ABB RELION REX640, Техническое руководство, Страница: 561 / 1960

• Phasor 1 depicts the direction of the 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).
If harmonic components are present in the fault quantities, they turn the phasor
alignment to the negative Im(Yo) axis.
• 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 in
the fault quantities (typically low-ohmic permanent, 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 a high degree of
overcompensation, the phasor turns towards the negative Im(Yo) axis (as phasor
4).
0 deg.
+90 deg.
-90 deg.
+45 deg.
Tilt angle




Figure 322: Directional characteristic of MFADPSDE
The residual current should be measured with accurate Core Balance
Current Transformer (CBCT) to minimize the measurement errors,
especially phase displacement. This is especially important when high
sensitivity of protection is targeted.
The characteristic
Tilt angle should reflect the measurement errors, that
is, the larger the measurement errors, the higher the
Tilt angle setting
should be. A typical setting value of 5 degrees is recommended.
The maximum value for characteristic
Tilt angle depends on the ratio of
the resistive and reactive component in the measured residual current Io.
The operation point moves away from the operation sector mid-point;
the lower is the ratio of the resistive and reactive component in the
1MRS759142 F Protection functions
REX640
Technical Manual
561