Date Code 20011026 Maintenance and Testing 7-31
SEL-321/321-1 Instruction Manual
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ohms45.5m2ZwhenRT2Zohms45.5c2Z
21.1
ohms6.6
c2Z
10.1
*9610.1•97.831•1806Re
c2Z
I
*I•ANG1Z1•VRe
c2Z
2
2
2
22
===
=
°∠°∠°∠
=
°∠
=
Equation 7.2
For:
°∠=
°−∠=
°∠=
°∠=
120V0.67V
120V0.67V
0V0.49V
96A4.23I
C
B
A
A
°∠=°∠
=
°∠=
97.831ANG1Z1
80.7I
180V0.6V
2
2
()
[]
ohms77.0m2ZwhenF2Zohms77.0c2Z
84.60
ohms8.46
c2Z
80.7
*9680.7•97.831•1806Re
c2Z
2
===
=
°∠°∠°∠
=
Note: As you perform this test, other protection elements may assert, causing the relay to
close other output contacts and assert relay targets. This is normal and is not a cause
for concern.
Phase Mho Distance Elements
The SEL-321 Relay includes up to four zones of mho phase distance protection. Enable the
number of phase distance zones you would like to apply using the PMHOZ setting. You may set
the phase distance elements to reach in the forward or reverse direction. The reach and direction
of each zone is independent from the other zones. When a zone of phase distance protection is
set to reach in one direction, the ground distance elements associated with that zone must be set
to reach in the same direction. Reach is set in secondary ohms. The phase distance element
maximum reach angle is always equal to the angle of Z1ANG.
Each zone has an instantaneous indication. For example, the M3P element asserts without
intentional time delay for A-B, B-C, or C-A faults within the Zone 3 characteristic. Zones 2, 3,
and 4 also include time delayed indication through elements M2PT, M3PT, and M4PT. In
addition, the relay provides an instantaneous indication for each individual phase-to-phase
distance element. For example, the MAB1, MAB2, MAB3, and MAB4 elements provide
instantaneous indication of A-B phase faults in each zone.
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