Successful selection and operation of overcurrent and residual current protective measures

Most basic electrical protective measures are intended to ensure that significant electrical energy cannot be dissipated anywhere other than within current using equipment. These measures include primary and secondary insulation, enclosures, barriers etc., and they have a passive function. Active measures are generally arranged to interrupt the supply to a circuit when electrical energy dissipation becomes excessive either within the circuit conductors and current using equipment or outside the circuit (for example in a person) where no dissipation is intended. The author examines active protective measures generally and describes the conditions necessary to ensure their successful operation.<>