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Glossary
Glossary
Short-circuit breaking capacity
(Icn)
Breaking capacity for which prescribed conditions include a short-circuit at
the terminals of the switching device.
Short-circuit current
Overcurrent resulting from a short-circuit due to a fault or an incorrect
connection in an electric circuit.
Short-circuit making capacity
(Icm)
Making capacity for which prescribed conditions include a short-circuit at the
terminals of the switching device.
Short-circuit protective device
(SCPD)
Device intended to protect a circuit or parts of a circuit against short-circuit
currents by interrupting them.
Short-time delay
Any intentional delay in operation within the limits of the rated short-time
withstand current.
Short-time withstand current
(Icw)
Current that a circuit or a switching device in the closed position can carry
during a specified short time under prescribed conditions of use and behavior.
Shunt release (trip device)
A release (trip device) energized by a source of voltage.
NOTE: The source of voltage may be independent of the voltage of the main
circuit.
Take-over current (IB)
Current coordinate of the intersection between the time-current characteristics
of two overcurrent protective devices.
Thermal overload relay or release
(trip device)
Inverse time-delay overload relay or release (trip device) depending for
its operation (including its time-delay) on the thermal action of the current
flowing in the relay or release (trip device).
Time-current characteristic
Curve giving the time, e.g. pre-arcing time or operating time, as a function of
the prospective current, under stated conditions of operation.
Tripping (operation)
Opening operation of a mechanical switching device initiated by a relay or
release (trip device).
Ultimate short-circuit breaking
capacity (Icu)
A breaking capacity for which the prescribed conditions according to a
specified test sequence do not include the capability of the circuit breaker to
carry its rated current continuously.
Undervoltage relay or release
(trip device)
Relay or release (trip device) which permits a mechanical switching device
to open or close, with or without time-delay, when the voltage across the
terminals of the relay or release (trip device) falls below a predetermined
value.
Working voltage
Highest r.m.s. value of the AC or DC voltage across any particular insulation
which can occur when the equipment is supplied at rated voltage.
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