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Ground Protection

Ground Protection

Ground Protection

(OP)
Hi forum experts,

My 22 kV sub station is powered via a nearby power station which means that the 22 kV earthing is actually located in the power station.Now,we are planning to use an alternative supply to power my sub-station when the power plant is not available.This means that I will need an earthing point on the 22 k V network.This earthing point would not be required when the nearby power station is in service.I am looking for the most convenient way to proceed.
Any suggestion.

Guardiano

RE: Ground Protection

What is your alternative supply, maybe its also with some earthing point.
If not, you can add grounding trasformer on your BB 22kV ( not important what kind or GrTr: zig-zag or wye/delta) and build additional logick for it connection.
Actually, need more information about your substation configuration.

RE: Ground Protection

(OP)
Thanks Slavag for your comments. The sub station transformers are of YY type and the alternative supply is the utility.

Guardiano

RE: Ground Protection

You must check with utilities, what kind of neutral groinding of 22kV network:
resistive
compensated
Im not sure if 22kV utilities network is solid grounded...

RE: Ground Protection

My opinion is your Substation Grounding Grid is connected with the Power Station grounding grid
or directly under ground or by means of a grounding wire or static wire, or cable shields or else..
If the Power Station grounding grid is close to your substation may be included in Power Station Grounding Grid
This fact will reduce the locally grounding fault resistance but will increase the grounding fault current.
I shall take the both-grounding grid resistance and grounding fault current as per Power Station.
Your substation has to be provided with its own grounding grid and has to be check the emash [as per IEEE-80-2000]
for this grounding grid configuration. Also the fence potential and grounding has to be check.
If the second source is far from this Substation you have to know [or calculate] the grounding fault current from this source and starting with the Utility fault current [or apparent power] at your net point and then calculate the emash for the new situation. Usually this second current will be less then this supplied from Power Station.
 

RE: Ground Protection

I think, we told about neutral gronding system, not about grounding grid
From time to time its problem.
For example, power staion with resistive grounding, and reserve system with compansated grounding, in this case outgoing protective terminals must be included bot 51N and 67Ns functionality

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