We proceed with our simulation of a two machine system. In the previous lecture we kind of I gave you an idea how you can formulate the equations. We will actually go through the all the equations once and then go ahead and actually simulate. I will show you the results of the simulation for various disturbances like load change as well as faults. Now, this is lecture number 37 and what we will be doing here is of course, continuing with our simulation of a two machine system. So, let us just have a relook at what the system we were trying to simulate. This is the simulation system simulation and this is the initial steady state operating condition. Now, we will take this as the beginning or the starting point of the simulation. In fact, you can say this is the load flow situation and of course, the first step of any simulation is to back calculate initial condition. So, if I know the voltages here then I can get the values of for example, all the states and the field voltages of both generators based on the voltage at the terminals and the currents in steady state which are coming out. And of course, from the conditions from all the you know specifications which are given for this scenario you should be able to find out the voltage and the angles as well as the current output of the machine which will enable you as I said to compute the initial conditions. You can refer to our simulation of a synchronous machine with an AVR connected to an infinite bus. We did that several lectures ago where actually showed you how you can from the terminal conditions calculate all the initial conditions. So, let us look at the synchronous machine equations for the two machine system. I mean this includes both the machines and also how you will interface them.  So, when I say network transients neglected what I mean also is that stator transients also are neglected. When I say stator transients are neglected what I mean of course, is that d psi d by d t and d psi q by d t terms of the synchronous machine have been set to 0 and the corresponding differential equation has been converted to an algebraic equation. So, what we have essentially are the differential equations of the rotor windings g h f and k and we also have a differential equation corresponding to a simple static exciter plus AVR model. In the previous class I told you that the AVR plus static exciter is modeled just by a transfer function k a upon 1 plus s t a that is the form of the transfer function as a result of which it actually is embodying the differential equation in a state x c which is given here and of course, e f d the field voltage is equal to x c except when x c hits limits. If x c hits limits we kind of clip e f d to those limits. So, this is basically the static excitation system model this is the same for both the machines to keep things simple we have considered similar parameters for both the machines. The turbine governor model is also kind of a transfer function of course, you can write the state space equation corresponding to this transfer function that not that is something which I have not written here, but you can easily you know infer that this first order transfer function k 1 plus 2 s upon 1 plus 6 s is actually embodying a single differential equation. So, effectively you can write down this transfer function in state space form where the input is the error in the frequency or the deviation of the speed from the reference value and the mechanical power is of course, the set point the load set point P m 0 plus the output of this governor delta P m. So, P m of course, is limited and out here you see as in a static excitation plus AVR model the turbine governor model in fact, the governor model effectively has a gain k remember that the governor is a proportional type controller in this case. So, what we are considering is proportional type controllers in both synchronous machines. So, the turbine governor model the steady state gain is not infinity like an integral controller it has got a finite steady state gain. The mechanical equations of course, are the rate of change of the rotor position that is if theta is of course, the rotor position. So, if theta is equal to omega t plus delta then d delta by d t of course, is given by omega minus omega naught and the rate of change of speed is of course, the torque equation and in per unit of course, T m and P m are practically the same the assumption of course, is whatever transients we are going to study the speed deviation from the nominal will not be too much. So, mechanical torque in per unit is the same as is practically the same as the mechanical power in per unit. Now, if you look at the next equation rather a few more clarifications here remember that omega b in all what have written is the base angular speed omega naught is basically such that theta is equal to omega naught T plus delta is the rotor position. So, delta is equal to theta minus omega naught t in this study let us take omega naught to be equal to omega b. So, what basically we are saying is that the base frequency and omega naught are taken to be the same in fact, another the thing we will assume in this example to keep things simpler is basically assume that the steady state frequency is nothing but, the base frequency. So, this is some simplifications which we are going to consider. We have the algebraic equation for both machines in fact, along the d axis and the q axis. The first algebraic equation is something of course, you know we derive the synchronous machine model. The second algebraic equation is actually got by assuming that d psi d by d t is equal to 0 and in that in this particular equation this term here should have been omega, but we have approximated it to be omega b. So, this particular algebraic equation has got constant coefficients into these variables psi q i d and v d. Similarly, on the q axis you have got this algebraic equation this of course, derived from the synchronous machine model and this algebraic equation is in fact, obtained by setting psi d psi d by d t and d psi rather d psi q by d t equal to 0. So, the same approximations apply here as well as here. So, we have got in fact, four differential equations per you know you have got four equations of the synchronous machine rotor windings and one differential equation for the static excitation plus AVR, one differential equation for the simplified governor model turbine governor model.  So, there are two machines there will be 12 states in fact, but the algebraic equations per machine are four. So, four algebraic equations per machine and I will state down here. Now, remember one thing what I have shown you so far is the synchronous machines in the park's reference frame. So, when you derive it for each machine you will be using the park's reference frame native to that synchronous machine. But if I use a transformation C k instead of C p where instead of using theta as the argument of the cosine and sine terms here I use omega naught t. Remember delta is missing here you know if it was omega t plus delta it would be theta corresponding to a synchronous machine. So, instead of having two different transformations for two different machines what I will do is use a common transformation whenever I am going to interface the variables corresponding to the two synchronous machines. So, what this will become clear in the moment. So, the ABC variables of course, are the same all what we are doing is changing using the transformation C k to what is known as the d q variables. So, if you look at how these transformations and the variables are related you get the equation as shown here.  So, this relationship is essentially a matrix relationship, but you can easily see that it essentially gives you can be compactly written by this complex relationship. Similarly, for machine 2 if I use you know C p 2 which uses the argument for the cosines and sin's as theta 2 is equal to omega naught t plus delta 2 will get basically the relationship between the capital or rather the upper case q and d variables as related to the local variables which use the local parks transformation. So, whenever I am going to what I will do is I will get the equations to the upper case q and d variables the lower case q and d variables are using a transformation which is native to that machine. The upper case d and q transformations for machine 1 as well as machine 2 both use C k which is independent of theta delta. So, whenever we are going to so f q 1 and f d 1 upper case are in fact variables which are obtained for common transformation.  So, the point is that if all the a b c variables are you transform using a common transformation C k then we can use k b a l and k c l that is Kirchhoff voltage and Kirchhoff current law while writing down when interfacing both machines. Now, the important thing is you do not have to transform all the differential equations to the upper case d q variables at all. What we need to do is whenever we are interfacing these variables whenever you are writing the algebraic constraints relating to these variables that time you should ensure that all the variables involved in that interface are obtained using a common transformation C k otherwise you will not be able to use the algebraic relationships which are obtained from Kirchhoff's voltage and current laws. So, that will become quite clear now if you look at the algebraic equations corresponding to both machines. What I have done is the algebraic the variables psi d lower case psi q lower case i d lower case and i q lower case have all been transformed the equations have been transformed the same relationship is there, but now I am using different variables I am writing the same relationship in terms of different variables. Now, the interesting thing is that if I write down these algebraic equations in terms of the upper case variables I will have to combine those equations in fact and you get this kind of form of the equations. Now, the interesting thing is that if you choose x d double dash and x q double dash to be equal what you find is that this capital D variables psi d is related to i d by simply x d double dash psi q is related to i q also by x d double dash. So, if you assume that this sub transient saliency is not there that is x d double dash and x q double dash are equal then an interesting thing which follows is that the algebraic equation corresponding to psi upper case d is related to i upper case d by a simple constant coefficient which is not dependent on delta. The other terms are all gathered out here and they are all states f 1 is a function of the states. So, this is a non-linear function of the states. So, the algebraic equations effectively have been rewritten in terms of the capital D q variables. Now, this of course, can be done for both the machines. So, when you are talking of machine 1 you will have of course, an additional subscript of 1 everywhere. So, of course, I have not done that, but remember that this has to be done for both machines. So, what you will have effectively is that these 4 algebraic equations for each machine for both machines will be 4 algebraic equations, but remember that the variables in these 4 algebraic equations will be having a common transformation from the ABC variables. So, you can actually use these upper case d and q variables directly whenever you are using any algebraic constraints like K v l or K c l. If I neglect of course, if I neglected the stator transient that is d psi d by d t are set to equal to 0 and d psi q by d t are set equal to 0 then there is no real logic in retaining the first transients associated with the network. Remember that the network is was already simplified you know we may got an lumped R L model from what was essentially a partial differential equation model. So, that is of course, a big jump I am a big models in simplification. Now, we go ahead and do another modeling simplification that is we neglect the network transients.  So, you can get them and subtract them they are kind of compatible. So, we can use the voltage on either side of course, is obtained from a common transformation. So, this equation is actually valid we could not have for example, written down here small or lower case d 1 and q 1 and lower case d 2 and q 2 that would be incorrect. So, remember that this change is there. So, what we have effectively done is obtained these algebraic equations of the network from the essentially from the differential equation of the lumped R L model of the interconnection. There are some more algebraic equations what we have done essentially is what is v d 1 and v q 1 since there is a resistive load. If you focus on this diagram which is here if this is a resistive load it is a unity power factor load, but I also additionally say that it is a you know kind of a resistive load. So, the voltage here is equal to the current into the resistance. If the resistance is R L 1 then you know the voltage and the current are simply related by an algebraic relationship. Now, so the what is the current flowing through this it is the current of the generator minus the current through the line. If I call this current through the line as I L in that case you will have v q 1 is equal to R L 1 into the difference of the generator current minus the line current. Now, this 1 and 2 actually are superfluous actually this should be just I L q this 1 is not necessary. So, this is a small error which you should correct v d 1 is equal to R L 1 into I d 1 minus I L d please remember to remove this 1 here it is not required there is only one line current. So, there is no need of this additional subscript 1 out here. Similarly, v q 2 is equal to R L 2 into the current through the resistance that is the generator current plus the interconnectional line current again please neglect this superscript 2 here which appears in this term I L q. So, just remove this superscript I am sorry. So, you can remove this subscript. So, you have got this these algebraic equation please remember to make these corrections. So, eventually you have got 16 states what are the 16 states. In fact, these are delta 1 omega 1 then the 4 rotor windings are the first machine then the state corresponding to the simplified AVR in exciter model and x g 1 is the state corresponding to a simplified turbine governor model. Similarly, you have got the same thing for the other machine. So, there will be a total of 16 states and the algebraic equations R 14 you could have counted all the algebraic equations 4 for each generator that will become 8 plus 6 equations which I just described some time back 2 of course, for the line and the 4 equations which I just mentioned some time back. Remember that the number of variables algebraic variables also are 14. So, it should be possible whenever you are writing a program to actually use you know you can solve the algebraic equations and write them in terms of the states. So, this is something you can do remember that at every point at every instant of your simulation on numerical integration remember that psi d 1, i d 1, psi q 2, psi q 1, i q 1 and so on are dependent on the states. So, if you recall that if you look at these equations here you see that eventually psi d this equation is dependent on the states. So, there is an overall dependence on the states just remember that there is an overall dependence on the states. Now, we begin our simulation remember all the assumptions we have been which we have made we have made lots and lots of them, but some of the important ones are that we are considering we are going to consider relatively slower phenomena we are not going to consider very fast. Basically we are going to study electromechanical transients and what we have of course, done is also assumed in some cases replaced omega by omega b. So, what the assumption is that you are not deviating too much from omega b. So, all our studies are for frequencies which are near the nominal frequency is it now let us get back to our case studies. So, I will just get you to that slide remember we have made the simple models of the AVR and turbine governor. So, this is something you can watch on your screen. So, once you have made the simplified models and obtain the differential equations and of course, made a few more assumptions will you of course, considering three phase balanced disturbances there would not be any unbalanced disturbances synchronous machine data. And I have done the programming for analyzing the system the first result which I want to put forth to you are the Eigen values of the system for obtained after a small signal analysis around the equilibrium point corresponding to this situation. So, if you look at the situation again this is the equilibrium situation I have back calculated the condition linearized the differential equations we have done this before. So, I am not doing it again and I have actually tried to obtain the Eigen values of the system for this equilibrium point. So, if I give small disturbances the behavior will be captured by the linearized kind of response of the system for small disturbances. So, if you look at the Eigen values of the system there is some interesting things you will see if you have no governor if you have got no governor there are two zero Eigen values then you have got you will have two zero Eigen values and then you have got a low frequency oscillatory mode which is not so well damped. So, this is a low frequency oscillatory mode which is not so well damped I am sorry you also have other Eigen values some with relatively large real part and some very large Eigen values on the right hand side. So, without governor if I consider network and stator transients that is I do not neglect d psi d by d t d psi q by d t as well as d i d and d i q by d t of the network in that case you will have some very high frequency or high magnitude Eigen values corresponding to fast transients. So, this is what you get what are these two zero Eigen values remember I had mentioned to you that whenever you have got a system like this this is an analogy a two mass spring system you the thing is that if you have got essentially a swing mode which is an oscillatory mode as well as two zero Eigen values why do you get these two zero Eigen values you have got essentially if there is no friction of the surface then your response has two components corresponding to the zero Eigen values they are repeated Eigen values and in this case in fact you can show that you are going to get for the spring mass system response terms e raise to zero t and t e raise to zero t we have discussed this long time back when we are considering linearized analysis when you have got repeated Eigen values you can in some cases get this kind of response. In fact if you do not have friction we do get two zero Eigen values two for a two mass spring system this something you can verify by writing down the equations. So, what is this mean is that if I give if for example these two masses have equal initial velocities say v zero is equal to one and v v two zero is equal to one both these masses will move if there is no friction they will keep on moving getting what I am trying to say. So, they will keep on moving in case there is no friction. So, what you will find is that the displacement from an arbitrary reference will have a variation of t because if they given initial condition in these states which are equal you will find that this just keeps on moving. So, it is not surprising that you have got these two zero Eigen values and therefore, you have got this kind of response. So, remember that when you do not have a governor what does it mean?  So, it is equivalent to having the situation where you have got constant external forces acting on this mass spring system, but no friction there is no frequency dependence of these external forces. So, if there was friction of course things would be different in fact by putting a governor what you are doing is essentially making some external force on this system which is proportional to the change in velocity. So, in fact a governor changes the mechanical power with in response to omega minus omega omega f minus omega what it means essentially is that you are introducing a kind of a viscous damping coefficient into your torque equation and as a result of which when you have a governor you do not have these two zero Eigen values. So, that is an interesting point. So, just remember this remember that in case you have got a load which is frequency dependent or you have got a turbine governor enabled you will get only one zero Eigen value because in that case you do not expect this t e raise to zero t term to be there. In fact if in case you have friction and you have got an initial velocity you will find that eventually this mass will grind to some halt grind to a halt after some time. So, you cannot have this kind of term in case there is this viscous damping introduced by either load dependence on frequency or mechanical power dependence on frequency which is introduced by a governor. So, in this case of course our load is a constant resistance. So, of course you do not expect that the load to be frequency dependent. So, if you do not have a governor you will have two zero Eigen values and t e zero t kind of response. Remember of course that even if you put a governor there is still be a zero Eigen value or in effect a response term which is equal to e raise to zero t why is that. So, remember that if in this mass spring system if my response is x 1 t if your response is x 1 t and x 2 t you can add an arbitrary constant term to both of them and still your differential equations will be satisfied. So, an interesting point is that if your solution to your delta 1 and delta 2 or in this case for a spring mass system the displacements x 1 and x 2 is x 1 t then x 1 t plus x 0 also will satisfy your differential equation. This is because whenever x 1 and x 2 appear in your differential equations or even in this synchronous machine example you will find that everything depends on the difference of the angles the absolute value of delta 1 and delta 2 does not determine the electrical powers etcetera. None of the components in this system are dependent solely on the absolute or the actual angle at phase angle at a given point. For example, the power flow the steady state power flow here depends on the difference of the angles at the two ends it does not depend for example, on this alone. So, what it follows is that if your delta 1 and delta 2 are solutions are the responses following a disturbance or even the steady state responses.  Therefore, do not be surprised when you do an Eigen value analysis and find out that you are getting a zero Eigen value whenever you are studying this kind of system with the kind of differential equation and differential algebraic formulation which we have written. So, of course, whenever you do an Eigen analysis also another thing you try to remember is that you may not get this is exactly zero whenever you do a numerical analysis. You may get this slightly non zero but that will be because of numerical errors precision errors. So, of course, when you have a governor now coming back to this problem having a governor introduces changes this zero Eigen value to a negative real Eigen value which implies that they cannot be any t e raise to zero t kind of terms in your response. Another thing is that two additional Eigen values come about because there are two extra states which we have considered with when you model a turbine governor. If you assume of course, assume that the mechanical power is constant that is what this without governor means you will not have these additional two Eigen values but when you have a governor you will have these additional Eigen values. Again remember that when we consider network transients we have got these high frequency terms. If you neglect network transients in that case you will find of course, that the high frequency terms are missing but other than that you have got again these zero Eigen values. You also have the low frequency oscillation terms these are also called a swing modes and you have also got additional modes because of their many many more states. But the important modes which you need to remember are these zero Eigen values and these swing modes these are associated with electromechanical transients. Remember of course, then how do I know that I cannot I have just stated this fact I am not proved that these Eigen values are associated with the electromechanical variables deltas and omegas. But in fact, you can actually prove this using participation analysis which we discussed sometime back. You can associate the modes with electromechanical transients primarily with the electromechanical transients but of course, this does not mean that these modes are not dependent on the other states. But when I say electromechanical modes these are essentially primarily associated with deltas and omegas. The other states also influence these modes but they are primarily associated with delta and omega that is what I want to say. So, with governor and without governor you have similar behavior with and without network transients considered you still have a similar behavior. So, we can to some extent justify this approximation of neglecting stator and network transients. So, we go to case 1 now I will quickly go through a few simple disturbances. Suppose, I have got this I give a step change in this load I change this resistance from 0.52 per unit to 0.7 per unit. So, actually the load reduces because the resistance has reduced sorry resistance has increased. So, if there is a load throw off that some part of this load has been removed. In that case if I do not have governors if I look at various quantities first thing you will find is the rotor angular difference increases or rather decreases why does it decrease from 45 degrees it comes to roughly 40 degrees. So, the angular difference delta 1 minus delta 2 both are you know you know rotating and the angular difference between them is around 40 degrees after the disturbance while it was 45 degrees before the disturbance why does that happen well one way of looking at it is that when you throw off some load here the load here reduces on this line reduces. So, the angular difference between these 2 buses reduces and the corresponding rotor angle also reduces. Now, remember when you say no governor you are not changing the mechanical power. So, if I do not change the mechanical power remember this is like a friction less system. In fact, there is no dependence of the external powers mechanical or load powers on the frequency and if there is a load generation mismatch what you of course find is omega 1 omega 2 as well as the center of inertia frequency which is defined as h 1 omega 1 plus h 2 omega 2 divided by h 1 plus h 2 both linearly increase. So, you see this linear increase and of course, if you allow this to continue then after a point your generators will be tripped out the reason is that if your frequency goes greatly away from the nominal frequency there is a chance that you will damage the turbine and generator system why is that. So, actually turns out that the turbine is made out of blades they are made out of blades and you have got a steam flow through this through these blades along this periphery the steam flow is not uniform it is not perfectly uniform there are variation natural variation in the steam flow. So, your steam flow may be 0 to 360 may be like this. So, it may be of course, this is an exaggerated electrical engineering or electrical engineers description of what happens. Now, what happens is that in case your rotational frequency deviates from nominal if it deviates from nominal you will find that this turbine blades start getting periodic forces across means are applied across the blades. So, if your steam flow is changing there is a variation of steam flow and you are running at the base speed you will of course, see that the force on the blades is actually changing. Now, the thing is if you deviate from this omega b the frequency of the force which these blades see will change. Now, what happens is in case the frequency with of the forces which these blades see starts coinciding with the natural vibration of these blades then there will be a huge displacements see you are giving a periodic force which is equal to the natural vibration frequency of the blades if that happens at a certain frequency if the rotational frequency deviates from omega b then you will find that the frequency of the forces on the blades also changes and if it coincides with the natural frequency of vibration the blades will get damaged. So, nobody allows especially a steam turbine in a steam turbine generator system nobody allows you to deviate the frequency to deviate much away from the nominal speed because typically you will find that after around a 1 hertz deviation from the nominal 1 or 1 and half hertz from the nominal you may start coinciding with the resonant frequency the forces which are incident on these blades start coincide the frequency of that starts coinciding with the natural frequency of the blades. So, that may damage the blades. So, no after a certain speed deviation either on the positive direction or the negative direction you may have to trip out the generator you either have an over speeding control which suddenly changes the mechanical power like a governor or you have to trip out the generator. So, this is not acceptable of course, remember that because the angular speeds are changing does not mean that the machines are losing synchronism. So, if you look at the difference frequencies it is constant in fact omega 1 minus omega 2 is constant only thing is that center of inertia speed is increasing because unbalanced external force because you have changed the load generation balance also the line power which is line power comes to a constant. So, actually from a point of view of synchronism synchronism is if you look at it we are not gone out of we have not gone out of step the mechanical powers are constant the center of inertia frequency is changing, but the relative speeds are in fact constant. So, we are not lost synchronism we have what we are saying is that the overall frequency has changed. So, that is something you have to keep in mind we are not talking of a relative motion instability we are talking of continuous change in the center of inertia speed. So, both machines are almost together decelerating or in this case they accelerating together they are not they are moving together, but they are both accelerating. If you look at a case two with the governors are enabled what you notice is of course, the mechanical the transient looks a bit different and in fact it settles down to a different value you look at the angular difference it settles down to 32 degrees instead of 40 degrees in the previous case. The angular speeds reach an equilibrium there is a decrease in this there is an increase in the center of inertia speed as well as the speed of each individual mass rotor mass, but eventually the speed reaches an equilibrium. The equilibrium speed is not equal to the previous speed. In fact, if you note something that the governors are proportional type governors in the sense that the mechanical power is changed using an algorithm like this the governor has got this kind of you know transfer function and of course, the turbine has got a transfer function. So, the turbine governor transfer function is k 1 plus 2 s upon 1 plus 6 s. Now, this k is a proportional controller effectively it is also the inverse of the droop characteristic of the machine. Now, the point is that you can change the mechanical output of the machine only if omega f and omega are not equal. So, in case this proportional kind of governor will always give you a steady state error. So, your frequency does not come back to the original frequency there is a frequency change that is something which you should remember. The mechanical speeds the difference speeds a relative motion is stable it is not unstable. The speeds the difference speeds become equal to 0, but the overall speed of both the machines settles down to a higher value. Here the mechanical power are changing why are they changing because we are having a governor. So, if you have got a governor your mechanical power will change and of course, the line powers also will change because governor is present here as well as here. So, the point is that if governors are present on both machines each of them will change the mechanical power. If they change the mechanical power the overall power flow situation changes. So, load has changed mechanical power here is change and the mechanical power here is change. So, if all the three things change you will find the frequency goes to a new equilibrium and you know your line power also settles to a different value the angular difference between the two buses also will settle down to different values. Now, of course, the point which you should note here is that governors on both machines are present. Now, what if we had just one governor or a governor present only on one machine basically your mechanical power of only one machine would change only one machine would take on the load change and of course, if you just had governor on one machine only one person would contribute to the you know to trying to get the frequency to equilibrium. So, if you keep the same gain and just disable one governor your frequency deviation will be more only one generator will respond to the load changes. It can also be inferred that since the load the amount of power change of each turbine is proportional to k into omega r f minus omega by changing k or omega r f you can in fact, change the amount of contribution of each generator. So, why is that so because remember that the speed eventually if you are remaining in synchronism speed of both machines is going to be the same. Now, if speed is the same and omega r f of both machines is the same then the amount of power change each generator takes up is proportional to omega r f minus omega into k. So, if k 1 and k 2 are different I mean you have got two different gains or two different groups on the generators of each machine in that case you will find that the each generator takes on different load change a kind of extreme condition is where the gain of one generator of one governor is much higher like one of the governors for example, has a steady state gain of 300 and the other has got a gain of 10. In that case the governor assuming omega r f's are the same the governor with a larger gain takes on more of the load it takes it increases its mechanical power more whereas, the other generator does not increase its mechanical power as much. Now, the extreme condition is where you have got an integral controller on one of the governors and integral controller essentially has got infinite gain in steady state you know 1 upon s remember. So, you will get infinite gain in steady state. So, if you got one governor which has got an integral gain it will take on the complete load change and the other governor will be left high and dry in the sense it will not contribute anything to trying to maintain frequency of course, this is assuming omega r f on both machines is the same. Now, just think of think about it can you have integral controllers on both governors this is something you need to think about this is a question which not obvious you think over it a bit you cannot have in fact both governors having integral gain why it is. So, is something you can think about now the third case is not a load change what we will do is we will have a three phase fault it is a balance fault at bus 1 at 1 second and we will clear the fault and after 80 milliseconds that is four cycles. Now, of course, remember that post fault conditions assume to be same as pre fault conditions. So, it is a kind of temporary fault it is we just come back. So, when the fault is cleared. So, you can consider this as a situation where in bus 1 suppose you have got an open line this is your oops bus this is a generator 2 is a generator 1 the same system this is a load this is a load. So, this is your same system and you have got a transmission line out here which is open circuited here at this end. So, short transmission line and you have got of three phase fault on this line near about this bus. In that case you will have a short circuited this bus a three phase short circuited this bus which has to be cleared by opening the line. The post fault and the pre fault situation is going to be the same when before the fault you had connected an open line here it is a short open line. So, it is like having nothing here you had a fault for some time which is cleared by opening the line. So, what you have is pre fault and pre post fault situation is the same assuming of course this is a short line and open circuited short line is effectively doing nothing to the system initially. So, under these circumstances what you find is if you are clearing time is this much you will find that delta 1 minus delta 2 in fact is stable. Since pre fault and post fault systems are equal you will find that there is no change in the load generation balance situation nor are the flows change. So, losses also do not change. So, angular speed simply comes back to the original value they are transients, but overall angular speed settles down.  The powers again are stable actually this simulation has been done considering network transients we have model network transients. So, what you see essentially in the beginning of this transient here for example, are some high frequency components. So, if you consider network transients you will get these high frequency components there is a high frequency component here as well. So, this is how your delta 1 minus delta 2 if you neglect the network transients you get almost similar response, but remember there is some there are some differences for example, the maximum deviation here is around 70 degrees whereas, when network transients were considered it was almost 60 degrees. So, there is a 10 degree difference. So, when network transients are neglected you do have some difference in the result. In fact, network transients neglected gives you a somewhat larger angular deviation and, but otherwise the response looks almost the same you just see that there is no high frequency you know transient you know because you have neglected network transients. Now, we will consider when we increase the fault clearing time to 0.28 seconds, but the network transients of course, are neglected the interesting thing is that the angular deviation under this circumstance grows in an unbounded fashion. So, if you have a larger clearing time the fault is cleared, but after a long clearing time. So, a longer clearing time means that because of this sudden disturbance the deviation of the states from the post fault equilibria are going to be more. So, if your deviation is too much you may not you know pull back into synchronism as a result of which the relative angular motion is becomes unstable. So, please remember this is relative angular motion becoming unstable if you look at the angular speeds they too you know deviate from each other although omega c o i is relatively you know within bounds omega 1 and omega 2 the relative angles increase. This is contrast this with the earlier situation in the earlier situation when we had a load through off without governors omega c o i went on increasing, but the relative motion between them was stable this is exactly the converse situation. So, what we have seen is that if you give a disturbance like a fault which is not cleared for a long time you may go out of synchronism and you will see the relative motion is unstable. So, relative out of synchronism refers to relative motion. If you look at the mechanical the electrical power output of each machine you will find that it is oscillating there is a kind of a wild oscillations. In fact, it even reaches negative values positive and negative values. So, if you lose synchronism this is what your mechanical power is going to look like. So, if your mechanical power is of course going to look like this you cannot continue operating in this fashion. So, although I was kind of shown you a simulation which in which the loss of synchronism kind of remains for several seconds no action is taken you are just allowing the angles to you know increase. Another word for it is the poles of both machines are slipping with respect to each other. So, you just allowing that to continue if you allow it to continue there will be wild oscillations in power and you cannot operate in this fashion you will damage the shaft for example of the machine. So, what usually you do is that in case you detect an out of synchronism condition you will have to separate out the two machines. Now, if you separate out the two machines you will have to essentially trip the interconnection between them. But remember if I trip the interconnection between them I will have basically another problem to contend with what is that the local load generation balance in these two islands which have got which have kind of disconnected is not you know there is a fairly large generation imbalance in both these islands and you know then you have to really exert the governors as well as any emergency load shedding schemes may be required to quickly get an equilibrium in the center of inertia of each individual system or you know now they are disconnected systems. So, I have to ensure that the frequency of each system reaches an equilibrium. So, you have to really control the prime over and load power on both systems once you disconnect.  So, you cannot operate that way you have to trip out the interconnection once you trip out the interconnection you are left with another problem that is of load generation imbalance in the two disconnected islands which has to be really sorted out. So, loss of synchronism is not a nice scenario and even if you manage to island or trip out or disconnect the two systems when they are lost synchronism why do you do you need to disconnect because there is going to be wild oscillations in power voltage and so on. So, you have to disconnect once you disconnect you have got the problem of maintaining the frequency in the two individual systems which boils down to trying to maintain the load generation imbalance balance in these two systems. Now of course, an interesting point is that if your power system experiences a loss of synchronism situation usually there are out of step relays which detect this and trip also an interesting point is that the wild deviations in voltage and current cause distance relays in a transmission system to mistake it for a fault and it causes transmission line tripping. So, whenever there is a loss of synchronism scenario you may have you know what you call an uncontrolled splitting of the system due to distance relay operations. So, you may what I said that you need to disconnect the two machines they may disconnect on their own in the sense that relays may actually trigger and trip out in case such a situation occurs. So, there will kind of summarize this very interesting study which we did on electromechanical transients in a two machine system. Just remember of course, that we have considered the electromechanical both the relative frequency relative motion as well as the center of inertia motion. There are other modes and patterns in this motion they are not very well observable in this response. Those patterns also can go unstable for example, if you do not design your control system properly for some inappropriate gain of AVR and govern you may find some other modes which are not necessarily electromechanical modes also go unstable. So, these kind of things also can occur will summarize at least this electromechanical transients part in the beginning of the next lecture and then move on to some understanding what happens when you have more than two machines like our grid which has more than 500 or so large machines synchronous machines all interconnected to each other. So, this something we will discuss in the next lecture.


Welcome folks, we at the Dow Industries finish up $643, Nasdaq up $270, S&Ps up $89, Gold. Gold contract down $8, trade at $18.32 an ounce. We had Silver up $3 cents, $21.71 an ounce, LightSweet crude up a buck, $110.65 a barrel and notes and bonds. The 10-year note, down 11 ticks, trade in $1.1526, the 30-year up down a full point, plus 4 ticks at $133.18, we have the 10-year right now yielding 3.30% folks. The high, the last few weeks there's a 3.473, the low for the last three months is 2.2. Now just check that out, in three months you went up 50%, 2.2 to 3.4. We bring this back six months if you want to see something wild, we've gone from 1.4 to 3.4. We've added two points on, and I believe that would be, oh man a year, no, oh my God. It's 1.1 to 3.4, the low for the last 12 months folks is 1.1. Now let's get over to this dollar. So the dollar's going to be, the dollar right now, the market has a love-hate affair with the dollar. The bottom line is that you can see, you know the bottom line is that the first high the dollar made was in May, that high was 105. We go back and we look at the aspect actually of where, let's take this and look at this for a second, because what you're going to see is that we go back to November, well let's see, November the dollar was trading at 94, bounced along the bottom, as it bounced along the bottom, you know, market hung up, start in January, guess what? 89 the dollar was in January, bottom line, markets break and as they break the dollar goes from 89 all the way up to 105. So if this dollar is going to break higher and go to 121, you can see it's a direct correlation now, and there's not always a direct correlation by the way, okay, but the bottom line is that there's certainly a direct correlation now that when the dollar pulls back, the market gets some relief, the dollar goes higher, the market gets slammed, bottom line, keep your eye on the dollar. Have a great night folks, have a safe night, come back and visit Tommy tomorrow morning, kicks us off 9 o'clock in the morning, great show folks, have a great one, have a safe one.


Welcome to this lecture number 3 which is in which I am going to continue from where I stopped in the previous lecture that is on ground water level fluctuations and environmental influence and here we know that it should be our endeavor to maintain the ground water level which may be water table in case of an unconfined aquifer or it is known as the piezometric surface in case of a confined aquifer. So this ground water level should be maintained at the optimum range. It should neither be too shallow nor should it be too deep and to maintain this optimum level of ground water during all the times. So we need to study the reasons based on which the ground water level fluctuates. So some of the reasons are listed here. The first one is stream flow variations followed by meteorological and tidal phenomena and urbanization is also one of the parameter which influences the ground water level fluctuation followed by earthquakes, external loads and so here land subsidence. Here let me also write land subsidence etc. So these are some of the reasons or causes for the ground water level fluctuation and let me also continue. So in the previous class we are discussing about the secular as well as seasonal variations. While the secular variations represent the variation in the ground water level over a period of more than a year, seasonal variations they represent the variation in the ground water level within one year over different seasons and there is also third type of variation which can list it as the short term variation. So in this case so it is basically daily or diurnal variations which is very commonly observed in municipal water supply wells. So essentially here you can say this short term variation is a daily represents daily or diurnal variation, seasonal variation represents the average annual variation, average variation within an year and secular variation represents the variation in the ground water level over a period more than a year. So we need to consider all the three and during the all the periods right from period ranging from less than a day to a period which is say around a year to a period which is greater than that may be a number of years could be 5 or 8 or 10. So all these things we need to consider. Now let us consider firstly the stream flow and its impact on the ground water levels. So let us consider in this figure a stream with bed shown along the sloping bed shown here and then there is an impermeable strata let this impermeable strata consist of a hump as shown here in the middle and because of this hump in the impermeable strata. So the water streamlines the ground water streamlines will show an upward trend and especially in the hump so where the height of the impermeable strata is at its highest. So the sum of the stream the ground water streamlines they will be above the ground so they become surface water streamlines and so in this portion so that is say from here to here. So this water table will be above the ground level whereas to the left of this the water table is below the ground as well as to the right of this section the water table is below the ground level or in this case it is a stream bed level. So here what happens is so this portion that means from the hump to the portion where the ground water streamlines have transformed themselves into surface water streamlines. So it will be acting like a effluent stream or a gaining stream because here what happens is so the all the ground water will contribute as effluent or as will contribute to the stream flow.  So therefore from this point onwards downstream the water table is again below the ground level and this portion between the hump and the location where the surface streamlines again get converted into ground water streamlines. So that will behave like a losing stream or an influent stream so in this case what happens is because of the water table higher than the water table in the adjacent as one so the stream will lose so through infiltration as well as the through infiltration occurring at the bed as well as the banks so therefore it will be acting like a losing stream or an influent stream. And in this in the middle portion so it is the rising water in a stream channel from the emerging ground water flow so this is how the stream flow will affect the ground water level. So many times this stream flow the effect of the stream flow on the ground water level is also visible especially in case of floods the flood wave. Let us consider in this case a flood stage hydrograph which represents a variation of stage which is essentially the water level in the stream at a particular location with respect to a standardized datum such as the mean sea level and its variation with time. And in this case the time values are represented in terms of flood periods so flood period is the period basically it starts from the duration from the time instant when the stream flow or the discharge goes on increasing abruptly above the base flow which is basically the ground water contribution. And then again after reaching the peak flood during which time there will be peak stage so this is the peak stage here again it starts the flood wave starts receding so the flood level as well as the flood discharge gets reducing. And finally it reaches the normal level so this period from the increase from the time instant when the flood wave started increasing to the time instant when the flood wave started decreasing so this is known as flood period. So here it is indicated as the time instant between 0 and 1 so here this is the flood stage hydrograph and the difference between the initial water level which is here in Indian terminology it is known as the no flood level or the danger level and also the highest flood level that is the final water level that is the water level during the flood peak. And this one this initial stage of flood is also the final stage because after the flood wave recedes it again goes back to this one and here this is the ground surface which is slightly above the flood stage flood peak stage. And in this case now let us consider how the bank storage volume as well as the recharge and discharge vary in case of a flooding stream and so now let us consider the bank storage. So essentially this bank storage volume is the volume of flood water which gets stored in the banks of course which includes beds also. And here what happens is so this as the flood stage goes on increasing from the initial level to the flood peak stage. So the bank storage volume also goes on increasing and when the flood stage is at its peak the bank storage volume is also at its peak and as the floods stage goes on decreasing the bank storage goes on also goes on decreasing but more gradually not as abruptly as the flood wave. So here in this case if the time for the receding flood stage hydrograph is may be of the order of say 40 to 50 percent of the flood period whereas in this case the time for the reduction in the bank storage volume it may be almost say 2 and half at least 2 and half times the flood period. So it is more gradual here. And now let us consider the recharge and discharge volume which occur due to the water entering the bank storage and the water leaving the bank storage. So here initially when the flood wave starts and the flood stage goes on increasing from the initial level to the flood peak stage so the recharge goes on increasing and it reaches the maximum and again so this recharge then the recharge goes on decreasing and at this time instant when the flood stage is at its peak and the bank storage volume is also at its peak. So here so the recharge volume which essentially is represented by the volume bound by this curve so this recharge volume is also the maximum. So here this is the peak recharge intensity and this recharge intensity goes on decreasing and then the recharge volume so this is the area here so that is maximum. And once the recharge is maximum then what happens is the water starts leaving the bank storage and so that will appear as a discharge. So this discharge which starts from the time instant of the flood peak stage it starts increasing initially reaches peak somewhere between the flood peak stage and the first time flood time period. So somewhere in between so this the discharge volume is this the discharge intensity is maximum and then so like the bank storage volume so then onwards so the water leaving the bank storage will also be gradual. So essentially this area which goes on increasing represents the that is the water leaving the bank storage and again so in about 2 and half to 3 times as 1 so it shows the it again comes back to its original value. So this is the impact of stream flow so previously in the previous case we studied the we discussed about the ground water level in case of a river which is having an impermeable bed with a central raised portion or a hump and in this case number 2 we studied the variation of the flood volume especially the bank storage volume as well as the water entering the bank storage during the recharge process and water leaving the bank storage during the discharge process. So these are some of the cases of stream flow influencing the ground water level. Now let us come to what is known as the base flow and this base flow as a name itself says so it is the flow which is existing in a stream due to an extended contribution of ground water. So obviously the stream flow it originates from the ground water flow so that this base flow is a stream flow portion which originates from the ground water flow. Now let us consider a flood hydrograph as I was mentioning here so this is the total hydrograph which we can also call it a flood hydrograph say somewhere here this during this period there is a precipitation or rainfall then because of that so there is surface runoff increase and then it starts the flood hydrograph and it reaches the peak. So this is the peak discharge or the peak flood discharge and after that it goes on decreasing and again it will reach the total discharge will be equal to the base flow wherein entirely it is the base flow which contributes to the total flow from this time and beyond. Then now here let us study the variation of the base flow as we discussed in the previous case so because during this period recharge is taking place the ground water recharge is taking place and unless the ground water gets saturated so there cannot be any discharge. So therefore this is essentially the dotted line from here to here this represents the recharge phase and then there is no this one and if we from this point onwards the discharge starts so this discharge it goes on increasing reaches a peak and then it starts decreasing and so finally it starts gradually decreasing and it reaches from this point onwards it is only the base flow which is contributing this to the stream flow there is no other contribution to the stream flow beyond this point. But if we consider the if we neglect the bank storage then what happens is so the base flow hydrograph which is essentially the plot of the base flow with time it shows less fluctuation so because so here what happens is so this base flow hydrograph in this we are neglecting the bank storage and because of this one so it is showing the minimum base flow does not reach 0 because there will be always some but this is not the actual case so this is just the base flow hydrograph when we neglect the bank storage. So here the minimum base flow is also less is also slightly more than the 0 which is the actual minimum base flow and the maximum base flow is slightly less than the actual maximum base flow which occurs somewhere here so like this so it is the base flow which essentially is the one which provides the this one that is which provides the extended ground water distribution over space and time and it is essentially this base flow in the in hydrology it is represented by the various infiltration indices like the phi index the w index so which represent essentially the infiltration part and then so especially this w index the initially abstraction also so essentially so the base flow represents the minimum total flow which exist during the period wherein there is no flood flooding. Now so this represents the base flow variation during a flood hydrograph the actual variation shown by the dotted line and the base flow hydrograph neglecting the bank storage shown by this line which shows a higher minimum and a lower maximum. Now let us consider the other factors such as the impact of evapotranspiration on the ground water fluctuation so in the previous class we mentioned that even though ground water it is below the ground so always there is some small portion of ground water which is closer to the surface which is very close to the surface level and it is affected it is subjected to evaporation and so therefore what happens is so because of this small that is the portion of this ground flow which is directly subjected to evaporation near the surface so there in the surface near the surface so the evaporation expressed as a percentage of pan evaporation is very high as you can see here so this is say some in the range between say the surface and say 0.5 meters or say maybe 1.45 meter which is one and half feet so around this range in this top layer so the ground water evaporation which will be almost 25 to it is more than 25% and even it reaches as high as say 50% of the pan evaporation rate there but as you go deeper and deeper so this the evaporation effect it will be less and less visible on the ground water fluctuation because so what happens is so this is the ground water is at a depth below this 0.5 or say 0.45 meters and therefore what happens is the ground water evaporation of ground water expressed as a percentage of pan evaporation it goes on decreasing and even it may be so at deeper depths it may be practically negligible it may be of the order of say 5% or even less than that so this is how the ground water fluctuates due to the effect of evaporation so the effect is significant in the ground water layer which is at the top that means from the surface to say 0.45 to 0.5 meter below the ground and below that the fluctuation of ground water level due to evaporation so that will be significantly less. Now let us also consider the effect of transpiration because as you know evapotranspiration consists of evaporation which is occurring at the open surface or the open water bodies or the bare soil the soil moisture gets evaporated there and the transpiration is basically the water which gets which transforms into the vapor form due to the metabolic activity of the plants so the plants they during the process of metabolism so through this stomata openings so they give out water in the form of water vapor which is known as transpiration and here say let us consider a day in few days in summer and the depth of water table and as you can see here so this day 1 represents a 24 hour period similarly day 2, day 3, day 4 all of them represent 24 hour period and as we all know so the temperature is maximum sometime immediately after the midday so therefore during that period the transpiration rate will also be maximum so therefore the depth of water table will be the highest that means the water table will be the deepest at that and again as the evening approaches and then as the at the midnight and then so beyond that so what happens is so due to the reduction in the transpiration activity so the depth of water table it shows a slight increase so this may be of the order say few centimeters may be something like less than definitely less than 10 centimeters generally of the order of say around 5 centimeters then again the next day it happens the same thing what happens is so here somewhere immediately after the midday the transpiration is a maximum the rate of transpiration is a maximum so the water table depth is minimum so this kind of daily variation of the water table depth due to transpiration it follows a you can say this is a sinusoidal wave now let us consider the effect of the vegetation evapotranspiration essentially because it is extremely difficult to measure evaporation or transpiration separately because when we plant when plants grow on the ground so there are some areas where there are plants which are planted artificially or plants which grow out naturally whereas in the neighboring areas so there may not be any plants so essentially so in such case so there will be loss of water from evaporation in the bare soil or the soil or the area where water is the plants are watered by say flooding and other similar processes so here what happens is so therefore it is a well known practice to express this total loss due to evaporation in transpiration together as evapotranspiration so here see in case of a bare soil so the evapotranspiration is the depth to water table the plot of say depth to water table versus evapotranspiration it follows this curve so therefore so at this one so at this depth so there is zero evapotranspiration so this could be say a few meters may be 2 or 3 2 to 5 meters also depending upon the type of soil and the presence of the impervious strata below and on the other hand say wherever there is a shallow rooted vegetation so these consist of plants whose roots they do not spread say more than say 1 meter from the ground surface so in such case what happens is so the at the ground surface the evapotranspiration is the maximum and then as we go deeper and obviously this depth the depth where in the evapotranspiration will be practically 0 so this depth will be higher than the depth due to the depth observed in case of a bare soil so here so the variation of evapotranspiration and the depth to water table in areas having shallow rooted plants or crops or vegetation it follows this one obviously here this the and here as you can say this is a bare soil so this evapotranspiration is entirely due to evaporation whereas in this case so if you can say this is due to evaporation and this is due to transpiration so and at this depth which may be say something like say 1 to 2 meters so here so the at this depth and beyond so the evapotranspiration becomes practically 0 and now let us consider deep rooted vegetation like such as the large trees so for example I can give this banyan tree so this banyan tree that is one of the where in the roots so they also grow and they also reach the ground then they grow bigger and bigger and thereby giving additional stability to the banyan tree and in this case the roots may go even few meters deep also maybe sometimes even maybe tens of meters deep rarely so here what happens is this the plot of evapotranspiration and the depth to the water table so it will follow a curve which is even which is having a at the ground level the evapotranspiration is even more because it is a deep rooted vegetation and the when it is deep rooted vegetation it also has a large number of leaves as well as stem through which this transpiration takes place so therefore the evapotranspiration at the ground level is larger and also so up to this the this is basically the it represents the root zone depth which may be of the order of say few meters say 5 to 10 meters so only beyond that the evapotranspiration becomes 0 so therefore so this is the this diagram shows the variation of evapotranspiration with the depth to ground with the depth to water table for bare soil shallow rooted vegetation so where in we can say the vegetation is the root zone depth is say less below less than 1 meter or so less than 1 meter whereas deep rooted vegetation where in the root zone depth is even up to say 8 to 10 meters or so so in this case so this is the variation so now let us come to the variation or the fluctuations in the ground water table due to other meteorological phenomena such as the atmospheric pressure and we know that so it is the atmospheric pressure which is the prerequisite for a low atmospheric pressure is a prerequisite for precipitation when there are wherever there is a low pressure formation so there what happens is the water the atmospheric moisture which is as well as the moisture which is in the clouds it has a tendency to precipitate and this precipitated the clouds with water atmospheric moisture condense in them becomes heavy and then there the precipitation starts in various forms of precipitation so here what happens is so the as the atmospheric pressure decreases so here so the these peaks because the atmospheric pressure it is shown to be in the graduation it is the higher atmospheric pressure is shown in the downward direction so therefore this as the atmospheric pressure increases so there is no possibility of precipitation so therefore the ground water the well water level which essentially represents the ground water in unconfined aquifer it will be at its lowest level and as the atmospheric pressure decreases so it represents so these points so here so the there is a possibility of precipitation and then due to precipitation the well water level which represents which also represents the ground water level in an unconfined aquifer increases so like that so this is the effect of atmospheric pressure on the ground water fluctuation in case in this case we have considered only the unconfined aquifer. Now let us come to the the effect of precipitation in general and say rainfall in particular on the ground water level fluctuation so here let us consider the weakly hytograph which represents the amount of precipitation which has taken place during that particular week so in this case this rectangle represents the precipitation depth in the week number one similarly this represents the precipitation depth in week number two so like that so this is basically a stacked bar graph with the width of each of the stacked bars equal to the duration of one week and in this case now in the in red colour what the average water table elevation in the wells which represents the ground water level in an unconfined aquifer is represented in this case as you can see here so this is basically here we can say this is we can consider this to be the monsoon season in a region say in India where the monsoon is significant and this one so here what happens is as long as there is some amount of average weakly precipitation so this results and the average weakly evapotranspiration is somewhat less than this so this the ground water the average water table elevation will go on increasing and there are some places where the average water table elevation is almost stagnant so those they those represent the weeks wherein the total weakly precipitation as well as a totally total weakly evapotranspiration is more or less same or slightly less in that case it also shows like decreasing trend and in this case so here say this during week number 17 and 18 there is absolutely no precipitation so in this case the precipitation amount the weakly precipitation amount is 0 whereas the weakly evapotranspiration amount is significant so therefore it shows the water table shows a lowering trend so that is shown by this and then again on the 19th week so there is some precipitation and because of that the water table again and as long as this the depth of precipitation is slightly more than the average weakly evapotranspiration so this water table goes on shows a slight increase so like this the various meteorological phenomena will impact the ground water level fluctuation now let us consider the tidal range the effect of tides on the ground water level in this case we know that so then in English there is say that time and tide wait for none so these tides essentially are daily tides which occur with the time period of say 12 hours I am sorry 24 hours and 50 minutes there are also the spring tides and so in a duration of say 24 hour 50 minutes so point on earth will be closest to another similar point on moon so essentially these tides occur due to the attraction between the earth sun attraction earth sun earth moon as well as sun and moon so this obviously of course sun and moon it would not have any effect on the earth but at least the attraction between earth and sun as well as attraction between earth and moon it earth and moon so this attraction results in the daily tides so which will so in a period of say 24 hour 50 minutes there will be 2 spring tides there will be 2 high tides and there will be 2 low tides and then similarly during summer and then during winter spring as well as autumn there will be so tides so here let us consider so the tidal effect on the ground water level and in the left hand side in the figure we are considering a confined aquifer so here this is the ground water level so here although the ground slope will not be as steep like this generally so for simplicity so the interface between land and ocean is represented by this vertical line and so this represents a confined aquifer and here so this tidal range is represented at 2 H 0 where H 0 is the height of the water surface above the mean sea level at that particular tidal location or coastal location and then at a general distance x measured from the coast so this is the coast here which has been approximated as a vertical line so at a general distance x the tidal height is equal to 2 H so here what happens is because of the tidal effect so the when the water level in the sea is maximum so obviously the ground water level at that level will also reach that will also be reaching that maximum and of course as you move away from the coast so this variation will also be decreasing and eventually at some distance upstream from the coast so this tidal variation will be practically negligible and so this is in case of a confined aquifer and because of this so there will also be the this represents the variation of the piezometric surface in case of a confined aquifer now on the left hand side let us consider the tidal effect on the ground water level in an unconfined aquifer so here so there is an unconfined aquifer which essentially is spreading from the ground level here so this is the ground level all the way up to the impervious strata so this is the impervious layer and similarly this is the impervious layer in case of a confined aquifer and of course this is also the impervious layer the top confining layer which is also an impervious layer and in this case what happens is the same phenomena is observed and the when the tide reaches its maximum range that is its maximum level so the ground water level will also be fluctuating and it will show the maximum level which is h 0 times above the mean sea level and here in this case this represents the mean sea level and at any distance x upstream of the coast so this ground water table will be having an increase in the depth in elevation given by h which is less than h 0 and at some distance upstream of the ground water level so it will be 0 the ground water fluctuation is 0 so this is the impact of the tidal water level on the ground water level fluctuation. Now let us come to the effect of urbanization on the ground water level in this case the we all know that in case of urbanized localities so there will be this large amount of households with say practically impervious surface or finished surface and so which result in significant increase in the surface and now at the same time significant decrease in the total ground water recharge unless and until so there are some specific artificial ground water recharge structures are designed and installed so the ground water recharge will be highly insufficient so therefore so this reduced ground water recharge will result in gradual lowering of the ground water level unless until we take measures to have appropriate artificial ground water recharge measures so therefore the effect of urbanization in general in the areas is very what I should say is the reduced ground water discharge possibly so here this is leading to unsustained ground water levels that means eventually the ground water level will be so deep that extraction of ground water will become unfeasible and will not be feasible anymore now so this is the effect of the urbanization now let us also consider the effect of earthquake that is eq on ground water levels so here what happens is in case of earthquakes there will be a variety of effects as I was mentioning in my previous class the earth shakes and due to this shaking of earth and there will be various in the fault zones as well as in the various so there will be significant amount of damage to the earth and especially in case of structures such as buildings and other engineering structures and so because of this cracks which develop on the in the buildings which also continue along the ground so here what happens is so there will be sudden rise or fall of water level in the wells so if there is a sudden rise in the water level in a well so may lead to sudden rise or fall in well water levels if there is a sudden rise in the well water level immediately after earthquake then we should realize that there is possibly some additional very high ground water recharge taking place due to the changes in the subsurface soil layers due to earthquake and similarly if there is a sudden fall in the well water level then it is an indication that so the water from that particular well is flowing into say neighboring locations, neighboring areas so thereby there is a sudden fall in the water level of the well so these are some of the impacts of this one and now let us also consider say the impact of the land subsidence as well as external loads so these external loads as well as the impact of land subsidence on ground water levels so in this case both these land subsidence as well as external loads they result in a significant variation in the ground water levels so here what happens is wherever there is an external load applied so this load may be due to the load may be due to a particular hydraulic structure such as it may be a hydrostatic load or it may be some other load so here what happens is due to the application of load the ground shows certain amount of deflection the ground the soil above the aquifer shows certain amount of deflection and when this load is removed so this deflection does not really get removed for the simple reason that soil is not perfectly elastic and so there is a lot of plasticity in all in the soil and because of this so there will be fluctuations there will be impact on the ground water level so and then similarly this land subsidence and many places this wherever there is a external this one external wherever there is a say oversaturation of ground water so there the land becomes the soil its unit weight will decrease from gamma sat to gamma sub so in this case in case of oversaturated soils so this is gamma sat changes to gamma sat minus gamma sub gamma w which is the unit weight of water and this gamma sat minus gamma w is the submerged unit weight of water so therefore when the just below just when the unit weight of soil is at or slightly below the gamma sat so it will have the optimum moisture content and it will have the optimum strength and as the its unit weight falls so its strength also falls so this strength the fall in the strength is many times so significant so that there will be land subsidence and so this land subsidence so maybe this landslide is an example of that and so because of that so this what happens is the ground water level fluctuates so these are some of the impact of the earthquake external loads as well as land subsidence and so this one will now in this so this is how so the ground water level fluctuates practically due to various causes various reasons and so this fluctuation will result in the ground water level which is either too shallow or too deep so that wherein the extraction of ground water level or harnessing of ground water level becomes unsustainable becomes costly so therefore we should see that so by adopting appropriate measures we should by analyzing the ground water fluctuation we should ensure that the water table in case of the unconfined aquifer or the piezometric surface in case of the confined aquifer it is maintained at the optimum depth and so in the so we will stop here and we will continue although I mentioned in the title of this one the literature data sources as well as internet sources in this lecture so we will continue it in the next class. Thank you.


a context when we've got our upcoming International Conference, we've got the World Humanitarian Summit and we've got the 50th anniversary of the Fundamental Principles, they appear to be discussed and debated more than ever before. I think what we learnt was that many of the principles that we talk about today have different meanings for different actors and we really need to start debating and discussing what are their intrinsic values otherwise we risk the fact that they might turn into a hollow mantra, words that we say but we don't actually really know what they mean. I think the humanitarian system is also coming under increasing pressure, we've got the politicisation of aid and we've got very complex emergencies to deal with. The principles can provide really strong tools to cut through and assist us in decision making. So I think we heard tonight that there are principles for aspiration such as humanity and impartiality in a way to make sure we have the moral value of non-discrimination but we also have operating principles such as neutrality and the issue of independence. I think as the movement we've got a lot of work to do to demonstrate the operational relevance of the principles. I think too often we presume that because we're part of the movement that we all understand them, that we all apply them and that they're relevant. I think we've a lot of work to do to demonstrate how they're actually relevant on the ground. We've done some work in the British Red Cross on trying to analyse the operational relevance of the principles, looking in particular at the work of the Lebanese Red Cross and the Somali Red Crescent. I think those two national societies are inspiring in terms of how they've implied the fundamental principles. In Lebanon, in a country that is often divided on confessional grounds, the Lebanese Red Cross that is built up around a very diverse volunteer force has access across all communities and is able to provide medical services to everyone in need across often some very divided communities and they do that by virtue of a very strong leadership that develops an ethos and a culture where the principles matter. They do that because they hire volunteers who come to the Red Cross because of the principles and demonstrate that in their work. They do that because they communicate the principles to communities and the principles imbue everything that they do and underpin their work. In the Somali Red Crescent, it's similar. Somalia, Somaliland and Kuntland, the Somali Red Crescent operates across all of these different territories. In fact, it's the only national institution to do so. It has access in many areas in south central where other organisations are very challenged and some of this access comes because of a legacy of principles action. The Somali Red Crescent is known because the effective and reliable humanitarian services are provided during the 1990s and it can draw on that in terms of demonstrating how it is providing impartial services across the territory. I think we need to do more showcasing of this important work in the movement to learn from it but also to look at dilemmas, to see the principles not as a rule book that we apply but rather as a framework, as a formula for action and to understand where are the tricky dilemmas, where are the trade-offs and being honest about them. I'm saying that it's not easy but we actually do think that they're relevant to today to providing assistance to those who need it most. Answering a question of what should we do here, what's best, how do we help people most is often very hard and very difficult because these contexts are extraordinarily complex and sometimes what helps is to move that discussion up a level and to say, okay, what does impartiality tell us? Impartiality tells us to look for those who are most in need. And how can we do that here? Oh, we actually could. We could measure, for instance, levels of malnutrition and find the communities that are most in need and that would tell us where to go. So there's that level in which it's actually determining where your project might go. Now, the next thing that might happen there is that in trying to get to that area where people are most in need, there's, yeah, whether it's a government or an armed group or even the community themselves might not understand what you're doing there.  Are you favoring one side? And that's where you have to be able to talk to them. And if you just go and say, hey, we're really good people. We come in, we're good and we want to do good things, well, that might work. But I don't think it's going to work because these are very polarized environments, especially where there's conflict involved. There are enemies of the people you're talking to. And if they are concerned that you are there in order to help their enemy, they're not going to let you do anything. And so you have to be able to talk to them and say, no, we are independent. We are not being given money to do this. We are not being given money to help one side or another. We are neutral here. We don't want to help one side or another. But we are going to help that community there not because of their ethnic identity or their religious identity or their political or what geographic region they're in. We are going to help them because we have measured the situation in terms of, let's say, malnutrition. And that's where the highest levels of malnutrition exist. And when those same levels, when we find equally high levels in your part of the country, we would go there. And that's who we are. And that's why we're doing what we're doing. Well, FCHR carried out a piece of work over a two-year period. So it was quite an intensive piece of work to look into whether or not the principle of impartiality could be measured. And the reason we focused on the principle of impartiality was that this is really at the core of humanitarian response. It's about the allocation of resources and the prioritization of responses. We decided to carry quick and dirty, peer review of organizations' responses in the Columbia context. Very broadly, what we find in terms of key finding is that when you're looking at measuring the principle of impartiality, you need to look at what scale are you measuring. Are you measuring at the project level? That's relatively straightforward. The issue of timeframe was another one. I mean, do you position yourself in an area which is potentially at risk of a crisis? So to be able to respond to the crisis, you may not be respecting principle of impartiality by being operational there. For example, Norse Mali before the most recent conflict. But at the same time, it means that you are able to operate once the crisis hits. The other big area that we saw is that there's a constant trade-off around humanitarian principles. It's not the clear tick the box, yes, we met it, no, we didn't met it. There's a trade-off to be done in terms of decision-making. In certain cases, you may have to compromise the principle of impartiality to meet the perception of neutrality or vice versa. Welcome to this first expert panel of a cycle of events and conferences, which we started a few months ago at the Maison de la Paix in Geneva on the principles guiding humanitarian action. I will introduce the discussion tonight, but mostly talking about this cycle we are having in 2015 to study the topic of principles guiding humanitarian action, and I see that there is a large interest for this issue, looking at the crowd this evening. We are co-organizing this event with here, so I will give the floor soon to Ed Schenkenberg, who is the CEO of this new organization in Geneva. We will introduce also the organization before moving to the discussion tonight, which is called Work the Talk, Assessing the Application of Humanitarian Principles on the Ground. So as I said, this is part of a broader cycle of events, which will take place in Geneva, but also in other locations. Last year, we had a cycle of conferences and debates on new technologies and the modern battlefield. This year, we decided to study this topic of principles guiding humanitarian action, together with our colleagues from the Red Cross and Red Crescent Movement, with various humanitarian actors, with also experts from the military, from government, to look at the challenges regarding the application of humanitarian principles in the field. So we are not aiming at having theoretical discussions on the values or the theories underlying humanitarian action or humanitarian principles, but looking at how they are applied today. And this event takes place, or this series of events will take place at a time when humanitarian principles are challenged, first because we see new emerging actors involved in the humanitarian organization, and we may need to build a new consensus on what these humanitarian principles are, but also because we see many restrictions imposed on humanitarian action in the field, in conflict situations, sometimes also in disasters, imposed by parties to the conflicts, and so there is a need also to respond to these challenges. 2015 also gives us a good pretext to explore these issues, because it's actually the year which marks the 50th anniversary of the adoption by the Red Cross and Red Crescent Movement of its seven fundamental principles. This year we will have also in Geneva the next international conference of the Red Cross and Red Crescent in December, which has chosen to, or the main theme, the overarching theme of the conference will be the fundamental principles, principles in action. So there again, I think that our discussions, our cycle of events will feed the discussions at the conference. Further ahead we will have in 2016 the World Humanitarian Summit, convened by the UN Secretary General, which will be a first summit of this importance on humanitarian action. And we hope that the discussion on humanitarian principles, on the fundamental principles, but also principles guiding humanitarian action at large will also inspire discussions during this World Humanitarian Summit. So that's why we have this series of discussions and we invite you to follow them as you are interested by this topic. You can find more information on our future events, looking at this QR code at the back of the leaflet on your seats. You will be able to register to our newsletter and be informed about our future events, cycle of debates here in Geneva, but also in many locations, on site and online. Last comment, we'll have also an issue of the international review of the Red Cross tackling this subject. At the moment we are receiving contributions from all over the world on contemporary practice of humanitarian principles. So thank you for coming this evening. And after this short introduction, I'd like to give the floor to Ed. I don't know, there you are. So just one word of introduction. Ed Schaikenberg was previously Executive Director of the International Council of Voluntary Agencies, IGVA. He was also Chief Executive of DARA, Development Assistance Research Associates. He has done extensive research in the field of humanitarian action and in the field of the humanitarian principles. He's here today to present the Humanitarian Exchange and Research Center here. The new organization is leading E&G. Thank you. Thank you very much, François. Thank you very much for those kind words. Let me also express a word of warm welcome to all of you. It's a real pleasure and honor, in fact, to be here and to be one of the co-organizers of this debate. There's two questions I've been receiving. I'm not entirely new, as some of you know, to Geneva. And there have been two questions I've been receiving in the last couple of weeks, quite regularly. One who is involved and I'm actually quite happy that all my colleagues are here, which is a small team for now, but and also some board members, in fact. And then the next question I get. So what is it that you do? Let me just say a few things on that. Because when I get that question, what I answer is, well, in fact, what we do is we look at the gap between policy and practice. And about 10 days ago, I was at a meeting in the Hague, the Dutch Humanitarian Summit, a rather large event in a rock hole, actually, which a rock concert hall that was quite an actually interesting environment. But what I really wanted to say, in fact, was one person here who was also there. And I think Tomon, I know you're here. We saw each other exactly. We saw each other already before the meeting. Tomon is a medical doctor working with MSF. He's from Damascus. And at that meeting, I think Tomon, you made a very passionate point. You said, actually, all of us here in that room, so perhaps all of us here also today, we need to be on the ground. We need to be where it matters, where it matters most. Because particularly in meeting rooms in Geneva, and that's certainly my experience in Geneva, we create our own reality, which is not the reality when we see it as we are on the ground. And the few times I do go out to the field, indeed, I do see things that are very different the way that they're portrayed here. So that's exactly why I think we get created here to try actually to bring that reality as we see it at the field level, to bring that to meeting rooms such as this one. So in that sense, this theme of today for us is a very logical one. Humitarian principles. It's our DNA. It's what our common denominator will bring us together. And precisely on humitarian principles, what I'm hearing these days in meeting rooms in Geneva is that we're delivering principled humitarian action. That's great. But what I get a little suspicious when I hear, as we all know, the humitarian community is growing. It's growing in numbers and it's growing in terms of its diversity. And when all these very different actors are saying the same thing, we're delivering principled humitarian action. I get a little bit suspicious. What actually do we mean by that? We're saying we're delivering principled humitarian action, but we don't really talk about principles. And that's exactly what I hope we'll do today. Lastly, this meeting in that sense, and this theme in particular, does, I think, come at the right time. We have to vote humitarian summit going on, the Red Cross movement conference late this year. Other processes going on in Geneva, like the core humitarian standard. And I think it's essential that those processes are informed by humitarian principles and that they really, in that sense, look at the content of humitarian principles instead of just saying, well, we're delivering principled humitarian action. So that's what I hope we'll do today. That, in fact, we are influencing those processes. And I really hope that you will contribute, in that sense, your experience and thinking to our discussions. Thank you very much. After this introduction, I'd like simply to give the floor to the moderator. So Dr. Helen Doham, who is the director of our Department of International Law and Policy here at the ICRC. Before becoming director at the ICRC last July, Dr. Doham served in the ICRC and also in the Australian Red Cross. She was director of International Law Strategy, Planning and Research. And she is also a senior fellow at Melbourne Law School. So she will introduce the panel and the panelist. Thank you, Helen. Well, thank you very much. And may I add my very warm welcome to you here this afternoon. I was going to say this evening, but it is quite delicious to have an event at this time. We could pretend we're still working, but it's almost evening time. So a warm welcome. And we were delighted to see with the number of different numbers and the types of representation that we have here today. So welcome on that. As has been said by the two previous guests, it's a time at the moment where we hear a lot about humanitarian principles. And I'll put them in talking marks for a minute, because we hear them articulated at the World Humanitarian Summit. We're looking at them with our upcoming international conference. They seem to be everywhere. But in reality, how can we make sure that they don't become an empty mantra? Words that we say and we all not ahead about, but actually have different visions about, have different attitudes and implementation. It's fine to have a diversity when we discuss things. But do they still have resonance? And how can we stop just listing them and start really digging down and working out what they are and what we need to do? If we're not careful, there could be the chance that they could risk losing their practical and very moral compass that provides many of us with the capacity to move forward, as well as a practical, operational element, unless we really start having hopefully discussions like we're having tonight. Because in fact, the fun, the principles, the humanitarian principles, and certainly from the Red Cross and Red Crescent's point of view, the fundamental principles have that too dual purpose. They provide with for us some sort of compass where we go in our humanitarian DNA. But they also provide in some of the principles such as neutrality and independence, a really practical tool to help us implement our mandate and to make sure we do so with as close as proximity to those who have needs as possible. But today we see, as was also alluded to by the previous speakers, an increased polarization of aid. In the last few decades, we've seen the development of the term stabilization and whole of government approaches to tackle fragility in other complex emergencies. Now, in this framework, some organizations have embraced a broader political approach of a transformative nature, transforming the society, transforming the economic or political structure of the countries in which they're working. Now, these organizations often claim to be principled on one hand, but on the other hand, to be rights based and very much embedded in the work, whether it be peace building or conflict resolution. And this, I think, we have to look at and reflect upon really deeply these tensions and how we can as a sector perhaps be more honest at times in articulating what principles we are utilizing in our activities. We've also got the very obvious issue, which is of concern to all organizations and states of the practical safety of humanitarian workers and that those organizations that actually distort or even reject the idea of the fund of the principles. And in particular for the Red Cross and Red Crescent movement, the fundamental principles can create real problems in terms of security on the ground. And we've seen that sadly recently. On the other hand, there are studies that show whilst principles such as neutrality independence are not the silver bullet by any means, they can significantly assist or at least contribute to safe access in some insecure areas. So I think we have to be careful. They're not the panacea, but they can have some practical value. Now, getting back to the panel here today, what we're really going to focus on is a range of questions. And the way I'm going to undertake it is introduce each of the of our panelists and I'm delighted with the superb representation we have today. Ask them to give a five minute snapshot of the vision or the views they have in relation to the humanitarian principles. I'll then go to a question and answer mode. Well, ask them to engage on particular topics and then we'll throw it open to the audience. I see in the audience are richness and depth of people who've got experience in this area. So we also want to engage with you. But to start with may I introduce the panelists to my right is Kate Hull, Executive Secretary of the Steering Committee for Humanitarian Response. Welcome, Kate. To my left, I have Mark Dubois, the former Executive Director of MSF UK, but now more importantly, an independent writer and researcher in this area. And then to the far left, we have the pleasure of having Socha O'Callaghan, who is the Head of Humanitarian Policy at the British Red Cross and is the co-author of numerous publications. So we've got a nice, a nice narrative at the table here of different experiences and different institutional takes on these issues of humanitarian principles.