Date Code 20010719 701 Motor Protection Relay
Installation
Relay Connections
2.21
AC Voltage Connections (Relay Models 0701001X & 0701011X)
The SEL-701 Relay is available with optional voltage inputs and associated
metering, protection, and reporting functions. When your relay is equipped to measure
voltages, you can connect the relay in any of the following ways:
Three-phase, four-wire, wye-connected voltages, 0–300 Vac,
phase-to-neutral.
Three-phase, three-wire, open-delta connected voltages, 0–300 Vac,
phase-to-phase.
Single phase-to-neutral, 0–300 Vac.
Single phase-to-phase, 0–300 Vac.
Refer to Figure 2.6 on page 2.7 through Figure 2.9 on page 2.9 for examples of
each type of connection.
The connection method shown in Figure 2.8 on page 2.9 may allow you to use the
motor control voltage transformer to supply the phase-to-phase voltage for the relay. If
the control voltage transformer is connected to the bus for the protected motor and the
transformer is connected A-B, you can connect the ac control voltage to the relay
voltage inputs, as shown in Figure 2.8. Using this connection method, the relay voltage
measurement accuracy is dependent on the control voltage transformer ratio accuracy,
regulation, and loading. However, this accuracy may be satisfactory for your
application.
NOTE: The SEL-701 Relay calculates system frequency for the
over- and underfrequency elements using the A-N or A-B
voltage. When single-phase voltage is applied, make sure that
either the A-N or A-B voltage is connected to the relay.
The SEL-701 Relay tracks frequency from 20–70 Hz. In relay models 0701000X
and 0701010X, the relay tracks frequency using the current waveform, while relay
models 0701001X and 0701011X use the voltage applied to the VA channel to track
the frequency.
NOTE: SEL-701 Relays with voltage option will track frequency
only if voltage is applied to the relay.
EIA-232 Communication Cables
The SEL-701 Relay is equipped with 9-pin EIA-232 serial port connectors on the
front and rear panels. The front-panel port is always available for connection to a local
PC for setting entry or information download. Use SEL Cable C234A (pinout shown in
Connect Your PC to the Relay on page 6.3 in Section 6: ASCII Serial Port Operation)
or a null-modem cable for direct connection to a local PC serial port.
The rear-panel EIA-232 serial port is available when you disable Modbus™
protocol support by relay settings. You can connect the relay rear-panel port to a local
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