6-4 Installation Date Code 20011026
SEL-321/321-1 Instruction Manual
Control Inputs
Relays come standard with control inputs that operate at the same voltage level as the relay
power source. Check the control voltage, labeled “LOGIC INPUT” on the rear-panel nameplate,
before making any connections. The control inputs are optically isolated “dry” circuits and are
not polarity sensitive. To assert the IN1 input, for example, you must apply control voltage to
the terminals assigned the IN1 input. Each input is individually isolated, and a terminal pair is
brought out for each input. There are no internal connections between control inputs. To assign
the functions of the control inputs, see Contact Input Assignments in Section 2: Specifications
and the SET G command in Section 3: Communications for more details. To verify operation
of the inputs, use the TARGET command (see Section 3: Communications). Several control
(or contact) input configurations are available; contact your local representative or the factory for
information.
Control Outputs
The standard control outputs are “dry” relay contacts rated for tripping duty. The optional
interrupting-duty control outputs are polarity dependent and are capable of interrupting high-
current, inductive loads. A metal-oxide varistor (MOV) protects each contact. Each output is
individually isolated, and a terminal pair is brought out for each output (Note: some I/O boards
share a common connection with adjacent contacts). There are no internal connections between
control outputs (except as noted previously). To assign the functions of the control outputs, see
Trip Logic in Section 2: Specifications and the SET L command in Section 3:
Communications for more details. To verify operation of the outputs, use the PULSE command
(see Section 3: Communications).
Alarm Contact Connection
The SEL-321 Relay includes an alarm output contact labeled “ALARM” on the rear panel. At
the factory, the alarm contact is configured to be closed for an alarm condition, and open for
normal operation. This is a “Form B” contact because it is closed when there is no power. To
invert the alarm output to close under normal conditions (“Form-A”), change the soldered jumper
associated with the alarm relay on the interface board where the alarm relay is located. See
Input/Output Connections later in this section for details.
Note: If the ALARM contact has a “+” symbol, it is polarity dependent and must be connected
accordingly.
The alarm contact asserts when power is disconnected from the SEL-321 Relay, the power
supply fails, or self-test diagnostics detect a failure. Self-test diagnostic failures include memory
failures, power supply failures, and invalid settings failures. See Self-Tests in Section 2:
Specifications and the STATUS command in Section 3: Communications for a discussion on
these failures and the alarm contact response to them. Also, the alarm contact is pulsed
when
Breaker or Level 2 access is established or when a setting change is accepted.
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