I have 3 Waukesha LNG generators that run in parallel, the number running depending on load requirements. These gens are 1200 KW units. There is no automatic load sharing, I set them up for speed and voltage and when they are put online the rig hands simply wait for the synchro scope to be in the proper position before closing the breaker, bringing it online. This can take some time as the speeds are well matched! This set up works fine as I have two other rigs with the same setup and controls and no issues.

However, on the rig that has driven me to post here.....

Two of the generators run fine together, the third will not run with the other two. It is what it is doing that has us confounded. It shows perfectly balanced KW and KVars with the other two (or one - depending) but twice the amperage. The amperage readings are correct as checked with a clamp on meter (multiple meters actually). It is so bad that it will eventually black out the rig if you leave it running. The generator will run fine by itself and show proper KW for the load applied on the analog meters, so it seems that the metering system is working properly.

Example: Gen 1 and 2 are running at 500 KW, 2 KVars apiece, and pulling - say 600 amps apiece. When I put gen 3 online the amps on gens 1 & 2 will drop to 300 each and the amps on 3 will go to 600. The KW and KVars will be balanced on all 3. If I let it run the amps on 3 will continue to climb while they drop on the other two. Eventually, with enough load, gen 3 will overload and shut down, causing the other two to shut down as well - reverse power I think.

How can you have balanced KW and KVars but be pulling twice the amps?

Note: We have swapped out the gen controller on 3 to no avail.

 

RigMan,

A generator is a device for converting torque into amperes. Torque is produced by the prime mover--the engine is this case. More fuel equals more torque. The generator just converts torque into amperes, so there must be something amiss with the engine governor or the fuel pressure regulator.

I'm not familiar with the fuel control valve/mechanism for these engines, nor what signal output from the governor controls the valve/mechanism.

But, if the amperes are increasing it's because the torque is increasing, and if the torque is increasing it's because the fuel is increasing. And fuel is controlled by the engine governor.

Please write back to let us know how you fare in resolving the problem.

I'm very confused, though, because you say there's no automatic load sharing and unless the operators are manually setting the load setpoint and changing it as the load changes, it would certainly seem there is some kind of load sharing or power system controller. And if there is, then the problem may be coming from that.

 

> I have 3 Waukesha LNG generators that run in parallel, the number running depending on load requirements. These
> gens are 1200 KW units. There is no automatic load sharing, I set them up for speed and voltage and when they are
> put online the rig hands simply wait for the synchro scope to be in the proper position before closing the breaker,
> bringing it online. This can take some time as the speeds are well matched! This set up works fine as I have two
> other rigs with the same setup and controls and no issues.

Pl. check the VOLTAGE DROOP CHARACTER of the 3rd GENERATOR. The Voltage Droop Character will DECIDE the LOAD SHARING.