20MW Brush make generator is having Brush make PRISMIC A30 AVR. This AVR is having two channels, one is main and the other is hot standby.

Recently we faced a peculiar problem that the AVR switched to standby chanel from main. Suspected control card may be faulty and replaced the AVR module with a new one. The machine runs smoothly for 12 hrs in main mode and again switched to standby mode.

Checked all the fuses and tightness of wiring. PMG supply value is also getting correct. The machine is running smoothly in standby chanel. What are the things to be checked more or else what may be the reason. whether it is permissible to run the machine in standby mode.

 

On the front of the A30 is a set of LED's on each card. The far right card is the monitor card that should illuminate an LED indicating why the AVR switched from Control to Standby card. Usually a trip over to standy is initiated when a limit is reached and the value continues to exceed the limiter. Common faults are over/under-excitation, over/under voltage.

 

We have 2 turbine no exiciter what is the problem ?

 

what you mean by no exiciter ....
which type of excitation AVR ....