ABB RELION 650 SERIES, Technical Manual

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Since the polarizing voltage is also used for the Mho distance characteristics, the
magnitude of the voltage is just as interesting as the phase. If there are symmetrical
conditions and the measured per phase positive sequence voltage magnitude is
above 75% of the base voltage before the fault, the pre-fault magnitude will be
memorized and used as long as there is a fault. The phase angle however will only
be memorized (locked) for 75 ms at a time, not to lose synchronism with the real
system voltage.
Should the positive sequence voltage drop below 2% of the base voltage, it will be
considered invalid. In this situation, directional signals and starts from Mho
elements will be sealed-in and kept static as long as there is a fault.
6.1.7.5 Fuse failure
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The ZMFPDIS function has to be blocked by an additional function like the Fuse
failure supervision (FUFSPVC) or an equivalent external device. Typically, the
binary input VTSZ is used for this purpose.
A built-in supervision feature within distance protection itself, based on phase
current change, will ensure that the FUFSPVC blocking signal is received in time.
Namely, an intentional time delay will be introduced if no current magnitude
change greater than 5% of IBase has been detected for any of the three phase
currents.
6.1.7.6 Power swings
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There is need for external blocking of the ZMFPDIS function during power
swings, either from the Power Swing Blocking function (ZMRPSB) or an external
device.
6.1.7.7 Measuring principles
Quadrilateral characteristic
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ZMFPDIS implements quadrilateral and mho characteristic in all the six zones
separately. Set
OpModePEZx or OpModePPZx to Quadrilateral , to choose
particular measuring loop in a zone to work as quadrilateral distance protection.
All ZMFPDIS zones operate according to the non-directional impedance
characteristics presented in figure
33 and figure 32 . The phase-to-earth
characteristic is given in ohms-per-loop domain while the phase-to-phase
characteristic is given in ohms-per-phase domain.
Zone 1 has individual positive sequence impedance settings for phase-to-phase and
phase-to-earth (X1PPZ1, R1PPZ1 and X1PEZ1, R1PEZ1). For the other zones, the
positive sequence impedance reach is common for phase-to-phase and phase-to-
earth (X1Zx, R1Zx).
1MRK 506 382-UEN A
Section 6
Impedance protection
Line distance protection REL650 2.2 IEC 97
Technical manual