E/F Protection

What, specifically, would you like to know? I don't understand the details of your question.

My assumption the 33 kV is coming from the bus and connected to 33kV transformer at Delta side, while 6.6 kV is star side and connected to OHL. Neutral point of the Star side is connected to ground (solid or resistance or other..?).

The 33 kV bus has source (remote or closed location) that is provided with grounding. For 33 kV feeder protection You can install E/F relay using residual CT scheme or CBCT if the CT size is meet the cable size. For 6.6 kV you can install REF.

Please disregard this info if my assumption is not correct.

If the 33kV (delta side) is connected to OHL, please be provided the information where is the source (power generation) coming from?

Dear Sir,

My question is that can I use the E/F relay to detect the earth faults on the 33 KV OHL if I have mobile Gen set 5 MW Generation and the Gen set is 415 V rated voltage, and the step up transformer is 4 MVA , 415 V/ 33KV with star at 415V side and with Delta at 33 KV and if you suggest to install earth transformer at the 33 KV side what is rating and specification .

Dear Atif Ali,

Sorry for late response.

"can I use the E/F relay to detect the earth faults on the 33 KV"

Yes you can provide E/F relay for protecting 33 kV OHL, if you put earthing transformer at delta side (33 kV system).

"what is rating and specification".

Sorry, I am not able to determine the earthing transformer kVA, may be other can do it.

Regards,

If the E/F protection is for the Transformer, then REF is perfect as mentioned above (it will be possible to do HV and LV REF).

If the E/F protection is for the OH line, then the re-closer must not close the breaker after an E/F trip is issued.