Why Does Generator Not Reach Set Reverse Power Level During Parallel Operation

Thanks , further I checked individual generator with 170KW,both was fine , it is notice that when i reduce RPM from defected generator its just decrease RPM and the governor motor keep in rotating when I reducing but RPM does not chain, same parallel condition when I increase rpm from other generator defected one remain in -16kw and both generator RPM was noted increasing (monitor fro RPM gauge ).when individual both generator RPM was Reduce up to 47HZ and found its effective.how doe fuel flow to governor is effecting during parallel operation.give me some more details to trouble shoot my problem

It almost sounds as if you are trying to get the reverse power to go higher (up to the trip level) when you should be trying to get it back to zero.

It is important to note that increasing the torque applied to the good unit (#1), ie increasing its RPM, is actually increasing its share of the load, this is because the generator RPM is constricted by the frequency of the bus (the other machine) - this would be 1500RPM for a 4 pole 50Hz device, so the extra torque is converted to extra amps to the load, and #2 becomes part of that load. Increasing the RPM of the 1st generator when the 2nd is motoring is surely going to increase motoring and so (if #1 torque increase is large enough) will increase the RPM of the 2nd prime mover - they will attempt to keep in step RPM wise due to the common bus connection and common frequency, but I would have expected the reverse power reading to also climb.

Reducing the frequency to 47Hz was likely effective because the 2nd generator is not reaching correct frequency - so when you reduce the 1st RPM it brings them both into sync and the 2nd stops motoring.

If #2 prime mover is not producing enough torque to keep it spinning freely (ie at synchronous speed), its speed will be forced to increase to that of the bus, the generator will motor, and reverse power will be the result.

Fuel flow affects the RPM of the prime mover, which directly affects the synchronisation of the two generators, if they are out of sync then one generator will motor, the degree of motoring/reverse power will depend on the degree of disparity.

I would suggest that you disconnect the offending generator and then re-synchronise it to the bus with the synchroscope reading slightly high before you reconnect.

Make sure your synchroscope is connected correctly otherwise the readings may be reversed, if using a synchronising relay - again make sure the connections are not reversed, and ensure that it is not closing the circuit until full synchronisation has occurred ie positive slip in the setting. If positive slip is not available on your setup then you need to arrange for the motor governor to call for more power when the breaker is first closed.

Have you checked the connections to the CTs to determine if they are correct and sending the correct signals? - DO NOT open circuit the CT secondaries whilst any current is flowing through the core primaries.

If the prime mover is not maintaining speed under load, then you should investigate that.

"....the governor motor keep in rotating...", there's your first clue, if the governor motor doesn't stop rotating it means it can't find/adjust its setpoint, you may find that the linkage between the motor and the fuel valve/regulating mechanism is damaged/disconnected.

Second thing to try is raising the output on the slower machine and seeing if it takes on load and the faster machine gives it up. If not then your droop mechanisms are either set improperly (if at all) and/or malfunctioning.

You should be glad that you can't push more than 16kW into that diesel, that's still a lot of reverse torque (the direction of rotation is still the same) going into a mechanism that's supposed to produce torque, not absorb it for prolonged periods.

If you're the ETO then you better get the MTO involved really soon before you destroy his engine. Where is the Chief Engineer through all this, on shore duty??

Caterpillar. Reading the name correctly might help in reading the manual correctly.

Although I have heard within the discussion of the power to the prime mover and changes in that, I have heard nothing about the normal equipment for paralleling two generators. Generators frequently do not like to share load and which ever is the strongest takes as much load as it can and the weaker may even act as a load. This may occur even when nothing is wrong with a generator or prime mover. If that is the case either generator can operate up to it's power capability if operated separately. That does not mean they will parallel. To operate in Parallel, the prime movers must have special circuitry to make them apply the same percentage of HP to each generator and the exciters for the generator must be tied together with paralleling circuitry that will prevent circulating current which is what is occurring here. Most large commercial or marine generators either have this circuitry or can have it added. That does not mean that it is hooked up correctly. I have seen many cases of the exciter paralleling connected exactly backwards. This means that one generator will take the load while the other will loaf or motor until either one reaches a limit that was not intended to exist.

When I was first in college, with no EE courses yet, I took a summer job at a service station 45 miles from anything in Nevada. As I got to daily working pumping gas and washing car windows, I noted that the owner was having problems keeping his generators running and asked if I could help. He put me to routine tasks such as checking fuel supply, oil, maintenance and turning on and off generators as the load changed. Realize that this was a conglomeration of Diesel and Propane powered generators purchased for one reason alone, that the price was the cheapest available. The owner was savvy as far as engines (prime mover) was concerned, so they all ran well and all were fully capable of producing power. We lived out in the desert in trailers and the routine was at closing time, we would back off to one generator with just enough power to run a few lights, refrigerators and freezers, and a swamp cooler for each trailer. During the day we would reconfigure the electrical system to divide up the load so each generator could operate independently. This was crude and actually involved moving wires. As I got to know the generators better, I realized from the manuals that they did have paralleling capability within the exciters and studied with my then limited knowledge to figure how they worked. We started after a while running the generators in parallel and simply turning off one at nightime, but keeping the two smallest units operating in parallel so if one quit we had some time before loosing power. This worked great, but I remember my mind and body was so tuned to the sounds from the generator, that when one started to have problems in the middle of the night, I would awake to find myself running towards the generator shed without any prior thought. THEN came the time when the owner purchased a larger 3 phase generator and wanted to put it in parallel with the single phase units. That was a challenge that I had to get my father to help with. It involved a lot of rewiring and an actual physical rod connection between the diesel injector pumps on the prime movers. Paralleling single phase and 3 phase generators is not in any books I have found, but it can be done because I have done it.

In my career as an EE, I settled into field engineering working with just about any large electrical equipment, but sort of specializing in generators and exciters, but mainly really large ones for utilities and large industrial co-generation. These are by nature, paralleled and operate connected to the nationwide grid. The nuclear plants were the biggest challenge because any changes had to be approved by a national regulatory agency, which made some decisions not on technology but on politics. We could operate with the approved equipment, but even if it was proved that a change would improve reliability it might not be approved. I remember a particularly frustrating experience in Japan.

At the end of my carreer, my employer asked me to open a field office near my home town and in particular work with the local utility on some problems and of course the large casinos there. The first job I had was a phase-in-balance on the AC lines, that fed the casino that had replaced the service station that I worked in during my job attending the small generators mentioned earlier. The solution was a simple one, and of course, no one was there from the old days, but it was ironic for me. I did, however get back to the paralleling of smaller diesel generators which were present in every casino in case the utility went down. I got a reputation for being able to spot problems caused by faulty equipment and incorrect wiring. This was when programmable controllers and other computers were used and the diagnosis and correction was frequently done on a keyboard. It was interesting to find so many problems with manufacturers or consultants software with really basic problems. Getting the manufacturers or consultants to agree to their errors was very difficult. Almost as bad as regulatory agencies.

I have bored any of you who have reached this point, I apologize. Early morning, memories, and things I really don't want to do. Sorry.

Check the governor settings on both machines. One should be on "isochronous" to maintain frequency and the other should be on "droop" to follow. If both are on isochroconous they will fight each other and if they are both on droop, your frequency will drift.

In my opinion, you tested the reverse power of the second generator while the first generator was driven by Caterpillar Diesel motor and the second was not [driven] at all. That means 16 kW is the no-load of the second generator works as synchronous motor. You cannot increase further the reverse power only if you will use a brake -or an induction motor used as brake connected-mechanically-with second generator shaft.