553 / 2017-05-14 12:16:35

Evaluation of Back to Back Capacitive Current Switching performance of 36kV VCB

15090

会场 > Switching Phenomena in Vacuum

Nowadays vacuum circuit breaker(VCB) is widely
used in medium voltage networks. Reactive power
existing in a network reduces the total amount of active
power and induces considerable voltage drops.
Therefore, capacitor banks are widely used for the
compensation of reactive power or for the stabilization
of voltage out of power quality reasons. Capacitor banks
are generally operated once or twice a day during the
peak load hours. They are used for disconnecting cables
or overhead lines with several 10 Amperes or for the
switching of capacitor banks with several 100 Amperes.
When capacitive load is connected to the power system,
pre-arc occurs as the gap between contacts become
smaller during closing operation. And the pre-arc heats
the contact surface locally and finally causes contact
welding. As the contacts are separated by opening
operation, the welded area on the contact surface would
be ruptured and the tips are left as a negative factor to
internal insulation of vacuum interrupter(VI) during
switching. Therefore, contact welding and rupture can
make worse contact surface.
In addition, the stress by a recovery voltage becomes
twice of system voltage due to the 90 degree lagging
load voltage under capacitive switching conditions.
Especially, the duty of back-to-back is the most severe
among capacitive current switching duties because the
amplitude of the inrush current is much higher than that
of single bank.
In this paper, 36kV back-to-back capacitive current
switching tests of test duty 2(BC2) with single phase
were performed with a series of separate making tests
followed by a series of CO tests due to limitations of the
test plant according to IEC standards 62271-100. The
test results were compared in terms of pre-arcing time,
break down voltage distribution, contact surface after
tests, contacting area, and field enhancement factor.