ABB REL670 2.2 IEC, Руководство по применению

Страница: 253 / 908

K
N
is earth compensation factor for single circuit set at the relay given
by equation
Z
0m
is the zero sequence mutual coupling between the faulted and the
parallel line
0 1
1
3
N
Z Z
K
Z
=
-
×
IECEQUATION14005 V1 EN-US
(Equation 164)
K
Z
Z
Nm
m
=
⋅
0
1
3
IEC13000297 V1 EN-US
(Equation 165)
From the above it can be deduced:
• Error is proportional to the mutual coupling factor K
0m
• The error increases with the parallel line earth current in relation to the relay
current
• The relay underreaches when I
EP
is in phase with I
ph
+ K
N .
I
E .
For a remote end terminal fault, this underreaching effect can be as high as 25%.
The distance protection zone reaches vary with the switching state of the parallel
line configuration. We consider the three most common operation modes:
1. Case 1: Parallel line out of service and earthed at both ends
2. Case 2: Parallel line switched off and not earthed or earthed only at one line
end
3. Case 3: Both lines in service.
The reach of the distance protection zone 1 will be different depending on the
operation condition of the parallel line.
Compensation of the mutual zero sequence impedance of parallel circuit can be
achieved by appropriate selection of zero-sequence compensation factor K
N
when
parallel line can be in service, out of service, or out of service and earthed at both
ends.
Five zone distance protection, mho characteristic function (ZMHPDIS) can
compensate for the influence of a zero sequence mutual coupling on the
measurement at single phase-to-earth faults in the following two ways, by using:
• Different setting values that influence the earth -return compensation for
different distance zones within the same group of setting parameters.
• Different groups of setting parameters for different operating conditions of a
protected multi circuit line.
1MRK 506 369-UEN B
Section 8
Impedance protection
Line distance protection REL670 2.2 IEC 247
Application manual