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High Impedence Protection - Shunt Reactor

High Impedence Protection - Shunt Reactor

High Impedence Protection - Shunt Reactor

(OP)
This is my 3rd project where in i'm commissioning a Shunt reactor protected with High Impedence Differential Protection ( rating 125 MVAr). I couldn't get a convincing answer as to Why are Shunt Reactors protected with High Impedence Differential Protection? Why not Low Impedence differential Protection?

Have any one of you come across a low impedence differential protection for reactor?  

RE: High Impedence Protection - Shunt Reactor

I think the high-impedance differential  has no restrictions coils and in consequence are more sensitive to low fault currents.

 

RE: High Impedence Protection - Shunt Reactor

High impedance protection has better stability for through faults. Low impedance protection requires an operate current and a restraint current which would normally utilise measurement of the neutral current to perform the calculation within the relay.
Regards
Marmite  

RE: High Impedence Protection - Shunt Reactor

(OP)
Odlanor, Marmite,
Thanks for the replies.  

RE: High Impedence Protection - Shunt Reactor

I think its more historical standard.
HI is more simple and more sensitive ( newer LI is sensitive too), but request a high qulity of CT.

RE: High Impedence Protection - Shunt Reactor

(OP)
Salvag,
You are right, I'm trying to look at the details of the sensitivity issue of High Impedence v/s Low Impedence and found that for same CT characteristics, Low Impedence is more sensitive. And High Impedence has better sensitivity only with a better CT.

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