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example to calculate and determine trip
currents; set the relay as follows:
Z1P = ZIG = 4.5
Z2P = Z2G = 6.0
Z3P = Z3G = 9.0
PANG = GANG = 75 ο
a. Single-Phase-to-Ground Fault
Use the equation in Step 10, and the following input
voltages:
∠
V
=
45 0°
=
V
AN
LN
∠
V
=
70
–
120°
BN
∠
V
=
70 120°
CN
The single-phase trip currents for Zone 1, Zone 2,
and Zone 3 at the maximum torque angle
(
∠
)
I
75°
are 6.0A, 4.5A and 3.0A, respectively.
A
b. Phase-to-Phase Fault
Use the T-connection and the equation in step 13.
Apply the following input voltages:
1
∠
-- - V
V
=
18 0°
=
AN
2
∠
V
=
18
–
180°
=
BN
∠
V
=
105 90°
CN
The single-phase trip currents for Zone 1, Zone 2
and Zone 3 at the maximum torque angle
(
∠
)
I
–
75°
are 4A, 3A and 2A, respectively.
AB
c. Three-Phase Fault
Use the equation in Step 12 with the following input
voltages:
∠
V
=
27 0°
=
V
AN
LN
∠
V
=
27
–
120°
BN
∠
V
=
27 120°
CN
The three-phase trip currents for Zone 1, Zone 2 and
Zone 3 at the maximum torque angles
∠
∠
I
–
75°, I
–
195°, I
A
B
T1 = 0
T2P = T2G
= 0.2
T3P = T3G
= 0.3
ZR
= 3
F
1
-- - V
F
2
∠
+45°
C
should be 6.0A, 4.5A and 3.0A, respectively.
1.1.8
Instantaneous Overcurrent (High-Set
Trip)
Step 20. Using the SETTINGS mode, change the
following settings:
ITP = 10A
ITG = 5A
NOTE: The High-Set ground overcurrent (ITG)
and phase overcurrent (ITP) are super-
vised by Forward Directional Ground
unit (FDOG) and Forward Directional
Phase unit (FDOP), respectively. In or-
der to test the High-Set trip, the 3φ
voltages are necessary as directional
reference. The ITG and ITP will automat-
ically become non-directional over-
current units if the setting of LOPB is
YES and at least one input voltage is
zero volts (e.g., LOPB = YES in the me-
tering mode).
Step 21. Using Figure A-1, configuration #1, to
connect currents and voltages, apply AG fault as
shown in Step 1.1.3. The MDAR should trip at I
= 5 Amps ± 5 % with a target of ITG-AG. For re-
versed fault, apply 8A reversed fault current (i.e.,
I
leads Van by 135° for Y-connection, or 105° for
a
T-connection). The relay should not trip.
Step 22. Using Figure A-3, to connect currents and
voltages, apply AB fault as shown in Step 1.1.5.
The MDAR should trip at Iab = 10 Amps ±5%,
with a target of ITP - AB. Apply a 15A reversed
fault current (i.e., I
leads V
a
nection or 105° for T-connection). The relay
should not trip.
1.1.9
Ground Backup (GB) Test
Step 23. Use the SETTINGS mode and change the
following settings:
• ITP
= "OUT"
• ITG
= "OUT"
• GBCV
= CO-8
• GBPU
= .5
• GDIR
= "NO"
I.L. 40-385.5
LOPB = "NO"
Z3G
= "OUT"
Z3P
= "OUT"
a
by 135° for Y-con-
ab
A-5
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