Sel SEL-421 - Page 291

GL.5
Date Code 20020501 SEL-421/SEL-421-1 Relay
Glossary
Common Class Components—CTR
Common
Class Components
Composite data objects that contain instances of UCA standard data types.
Common Inputs
Relay control inputs that share a common terminal.
Common Time Delay
Both ground and phase distance protection follow a common time delay on
pickup.
Common Zone Timing
Both ground and phase distance protection follow a common time delay on
pickup.
Communications Protocol
A language for communication between devices.
Communications-Assisted
Tripping
Circuit breaker tripping resulting from the transmission of a control signal
over a communications medium.
Comparison
Boolean SELOGIC control equation operation that compares two numerical
values. Compares floating-point values such as currents, total counts, and
other measured and calculated quantities.
COMTRADE
Abbreviation for Common Format for Transient Data Exchange. The
SEL-421 Relay supports the IEEE Standard Common Format for Transient
Data Exchange (COMTRADE) for Power Systems, IEEE C37.111–1999.
Conditioning Timers
Timers for conditioning Boolean values. Conditioning timers either stretch
incoming pulses or allow you to require that an input take a state for a certain
period before reacting to the new state.
Contact Input
See Control input.
Contact Output
See Control output.
Coordination Timer
A timer that delays an overreaching element so that a downstream device has
time to operate.
Control Input
Relay inputs for monitoring the state of external circuits. Connect auxiliary
relay and circuit breaker contacts to the control inputs.
Control Output
Relay outputs that affect the state of other equipment. Connect control outputs
to circuit breaker trip and close coils, breaker failure auxiliary relays,
communications-assisted tripping circuits, and SCADA systems.
COS Operator
Operator in math SELOGIC control equations that provides the cosine
function.
Counter
Variable or device such as a register or storage location that either records or
represents the number of times an event occurs.
Cross-country fault
A cross-country fault consists of simultaneous separate single phase-to-
ground faults on parallel lines.
CT
Current transformer.
CT Subsidence Current
Subsidence current appears as a small exponentially decaying dc current with
a long time constant. This current results from the energy trapped in the CT
magnetizing branch after the circuit breaker opens to clear a fault or interrupt
load.
CTR
Current transformer ratio.