GE L90 Instruction Manual page 578
Ur series line current differential system
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9.6 FAULT LOCATOR
Table 9–40: TAP VOLTAGE DIFFERENCES USING TERMINAL DATA
VALUE
RELAY 1
LOC-REM1
0.66337 pu
LOC-REM2
0.0011344 pu
REM1-REM2
0.66289 pu
Applying the results of the table above to the equations in the previous sub-section, the algorithm arrives at the following:
•
Relay 1 determines remote 1 to tap.
•
Relay 2 determines local to tap.
•
Relay 3 determines remote 2 to tap.
As a result, the relays use the following data for further calculations.
Table 9–41: INPUT DATA FOR MAIN FAULT LOCATION
VALUE
RELAY 1
Fault segment
2
L
120 km
0.1517 pu 80.5°
Z
0.26558 pu 2.3467°
V
TAP
0.30072 pu –12.468°
V
1
2.9991 pu –69.256°
I
TAP
7.4992 pu –78.915°
I
FLT
The data above are effectively identical. The difference in current magnitudes results from different per-unit bases at the
three relays (1200 A, 1000 A, and 1600 A). The difference in impedances results from different CT and VT ratios at the
three relays.
The tap voltage is the actual voltage at the tap (0.26558 × 500 kV /
(0.30072 pu = 86.81 kV).
The tap current is the total feed from the tap towards the fault and is 2.9991 × 1200 A = 3.599 pu × 1000 A =
2.2494 pu × 1600 A = 3.599 kA. The fault current is 7.4992 pu × 1200 A = 8.999 pu × 1000 A = 5.6244 pu × 1600 A =
8.999 kA.
The data above results in the following fault locations.
•
Relay 1 fault location = 0.4173 pu or 0.4173 × 120 km = 50.0704 km from its remote terminal 1 (relay 2)
•
Relay 2 fault location = 0.4172 pu or 0.4172 × 120 km = 50.07 km from local terminal (relay 2)
•
Relay 3 fault location = 0.4173 pu or 0.4173 × 120 km = 50.0704 km from its remote terminal 2 (relay 2)
The actual fault location in this example was 50.00km from relay 2 as shown below.
9
9-54
RELAY 2
0.66334 pu
0.66286 pu
0.001137 pu
RELAY 2
1
120 km
0.1264 pu 80.5°
0.26559 pu 2.3468°
0.30072 pu –12.468°
3.599 pu –69.256°
8.999 pu –78.915°
channel 1
Relay 1
70 km
channel 2
Relay 3
channel 1
Figure 9–17: ACTUAL FAULT LOCATION
L90 Line Current Differential System
9 THEORY OF OPERATION
RELAY 3
0.0011344 pu
0.66289 pu
0.66337 pu
RELAY 3
3
120 km
0.2023 pu 80.5°
0.26558 pu 2.3467°
0.30072 pu –12.468°
2.2494 pu –69.256°
5.6244 pu –78.915°
3
= 76.67 kV). The V
voltage is the voltage at relay 2
1
AG
channel 1
Relay 2
50 km
120 km
channel 2
channel 2
831812A1.CDR
GE Multilin
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