ABB RELION Series Technical Manual page 385

1MRS758755 A
REC615 and RER615
Technical Manual
In Figure 199, phasors 1...4 demonstrate the behavior of the directional phasor in
different network fault conditions.
• Phasor 1 depicts the direction of accumulated sum admittance phasor in case of
earth fault outside the protected feeder (assuming that the admittance of the
protected feeder is dominantly capacitive). The result is valid regardless of the
fault type (low ohmic, high(er) ohmic, permanent, intermittent or restriking). In
case harmonic components are present in the fault quantities, they would turn the
phasor align to the negative
• Phasor 2 depicts the direction of accumulated sum admittance phasor in case of
earth fault inside the protected feeder when the network is unearthed. The result
is also valid in compensated networks when there are harmonic components
present in the fault quantities (typically low ohmic permanent or intermittent or
restriking fault). In this case, the result is valid regardless of network's actual
compensation degree. Harmonics would turn the phasor align to the positive
Im( Yo )
axis.
• Phasors 3 and 4 depict the direction of accumulated sum admittance phasor in
case of higher-ohmic earth fault in the protected feeder without harmonics in the
fault quantities when the network is compensated. As no harmonic components
are present, the phase angle of the accumulated phasor is determined by the
compensation degree of the network. With high degree of overcompensation, the
phasor turns towards the negative
Protection functions
Im( Yo )
axis.
Im( )
Yo axis (as phasor 4).
Section 4
379