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as well as a you know a simulation wherein we had given a three phase fault. And one of the key phenomena which we observed was that in the especially that it was observed in the rotor speed and the angle the phenomena which was observed was the loss of synchronism whenever there is a very large disturbance I mean after for a certain large disturbance also there is a center of inertia motion or you can say the common speed of the system changes in case there is a load generation imbalance which of course can be corrected by governors. In fact there are two things which affect the motion of the center of inertia the in fact the load generation imbalance is affected by the governor characteristics as well as the frequency dependence of loads of course the frequency dependence of loads is generally weak and it is not a good idea to rely completely on the load frequency dependence to get you to an equilibrium speed the center of inertia speed which is an equilibrium. But if you depend on the load frequency characteristics to get you to an equilibrium that perhaps is not a very good idea because for example if there is a large load generation imbalance which occurs then you will find that the frequency settles down to a value which is very low low or high of course it is low in case there is a load is greater than the generation and vice versa. Now governors should be you know enabled governors or what is known as the primary response has to be enabled on all generators or at least the major generators in the system so that each of them in some ways contributes to trying to maintain the load generation balance. So of course there is an issue then of how to share the you know load amongst the various generators you know so for example for a particular schedule there is a load generation balance and you are operating at a certain frequency but if the there is suddenly a load change then the frequency tends to deviate and all the governors which are enabled respond. So various generators increase their mechanical input power and therefore the electrical output power and the frequency tends to an equilibrium. The sharing is dependent in fact on the gains or you know gains are in fact the inverse of the droop of the governor characteristics. So that normally governors are proportional controllers in fact the proportional gain in fact determines the load sharing. If you look at for example suppose one of the governors it changes its mechanical power based on the difference between the reference value and omega 1 the actual speed measured at that generator this is the gain. So the change in the output of mechanical output of a generator will be basically given by this. Now this is of course true of other general governors as well. So in another generator the turbine changes is mechanical power as per this rule.  Why?  In principle even a load disturbance can cause relative angle motion and possibly in certain situations a loss of synchronism situation. But we will assume that the system does the relative motion is stable and the system will retain synchronism in that case omega 1 and omega 2 in steady state are going to be equal. Therefore in steady state your delta p 1 and delta p 2 is equal to k 1 by k 2. So the gains of your governor in fact determine how much each generator shares this extra load. Remember that in an integrated system what matters as far as the center of inertia frequency or the common frequency of the system is the total load generation imbalance. So if once I have integrated all the synchronous generators that is connected them by AC lines you cannot say that a load belongs to a certain generator. So all the generators put together are pooling in their powers and meeting that load. So any load change affects all generators which have a governor and you will find that this mechanical power change is proportional to k 1 by k 2. Of course this is as I mentioned last time a nice way to implement the load change. I mean you can for example keep k 1 and k 2 so that generator share the load according to their ratings that is a reasonable thing to do. So the proportional kind of scheme of maintaining you know kind of changing the mechanical output power of the turbines is quite a good idea. In fact one consequence of having a proportional controller is of course that in case there is a load generation imbalance if I want to change the mechanical power output of a machine then there has to be some steady state error between omega ref and omega. So whenever you have these kind of governors your frequency does not come back to the original value before that is what existed before the disturbance load disturbance. It will have some frequency error but this in spite of this I mean you can choose a gains for example large enough. So if your gains are large enough in fact this error is smaller but this proportional scheme is a nice way of sharing the loads amongst various generators and one of the important thing is a completely local control all you require is the local speed of the machine. So in this way although generators may be interconnected and spread hundreds of kilometers apart so thousands perhaps so still you can have a nice scheme to control the center of inertia motion. The other phenomena which we discussed was of course the loss of synchronism. So in today's lecture let us just recap this aspect also. So today's lecture in fact is we will just think of what happens when you have got even larger systems. We of course consider two machine system in the previous class we will go for even larger systems. When you talk of relative motion there are two issues whenever you look at any small disturbance given to a multi machine system you will find that one of the prominent patterns there are of course other patterns as I mentioned in the previous class but one of the prominent patterns for small disturbance is a low frequency oscillation which occurs around 1 hertz. So that is essentially you know associated with the motion of the you know or rather the states delta and omega of the machines and that is of course a relative motion between the machines. So what we call as power swings or low frequency oscillations etc are in fact electromechanical oscillations which involve relative motion between the machines. Now this manifests as an oscillation.  So that is an important point about the relative motion. However for large disturbances last time we saw a large fault large duration fault. So for large disturbance there is a possibility of loss of synchronism of course depends on the disturbance itself and what operating point you are. So loss of synchronism also is a phenomena associated with the relative motion of machines. Suppose you have got the machines not coming back into synchronism but accelerating or decelerating with respect to each other then you would say that the relative motion is unstable and loss of synchronism has occurred. Now loss of synchronism is not acceptable it occurs for certain large disturbance does not occur for most large disturbance and it is a endeavor of an operator to ensure that the system has enough margin it is operated a bit conservatively. So that you do not lose synchronism one of the things which we perhaps did not discuss much in detail but something which you can do is try to increase the power flow bit on transmission line. For example in the two machine system if you increase the initial power flow through the transmission lines and then subjected to a particular disturbance it becomes more susceptible to loss of synchronism. So one of the endeavors of a system operator is to operate the system a bit conservatively so that the system can withstand certain credible disturbance. In fact even while planning the system planner will try out few credible contingencies and ensure that at least for loss of a credible kind of disturbance that is a fault with the loss of a transmission line the system remains in synchronism. What we discussed sometime back of course was this loading generation imbalance which is associated with the center of inertia motion that is the overall movement of the system. So that may or may not involve this center of inertia motion can be thought somewhat as something distinct from the relative motion. So of course as I concluded in the previous lecture it does not mean that there are no other phenomena which can occur dynamical phenomena which can occur. We are focused on two particular phenomena this is relative motion stability as well as the center of inertia motion stability which is associated mainly with the electromechanical states but you can have other modes of instability involving for example poorly designed controls etcetera. What happens when you go from two machines to three machines? So to just kind of give you a crude analogy again of a system which is kind of will give us at least some idea of how the electromechanical modes behave of a process. Remember whatever analogy I am showing you here of a spring mass system is actually not completely does not completely reflect our system. Remember our system is many other modes as well the order of our system is quite high it involves not only delta and omega states but several others too. So whenever I am talking of this analogy it is only highlighting or kind of it is an analog of only the electromechanical pattern which you see in a power system behavior. So if you look at this multi mass multi spring system what really holds true here is that the center of inertia motion that is the motion of this that is you can talk of M 1 V 1 plus M 2 V 2 plus M 3 V 3 divided by M 1 plus M 2 plus M 3 this is the center of inertia speed it is proportional to the sum of the external forces on the system that is F g 1 plus F g 2 minus plus F g 3 minus F l 1 minus F l 2 minus F l 3. So this aspect of the motion in fact remains the same we just add up all the torque equations or the what you call the swing equations of all the synchronous machines just add them up you will get this equation of the motion of center of inertia that is of course something which what we saw in the two machine system will still be valid for a three machine system and so on. So even a 500 machine system the center of inertia motion is going to be equal to the sum of the mechanical power input minus the electrical power output that is the sum of loads and the losses electrical losses. But a much more interesting point which you may consider at this point is what about the relative motion in case of a single machine connected to infinite bus we considered of course the relative motion consisted of the motion of the machine with respect to the voltage source. When I got a two machine system what we saw is the relative motion between the two machines delta 1 minus delta 2 what happens when you have got 3 or 4 or 5 machines connected to each other. Now looking at this analogy of course gives you a picture of what is going to happen. Now what you have now is 3 machines so 1 2 and 3 3 machines are there and suppose I give a disturbance to this system that the kinds of patterns you will see are going to be again quite interesting one of course is the motion of the center of inertia. But if you look at a 3 machine system just to highlight a simple kind of situation suppose you have got one large mass connected to two other small masses and they are connected by relatively a stiff spring.  Now if you look at the relative motion in this case forget the center of inertia motion we will talk only of the relative motion. It you can guess of course this is something I do not prove here now I do the mathematical analysis of it. But you can just guess that in case this spring is very stiff that is difficult to stretch it. Whereas this spring is a bit loose I mean the sense you can stretch it quite easily this mass is large these two masses are small. Then you will find if you do a Eigen value analysis you can actually write down the equations of the states you know the differential equation corresponding to x 1, x 2, x 3 and v 1, v 2, v 3 which are the velocities. In that case if you look at the Eigen values in the modes of the system this something you can do with typically you can choose some simple small values of m 1, m 2 a large value of k small value of k large value of m 3. In this particular system in this particular system what you can expect are two actually two oscillatory modes corresponding to relative motion of the machines. So, if you take a three machine three mass spring system you have got you will have two oscillatory modes which actually if you look at the Eigen vectors corresponding to these oscillatory modes that is the complex pair of Eigen values which will come about when you do the Eigen value analysis of this system. Two oscillatory modes one would be of high frequency mode one would be a low frequency mode. So, I encourage you to just do this Eigen value analysis for this system suppose this is 1 kilogram, this is 1 kilogram, this is 100 kilogram or 10 kilogram you can take something extreme. So, that you know what I am trying to tell you will come out very clearly. Let us say this is k is you know 10 Newton per meter and this is k is equal to 1 Newton these are just fictitious values which I have asked you to just consider to do the Eigen value analysis. Now, if you do the Eigen values of the system as I told you will find if there is no friction the Eigen values will come out to be this. In fact, plus or minus is relevant here there will be two Eigen values zero Eigen values these two zero Eigen values of course, are associated with the motion of the center of inertia of the system the motion and actual x 1 x 2 x 3 values corresponding to the center of inertia motion or the common pattern of the system. If you have got friction then you will have a Eigen values of this kind and you will have one zero Eigen value and one sigma 1 sigma 2 and sigma 3 are less than 0. So, this is in case you have got friction, friction is provided that is if you make the external forces a function of speed. So, this of course, in a in a multi machine system or in a actual power system is provided by governors and load frequency characteristics of the system. Now, the two frequencies are in fact these are corresponding to the relative motion and if you look at the relative motion it is easy to guess this is only a guess I am not really proving anything to you can actually do an Eigen value analysis and show it is that in this particular system not saying this first for all systems is that the low frequency oscillation you will find that these masses look at Eigen vectors the information that will give you is that the masses m 1 and m 2 whenever only the low frequency mode is excited the masses m 1 and m 2 move together against the big mass m 3. So, these are the two masses m 1 and m 2 and this is m 3. So, you find that there is a low frequency oscillation associated with these two masses moving against the large mass there is hardly any relative motion between the smaller masses whenever the another pattern of motion is when this m 3 mass does not move much, but there is some relative motion between m 1 m 2 of relatively high frequency. So, you have got these three patterns which you will rather three patterns one with the center which corresponds to center of inertia and the relative motion there are two patterns two oscillatory patterns one is a high frequency one involving masses m 1 and m 2 and low frequency one involving masses m 3 moving against masses m 1 and m 2 which move together. So, this is the pattern which you can infer by doing an Eigen value analysis. Now, the important point which of course I wish to make here is that whenever you have got a three machine three mass spring system you have got two relative modes of oscillation. Now, in general whenever you give a disturbance if it is a general disturbance you will find that all the modes are excited. So, a general disturbance no special initial conditions you will find that the masses move together there is a this high frequency mode and a low frequency mode. So, you can have all this. So, this kind of behavior you can expect. So, if you take a 500 machine system you will find that there are you know 499 relative modes of oscillation yes that is true not all of them are excited for all disturbances. If you give a disturbance or a initial condition which is not the equilibrium condition you will find that certain modes are excited others are not. So, remember that in the n machine system the n minus 1 relative modes of electromechanical oscillations. Now, one more issue which you should remember is that whenever you go from us you know the relative motion although in the spring mass system where it is a linear system a power system is a non-linear system. So, for large disturbances again you may have relative motion going you know is you can have a loss of synchronism phenomena in which machines separate out from each other that is you have got machines one of the machines accelerating in one machine decelerating this is a non-linear phenomena which cannot be predicted by Eigen value analysis. So, you can have a situation where the machines you know m 1 m 2 for example move together and they go out of synchronism with m 3 that is the springs break you can look at it that way the springs are non-linear than the springs can break. So, you can have loss of synchronism phenomena even in multi machine systems larger systems also have this phenomena of loss of synchronism. So, what we have seen in the single machine infinite bus system is also seen in a two machine system it is also seen in a multi machine system when you go from graduate from a single machine connected to a voltage source to a two machine system the additional phenomena which you have to consider is the motion of the center of inertia when you go from a two machine system to a n machine system the center of inertia motion of course remains there, but you have got n minus 1 swing modes or patterns, but again the loss of synchronism corresponding to relative motion is still there you can have loss of synchronism for large disturbance only of course is an important point which you should remember is that in multi machine systems groups of machines may lose synchronism with respect to other groups of machines. So, that is the major difference which you should note and as I mentioned some time in case you lose synchronism that is one set of machines has a frequency which is which tends to be different from other center of machines then you will have oscillations which is something we saw in the previous class you have got oscillations in the electrical power as well as several at several places for example, in this example the midpoint voltage tends to oscillate this is a 50 hertz waveform, but you see the magnitude goes on going up and down. So, in case two machines which are interconnected lose synchronism in that case you have got wild oscillations in voltage and other quantities and usually distance relays will think this is the fault whenever you got a voltage 0 any distance relays which observes this kind of voltage and current will tend to trip and then you have got a separation of the two systems and as I mentioned some time back whenever you have got a loss of synchronism phenomena you have to separate or you inadvertently or in an uncontrolled fashion you separate and once you separate you are left with the other problem that is maintaining load generation balance in the separated systems. If you remain connected you will have see a very large these kind of oscillations and variations which cannot be tolerated because they can lead to equipment damage. So, loss of synchronism is never tolerated for more than you do not allow the machines to slip poles as they say. Several years ago the western part of our country was a synchronous grid. In fact now it has got integrated to several other grids in the country, but this is the scenario which was prevalent about 4 or 5 about 5 to 6 years back when western region was kind of an independent system it was consisting of the states which are shown here. It was seen that for large disturbances groups of machines on the eastern part of the western grid there are large machines here you know at Vindhya Chalkorba and so on. The large number of coal base generating plants here they separated they normally used to separate out if the system was subjected to large disturbances. So, there are several instances where there are fairly large disturbances and the system used to separate out in the sense that these machines used to accelerate with respect to these machines while still remaining connected. The center of inertia motion would have been not really prominent, but the machines would be separating out with respect to each other and because of which the distance relays on these lines used to trip and cause islanding of the western part in the eastern part of the western region. And once this used to happen this used to be a load deficient or other generation deficient area. So, the frequency in this islanded system would suddenly drop and often the system used to collapse. Interestingly in Mumbai we had a controlled islanding we have in fact a controlled islanding system which kind of isolates itself from the rest of the system in case such a situation. In several they have certain checks if this happens they separate out Mumbai from the rest of the western grid. So, this is an example of a controlled islanding, but you can have uncontrolled system separation as well. So, if you look at relative angular stability I should use the word relative angular stability because there is also corresponding phenomena of the center of inertia motion is also an electromechanical phenomena. So, we will talk here in these two points which are here are relating to angular stability. Remember as I mentioned sometime back small disturbances you generally see an electromechanical behavior which is oscillatory which is a mixture of n minus 1 modes. Remember that you can analyze small disturbance stability by Eigen value analysis of the linearized system around an equilibrium point. Remember the power system is a non-linear system. So, if you want to do small signal analysis you have to linearize around an equilibrium we have done this for a study of the AVR some lectures back. You can show of course that for certain operating points the linearized system has got Eigen values which are positive real parts. So, sometimes you can have in fact small disturbance behavior unstable too. So, this is something you should remember large disturbances on the other hand are disturbance dependent they are also operating point dependent and quite inappropriately power system engineers refer to the phenomena of large disturbances as transient stability. Transient instability or transient stability refers to large disturbance. So, if some power system you know confronts you with the word transient stability what he really means is large disturbance instability which results in loss of synchronism. So, transient instability means that it is disturbance dependence and remember that in a synchronous grid that is synchronous machines connected by AC lines it is always found to be an issue. There will always be some large disturbance for which a system loses synchronous. So, you take any multi machine system connected by AC lines synchronous machines connected by AC lines there will always be a large enough disturbance for which the machines lose synchronism. So, just to make this now absolutely clear I hope we will not have to recap this again. Suppose you have got this is a plot of generator speeds under various situations in a multi machine system of course, it is a multi machine system, but I have plotted actually only three machines three speeds here. This is a typical situation if there is a sudden load throw off in the system the generator speeds tend to accelerate. So, if there is a general load throw off you will find that swings you will see these power swings corresponding to the oscillatory motion, but more prominently you will see the center of inertia speed is increasing and of course, if you have got governors or load frequency dependence loads of frequency dependence eventually the system settles down to an equilibrium somewhere at a higher speed. Of course, if you have got one machine with an integral type of governing system or also called an isochronous governor you may find even that the frequency goes down back to the original speed, but most governing systems in a multi machine setup rather all in a multi machine setup you cannot have you know many machines having a proportional controller an integral controller at most one can have an integral controller why that something you try to think over, but typically all machines have proportional type of droop characteristics that is you will have some steady state error in frequency the governor will not get the frequency back to 0 back to the previous speed you may have to do some extra work in order to get the frequency back to the original frequency that is called secondary control. So, that something will not do right now in this course, but you can look at any undergraduate text book they will talk of governor action coupled with slower secondary control. If there is a generator trip on the other hand you will find that the frequency drops and although relative motion is also excited the most important thing here you see of course, is that the frequency tends to the center of inertia frequency will tend to drop and settle down. So, this is a situation where the common that is the center of inertia motion as well as the relative motion is stable if this occurs and this frequency deviation is not too much nobody will be worried too much everybody people will finally say fine we have settle down to a frequency which is slightly different from the original frequency usually power system engineers cannot tolerate anything more than half a hertz or so. So, that is the absolute maximum of frequency deviation of course, in our you normally this the amount you can deviation you can allow depends on what the turbine blades in a steam turbine can you know tolerate looking at the figures at the bottom what I see here what the plots which I have shown here is two machines the speed of two machines is kind of tending to deviate from the machine which is shown in red generator speed which is shown in red. This is an example of a large disturbance angular instability or what I termed as transient instability this is a loss of synchronism phenomena and you will find that it is relating to the relative motion between machines. You also can have we have seen this in the single machine infinite bus with an AVR you can also under certain circumstances have the machine the synchronous machines having small disturbance instability this can happen if for example your control systems like an AVR have very high gains and they adversely affect the oscillatory modes this electromechanical modes that can happen we have seen that happen in the single machine infinite bus system. You find that you have got this motion which does not die down usually it is manifest is growing oscillation and is triggered by any disturbance big and small. So, what you find is that we do have situations in which a system operator is operating the system and he finds that after sometime he notices that there are oscillations which simply do not seem to be dying down. This is occurred in the past and what he is effectively seeing here is a situation of small disturbance instability where there is no large disturbance which is occurred in the system, but you have entered an operating point or a new equilibrium point of your system is such that the system is small disturbance unstable. So, you may actually have these electromechanical modes going unstable small disturbance unstable under certain situations you cannot operate this way you will have to do some corrective measure. So, that would involve at least at the planning and non real time operating stage tuning of controllers. So, that this does not occur of course remember that something which should always keep in mind is what I have told you right now is a specific aspect the electromechanical oscillations are a specific and an important phenomena which occur in synchronous grids, but there are other you know kind of phenomena and we should have some idea of the time scales which are involved when studying them. Luckily there are there is a clear separation of you know the time scales which are associated various transient phenomena. For example, if you look at the scale at the bottom the fastest transients are those associated with lightning and switching. Then you have got the slower network transients associated with the electrical network as well as what you call as torsional transients associated with the shaft of the rather the shaft and mass system corresponding to turbines and generators. These are also phenomena which are manifest, but these are faster phenomena. Relative rotor angle dynamics are in fact what we were studying now they are occurring in the time scale or the frequency range of 1 hertz you know half hertz 1 hertz 2 hertz half hertz you know that range you know these are relative rotor oscillations. You have got slower frequency dynamics associated with the center of inertia motion that of course depends on the overall inertia of the system the sum of inertia constants of the system. So, it is a bit slower in fact prime mover dynamics those associated with the boiler etcetera are very very slow compared to for example, rotor relative angle dynamics and of course, very at a very slow level you have got aggregate load changes load there is a kind of pattern to how load changes over the day. So, that is a very slow change. So, luckily for us all these phenomena well separated out in time. So, actually that in that sense we can analyze each phenomena separately. So, you know that is an advantage I could talk of relative angle motion without worrying too much about for example, some of the real Eigen values of the some of the patterns associated with the damper bindings of a synchronous machine. So, you could actually look at electromechanical variables in a focused way because one of the reasons that is a good time separation between various transients you need not worry about lightning switching transients whenever you are studying about you know relative motion dynamics. So, if you recall it is important to correlate what we have done before in this course and what we are doing now whenever you are studying slow transients you can assume that the network and some parts of the system are in fact, in quasi steady state. So, for example, if you are studying electromechanical transients you could afford to neglect the network transients and the stator transients because they are relatively fast. This is something we have kind of beaten to death when we were studying the in the first few first 5 to 10 lectures. On the other hand whenever you are studying lightning and switching transients you can for all practical purposes assume that the speed of the generators etcetera is constant. In fact, you can most of the times whenever you are studying such transients you can safely assume that the machines is a constant speed running at a constant speed you may even model a machine as a voltage source. So, remember that our modeling it has to be consistent with the kind of phenomena we wish to study. Now, correspondingly you can also see what are the controls you know whenever talking of transients you can also talk of in terms of controls. If you look at equipment protection and power electronic controls they occur at a very, very they are a quick acting. So, for example, the primary protection can act within a few cycles you know for example, if there is a three phase fault on a transmission line you can the state of the art is that you can switch it off in you can trip out that transmission line and isolate the fault in just two or three cycles you can have differential protection which acts even faster. So, this is the equipment protection acts at a very fast scale. So, does power electronic controls. So, if you recall for most electromechanical you know studies we could assume that a excitation system is the converter is modeled simply as a kind of a gain you give a control system and it implements the order because that is because power electronic controls also in a system are extremely fast. So, if I got HVDC systems or the static excitation systems you need not operate you know model them in excessive detail if you are studying for example, relative rotor angle dynamics or prime mover dynamics. So, just remember that modeling and analysis and in fact, the tools which you use for certain phenomena are kind of designed for that phenomena. Of course, you may take an approach that I will model all the whole system in full detail. In fact, you can model network transient state transient everything and use a variable time step in implicit method to integrate or simulate this system. This is also a viable approach. In fact, nowadays there is less of a distinction between fast and slow. You do not have different programs to study fast dynamics, slow dynamics, long term dynamics. You can in principle make a program in which you use an implicit numerical integration method and have a variable time step. So, you can capture not only the fast transient, but the slow transients as well. But at least whenever as a first step or to keep a good distinction between all the phenomena. In fact, people have written different programs with different modeling assumptions for different phenomena. One class of course, I am not you know we will be talking of rather methods for improving stability a bit later in the course.  You can actually think of also implementing what are known as system protection schemes. For example, let me give you an example.  So, you can what you can do is if there is a big load throw off and the frequency falls on precipitously rather it should rise precipitously. Suppose, for example, let there is a generation trip and therefore, the frequency drops precipitously and your governors are not able to act well in time. Then you may think of deploying schemes like rate of change of frequency protection. That is if the rate of frequency drop is higher than a certain value trip out some loads. So, you can have these kind of local schemes which try to ensure that the system remains you know the frequency of the system remains within a certain value. So, you can have these are also known as emergency control schemes or rapid action schemes and so on. So, these are kind of what are known as system protection scheme which operate a slightly slower level. They are not what you call equipment protection schemes. So, they are typically act in the range of half a second, 1 second and so on. In fact, with the availability of synchronized non-local measurements under what are known as wide area measurement systems. One can devise non-local you know when I say non-local means you are using signals which are time synchronized and obtained from various locations in the grid. You can use these signals to fine tune some of your system protection schemes. So, this some in interesting research area which some of you can think about taking up. Governor prime mover controls are somewhat slower than system protection or equipment protection schemes typical equipment protection and system protection schemes and of course, manual control is the slowest amongst them all. So, this is a good I giving you a kind of idea of various transients which you can encounter in what are their what is the bandwidth. Let us just look at some actual system. See this is what I am going to show you next is the kind of measurements we have observed in our grid. You know for example, at the present time in India you have got if you look at our country there is a approximate map. This portion of the grid is one synchronous grid that is their synchronous machines connected to each other by AC lines. So, if you have a synchronous generator here you will find AC line path right up to any generator here as well. So, this is basically a synchronized grid you have another synchronized grid this is the southern grid. These two grids are not connected to each other right now as of 2010 by AC lines they are connected by DC lines. So, you actually rectify the voltage invert it again. So, these two systems need not be of the same frequency, but generators here if they have to have a stable relative motion then all of them have to be running in synchronism in steady state. Now, what we did was we have measured frequency at fairly distance distant locations in the grid. In fact, the ones I am going to show you are approximately 400 roughly 200 300 to 400 kilometers apart. This disturbance which I am showing you is a generator in trip. So, generation trip has occurred and what you notice here of course, is that the frequency drops. So, the center of inertia motion is suddenly excited whenever there is a load generation imbalance and this is a relatively large generation trip is an expanded view actually which occurred somewhere the interesting thing is that is generation trip occurred somewhere in eastern UP. Eastern UP is a state here. So, it occurred somewhere here and what you notice is that the frequency change which is measured in the western region. Since this is a synchronous grid and relative motion was stable for this disturbance the frequency here, here, here, here would have been the same, but since there is a sudden load generation imbalance caused by a generation trip the frequency dropped here. It in fact, would drop everywhere in the grid because for this particular disturbance the system did not lose synchronism. Relative motion was stable, but the measurement was done here and interestingly for load trip here for generation trip here the effects are seen more than 1500 kilometers away in the western region and this is because they are all interconnected by AC lines synchronous machines connected by AC lines. So, you see that the frequency drops down at a certain rate then there is another frequency there is another probably generation trip here then again the slope becomes normal. So, probably there was a load tripping here. In fact, if you look at this slightly compressed graph what you notice is that the frequency drops kind of has a lower slope here and at 48.8 roughly you have under frequency relays which are system protection schemes which tend to get that the get back the center of inertia frequency back to normal. Remember that the machines or the frequency at Mumbai, Sangli and Surat which are all in the western region are practically the same forget all this noise which appears here this is measured at the distribution point. So, you have got a lot of noise, but you notice that all the frequencies are moving together you can hardly distinguish between the three locations the frequency. So, there is no loss of synchronism occurring the machines all move together, but because there is a load generation imbalance is a very prominent motion of the center of inertia of the system. This trip remember occurred 1500 kilometers roughly away from the point where these measurements were taken this is another disturbance, but this is a fault situation this is a frequency measured at four locations in the western grade for a fault which occurred in the western grade. So, what you notice of course, if you look at it carefully is that there is a very you can see relative motion oscillatory motion of one hertz. So, you will find machines in the north part of the western grade western part of the country that is at Amdabad and Surat are swinging together against machines in Mumbai and Sangli. So, this is approximately one hertz motion and they are moving out of a. So, you actually see this relative motion this relative motion is of course, stable because these oscillations eventually die out with time. So, that is an interesting really interesting phenomena which are seeing here which of course, is consistent with what we have understood. Remember that in case you have got synchronous machines say connected like this two synchronous machines in close proximity connected to each other via say a long transmission line to another machine you will find that there is a relatively high frequency local mode and in which these two machines swing against each other and there is a low frequency oscillation in which the two machines swing together against this machine. So, you can have a mixture of local and what you call inter area modes even within a power plant if there are many units you can have what are known as inter plant modes. So, I refer you to the our discussion of the two mass spring system three mass spring system where you have got two masses connected to a large mass the kind of behavior you have there. So, in fact, you can break up the motion into several modes and in some cases you can very easily distinguish between oscillations within a plant or between generators in close proximity or machines moving together against other machines which are far away these are called inter area modes. So, you can have this kind of mixture of several modes remember I told you that for a n machine system you can have n minus 1 modes. So, you have got all these mixture of modes in certain situations you can actually distinguish them you have got a high frequency inter plant modes relatively higher lower frequency local modes and much lower frequency inter area modes. So, you can have all these modes of electromechanical modes of relative motion. Interestingly for last disturbances you may lose synchronism this of course, is something which you have discussed sometime back, but it is difficult to sometimes predict instability. For example, which group of machines will lose synchronism with respect to other group of machines it is a bit difficult to predict. In fact, if you look at the movement of the machines following a large disturbance sometimes just by looking at them for a short while it may not be possible for you to tell whether the system is going to go unstable a few seconds later or not. And if it goes unstable what are the groups of machines how will the system separate out that is something which you cannot easily tell without actually doing a simulation on a system with a two machine system there is only one mode of separation the two machines fall apart. Single machine infinite bus system the single machine loses synchronism with the infinite bus in a multi machine system that may be much more tough because you can have many modes of separation just like you can have many modes of oscillation for small disturbances for large disturbances for certain large disturbances you can have many modes of separation and that may be not easy to tell which machine is going to fall within which group an accelerating group or a decelerating group. So, relative motion a large disturbance relative motion leading to loss of synchronism may be difficult to it may be difficult to predict unless you do a simulation I actually see there is no you have to do it the brute force way sometimes to really and get an answer to this question. So, just look at this graph which I have shown you here these are the relative angle plots for the motion of around 300 generators in the western region this is a kind of an academic, but realistic study not a real study, but a realistic study of 300 machine system. And this is the evolution of angles up to two seconds for a fault which occurred at 0.5 seconds which is cleared after some time cleared in the sense the line which the fault was there was stripped out. So, the rest of the system was fault free after that, but because of this disturbance the system was disturbed from the equilibria and starts evolving the transient starts evolving and you see actually several modes here you see a low frequency kind of mode and some high frequency oscillations also. So, you have got a mixture of several relative modes which are seen after this disturbance now the question is will the system lose synchronism or not is something is difficult to say just from what you have seen here. So, let us see how the system eventually evolved actually did a numerical integration of the system and what I see is here is the system breaks into three groups. So, groups of machines and our losing synchronism with another group of machines. So, this kind of thing can cause a complete you know this is a system wide kind of break up of the system and you know well the system is still interconnected, but as I mentioned some time back you may have outer step relays or distance relays actually causing a system separation. And now if each of the islands which are formed after this system separation the load generation balance is not quickly maintained using under frequency relays or by governor action or prime mover action or sometimes even generated trips you may find that each of these islands may collapse and that will cause a system wide blackout. So, these kind of things do occur though rarely it is a nightmare for a system operator if a system a disturbance leads to a system collapse of this kind. So, it starts off with a loss of synchronism then a system separation the system separation causes the islands the islands do not survive and you have got a blackout. So, you have to now start or restore the system from scratch have to re synchronize all the machines. So, that is a extremely intensive and difficult process and sometimes it may take hours if not days you know to get back the system back to normal let us re synchronize and re integrate the grid. So, this occurs rarely, but it can occur it is a nightmare really for a system operator, but for us academicians and students it is a very interesting outcome of the physical equations which govern the system. So, in that sense it is very exciting we do not have time in this course to now look at the power system tools which are used to understand these electro mechanical transients. We have actually done a two machine example and I told you how the equations are, but I really did not tell you the intricate details about how you solve these equations. Of course, you have to apply some numerical integration methods or in case of doing Eigen analysis you have to form the linearized system matrices, but we will spend a bit more time on the topics which are shown on your screen in the next lecture. This is more to do with the power system tools which are used to understand transient stability or even small signal and stability. Remember that simulation as a tool is very general it you can use it to understand fast rather small disturbance as well as large disturbance problems. So, this is what we will do in the next class. So, see you then.


So, how long ago was this when you were going to, when you first started going to his parties, how long ago was that? Well, it's not that I went to his party. You know what I'm saying? I'm just asking you. Okay, let me get on you.  You know what I'm saying? I'm just asking you. But now, what I'm saying is that, this was before Alligator, we talking almost 30 years ago. Yeah, we on Boss Talk 101. Yeah, we gonna talk. That is Pippin' Kid in the building, man. I'm gonna jump right in. C-E-O founder, P-Ditty, is a C-E-O too. Yes, sir. And what I do want to say is allegations keep popping out. You used to be in them parties. You one of the guys that was in them parties, you seen what was going on in them parties. And I just want to know, is it as radical as what people are saying? Well, I never seen that type of stuff. P-Ditty and I had business, right? So I did an album with this artist called Loom. And so over a million copies, it did extremely well. So Loom had gave my information to P-Ditty. P-Ditty called me along with his team. They asked me, what is my publishing company? I said, my publishing company is Kid Ivy Publishing. So we negotiated, I said, hey, but I got one favor I want to ask of you. He said, what's the house I want Loom to come to my party? I want him to perform for my birthday party. That will close until the deal. So that happened. And then about a year later, he called me on six months later. What time was it, huh? What time was it? A year? What time of the day? Well, when he called me, it was like probably, So he wasn't two o'clock in the morning? No. Because he called my boy at two o'clock in the morning at 2.30 and said, No, no, but when he actually had me to come to his party, he wanted me to come to his party. He put it, who was at that party? Jermaine Jopie, everybody in Atlanta. Usher, was Usher at that party? No, no, no, and me and P-Ditty when I came to his party, me and my man Paper Chase was in his VIP. You know what I'm saying? So when we went into his VIP, it was just me and Paper Chase and him and he was battling with Jermaine Jopie on the mic. So I didn't see all that gay stuff and all that stuff. What was Diddy at that time?   Okay, the allegations are that he was doing a little more than just bad boy on the mic. Well, I don't, I never seen it. You know what I'm saying? I mean, that's why I said, you know, I said I can't say for sure. When I met him, he acted like a street nigga.  You know what I'm saying? But let me ask you this question, but don't y'all have some street code or P code or whatever code that even if you did see some stuff, you still wouldn't say it?  You know what I'm saying?   You know what I'm saying? Don't play with me.   You know what I'm saying?  I'm saying, I'm gonna let you know.  So how long ago was this when you were going to, when you first started going to his party, is how long ago was that? Well, it's not that I went to his party, you know what I'm saying? I'm just asking you. Okay, let me get on you.  I'm just asking you. But now, what I'm saying is that, this was before Alligator, we talking almost 30 years ago. No, no, okay, that's the reason why I'm asking you. Some of this stuff gonna come up from 30 years ago. You sure you wasn't in some of them pictures? You weren't in some of them rooms? Hey man, I do have a picture with me and Puffy. You know what I'm saying? Me and Puffy did get in my way. Everybody had this shirt on? No, no. No, but what I'm getting to. No, I'm asking that everybody had this shirt on. Well, I'm looking at these pictures now. It's a lot of shirts off. No, no, no, no, man.  That's what I'm trying to tell you. What I'm trying to add. Oh, God.  I would have whooped the nigga playing with me. You know what I'm saying? Niggas in the joint didn't play with me. I ain't gonna let them nigga on the street play with me. You know what I'm saying? I'm a boss for real. You know what I'm saying?   You know what I'm saying?  You know what I'm saying?  Okay, because I got a question. Because the thing is what I was trying to get to was, okay, because it was a long time ago and back then, you know, and I would think that when celebrities throwing parties and stuff like that, especially if they know that you a pimp or, you know, they invite all of them because y'all bringing the girls. No, you're asking the wrong question. Hold on. The right question is how many bitches did I bring there for them niggas? Hold on, but I'm getting to that. No, no, no. I was providing the bitches. That's what I was getting to, but hold on. That's the niggas. The bitches. But what I'm asking back then was there, was there, was there pimps that had males?  That's what I'm trying to ask. You got a misconception of the pimping. You know what I'm saying? Pimpin' is pimping the horn. Not hornin' horn. You know what I'm saying? Me, it's pimping the horn.  She's gonna be young, fine, and qualified that's really on the pimp side. You dig what I'm saying?    Yeah, I don't. You know what I'm sayin'? Get it right. It's what it might be. It's what it might be. I'm sure somebody pimping now. Hey, I'm the best that didn't get away with it. You know what I'm talkin' about? That's just not me.  But I did 10 years in prison and never looked at a man as a woman.  Definitely is. Let me ask you a question.  You've seen what happened with R. Kelly. You've seen what happened with all these different people. Even Epstein, I think he killed himself when he got in there or they killed him. But allegedly. But what do you see happenin' with Pete Diddy with this case? Well, let me get to, that's the appropriate question, right? Now here's the situation, right? In the African-American community is 3Ds, demonized, destroyed, and discredited when it come to black men. You know what I'm sayin'? I mean, it's been a long, long lasting policy of certain government officials and certain white supremacists to try to bring black men down. You know, that's why when I look at Fannie Willis down there in Atlanta, you know what I'm sayin'?   I guarantee you, they haven't done it to him yet, but Jay-Z, they probably try to get him. They gon' try to get, like they doin' with Aesau Rocky. They already gettin' at him. You know what I'm sayin'? They gettin' at Rihanna. You know what I'm sayin'? And they gon' be gettin' at Beyoncé.  When you look at it from the perspective, whenever you read your history book and say, George Washington was the greatest president all the time and so was Jackson. We got him on a dollar bill and we got him on a $20 bill, but they don't tell you both of them pokes for slaves. You know what I'm sayin'? I mean, they teach you about main arcades. They teach you about Karl Marx. Yeah, they teach you about all these white greats, but they don't, they teach you about Mansa Musa or Kwame Kuma or Charles Drew or Percy Julian, some of the African-American greats. And then when they do, why is Martin Luther King, no disrespect to Martin Luther King, why is Martin Luther King more pronounced and more recognized than Percy Julian? Percy Julian was the first black man on his own medical facility. He also got over a thousand packs with the gluten company. Not only that, you know what I'm sayin'? He protested in Chicago, in Oak Park, Chicago, when they burnt this house down because they wanted him to move. He did the same thing Rosa Park did. He refused to move. He refused to allow the white establishment to bring him down. And nobody ever talked about that, but they talk about Martin Luther King because they killed Martin Luther King. You know what I mean? So in the backdrop of Martin Luther King, you know, all of these streets, all of this stuff that they got in respects to Martin Luther King, the backdrop of that is, you know, it's a European, you know, person that killed Martin Luther King.  So you got to understand, whenever they're lifting a black person up or they're taking the black person and they're giving them all that recognition, he is always a rug that's being pulled up under them because that's what whites look like, making black folks look like they're food.


Thank you very kindly. Mostly I hack on things that don't exist. Sometimes I build things and sometimes they work and sometimes they don't. I haven't got my reading glasses so if I stop and stare at the thing that's because I'm old and terrible. I'm going to talk quite a lot about depression. So if that's going to be a bit painful for you then please look out for yourself. I'm quite happy to talk about bleak things because they happen to me and if that's a bit grim for you. These things happen. Also this clock hates me but... So anyway, a few years ago I was working in Bath and what I was, as Geoff Rowe doesn't say, all the technical team apart from two of us left pretty much in a two month period which was kind of terrifying. And I took to wandering around Bath just to get out of the office and so I could stop thinking about Zen or Redis or PHP or managers that I hated and wanted to die a slow and painful death. So one of the things that Bath has is parades of terrible shop selling terrible things and one of them was a toy shop and in that there were enameled signs for things that didn't exist and didn't have enameled signs and there were wooden toys that you'd give to children and they'd kind of stare at going, well where did the batteries go? And there were tin robots which children weren't allowed to play with because they had lead paint or they were just sharp objects because they were just terrible things and shouldn't have been in a toy shop in the first place. And I kind of wanted one. So I bought tin robot that looked like it was about to have a psychotic break and it was set about anybody or it's all with a welding torch. So allied to this we were doing devopsy things which generally means that you're supposed to have one of these to do your deploys with so that's fine. Yay lots of deploys, yay big red switch, hey! However our deploy rig would have needed this and this was awful but we were kind of working on it and there were only two of us out of a team of seven left and we were going to catch fire and die and in this state I thought the best thing in the world would be to build a robot that would beat around the office and discover who had broken the build and call on the bollocks because obviously public humiliation is a great thing to do for employee wellbeing and to make public humiliation make software better. Everybody knows this. That sarcasm by the way. Public humiliation was why my ex-employer's code was in a terrible state anyway. So A and B came together and I thought sweary bot here we go and I ordered a bunch of bits off the internet because that's what the internet's for and started hacking away and it kind of all went really well and it was great and I think so this is a test rig. Unfortunately there's no sound but what was it nearly mostly worked but it had a strange failure mode where this thing what you can't hear is that it's mumbling to itself in bad speech synthesiser and what it tended to do was just rock back and forth swearing quietly to itself and it would take you know it's beatling about my bathroom it's just attacking the first thing it can find which is my feet and it just won't take piss off an answer so it would just find a dark corner and just hide in it just go bollocks shit bollocks shit and it was at this point I realised I'd built a depressed robot that couldn't cope store that image away for later so the grim thing about this is that there is no happy ending I fell into a particularly nasty depression at this point and never finished it and what's worse is that the bloody computer stopped I posted about it on LJ and many of my friends were like yeah he's very robot brilliant idea that's completely you JHR and I'm like thank you and about 12 months later after I recovered a bit more no it's just not playing is it or rather it's playing but won't stop playing let's see what happens computers right so anyway it was awful I saw all these happy messages about the stuff I hadn't done and it was like awful and made everything worse and reading that sort of thing can really really make you hate yourself because you then were like yeah I can do a thing it's great and you now is like well I fucked that one up and you've let your friends down and you didn't finish the project I mean you never finish a project come on who are you kidding you never finish a damn thing your house is littered with dead projects and the computer works finally and you know you're full of wacky ideas and madcap schemes that never come to fruition if it was a sitcom it would be funny but it wouldn't be funny because sitcoms aren't funny and you let people down you're a loser you shouldn't be allowed to do this sort of thing you just shut up not bother your friends when you're exciting things because they never turn out right just stop don't bother your friends at all be quiet shut up do your work do nothing depression is a right fucking bastard do not listen to it so the good thing is I got better thank you so a few years I mean it was a couple of years ago now I'm trash at the bar having finished a volunteering at a science fiction convention and the best thing in the world slipped into my head which was a cuckoo clock that calls you a twap I mean who on earth wouldn't want one of those so eBay's amazing it turns out there are many cuckoo clocks they come in pink they also come as built I mean this is a German chap's art project and he made cuckoo clocks out of disturbing buildings from I think the ex of Berlin but anyway and about this time I discovered the joy of the SP8266 which is a microcontroller there are about nine punts and they've got something much more grunt than an Arduino but less IO but it was fine and that was just going to be fun but damn things come with Llewer which is horrible I did write a thing here about banging on about favourite toy languages because I can't be doing with Llewer because reasons Pearl drove me up the wall Pearl made me hate myself which is just I'm sure the designers of a language didn't envisage that but it does it was the only thing for a long time and anyway I discovered Ruby because that's all the configuration management stuff was written in and it was night and day and there's I think this notion that a language that fits your head better is less likely to gaslight you and is better for your mental health this is certainly my thoughts on it which are worth whatever you pay to get in nothing, yay but anyway where was that I built a cuckoo clock I built this cuckoo clock now this video will probably also break the same way as the other one but very eventually I'll stuff it we'll get that so while this thing isn't doing its thing there's finally don't worry about the next it doesn't work nail varnish was a wee gold by then so this thing breadboarded up sorry I don't know I'm gesturing at that it's over there everything worked it was great I had a cuckoo clock it called your bastard on the hour boxed it up Vero board soldering and it didn't work and it was just like well you know there's two black wires which are the hour trigger I've got them the wrong way up anybody could do it really turn it upside down it didn't work well getting on a bit I need magnifying hat to see small soldering now because old age it'll be my mangy soldering anybody can do it I'll just stare all the joints and it'll be fine and it didn't work so that demon that thing that tells me I'm rubbish came back and said many things repeatedly along the lines of look here you are again it doesn't work you're a muppet what are you even thinking why are you even trying nobody cares it's just a stupid idea don't just stop you can't you don't know what you're doing and we're here again so the weird thing is about depression that it comes along with imposter syndrome and anxiety and a bunch of other stuff which are rubbish and here's the thing if I put the clock in test mode this is a live demonstration the like of which blue Peter I've never seen if you're of an age to have ever watched blue Peter so an accurate representation of the inside of my head when I'm having a bad time and I can get the sodding USB connection the right way up because hey I forgot my reading glass is so you try and have a conversation with the rest of your head and there's a thing in the back of your head is just interrupting you the whole time you can't think straight you've just got this noise and you're trying to tell people things and it's your voice telling you you're an idiot all the time thank you and everybody likes swearing however where was I? just here so the way I visualise the inside of my head he owes a lot to Unix now okay this is a leak abstraction it's a rubbish idea don't do this at home but thank you one of the things that models I guess is an overloaded system and it's thrashing and half your cognitive function is running in swap and you can't do a damn thing because you're spending all your time trying to shut down out of control demons which are calling you a bastard and your brain is like treacle because you know your half your memory is just thrashing and everything is terrible and so the joke here is that my demons are demons which looks funnier written down as indeed does the ad lib I wrote down so it's not an ad lib but there we are where was I? oh it's over here that's nice so one of the things the demons and I would like to point out that this is nothing to do with schizophrenia symptoms or anything like that it's just I have this model of what's going on in my head and it's shouty eunuchs demons because I'm a spot and what they'll do is get really busy and remind me of some time when I was at a party in 1983 when I made a tat on myself just as I'm overtaking a bus on a windy a road and it's like no you're not killing me that way or they'll decide that a slideshow of my worst moments 1986 to 1995 would be the best thing in the world to show me at about 2am when I'm trying to drop off to sleep the little bastards so here we are imagine if you will a thing which insults you with your own voice exhibit B and at this point weirdly sitting in a cafe in north London eating a salad and drinking tea I have a mug staring out the window I became enlightened I kind of realise that actually what I've been doing is building automata that were external versions of the things that were in my head no, no men in white coats that's okay so this is actually a thing I was chatting to an actual artist I don't think she was wearing a beret and smoking a roll up but and I described this and she was like yeah why do you think you're special? well so I kindly just it all came collapsing on itself and I was like right so I build things to come to terms with the stuff that's going on okay let's store that one away too so I was in Glastonbury the other month you can just about see Glastonbury tour behind the Volvo with the reefer Volvo? yeah, no anyway Glastonbury is great it's filled with good yards X-Railway bits and some shops and a tour which is there and there and there and anyway anyway so the thing the brilliant thing about Glastonbury is that the shop on the high street it's opposite the shop that will sell you homemade faggots and chips for about three quid and it is filled with wooden toys and robot arms and squitty little skittery robots that light up and I wanted to buy one of everything and send it through a time machine to my past self and say it's alright just make all of it break it, paint it green I don't care just do it this is the best thing however time machine is are impossible and my past self would be really freaked out if that happened so I just sent a pile of stuff to my brother's kids and I kept them for myself obviously because who would not wish for a flying unicorn and I realised I bought another automata thing and now I know how this stuff works what is going to come out and I was driving back from Glastonbury up the Twidley Road to Bristol because I live in Bristol and driving to Bristol if I lived somewhere else would be stupid when I realised exactly what I was doing which was that now some none or all of you may have some notion of the significance of the colour scheme or not have I finished? so that happened and I'm not sure yay so if there's a point here it's that bugger depression find ways of explaining it to yourself that might help those are my ways of explaining it to myself and that about covers it I wouldn't actually ask me for any useful information other than if you're having problems with Kubernetes because I know about as much as that as I do about depression so and the question is if anybody's got any questions you're weird but far away I was going to formulate about oh right so we must call I was and this so software and hardware will gaslight the shit out of you and it is really bad for your mental health two examples one, Kubernetes itself the liveness probe if you read the documentation it says as long as your container returns anything between 200 and 399 everything's good Kubernetes loves you and will keep your kit running bullshit so the documentation for this is in a hold on 2015 three-year-old PR on GitHub at the bottom of a lock filing cabinet et cetera et cetera et cetera and I did not find this straight away and I wrote a thing and I stuck it on Ka and it didn't start and it was just complaining because the return code was wrong and it was look it's in the documentation you're supposed to work your fucking blasted thing and I struggled with this for days and I thought I was a complete idiot because I can't work simple containers and the instruction said they should work reality said it didn't well Google are never wrong so clearly I'm the idiot no Google can't write documentation to save their lives it turned out actually that a friend of a friend works for them and I complained mightily on faceache and he was like but Google are never wrong exhibit A exhibit B you sort yourselves out lads the other thing oh yeah we must D1 Pro a ledges to have 16 squillion bytes of memory which you can't use this is hidden at the bottom of a github pier from three years ago in a lockfiling cabinet Mark beware of the leopard and I have one of these and I was building a thing and it wouldn't work and I thought I'd blown it up because I'm an idiot and I can't work electronics and I got a different one and that worked because it was a slightly different version with less memory so anyway everything is terrible beware kit that tries to gaslight you or destroy your brain and that's not a useful behaviour pattern for things that people have made for other people but anyway questions apart from is the bar open and will you shut up is that working? yes thank you for the talk that's lovely the one about demons yes I'm quite old to be a parent and I have some small children and the question was so when can I show my eight year old alien now so monster stories for children I was feeling a bit guilty about this because I thought well I don't know but I met this woman from Mexico who's a good catholic and she said Peter look parenthood is just one long series of guilt trips don't worry right now it turns out it seems monsters in children's stories are a way of externalising things they can't understand now I think if somebody looked on Google which is never wrong they would figure out the citation for that but it's an interesting thought that the externalisation of things is an important step in growth I'd like to pass that comment I fully admit that I'm slow and have to work things out alone and for a lot of this brain stuff because being depressed for part of the time doesn't help because your brain works even slower and hates itself but yeah yeah can we go to the bar now so now you sort of see the process working a bit more does that mean that you can see the automata coming earlier maybe I don't know work in progress I shall find out the next thing I build I don't know what it will be I suspect now I understand what's going on I want to go back and build this way with a robot out of a sense of spite if nothing else because maybe one more question I think really quick one your flying unicorn yes does it do anything that it didn't when it started or does it just have a thematically appropriate colour scheme actually it's got a stepper motor in there which is why the winding handle doesn't work very well but if you use a stepper motor for longer than five minutes it tends to catch fire excellent it is a bonning wing flying unicorn yes it has worryingly enough I got the colours slightly wrong so it's got that vibe of as you say a ground attack strafing people you do not like but I love it to pieces because it's just like it's a complete thing and it worked and I had a whale of a time just because I knew what I was doing and what was in my head it was just like not exactly like that it would be weird I mean that's probably close to Stuart Lee somebody dragged me off stage I don't know can I stop now? yes thank you thank you Jchar


The standard step-in-c, ISO 14649, offers a new model for data transferred between CAD slash CAM systems and CNC machines. It addresses the limitations of the existing G-code standard and opens up new possibilities for its management. At the Department of Automation and Production Systems at the Faculty of Mechanical Engineering, University of Zalina, a project was conducted to explore the implementation of step-in-c format through programming of CNC machines. The results of this research included an analysis of the standard step-in-c, a methodology for converting step-in-c data into express code, and the development of software for transforming step-in-c data into a format compatible with a specific CNC machine controller. The software was tested on a particular CNC machine and successfully demonstrated the viability of implementing the new standard in older models. This article was authored by Nedesta Cubanova and Ivan Kurek. We are article.tv, links in the description below.


In this presentation, we will discuss rules related to fees and commissions for a CPA firm, a public accounting firm engaged in audits and attestation arrangements, attestations agreements. We're going to start off with the contingent fees.  The type of contingent fee that might come to mind is something like a lawyer, for example, who has a contingent fee on the outcome of the case. So their fee possibly being then contingent on the outcome of the case. That would be an example of a contingent fee. Now note the problem with contingent fees is they could compromise our opinion on it, especially if we had a contingent fee, for example, in a similar situation with regards to the audit itself. If we had a contingent fee that basically said it's going to be contingent on the opinion we give, then that would give more pressure for us to give a favorable opinion because then that would be the opinion that would be needed to get the highest fee. So obviously, we don't really want if the good that we are given of the service that we are providing is the trust of the opinion that we're providing. We don't want that opinion to be contingent on a fee or the fee that we'd receive to be contingent on the outcome of the opinion because that's going to give us more pressure to give a favorable opinion and it may look in appearance to be compromising independence. So therefore, whenever you think about these contingent fees, a kind of fee structure that's going to be contingent on some type of future event, I really want to think through that and see how it might compromise the work that is being performed in some way, especially if it's, of course, an opinion type of thing, it could really compromise the work that's being performed. So a member shall not perform for a contingent fee any professional service, notice it says any professional service for or receive such a fee from a client whom the member or the member's firm performs an audit or review of financial statements. So obviously an audit review is less substantial in terms of the opinion and the work that's done in the review, but still an attestation agreement, then we have a a compilation, which is basically compiling the information into the financial statements of a financial statement expected to be used by third party if the compilation report does not disclose the lack of independence. So in that case, we may be able to compile, which is that which is usually not anywhere near significant of the work that's going to be done in an audit, as we compile the information. However, we would have to disclose that there's a lack of independence in that situation and examination of prospective financial information. A member shall also not prepare an original or amended tax return or claim for a tax refund for a contingent fee for any client. So notice this is another area within taxation where we want to really stay away from the contingent fees, because again, you could see how it would compromise the tax preparation process. If we were to say, for example, our fees going to be dependent on the type of refund that you're going to get, or whether you owe taxes or not, that could compromise the tax preparation process. And so we really just want to kind of stay away from that kind of contingent fee in those areas. Now we're going to consider commission and referrals fees starting with commissions prohibited commissions. A member in public practice


S.P.M.Buzz What's up guys, a very warm welcome to S.P.M.Buzz. My good name is Miski Fingi. And today I have a star. Guys, this is Dr. Ezekel Mutoamunamjua. Mimuona kumtandao. I've bumped into him. Nikasema lazima tuongena, Dr. Tari. How are you doing? Very well. This is an appushma. What a lovely afternoon. Good to see you. Good to see you too, Dr. Tari. It's an ambush but you will always have something to tell us so it's okay. Oh yes, I'm always, I always have a story. Yes. So now you know the election period is technically over. How do you feel on how we have conducted ourselves as a country and even the electoral process, how do you feel about it? I think we have come of age as a democracy. That we can do elections even though there is contestation but we do elections, results are announced and the following day we open our shops, we go back to business. It's amazing. We have actually embarrassed the world, ashamed of them who are skeptical and looking forward to some skamishis and it is the extent, they knew they would be, they were always sure. But I think we have behaved in the most mature manner. This election should be not a matter of life and death. We go do our civic duties as civilians, as citizens cast our votes, let IBC count if there is contestation people go to court and seek justice but we shouldn't be drawn into fights, tribal or political and this is what we approved. In fact, I think our behavior in this election will go into record and will be a model, a reference point for the other African continent and even other countries in the world. So I think for me the heroes are the citizens. The heroes are you who is conducting your interviews and you are not afraid that you will be attacked.  Let those who feel aggrieved seek justice and recompense in court but for us as citizens we did our job, we are not the empire and we are not going to be drawn in fights and they are saying never again that message is so emphatic from Kibra to Endorette to Mombasa it is amazing. I watch TV and see those clips from Mondinari Kenyans saying we did our job. In fact, I saw someone who was addressing Baba and saying Baba dupu piki ya kura Baba dupu na kupenda Lakinia 20 yukubara-bara you know I was like say that about everybody that we do our job, finish the elections go back to business. That was very impressive niliwa no aksema piya to see bleed in diowalid. Absolutely. In fact, I really ran that somebody did that and I saw it using my photo and I ran it actually on all my social media and I think the message is emphatic that the people are looking for a job other politicians you and I need to also and survive no you are lucky if a politician pays your rent unless that is a relative chances are that even if they do it they are doing it for our pappas and they are using you ultimately you need to go back to work and do your aso do your interviews do whatever business you do and then continue with your life there is a rent to pay there are school fees to pay for your children for parents they want life to go back to normal it has never happened by the way for a very long time that we do elections say 19 2002 I didn't think 2002 the kibaki euphoria when it was warning but we were also there was still some symbolic tension because we were not sure and those who are with the president they felt really crushed because it was treated badly it was not like the normal competition that has happened this time round people have competed gone into elections cast their votes results were announced of course there was a bit of unfortunate chaos at the bombers but once that was contained here we are and that was done by politicians this time round it is not the citizens all through a chair or through a stone it is politicians the players who are fighting it will kill each other if you want you have used us long enough I think it has never happened before in history so we are the trade blazers as it was in terms of setting the tone for Africa and never again shall we go back to the unfortunate post-election violence of 2007-2008 this was what Kligla and predicted that the next election post-election violence if you are not careful will make 2007-2008 look like a child play you remember they were now saying wazungo wala kwa na sema ni hi wala kwa na sema za sa hi pelikeni cameras cameras wala kwa kila mali all the international media and I remember tweeting and saying let us disappoint them let them send us congratulations which they are doing now the international media is now congratulating the president-elect the international community presidents of other world in the global community and I think what the message that is being sent is that we are moving on we need all beat elections are over and we want to set this to be the example that will be emulated across Africa and across the world and even for us to say 2022 defined who we are now the others were mistakes the others were reactions that were just out of impasse but this time round the true character of Kenyans showing love and rising to the occasion to prove the world wrong resilience and love and compassion and the spirit of peace love and unity has been displayed and I think we are grateful to God we owe it to God that we have the peace that we are enjoying today that we can go on with our business days after the elections Kenyans you are the real heroes every Kenyan was not cast say that last word because of political differences heart their neighbor you are the real hero of this election salute indeed a salute to you now doctori we have ambushed you I know but what is going on here today is it a workshop? music corporation site of Kenya was founded in 1983 next year 2023 will be 40 years we have started the roll out of activities to celebrate music MCSK at 40 will be 40 next year part of those activities include programs to start a music circle a circle for musicians they include activities to start social security fund within SSS I spent the whole day with them here yesterday today we brought in all the different groups of artists representing musicians to start working together in that campaign to ensure that we are programs that will cushion musicians and that is we we go towards MCSK at 40 we will lift the welfare of musicians financially medical cover welfare of their relatives a circle where they can borrow money and invest and using the royalties we collect for them ensure that we cushion them when their financial difficulties we can use their royalties to guarantee them to get loans in the bank so today we end a strategic thinking committee that was meeting here and it includes celebrated musicians we have brought in Dr. Piso as a brand ambassador Mekos Gay infact I was with the daddy here and others just to ensure that celebrities the people have meant Kenya Kenya name out there the flag of Kenya shine outside in the world like Mekos Gay they become part of this and they drive that conversation so by October next year we'll be celebrating MCSK at 40 but it's not just celebrations we hope by then even gala words where musicians are working on with checks of millions out of royalties that we collect so today we are laying in strategy we even starting an app digital app where we are going to applaud all the music for our members the way there is app or music and the people buy the money will be coming directly to our members on M-Pesa we are calling MCSK music and we want to use it exclusive Kenyan music we have over 500,000 songs but our members that were just lying there people like Mdundo Boomplay Mdundo has about 20,000 and they feel they are great we have over 500,000 songs in our custody so we will applaud them so we were planning those activities to ensure that we come up with a roadmap towards MCSK at 40 this was engagement this was just brainstorming and then bringing people from different sectors out of this election this was our first meeting post election to say there is likely to be a new government how do we work with that new government how what are the committees of parliament who are the ministers who are likely to be appointed where are we likely to be placed as an industry so we are also contributing to the narrative of go back to business get the country back to business and then we were also planning and looking at how can the music become a tool and a vehicle for promoting our catch and our values and placing the godliness where it should be our kids don't have to sing Sipangwingwe it's a good song I found myself humming it but it is based on rebellion where kids are saying they don't want to be I know we have let them down but we want a song that actually they are proud of themselves that if I am giving you an advice or a parent in you you see kupanga has been used because of the way we have let them down as parents, as government, as leaders even churches we have let our kid down but we are saying never again just the same way we have always fought elections are not free and fair now we have not fought we want going forward to sing about the glory of Kenya the beauty of Kenya Sipangwingwe packaging and the stuff like that no one in music with the content you got them all fans na se ma nizuri kwa mbe nili kwa na ichukia naka pata zikumoji kwa nyumba na se ma isipangwingwe kwa isheni ya kwa isheni ya kwa isheni ya kwa isheni ya kwa kwa se ma good talent the lyrics kwa kwa ru demon is very popular wasafi nini ni kwa ru gengaliya lyrics kwa permulti macho we don't have to sexualize everything the idea is is it possible to set a tone for music that sells without sexualizing without corrupting morals and still position it to sell position it to have market that is wider than Kenya If you sing Peke Jeng, my sister, who will listen to you? Can you play that with your mum? No. Or with your dad? So you limit your market. But if you sing a song that is promoting values that is general and it has a message that cuts across, it will be listened to many people. I want a song I can play in my car. I can play in a place like this. I can play in the office. I can play in my house. That has a bigger market. Even possibly a song that can be played internationally. You saw Jerusalema challenge. Jerusalema and a lot of Zulu, I think it's Zulu. Most of the words there. But we embraced it. The beauty of music is that you don't even have to understand. Lingala, we sing songs of Kofiolomide and other musicians. We don't understand, but you know when the tune is good. So we are in a place where we want to mend our young people to know that the market is in many people listening. You can get a song that even if it is a secular song that can be played during a wedding in church. You are better off than if you sing Pekajeng and it can only be played among your age group. Watoa kiyakujia Pekajeng wa jwe maniake. Ah, naza mazoa kuchesia wimbote na. Laki na kama ni wimboe na sema tu mamboa kupendana family values, resilience, hard work, teamwork. Watoa kiyakujia kwendoa wa pendane usipigemu kewako and the FGM and the social behavior. You criticize those ones. It will be listened, it will be used. Why do you think some of these musicians cannot be invited in public events? Did you see the bands, the choirs that were singing in bombers? Ah, doctori kwanza apu wa tuwali waka dinali wange kuwa apu. Waka dinali. Uju waka dinali. Na Pekajeng, we are bombers. Urukewa na jamuri deimu kuchesia wimboe so. Na zima wimbo, nao na uumitu wa kungulukuangala. Do you know that song is very deep and nice message? It has no ukora. But kungulukuangala everybody is playing it. They don't have to know the meaning. But the guy says every time you see smoke, there is fire. And he does it, both the lyrics and the tunes, they are so nice that you want to listen to kungulukuangala. So the old thing is market your product, music as product that sells to a global market so that you don't limit yourself to only your age group in the name of rebellion. Music is not about rebellion. Of course it can pass messages to liberate but if you just focus on that without money. So what we are doing as MCSK is to say where is the money. What kind of tunes? What message will give you more market? Wider market within commesa, within East African community internationally so that a song like Jerusalema where we didn't understand some of those words but we were dancing Jerusalema challenge we can do that with Kenyan songs. It's not to say that there is no market for Sipangwengwe. I love it myself. But it's to say can we widen the market make even that song play for a longer period of time. Look at Eric Waenana's song Injiakitukidogo or the one who was singing about her money, Kenya. It was playing even at moments, 20 years later. So that's what we are focusing on. Getting mentorship so people can see messaging how do you craft it to fit societal issues and help to focus on those issues. Music should re-preak our conscience. If I'm a corrupt person, I listen to a song like Injiakitukidogo and you feel ya. It tells you, it teaches you something. If you listen to a song that is talking about resilience and the power of overcoming challenges you relate with it. Relatability. That's what we were discussing with Safara. Safara, yes. Now, Doctoria as we wind up you mentioned Diamond and Diamond came just the other day and performed to headline in a political party and it was a big deal and Kenyans reacted to it saying and our artist worth have been they branded themselves in a way that they can be called to such an event. What are your thoughts about that? It's about branding. When I was appointed to this position there was a story in the nation, the headline was I'll make Kenyan musicians billionaires. I was saying we don't have to invite Diamond. Do you know why we are inviting Diamond? Demand. Young people want Diamond. If you took a mutua there or they demand why he looks successful. He's flying all over. He's in South Africa. He has bought this. He has this. If they see you living well out of music if they see you influencing cost of things, living well, driving good cars living in a good house our kids would want to become musicians but if you are only begging and poor and when you are sick we have to raise money you have not employed anybody you don't contribute to anything you get into drugs and depression nobody wants to emulate you. Why Diamond came was out of demand. You create demand by branding and I've said that even about our sportsmen that you can't just rely on legs you got to look at activities and that's why organizations like MCSK come in to give more value addition that just the talent of singing because we have seen our people 1-1-1-1-1 to wonder kwa matatu kila maali kufa kabisa uta iski etena why? because it didn't look at that the dynamics of longevity and the market target market audience that you want to talk to so we bring that mentorship we give them networks we connect them exposure exposure with other countries with other musicians international musicians co-production there's more to MCSK than just collection and distribution of royalties and I believe maybe you should put in Eric Komondi in there because he was actually very he was actually very vocal about artists now in the Diamond issue telling them about branding there's a cloud chaser Komondi is not a musician he is a comedian he has contributed to the narrative which is good but if you want to really make a real contribution you make it with the artists themselves no one can succeed alone I am here in the sea of music co-production site of Kenya but like you've seen and called other people Kenyan Association of Music Producers Prisk they were all year we spend a whole day here planning because you can't succeed alone I can also do drama for cloud chasing to increase my viewership and whatever but did I achieve what I wanted the whole concept about playing local content is very important using our own artists so what was doing was good is only the approach and I'm saying going forward drama will not work what will work is focusing on issues working with the parliament working with the government working with the industry other stakeholders and ensuring that we have proper policy formulation and implementation that will reflect the future of music as a source of jobs and wealth Thank you so much doctori we are waiting for the execution of those plans a saintisana inshala like they say we are trying as you can see we are new this is my fourth month at MCSK but you can see we are bringing conversations we want music to be at the height of all atu taika wana muziki wana raulia utena tu ntaika wana muziki na jia ya kwaishimu wana muziki na kwa brand na kwa promote na kwa patea conducive environment wakuwe kamaandiamond wana muziki wakenya a invaitiwa pia a kachese kateka shere kuletanzania amainji zangambo na hiyondu tradyotumiaza kufikiya na itafanyeka tuhivo ekiwa wana muziki wataonekana wana ishi maisha mazuri wana ishi meka kateka njami wana mandilia na ofa na wana chiangi a kateka wakuza juwa uchumi Thank you so much doctori a saintisana a saintisana alright guys that was doctori Ezekil Mutua right here Thank you guys for watching if you're an artist I hope you're ready to get into this conversation enjoying MCSK into the plan of making artists billionaires Thank you for watching my name is Miskithinji until next time It's goodbye