Generator Speed Shift
Generator Speed Shift
(OP)
Hello Friends, I have just joined this helpful site. I am an electronic engineer who is working as Operation and Maintenance Chief at a hospital. There are 2ea Alternators (SDMO-400V/50Hz/1000kVA) that are each driven by Diesel Engines (Cummins KTA50G1, 1500rpm/50Hz) as Emergency Power source for the building. The building's power demand is about 700kW. If any commercial power outage is detected both of the generators comes up and the generator-G1 connects to emergency busbar and first load group swithing to emergency side in 3 seconds. During this time generator-G2 decreases its speed and tries to synchronize to the emergency busbar. After the synchronization (about 30 seconds) period G2's C/B closes and coupling to emergency busbar is achieving. After this point G2 takes about 50% of the load on the busbar and other load groups connecting to emergency busbar sequentially. This is the scenario. Governor Setting is 1500 rpm with 1% droop for G1 and 1540 rpm with %3 droop. There are RG491 modules in each generator's control panels.
And the trouble I have on the Generator Sets is:
While G2 decreasing speed and trying to synchronize to G1, G1's speed begins to increase and after that G2 tries to increase the speed and catch the G1. Is that normal? What I think is G1 should remain at the adjusted speed at least untill G2 connects parallel and load sharing takes place.
Thank you very much for any help.
And the trouble I have on the Generator Sets is:
While G2 decreasing speed and trying to synchronize to G1, G1's speed begins to increase and after that G2 tries to increase the speed and catch the G1. Is that normal? What I think is G1 should remain at the adjusted speed at least untill G2 connects parallel and load sharing takes place.
Thank you very much for any help.






RE: Generator Speed Shift
RE: Generator Speed Shift
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Generator Speed Shift
RE: Generator Speed Shift
The two not paralleled should have no relation to each other.
Does this mean that that one generator running by itself will also incorrectly speed up too?
It should not be dong that in iso or droop mode! I'd say there is a governor or control "problem", not just a "setting" issue.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Generator Speed Shift
RE: Generator Speed Shift
RE: Generator Speed Shift
RE: Generator Speed Shift
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Generator Speed Shift
1- G1:1500rpm, 2%droop and G2:1510rpm, 2%droop
2- G2:1500rpm, 1%droop and G2:1510rpm, 3%droop
The problem was still there for both of the settings.
I could not try isoc operation of G1.
I will focus on RG491 which has certain percent control of the governors. Thanks for advices again, still open for your advices.
RE: Generator Speed Shift
1. There was some bad timing relays in the control panels. I have replaced them.
2. I made this adjustments on the governors : 1515 rpm 2%droop gor G1 and 1530 rpm 2% droop for G2.
3. I have adjust the RG491 cards's freq. pots (these are governors remote pots which has control of 10% of governor speed setting) and power balance pots to middle position.
4. I did simulate a power outage and saw that the G1 connected to busbar as soon as it reached to 90% of rated speed while G2 speeding down. I have decreased the G1's remote speed pot (on RG491) counterclokwise and maintain a steady speed at 50.6Hz. Then waited G2 to synchronize. After synchronization i watched the load balance. I did increase G2's speed from remote pot untill the loads on bots sets are aqual. I have watch the parallel work for 30 mins. During this time i did put and remove some loads on the busbar, the equal load sharing automatically maintained. I turned off both of them and simulate another power outage. Everything was good and satisfactory except the long synchronization time. It takes about 2 mins. It is good for now but later i will work on shorten synchronization time by decreasing G2's governor speed ( this is what i think related with ). Thank again friends.