Diesel Generators and Synchronization Problems

Sounds like a governor problem, perhaps caused by the load sharing controller.

If One Alternator trips out on reverse power, and you can establish that the alternator did in fact experience reverse power, IE the alternator motorized, then obviously the on line alternator has assumed the load.

Observe the power factor meter or KVARS meter, the alternator experiencing reverse power will show leading power factor or VARS.

Also notice the frequency of both alternators when the reverse power relay trips. a moderate or large difference between the on line and off line alternators will indicate speed governor control problem. The on line frequency may rise significantly (5 Hz is significant). The off line alternator frequency will likely rise some when taken off line. if the off line alternator frequency drops significantly, check the governor or fuel system.

A really simple to fix problem I have encountered with electronically controlled governors in which the speed is sensed with a magnetic pickup on the flywheel ring gear (IE counting the # of gear teeth passing the pickup), has been small shards of iron likely from starter gear engagement/disengagement collecting on the magnetic pickup and degrading the signal from the pickup (Typically around 7 volts AC, 2-3 Khz).

I suggest that you remove the mag pickup carefully noting exactly how far it is inserted, I have marked the barrel of the pickup, locknut, and bell housing with a marker to be able to return it to exactly the same insertion depth. Or refer to manufacturers recommendations for proper insertion.

If shards of iron are found on the mag pickup clean it thoroughly, this may take some effort as the iron shards will resist removal from the usually quite strong magnet.

The bell housing should be cleaned as best as possible with compressed air and/ or power washer, rags etc, whatever you can get in to the bell housing to remove debris.

Some Caterpillar engines mount the mag pickup on the camshaft gear housing, however they too are not immune to fouling by small iron particles that may circulate in the lube oil (Indicates a more serious issue).

Have you had the oil analyzed for contaminants, could save you a nasty surprise.

Regards CEKM

Hi All,

Thank you very much for the various inputs and insights I received from all of u thus far; These are the answers to the above questions asked by the various participants.

1. Have replaced the Generator 2 governor with Generator 1 governor, problem still remains i.e. the reverse power problem is still encountered.

2. Cleaned up the magnetic pick up of any magentic debris or contaminants, problem doesn't disappear.

3. The fuel is coming from the same tank to both the generators and the fuel is not contaminated

4. Carried out the load test individually on the Gen set, and discovered there is no problem in frequency, voltage or amperage. There is also no Hunting on the generator. Good stability is observed.

5. Tried to swap Load Sharing Module and Synchronizer cards with used cards, problem still persist.

Regards

Minsaram

If you have the original set up procedure in the manual or can get it on line, start from the beginning and set up from scratch. Don't tweak or fiddle, set them up in the same order as the book says. In fifteen years some of the components have probably drifted out of tolerance but not necessarily failed.

I don't think it will be the synchronizer as this is, I believe, only responsible for the initial paralleling of the sets

regards

Chas

Check the AVR, exciter system, PTs, CTs and protection relays. Loss of excitation and metering problems can also cause reverse power trips. The problem could be and probably is intermittent. Been there chased that goose! Got pinched and wing whipped a few times too!

TT3

what if a diesel generator works no-load regarding frequency? it is 60 hz or something like 62 hz? İ also know that a generator will have a slightly higher voltage than nominal while working no-load so why? if it has both AVR and frequency controller it doesnt make sense all right? i dont know reality i just guess pls englihten me..

Hi Minsaram,

Just a thought, Have you checked the fuel itself? If they are running from separate tanks you could have a contamination problem. How about air in fuel?

The fact that you improved the issue by adjusting the governor setting doesn't mean that it is a control system fault, it could be mechanics. Can you run the second gen on its own at full load for a test? that would eliminate fuel /fuel system problems.

regards

Chas

Minisaram,

I too have had these kind of problems that didn't make sense, and spent lots of time chasing intermittent problems.

I suggest that you go to a Refrigeration wholesaler and get what are called "Tattletales", small inexpensive devises available in 24, 120, and 220 volt versions, attach them across the contacts of suspected components, the devices will burn a small wire giving visible indication that the contact has opened, has worked for me in chasing down phantom events.

Also check the tightness of every screw and connection in the system, pull on every wire to ensure connection is tight.

Was on a ship about to depart, Emergency generator would start, then immediately die. Illegal for the ship to depart without a functioning EDG. Chief and 1st assistant were about to begin the procedure to replace and calibrate the digital governor control, a two hour job, tugboats were alongside, Pilot on board.

I persisted in pursuing the KISS approach Keep It Simple Stupid, I opened junction boxes and started pulling wires in one box I pulled on a wire connecting the Mag pickup to the governor, out it came from the crimp ring connector, two other similar improperly crimped connections were found.

We made the departure on time.

Moral, look at the simple things first It ran fine previously right?

Good luck

CEKM