Historical Development Of Residual Current Circuit Breakers

Since the invention and use of electricity, it has brought both immense convenience and devastating dangers. It can damage appliances, cause fires, or result in electric shocks. A device that ensures safe use of electricity would prevent many unnecessary losses. Therefore, along with the proliferation of various electrical appliances, a wide range of protective devices have also emerged. One type specifically designed to protect people is the residual current device (RCD). Commonly known as a leakage current switch, an RCD is a protective device used to prevent electric shock and electrical fires when a short circuit to ground occurs due to damaged insulation in a circuit or appliance. It is typically installed on the socket circuit of each household's distribution box and on the power input line of the building's main distribution box, the latter specifically for preventing electrical fires.

RCDs have undergone a long development process and are now widely used worldwide.

In 1930, a voltage-operated RCD was invented in Europe to prevent electric shock accidents caused by insulation damage in electrical equipment. In 1960, a current-operated RCD appeared. Currently, voltage-operated residual current devices (RCDs) have been phased out worldwide, while current-operated RCDs have become the primary electrical devices for protecting against leakage current and electric shock.

Japan began developing voltage-operated RCDs in 1964 to prevent electric shock accidents at construction sites. In 1966, it imported electromagnetic current-operated RCDs from West Germany, and began producing integrated circuit RCDs in 1976.

The United States began using current-operated RCDs in 1967. Electric shock accidents at swimming pools spurred the development of RCDs, and from the outset, required RCDs with a leakage current operating current of 5mA.

China began developing voltage-operated RCDs in 1966, began developing and producing electromagnetic RCDs in 1976, and around 1985, it developed and produced integrated circuit RCDs.

The widespread application of RCDs is inseparable from the formulation of usage standards and regulations. The 1971 edition of the U.S. National Electrical Code (NEC) mandated the installation of residual current devices (RCDs) in residential buildings and construction sites, effective January 1, 1973. Japan's Electrical Equipment Technical Standards and the Ministry of Labor's Safety and Health Regulations stipulate that electrical equipment operating at voltages exceeding 60V must be equipped with RCDs in damp locations, and all 400V circuits must have RCDs installed.

In 1981, China's former State Construction Engineering Bureau issued a "Decision on Strengthening Labor Protection Work," which mandated that all electrical equipment on construction sites must be equipped with RCDs. GB3787-1983, "Safety Technical Regulations for the Management, Use, Inspection and Maintenance of Hand-held Power Tools," formulated in 1983, stipulates that hand-held power tools must use residual current devices (RCDs). JGJ46-1988, "Safety Technical Specifications for Temporary Power Supply at Construction Sites," formulated by the Ministry of Construction in 1988, stipulates that electrical construction machinery and hand-held power tools must be equipped with RCDs, and requires the implementation of two-level RCD protection, including main power supply RCD protection, at construction sites.