합정국 대통령 각각에서 입장하십니다. 존경하는 로널 레이간미 합정국 대통령 각각 내부. 그리고 동행하신 그 입인 여러분. 본인은 먼저 대한민국 국회를 대표하여 레이간대통령 각하와 영부인 렌시 레이간녀사흐 이번 방안을 진심으로 환영하면 바쁘신 일정 가운데서도 이처럼 세계에 접어든 한미관계 발전의 새로운 기반을 말해야 하는 획기적 계기가 될 것으로 확신하는 바입니다. 이원 여러분 미야 합정국 대통령 각하를.Not long after the war on this peninsula, your president paid a visit to Washington. In his remarks at the state dinner President Eisenhower spoke of the Korean people's courage, stamina and self-sacrifice. He spoke of America's pride in joining with the Korean people to prevent their enslavement by the North. 이 미국의 깊은 인연을 전해오는 것입니다.  Yet the first words from the Kingdom of Chosun to the Emissaries from America were words of welcome and hope. I would like to read part of that greeting to the Americans because it tells much of the Korean people's character. Of what country are you? 10,000개의 여행을 통해 바다와 부산을 바꾸고 또한 다른 곳에 또한 다른 곳에 또한 다른 곳에 또한 다른 곳에 또한 다른 곳에 또한 다른 곳에 또한 다른 곳에 하지만 같은 Tesita jaw 으 unity mn boma inger w Syl said w ז�인 영my ur 완전 w w 용astic so an all contnence among civilized nations World is sadder today because these ancient and honorable practices could not protect the lives of some recent travelers joke 사 array Instead of offering condolences at issued denials instead offering reass reasons it repeated its threads Even in the search for our dead, the Soviet Union barred the way. This behavior chilled the entire world. The people of Korea and the United States shared a special grief and anger. My nation's prayers went out to the Korean families who lost loved ones even as we prayed for our own. May I ask you today to pause for a moment of silence for those who perished. 이 조언을 함께 me in this tribute in which the spirit of our two peoples will be as one. Amen. In recent weeks, our grief deepened. The despicable North Korean attack in Rangoon deprived us of trusted advisors and friends. So many of those who died had one admirers in America, as they studied with us or guided us with their counsel. I personally recall the wisdom and composure of Foreign Minister Lee with whom I met in Washington kil'short months ago to the families and countrymen of all those who were lost America expresses its deep sorrow. We also pledged to work with your government and others in the international community to censure North Korea for its uncivilized behavior. Let every aggressor hear our words because Americans and Koreans speak with one voice. 자가는 개국이 안 되거나, 대한민국의 한국에 임머리가 안 되는 것입니다. 우리가 미국이 최근에는 세븐티브의 사베이징을 한 세계를 유지하고 있습니다. 우리 Marines in Lebanon were murdered by mad men who cannot comprehend words like reason or decency. They seek to destroy not only peace, but those who search for peace. We bear the pain of our losses just as you bear the pain of yours. 우리는 친구를 나누고, 그룹을 나누고. 국가와 국가와 다른 국가의 시대는 그런 의미가 없다는 것을 이해하지 않습니다. 왜 그런 혜택이 필요한지 궁금합니다. 물론, 전혀 쉽게 말할 수 없다는 것입니다. 우리 친구들과 아래와 진실의 정의가 필요할 수 있습니다. 우리는 더 확실하게 지지할 수 있을 것입니다. 그리고 우리가 기억할 수 있는 것은 우리가 상대하는 것들은 앞으로의 흥미를 전달하지 못하는 것입니다. 한국의 과거에 대해 이 더 좋은 점은 한국은 우리의 삶의 경험이 더 좋은 것입니다. 그리고 오늘 제 의견을 그리기 위한 큰 흥미를 그리기 위한 것입니다. 이 흥미를 그리기 위한 것입니다. 사회적 경험과 경험의 도움이 이 녀석의 background of this struggle the great ideological issues of our era were heard would the feature of the region be democratic or totalitarian communism at that time seemed to offer rapid industrialization the notion that the people of the region should govern their own lives seemed to summon impractical and undue luxury but Americans and the people of Korea shared a different vision of the future Then North Korea burst across the border intent on destroying this country. We were a world weary of war but we did not hesitate. The United States as well as other nations of the world came to your aid against the aggression and tens of thousands of Americans gave their lives in defense of freedom. As heavy as this price was, the Korean people paid an even heavier one. Civilian deaths mounted at the hundreds of thousands. President Johnson said before this very assembly, who will ever know how many children starved, how many refugees lie in unmarked graves along the roads south. There is hardly a Korean family which did not lose a loved one in the assault from the north. In 1951 in the midst of the war General Douglas MacArthur addressed a joint session of our Congress. He spoke of you saying the magnificence of the courage and fortitude of the Korean people defies description. As he spoke those words our Congress interrupted him with applause for you and your people. After the war Koreans displayed that same fortitude. Korea faced every conceivable difficulty. Cities were in ruins. Millions were homeless and without jobs. Factories were idle or destroyed. Hunger was widespread. The transportation system was dismembered. And the economy was devastated as a result of all these plagues. And what did the Korean people do?  And today the world speaks of the Korean economic miracle. The progress of the Korean economy is virtually without precedent. With few natural resources other than the intelligence and energy of your people. In one generation you have transformed this country from the devastation of war to the threshold of full development. Per capita income has risen from about $80 in 1961 to more than 20 times $1,700 today. Korea has become an industrial power, a major trading nation and an economic model for developing nations throughout the world. And you have earned the growing respect of the international community. This is recognized in your expanding role as host numerous international events including the 1986 Asian Games and the 1988 Olympics. Now is the years of past. We know our vision was the proper one. North Korea is one of the most repressive societies on earth. It does not prosper. It arms. The rapid progress of your economy and the stagnation of the north has demonstrated perhaps more clearly here than anywhere else the value of a free economic system. Let the world look long and hard at both sides of the 38th parallel and then ask which side enjoys a better life. The other side claims to be the wave of the future. Well if that's true, why do they need barriers, troops and bullets to keep their people in? The tide of history is a freedom tide and communism cannot and will not hold it back. The United States knows what you've accomplished here. In the 25 years following the war America provided almost $5.5 billion in economic aid. Today that amounts to less than 6 months trade between us. That trade is virtually in balance. We are at once Korea's largest market and largest source of supplies. We are a leading source of the investment in technology needed to fuel further development. Korea is our ninth largest trading partner and our trade is growing. Korea's rapid development benefited greatly from the free flow of trade which characterized the 1960s and 1970s. Today in many countries the call for protectionism is raised. I ask Korea to join with the United States in rejecting those protectionist pressures to ensure that the growth you've enjoyed is not endangered by a maze of restrictive practices. And just as we work together toward prosperity, we work toward security. Let me make one thing very plain. You are not alone people of Korea. America is your friend and we are with you. This year marks the 30th anniversary of the Mutual Defense Treaty between the United States and the Republic of Korea. The preamble to that treaty affirms the determination of our two countries to oppose aggression and to strengthen peace in the Pacific. We remain firmly committed to that treaty. We seek peace on the peninsula. And that is why United States soldiers serve side by side with Korean soldiers along your demilitarized zone. They symbolize the United States commitment to your security and the security of the region. The United States will stand resolutely by you just as we stand with our allies in Europe and around the world. In Korea especially, we have learned the painful consequences of weakness. I am fully aware of the threats you face only a few miles from here. North Korea is waging a campaign of intimidation. Their country is on a war footing with some 50 divisions and brigades and 750 combat aircraft. The North has dug tunnels under the demilitarized zone in their preparations for war. They are perched and primed for conflict. They attacked you in Rangoon. And yet in spite of such constant threats from the North, you have progressed. Our most heartfelt wish is that one day the vigil will no longer be needed. America shares your belief that confrontation between North and South is not inevitable. Even as we stand with you to resist aggression from the North, we will work with you to strengthen the peace on the peninsula. Korea today remains the most firmly divided of the states whose divisions stemmed from World War II. Austria and unity was reestablished peacefully 10 years after the war. Germany remains divided, but some of the pain of that division has been eased by the inner German agreement of a decade ago. I know the Korean people also long for reconciliation. We believe that it must be for the people of this peninsula to work toward that reconciliation. And we applaud the efforts you have made to begin a dialogue. For our part, we would, as we have often stressed, be willing to participate in discussions with North Korea in any forum in which the Republic of Korea was equally represented. The essential way forward is through direct discussions between South and North. Americans have watched with a mixture of sadness and joy your campaign to reunite families separated by war. We have followed the stories of sisters torn apart at the moment of their parents' deaths. Of small children swept away in the tides of war. Of people who have grown old not knowing whether their families live or have perished. I've heard about the program that uses television to reunite families that have been torn apart. Today I urge North Korea it is time to participate in this TV reunification program and to allow your people to appear. I would say to them whatever your political differences with the South, what harm can be done by letting the innocent families from North and South know of their loved ones' health and welfare. Full reunification of families and peoples is a most basic human right. Until that day arrives, the United States, like the Republic of Korea, accepts the existing reality of two Korean states and supports steps leading to improved relations among those states and their allies. We have also joined with you over the past two years in proposing measures which have accepted would reduce the risk of miscalculation and the likelihood of violence on the peninsula. The proposals we have made, such as mutual notification and observation of military exercises, are similar to ones negotiated in Europe and observed by NATO and the Warsaw Pact. These proposals are not intended to address fundamental political issues, but simply to make this heavily armed peninsula a safer place. For we must not forget that on the peninsula today there are several times more men under arms and vastly more firepower than in June of 1950. We will continue to support efforts to reduce tensions and the risks of war. I have spoken of the need for vigilance and strength to deter aggression and preserve peace and economic progress, but there is another source of strength and it is well represented in this assembly. The development of democratic political institutions is the surest means to build the national consensus that is the foundation of true security. And the United States realizes how difficult political development is when even as we speak, a shell from the north could destroy this assembly. My nation realizes the complexities of keeping a peace so that the economic miracle continues to increase the standard of living of your people. The U.S. welcomes the goals that you have set for political development and increased respect for human rights, for democratic practices. We welcome President Chun's farsighted plans for a constitutional transfer of power in 1988. Other measures for further development of Korean political life will be equally important and will have our warm support. This will not be a simple process because of the ever-present threat from the north, but I wish to assure you once again of America's unwavering support and the high regard of democratic peoples everywhere as you take the bold and necessary steps toward political development. Over 100 years ago, you asked earlier American travelers to make their wishes known. Well, I come today to you with our answer. Our wish is for peace and prosperity and freedom for an old and valued ally. In Washington several weeks ago, a memorial service was held for those who had perished on Flight 007. During that service, a prayer was read. I would like to read you that prayer because it is a prayer for all mankind. Oh God, look with compassion on the whole human family. Take away the arrogance and hatred which infect our hearts. Break down the walls that separate us. Unite us in bonds of love. And work through our struggle and confusion to accomplish your purposes on earth. That in your good time, all the nations and races may serve you in harmony. That too is our wish and prayer. 안녕히 계십시오. Thank you and God bless you.


One of the interesting things which we were discussing at the end of the lecture the previous lecture was that the rate of you know magnification or increase of the unstable oscillation predicted by Eigen analysis is somewhat different from what is obtained by our simulation. Now, simulation we see a larger rate of change. So, that of course, was not very surprising. In fact, the reason why that probably what was true was because we used Euler method for numerically integrating the equations which tends to show an unstable system to be even more unstable than it actually is. So, that is one of the reasons why the rate of growth in the simulation seem to be much much higher than what we saw in the from the Eigen analysis. Just to you know show you the results again I will do that in a short while from now. So, today's lecture of course, we will continue with our discussion of what this behavior the simulation of the AVR automatic voltage regulator regulated synchronous generator which is connected to an infinite bus, but we will probably have more time and we can now shift in this particular lecture to another topic which is the issue of load models. So, there is another component or you know a class of components which need to be considered which are the loads themselves. So, what we will do now in today's lecture was the new topic of course, would be a load modeling which we should begin with in this particular lecture. We will of course, discuss some of the remnant issues in our discussion of the automatic voltage regulated synchronous generator. Now, to see the results as I mentioned sometime back again I will run a silo program which really displays the behavior which I was talking of. So, what I was telling you in the previous class was the operating point corresponding to the torque being equal to 1 per unit appears to be unstable because the system when given step change in mechanical torque does not seem to be going and settling to an operating point is a growing oscillation. The rate of growth of the oscillation is much higher than that was predicted by Eigen analysis. Remember here we are giving step changes in mechanical torque and in some previous simulations we also saw step changes in the voltage reference of the automatic voltage regulator. Remember that the final operating point to which it has to settle to must be small signal stable in order that the system go and settle to that operating point. This is not what is happening in the case of the operating point corresponding to mechanical torque being 1 per unit. In fact, the operating point corresponding to T m is equal to 0.5 is in fact stable. So you will find that this first disturbance which in which we gave a step change of mechanical torque from 0 to 0.5 was indeed stable the system was kind of settling down to an operating point. But the second disturbance which takes the system to a new operating point is does not settle down because the new operating point is not small signal stable. So, this is what really we were discussing in the previous lecture. So, just to make things even more clear we just look at the same disturbance with change in. So, our first disturbance of mechanical power resulted in the electrical power settling to 0.5 that was the first step change. The second step change taking it to 1 does not seem to settle because the new operating point of electrical torque equal to the mechanical torque equal to 1 is not a stable 1. So, that is what we saw in the previous class. Now, when we did the Eigen analysis we will do the Eigen analysis around the operating point corresponding to this. What we saw then was indeed the system is not small signal stable because the real Eigen value has got a positive real part. The issue we were talking of was of course, that the rate of growth of oscillation of the oscillation as observed in the state variables etcetera was not as was much higher in the simulation than was predicted by Eigen analysis. So, that is one point which we discussed and we attributed that to the numerical method. I encourage you to actually try out other methods like trapezoidal rule etcetera to see how much what is the rate of you know the magnification of the oscillation whether it correlates better with the Eigen values. So, this is something I leave to you as an exercise. There are a few more points which we need to examine. If you look at the plot of power we will just do this again we will have to simulate it because the variables have got cleared. In fact, it is taking a very long time because I have used Euler method with a very small time step. So, this is not the thing to do in real programs. Now, one more thing you notice is that is oscillation not just growing with time. If it was a exponential growing oscillation as was predicted by Eigen analysis we would eventually find that this just blows up in this fashion and goes off to infinity practically. So, this is what our you know your Eigen analysis predicts, but of course, Eigen value analysis remember is of a linearized model it is not valid for large disturbances. So, after a point you know our linearized analysis is not valid in the sense that as the oscillation grows the deviations from the equilibrium become large and it is no longer correct to assume that our oscillation should behave the way it is predicted by Eigen analysis. In fact, what we find actually is it is kind of the oscillation is kind of saturating to a steady oscillation. Now, this is an interesting behavior which cannot be explained by the linearized analysis it is purely a non-linear phenomena and what you see is that this is something which is obtained only by simulation it is something we cannot predict by Eigen analysis. In fact, the origin of this itself is an interesting enough dynamical phenomena. In fact, if you look at the field voltage what we see that the field voltage seems to also oscillate and it is clipped to a certain value why is it clipped because the static excitation system has got limits. So, that is the reason why it is getting clipped. Now, in case I do not have these this clipping action. So, if I remove the limiters in the model in that case what happens now if I do that. So, I will just do that for you what I will do is I will make the limits very very large which in fact practically disables the limits I may instead of 7 times the terminal voltage E f d is limited to 70 times which is of course, a very large value. So, for all practical purposes this excitation system is no longer limited. So, I rerun the simulation without with the excitation system unlimited having unlimited voltage field voltage capability and in that case this is what I get. We will plot the phase angle the angle delta the rotor angle and now you are getting an altogether different behavior. So, if I remove the field voltage limits you are getting altogether different non-linear behavior delta is going on increasing. So, instead of having. So, if you look at what is predicted by Eigen analysis around this equilibrium point is for any disturbance the deviation grow with time and go to infinity this is what small signal analysis predicts. What you got is why the non-linear simulation was with Euler method was a higher rate of growth initially with saturates this is in case exciter limits are model exciter limits are model and in case you assume that excitation system does not have any limits. We find that this movement of delta eventually it becomes a monotonic movement as seen in this figure. In fact, if you expand this this will become very clear. Do you see this? So, what you are seeing is the classical loss of synchronism phenomena. So, what happens is that you get different non-linear behavior depending on the kind of excitation system model you have used. In fact, excitation system model with limit seems to be giving us a sustained oscillation and not just a growth towards the loss of synchronism. This is a classical case of loss of synchronism. Remember loss of synchronism is also a non-linear phenomena it is not something which cannot be predicted by Eigen analysis and it because it is a kind of monotonic increase in the rotor angle after a point it just goes and loses synchronism. So, this is these are interesting non-linear behaviors observed in the synchronous machine. In fact, if a machine is small signal unstable there are two things which will happen you will have a sustained kind of oscillation because and it does not settle down to the equilibrium point or you have got this loss of synchronism phenomena. So, both these things are in fact possible and I will now show you a real life example or real life measurement of small disturbance instability. This was observed on 28th August 2010. What you see in this figure is the frequency of two places two locations which are quite far apart. In fact, one is in Mumbai and the other is Ahmedabad both in the western region of our country. What we see is that the frequency which is a near about 49.9 hertz is in fact not constant you know the out here there seems to be an operating point change and thereafter you see that the frequency at Ahmedabad seems to grow with time and then settles to a sustained oscillation which in fact lasts for more than a few minutes. So, you just see how it is just going on and on. So, this is an example of small disturbance stability which has been observed and if you look at the frequency of swings of these swings it is roughly you know corresponding to one hertz. So, this is in fact a electro mechanical swing which is observable in the frequency measured at Ahmedabad and you see that the frequency does not damp out. In fact, it does damp out, but only after the operating point appears to change. So, it just goes on and somewhere here the operating point changes which is seen by a slight change in the frequency and then this oscillation peters out. So, this is an example of small disturbance oscillations you know of poorly damped small low frequency oscillations of swings and this was actually observed in our Indian grade. So, we will just have a look at it again we will just run through it again. So, these are the frequencies measurement and there is a frequency and finally, the oscillation dies down after a change in operating point. So, you have a sustained oscillation for almost 5 minutes. So, shows that that particular operating point was in fact small disturbance unstable. Of course, if the system tends to lose synchronism or in some cases when you have got sustained oscillation there is a good chance that some relay or predictive relays which are present in the system may pick up. They will see that something abnormal is happening and if it fits in the logical conditions which are given for relay tripping operation they may actually trip out the machine. So, we should of course, take our results is not the full story. In fact, once a system is unstable it is possible that there may be relay operation at some point of time with the responses playing out the unstable responses playing out. So, this is something you should keep in mind. So, the things which you now should remember about our AVR modeling and simulation what are the issues? What is the special issue? We have of course, done the modeling and behavior of the AVR and the special behavior when it becomes unstable under certain circumstances. So, these are the special issues these are not the issues of an automatic voltage regulation system. In fact, if the system is stable and designed well you may find that you will not come across instability that often. In fact, it may happen once in a while for situations which are not envisaged when you are doing your design. But more often your voltage regulator will behave normally and you will have a stable response and you will have good voltage regulation and so on. So, we should not take instability as the thing which always occurs. It occurs under special circumstances. Now, the thing of course is that it does occur sometimes that is something which you should keep in mind. Now, the issues which we have seen in this first part of our lecture today was that there are two kinds of non-linear behavior which may manifest itself themselves and those are will not be predicted by small signal analysis. They are sustained oscillations and the loss of synchronism. Loss of synchronism incidentally can take place under other circumstances as well. If there is a large enough disturbance you may also lose synchronism. We saw the situation in the latter simulation which we did today in which the system lost synchronism because the rotor angle went on increasing with time and after a point it just split from the infinite bus to which it is connected to. Split I mean the system may still be connected, but your rotor angle has become very large and keeps on becoming large and the machine kind of slips against the infinite bus. There is a pole slipping taking place and as I mentioned some time back as you have pole slipping and other unstable responses it is very likely some relays also would trip. So, in that sense our simulation is not really complete. So, we saw loss of synchronism because of small signal instability this also can occur or you can have sustained oscillations this also can occur. Now, one of the other issues which are special to our discussion of automatic voltage regulation system was our definition of q v and angle during transient nothing to do with automatic voltage regulation systems per se, but as we analyze it we did come across definition of reactive power voltage magnitude and angle during transient. So, just to these are important things which you should remember these are definitions it is difficult to assign a physical meaning to voltage magnitude reactive power and phase angle during transient that is difficult to do. So, these are definitions. So, once the definitions which you should remember as voltage magnitude is root of v d square plus v q square this is a definition of voltage magnitude during transient conditions as well reactive power can be defined as this is a reactive power fed into the terminal generator terminals from the generator this is q this something is consistent with our definition of reactive power in steady state. So, it is up to you to prove that our definition of reactive power in steady state confirms to this definition in transient. So, this is an interesting thing which you should try to prove similarly phase angle theta during transient can be defined as v d by v q these are these are all interesting things which are which do not have the difficult to assign physical meaning to them during transient, but they confirm they can be used and confirm to the steady state definitions in steady state. So, in steady state you will indeed find that our intuitive idea of what voltage magnitude of a sinusoid is what is being given by v d square plus v q square the square root of that. Similarly, the this definition confirms to the definition of reactive power in steady state. So, this is something you prove. So, this is also something you should prove. The other special issue which I did not I have not tackled here is that you have other kinds I remember when we discussed our automatic voltage regulation system or the excitation system in general you had basically the excitation system power apparatus then you have got the control system which is essentially the regulator, but the automatic voltage regulation function is not sacrosite you know in case in case any limit of the synchronous generator is hit. Suppose the field current limit of the synchronous machine has been exceeded in the sense that the field current has become too large and it causes excessive heating of the field winding what we would like to do is once this limit is hit we can sacrifice what we need to do of course, is reduce the field voltage. So, what one can do is suppose this is your a v r suppose and this is your static excitation system a simple model which is just a limit. This is the voltage limits at the output of the static excitation system, but on the other hand if a field current limit is exceeded what you need to do is reduce reduce the field voltage to reduce the field voltage we will have to reduce the field the signal given to the AC to DC converter the thyristor converter by the a v r. So, one thing you can do is have a summing block here plus and minus in case so I will just write the logic here in case field current is exceeded override override or modify the order given by the automatic voltage regulator and reduce the field voltage. So, that is the thing you ought to do so I will not spend much time on what logic you can use in fact, you can instead of reducing the field the control order given to the static excitation system you can also instead modify the field voltage reference itself you can reduce the field voltage reference in case the field current limit is exceeded. Remember of course, this is a point of practical concern in a designing a logic is that when the field current is exceeded it exceeds its steady state limit it is not necessarily to necessarily to do anything right away. The thing is that the since the time constants for heating up of the rotor are much higher or larger you can wait for a few seconds it is not going to the machine is not going to get immediately it will not exceed its temperature limits. So, for a short while you can you can in fact, sustain a slightly larger value of field current than the continuous limit. So, in fact for a short while say for few seconds you can in fact, exceed the field current by say 1.2 or 1.3 times the steady state limit there after you can actually start dropping down the current. So, what basically is important is that the temperature of the rotor should not rise the rotor winding should not rise beyond the rate. So, for that you can sustain for a very short while a larger field current than the continuous maximum limit a maximum limit under continuous conditions. So, it we can call it some kind of transient rating of a synchronous machine may be higher than the continuous rating of the synchronous generator. So, your whatever logic which you use in your designing of the excitation control system should use the fact that the system has got higher transient ratings than the steady state rating. So, for short while you can in fact, use the field forcing capability of a synchronous generator to improve the response of a synchronous generator. The other thing which is used in automatic voltage regulation system or rather I should say the excitation control system which also includes the regulation system as one the major component is the stabilizing function. The stabilizing function or the stabilizer is something which does not act in steady state at all. So, those in steady state you should do voltage regulation if some limit is being hit modify the regulation function override it slightly. But both these limiting functions and the regulation functions are to a large extent steady state functions, but if you want to use improve a dynamic response. For example, we saw that for a particular operating point your oscillations were unstable there was small signal unstable predicted by linearized analysis as well to be small signal unstable. In such a case you can modify your basic control system. So, for example, you could this is the automatic voltage regulator is giving EFT. You could for example, put in a modulating signal or an additional signal to modulate the aviar reference in a certain way. So, as to improve your stability. So, what you are doing is take a signal in which this oscillation is observable take some signal for example, the speed power etcetera design a control system design a transfer function appropriate transfer function and modulate the voltage this modulate V ref at this summing point. So, that the oscillation which would possibly grow with time for certain operating points is in fact stable. So, this is in some sense a controller design problem you are designing an additional loop additional stabilizing loop in your system which already exists. So, as to make your system stable. So, this is something you could do of course, the question which may be asked which is very natural is that instead of having this particular loop this particular loop here why cannot we just modify the transfer function here. So, instead of just having k upon 1 plus s t a the thing is that the parameters of the aviar in fact, do affect the you know the response you know the stability of the swing mode. If I change this k this is something I did not actually simulate and show you but this is something you can try to do it try to do it yourself you change the aviar gains or instead of a simple proportional gain you have a proportional gain in addition to a lead lag block. So, if you have got all these things it is possible in fact, for you to modify the stability of various equilibrium points, but normally this is not what is done in fact, you will have this extra stabilizing loop which is provided here. So, you have got something which modulates the v ref and by doing that you try to improve the response. So, let me just put it this way. So, what you are trying to do here just take a minute yeah. This is your system this is your v ref this is your synchronous machine excitation system etcetera. You have got a variable like speed or delta or power in which this oscillation is visible delta is a bit difficult to measure using just local measurements, but speed and power you will certainly see these oscillations along with delta. So, you can take speed as a feedback signal design a controller and modulate this voltage reference itself this is what I really mean this controller is also called a stabilizer because it has no steady state function. So, it in fact should not you know override or interfere with the voltage regulation function too much. So, you will have to limit this another thing is that during steady state it should not affect your voltage regulation function. So, a controller of this kind will always have some high pass filter component which will prevent any output from coming out in steady state condition. So, this is the generic way how people try to stabilize oscillations the other option as I mentioned is do not have this loop, but you play around with the gains of the AVR also the structure of the AVR itself. This is also conceivable, and this is found to be a better way of doing things because you can actually choose variables in which the oscillatory mode is more observable. And therefore, I have you can have a much more effective stabilizer this way. So, this is something of course stabilizers is something we will just do briefly when we understand methods of enhancing system instability. Now, let us just go on to another point we will not really going to stabilizer design at this stage that is the topic of doing other kinds of simulation. Now, we have really done in this particular past couple of lectures two simulations we have done simulations as well as Eigen value analysis of disturbances like step change in V ref. In fact step change in V ref is very much doable you go to a power plant and you go to an excitation system there will be a provision for you to which will allow you to give step changes to an automatic voltage regulator. So, doing this step change is very much possible it is a realistic disturbance which you could do give. In fact, a system operator may wish to change the V ref why is this facility given not just to test, but V ref may be changed by a system operator or plant operator based on the reactive power output which he wants out of a synchronous generator. So, V ref in fact is decided by us if we are operating the power system or a particular generator, but the other disturbance which we consider that step change in mechanical torque is not really very realistic we cannot really give step change in mechanical torque it is not an easy thing to do the prime more systems are much less amenable to this kind of step changes. In fact, to give a step change in torque what conceivable you would have to do is suddenly increase the you know in some sense the steam force on the turbine which is not really feasible, but we nonetheless use that as a disturbance just to show a certain phenomena. So, just we will keep the realistic things in mind a more important disturbance which does occur which we could have tried to simulate using this simulator you know this simulation which we did was simulation of a fault simulation of a disturbance in the form of a fault. So, fault is a short circuit due to loss of insulation the system. So, you could have a transmission line in which the insulation is broken down on some insulator as a result is a flash over between a conductor and a tower and that is a short circuit effectively. So, that is a fault and a fault is usually cleared by protective action by tripping of the faulted line. So, there is a system which actually senses this and trips it out. So, you can in fact so what we did was we studied very benign disturbances in fact some of them unrealistic like a step change in torque. We can in fact give other disturbances for example, we could have model instead of one line two lines and assume that at some point of time there would be a fault here that is v d v q at the terminal of the generator would become 0. And as a result of which some protective relay would act and this line would be out. So, you would need to change your equations. So, whenever there is a sudden disturbance like a fault your equations of the system change. So, your simulation in fact would require you to not change the inputs by like in the case of v ref and t m, but in in case of a fault you would need to change your mathematical equations which describe the system itself. So, if you got a three phase fault for example, you would need to put v d v q equal to 0 for the faulted duration. Once the fault was cleared you would have to write your equations describing the interconnection only one line would be present after clearing of this line. So, you need to modify the equations. So, this something is not very difficult to do you you can try to do it yourself.  So, this something you can try to attempt to do of course, one point you know it is important to raise it at this juncture is that in case you have got an unbalance fault you have got an unbalance fault. There is one problem which you will come across is that your model of the network or interconnection using d q variables may be of less value because when you do the d q transformation of an unbalance system unfortunately you will not get time way invariant differential equations you will have differential equations with vary with time. So, please chew on this you just think over this and contemplate what would happen in case you did have an unbalance system.  You will find that the equations we describe them would suddenly become time variant in the d q frame when you in the new variables. So, this is an important point which you should remember. So, you need to handle this in when you try to simulate practical disturbances because faults most of the times are in fact single phase faults. Single phase faults which are the most common type of faults single line to ground fault and so on. So, when you use d q frame first thing you will of course, have to consider the 0 sequence equations. The second thing is that the d q equations the equations in the d q variables will become time variant. So, when you simulate you will have time variant components in your system. So, let us go now just we have kind of concluded our discussion of automatic voltage regulation systems and excitation systems. Let us just look at where we stand a kind of bird's eye view we have completed the modeling of excitation systems right now. We have also done modeling of synchronous machines and the general analysis general principles for the analysis of dynamical systems. What we need to do in the next couple of lectures or maybe three lectures is the modeling of loads prime viewers and transmission line. These are important components which we should consider in our discussion. Before we move on to a relatively shorter discussion of stability of interconnected systems. In fact, we have studied a bit of this in the simulations which I have shown. I have shown you loss of synchronism small signal instability at certain operating points. These are phenomena which actually occur and I have tried to show them with a very simple system. In when we talk of stability of interconnected power systems later on we will move on from studying just a single machine system to multi machine systems as well. I have already kind of introduced you to how you can make stability analysis tools. You have to make basically you have to numerically integrate the differential equations or do an Eigen value analysis of the linearized systems around equilibrium points. So, these are the basic tools in our armory which we can use to attack this problem. Of course, we will I have already given you a hint of how you could improve the stability say the small signal stability of a system by making improvements or designing or constructing additional loops controller loops in your power system. So, we will discuss this aspect as well later again. Now, one of the things we will move on to today is the modeling of loads. Loads of course, are difficult to model you will appreciate that in a large power system loads. In fact, you cannot talk of an individual load I mean it if for example, if I am studying the Indian power grid the whole you know grid let us say that the southern grid of the system which is a of this country which is a synchronous grid. So, southern grid of our country is a synchronous grid. Now, if I am going to talk of load on the grid we actually have a vast or a huge diversity in the kind of loads which we have. In fact, even if you look at the loads in this studio they are in fact many and varied. In fact, you have got incandescent lamps you have got this computer load then you have got an air conditioner which is right now off because it thumbs a bit and many other loads which I have not mentioned here. So, when you are talking of modeling loads in a system do I have to model everything in anything in detail for example, do I have to model the motor in an air conditioner or do I have to consider every each and every bulk. Now, you will realize that this is will get us nowhere because when you are talking of the dynamics of the complete southern grid which has millions of loads millions of individual loads it will become impossible to do any kind of analysis of the kind I have been mentioning. You cannot really find you will not be able to come up with any useful inferences because the system will become too large to handle you will and even more worse you will not have the data of each and every load loads keep on changing depending on the day weather season and you know and so on. So, it will become an impossible situation to model loads. So, what we really need to do is aggregate loads wherever we can now aggregation by aggregation I mean I will aggregation and not only clubbing together of similar loads, but even modeling them by some gross characteristics we do not really go into very much in detail unless we feel that indeed there is a reason to really model each and every some particular component in detail. For example, if I got a few way a few large motors in the system you know of say several megawatts like our power auxiliary in some cases you may require to model depending on what study you are doing model each and every individual load in the power plant itself. So, that depends on the nature of the study you are doing, but more often than not many loads can in fact be clubbed and we will we have the flag of loads which need to be considered in much more detail. So, most of the loads will be modeled by some general and aggregate method and special loads of course, you will have to flag off and model in detail special large loads. So, that is what we need to do load at a bus the simplest way you can try to model a load is simply by describing how it is real and reactive power the amount of real and reactive power it absorbs as a function of frequency and voltage. So, you know you can just make a algebraic relationship between p and q of the load and the frequency prevalent frequency and voltage and the bus to which it is connected. Now, the best the simplest way you can do it is some kind of simple polynomial or a simple first order polynomial representation for example, p by p 0 is equal to 1 plus k p v into delta v this is a simple representation first it will be valid for practical for small changes in voltage and frequency this is a algebraic representation.  So, what is p 0? So, p by p 0 is the normalized power power at the normalized. So, p is equal to p 0 when delta v and delta f which are the deviations from the normal nominal voltage and frequency take place. So, sorry p is equal to p 0 when delta v and delta f are in fact 0.   So, this is a neat way of writing down the aggregate characteristics of certain loads. So, when you do not have for example, any data it may be a good or rather you do not have very detailed kind of data it may be a good idea to try to fit the characteristics roughly to these algebraic equations. So, this is the you know equations for the loads. Now of course, when you making a aggregation it would be nice to know or whenever you are deciding your these parameters k p v k p f k q f and k q v it would be good to know you know for example, what are the various components of the load I mean I am not saying to the last detail you know, but for example, if I know that at IIT Bombay our loads are mainly lighting and air conditioning loads then I can get a proper roughly from you know other studies which have been carried out by others you can get this you can put in a value of k p f and k q f which fits in well with this kind of load this kind of load mixture. So, for example, it is people have carried out studies and they have found that for air conditioners for example, a window type air conditioners their power factor can be approximately 0.8 0.82 or so. So, these are obtained from certain studies obviously, they will change depending on the rating of the air conditioners and so on and this k p f k p v is for example, for air window air conditioners it has been found in certain studies that 0.47 approximately k q v is approximately 2.5 k p f is roughly 0.5 and k q f is minus 2.8. So, this is one particular load characteristic which you can which you can use you know. So, if there is a lot of air conditioning load or a certain proportion of the load is air conditioners then you can model one chunk of the load in this fashion with the appropriate values of k p v and so on. Similarly, let us just talk about for example, water heater. So, water heater is basically a voltage dependent load it has practically no you know it does not draw reactive power and it is not dependent on frequency you do not expect the heating of the element of any heating kind of load like water heaters to have any thing other than the real power dependence on voltage. So, what you will find is k p v is 2.  So, this is the water heater for example. So, you will find it for this particular class of loads your this is what you will get. Similarly, you have got fluorescent lighting and so on. So, you should in fact you can for example, look into the load modeling chapter of the book by Kundur which I mentioned sometime back and look at the wide variety of loads and their characteristics which are given there. One of the things which probably could be of interest is industrial motor. In an industrial motor in fact has got a certain class of industrial motors has got power factors of 0.88 k p v of 0.07 which is means it is not really voltage dependent k p f which is 2.5 which is fairly good of high frequency dependence and k q v which is 0.5 n k q f which is 1.2. So, you see this fairly large variation in these constants. So, what we need to do is once you have got a load bus it is better to first split it up into various components of loads you know like lighting loads. Lighting means whether you have to really distinguish whether it is primarily incandescent or is it fluorescent then the motors, air conditioners this could be industrial motors, air conditioners and therefore, get a kind of you know describe these individually by the appropriate k p f and k q f and so on and then get a kind of characteristic of the final load and reactive power load which appears on the system actually drawn by the system. So, this is what you need to do sometimes of course, even this when you are doing a large study even this may be very tedious to at this kind of data may be very tedious to get. So, you may find in fact, people kind of classifying loads as residential, commercial there is official office spaces etcetera and industrial usually manufacturing industries etcetera and power plant auxiliaries. So, you can have these load classes and similarly for these load classes we can actually get these k p v and k q v and so on constant. So, if you know for example, Mumbai load is this much of it is residential or domestic this much is commercial. So, you can actually get an aggregate load model for Mumbai as partly commercial partly residential partly industrial and in wherever there are power plants right at that bus you have got power plant auxiliaries remember the steam power plants require substantial amount of auxiliary power you know for their pumps etcetera. So, you will find that that itself may be 5 to 10 percent of the plant output itself the rating of all the auxiliaries. So, that itself is a quite a substantial load that also has got certain characteristics. So, I refer you to the book by Kundur which gives these characteristics in one place you will find that given in one place.  A better way of representing loads would be with a dynamic model, but as I mentioned it would be too difficult first of all to get the data for the dynamic models, but certain loads you know like very large motors you know which may be present in some places you know for them you could flag out these loads in fact, and then model them in detail for example, induction machine loads very large induction machines are there you know several megawatt rating machines are there. So, those machines you may try to flag out and model separately as dynamical equations instead of static equations. So, if you look at induction machines they also come out to become you know the modeling of induction machine may be required in another context not only have you to model large induction motor loads individually using dynamical equations very large I am talking of megawatts whenever you are studying a grid those kind of motors. The other context in which induction motors really or induction machines may manifest themselves is when you are trying to model induction generators. Now, many of the for example, wind farms or wind generators are in fact induction generators and it is a good idea and they are also many very often connected to low voltage system. So, they are almost like negative loads negative induction motors. So, you may actually have to model certain large induction motors as well as large induction generators in your grid individually using differential equations. Now, how do you do that remember we will just not go very much deep into this I will just indicate how we can do it using the synchronous machine equations themselves. Now, just remember that I mentioned sometime back that you can get a simplified model of a synchronous machine using 1.1 model that is 1 winding on the d axis on the rotor and 1 winding on the q axis of the synchronous machine on the rotor. Now, so the equations which you get in fact are given on the screen we have done this in the 22nd and the 23rd lecture and the q axis equations are these. So, these are of course of a synchronous machine. Now, an interesting question to you is which I just kind of hinted in that lecture also was that using the 1.1 model in fact you can get a model of an induction machine as well. How do you get that well you need to make just remember what an induction machine looks like usually it has a round rotor configuration there is no actual distinguish between the d and q axis especially of a squirrel cage machine it is very difficult to define what is the d axis and the q axis if you got a squirrel cage it looks exactly the same in both axis. So, in such a situation what you see is that you cannot have a distinguish distinction between the parameters of the d axis and the q axis another important point which is there is that there is no field voltage applied to a particular winding on the d axis the d axis and the q axis look exactly the same even if you are modeling with two windings the parameter of the winding will look exactly the same. The E F D is 0 because you are not applying any field to the voltage of the field winding the there is no field winding. So, the field winding in fact has to be converted to a damper winding which is short circuited onto itself. So, your E F D has to be made equal to 0. So, if you want to convert the synchronous machine model to an induction machine model then what you need to do is T Q dash T D dash have to be made equal X D dash X Q dash in this 1.1 model have to be made equal and X Q and X D also have to be made equal and E F D has to be set to 0. So, what you will get is a model of an induction machine it is effectively like two damper winding one on the d axis and one on the q axis otherwise the machine looks exactly the same it is no saliency either in transient conditions or in steady state conditions. Of course, it is all very well to say now we have got the model of an induction machine, but typically if you look at induction machine theory etcetera you will get your parameters in terms of the leakage reactance is stator leakage reactance is the stator mutual reactance rather the mutual reactance mutual reactance X M you will also get the rotor leakage reactance referred to the stator X R and from that in fact, you can get the parameters X dash X and T dash which I have just mentioned using these formulae. Now, this is not difficult to prove in fact, you can take the 2.2 model of a synchronous machine set R K and H R H tending to infinity to open the two extra damper windings then you will get 1.1 model you can use the basic equations of the synchronous machine as described in the 11th 12th and the 13th lecture of this course and actually derive these X X dash and T dash. So, this of course as I do to many tedious things which are which we have to derive I leave it to you to derive this. Now, there are some other issues for which we do not have adequate time in this particular lecture we will revisit this in the next lecture. When you say I have converted the synchronous machine model to an induction machine model well what do you mean by rotor angle first thing is a synchronous machine behaves differently from a induction machine. In fact, in steady state the synchronous machine speed is equal to the voltage source to which it is connected. So, rotor the speed is in fact equal to the voltage source to which it is connected a wrote induction machine in fact, does not behave that way except when it is under no load conditions. Rotor angle is is manifest in the torque the question is it manifest in the equations of a induction machine torque the answer is no this something we will discuss in the next next lecture. In a synchronous machine yes you can show that your torque is in some way related to the angle delta, but in an induction machine it is not another thing is we of course will need to most often model induction motors. So, there is some change in convention which we may have to do because we have derived a synchronous machine equations in the generator convention currents going out of the machine the mechanical and electrical torques in certain direction with reference to the rotating direction and so on. So, we have to actually discuss this issue in the next lecture also we will also discuss the mechanical torque and speed dependence this something we will also have to discuss in the next lecture. In the next lecture we will also hint at how using the dynamical tools which we have discussed. So, far there is Eigen analysis and simulation we can actually prove the phenomena of self excitation of induction machines I will just tell you how you can actually try to prove it. So, that is of course something we will do in the next class.


We're here with my co-host today, Stu Miniman. This is the Cube Silicon Angles Continuous Production. We're here two days live at IBM Edge at the Mandalay Bay. This is the second year of Edge. More than doubled from last year we were in Orlando and we've got about 5,000 people here this year. A lot of good buzz, a lot of good technical talk, a lot of good business talk. Good flavor between hardware and software, systems and storage and software and really showcasing sort of IBM's new vision, vision for the future, what they see as this new type of IT, the storage as a platform and Alex Yost is here. He's the Vice President of Business Line Executive within IBM's server business. Alex, welcome to the Cube. Thank you so much for having me here guys, good to see you. Yeah, so what are you doing here at Edge? What are you talking to customers about? What are you hearing? What's the buzz? So clients today are investing in their data centers, but more importantly what they're investing in is their business. So if you went to the main ten session, one of the things you heard about is when we talk to CEOs and CIOs, the importance of IT to customer businesses because what customers are looking for is how do they run their businesses more efficiently and more effectively? How do they use IT to do that? Well the fact of the matter is it's not by putting out server RFPs, it's by running those applications better and so what they're after from us is guys, how do you make our IT more effective for us and for our business and so we're spending a ton of time talking to people about exactly that topic. Yes, okay, so those are some of the factors that are driving IT decisions today. How is that affecting your strategy at IBM? Well the way it affects our strategy at IBM is you heard Tom Rosamillie talk about it. The money that we're spending on innovation is all around helping clients to get the most out of their IT spend. So clients are looking for how do they optimize big data? Well flash technology plays a big role in that. Optimized systems play a big role in that. Customers are coming to us and they're saying we know we have to adopt this or that application set, how do we do that with the staff that we have on board today? Number one, our staff is overworked. Number two, our staff isn't expert yet in doing that. So if we can provide them with recurrent architectures, if we can provide them with systems like an SAP HANA offering that give them the capability to get up and running more quickly then they can devote their IT staff to innovation for their company instead of keeping the lights on. I met with a client not too long ago and they said you know what 70% of our staff is eligible for retirement right now. Well the fact of the matter is when they look at that what they see is holy cats how are we going to innovate if our IT staff is ready to retire? So you said most customers aren't going to build a new data center but the server providers have such a growth pattern that it's almost like they're building a new data center you know every six months or year. So you know how was that discussion going between the enterprise and the service providers and even the cloud solutions and how do you kind of go between those two? Well the MSP market is very vibrant and what we're seeing is that clients are adopting MSP service providers application as a service across their business and it's interesting to see the adoption patterns. We recently had a customer advisory council and I asked the clients you know what is your adoption of cloud service provider content and capability and one guy said well we're not going to be going to a public cloud because our industry is highly regulated and we can't do that. The next guy to talk says because our industry is highly regulated we're adopting a cloud service provider because they're experts in providing applications for our industries and staying compliant in our industry and so what we're seeing is there's a lot of firms that are aware of it and evaluating it they're adopting at a different pace because it's what's relevant to them and to their business. Can you talk a little bit about kind of that transition from kind of the blade system to the pure system, pure flex architecture you know recent industry numbers show that blade server revenues are down in general you know so blade center's been a great workhorse for IBM for many years but it looks like this is really IBM's bet on the next generation architecture and how does that kind of fit to the kind of the cloud models that we were just talking about? Well clients today are looking for more value than just great hardware and so I'm here to tell you that you know the the flex system and pure flex hardware offering is based on over 15 years of innovation and development in the blade server marketplace it has the fastest backplane it's got the most power and cooling it's got the ability for the most memory processors in the industry it's unsurpassed in terms of technology but that's not enough clients are looking for how quickly can I get up and running how do I simplify the management deployment in a cloud environment in a virtualized environment or in a specific application environment and so with pure systems what we're offering to customers is a variety of offerings that give them the ability and whether it's an application as a service or whether it's a platform as a service giving them the capability to specify their operating environment and get up and going very quickly because if we can minimize the amount of time that skilled IT staff spend on the rudimentary tasks of up and running and deployment and management maintenance and get them into innovation customers get value and that's where we think they'll choose us yeah absolutely so Alex we're talking before about you know the labor component talk a little bit more about what customers want to spend their time on we talked a little bit about how they're spending their time today talk a little bit more about that because you said you know it burns one of your customers when they see a senior systems engineer changing it out of disk drive how are they spending their time patching whatever they're doing today and how do they want to spend their time well you're right a lot of the time today is spent on what many customers will say keeping the lights on where they want to spend their time is on innovation the big tasks that IT managers have been given by their executive management are enable mobility enable clients to access us and our business easier and and more quickly enable us to use big data enable us to use technology to differentiate us in the marketplace and so whether it's whether it's oil and gas and and doing exploration whether it's an automobile manufacturer looking to shorten the cycle time to produce or manufacture an automobile or whether it's a retailer looking for better information about their customers they're all looking to use technology to innovate use technology to give them a business advantage they can't do that if they're spending the time keeping the lights on and the data so I met with a customer in the financial industry the other day and that customer told me that when they bring a new application forward they actually monetize the each of those applications and they say this is a five million dollar application this is a four million dollar application and what they mean is our company is going to make five million dollars in profit once we get this thing out the door you know what that's a heck of a lot more job satisfaction than I kept the server farm running today well and then you can quantify the value you're bringing to the organization if you can get it in you know a month earlier you know it starts to get big exactly excellent alright Alex well listen thanks for stopping by the cube and sharing your insights about what customers are doing I really appreciate your time and good seeing you again great to see you guys thank you all right keep it right there everybody will be right back with our next guest we're live from edge this is the cube and we'll be right back after this word.


Thanks to all of you to be with us here on day two. So we're really honored to have Stephen Pinker with us. Many of you are familiar with his work. He's the Johnson Family Professor of Psychology at Harvard. And he's one of our nation's most prominent and interesting and creative public intellectuals. He's written on many different subjects. He's the author of The Language Instinct, How the Mind Works, The Blank Slate. And the book that is really what we'll focus on more here is really a fascinating work called The Better Angels of Our Nature, Why Violence Has Declined. He's, interestingly, the chair of the usage panel of the American Heritage Dictionary. So questions of words and naming means a great deal. And he's been named one of the 100 global thinkers by foreign policy and by Time Magazine as one of the 100 most influential people in the world today. So we're honored to have you with us today. Thank you. And I thought maybe you could begin our conversation with an overview of kind of the general arguments of your book, The Better Angels of Our Nature. The thesis of The Better Angels of Our Nature is that despite the impression that one gets from the headlines, quantitative studies of violence show that it has gone down over the course of history, over multiple scales of time and magnitude. This is true of homicide. This is true of treatment of children. This is true of tribal raiding and feuding. But the numbers that I'll mention this morning, given the themes that the conference have to do with war. And this is largely a trend of the last 70 or so years. Since 1945, if you count the wars and if you count the number of people killed in wars. And this is, by the way, very different from getting your impression of the world by looking at the headlines. Because news is by definition about things that happen, not about things that don't happen. We rarely see Wolf Blitzer on the streets of Angola saying, here I am reporting live from a country that's not at war. Given a world of 7 billion people of almost 200 countries, there's very likely to be a war somewhere. It will always make the headlines. If you only concentrate on the headlines, you'll think the world that nothing has changed. It's only when you count up all of the parts of the world that are not at war and the number of people who die peacefully in their sleep that you can really appreciate the trends. And here's what the trends seem to be. One thing, if you look at the most destructive category of war, and that's war between two countries, especially two big, rich, powerful countries. There has been a quite dramatic decline. There's been no war between any two great powers since the end of the Korean War in 1953. And interstate wars, government against government, have been going down. I don't think there has been one with a standard definition of war as one where there's a conflict where there are at least 1,000 deaths in a year. There hasn't been one since 2003. And then just the number has been gradually petering out. Wars between rich countries. There hasn't been a war between the countries, the top 40 countries in terms of GDP since 1945. Wars in Western Europe. We kind of take it for granted that France and Germany are not gonna fight a war anytime soon. But for most of the course of human history, needless to say that was not the case. Western Europe used to have start two new wars a year for a span of 500 years. As of 1945, that went to zero. And of course, there were no wars between the United States and the Soviet Union, contrary to every expert prediction that World War III was just a matter of time. And then the smaller wars, the civil wars and the wars between less developed countries, those persisted after the decline of war between big rich powerful countries. But those too have been going down in number and in the human toll. If you were to count the number of verified war deaths per capita, the numbers would look something like maybe 300 per 100,000 per year during the worst years of World War II. That went down to about 30 per 100,000 per year during the years of the Korean War, down to the teens during the era of the Vietnam War, the single digits in the 70s and 80s, down to about one for most of this century, sorry, one in the 1990s and less than one in the 21st century. Now there's been a small uptick in the number of wars and the rate of deaths in war over the last three years because of the Syrians of a war and the wars in the aftermath of the Arab Spring. But even that has raised the rate from about two tenths of a war death per 100,000 people to about 0.8 tenths of a war, sorry, eight tenths of a war death per 100,000 per year. So it is a quadrupling, but it's quadrupling from a really, really tiny number to a number that's only a little bit worse. It's wiped out about a dozen years of progress, taking us back to about 2002, 2003, but nowhere near the levels of the 60s, 70s and 80s. So that's the empirical datum that among others I try to explain in the better angels of our nature and it's one that is underappreciated if you go by the headlines. I see my book as part of a general trend to try to move people away from basing their assessment of the state of the world on subjective impressions and intuition and more towards data and numbers. We've all seen revolutions in areas like sports with moneyball in political forecasting with 538 as opposed to a seat of the pants punditry and I'd like to see more of that in our analysis of war and peace and in violence more generally. So this gets us to the title of this panel which is why is violent conflict decreasing in the long term? So you've given us compelling data that we've seen these decreases specifically in war, but underlying that has to be some justification, some understanding of the reasons why these numbers have gone down. Yeah, and I'm under no illusions about human nature.  On the other hand, stranger things have happened over the course of human history. All the great ancient empires used to practice human sacrifice, throwing virgins into volcanoes to placate angry gods, they managed to get rid of that even though human nature presumably didn't change and burning heretics and capital punishment for shoplifting and debtor's prisons and all kinds of barbaric customs eventually declined and eventually disappeared. And so I think of the decline of war as something that's not necessarily permanent by any means, but it does seem to be a real development and we ought to try to understand what was behind it. What is it about human nature that allows both aggressive forces like revenge and dominance to do battle with some of our more peaceable inclinations like self-control, like rationality, like empathy and so on. So if you try to see what's gone right in the last 70 years, lots has gone wrong, but something's gone right. We actually heard a number of them from General Ogierno earlier this morning when he made a number of statements about the overall conduct of war that I think would have been quite extraordinary a hundred years ago. Like the purpose of the military is to prevent wars, like our prime objective is to prevent provocation, miscalculation, escalation. There's a general increasing norm that war is not just the continuation of policy by other means, it's not the natural state of affairs. It's an abnormal situation to be avoided and I think that is a historical change. There's more of a valuation of human life and less of a valuation of national honor, glory, status, dominance and so on as a primary aim. There are more tangible changes in norms that I think have helped implement that. There's, since 1945, there's been an understanding that more or less, the world is divided into states. States are immortal, boundaries are sacrosanct. Now, that's not 100% true, but it is surprisingly true. No member state of the United Nations has gone out of existence through conquest since 1945. That's an extraordinary in world history when states were just wiped off the map or swallowed up at the drop of a hat. Very few national boundaries have been moved around by force and the exceptions are instructive like the Falklands, like Kuwait in 1990, like Israel in the Six-Day War where the conquests are contested to this day. Granted, there have been some pushing at the boundaries like Crimea is a disturbing example, but by and large, the lines that were on the map in 1945 are still on the map. There have been states that have fragmented. There have been decolonization, but the colonial borders then got kind of grandfathered international borders and very few of them have been moved around by force quantitatively, if you count. So that's a second set of norms, just what you do or don't do if you are a member of the respectable club of nation states, which the United Nations kind of sanctified. Then there are structural factors that I think each, at least statistically, pushed the world, reduced the likelihood, although they don't reduce it to zero. Economic development, probably the best predictor of civil wars is just rock bottom poverty and once a country rises to a couple of thousand dollars equivalent per capita GDP, the chances of it hosting a civil war plummet. So as the world gets richer, it has fewer wars. Global institutions like the United Nations and other regional coalitions seem statistically to lower the likelihood of war. International trade and investment, when countries find it cheaper to buy things than to steal them, then they're less likely to indulge in conquest. And it's often been said the United States and China, despite the rivalry are probably not gonna go to war because they make all our stuff, we owe them too much money, so it would be economic suicide on both sides. And democracy has at least a statistical effect in reducing the chance of war. All things being equal, two democracies are much less likely to go to war than a democracy and an autocracy or two autocracies. And so the rising tide of democratization has brought with it a slight lowering of the risk of war. So those are the explanations that have been on the table and I think all of them have some degree of validity. So one of the most interesting things about your book is it's not really about war per se, it's about violence. It sort of offers a comprehensive theory in a way of violence and its steady reduction over long periods of time. So do you see, and you speak about domestic violence and crime and other forms of violence, is there any type of violence that you think in the near or long-term future poses a particular threat that might increase in some profound or destabilizing way? Well, there's a lot of, needs to say a lot of unpredictability. There are no cycles, that is I don't think that statistical studies of war's over the course of history, so there's an enormous amount of randomness. There are unknown unknowns, things come out of the blue, but it is not the case that if we'd gone for a long period of time without a big war, then we're due for one. History doesn't work that way. It's random rather than cyclical. I think there's certain categories that could continue to go down. I think the violent crime, homicide and rape and assault have been sputtering downward and the old idea that you'll never get rid of them or even reduce them until you solve major problems like poverty and racism and inequality have turned out not to be true, that when a country decides, let's just try to reduce the crime rate, they generally succeed. And even some of the most violent cities in the world like Bogota and the Favellos of Rio and Russia after the collapse of the Soviet Union where it looked like violence was going to be permanent, the rates of homicide have come juttering down. The other categories though that are much less predictable.  But when it of course comes to civil wars, all you need is a bunch of young men and weapons which are pretty easy to procure and they can call themselves the popular front for the liberation of whatever and you could have a civil war. So it's gonna be much harder for the world to see an end to civil war compared to interstate war. Terrorism is always tempting because it's a way of leveraging a very small amount of violence into a very large amount of attention. The global toll of terrorism is outside of war zones. It's actually quite trivial for, but it is almost by definition a media magnet. And so anyone with a grievance can use a little bit of terrorism to inject themselves on the world stage. So I don't think we're gonna see an end to that any time soon. And then there are other question marks. We don't know what climate change is going to do to violence. I don't think it is a given that as the world gets drier, hotter, perhaps even hungrier that it's necessarily gonna lead to an increase in war. It's a widespread assumption, although the statistical studies don't back it up. So I think overall, absent big, ugly, nasty surprises which can always happen, but the systematic trends I think are toward a more peaceful war together with bad surprises. So let me ask you a question about how you came to this topic. And if you could recount maybe some particular moment or some realization that drew you to the significance of this declining engagement with violence, maybe the visit to the Torture Museum and one of the other episodes that you either speak about in your book or maybe have not spoken about publicly. Yeah, I came to it from a general interest in human nature. I believe there is such a thing. I don't believe that we're particularly nice species. But on the other hand, in encountering fears that a study of human nature leads to fatalism or pessimism or reactionary politics, like why try to make the world a better place if people are just rotten to the core if we've got violent genes or a violent brain and people will just louse it up no matter what you do. And I pointed out that human nature, for many years, human nature is complex that even though we do have motives that can result in violence, like revenge and dominance, human nature also accommodates other motives that can push back against violence. Abraham Lincoln called them the better angels of our nature and that was a lovely poetic term that I co-opted for the book title. But it refers to the fact that the brain also has systems like empathy, like self-control, like reason, like social norms, that depending on the circumstances can repress the parts of human nature that militate toward violence and war. And it's a question of which of those components of human nature get engaged at a particular time and place. So the train of events that led to this book were was pointing out actually on a blog posting. My literary agent has a intellectual website called EDGE and every year he asks a question and a hundred or so scientists and other writers sort of speculate on the question. One of the questions, what are you optimistic about? And I pointed at a number of facts that I was aware of such as that a lot of barbaric practices got abolished over the course of history like chattel slavery, like public torture executions, like debtor's prisons, and that the rate of homicide whenever it's been quantified by historians over a continuous time series shows a downward trend. Then after it was posted I got correspondence from scholars in fields that I barely knew existed saying that there's much more evidence for historical declines in violence than I had even mentioned in this post. In particularly the war nerds, the people who try to quantify how many wars have taken place and how many people get killed in them year by year, sent me their data saying this is the way the curves look. There's a lot of randomness, there are ups and downs but there's an unmistakable downward trend.  There's both a trend that few people are aware of because people get their oppression of the world from headlines rather than data. And this is a big fat, juicy, psychological problem. Namely, how could this be possible given that human nature could not possibly have changed that quickly? What is it in the various components of the brain that both allow us to be highly violent but when things go right we can repress those violent instincts? So this is the perfect place to open up the floor for questions from the audience. Right there in the center please. Hi, thanks, Simone Garrow with Control Risks. I first became acquainted with your work in a previous life when I was working at the Bill and Melinda Gates Foundation who, and Bill Gates is a huge fan of yours and would always push his team to read your work all the time. So thank you for that. But to bring it back, this is very optimistic and great to hear, but to bring it back perhaps on a more pessimistic note, is there anything that's going on in the world right now or trends that you see that worry you will keep you up at night? Oh yes, well certainly what's happening in Eastern Ukraine represents a real probing of the norm against conquest, against territory changing hands by force. Granted, it's highly limited. There Putin has sent in little green men rather than tank battalions. So it's not like Saddam Hussein in Kuwait. But still, this is pushing against a norm that has probably done a lot to keep the peace, that just you don't, if you're a country you've got some members of your own ethnic group in another country, you don't put on the table the possibility of annexing that chunk of territory. So it's worrisome that that norm is being challenged. Certainly the possibility of the worst case scenarios like nuclear terrorism and again the low probability high impact scenarios of possible nuclear war, even if it's regional. Even though I don't think it's particularly likely, I think the damage would be so catastrophic that we've got to think about those cases. And of course the influence of jihadism, of violent political Islam. Of the ongoing wars now, as of 2014, there were 11 wars in the world, which is a pretty low number historically. A couple of decades ago it was in the 30s. Of the 11, seven of them involve violent Islamist forces. So clearly the jihadism, Salafism, is continuing to be a big problem. Hi, Peter Singer from New America. Your work was recently referenced in a meeting that Ian Wallace and myself had with a senior government official related to cyber security. And they talked about how you had pointed out how there's all these trends going in a positive direction except in the space of cyber. And he was asking us of how do we make it like that? How do we make cyber threats look the same way as what's played out in, we would say, personal crime violence and also overall violence? And then a second part of this, one that's almost like a policy recommendation question, but related is that perhaps also an explainer for at least some of the things that we're seeing that is it is far more effective for me to non-violently steal the money from hundreds of people, or thousands or millions, rather than bash you across the head and take the money out of your wallet. I'd rather have a hundred million credit cards or the like. How do you both explain cyber security within this phenomena, but then second, what would be your recommendation to make cyber security follow the same patterns and trends? Well, I think there are problems and then there are really, really, really big problems.  Climate change is a really, really, really big problem. So I think of cyber security as a problem. I think if our nerds are smarter than their nerds and if we make it a priority to make systems more resilient and more secure, it'll be more of a nuisance than a global threat. Whereas nuclear terrorism is something keeps me up much more at night. If credit card records get stolen, that's a bad thing, but it's not in the same magnitude as say a nuclear terrorism or a big war between two countries, say a escalation in Ukraine. I don't think it's very likely, but I think it's a much more serious thing to worry about. And I, for, yeah, I'll do it at that. Can we get a mic over here to Tom? Great. Hi, Tom Ricks. I wanna ask you about the medical argument that the reason fewer people are dying in war is most people used to dying in war because of disease. And it's the elimination of disease rather than a decline in violence that has led to declining numbers of dead in warfare. Yeah, it's true that in many wars in the past, there was the number of people dying from disease was greater than the number of people blown up. But that can't account for the trends that we've seen because for one thing, effectiveness of medical treatment works on percentages and the wars vary along orders of magnitude, number of zeros, as opposed to percentage points. And so there's no comparison between say, World War II on the one hand, Vietnam and Iraq, all of which involve different number of zeros compared to the medical care available in World War II Vietnam and Iraq. If you back project the most sophisticated medical care of the current wars and say, well, what if we had them during World War II? World War II would still be off the charts. For one reason, because so many people were incinerated, nuked, starved, so that medical care was kind of beside the point when you have that sheer number of people vaporized or incinerated. And even in the best of circumstances, medical care can only operate at the margins. The percentage of people who would have lived even without medical care, you take away the people who would have died even with the best medical care. It's only the percentage in the middle that can be pushed around by medical care. If you've got 10 or 100 or 1,000 or 10,000 as many people affected in a war zone to begin with, that drives the numbers much more than the percentage in that intermediate zone that can be saved now, but couldn't have been saved in the past. Hi there, Anna Mulvarn with the Christian Science Monitor. The US military has a big deal moment on its horizon in January of 2015. It's gonna lift its combat exclusion policy for women. And so that could in turn lead to more women on the front lines of combat as they've been already. And it's traditionally also been a passport to leadership within the Pentagon. So we can imagine a day where more women are gonna be in those leadership positions. So I'm just curious about your reflections on how women might impact the future of violent conflict and warfare as they become more involved. It's a good question. And in general, the empowerment of women pushes against violence. Not that women can't or don't lead countries in wars or commit acts of violence themselves, but of the different categories of violence, I don't think violence is a single thing, and in Better Angels I distinguish a number of categories of violence. But there's some categories that are definitely a guy thing. We have the expression a pissing contest, and it's not a coincidence that one of the two genders is better equipped to compete by reasons of anatomy. I think it's a good metaphor that when it comes to stupid conflicts over honor, prestige, dominance, revenge, a lot of data suggest that that's more of a guy thing than a woman thing. Now again, when it comes to more practical uses of violence, that is, you're attacked, you have no choice, but to fight back, you're playing a chess game, and violence, and at least the threat of violence is to your advantage. I don't think there's a big, or if any, difference between the sexes.  And in general, public opinion polling tends to show that even though there's a lot of variance between countries in terms of sympathy for hawkish policies between men and women, so in one country you might have more hawkish women than you have hawkish men in another country. Within a given country there's almost always a gender gap and where men are more hawkish than women by a certain number of percentage points. Big enough so that the, for example, the both elections of George W. Bush would have been reversed if only women had had the vote. And women in American elections are favored, the more dovish candidate in election after election. Again, it's not an all or none difference, but it's enough of a statistical difference that as women have a bigger voice, I think that nibbles away at the probability of war. So we're out of time. Thank you so much. Let's all join together and thank Professor Pickerford. Thank you.