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Effect of neutral reactance on transient overvoltages (high resistance grounding)

Effect of neutral reactance on transient overvoltages (high resistance grounding)

Effect of neutral reactance on transient overvoltages (high resistance grounding)

(OP)
Greetings:

Attached is a picture of the zero sequence network of a solid ground fault with high resistance grounding (from EPRI "Grounding and Lighting Protection")

Practically speaking, if the resistor/xfmr was connected to the neutral through a long cable (say 5kV, 2/0, 200'), would its shunt capacitance (zero sequence capacitance) contribute to the total 3Ico ("3-phase") charging current? This charging current (3Ico) is from the two unfaulted phases. Could the neutral shunt capacitance formed by the cable (which only becomes charged upon the fault creating V_ng=V_ll from V_ng=0) be modeled by a capacitor in parallel with Xco in the attached figure?

If anyone has the ABB T&D book, Chapter 14, page 521, fig. 48 (sorry could not upload), does this plot indicate that such a neutral cable shunt capacitance can be neglected in 3Ico (Xco)? Thanks for your thoughts.

RE: Effect of neutral reactance on transient overvoltages (high resistance grounding)

NO! X0 does not include Xc0
Xo only include ractance of resistor and transformer
If X0 = 0 we have fig 47 values as fig 48 values;

fig. 47
X axe
ratio kW/kVA : 1.0
Yaxe
unfaulted phase: 260V
neutral to gtound: 165V
faulted phase: 120V

fig. 48
X axe
Xo/R0 ratio: 0
Yaxe
unfaulted phase: 260V
neutral to gtound: 165V
faulted phase: 120V


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