Section 6 Impedance protection
6.1 Five zone distance protection, quadrilateral and mho
characteristic ZQMPDIS (21)
6.1.1 Identification
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Five zone distance protection,
quadrilateral and mho characteristic
ZQMPDIS
S00346 V1 EN
21
6.1.2 Application
Sub-transmission networks are being extended and often become more and more
complex, consisting of a high number of multi-circuit and/or multi terminal lines of very
different lengths. These changes in the network will normally impose more stringent
demands on the fault clearing equipment in order to maintain an unchanged or increased
security level of the power system.
Five zone distance protection, quadrilateral and mho characteristic ( ZQMPDIS, 21) is a
full scheme distance protection function with simultaneous measurement in all five zones
for phase to phase and phase to ground faults. The function is equipped with five
individually reversible directional zones. This provides a fast and reliable functionality
with built-in redundancy. Each zone has its own independent settings for reactive and
resistive reach and for zero-sequence compensation.
ZQMPDIS (21) is designed to operate in the following modes for phase-to-ground and
phase-to-phase loops: quadrilateral characteristic, mho characteristic and combined
quadrilateral and mho characteristic. Mho relays are simpler than any other distance
protection characteristics but they have an inherent resistive reach problem for phase to
ground loops. The quadrilateral characteristic is suitable for phase to ground loops as it has
definite resistive reach. In these conditions, an optimized combination of mho and
quadrilateral characteristics can be made for distance protection by making mho for phase
to phase loops and quadrilateral for phase to ground loops. This feature of simultaneously
1MRK 506 334-UUS A Section 6
Impedance protection
113
Application manual
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