Earth current limiting Resistor

[moose2]

I work at an old mining installation that uses reactors on the star point of all underground transformers to limit earth fault currents. Why use a reactor instead of resistors? I would have thought reactors would create problems with transients/harmonics during earth fault protection switching.

Any thoughts??

 

[DanDel]

Reactors actually work better at transients than resistors. The more rapid the change in current(di/dt, which in this case you can think of as a higher system frequency) the higher the impedance of a reactor.

 

[DanDel]

Reactors actually work better at transients than resistors. The more rapid the change in current(di/dt, which in this case you can think of as a higher system frequency) the higher the impedance of a reactor.

 

[dpc]

Reactance grounding is not used much any longer. The main drawback is the risk of transient overvoltages during faults. To limit the overvoltage conditions, the fault current needs at least about 25% of the normal value. This can still be a lot of current.

Resistance-grounding can provide much greater reduction of fault current without overvoltage concerns, so it has basically replaced reactance-grounding, particularly for industrial facilities.

 

[scottf]

DPC-

From my perspective, there still seems to be quite a bit of use for neutral grounding reactors. In fact, I dare say, it seems there has been an increase over the past few years, for reasons that I am not sure of. Clearly more folks use resistors than reactors, but there are certain applications where a reactor is clearly superior, particularly in EHV applications, where the inherent line capacitance is high.