Setting Of Reverse Zone - ABB RELION 670 SERIES Applications Manual

1MRK 506 369-UUS -
8.9.3.4
Line distance protection REL670 2.2 ANSI
Application manual
If any of the above indicates a zone 2 reach less than 120%, the time delay of zone 2 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
zone 2 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 in the example below.
If a fault occurs at point F see figure 121, the IED at point A senses the impedance:
V I I I I I
+ + +
A A C A C B
Z Z Z R
= = + ⋅ + ⋅
AF AC CF
I I I
A A A
EQUATION302 V5 EN
A
I A
21
ANSI05000457 V2 EN
Figure 159: Setting of overreaching zone

Setting of reverse zone

The reverse zone is applicable for purposes of scheme communication logic, current
reversal logic, weak-end infeed logic, and so on. The same applies to the back-up
protection of the bus bar or power transformers. It is necessary to secure, that it always
covers the overreaching zone, used at the remote line IED for the telecommunication
purposes.
Consider the possible enlarging factor that might exist due to fault infeed from adjacent
lines. Equation 131 can be used to calculate the reach in reverse direction when the zone
is used for blocking scheme, weak-end infeed etc.
 I   I I 
+
C C B
Z 1 Z 1 R
= + +  ⋅ + +  ⋅
 
AC C F F
F F
I I
A A
   
Z AC
Z CB
F
C
Z CF
I A+ IB
IB
Section 8
Impedance protection
(Equation 252)
B
ANSI05000457-2-en.vsd
327