Date Code 20010731 Installation 2-11
SEL-352-1, -2 Instruction Manual
Connections
Frame Ground
For safety and performance, ground the relay chassis at terminal GND (Z27). Connectorized
relays provide a 0.250-inch-by-0.023-inch spade connector for this connection. The grounding
terminal of either relay version connects directly to relay chassis ground.
Power Supply
Connect rear-panel terminals marked + (Z25) and – (Z26) to a source of control voltage. Control
power passes through these terminals to a fuse(s) and to the switching power supply. The
control power circuitry is isolated from the frame ground. The 24/48 V power supply is polarity
sensitive. Refer to Section 1: Introduction and Specifications for power supply voltage ranges.
Current Transformer Inputs
Connect current inputs to the set of current input terminals. Note that the CT shorting connector
providing current connections to Connectorized relays installs in only one orientation. Note also
that the current input terminals on both terminal block and Connectorized relays have a mark at
one terminal per phase to indicate polarity. Each current input is independent of the other two
inputs.
Note: When installing CT shorting connectors, ensure that you secure each connector to the
relay chassis with the screws at each connector end. When removing a CT shorting
connector, pull it straight away from the relay rear panel. Removing a shorting
connector causes internal mechanisms within the connector to individually short out
each power system current transformer.
Potential Transformer Input
The two three-phase sets of voltage inputs are internally wye-connected voltage inputs. Each
three-phase set of voltages is independent of the other.
The relay requires difference-voltage potentials obtained from voltage transformers on both sides
of the circuit breaker for Scheme 1 of the flashover protection logic and the thermal protection
logic.
Optoisolated Inputs
Connect control input wiring to the six standard inputs IN101–IN106 and to any of the I/O board
optoisolated inputs IN201–IN208 you need for your application.
All control inputs are dry optoisolated inputs and are not polarity dependent. Specify a
nominal-rated control voltage of 48, 110, 125, or 250 Vdc for level sensitive and 24 Vdc for
nonlevel sensitive when ordering. To assert an input, apply nominal-rated control voltage to the
terminals assigned to that input. A terminal pair is brought out for each input. Refer to the
General Specifications in Section 1: Introduction and Specifications for optoisolated input
ratings. There are no internal connections between inputs. ON and OFF values are normally
within one volt of each other, in the indicated range.
To Next Page
