ABB Relion 670 series, Руководство по применению, Страница: 262 / 760

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 wit a simple example below.
If a fault occurs at point F, the IED at point A senses the impedance:
Z
V
I
Z
I I
I
Z
I I I
I
R Z
I
I
Z
AF
A
A
AC
A C
A
CF
A C B
A
F
AC
C
A
C
= = +
+
⋅ +
+ +
⋅ = + +





 ⋅
1
F F
C B
A
F
I I
I
R + +
+





 ⋅
1
EQUATION302 V5 EN-US
(Equation 227)
A
B
Z<
C
I A
IC
Z AC
Z CB
Z CF
I A+ IC
IEC05000457-2-en.vsd
F
IB
IEC05000457 V2 EN-US
Figure 160: Setting of overreaching zone
7.5.3.4 Setting of reverse zone
SEMOD154704-33 v3
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 228 can be used to calculate the reach in reverse direction when the zone is used for
blocking scheme, weak-end infeed and so on.
( )
1.2 2
³ × -
Zrev ZL Z rem
EQUATION1525 V5 EN-US
(Equation 228)
Where:
ZL is the protected line impedance
Z2rem is zone2 setting at remote end of protected line
In some applications it might be necessary to consider the enlarging factor due to fault
current infeed from adjacent lines in the reverse direction in order to obtain certain sensitivity.
7.5.3.5 Setting of zones for parallel line application
SEMOD154704-48 v1
Section 7 1MRK 505 343-UEN B
Impedance protection
256
Application manual