Abstract

In this book, the idea for residual current protection has been presented. The evolution in construction types of residual current devices, which has taken place over decades, is discussed. Types and functional properties of the contemporary residual current devices are described. The main parameters of these devices, from the point of view of their selection and application, are indicated. Special constructions of the protective devices, among other portable and socket-outlets residual devices, are described. The reliability of residual current devices and main sources of their defects are discussed. The rules of backup protection of residual current devices without integrated overcurrent protection are presented. The application of residual current devices in TN, TT, and IT low-voltage systems is commented upon. Requirements of the standards, regarding the obligatory use of residual current devices, are quoted. The principles of application of residual current devices in protection in case of a fault, additional protection, as well as protection against fire, are explained. As extended information related to the use of residual current devices in protection against fire, arc fault detection devices are described, which can be treated as complementary protective devices especially in the case of dangerous series arcing. The issue of residual current devices’ operation in circuits with nonsinusoidal currents is commented in detail. Residual current devices also make difficulties during an earth fault loop impedance measurement, which is one of the commonly performed measurements to verify the effectiveness of protection against electric shock by automatic disconnection of the supply. The sources of unwanted tripping of the devices, during this type of measurement, are indicated and suitable methods of measurement are shown. Immunity of residual current devices to the impulse leakage currents is discussed. Moreover, coordination of residual current devices with surge protective devices is commented upon. Principles of residual current devices’ verifications, examples of their results, as well as fault diagnosis in circuits with these devices are described. At the end of the book, Appendix A presents examples of residual current devices’ selection. Additionally, Appendix B covers a list of the standards regarding residual current devices’ performance, application, and operation.

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