Setting Of Overreaching Zone - ABB RELION 670 SERIES Applications Manual

1MRK 506 369-UUS -
8.1.3.3
Line distance protection REL670 2.2 ANSI
Application manual
In case of parallel lines, consider the influence of the mutual coupling according to section
"Parallel line application with mutual coupling"
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 ground fault reach should be selected to be <85% also when parallel line is
out of service and grounded at both ends (worst case).

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
adjacent lines at remote end are considerable higher than the fault current at the IED
location.
The setting must 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.
If the requirements in the bullet—listed paragraphs above gives a zone2 reach less than
120%, the time delay of zone2 must be increased by approximately 200ms to avoid
unwanted operation in cases when the telecommunication for the short adjacent line at
remote end is down during faults. The zone2 must not be reduced below 120% of the
protected line section. The whole line must be covered under all conditions.
The requirement that the zone 2 shall not reach more than 80% of the shortest adjacent line
at remote end is highlighted with a simple example below.
If a fault occurs at point F (as shown in figure 102, also for the explanation of all
abbreviations used), the IED at point A senses the impedance:
V I I I I I
+ + +
A A C A C B
Z Z Z
= = + ⋅ + ⋅
AF AC CF
I I I
A A A
EQUATION302 V5 EN
and select the case(s) that are valid in your
 I   I I 
+
C C B
R Z 1 Z 1 R
= + +  ⋅ + +  ⋅
 
AC C F F
F F
I I
 A   A 
Section 8
Impedance protection
(Equation 76)
203