U.2.7
Date Code 20090715
User’s Guide
SEL-421 Relay
Installation
Shared Configuration Attributes
The recognition times listed in
are only valid when:
➤
The ac signal applied is at the same frequency as the power
system.
➤
The signal is within the ac threshold pickup ranges defined in
Optoisolated (use with ac or dc signals) on page U.1.14
➤
The signal contains no dc offset.
The SEL-421 samples the optoisolated inputs 16 times per cycle—see
and Filtered Data on page A.3.2
Control Outputs
I/O control outputs from the relay include Standard outputs, Hybrid (high-
current-interrupting) outputs, and Fast Hybrid (fast high-current-interrupting)
outputs. Fast Hybrid outputs are available only on the optional INT4, INT5, or
INT8 I/O interface boards. An MOV (metal-oxide varistor) protects against
excess voltage transients for each contact. Each output is individually isolated,
except Form C outputs, which share a common connection between the NC
(normally closed) and NO (normally open) contacts.
The relay updates control outputs eight times per cycle. Updating of relay
control outputs does not occur when the relay is disabled. When the relay is
reenabled, the control outputs assume the state that reflects the present
protection processing.
Standard Control Outputs
The Standard control outputs are “dry” Form A contacts rated for tripping
duty. Ratings for Standard outputs are 30 A make, 6 A continuous, and 0.5 A
or less break (depending on circuit voltage). Standard contact outputs have a
maximum voltage rating of 250 Vac/330 Vdc. Maximum break time is 6 ms
(milliseconds) with a resistive load. The maximum pickup time for the
Standard control outputs is 6 ms.
shows a representative connection
for a Form A Standard control output on the main board I/O terminals.
Table 2.2
Required Settings for Use with AC Control Signals
a
a
First set Global setting EICIS := Y to gain access to the individual input pickup and dropout
timer settings.
Global Settings
Description
Entry
b
b
These are the only setting values that SEL recommends for detecting ac control signals.
Other values may result in inconsistent operation.
Relay Recognition Time
for AC Control Signal
state change
IN
nmm
PU
c
c
Where n is 1 for Main Board, 2 for Interface Board 1, and 3 for Interface Board 2; mm is
number of available contact inputs depending on the type of board.
Pickup Delay
0.1250 cycles
0.625 cycles maximum
(assertion)
IN
nmm
DO
Dropout Delay
1.0000 cycle
1.1875 cycles maximum
(deassertion)
NOTE:
EA certified relays do not
have MOV protected standard
output contacts.
NOTE:
You can use ac or dc circuits
with Standard control outputs.
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