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20MVA Current Limiting Reactor Impedance

20MVA Current Limiting Reactor Impedance

20MVA Current Limiting Reactor Impedance

Good day

I have been asked to do a protection and grading study for a 11kV distribution network (doing in ETAP). One of the feeders coming out of the main 11kV substation has a series reactor installed on it, to limit the fault current seen by the downstream substation.

The client has given me everything like cable size and length, fault levels on upstream S/S etc. But I requested info of the reactor and the operator said doesnt have the reactor specs, besides letting know that it is a 20MVA, 3 phase.

ETAP wants the positive sequence and zero sequence of this 3 phase series reactor. I asked for the operator to check nameplate but too old to see. Anyone here who has worked with an almost similar unit? I just need the typical impedance values so that I can run the Short Circuit calculation. Your help is appreciate as this has become an urgent request.

RE: 20MVA Current Limiting Reactor Impedance

Correct and complete data is important for a meaningful short circuit study.
If the data is not available, it has to be measured at site by testing the Reactor. I suppose the responsibility to provide data lies with the client. Your duty is to highlight the importance of the data and what could happen to the final outcome if incorrect / typical data is used in the study.
There are professional agencies who can test the reactor to establish its parameters. Alternatively, the OEM will be able to send the data if the client informs the OEM the Serial number and year of manufacture.

RE: 20MVA Current Limiting Reactor Impedance

@Ashdgee (Electrical)
If you were given the fault current limit that your reactor is limiting, you can compute the reactor details using the formula:
Reactor MVA = Ilimit2 x 1.732 x Xr/(1X106)
where: Xr is the reactor impedance in ohms.
To get the %Xr, multiply your calculated Xr by the rated current of the feeder and then divide by the line-to-neutral voltage.

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