Closing DG output breaker 60 degrees out of phase

We operate a 2600 kW EDG and were performing routine testing. We do not have a synch check relay and the operator closed the DG output breaker at roughly the 2 o'clock position. DG voltage and speed were both slightly higher than the source and hence positive load (KW and VAR) was applied upon closure. No Abnormal alarms were received. The DG was loaded and operated and shut down normally.

What are the impacts on the machine closing in 60 degrees out of phase. What tests/inspections are recommended if any.

 

[electricpete]

I think the biggest concern would be potential damage from the large electromagnetic forces created by the fault-like currents.

Megger check would be quick and easy. Visual inspection of the end-turns for distortion or cracking/splitting of insulation which may have resulted from movement.

Checking the tightness of the slots would be tougher. Easily done in the shop with rotor pulled. I don't think there is any practical way to check that without pulling the rotor.

Surge testing (for turn insulation) and hi-pot testing MIGHT be considered... but you run a risk of failing these insulation during these tests.

 

[12291973]

The impact will be on the coupling bolt which is coupling Diesel engine shaft and And generator shaft. When you Synchronise the machine at more angle, large torque will be produced on the rotor of the the machine. So during next outage of the plant you can check these bolts.