Rotor Earth Fault 1 Causes and Solutions

1. It's broken.

2. Mend it.

OK! Now, what's your question?

winding short to earth...

See [for instance]:

http://www.electronics.lnu.edu.ua/elit/pdf/58_20.pdf

or:

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4524422&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D4524422

http://www.albadronline.com/oldsite/books/POWER%20GENERATION%20HANDBOOK/Power%20Generation%20Handbook-Part4.pdf

and more others: see Google : "synchronous generator rotor grounding fault"

Could be a slip ring motor.

On some the star point is earthed.

I catch your point. However, could it be 2 stages-one or two grounded fault- in slip-ring rotor winding? And how the first ground fault would be signalized?

The only way I know of reliably testing a slipring rotor is a transformer test. Supply the rotor at a lower voltage and test the OC voltage on the rings. Any internal shorts will show with unbalanced voltage.

I've not done this test for years, I do remember the last time.

A 3.3KV 2000HP motor, 3.3KV stator, 1750V rotor. 433V connected to the stator gave 229V on the OC sliprings.

I'll be honest we were clutching at straws with this motor. We had consultants galore pontificating about the repeated slipring failures (flashover). All of them wrong. It all boiled down to a poor maintenance regime.

Far to little information supplied to offer anything other than a wild guess.

Our alternater have some probleum iam explining briefly,

while alternator with load of 6MW that time Rotary earth fault 1 activated, we triped the unit then checked exciter winding got burned,we changed the exciter with another one again we synchronised (Auto synchronisation)with load of 2mw after faction of seconds we got alarm of rotary earth fault 1 we triped the unit and checked again exciter coils got shorted,

we didnt recognised the fault from where........................i have dought about before burning the exciter why we did not get any alarm to avoid equipment damage, after damage only we are getting the alarm from rotar earth 1.....

Please kindly expline me proper reson for frequently shorted in exciter,after short only rotary earth fault 1 was activated

Our alternater have some probleum iam explining briefly,

while alternator with load of 6MW that time Rotary earth fault 1 activated, we triped the unit then checked exciter winding got burned,we changed the exciter with another one again we synchronised (Auto synchronisation)with load of 2mw after faction of seconds we got alarm of rotary earth fault 1 we triped the unit and checked again exciter coils got shorted,

we didnt recognised the fault from where........................i have dought about before burning the exciter why we did not get any alarm to avoid equipment damage, after damage only we are getting the alarm from rotar earth 1.....

Please kindly expline me proper reson for frequently shorted in exciter,after short only rotary earth fault 1 was activated

The exciter is a D.C. generator [it is not a static converter], I guess. Then-since it is not an overload I guess-the alternator was at low power output and the time was limited-it was an overvoltage. In this case the problem stays in the control circuit-a sudden interruption or sudden force excitation.