Electrical contacts: classification and role in switchgear

Electrical contacts are critical components of high-voltage circuit breakers, switchgear, disconnectors and grounding switches, and their performance directly affects the quality and service life of these appliances. As the core parts of medium- and high-voltage switchgear, they perform both interruption and conduction, and are widely used in high-voltage load switches, SF6 circuit breakers, on-load tap-changers, and large breaking-capacity disconnectors and grounding switches.

Arc contacts in SF6 circuit breakers

In high- and ultra-high-voltage SF6 circuit breakers, the arc contact is currently made mainly of CuW (tungsten-copper) alloy. Earlier designs used a finger-spring arc contact structure, but it was complex, the spring heated up in service, and its reliability deteriorated.

Main types of electrical contacts

Electrical contacts are divided mainly into rivet contacts, powder metallurgy contacts and sheet contacts. Rivet contacts are used mainly in relays, contactors, small switches and thermostats. Sheet contacts are used mainly in contactors, circuit breakers, thermostats and intelligent switches. Powder metallurgy contacts are used mainly in circuit breakers, line-protection switches, fault-current protection switches, leakage-protection switches and sliding brushes.

High-current spring finger contacts

Responding to the connector industry's growing demand for high-current connectors, SISE has developed a bidirectional coil spring finger (SiS) and a single-turn spring finger that form multiple columnar contact points, up to more than 300 in a single ring. The contacts provide a service life of more than 100,000 cycles, with contact current density and temperature rise approaching those of a transmission cable, and an insertion and withdrawal force of about 10 N.