Earth fault current

  1. Earth fault current
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Ground fault calculation

Earth fault current

\[ I_f = c · \frac{ \sqrt{3} · U · (ω · Ca · La + ω · Cc · Lc)}{ \sqrt{1 + (ω · Ca · La + ω · Cc · Lc)^2 · (3 · Rg)^2 }} \]

· IF: Earth fault current, A

· c: Voltage factor c = 1,10

· U: Voltage between phases, kV

· Ca: Overhead line zero sequence capacitance, F/km

· La: Total length of overhead lines departing from the substation, km

· Ca: Underground line zero sequence capacitance, F/km

· La: Total length of subway lines departing from substation, km

· ω: Current pulsation (2·π·fnet), Hz

· Rg: Grounding resistance, Ω

Neutral isolated

\[ I_f = c · \frac{U}{\sqrt{3} · \sqrt{(Rn + Rg)^2 + (Xn)^2 }} \]

· If: Earth fault current, A

· c: Voltage factor c = 1,10

· U: Voltage between phases, kV

· Rn: Grounding resistance of the network neutral, Ω

· Rg: Grounding resistance, Ω

· Xn: Grounding reactance of the network neutral, Ω