Distance Relay
Distance Relay
(OP)
Guys,
Distance relay can only detect LG or LLG faults and it can not detect LL faults right?
Distance relay can only detect LG or LLG faults and it can not detect LL faults right?
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RE: Distance Relay
RE: Distance Relay
Full scheme distance relays can see
faults in all phase combinations.
RE: Distance Relay
RE: Distance Relay
a = 1 <120 deg
VA = V0 + V1 + V2
IA = I0 + I1 + I2
VC = V0 + a*V1 +a^2*V2
IC = I0 + a*IC + a^2*I2
VAC = VA - VC = V1-a*V1 + V2 - a^2*V2 >>>>> Line to line quantities have no zero sequence dependency
IAC = IA - IC = I1 - a*I1 + I2 - a^2*I2
ZAC = VAC/IAC
Ground distance relays can see all faults but its sensitivity to ground faults is dependent on the k value.
VA = (V0 + V1 + V2), IA = (I0 + I1 + I2)
ZA = VA/(IA + 3*k*I0) = (V0 + V1 + V2) / (I0 + I1 + I2 +3*k*I0) = (V0 + V1 + V2)/ (I1 + I2 + (3*K+1)*I0)
I think though ground distance relay will get the directionality wrong if it has negative sequence directionality and picks up for a phase to phase fault and vice versa. One of the GE relays I think the L90 has a note about DLG fault potentially causing the relay to the get the directionality wrong but I could never figure out from the manual why for sure that was.
RE: Distance Relay