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U.2.6
SEL-421 Relay
User’s Guide
Date Code 20090715
Installation
Shared Configuration Attributes
The control input accuracy is
±
5 percent of the applied signal plus
±
3 Vdc.
The maximum voltage input is 300 Vdc, and the relay samples the control
inputs 16 times per cycle. See
Raw and Filtered Data on page A.3.2
Optoisolated
The SEL-421 Main Board B inputs, and the inputs on the optional I/O
interface boards (INT2, INT3, INT4, INT7, or INT8 I/O boards—see
), are fixed pickup threshold, optoisolated, control
inputs. The pickup voltage level is determined for each board at ordering time.
Use these inputs for monitoring change-of-state conditions of power system
equipment. These high-isolation control inputs are ground-isolated circuits
and are not polarity sensitive. In other words, the relay will detect input
changes with voltage applied at either polarity.
Inputs can be independent or common. Independent inputs have two separate
ground-isolated connections, with no internal connections among inputs.
Common inputs share one input leg in common; all input legs of common
inputs are ground isolated. Each group of common inputs is isolated from all
other groups.
Nominal current drawn by these inputs is 8 mA or less with 6 voltage options
covering a wide range of voltages, as listed in
.
You can debounce the control input pickup delay and dropout delay separately
for each input, or you can use a single debounce setting that applies to all the
contact input pickup and dropout times—see
Global Settings on page R.10.4
.
AC Control Signals
Optoisolated control inputs can be used with ac control signals, within the
ratings shown in
. Specific pickup and dropout
time-delay settings are required to achieve the specified ac thresholds, as
shown in
.
It is possible to mix ac and dc control signal detection on the same interface
board with optoisolated contact inputs, provided that the two signal types are
not present on the same set of combined inputs. Use standard debounce time
settings (usually the same value in both the pickup and dropout settings) for
the inputs being used with dc control voltages.
220
176 Vdc
80%
250
200 Vdc
80%
a
Applies to IN1nnP, IN2nnP, IN3nnP when global setting EICIS := Y.
Table 2.1
Recommended Control Input Pickup Settings
(Sheet 2 of 2)
Substation DC Voltage
Level
Recommended Settings
Pickup: GINP
a
Dropout: GINDF
NOTE:
The SEL-421 Main Board B
and the INT2, INT3, INT4, INT7, and
INT8 I/O interface boards have
optoisolated contact inputs that can
be used in either polarity.
NOTE:
Only the optoisolated
control inputs can be used to detect
ac control signals. Direct-coupled
control inputs can only be used with
dc control signals.
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