ABB Relion 670 Series Technical Reference Manual page 304

Section 6
Impedance protection
298
where:
V | and |I | are the positive sequence voltage and current magnitude
1 1
V1Level ,
are the setting of limits for positive sequence voltage and current
I1LowLevel
IMaxLoad
is the setting of the maximum load current
The output signal for detection of three-phase fault is only released if not ground fault
and phase-to-phase fault in the main sequence function is detected.
The conditions for not detecting ground fault are the inverse of equation 5 to 10.
The condition for not detecting phase-to-phase faults is determined by three conditions.
Each of them gives condition for not detecting phase-to-phase fault. Those are:
1:
ground fault is detected
or
|3I IN|> 0.05 ·
0
and
|3I IN|>maxIph ·
0
2:
phase-to-ground and phase-to-phase faults are not fulfilled
and
maxIph<0.1 ·
and
|I |<0.1 · maxIph
2
3:
|3I IN|>maxIph ·
0
or
|I |<maxIph ·
2
where:
maxIph is the maximum of the phase currents IA, IB and IC
INRelPG is the setting parameter for 3I0 limit for release of phase-to-ground fault loops
|I | is the magnitude of the negative sequence current
2
I2ILmax is the setting parameter for the relation between negative sequence current
to the maximum phase current in percent of
3I0BLK_PP is the setting parameter for 3I
loops
IBase
INRelPG
IBase
3I0BLK_PP
I2maxIL
limit for blocking phase to phase measuring
0
1MRK505222-UUS C
IBase
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