Parrallel Operation Power Plant & GRID

The generator may have lost excitation due to some reason which you may figure out and hence the drop in power output. Synchronous machines when under excited draw power from the grid and when over excited supply power to the grid. Epsilon

Actually, once a synchronous machine is on the grid, over-exciting or under exciting changes the amount of reactive power produced. Under-excited, it becomes lagging, over-excited, it become leading. Upon compete loss of excitation, it would no longer parallel the grid, and after 15 seconds, it is most likely that the breaker would trip if the excitation was restored. Did you notice the power factor during these events?

Most likely, the prime mover suffered some kind of "hiccup" and could not drive the generator to produce the full power needed, only part of it. If the power factor stayed at close to unity, it as something to do with this. If you saw a wild swing in the power factor during the event, then it does have something to do with a partial loss of excitiation as Epsilon suggested, look closer at your AVR.

In Parallel-with-Grid Power generation, the active power component is determined by the prime mover behaviour, while the reactive part is by the excitation control. You may want to check you prime-mover controls for 'stickiness' or such-like misbehaviour, or check if you didn't lose some feedback loop for those 15 secs.

Power factor controls (i.e. excitation has very little to do with the 6MW drop). Loss of excitation would trip the breaker within 2 secs depending on your protection settings.

By the way, what do you have installed exactly? I mean hardware, metering and SCADA.

Very good answer by Guest.

Excitation affect the power factor( MVARs is this case).

the MW is affected by the torque from the prime mover.

I have been in the power generation business for 30 years.have seen this hundreds of times.

Your problem, primarily, would have been reduced fuel to the machine, which whould have been controlled by your governor valve /control system if it was not a filter blockage etc. You did not say what type of engine you had.

If you have a control system with any type of HMI based monitoring, check the historical trend . If you have an analog or hydraulic without electronic monitoring then you may have to use some sort of recorder on the fuel demand/ fuel supply signal to troubleshoot.

If you are on a grid where the frequency varies drastically and you are in "droop" control, high frequencies will reduce the MW generated by your machine.

You did not say whet tyu

hello sir...

iam venkat .now iam in 2000m combined cycle power plant(steam and gas ).we have UAT TRANSFORMER . for wat pupose it will be used ?. Also i want to know abt the Excitation Compartment in detail and how it Excite the Generator.My id is ktva361_eee@yahoo.co.in .

Thanks for your intial consideration

Dear Sir,

When we are connected in synchronism with a major grid system with relays for safe system operation, such phenomenon ususally takes place.

This is a clear cut case of interconnected tie line operation connecting two systems and both the systems running in parallel.

As you have mentioned that the phenomenon remained just for 15seconds, it means either the CPP's generation might have increased or your system might have subsequently delinked from the major grid due to tripping of the interconnected tie line.

Regards,

Ulhas Pradhan

Disconnecton from the grid would not result in an import of 6 MW. As mentioned by guest, likely an issue with the prime mover and a drop in torque. We operate 2 machines in parallel with a grid connection. To shift load from one machine to the other, less fuel (steam) is admitted causing a drop in generator output (and vice versa for the other). Excitation control, as mentioned before, affects only terminal voltage and reactive power.