Investigations on some parameters influencing the current commutation in the circuit breakers

Abstract

The phenomenon of the commutation in a circuit breaker is the moment when the current switches from the nominal contact circuit to arcing contact circuit. Due to the difference of the impedance (resistance and inductance) between the two circuits, an arc appears between the contacts. So, this phenomenon can lead to two problems: the wear due to the commutation on the main contacts with bad issue if the main contacts could not withstand the nominal current and the particles of molten materials removed from the main contacts (pollution of the chamber with conductive particles). In this article we will analyze the influence of different parameters like materials nature, inductance and resistance of the circuits on the commutation. Calculations have been done and solution to improve the commutation has been proposed.

Electrical erosion test and condition assessment of SF 6 CB contact sets

“…5, the value of L a decreases after each opening operation due to arc erosion. However, a minimum value of L a should be assured for accurate commutation of the current from the main contacts to the arcing contacts during opening operation [16–20]. If the value of L a is lower than permissible value, the arc may burn continuously between main contacts even after the separation of arcing contacts.…”

“…The arcing contact length L a is an important diagnostic parameter for the condition assessment of CB contact sets for its influence to the normal function of distinguishing chamber (discussed in Section 4.2). In the previous works [16–18, 20], it is recommended that a minimum time for current commutation from main contact to arcing contact must be guaranteed. As a nearly constant contact speed was observed during the current commutation process in our tests, a minimum value of L a must be assured for proper opening operation of distinguishing chamber.…”