where:
V
1
| and |I
1
| are the positive sequence voltage and current magnitude
V1Level
,
I1LowLevel
are the setting of limits for positive sequence voltage and current
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
0
IN|> 0.05 ·
IBase
and
|3I
0
IN|>maxIph ·
INRelPG
2:
phase-to-ground and phase-to-phase faults are not fulfilled
and
maxIph<0.1 ·
IBase
and
|I
2
|<0.1 · maxIph
3:
|3I
0
IN|>maxIph ·
3I0BLK_PP
or
|I
2
|<maxIph ·
I2maxIL
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
2
| is the magnitude of the negative sequence current
I2ILmax is the setting parameter for the relation between negative sequence current
to the maximum phase current in percent of
IBase
3I0BLK_PP
is the setting parameter for 3I
0
limit for blocking phase to phase measuring
loops
Section 6 1MRK505222-UUS C
Impedance protection
298
Technical reference manual
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