U.4.4
SEL-421/SEL-421-1 Relay
User’s Guide
Date Code 20020501
Basic Relay Operations
Connecting and Applying Power
Connecting and Applying Power
Connect external power to the SEL-421 Relay to perform the initial checkout
and familiarization procedures in this section. For complete information on
power connections, see
Power Connections on page U.2.38 in the User’s
shows the portion of the relay rear panel where you connect
the power input.
Figure 4.2
Power Connection Area of the Rear Panel.
DANGER:
Contact with
instrument terminals can cause
electrical shock that can result in
injury or death.
!
Always attach a safety ground as the first connection you make to the
SEL-421 Relay. You must connect the grounding terminal (#Z31) labeled
“GND” on the rear panel to a rack frame ground or main station ground for
proper safety and performance.
You can order the SEL-421 Relay with one of three power supplies with
nominal operating voltages: 24/48 Vdc, 48/125 Vdc, and 125/250 Vdc. The
two higher voltage supplies, 48/125 Vdc and 125/250 Vdc use ac input and dc
input. The relay serial number label on the back of the relay lists voltage
ranges that encompass the nominal voltages.
shows the nominal
voltage inputs and power supply voltage ranges for dc input, and ac inputs if
applicable.
Use 16 AWG (1.5 mm
2
) wire (or heavier) to connect to the POWER
terminals. When you use a dc power source, you must connect the source with
the proper polarity, as indicated by the + (Terminal #Z29) and – (Terminal
#Z30) symbols on the power terminals. You can use ac input for the 48/125
Vdc power supply and the 125/250 Vdc power supply. The relay operates
from 30 to 120 Hz (nominal 50/60 Hz) when alternating current supplies the
POWER input.
Upon connecting power, you will see information on the front-panel LCD
(liquid crystal display) and the ENABLED LED (light-emitting diode) will
light. For complete information on the SEL-421 Relay front panel, see
Section 5: Front-Panel Operations in the User’s Guide
.
Terminal Z29 Terminal Z30
Terminal Z31
Serial
Number
Label
Table 4.1
Power Supply Voltage Inputs
Nominal DC
Voltage Input
DC Input Range
AC Input Range
(30—120 Hz)
24/48 Vdc
18–60 Vdc <35 W
N/A
48/125 Vdc
38–140 Vdc <35 W
120 Vac <120 VA
125/250 Vdc
85–300 Vdc <35 W
120/230 Vac <120 VA
Содержание SEL-421
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