Setting Of Reverse Zone - ABB RELION 670 SERIES Applications Manual

Section 8
Impedance protection
8.13.4.4
422
• 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.
Larger overreach than the mentioned 80% can often be acceptable due to fault current
infeed from other lines. This requires however analysis by means of fault calculations.
If the chosen zone 2 reach gives such a value that it will interfere with zone 2 on adjacent
lines, the time delay of zone 2 must be increased by approximately 200 ms to avoid
unwanted operation in cases when the telecommunication for the short adjacent line at the
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
+
A C
A
Z Z
= = +
AF AC
I I
A A
EQUATION302 V5 EN
A
I A
21
ANSI05000457 V2 EN
Figure 220: Setting of overreaching zone

Setting of reverse zone

The reverse zone (zone RV) 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
I I I
+ +
A C B
Z R Z
⋅ + ⋅ =
CF
F
I
A
Z AC
Z CB
F
C
Z CF
I A+ IB
IB
1MRK 506 369-UUS -
  
I I
C C
1 Z 1
+ +  ⋅ + +
 
AC C F F
I
 A  
B
ANSI05000457-2-en.vsd
Line distance protection REL670 2.2 ANSI
Application manual

I
+
B
R
 ⋅
F
I
A 
(Equation 380)