Reverse Power

If the relay is good, you are having voltage fluctuation beyond the set limit....It would seem that the outputs are not synchronous...You must test each generator, one at a time...measure each output off and under load...You may need to find a more qualified troubleshooter, this requires step by step testing until you can isolate the problem...

There are some things to be checked:

1)if the governor does not adequately operate, you may check wether the blades are properly operating. If this is the fact, the generator set must not run speed-no-load,and, conversely, be shut down for averiguation;

2)if it is a transient situation, a difference between impedances in the different paths connecting to the generator - including the generator - may cause a circulating current which may produce a reverse power. In this case, you may go to speed-no-load and check the aforementioned impedance

3)you may as well check if the droop of each of the generators are matching and correct the distortion.

In any case, it is advisable to organize a meeting between the governor manuacturer and the relay manufacturer so that they can advice you on how and which measures may be taken.

Kind regards

As per your statement there seems to be two buses/circuits. One is having number of generators which all tripped and another one is with two separate generators. In the circuit of two generators again one trips and a single generator remains on-load it means the load on second bus of two generators is within limit hence out of two one is still on load. So the probable cause of tripping surely not of reverse power but something else. Please first check up fuel supply, cooling water and ventilation etc.

Dear Guest: Is hard to analize this problem with so little information. To my understanding, the last two generators are tied to the same grid and probably close to each other. If this is the case they are probably hunting or oscilating, loading each other back and forth due to a diference in their speed drop settings. For two prime movers to work together, conected to the same grid, they need to meet certain criteria. The bigger unit should be set to speed droop 0% and the small one should be set to any convenience value other than 0%, otherwise they will oscilate by transfering load between both units. At one time one unit will load the other an viceversa, this will cause one unit to be motorized (reverse power). This in turn will trip one unit depending on the protection settings. It may help if you load the system with resistived load (something like street lights) in order to avoid unstable load (like electrical motors), also you may need to program the governor in order to change the speed droop so they can generate power when they are isolated from the main electrical system. You may check some literature at Woodward Governors.

Hope this will help you and I will like to know more about your operation so we can share our experiences. Regards. Luis