Methods for parallelism and synchronism of generator sets

Many companies need to run generator sets in parallel to meet power needs. Jiangsu Haixing Power gave its own understanding and analyzed the issues that enterprises are concerned about from the different methods of generator set parallelism.
Generally, generator parallel methods are divided into two categories: quasi-concurrent method and self-concurrent method. We analyze from their advantages and disadvantages:
A. Advantages of quasi-contemporal method parallelism:
(1) The generator has no impact current when closing;
(2) It has no impact on the power system;
B. Disadvantages of quasi-contemporal method parallelism:
(1) If the parallelism is caused by some reason, the impact current is very large, even twice as large as the three-phase short-circuit current at the end;
(2) When manual parallelism is used, it is not easy for operators to master the advance time of the parallel operation.

A. Advantages of parallelism since the same period:
(1) The operation method is relatively simple and the automation of the closing process is also simple.
(2) In the event of an accident, the switch is closed quickly.
B. Disadvantages of parallelism since the same period:
(1) There is an impact current and it has an impact on the system;
(2) The voltage of the system decreases at the moment of closing.

It should be noted that the following conditions
(1) must be met for parallelism during the quasi-simultaneous period. (2) The voltage phase is consistent. (3) The frequency is equal. (4) The phase sequence is the same.
If these conditions are not met, what consequences will be caused?
1. Voltages vary: The consequence is that after parallelism, reactive circulation between the generator set and the system occurs.
2. Inconsistent voltage phase: the consequence is that a large impact current may be generated, causing the generator to burn, or causing the end to be damaged by huge electrical power.
3. Frequency is different: the consequence is that the beat voltage and beat current will be generated. The torque generated by the active component of this beat current on the generator shaft will cause the generator set to produce mechanical vibration. When the frequency difference is large, the generator sets cannot be synchronized after being incorporated.

In addition, if the synchronous generator does not meet the quasi-simultaneous parallel conditions, we call it a non-simultaneous parallel. What are the dangers of being tied up in different periods?
The parallelism of the generator is a serious accident in a power plant. It has strong destructive power on related equipment such as generator sets and transformers, switches, etc. in series. In severe cases, the generator winding will burn and deform the end. Even if the equipment is not damaged immediately at that time, it may cause serious hidden dangers. As for the entire power system, if a large unit is paralleled in different times, it will have a great impact, which may cause power oscillation between the generator and the system, seriously disrupting the normal operation of the entire system, and even causing collapse.