Schweitzer Engineering Laboratories SEL-421-4 - Page 1513

GL.21
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Glossary
Self-Test—SNTP
Self-Test
A function that verifies the correct operation of a critical device subsystem and
indicates detection of an out-of-tolerance condition. The relay has self-tests that
validate the relay power supply, microprocessor, memory, and other critical sys-
tems.
SELOGIC
Control Equation
A relay setting that allows you to control a relay function (such as a control
output) using a logical combination of relay element outputs and fixed logic
outputs.
SELOGIC
Expression Builder
A rules-based editor within the ACSELERATOR QuickSet software program for
programming SEL
OGIC control equations.
SELOGIC Math Variables
Math calculation result storage locations.
Sequencing Timers
Timers designed for sequencing automated operations.
Sequential Events
Recorder
A relay function that stores a record of the date and time of each assertion and
deassertion of every Relay Word bit in a list that you set in the relay. A Sequential
Events Recorder (SER) provides a useful way to determine the order and timing
of events of a relay operation.
SER
Sequential Events Recorder or the relay serial port command to request a report
of the latest 1000 sequential events.
Series-Compensated Line
A power line on which the addition of series capacitance compensates for
excessive inductive line impedance.
Settle/Settling Time
Time required for an input signal to result in an unvarying output signal within a
specified range.
Shot Counter
A counter that records the number of times a recloser attempts to close a circuit
breaker.
Shunt Admittance
The admittance resulting from the presence of a device in parallel across other
devices or apparatus that diverts some current away from these devices or
apparatus.
Shunt Capacitance
The capacitance between a network connection and any existing ground.
Shunt Current
The current that a parallel-connected high-resistance or high-impedance device
diverts away from devices or apparatus.
SIN Operator
Operator in math SELOGIC control equations that provides the sine function.
Single-CT Application
Tie breaker with only one CT available for busbar protection.
Single-Pole Trip
A circuit breaker trip operation that occurs when one pole of the three poles of a
circuit breaker opens independently of the other poles.
Single Relay Application
(Bus Protection)
Stations with as many as 21 per-phase CTs require only one SEL-487B. Stations
with more than 21 and as many as 54 per-phase CTs require three SEL-487B
relays.
SIR
Source-to-line impedance ratio.
SNTP
Simple Network Time Protocol. A network protocol for time synchronization.