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BS7671 Amendment 2-704 RCD protection: structure and

The use of poorly maintained or outdated electrical equipment in hazardous environments exposes workers and visitors to the risk of electrical shock, especially if they are in direct contact with the ground.
Rely on RCDs for added protection against faults. Many existing switchboards installed on construction sites in the UK contain AC RCDs.
AC RCDs are not suitable for use with most modern electrical equipment and tools used on construction sites, with the exception of resistance based heating and lighting loads – see BS7671 Amendment 2.
General requirements for this procedure are given in the main part of the automatic power off procedure. Amendment 2 at the end of § 531.3.3 states: “The AC type RCD shall* only be used for operation in fixed installations with known load currents that do not contain a DC component.”
The suitability of monitoring and controlling devices connected to the field power supply, especially plug-in devices, is a major health and safety issue. The risks associated with connecting three-phase equipment to an existing power source protected by the wrong type of RCD are a potential hazard at all sites in the UK. This is recognized and permitted in HD 60364-7-704 2018 Appendix ZB: On German construction and demolition sites / All 3 three-phase sockets up to 63 A must be protected by type B RCDS.
Temporary installations: Any equipment that is shut down and moved to a new site location or sent for refurbishment/repair will be compliant with the latest safety requirements, i.e. classified as a new installation and complies with current regulatory requirements.
Connecting new equipment: The health and safety guidelines (see below) emphasize the need for competent personnel to verify that the power supply and protection devices are suitable for the connected equipment, for example, the type of RCD should be appropriate for the connected equipment/tool. – see BS 7671 531.3.3
* Legal definition: “Shall” means that a person has an obligation or duty to perform an action.
The guidance provided in the HSE Guidance Document and BS7671 supports compliance with the requirements of the UK Health and Safety Act.
Properly selected RCDs provide fault protection and additional protection – see Risk Assessment Requirements: HSE Manual Working on Electrical Equipment. The guidance ( Indent 4 & 5) states that before connecting equipment, a “competent person” must check the supply. The guidance ( Indent 4 & 5) states that before connecting equipment, a “competent person” must check the supply. The manual (paragraphs 4 and 5) states that a “competent person” must check the power supply before connecting the equipment. The guidelines (indented 4 and 5) state that a “qualified person” must check the power before connecting the device. This includes the suitability and functionality of all RCD protection devices installed in accordance with the equipment.
Three-phase loads including inverters (e.g. pumps, compressors, seals, welders, etc.) generate high frequency and smooth DC leakage currents that interfere with standard RCDs. Rule 531.3.3(iv) requires the use of Type B RCDs to provide the required level of protection for these types of loads.
“You must take precautions against the risk of death or injury from electricity. Electrical equipment must be safe and properly maintained.” The HSE emphasizes the importance of the Electricity in the Workplace Regulations 1989 and supporting guidance to reduce/eliminate the risks associated with improperly designed and improperly designed, improperly used and maintained equipment. Electricity in the Workplace of the 1989 Rules, Rule 4-(1) “All systems shall at all times be so constructed as to prevent hazards as far as practicable.” The relevant HSE Manual (HSR25) sets out requirements regarding: design (paragraph 62), foreseeable conditions and use (paragraph 63), manufacturer’s characteristics, suitable electrical protective devices… (paragraph 64)), and “Equipment safety” . system depends on the correct selection of all electrical equipment. System”.. (p. 65)
That is, the RCD provides protection, therefore, when choosing the type of RCD, it is necessary to take into account the requirements and recommendations given in BS 7671 531.3.3, based on the range of equipment that can be connected after the protected RCD outlet.
RCDs and RCDs are suitable for final circuit/socket protection: their fixed ratings are particularly suitable for protecting 30 mA from unauthorized adjustment by unskilled (electrical) personnel – see BS 7671 531.3.4.1 CBR and MRCD have adjustable ratings, can be operated/technician as instructed – see clause 531.3.4.2 of BS7671.
NOTE. MRCDs are used with standalone fail-safe devices and therefore must be validated after OEM assembly and connection (BSEN60947-2 Annex M). This is done to test the total disconnect time of the entire MRCD + MCB + S/Trip or U/Release assembly as part of the final assembly test:
Given the harsh conditions of construction sites and the high risks of using electrical equipment outdoors, the rules are simple: equipment must be fit for use, maintained in good repair and safe to use. This includes choosing the right type of RCD, properly protecting equipment such as RCDs from the environment, and keeping it in good working order. Periodically check and test to ensure that the RCD provides the required level of protection and is suitable for the connected equipment. Before connecting new equipment to an existing switchboard – HSE regulations require a “qualified person” to test the power supply to ensure it is safe to use with the equipment.

Post time: Aug-16-2022