Schweitzer Engineering Laboratories SEL-311B, Instruction Manual

Page: 429 / 602

Date Code 20011205 Testing and Troubleshooting 13-29
SEL-311B Instruction Manual
For:
° Ð =
° - Ð =
° Ð =
° Ð =
120 V 0 . 67 V
120 V 0 . 67 V
0 V 0 . 49 V
96 A 4 . 23 I
C
B
A
A
° Ð = ° Ð
=
° Ð =
97 . 83 1 ANG 1 Z 1
80 . 7 I
180 V 0 . 6 V
2
2
( )
[ ]
ohms 77 . 0 m 2 Z when F 2 Z ohms 77 . 0 c 2 Z
84 . 60
ohms 8 . 46
c 2 Z
80 . 7
* 96 80 . 7 • 97 . 83 1 • 180 6 Re
c 2 Z
2
= = =
=
° Ð ° Ð ° Ð
=
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-311B 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 E21P setting. Zones 1 and 2
are fixed forward. Zones 3 and 4 may be set forward or reverse. 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. All zones
also include time-delayed indication through elements M1PT, 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.
For general testing, use the instantaneous and time delayed elements that respond to any phase-
to-phase fault within a given zone such as M1P, M2P, etc. You can record more detailed and
specific test results using the instantaneous element associated with the faulted phase pair and
zone under test.
Phase Distance Element Supervisory Conditions
There are a number of supervisory conditions that must be fulfilled before the relay allows a
phase distance element to pick up. These supervisory conditions are described below.