ABB Relion 670 series - Setting Guidelines; General; Setting of Overreaching Zone; Setting of Zone1

8.5.3 Setting guidelines
8.5.3.1 General
The settings for the Full-scheme distance protection, quadrilateral for earth faults
(ZMMPDIS, 21) function are done in primary values. The instrument transformer ratio
that has been set for the analogue input card is used to automatically convert the measured
secondary input signals to primary values used in ZMMPDIS (21) function.
The following basics should be considered, depending on application, when doing the
setting calculations:
• Errors introduced by current and voltage instrument transformers, particularly under
transient conditions.
• Inaccuracies in the line zero-sequence impedance data, and their effect on the
calculated value of the ground-return compensation factor.
• The effect of infeed between the IED and the fault location, including the influence
of different Z0/Z1 ratios of the various sources.
• The phase impedance of non transposed lines is not identical for all fault loops. The
difference between the impedances for different phase-to-ground loops can be as
large as 5-10% of the total line impedance.
• The effect of a load transfer between the IEDs of the protected fault resistance is
considerable, the effect must be recognized.
• Zero-sequence mutual coupling from parallel lines.
8.5.3.2 Setting of zone1
The different errors mentioned earlier usually require a limitation of the underreaching
zone (normally zone 1) to 75 - 90% of the protected line.
In case of parallel lines, consider the influence of the mutual coupling according tosection
"Parallel line application with mutual coupling" and select the case(s) that are valid in your
application. We recommend to compensate setting for the cases when the parallel line is
in operation, out of service and not grounded and out of service and grounded in both ends.
The setting of grounded fault reach should be selected to be <95% also when parallel line
is out of service and grounded at both ends (worst case).
8.5.3.3 Setting of overreaching zone
The first overreaching zone (normally zone2) must detect faults on the whole protected
line. Considering the different errors that might influence the measurement in the same
way as for zone1, it is necessary to increase the reach of the overreaching zone to at least
120% of the protected line. The zone2 reach can be even higher if the fault infeed from
Section 8 1MRK 506 369-UUS -
Impedance protection
294 Line distance protection REL670 2.2 ANSI
Application manual