ABB REL 356 Current Differential Protection
5-21
Testing
15.
Reverse External Faults
For reverse Zone 3 Phase-Phase External faults use the Table 5-15 of voltages and currents. In each case apply the 3-
phase voltage to the relay system first then suddenly apply the currents listed. In each case the relay system should
not trip as these faults are reverse direction from the PANG setting.
Table 5-15. Zone 3 Phase-Phase Reverse External Faults: Z3P = 7.0 Ohms
Volts
∠
Angle
I
Amps
∠
Angle
Fault Z
Ohms
∠
Angle
Relay System
Operation
AB at MTA -180˚ 50% of reach fault
Va = 17.3
∠
0
Ia = 4.28
∠
-225 (135)
3.5
∠
-105
Vb = 17.3
∠
-120 (240)
Ib = 4.28
∠
-45 (315)
Vc = 69
∠
-240 (120)
Ic = 0
No Trips
BC at MTA -180˚ 50% of reach fault
Va = 69
∠
0
Ia = 0
3.5
∠
-105
Vb = 1.73
∠
-120 (240)
Ib = 4.28
∠
-345 (15)
Vc = 1.73
∠
-240 (120)
Ic = 4.28
∠
-165 (195)
No Trips
CA at MTA -180˚ 50% of reach fault
Va = 17.3
∠
0
Ia = 4.28
∠
-285 (75)
3.55
∠
-105
Vb = 69
∠
-120 (240)
Ib = 0
Vc = 17.3
∠
-240 (120)
Ic = 4.28
∠
-105 (255)
No Trips
3-Phase Units
To calculate the fault impedance seen by the relay system the following formula applies:
Z fault =
Vxg
Ixg
--------------
where x is either phase a, b, and c phases.
The above formula is rigorous and general. However, if a quick approximation of the minimum trip current required at
different angles (
q
) is desired, the following formula applies:
V
XG
Z2P (cos (PANG -
q))
----------------------------------------------------------
lxg =
where x is either phase a, b, and c phases.
Summary of Contents for REL 356
Page 23: ...ABB REL 356 Current Differential Protection 1 10 Product Overview and Specifications ...
Page 83: ...ABB REL 356 Current Differential Protection 3 36 Settings and Application ...
Page 127: ...ABB REL 356 Current Differential Protection 5 28 Testing ...
Page 186: ...LINE SECTIONALIZING USING A PLC AND ABB PROTECTIVE RELAY Page 49 of 53 ...
Page 187: ...LINE SECTIONALIZING USING A PLC AND ABB PROTECTIVE RELAY Page 50 of 53 ...
Page 188: ...LINE SECTIONALIZING USING A PLC AND ABB PROTECTIVE RELAY Page 51 of 53 ...
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