Switching off lights for 9 mins | Grid Failure? Why & how was it managed then? Simplified Analysis

hello guys this is Vivek here I welcome you all to my channel today in this video I will discuss on this topic called the consequences of certain unloading on power plants as we all know on 5th April 2020 our Honorable Prime Minister made a request to all of us to voluntarily switch off our lights for a duration of nine minutes following this request some concern was shown by various power system engineers and power system operators and they told us that this might result into a possible blackout however as the situation was known beforehand they took various initiative in order to avoid any possible blackout so in this video I will discuss why such concerns were being made and what could have gone wrong if the whole event was unknown to the power system operators and I will also discuss about the measures they took in order to avoid the blackout let’s get started but before we begin make sure you subscribe to our channel if you haven’t already and press the bell icon to receive the notification of every single video I make now in order to understand the consequences of unloading on power plants we need to have overall idea about power plants right in India there are various means by which power generation is done there is coal based thermal power plant there is gas there is nuclear there’s also high hydroelectric power plants as well as the renewable resources but among this the thermal power plant or the coal based thermal power plant is the most important why because it is itself a responsible for meeting more than 50% of the entire demand in our country here you can see this is the coal based thermal power plant this is total thermal you can see it contributes sixty two point eight percent of the total demand out of which fifty four point two percent comes from coal and one point seven percent from lignite and other resources are here as you can see so coal based thermal power plant as you can see is the most important source of power generation in India and also the impact that we were discussing a while ago has more impact on the coal-based thermal power plant hence I will focus on the coal based thermal power plant here now to understand what the consequences or what can go wrong if there is a sudden unloading we have to understand how coal based thermal power plant works in a coal based thermal power plant the two most important raw material is the coal itself and water what is done is that there is a drum something like this called boiler drum as the name says boiler means it is used to boil the water and convert it into steam so coal is burnt inside this drum okay and that is used to boil water now this water that you are seeing is collected through various pipes and with the help of nozzles okay nozzles look something like this so with the help of nozzles it is made to hit the turbine blade so what is the turbine turbine something looks like this like a fan or something okay which has the aerodynamic shape these are blades so it looks something like this so the high-pressure steam that is coming out of the boiler drum is made to hit the turbine blades and this causes the rotation of the turbine now the shaft of the turbine is coupled to a generator causing the rotation of the generator hence generation of electricity so this is the basic principle upon which the coal based thermal power plant works now we need to understand the generator that we are talking about this generator is an AC generator which means it works on the loss of electromagnetic induction right one such law is the Lenz law what does Lenz law says the Lenz law says that the EMF induced in a conductor is such as it opposes the very cause of its own creation now what does that mean here that the less according to Lenz law the EMF generated from the generator will try to stop the cause by which it has been generated okay now what is the cause of generation of the EMF the generation of EMF is because of the rotation of the generator so eventually it will try to stop the generator from rotating so that no EMF is generated so in order to do that let’s see what happens now let me make the picture of entire thing happening so this is our steam and that steam is coming into the turbine this is how indicate turbine turbine is also called expander hence this is the shape it has so it comes to turbine and from turbine the generator is coupled something like this this is a coupler and the generator is coupled here right and the generator is causing generation of electricity now this turbine is let’s say producing a mechanical torque in this direction causing the rotation of the revolt or bow generator system now the generated EMF will try to oppose this and because of that it will generate a counter EMF in this direction which is which you can say a hypothetical torque but it is generated in that direction in opposite direction so this is our mechanical torque essentially and this is our electrical torque in the opposite direction now as both the systems are coupled we can say that both of them are rotating at the same angular velocity which when multiplied to this torque causes torque times angular velocity which is power so this is our electrical power and this is our mechanical power also we can say this is the supplied power P m and P is the demanded power that is whatever the demand is on the generator hence P can be called as the demand power so eventually what is the relation between the supply and the demand well let’s say if the demand is increasing so that means PE will increase increase in PE will result in to increase in electromagnetic torque or the counter mechanical torque this counter mechanical torque is also behaving as the controlling torque right because it is controlling the real mechanical torque so that the whole system remains in a stable position so increase in P means increase in te and if PE is increasing that means the speed of the turbo generator system will reduce because that’s what the generator wants so in order to overcome this effect of deceleration of the whole system more amount of esteem is required so that the Macan Girl Talk overcomes this resistance from the electromagnetic talk and it keeps on rotating the generator hence supplying towards the consumer load so this is how the whole system works now that’s what we discuss till now about the whole thing and we saw everything about the turbo generator system that we need here now what is the problem the problem here comes if let’s say the whole scenario was unknown at 8:55 p.m. let’s say we don’t know that any such thing is happening or the power system operators don’t have any idea what what is there at 8:55 p.m. we are saying that let’s say there is a demand of 100 megawatt ok ideally this is just an example so there is a demand of 100 megawatt and all of a sudden at 9 p.m. we are seeing because we don’t know we are saying that there is a certain demand decrease and now the demand is new demand is 50 megawatt so what is the problem if all this is unknown at 8:55 p.m. what is happening the steam that is being provided to the turbine the controller is providing to the turbine is equivalent to that required 400 megawatt power generation that means whatever the steam is coming out the mechanical power is very high and that mechanical power is equivalent to hundred megawatt now the simple rule that is followed in a power plant is that PM must be equal to P that is whatever the mechanical power or whatever is the supplied power that should be the demand power as well now at 8:55 p.m.

100 megawatt power generation is required so the steam 08:27 - coming out the steam that is given to the turbine is of equivalent to hundred megawatt power generation so that is causing the generator to rotate and generate one hundred megawatt now all of a sudden what we see that there is a decrease in demand so that means there is a decrease in P that is the electrical power demanded now if P decreases as we as we saw that Omega is constant angular velocity is constant therefore the torque electromagnetic torque will also decrease here you can see in this picture the electromagnetic talk that the countering torque is there that will also decrease but the mechanical torque will not decrease why because we are we don’t know that there is a decrease in demand and we are still providing the same steam so eventually what will happen this mechanical torque will be greater than the electrical torque and this is the point of whole problem what will happen the electromagnetic torque will be less than they left than the mechanical torque and because of that the mechanical torque will dominate the whole system and that will cause a certain amount of acceleration certain jerk and certain acceleration in the whole turbogenerator system now acceleration means there is rise in omega ok now why it is problematic let me clear this all as there is a rise in omega as there is rise in omega because of the a certain acceleration of the turbo generator system there will be rise in the centrifugal forces acting upon the generator as well as the turbine must you keep this in mind that this is the increase in angular velocity whereas the increase in centrifugal force is directly proportional to the square of the angular velocity now that means there will be a huge amount of centrifugal force acting on the generator and that will result into the wear and tear of the entire generator system the conductors will be weird and teared the bolts will come out there will be a mechanical damage everywhere and not only that the turbine as I said is set of blades like this so this blades under the effect of this sudden force and certain jerk will bend and break away and you turbine is one of the costliest machine in the entire power system so eventually this turbine will be destroyed the generator will be destroyed and this will not be just with one generator this will be happening with multiple generators at the same time because of the jerk will be felt by every generator and that is why a possibility of blackout remains there okay here is the picture of a whole thermal power plant scheme okay and this is the picture of a turbine here you are seeing this this set is called turbine this is the generator system okay so this there are set of blades here these blades get destroyed because of this certain amount of jerk or centrifugal force acting upon it now there is one more problem not only this another problem that is here is let us say the the whole demand is not that much decreasing and somehow the generator is able to maintain the whole thing and there is no mechanical damage and all so even after that we cannot avoid the possibility of the increase of the angular velocity the angular velocity will increase of course now increase in angular velocity will also result in to increase in frequency why because frequency is directly proportional to or what I can say is the manifestation of the speed of generator it is given by PN s upon 120 in an alternator right so n s is the synchronous speed or generally speaking is it is the speed of the generator so P is the mechanical constant P is called the number of poles so avoiding P you can see that F and NS are directly related so increase in NS which will happen because of the increase in angular velocity will result into increase of frequency now increase of frequency means what will happen there will be increase in the line reactance X is given by 2pi FL so if F increases obviously X will increase Y that is problematic because the maximum power sending capability in transmission line is given by V SVR upon X so now that will sorry this will be just X okay this will be V as V R so V SVR upon X now if x increases that means there will be a reduction in the entire P max that is the maximum power sending capability not only that the 80 current and hysteresis loss that we talk about in a transformer there are yes transformer that we use in distribution in generation so in the transformer there are these two types of losses that is the eddy current and hysteresis loss the eddy current is directly proportional to F square and this is directly proportional to F so this two will also increase which will be seen as the increase in temperature of the transformer hence the transformer may trip under the sudden increase of temperature okay all of these systems are they’re made to just tolerate the whole thing for a certain limit definitely rise of frequency is somewhat acceptable but it should not exceed the maximum of plus minus three percent that is even in the worst case scenario the frequency should not exceed more than three percent of its set value on the either side either decrement or increment Y decrement is also not OK because the decrement in frequency means decrement in the speed and if the speed decreases that means again the supply frequency is decreasing now there are various motors inside the power system or power station itself so that if speed of those motors will also decrease which will result in to further decrease in the power generation and eventually the whole generator will stop under the effect of the electromagnetic torque in that case all the electromagnetic torque will be greater than the mechanical torque hence that the acceleration of the whole system so this is the whole scenario upon which various conclusions were being made the there will also be rise in the voltage on the receiving end side why because there as the load is decreasing that means the load current will also go down and because of that the armature reaction and the line drop will also be low so because of that the receiving end voltage on the transmission line will be also at high now let me show you some graph of the voltage and frequency so this is the frequency and voltage graph that you are seeing as I said there was a rise in frequency as you can see here but what you can find that the frequency rise was maintained in so well manner that it did not exceed the plus minus 3% bar okay you can see here at 9:00 p.m. when everyone switched off their lights that caused the rise in the frequency because of the demand decrease and when after nine minutes everyone turned on their all loads that followed by a decline in the frequency but eventually it touched the 50 Hertz line here you can see this is 50 years okay and as I said there was also a rise in the receiving end voltage because of the mentioned reason but when everyone turned on their lights and all the voltage also dipped down now how this all thing was maintained this is up to now we talked about if the whole thing was unplanned so as the whole scenario was planned these are the actions the puso cool let us know that these were the actions they took so I will describe all these actions so first of all what what they did was they began to cut down the steam supply to the power plant by 8:45 p.m. okay one more thing that you need to keep this in mind that the coal base thermal power plant is not as responsive as other power plants that’s something you can call as the drawback of the coal based thermal power plant what does that mean that it cannot change the supply or demand in in a speedy manner just like all other power plants can do like hydroelectric or renewable resources so it takes time for the coal waste thermal power plant to achieve any of the equilibrium State that’s why the steam cut down was started from 8:45 p.m. eventually that resulted in to decrease in the mechanical power input and as the mechanical power input decreased but at that time keep this in mind that the electromagnetic torque was high why because the demand was not low at that time the demand got low at 9:00 p.m. but they took action and they began to decrease this mechanical power from 8:45 p.m.

now you will ask that if they began to decrease 17:52 - this mechanical power input or the steam input how the demand was met at that time so that was met by increasing the hydroelectric power generation so at that time thing there was an increase in the hydroelectric power generation so they kept on increasing this for 15 minutes so that it doesn’t result into a cutoff for that 15 minute gap okay so that was done at 9:00 p.m. exactly what happened everyone shut down their load and there was a decrease in the demand so because the mechanical power was decreased the coal based thermal power plant was able to absorb the shock and there was no acceleration in the whole system once the whole thing got over after 9 minutes after 9 p.m. after 9 minutes the hydroelectric power generation was continued again and it kept on increasing because as I said the coal based thermal power plant cannot just go to a new set point so quickly so the hydroelectric power generation was still working and the whole base thermal power plant in the coal waste thermal power plant the steam input was increased in a gradual manner it tooks it took around 17 minutes for the coal based thermal power plant to reach to the new set point so it took 15 minutes for the coal based thermal power plant to reach from high supply to low supply and then from low supply to high supply or the normal supply it took another 17 minutes okay so that’s what this said here you can see that the hydro generation across the country was maximized by 2045 hours and generation reduction of seventeen thousand five hundred forty three megawatt between twenty forty five to 2110 matching with demand reduction of thirty one thousand eighty nine megawatt so this was the demand reduction as you can see was achieved with these resources this hydro generation was again let me clear this this hydro generation was again ramped up from eight eight thousand sixteen megawatt to nineteen thousand twelve megawatt so you can see that the hydro generation was ramped up from twenty one ten to twenty seven twenty one twenty seven as I said it took around another seventeen minutes for the whole thing to come to the normal situation okay another thing is that the reduction of total ten thousand nine hundred fifty megawatt generation was achieved through thermal gas and wind generation from twenty forty five to 2110 okay so it was not only thermal power plant but the maximum shear was that of the thermal power plant followed by gas and the wind generation advanced actions such as switching of transmission lines taking reactors in service changing SVC STATCOM HVDC setpoints we were taken prior to the event for keeping voltage and line loadings within permissible limits now there was also a chance that if everyone turned off their entire load so that could that fear was also there because that would result into a sudden spike in the reactive power demand as well once the event gets over as you can see here in this later they have pointed out this this is a letter written by the ministry of power here you can see that in this line that the appeal of Honorable Prime Minister is to voluntarily switch off only the lights from 9 p.m. on fifth appeal there is no call to switch off either streetlights or appliances like TV refrigerator AC in homes okay so why this was said this was said because if you shut down everything there will be an unprecedented decline in the world demand okay and that amount of decline will result in to failure of the coal base thermal power plant and various other power plants even if the whole event is known okay so if the request was made that you should only strictly shut down or turn off the lights that you have in your home not street lights no TV no refrigerator no AC should be turned off there be a minimum amount of load that should be there on the consumer end so that the whole system can remain in stability okay so this fear was also there this doubt was also there that’s why all the reactors is we see these are the things that we use for the reactive power control in the transmission line there is a video that I have made on this whole topic you can watch here in the eye section so these things were active so that they can take actions and control the reactive power of search if any such thing happens but fortunately no such failure was there and everything went on smoothly as they have said in the next line the event was managed smoothly without any untoward in incident while power system parameters were maintained within limits so this was a by the expertise of the people by increasing the hydro generation they also took care of no blackout even before or after the event and also they controlled everything they protected the generator the turbine everything was under control so in this way the whole situation was managed here you can see a data of frequency and the demand as you can see from 20 52 to 21 9 there was a decline in the megawatt generation from the generator but as you can see the frequency has been well maintained from forty nine point seven three Hertz that was at twenty fifty two and this was the time when when everyone turned off their lights at 9:00 p.m. so here you can see there was sudden increase in frequency fifty point zero five then 50 point zero three then suddenly it went to fifty point one six fifty point two one but it was more or less near this 50 Hertz okay so in this way the whole thing was maintained so that’s all for today guys thanks for watching if you have liked this video press the like button let me know in the comment section what do you think about this video what are your suggestion in any queries if you have put them in the comment section below don’t forget to subscribe to our channel and press the bell icon to receive the notification of every single video I make share this video this is Vivek choppy and I will see you next time .