Stop Rostov NPP. Hot on the heels of the accident
On November 4 of this year, the news about the stopping of the Rostov NPP has stirred up the entire world community. The Internet began to boil over with headlines like “Accident at the Rostov NPP”, “Two power units of the Rostov NPP stopped in an emergency”. The ignorant people, especially those who live nearby, immediately began to build conjectures. The word “accident” + the word “NPP” has recently been associated with radiation pollution.
In this case, the information management of the Rostov NPP competently and quickly worked out. They reported that the shutdown of power units was caused by problems in the electrical part of the system and the background radiation was normal. Such things as raising the level of pollution in our time are no longer concealed, since it is no longer the USSR and any citizen with a dosimeter can write on the tweeter to raise the background. Therefore, such statements of official services should be trusted. But nevertheless, what happened in this electrical part, what caused the “dumping” of two blocks and the widespread large-scale disconnection of consumers of the united power grid of the South (UES of the South)?
Let's try, having some data, to make out this large-scale failure step by step. This will help me to discuss on the portal of professional relaymen rzia.ru and some data from the operational and sensitive personnel of the power system.
We have the following wording of a specialist: “When outputting a 500kV South overhead line, there is an erroneous overlap of electrical equipment on equipment that is under voltage. The section with connections of 500kV disconnects from the DZSh. There is a sharp load shedding. At the same time, the AL-500kV Florovskaya-Volzhskaya HPP is disconnected from the ALAR. Thus, the IES of the South will be separated from the Center (system), it will become isolated and there will be a widespread reduction in the frequency and operation of the AChR. I can add that according to the results of the analysis, the frequency decreased to 48.2 Hz. With subsequent recovery in 23 seconds. ”
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How it was? Version.
November 4 ... 5 hours 23 minutes. The operating personnel of the Rostov NPP allegedly removes the Yuzhnaya 500 kV overhead line for repair , for this purpose, on-site 500 kV switchgear (500 kV open switchgear), operational switching is carried out.
When one of the switches is turned on (presumably B-50 according to the scheme) 500kV, voltage is applied to the grounding blades. A short circuit occurs. It occurred presumably in the area between the switch B-50 and B-51, that is, one of the three grounding knives was turned on: -50, -51 or . And then the bill went on milliseconds ...
After 76 milliseconds, the B-50 switch is disconnected from the protections and the short circuit action is terminated. And it would seem that the personnel error was eliminated by the successful operation of the protections, and the station and the power system should continue to work ... But no! Simultaneously, the busbar protection 4 of the 500 kV section - differential tire protection (DZSh) - starts up and runs. From it all further troubles begin.
This protection should only be triggered from a short circuit only on the 500 kV busbars themselves, but not elsewhere (this is protection with absolute selectivity). But the defense was launched (it is now the most intense moment of the investigation), and there is no way back. She began to disconnect all 500 kV outgoing lines connected to the 4th section of the 500 kV outdoor switchgear.
The station in a split second lost the load. Naturally, having lost the load, the steel generators will accelerate, because there is no load, and the power at the turbine remains the same. But the generator can not be accelerated! First, the desync begins, i.e. the generator voltage vector begins to “overtake” the voltage vector of the power system, and secondly, mechanical destruction of turbine elements, or generator, may occur.
Therefore, AROL automatic equipment immediately turned off one generator, and then the second one. And naturally, it is assumed that the special automatics of the reactors “muffled” them a little, but this all happened according to the rules of work in this situation. In such cases, ARBKZ automatic equipment sometimes works (automatic unloading in case of close short circuits), but it is not often used, and it seems that it was not at RostAES.
In the meantime, such things happened in the ECO South energy system.
Ode_ug
Morning in the UES of the South began with a power surplus, that is, generation was more than consumption. So, the power flows went from the IES of the South to the neighboring power systems. This is normal. And here at one moment 2000 MW of power “disappears” from the power system, that is, it is the capacity of the Rostov NPP. There is a sharp unbalance of active power, which leads to a decrease in frequency in the power system to 48.2 Hz. At the most inopportune moment, ALAR automatics disconnects the 500 kV Frolovskaya-Volzhskaya HPP line. This leads to the separation of the ECO South from the ECO Center, and the ECO South begins to work in isolation. Emergency automatic emergency response system starts working, which shuts down consumers, saving the power system from complete collapse. After 23 seconds, the frequency in the power system is restored, that is, it comes back to the level of 50 Hz. In parallel with the decrease in frequency, there is a voltage drop on the buses of substations 330-220 kV, and the SAON automation works.
At this time, the dispatchers of the ODE of the South begin to take urgent action to restore the normal mode. By 10 o'clock most of the lines had already been turned on, and the connection of the IES of the South with the IES of the Center was restored. All this time at the Rostov NPP there have been works on the commissioning of the power units. And by 4 pm, power unit No. 2 was switched on. The power unit No. 1 came to normal operation only on November 6. You can make the assumption that the reactor unit number 1 is greatly unloaded, and it took time to withdraw it from the "iodine well". How the VVER-1000 reactor is removed from the “iodine pit”, and why one of the reactors reached the operating parameter faster, you can read here .
What do we have in the bottom line?
1) The root cause of everything that happened is an erroneous voltage supply to the grounded part of the electrical installation. If this is a mistake in the form of switching (the program), then the one who compiled and signed the form (program) will be guilty. If this operation was added by the operating personnel of the NPP during the switchings (according to local conditions), then most of the blame will be on it. Plus, most likely, there was such a violation as the release of the EMB. Operational interlocking should not have allowed to turn on the switch when the grounding knives are on. However, not everything is unambiguous here: often the EMB logic does not allow performing the operations provided for by the form, and the operating personnel displays it by making an entry in the release log, or in the operational log.
2) The operational staff was wrong, this is indisputable. But the development and scale of this accident was due to the excessive action of relay protection - DZSh. It was this protection that “separated” the NPP from the power system and created the prerequisites for further disconnection of the generators, the operation of emergency control automation, and the separation of the power system. Now the “war” begins, and the operating personnel begins to look for any excuses in the “jambs of installers”, in the contacts of the test blocks ... And this is correct, you need to look for the cause.
3) In the current situation, it can be said that the operating personnel of the power system coped with such a “harsh introductory” rather quickly and did not let the OES of the South collapse to the end. There is one quotation from a specialist, which is very relevant here: “For planned switchings in the darkness, I would have been driving the full dispatch services in full force to stations and substations for such night switchings. And so they themselves wore OPU-ORU-OPU. Mistakes of staff on the night shift, and even at the end of the shift, are most likely. "
4) The current situation should be analyzed by the power system re-regulators, because a situation has occurred that could happen again. And you need to be ready for the "fallout" of two blocks at the same time. The regime's regime will also benefit from assessing this situation, because in the UES of Belarus 2 NPP power units will have an even greater “weight” than the 2 NPP units in the OES of the South. So there is a good chance to learn from the mistakes of others, and to provide for such a regime. There is confidence that the Belarusian energy sector will take everything into account.
Reference:
What transformations are waiting for the ECO in the future?
In the IES of South, the balance of power in the period 2013–2014 is formed with a deficit of a regulatory power reserve of about 370.1 - 626, 9 MW, which can be covered from the IES Center and the IES of the Middle Volga. In the following 2015–2019, the development of ECO South power plants will ensure the region’s capacity needs.
In the UES of South, the increase in electric power production at nuclear power plants for the period 2015-2019. 15.3 billion kWh (from 19.8% in 2012 to 29.7% in 2019). The share of TPPs will decrease from 56.2% in 2012 to 49.4% in 2019, with an increase in the absolute value of TPP output from 44.7 billion kWh to 51.6 billion kWh
In this case, the information management of the Rostov NPP competently and quickly worked out. They reported that the shutdown of power units was caused by problems in the electrical part of the system and the background radiation was normal. Such things as raising the level of pollution in our time are no longer concealed, since it is no longer the USSR and any citizen with a dosimeter can write on the tweeter to raise the background. Therefore, such statements of official services should be trusted. But nevertheless, what happened in this electrical part, what caused the “dumping” of two blocks and the widespread large-scale disconnection of consumers of the united power grid of the South (UES of the South)?
Let's try, having some data, to make out this large-scale failure step by step. This will help me to discuss on the portal of professional relaymen rzia.ru and some data from the operational and sensitive personnel of the power system.
We have the following wording of a specialist: “When outputting a 500kV South overhead line, there is an erroneous overlap of electrical equipment on equipment that is under voltage. The section with connections of 500kV disconnects from the DZSh. There is a sharp load shedding. At the same time, the AL-500kV Florovskaya-Volzhskaya HPP is disconnected from the ALAR. Thus, the IES of the South will be separated from the Center (system), it will become isolated and there will be a widespread reduction in the frequency and operation of the AChR. I can add that according to the results of the analysis, the frequency decreased to 48.2 Hz. With subsequent recovery in 23 seconds. ”
')
How it was? Version.
November 4 ... 5 hours 23 minutes. The operating personnel of the Rostov NPP allegedly removes the Yuzhnaya 500 kV overhead line for repair , for this purpose, on-site 500 kV switchgear (500 kV open switchgear), operational switching is carried out.
When one of the switches is turned on (presumably B-50 according to the scheme) 500kV, voltage is applied to the grounding blades. A short circuit occurs. It occurred presumably in the area between the switch B-50 and B-51, that is, one of the three grounding knives was turned on: -50, -51 or . And then the bill went on milliseconds ...
After 76 milliseconds, the B-50 switch is disconnected from the protections and the short circuit action is terminated. And it would seem that the personnel error was eliminated by the successful operation of the protections, and the station and the power system should continue to work ... But no! Simultaneously, the busbar protection 4 of the 500 kV section - differential tire protection (DZSh) - starts up and runs. From it all further troubles begin.
This protection should only be triggered from a short circuit only on the 500 kV busbars themselves, but not elsewhere (this is protection with absolute selectivity). But the defense was launched (it is now the most intense moment of the investigation), and there is no way back. She began to disconnect all 500 kV outgoing lines connected to the 4th section of the 500 kV outdoor switchgear.
The station in a split second lost the load. Naturally, having lost the load, the steel generators will accelerate, because there is no load, and the power at the turbine remains the same. But the generator can not be accelerated! First, the desync begins, i.e. the generator voltage vector begins to “overtake” the voltage vector of the power system, and secondly, mechanical destruction of turbine elements, or generator, may occur.
Therefore, AROL automatic equipment immediately turned off one generator, and then the second one. And naturally, it is assumed that the special automatics of the reactors “muffled” them a little, but this all happened according to the rules of work in this situation. In such cases, ARBKZ automatic equipment sometimes works (automatic unloading in case of close short circuits), but it is not often used, and it seems that it was not at RostAES.
In the meantime, such things happened in the ECO South energy system.
Ode_ug
Morning in the UES of the South began with a power surplus, that is, generation was more than consumption. So, the power flows went from the IES of the South to the neighboring power systems. This is normal. And here at one moment 2000 MW of power “disappears” from the power system, that is, it is the capacity of the Rostov NPP. There is a sharp unbalance of active power, which leads to a decrease in frequency in the power system to 48.2 Hz. At the most inopportune moment, ALAR automatics disconnects the 500 kV Frolovskaya-Volzhskaya HPP line. This leads to the separation of the ECO South from the ECO Center, and the ECO South begins to work in isolation. Emergency automatic emergency response system starts working, which shuts down consumers, saving the power system from complete collapse. After 23 seconds, the frequency in the power system is restored, that is, it comes back to the level of 50 Hz. In parallel with the decrease in frequency, there is a voltage drop on the buses of substations 330-220 kV, and the SAON automation works.
What do we have in the bottom line?
1) The root cause of everything that happened is an erroneous voltage supply to the grounded part of the electrical installation. If this is a mistake in the form of switching (the program), then the one who compiled and signed the form (program) will be guilty. If this operation was added by the operating personnel of the NPP during the switchings (according to local conditions), then most of the blame will be on it. Plus, most likely, there was such a violation as the release of the EMB. Operational interlocking should not have allowed to turn on the switch when the grounding knives are on. However, not everything is unambiguous here: often the EMB logic does not allow performing the operations provided for by the form, and the operating personnel displays it by making an entry in the release log, or in the operational log.
2) The operational staff was wrong, this is indisputable. But the development and scale of this accident was due to the excessive action of relay protection - DZSh. It was this protection that “separated” the NPP from the power system and created the prerequisites for further disconnection of the generators, the operation of emergency control automation, and the separation of the power system. Now the “war” begins, and the operating personnel begins to look for any excuses in the “jambs of installers”, in the contacts of the test blocks ... And this is correct, you need to look for the cause.
3) In the current situation, it can be said that the operating personnel of the power system coped with such a “harsh introductory” rather quickly and did not let the OES of the South collapse to the end. There is one quotation from a specialist, which is very relevant here: “For planned switchings in the darkness, I would have been driving the full dispatch services in full force to stations and substations for such night switchings. And so they themselves wore OPU-ORU-OPU. Mistakes of staff on the night shift, and even at the end of the shift, are most likely. "
4) The current situation should be analyzed by the power system re-regulators, because a situation has occurred that could happen again. And you need to be ready for the "fallout" of two blocks at the same time. The regime's regime will also benefit from assessing this situation, because in the UES of Belarus 2 NPP power units will have an even greater “weight” than the 2 NPP units in the OES of the South. So there is a good chance to learn from the mistakes of others, and to provide for such a regime. There is confidence that the Belarusian energy sector will take everything into account.
Reference:
What transformations are waiting for the ECO in the future?
In the IES of South, the balance of power in the period 2013–2014 is formed with a deficit of a regulatory power reserve of about 370.1 - 626, 9 MW, which can be covered from the IES Center and the IES of the Middle Volga. In the following 2015–2019, the development of ECO South power plants will ensure the region’s capacity needs.
In the UES of South, the increase in electric power production at nuclear power plants for the period 2015-2019. 15.3 billion kWh (from 19.8% in 2012 to 29.7% in 2019). The share of TPPs will decrease from 56.2% in 2012 to 49.4% in 2019, with an increase in the absolute value of TPP output from 44.7 billion kWh to 51.6 billion kWh
Source: https://habr.com/ru/post/362881/
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