Generator Reverse Power

Something is backwards.

Look on page 231.

I think you already have your answer. "Prior to synchronization to grid."

That's the puzzle rather than the answer.

The puzzle is why the generator was connected to the grid prior to synchronization?

It didn't read to me that it had been connected to the grid yet, but that might be an interpretation.

Has some maintenance just been performed on this generator? If yes, then that is where you should start looking for your problem.

Perhaps, after you share with us exactly what was going on; things like the rating and type of the unit, how it was being synchronized, buttons pushed, the type of protective relaying and flags dropped, what "prior to synchronization" means exactly, etc., etc.

LINK

try this for an answer.....

Sounds like you have something wired backwards....or start-up sequence wrong....when was the last time maintenance was performed on the static exciter system? These static exciter systems are high maintenance...

http://control.com/thread/1232026413

http://hydropower.ornl.gov/docs/HAP/ElecExciterBestPractice.pdf

Reverse power occures due to frequency mismatch of your system with grid. Frequecy of your system depends on fuel supply to your engine. The reverse power only can occure due to problem in your fuel system. Fuel system problem may be from choaked filter/strainer, Fuel control valve and related fuel control system or insufficient fuel supply.

Right..

It would seem that the link I placed in an earlier reply has not been looked at, so to quote from that link

"Reverse power generally describes a condition where the prime mover of a generator is not supplying sufficient torque to keep the generator rotor spinning at the same frequency as the grid to which the generator is connected. In other words, the generator has actually become a motor and is drawing current from the grid to which is connected and is supplying torque to the prime mover which is supposed to be supplying torque to the generator.

During synchronization, it might be possible to have the synchroscope rotating in the Slow direction (anti-clockwise) and then close the breaker. Under this condition, the generator would then be drawing a small amount of current from the grid instead of supplying a small amount of current to the grid (which occurs when the breaker is closed with the synchroscope rotates in the Fast (clockwise) direction).

I have seen some prime mover control systems (and exciter regulator control systems and synchronizers) that try to increase load slightly as soon as the generator breaker is closed. On a couple of sites, after a maintenance outage, I have seen the output of the control mis-connected to the control valve and cause the load to actually decrease instead of increase and cause the generator to trip on reverse power. One case was a paper mill that had a DC motor on the steam control valve actuator and the motor leads were reversed."

If you are asking reverse power during synchronization then it normally happens when synchroscope needle is moving from negative direction and crossing zero and you closed the breaker. Always do the synchronization in positive direction by looking the trends of the needle movement.

Dear All

few more details are here

1) "Prior to synchronization" means the generator did not connected to grid, and the generator is getting tripped on reverse power before synchronization to grid

2) The generator is getting tripped on reverse power while terminal voltage reaching to rated 15KV from 0KV

3) There is no issues from prime mover side and fuel

4) ABB make REG 316 is the protection relay

5) Generator & AVR make: SIEMENS

6) Reverse power setting is -2.6MW, 2sec, as per events list the relay got operated at -5.2MW for first time and -4.0MW at second time

You got some readin to do....

https://library.e.abb.com/public/7dad4d661f676198c125785a0057dbb1/1KHA000835-UEN_en_RE.316_4_Numerical_Protection_and_Control_Unit_-_Operating_Instructions_(Edition_Oct_2004).pdf

Reverse power can not occur before synchronization------ basic of electrical engineering.

Your REG 316 is malfunctioning. Try to switch of the power for few seconds and switched it on, check for its function, if ok no problem , otherwise call vendor for reprogram or replacement.

Sounds like protection relay is not configured correctly or operating correctly. Reverse power should only occur when connected to another source.

please check your MW transducer, it should be giving 0 MW before synchronizing to grid.

Alex, I'd like Generators for $800 please.

If your generator protection is tripping on reverse power with the generator not yet synchronized / connected to the bus, then you could have one or more of several problems:

1. The relay is wired to the CT and/or VT inputs imcorrectly. It would help if you could post a schematic of the relay connections to the instrument transformers and generator bus. Where are the CTs and are they of proper ratio, phasing, and polarity? Same with VTs?

2. The relay is programmed incorrectly. Is this reverse power setting correct, per the device coordination study?

3. The relay is operating incorrectly, and sensing something it shouldn't. Was the relay bench tested to verify that it operates at the proper setpoints for appropriate voltage and current inputs?

A consideration ifor the ABB REG316 (or other numerical, multifunction relay) is when should a particular function be enabled. I would suggest that the reverse power function should be disabled while the generator is not yet synced to the bus, because that function is not relevant yet. Reverse power protection is actually only relevant when the generator is connected to the bus. Other protection functions are used to protect the gen wirings before this point. In looking at schematics for older style, electromechanical reverse power relays (such as the GE ICW51), they usually put a Normally Open contact (52a) of the generator circuit breaker in series with the relay's reverse power trip output, so that the trip could only operate after the breaker is closed and the generator synced to the bus.