Important
Terms:
Rated voltage:
The rated
voltage is the maximum voltage (phase to phase), expressed in kV RMS, of the
system for which the equipment is intended.
It is also known as maximum system
voltage. (800 kV RMS)
Rated
insulation level:
The combination
of voltage values which characterizes the insulation of a circuit breaker with
regard to its capability to withstand dielectric stresses.
The rated value
given is valid for altitudes ≤1000 m above sea level. See nameplate.
Rated Lightning Impulse Withstand Level (LIWL):
The lightning impulse
test is performed with a standardized wave shape 1.2/50 µs for simulation of
lightning over-voltage.
The rated
Lightning Impulse Withstand Level (LIWL) indicates the required withstand level
phase-to-earth (phase-to-ground), between phases and across open contacts.
The
value is expressed in kV as a peak value. (2100 kV)
BIL (Basic
Insulating Level) is an old expression but means the same as LIWL.
Rated Power
Frequency Withstand Voltage:
This test is to
show that the apparatus can withstand the power frequency over-voltages that
can occur.
The Rated Power
Frequency Withstand voltage indicates the required withstand voltage
phase-to-earth (phase-to-ground), between phases and across open contacts.
The
value is expressed in kV rms. (870 kV RMS)
Rated Switching Impulse Withstand Level(SIWL):
The switching impulse voltage is generated in conventional impulse voltage generators at the laboratories. The wave shape 250/2500 µs simulate switching over-voltage.
The rated
Switching Impulse Withstand Level (SIWL) indicates the required withstand level
phase-to-earth (phase-to-ground), between phases and across open contacts.
The
value is expressed in kV as a peak value. (1550 kV)
The switching impulse is required
only for voltages ≥300 kV.
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