Setting Guidelines; General; Setting Of Zone 1; Setting Of Overreaching Zone - ABB RELION 670 Series Applications Manual

Section 7
Impedance protection
In practice, the setting of fault resistance for both phase-to-earth
RFPP should be as high as possible without interfering with the load impedance in order to
obtain reliable fault detection.
7.9.3

Setting guidelines

7.9.3.1

General

The settings for Distance measuring zones, quadrilateral characteristic ((ZMRPDIS) are done in
primary values. The instrument transformer ratio that has been set for the analogue input
module is used to automatically convert the measured secondary input signals to primary
values used in (ZMRPDIS).
The following basics must 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 earth-return compensation factor.
• The effect of infeed between the IED and the fault location, including the influence of
different Z
• The phase impedance of non transposed lines is not identical for all fault loops. The
difference between the impedances for different phase-to-earth loops can be as large as
5-10% of the total line impedance.
• The effect from load transfer together with fault resistance may be considerable in some
extreme cases.
• Zero sequence mutual coupling from parallel lines.
7.9.3.2

Setting of zone 1

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 to section
"Parallel line application with mutual coupling"
particular application. By proper setting it is possible to compensate for the cases when the
parallel line is in operation, out of service and not earthed and out of service and earthed in
both ends. The setting of earth-fault reach should be selected to be <95% also when parallel
line is out of service and earthed at both ends (worst case).
7.9.3.3

Setting of overreaching zone

The first overreaching zone (normally zone 2) must detect faults on the whole protected line.
Considering the different errors that might influence the measurement in the same way as for
zone 1, it is necessary to increase the reach of the overreaching zone to at least 120% of the
protected line. The zone 2 reach can be even longer if the fault infeed from adjacent lines at
remote end are considerable higher than the fault current at the IED location.
The setting shall generally not exceed 80% of the following impedances:
• The impedance corresponding to the protected line, plus the first zone reach of the
shortest adjacent line.
• The impedance corresponding to the protected line, plus the impedance of the maximum
number of transformers operating in parallel on the bus at the remote end of the
protected line.
260
/Z ratios of the various sources.
0 1
RFPE and phase-to-phase
and select the case(s) that are valid in the
1MRK 504 152-UEN B
IP14962-1 v1
GUID-FE2F8421-83BA-47FF-AB07-77C242D9650D v1
GUID-36A888E8-F209-478E-B8C4-76370B644386 v1
GUID-2C36623A-7A29-4881-9F33-DA5F5FD36DE5 v1
Application manual