Residual Current Devices and Arc Fault Detection Devices

Residual Current Devices and Arc Fault Detection Devices

Residual Current Devices (RCDs) are now a standard part of any modern electrical installation, and their contribution to increased safety against electric shock is undisputed. To select the appropriate types and use them correctly, it is necessary to know a few basic rules to ensure trouble-free operation and, at the same time, to avoid nuisance tripping.

This new manual builds on the previous third edition, aiming to update some information, and is supplemented with fire protection using Arc Fault Detection Devices.

The first chapters describe the properties of individual types and designs of RCDs according to the requirements of product standards. Furthermore, the requirements of installation standards are defined to clarify the conditions under which RCDs should be used. These basic principles are followed by recommendations for choosing suitable types for individual applications. The update mainly concerns changes in the use of types sensitive to different kinds of residual currents, which today not only affects more complex industrial applications but also increasingly extends to common domestic installations.

Compared to the previous edition, the requirements of the standards have been updated, and information regarding the selection of types A, B, and F and their use in special cases has been added. The manual also includes an overview of measurement requirements during commissioning and inspections.

Finally, a very useful description of various causes of problems is provided for cases where an installation with an RCD does not function as expected. The recommended solutions should answer most questions encountered in practice.

A separate part of this manual is dedicated to fire protection using Arc Fault Detection Devices, commonly known by the acronym AFDD. This is a device that fills a gap in the previously available protective measures that use RCDs. Current electrotechnical standards recommend their use, especially in domestic installations and places with a risk of fire involving flammable materials. Because it is an affordable solution that increases the protection of human lives and property, it is only a matter of time before they are used in all cases for which they were developed. Experience from countries where they have been in use for many years unequivocally confirms their benefits.

This manual is intended for the broad electrotechnical community, and we assume that not only electricians and students of electrotechnical fields, but also inspection technicians and designers will find something useful in it.