Quality of residual current‐operated circuit breakers

Abstract

In the last few decades, residual current-operated circuit breakers, with (RCBO) or without integral overcurrent protection (RCCB, hereafter referred to indistinctly as “residual current devices” - RCD), have assumed a fundamental importance for the electrical safety of low-voltage systems. In accordance with IEC and CENELEC International Standards, they are a necessary protection against indirect contacts in TT systems, are recommended in TN and IT systems, and are able to prevent fires due to small earth-fault currents. RCD with a rated residual operating current Idn ≤ 30 mA also constitute the only existing active protection against direct contacts and in the case of failure of the protective or earthing conductor. Hence, it is upon their reliability that, to a large extent, the safety of persons, of livestock and property depends in the use of low-voltage electric power. This paper presents the results of a specific research conducted in Italy on approximately 21000 RCD installed in residential and nonresidential premises. The results of the research are analyzed in the dual intent of drawing, on a statistical basis. useful indications for improving the installation, manufacturing and testing requirements of RCD.