Generator Asynchronous Parallel Operation

When a generator is paralleled asynchronously, a huge current impact is generated in the generator stator, the stator ammeter swings violently, the stator voltmeter also swings accordingly, the generator vibrates violently, and makes a roaring sound, the rhythm of which is the same as the swing of the meters.

1.Handling of Generator Asynchronous Parallel Operation

The asynchronous parallel operation of the generator should be correctly judged and handled according to the accident phenomenon. When the synchronization conditions are not significantly different, the generator has no strong vibration and roaring sound, and the meter swing can quickly subside, there is no need to shut down, and the unit will soon be pulled into synchronization by the system and enter a stable operation state. If the asynchronous parallel operation causes a great impact on the generator and causes strong vibration, and the meter swings without attenuation, the unit should be immediately disconnected and shut down. The unit can be restarted and paralleled only after the test and inspection confirm that the unit is not damaged.

2.Causes of Asynchronous Grid Connection

1) Unequal voltage

2) Inconsistent voltage phase

3) Unequal frequency

4) Failure of the synchronizing device during automatic quasi-synchronization parallel operation

5) Operators did not operate according to the operation ticket during automatic quasi-synchronization parallel operation

6) Operators did not operate according to the operation ticket during manual grid connection

7) Synchronous meter failure during manual quasi-synchronization grid connection.

8) The generator phase sequence check and phase verification were not carried out before the newly installed or overhauled unit was put into operation, and the secondary circuit of the relevant voltage transformer was not phase verified after maintenance.

9) The indication of relevant meters is incorrect.

3.Hazards of Asynchronous Parallel Operation

During asynchronous parallel operation, due to the large closing inrush current, the huge inrush current causes a serious impact on the generator, transformer and the system. The unit will vibrate strongly, causing the stator winding of the generator to be deformed, twisted, insulation broken, stator winding connector melted, and even the winding burned. Even if it is not damaged at that time, it will cause serious hidden dangers. As for the entire power system, if a large unit is paralleled asynchronously, the generator will oscillate in power with the system, seriously disrupting the normal operation of the entire system, and even causing the collapse of the entire power system.

4.Prevention of Asynchronous Parallel Operation

1) Check the condition of the meters before the unit is connected to the grid, and compare multiple meters during the grid connection process to judge the correctness;

2) Must strictly operate according to the operation ticket, and the supervisor must supervise in place;

3) Phase sequence check and phase verification must be carried out before the newly installed or overhauled unit is put into operation, and phase verification must be carried out after the maintenance of the secondary circuit of the relevant voltage transformer;

4) The automatic synchronizing device must be in good condition

5) Before grid connection, the generator must be confirmed to be in hot standby status, and the generator outlet switch and PT must be manually moved to the working position.

6) Operators should be familiar with the primary system and secondary system of the factory

7) Do not close the switch when the synchronous meter pointer stops at zero or has pointed to zero. Before the generator to be paralleled is connected to the system, reaching synchronization with the system is only temporary. If the synchronous meter stops at zero, it may be caused by disconnection in the meter or other reasons, and the switch cannot be closed

8) When the synchronous meter pointer moves to zero too fast, it indicates that the frequency difference between the generator to be paralleled and the system is too large, and it is difficult to master the closing operation time of the circuit breaker, which is easy to cause asynchrony, so closing is not allowed.

9) When the synchronous meter pointer is unstable and jumps when passing the zero position, it may be because the internal contacts of the synchronous relay are stuck, so closing is not allowed.

Guangxi Dingbo Generator Set Manufacturing Co.,Ltd. was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to [email protected] we will pay highly attention on your question.