Synchronize Three CAT G399s


Thread Starter

Smart Okpanku

I have gone through the posts contained here they are quite informative. I am currently having similar challenge with 3 units of CAT G399 gen and ETSCO (model 1400) Synchronization panel. The three alternators are rated 550kw, 480V, 60Hz. I have the mandate to synchronize the three of them for our operation.

My challenge is: when ever I try to bring in the second gen into the bus, the KVAr meter of the two gens rise up to 500KVAr. The Ammeter readings on both rise as well.

Pls i need information on how to go about this reactive power.
what is the maximum allowable reactive power for an alternator rated 550kw?
I don't have any experience with the exact equipment you are working on, but this may help to point you in the proper direction. If the three gen-sets are all connected to a common bus without any transformer/impedance between them then the problem is likely with the excitation ("AVR") system tuning and/or inputs (specifically, the CT input(s)).

In order to "share" reactive load (that is, to stably participate in the "provision" of reactive power without large reactive load swings) exciter control systems generally have a "droop" mode of operation which must be active and properly configured (tuned) to allow operation of multiple units on a common bus without any transformer/impedance separating them.

Also, many times the excitation systems have CT (Current Transformer) inputs which must be properly "phased."

I suggest you have someone knowledgeable with the type of excitation control system ("AVR") used on the gen-sets at your site come to site to inspect the configuration and the inputs to help with your problem. If the only problem you are experiencing is reactive load swings, then it's likely the governors of the gen-sets are properly configured and it's just the excitation control system(s) which need to be verified and possibly tuned for proper parallel operation. You didn't say if the three generators each are stable when operated individually (it's presumed they are), but, again, there may be some additional configuration or tuning which is required to allow these generators to share reactive load when paralleled together on a common bus.

Best of luck!