Date Code 20011026 Maintenance and Testing 7-17
SEL-321/321-1 Instruction Manual
Serial Communication Equipment Connections
A terminal or PC with communications software is necessary to make SEL
OGIC
®
control
equations setting changes and examine relay event reports. We recommend using a terminal
during relay testing. Figure 7.8 shows typical connections between a computer and the SEL-321
Relay Port 3. Complete details regarding serial communications with the relay may be found in
Section 3: Communications.
WARNING
!
Use only serial communications cables manufactured by SEL or built
to SEL specifications with the SEL-321 Relay. Damage to the relay or
your communication equipment may result from the use of incorrect
communication connections.
Figure 7.8: Communications Connections Between the SEL-321 Relay and a Terminal
TEST PROCEDURES
This section includes outline test procedures for overcurrent, directional, phase distance, and
ground distance elements included in the SEL-321 Relay. The procedures are general, so that
they may be applied to any specific element or zone.
Overcurrent Elements
The SEL-321 Relay includes phase, residual, negative-sequence, and positive-sequence
overcurrent elements. The type of overcurrent element under test determines the test connections
required. Some elements are supervised by directional elements or distance elements.
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