Toshiba GRZ100 B Series, Instruction Manual

Page: 137 / 447

⎯
136
⎯
6 F 2 S 0 8 4 6
•
zone F trip
•
zone 1 extension trip
•
external main protection trip
2.7.4 Displaying Location
The measurement result is stored in the "Fault record" and displayed on the LCD of the relay front
panel or on the local or remote PC. For displaying on the LCD, see Section 4.2.3.1.
In the two-terminal line, the location is displayed as a distance (km) and a percentage (%) of the
line length.
“
∗
OB” and “
∗
NC” may display after the location result. These mean the followings:
∗
OB: Fault point is over the boundary.
∗
NC: Fault calculation has not converged.
In case of a fault such as a fault duration time is too short, the fault location is not displayed and the
"---" marked is displayed.
2.7.5 Setting
The setting items necessary for the fault location and their setting ranges are shown in the table
below. The settings of R0m and X0m are only required for the double circuit lines. The reactance
and resistance values are input in expressions on the secondary side of CT and VT.
When there are great variations in the impedance of each phase, equation (4) is used to find the
positive sequence impedance, zero sequence impedance and zero sequence mutual impedance,
while equation (5) is used to find imbalance compensation factors Kab to Ka.
When variations in impedance of each phase can be ignored, the imbalance compensation factor is
set to 100%.
Z1 = {(Zaa + Zbb + Zcc) − (Zab + Zbc + Zca)}/3
Z0 = {(Zaa + Zbb + Zcc) + 2(Zab + Zbc + Zca)}/3 (4)
Z0m = (Zam + Zbm + Zcm)/3
Kab = {(Zaa + Zbb)/2
− Zab}/Z1
Kbc = {(Zbb + Zcc)/2 − Zbc}/Z1
Kca = {(Zcc + Zaa)/2 − Zca}/Z1 (5)
Ka = {Zaa − (Zab + Zca)/2}/Z1
Kb = {Zbb − (Zbc + Zab)/2}/Z1
Kc = {Zcc − (Zca + Zab)/2}/Z1
The scheme switch [FL-Z0B] is used for zero sequence compensation in double circuit line.
The switch [FL-Z0B] is set to "OFF" when the current input to the earth fault measuring element is
compensated by residual current of the parallel line. When not, the switch [FL-Z0B] is set to "ON"
and Z0B-L and Z0B-R are set instead of R0m and X0m as follows:
Z0B-L = zero sequence back source impedance at local terminal
Z0B-R = zero sequence back source impedance at remote terminal
In double circuit line, however, it is recommended that the current input compensated by residual