ABB REL 356

ABB REL 356 Current Differential Protection
5-15
Testing
5. Forward External Faults
For forward Zone 2 Phase-Ground External faults use the Table 5-5 of voltages and currents. In each case apply the 3-
phase voltage to the relay system first then suddenly apply the currents listed. The relay system should not trip as
these faults are beyond the reach of the Zone 2 ground units.
Table 5-5. Zone 2 Phase-Ground Forward External Faults: Z2GF = 4.5 Ohms Z2GR = 4.5 Ohms
Volts
∠
Angle
I
Amps
∠
Angle
Fault Z
Ohms
∠
Angle
Relay System
Operation
AG at MTA 110% of reach fault
Va = 30
∠
0 Ia = 3.6
∠
-75 (285) 4.95
∠
75
Vb = 69
∠
-120 (240) Ib = 0
Vc = 69 ∠ -240 (120) Ic = 0
No trips
AG at MTA –45˚ 110% of reach fault
Va = 30
∠
0 Ia = 3.6
∠
-30 (330) 4.95
∠
30
Vb = 69 ∠ -120 (240) Ib = 0
Vc = 69 ∠ -240 (120) Ic = 0
No trips
AG at MTA +45˚ 110% of reach fault
Va = 30 ∠ 0 Ia = 3.6 ∠ -120 (240) 4.95 ∠ 120
Vb = 69
∠
-120 (240) Ib = 0
Vc = 69
∠
-240 (120) Ic = 0
No trips
BG at MTA 110% of reach fault
Va = 69
∠
0 Ia = 0 4.95
∠
75
Vb = 30 ∠ -120 (240) Ib = 3.6 ∠ -195 (165)
Vc = 69
∠
-240 (120) Ic = 0
No trips
BG at MTA –45˚ 110% of reach fault
Va = 69 ∠ 0 Ia = 0 4.95 ∠ 30
Vb = 30
∠
-120 (240) Ib = 3.6
∠
-150 (210)
Vc = 69
∠
-240 (120) Ic = 0
No trips
BG at MTA +45˚ 110% of reach fault
Va = 69
∠
0 Ia = 0 4.95
∠
120
Vb = 30
∠
-120 (240) Ib = 3.6
∠
-240 (120)
Vc = 69
∠
-240 (120) Ic = 0
No trips
CG at MTA 110% of reach fault
Va = 69 ∠ 0 Ia = 0 4.95 ∠ 75
Vb = 69
∠
-120 (240) Ib = 0
Vc = 30
∠
-240 (120) Ic = 3.6
∠
-315 (45)
No trips
CG at MTA –45˚ 110% of reach fault
Va = 69
∠
0 Ia = 0 4.95
∠
30
Vb = 69 ∠ -120 (240) Ib = 0
Vc = 30 ∠ -240 (120) Ic = 3.6 ∠ -270 (90)
No trips
CG at MTA +45˚ 110% of reach fault
Va = 69
∠
0 Ia = 0 4.95
∠
120
Vb = 69 ∠ -120 (240) Ib = 0
Vc = 30
∠
-240 (120) Ic = 3.6
∠
0
No trips