U.2.38
SEL-421/SEL-421-1 Relay
User’s Guide
Date Code 20020501
Installation
Connection
Power Connections
The terminals labeled POWER on the rear panel (#Z29 and #Z30) must
connect to a power source that matches the power supply characteristics that
your SEL-421 Relay specifies on the rear-panel serial number label. (See
Power Supply on page U.1.11 in the User’s Guide
, for complete power input
specifications.) For the relay models that accept dc input, the serial number
label specifies dc with the symbol shown in
.
NOTE:
The combined voltages
applied to the POWER and MONITOR
terminals must not exceed 600 V (rms
or dc).
The POWER terminals are isolated from chassis ground. Use 16 AWG (1.5
mm
2
) size or heavier wire to connect to the POWER terminals. Connection to
external power must comply with IEC 947-1 and IEC 947-3.
Place an external switch, circuit breaker, or overcurrent device in the POWER
leads for the SEL-421 Relay; this device must interrupt both the hot (H) and
neutral (N) power leads. The maximum current rating for the power
disconnect circuit breaker or overcurrent device (fuse) must be 20 A. Be sure
to locate this device within 9.8 feet (3.0 m) of the relay.
Operational power is internally fused by power supply fuse F1.
the SEL-421 Relay power supply fuse requirements. Be sure to use fuses that
comply with IEC 127-2.
You can order the SEL-421 Relay with one of three operational power input
ranges listed in
. Each of the three supply voltage ranges represents a
power supply ordering option. As noted in
, model numbers for the
relay with these power supplies begin 04210
n
, where
n
is 2, 4, or 6
,
to indicate
low, middle, and high voltage input power supplies, respectively. Note that
each power supply range covers two widely used nominal input voltages. The
SEL-421 Relay power supply operates from 30 Hz to 120 Hz when ac power
is used for the POWER input.
The SEL-421 Relay accepts dc power input for all three power supply models.
The 48/125 Vdc supply also accepts 120 Vac; the 125/250 Vdc supply also
accepts 120/240 Vac. When connecting 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. When connecting an ac
power source, the + terminal #Z29 is hot (H), and the – terminal #Z30 is
neutral (N).
Each model of the SEL-421 Relay internal power supply exhibits low power
consumption and a wide input voltage tolerance. For more information on the
power supplies, see
Power Supply on page U.1.11 in the User’s Guide
Table 2.8
Fuse Requirements for the SEL-421 Relay Power Supply
Nominal
Power
Supply
Voltage
Rating
Power Supply
Voltage Range
Fuse F1
Fuse Description
Model
Number
24/48 V
18–60 Vdc
T6.3A
H250V
5x20 mm, time-lag, 6.3 A,
high break capacity, 250 V
042102
48/125 V
38–140 Vdc or
85–140 Vac
(30–120 Hz)
T3.15A
H250V
5x20 mm, time-lag, 3.15 A,
high break capacity, 250 V
042104
125/250 V
85–300 Vdc or
85–264 Vac
(30–120 Hz)
T3.15A
H250V
5x20 mm, time-lag, 3.15 A,
high break capacity, 250 V
042106
Summary of Contents for SEL-421
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