SEL-451 Data Sheet
Schweitzer Engineering Laboratories, Inc.
6
and other system operation conditions. A running aver-
age provides a stable prefault reference and adaptive tun-
ing learns and tunes out feeder ambient noise conditions.
Decision logic differentiates an HIF condition from other
system conditions such as switching operations and
noisy loads. As much as 40 minutes of high-impedance
fault activity is stored in high-resolution COMTRADE
format and a summary of HIF activity is available using
ASCII commands. View important high-impedance fault
data from available metering commands.
Six Independent Settings Groups
Increase Operation Flexibility
The relay stores six settings groups. Select the active
settings group by control input, command, or other pro-
grammable conditions. Use these settings groups to
cover a wide range of control contingencies. Selectable
settings groups make the SEL-451 ideal for applications
requiring frequent settings changes and for adapting the
bay to changing system conditions.
Selecting a group also selects logic settings. Program
group logic to adjust settings for different operating con-
ditions, such as station maintenance, seasonal operations,
emergency contingencies, loading, source changes, and
adjacent relay settings changes.
Combined Current for Protection
Flexibility
In traditional relays, when protecting a line fed from two
breakers, such as a breaker-and-a-half system or double-
breaker system, you needed to combine the CT inputs
before connecting these inputs to the relay. The SEL-451
can accept separate inputs from two separate CTs and
mathematically combine the currents. This allows col-
lecting separate current metering and breaker monitor
information for each breaker. Breaker monitoring func-
tions for two breakers are done within one relay. Individ-
ual breaker currents allow for breaker failure functions
on a per-breaker basis within the SEL-451. Breaker diag-
nostics are reported on a comparative basis allowing for
advanced, proactive troubleshooting.
Custom Control Capabilities
Customize control capabilities, adding stability and secu-
rity to your system.
➤
Use expanded SEL
OGIC
control equations to create
advanced stability enhancements such as VAR-
flow controlled time undervoltage load shedding.
➤
Combine frequency elements with voltage
supervision for added security with
underfrequency load-shedding systems.
Control Inputs and Outputs
The standard SEL-451 includes five independent and two
common inputs, two Form A and three Form C standard
interrupting outputs, and three Form A high-current
interrupting outputs. The following additional I/O boards
are currently available.
➤
Eight independent inputs, 13 standard Form A and
two standard Form C contact outputs.
➤
Eight independent inputs, eight high-speed, high-
current interrupting Form A contact outputs.
➤
Eight independent inputs, 13 high-current
interrupting Form A outputs and two standard
Form C contact outputs.
➤
Twenty-four inputs, six high-speed and two
standard Form A contact outputs.
Assign the control inputs for protection and control func-
tions, monitoring logic, and general indication. Each
control output is programmable using SEL
OGIC
control
equations. No additional I/O boards can be added to the
3U chassis; however, one board can be added to the 4U
chassis, and two additional I/O boards can be added to
the 5U chassis.
Figure 3
VAR-Flow Controlled Time Undervoltage Load
Shedding
Volt Drop pu
Trip Time
Time (s)
15
10
5
0
0
0.5
1
