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3-phase MVA

3-phase MVA

3-phase MVA

(OP)
If I have a value of 500MVA on a bus, does it means its available 3-phase short circuit MVA from utility? If yes, how I can calculate Line to Ground MVA from this.

Thanks in advance

RE: 3-phase MVA

Probably the transformer capacity.
Available short circuit current is usually reported in kA.
Be aware that the available short circuit current is not the same as the maximum possible fault current.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: 3-phase MVA

Hi burntcoil

Your info is a bit scarce to go by. Did the utility state that the threephase fault level at the bus is 500MVA? If so then by that is usually mean that a solid threephase fault at the bus will yield a fault level of 500MVA  =  sqrt(3)*VL*IF.

VL  =  line voltage (you will need to find out from the utility (or whoever your source is)what value of voltage was used. Sometime 1p.u. or sometimes 1.1p.u. is used, etc.

IF  =  short circuit current.

I'm afraid you cannot conclusively say what the eartfault current will be as that depends on the system earthing. If you assume solid earthing (which is most likely the case with most HV systems > 66kV) then then EF current is in the same order as the threephase current but the MVA level will be one third, i.e. 167MVA. If < 66kV I would be way of making this assumption.

Best is to get these values from your source.

Regards.



  

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