Power distribution components transform and transfer voltage in order to distribute power supplied by electric service providers to load facilities. In power distribution, safety devices such as circuit breakers, earth leakage breakers, tube fuses, circuit protectors, etc., are installed to prevent accidents caused by abnormal circuit resulting from overcurrent, ground fault and earth leakage. Circuit breakers interrupt the circuit in the event of an overcurrent or a short circuit, earth leakage breakers interrupt the circuit in the event of an earth leakage, and circuit protectors provide overcurrent protection to internal circuits in devices as well as major pieces of equipment. Earth leakage breakers, in particular, are classified into 3 categories, high-sensitivity, mid-sensitivity and low-sensitivity, and are also available in high-speed types with up to 30 mA rated current sensitivity that shuts off current in less than 0.1 seconds in the fastest models for extra safety. In electromagnetic switches used for motor controls, thermal relays shut down the motor when it detects excessive heat generated by the motor in the event of an overload.