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System Grounding

I have 11kV(resistance grounded) system with 34MW generator (STG) and grid with 132/11kV incomer - generator neutral is resistance grounded, When both system is operated in isolated mode each of system grounding will come to picture. If both (Grid and Generator) are running in parallel " WHETHER BOTH OF THE SYSTEM IS GROUNDED" or any one of system grounding to be removed to have the effective GROUND fault detection????????. if so which grounding to be retained. If both system is grounded if there is a fault say L-G fault the ground fault in the system is seen by both of earth fault relays in both of the system grid and generator also it is noted that current seen by the relays is not the actual current and also it depends on the location of the fault. Please explain how to provide system grounding.

Reply to
Govind
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You have given insufficient information. No-one here knows just what the connections are (I assume that the grid is grounded Y on the high side and delta on the low side-is it? Do you know?).

I suggest that you pay a professional to look at your specific system and review the grounding and protection systems. Depending on guesses made, even by experienced engineers is like getting a medical diagnosis and plan for treatment over the phone ).

Reply to
Don Kelly

Sorry for insufficient information!... Following are the details of the system

A). 11kV Grid supply

1.Incoming Transformer - Ynyn / 132/11kV / Primary and Secondary Resistance Earthed 2.Secondary side of the Trafo feeds a 11kV Swr

B). 11kV Generator

  1. 34MW, TG, 11kV, Star Connection, System earthed via Resistance.
  2. Generator feeding above said same 11kV Swgr.
  3. Resistance Earthing has motorized isolator for isolating/ closing the neutral(in generator side)

Please explain what to be done when both operates in parallel regarding earthing. My main question is if both system are grounded if the earth fault occurs in the system (say exactly middle - say equal resistance for both the systems) then both of the relay will see the ground fault current but it is half of the ground fault current. Whether directional earth fault is suitable for this application ????

Govind

Reply to
Govind

I repeat- free advice is worth all it costs. Hire a consultant and get the job done properly by someone who is (a)competent and (b) can actually look at your setup. (you may also have some triplen harmonic voltages in your setup). You will have to pay going rates for the combination of (a) and (b). I cannot, ethically, advise you otherwise.

Reply to
Don Kelly

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