When I was bring generators on line and adding them to the buss I would adjust the govenor so the speed would just above the buss speed. When the dial approached 12:00 and the lights went out I would pull the breaker closed. The Idea that the breaker would close in synic and the generator would have a small load and the buss would not back feed the generator.
Now my question.
I worked in a new building with three emergency generators. When the power went out all three generators would start. The first one up to speed would close and connect to the unloaded emergency buss. The next one would synic with the buss and the breaker would close. Then the third would synic and close to the buss. After the third generator closed to the buss then the cross tie will close and emergency power is provided to the building.
I am still having a hard time seeing how an unloaded deisel engine can be exactly syniced to two other engines. I mean it has to be perfict. I could understaand if it had a small load, but no load. I watched it one night when the power kept going on and off, so I know it works.
Am I just being out dated here or is there something I am missing.
The generators will all be running at the same speed regardless of load. If you were to manually sync the third generator to the other two in the way you used to, the first two would act as a very temporary load to the third until they matched speeds. At that point they’ll be locked together. If one tries to speed up, the others will be a load and slow it down. If one tries to slow down, the others will speed it up. Obviously a governor that is trying to maintain an engine speed that is way out of whack will cause problems. There’s a limit to how much a generator can be motored, and protection should be in place to prevent exceeding it.
There are now digital governors and digital excitation controls that communicate with each other to minimize the motoring of any given generator set when there’s no load.
OK now I think I see what I was missing. With the old mechanical govenors the reverse current could get to be too high so there had to be a load. But with digital govenors not only could they read the engine speed to a finer level they also could monitor each other to keep the rack adjustments finer.
Next question on new gen sets are they using jerk pumps with a rack set up or are they using a modified rail system, or can they control the injectors electronicly.
I wish I was still around those gen sets to have another look.
A reverse current safety won’t trip on absolutely any current, it’s set to what is safe for that generator. There’s not much current required to keep unloaded gens in sync.
I can’t imagine any modern diesel without EFI. There are engines that can do multiple (I’ve seen 6!) injections of different amounts at different times in one cylinder’s firing cycle to increase fuel efficiency and reduce pollution.