Q: How many methods are there to parallelize generators, and what are the advantages and disadvantages of each?
A: There are two types of generator parallel methods: quasi-simultaneous method and self-simultaneous method. Their respective advantages and disadvantages are as follows.
Quasi-simultaneous method of parallel advantages:
- no inrush current when the generator is closed.
- there is no impact on the power system.
Disadvantages of quasi-simultaneous parallelization:
- If for some reason non-simultaneous parallel, the inrush current is very large, even twice as large as the three-phase short-circuit current at the end of the machine.
- Â when using manual quasi-simultaneous parallel, parallel operation of the overrun time is not easy to grasp the operating personnel.
The advantages of self-simultaneous parallelization
- The operation method is relatively simple, and the automation of the closing process is also simple.
- In the case of an accident, the closing is rapid.
Disadvantages of self-simultaneous parallelism
There is an inrush current, and there is an impact on the system.
- The voltage of the system decreases at the moment of closing.
What are the conditions for quasi-simultaneous parallelism?
- Equal voltage.
- The voltage phase is the same.
- Equal frequency.
- The same phase sequence.
What are the consequences of not meeting these conditions?
- Voltage is not equal: the consequence is that after the parallelization, there is a circulating current of reactive power between the generator and the system.
- Voltage phase inconsistency: The consequence is that a large inrush current may be generated, which may burn the generator or cause damage to the end by a large electric force.
- Frequency is not equal: The consequence is that it will produce the beat vibration voltage and beat vibration current, the active component of this beat vibration current will produce the torque on the generator shaft, which will cause the generator to produce mechanical vibration. When the difference in frequency is large, even the generator can not be synchronized after integration.