Electric circuit breakers are used to protect branch circuits in residential, commercial and industrial buildings against overload and fault conditions. The circuit breaker can be classified into an oil circuit breaker using oil, a gas circuit breaker, an air circuit breaker using the air, a magnetic blow-out circuit breaker using magnetism, and a vacuum breaker using vacuum in accordance with used arc extinguishing medium. Circuit breaker and other circuit interrupters are often constructed with contacts and blades to form the electrical disconnect. A circuit breaker basically consists of a main contact at system voltage, insulation between main contact and ground potential (porcelain, oil, gas), operating and supervisory devices, and an insulated link between operating device and main contact.