Help with generator alternator producing too much power 1

[Waqalevu]

Help requested with 11kV, 3MW generator. Our generator has just returned from a major overhaul, and we are in the process of recommissioning the set. The setup is that the generator supplies power onto a common busbar in parallel with the DNO supply. We supply site load and export any excess power onto the grid. We also have 3 CHP's onto the same busbar, but these have been switched off for the purpose of recommissioning.
The generator drives a 3MW Leroy Somer alternator. Load demand signal is by way of a 4-20mA signal from the PLC. Before the generator was sent away for overhaul, a 20mA load demand signal produced 3 MW output from the alternator. The engine governor is controlled by a Woodward 2301A speed control.
Yesterday we started the engine for the first time since it's return and it failed on overspeed during startup. After several attempts, we trimmed back the start fuel limit, which solved this problem.
Today we ran the set on load for some time. The alternator is now outputting 3.6MW, which is more than it is rated for. So for a 20mA demand signal, we are getting 3.6MW instead of the rated 3MW. The voltage is stable at 11kW, the frequency is stable at 50 Hz.
The governor has been overhauled, and the set has been set up and tested at the factory on their controls (not our controls).
Question is, why are we now getting too much power from the alternator, and how do we trim back?

 

[crshears]

Adjust the speeder gear?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[waross]

Adjust the governor.
It looks as if the factory set it up for 60 Hz instead of 50 Hz.
It's trying to reach 60 Hz, but it is grid tied to 50 Hz.
As a result it is 20% overpowered.
Call the factory.


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[catserveng]

Can you be more clear about the controls you have? A 2301 speed control is only a speed governor, it can be biased by another controller for managing kW load, but doesn't directly take a 4-20mA signal. A 2301A LSSC (Load Share Speed Control) is designed to share kW load with other 2301A LSSC's or with load control devices that use 0-3VDC Load Share lines signal, such as a Woodward GLC or a DSLC.

If your PLC is using 4-20mA as a load reference setpoint to the speed control, then you have some other type controller in between the PLC analog output and the speed control.

Also, is the "governor" on the engine the 2301 is driving actually an actuator, like a UG type actuator, or a ballhead backup type governor/actuator such as an EGB?

More information will get you a better answer.

MikeL.

 

[crshears]

Hmmm...

If it was set up for 60 Hz in the factory, why would it trip on overspeed? ...unless there is a separate overspeed trip that's on site but not part of the unit and that was simply wired back into the control circuitry when the unit came back from the factory, I suppose...

But that opens another poser: is there a separate synchronizing unit that limits the fuel input long enough to smoothly place the unit on the line, but that promptly 'gets out of the way' once the unit synchs and allows the load governor to ramp the unit to 120% of rated capacity?

One way to confirm the load governor is maloperating might be to dial back the fuel rack limiter, presuming one is provided...another more primitive way would be to carefully bleed off hydraulic governor actuating fluid, even if that involves piping up a temporary needle valve just for the proof run.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[catserveng]

So if you do have a 2301A speed control, there is a model that can use a remote speed reference, posting a picture or models number of your governor would be helpful.

You can reference Woodward Manual #02302 if that is the case.

MikeL.

 

[crshears]

Hi MikeL., if I'd seen your first post above I wouldn't have submitted mine; I guess that's one of the by-products of independent responses being composed simultaneously...

Are the fuel rack actuators of these governors all hydraulically based, or do they use a different medium? [ Too busy this early in the shift to look up those Woodward docs ]

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[catserveng]

Pretty much all the 2301 series products were driving hydraulic actuators, most common I work around are the EG series, from 3 to 10 foot lbs of output torque, used mostly on diesel and gas engines up to around 1MW. EGB series actuators have a ballhead backup mechanical governor, when used with this type actuator the 2301 is a "reverse acting", so if the 2301 output goes away the ballhead can take over.

Older engines could also use a UG actuator, mostly these were used on conversions when the original governor was a hydramechanical UG8 or UG32 and the user wanted to go to an electronic governor.

Some of the early ProAct actuator lines (all electric) had driver modules to take a signal from a 2301 and amplify it to drive the electric actuator.

Hope that helps, MikeL

 

[crshears]

Hi Mike, yes it does; thanks!

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]