Toshiba GR 200 Series, Instruction Manual

Page: 66 / 1563

6F2S1915 (0.46)
GRZ200 (Soft 031 & 032)
- 45 -
Figure 2.1-22 Z1S Quad element close-up fault (Offset action)
Operation of ZS for earth and multi-phase-faults
ZS can operate for any of the following faults: a phase-to-phase fault, phase-to-phase ground
fault, and a fault evolving into a multi-phase fault. To strengthen dependability in detecting
the multi-phase fault, it is possible to add the judgement of fault phase identifier. The fault
phase identifier consists of ZG elements. The judgement condition will be added when
On
is
set for setting [
Z*S-MSDET
]†. In order not to add the judgement in ZS, the user can set
Off
for
the setting.
†Note: It is recommended to set [
Z*S-MSDET
]=
On
in the instantaneous main protection
element only. Since operating condition of Z*S elements is increased by setting
On
, it is desirable to set
Off
in the backup protection easier to operate.
(iii)
Special characteristic in ZG
Earth fault compensation (Zero sequence current compensation)
On the detection of an earth fault, ZG requires a compensation function that corrects
measuring errors caused by the earth return of zero-sequence current. By using the
compensation function, the positive-sequence impedance to the fault point can be determined
precisely by the reactance element in the faulted phase. For a double-circuit line, the zero-
sequence current from the adjacent line is introduced to compensate for influences from zero-
sequence mutual coupling. Considering a case where the angle of the positive-sequence
impedance and the zero-sequence impedance differs, the distance protection function carries
out zero-sequence current compensation vectorially. We can see this case commonly in cable
circuits.
X
R
Z1S
ZS-DirRθ(R abscissa)
ZS-DirXθ(X ordinate)
ZS-Rθ
Z1S-R
Offset Quadrilateral characteristic during close-up fault
Static Quadrilateral characteristic