10-56
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
FAULT LOCATOR
CHAPTER 10: THEORY OF OPERATION
10
Figure 10-17: Relay connections for multi-ended fault locator example
The following settings are entered into the relays by you. These values are calculated in secondary ohms as shown in the
following tables.
Table 10-40: Line impedance settings (all angles are 80.5°)
Assume that the following signals are measured by the relays when the fault locator is triggered.
Table 10-41: Relay measurements (physical inputs)
These measurements are shown as follows in per-unit values of the CT and VT nominal of the 87L source.
Table 10-42: Relay measurements (per-unit values)
When subjected to the expanded Clarke transform in the previous section, the local currents yield the following values (in
relay per-unit values):
•
Relay 1: 1.3839 pu
∠
–84.504°
•
Relay 2: 5.4844 pu
∠
–85.236°
•
Relay 3: 1.2775 pu
∠
–56.917°
When subjected to the expanded Clarke transform in the previous section, the local voltages yield the following values (in
per-unit values of the nominal primary phase-to-ground voltage):
Value
Relay 1
Relay 2
Relay 3
Local to tap
1.0219 sec. ohms (relay 1 to tap in
relay 1 secondary ohms)
6.0833 sec. ohms (relay 2 to tap in
relay 2 secondary ohms)
1.0707 sec. ohms (relay 3 to tap in
relay 3 secondary ohms)
Remote 1 to tap
1.7520 sec. ohms (relay 2 to tap in
relay 1 secondary ohms)
3.5483 sec. ohms (relay 1 to tap in
relay 2 secondary ohms)
1.3626 sec. ohms (relay 1 to tap in
relay 3 secondary ohms)
Remote 2 to tap
0.8030 sec. ohms (relay 3 to tap in
relay 1 secondary ohms)
2.7883 sec. ohms (relay 3 to tap in
relay 2 secondary ohms)
2.3360 sec. ohms (relay 2 to tap in
relay 3 secondary ohms)
Value
Relay 1
Relay 2
Relay 3
F1
10.64 A
∠
–87.5°
8.592 A
∠
–88.5°
9.652 A
∠
–43°
F2
1.652 A
∠
88.9°
1.273 A
∠
78.6°
5.201 A
∠
–99°
F3
1.66 A
∠
–31.2°
1.614 A
∠
–43°
6.269 A
∠
139.3°
F5
52.71 V
∠
0.8°
76.943 V
∠
24.579°
49.6 V
∠
10.1°
F6
58.21 V
∠
–121.4°
86.321 V
∠
–98.052° 57.1 V
∠
–115.6°
F7
58.93 V
∠
121.9°
78.795 V
∠
137.27°
59.12 V
∠
130.8°
Value
Relay 1
Relay 2
Relay 3
IA
2.128 pu
∠
–87.5°
8.592 pu
∠
–88.5°
1.9304 pu
∠
–43°
IB
0.3304 pu
∠
88.9°
1.273 pu
∠
78.6°
1.0402 pu
∠
–99°
IC
0.332 pu
∠
–31.2°
1.614 pu
∠
–43°
1.2538 pu
∠
139.3°
VA (VAB)
0.91304 pu
∠
0.8°
0.92335 pu
∠
24.579° 0.85917 pu
∠
10.1°
VB (VBC)
1.0083 pu
∠
–121.4°
1.0359 pu
∠
–98.052° 0.98909 pu
∠
–115.6°
VC (VCA)
1.0208 pu
∠
121.9°
0.94557 pu
∠
137.27° 1.0241 pu
∠
130.8°