ABB Relion REG670, Applications Manual

Page: 255 / 780

If a fault occurs at point F, see figure 91 , 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
(Equation 126)
A B
Z<
C
I
C
Z
AC
Z
CB
Z
CF
I
A
+ I
C
IEC09000256-2-en.vsd
F
I
A
I
B
IEC09000256 V2 EN
Figure 129: Setting of overreaching zone
8.3.4.4 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 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. The equation can be used to calculate the reach in reverse direction
when the zone is used for blocking scheme, weak-end infeed, and so on.
Z
rev
1.2 × (Z2
rem
- ZL)
>
_
GUID-ABFB1C53-F12A-45D5-90CC-907C9FA0EFC3 V1 EN
(Equation 127)
Where:
ZL
is the protected line impedance.
Z2rem is the zone 2 setting (zone used in the POTT scheme) at the remote end of the protected line.
In many applications it might be necessary to consider the enlarging factor due to the
fault current infeed from adjacent lines in the reverse direction in order to obtain
certain sensitivity.
8.3.4.5 Series compensated and adjacent lines
1MRK 502 071-UEN -
Section 8
Impedance protection
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 249
Application manual