GL.7
Date Code 20171006 Instruction Manual SEL-400 Series Relays
Glossary
Control Input—Data Object
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.
Coordination Timer
A timer that delays an overreaching element so that a downstream device has
time to operate.
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.
Current Compensation
Adjustment of the current signals to nullify any standing unbalance current.
Current
Reversal Guard Logic
Under this logic, the relay does not key the transmitter and ignores reception of a
permissive signal from the remote terminal when a reverse-looking element
detects an external fault.
Current
Transformer Saturation
The point of maximum current input to a CT; any change of input beyond the
saturation point fails to produce any appreciable change in output.
CVT
Capacitive voltage transformer that uses a capacitive voltage divider to reduce
transmission voltage to a level safe for metering and relaying devices. See CCVT.
CVT Transient Blocking
Logic that prevents transient errors on capacitive voltage transformers from
causing false operation of Zone 1 mho elements.
CVT Transient
Detection Logic
Logic that detects transient errors on capacitive voltage transformers.
Data Attribute
In the IEC 61850 protocol, the name, format, range of possible values, and
representation of values being communicated.
Data Bit
A single unit of information that can assume a value of either logical 0 or
logical 1 and can convey control, address, information, or frame check sequence
data.
Data Class
In the IEC 61850 protocol, an aggregation of classes or data attributes.
Data Label
The identifier for a particular data item.
Data Object
In the IEC 61850 protocol, part of a logical node representing specific
information (status or measurement, for example). From an object-oriented point
of view, a data object is an instance of a data class.
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