U.2.42
SEL-421 Relay User’s Guide Date Code 20090715
Installation
Connection
Connectorized
For the Connectorized SEL-421, order the wiring harness kit, SEL-WA0421.
The wiring harness contains four prewired connectors for the relay current and
voltage inputs.
You can order the wiring harness with various wire sizes and lengths. Contact
your local Technical Service Center or the SEL factory for ordering
information.
Perform the following steps to install the wiring harness:
Step 1. Plug the CT shorting connectors into terminals #Z01 through
#Z06 for the IW inputs, and #Z07 through #Z12 for the IX inputs,
as appropriate.
Odd-numbered terminals are the polarity terminals.
Step 2. Secure the connector to the relay chassis with the two screws
located on each end of the connector.
When you remove the CT shorting connector, pull straight
away from the relay rear panel.
As you remove the connector, internal mechanisms within the
connector separately short each power system current
transformer.
You can install these connectors in only one orientation.
Step 3. Plug the PT voltage connectors into terminals #Z13 to #Z18 for
the VY inputs, and #Z19 to #Z24 for the VZ inputs, as
appropriate.
Odd numbered terminals are the polarity terminals. You can
install these connectors in only one orientation.
Control Circuit
Connections
You can configure the SEL-421 with many combinations of control inputs and
control outputs. See Main Board I/O on page U.2.10 and I/O Interface Boards
on page U.2.12 for information about I/O configurations. This subsection
provides details about connecting these control inputs and outputs. Refer to
Figure 2.2, Figure 2.10, and Figure 2.14 for representative rear-panel screw
terminal connector locations.
Control Inputs
NOTE: The combined voltages
applied to the INnnn and OUTnnn
terminals must not exceed 600 V
(rms or dc).
Table 2.3 lists the control inputs available with the SEL-421, and notes that
some are Direct-Coupled, and some are Optoisolated.
Direct-Coupled
Direct-coupled control inputs are polarity sensitive. These inputs use direct-
coupled circuitry, and have terminal markings to indicate polarity: a + mark
appears for each input. Connect the positive sense of the control input to the +
terminal. Although you cannot damage these inputs with a reverse polarity
connection, a reverse polarity connection will cause the relay internal A/D
converter to measure the input voltage incorrectly and the relay will no longer
detect input changes (see Control Inputs on page U.2.5).
Note that the Main Board A I/O control inputs have one set of two inputs that
share a common input leg. These inputs are IN106 and IN107 found on terminals
#A30, #A31, and #A32.
Relay misoperation can result from
applying other than specified
secondary voltages and currents.
Before making any secondary circuit
connections, check the nominal
voltage and nominal current
specified on the rear-panel
nameplate.
Courtesy of NationalSwitchgear.com
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