Current abnormal increase on paralleling generator with DECS200 regul 1

[toudom]

I'm commissioning installation of a DECS200 regulator on a 380Vac rated vapor turbine driven generator. When trying to parallel the generators, current outrushed to abnormal level (over 6kA on a 4345A nominal generator) but it's voltage seemed to stagnate to the setpoint (400). I'm in VAR mode. Another generator is already on the bus. The online gen's active power didn't vary but the current of the bus incomming generator goes to 6 000 A. What would be the explanation to that current outrush of the generator ? Your answers would be very helpful.

See attached parameters for the DECS200.

Toudom

 

[glendale]

It sounds like the voltage droop characteristic of the AVR is incorrect. The AVR droop setting should provide a falling voltage characteristic for increasing lagging reactive power. If the droop CT is either in the wrong phase or wrong polarity the AVR output will increase instead of decrease when lagging reactive power is produced. The effect is dramatic and very quick resulting in a high level of reactive power flowing between paralled machines.
Check the AVR CT and voltage sensing is as per the manufacturers schematic.

 

[toudom]

Thank you glendale.
Of course CT wrong phase and wrong polarity were detected. This change was made before and was not reported.
CT had to be wired on B phase but it was wired on phase A. That caused a false calculation of real power that was negative. The wrong polarity caused the increase of reactive power flowing across the two generators. The two problems were solved.

Thanks,
Toudom

 

[oldfieldguy]

toudom-

You make me feel good. Your subsequent explanation described what I was expecting.

Good luck in the future. You've just had a valuable bit of experience.

old field guy