The impact of power system oscillation on electrical relay protection, the answer is relatively simple. To know the results, we have to understand what power system oscillation is.
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The power system oscillation, when it was first contacted, was in the regulations, I don't know why, and then it was gradually deleted, perhaps related to the increasing capacity of the unit. Power system oscillation is actually a large-scale load dumping accident caused by generator tripping, line failure or simultaneous fire extinguishing of multiple boilers, resulting in the collapse of power system frequency. I don't know how everyone's self-operated thermal power plants are, usually the dispatcher has the authority to pull the load, and according to the importance of the external network load, there is a sequence of numbering, what to pull first, what to pull last, to ensure that when the power system oscillation, the frequency of the grid is not collapsed. Of course, primary frequency modulation, secondary frequency modulation, excitation regulator, etc. are used to ensure the safe and stable operation of the power system.
When the power system oscillates, it has an impact on the electromagnetic and mechanical parameters of the grid, including current and voltage. The current and impedance relays in protective relays are subject to interference and influence. When the protection action value is reached, the corresponding relay protection device will act, which will magnify the original accident. Therefore, when we choose relay protection devices, we must integrate malfunction, sensitivity, reliability, etc.
The power system oscillation is divided into synchronous oscillation and subsynchronous oscillation, these two kinds of oscillation are introduced as synchronous or asynchronous oscillation, all of which have the same meaning, the general frequency of synchronous oscillation does not change, and this synchronous oscillation is a frequency drop, but it cannot reach the low frequency level. No matter what kind of power system oscillation occurs, it is required to recover in a very short time, otherwise the power generation output should be reduced, which is what we call load pulling or increasing the power generation output in other places to maintain a stable power system.
Thermal power plants