ABB Relion REG670, Technical Manual

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faults generating heavily distorted signals. These faults are handled with outmost
security and dependability, although sometimes with reduced operating speed.
High speed distance protection ZMFCPDIS is fundamentally the same function as
ZMFPDIS but provides more flexibility in zone settings to suit more complex
applications, such as series compensated lines. In operation for series compensated
networks, the parameters of the directional function are altered to handle voltage
reversal.
The ZMFCPDIS function is a six-zone full scheme protection with three fault loops
for phase-to-phase faults and three fault loops for phase-to-earth faults for each of the
independent zones, which makes the function suitable in applications with single-
phase autoreclosing.
The zones can operate independently of each other in directional (forward or reverse)
or non-directional mode. This makes them suitable, together with a communication
scheme, for protection of power lines and cables in complex network configurations,
such as parallel lines, multi-terminal lines, and so on.
A new built-in adaptive load compensation algorithm prevents overreaching of the
distance zones in the load exporting end during phase-to-earth faults on heavily
loaded power lines. It also reduces underreach in the importing end.
The ZMFCPDIS function block incorporates a phase-selection element and a
directional element, contrary to previous designs in the 670–series, where these
elements were represented with separate function blocks.
The operation of the phase-selection element is primarily based on current change
criteria, with significant increased dependability. Naturally, there is also a part
operating with continuous criteria that operates in parallel
The directional element utilizes a set of well-established quantities to provide fast and
correct directional evaluation during various conditions, including close-in three-
phase faults, simultaneous faults and faults with only zero-sequence in-feed.
1MRK502052-UEN B
Section 7
Impedance protection
227
Technical manual