ELECTRIC.IE • The Magazine & Website for the Irish Electrical Industry • 21 IIndusttry News Main Isolation (718.537) The distance between the means of switching off for the electrical installation i.e. the main isolator and the place where the corresponding supply cables enter the building shall be as short as practicable. This issue is also covered in the ESB’s “Code of Practice for Customer Interface” Figure 1 is an Interpretation of ESB requirements for the maximum distances of their cables within a customer’s premises. Maintenance of Lighting Circuits (718.559) Maintenance of adequate levels of illumination shall be determined by a risk assessment of the premises taking account of the classification of evacuation as per Annex 51ZA of I.S.10101. Two different arrangements for lighting final circuit are specified as follows: (i) Locations with low risk (Condition BD1) where a single normal lighting final circuit is adequate and (ii) other locations: (Condition BD2 , BD3 or BD4). For the latter, i.e. the vast majority of buildings, two or more lighting circuits are required with luminaires supplied in such a way that failure of either circuit will not leave any part of the location with an insufficient level of illumination. This rule also states that if RCDs are used they shall protect no more than one final circuit. RCDs are not generally required for protection of lighting circuits other than in domestic installations. However, where they are deemed necessary, e.g. in a room containing a bath or a shower, this rule means that a common or RCCB protecting a group of MCBs (which is common in domestic installations) cannot be used in communal facilities and workplace, i.e. each lighting circuit which requires RCD protection must be protected by an individual RCBO. If the normal lighting of a location accessible to the public can be dimmed, means shall be provided to reinstate the full level of illumination by an appropriately located switch. In some locations it may be necessary to ensure lighting cannot be operated by unauthorised persons. Figure 2 above shows a simplified example of compliance with 718.559 for a building meeting Condition of Evacuation BD2, BD3 or BD4. The corridor is illuminated using two separate circuits with lighting points Figure 2 - Simplified Example of Compliance with Rule 718.559. interleaved such that failure of either circuit will not leave the corridor in darkness. Likewise the emergency fittings are balanced across both circuits. Supplies for Electric Vehicles (722) Introduction Section 722 applies to circuits intended to supply energy to electric vehicles and circuits intended for feeding electricity from electric vehicles into the grid (V2G). While the entire section has been rewritten the basic requirements for domestic and similar installations has not changed. Selectivity shall be maintained between the RCD protecting an EV charging point and an RCD installed upstream. In a typical domestic system, while there are other RCDs in the consumer unit (i.e. those supplying socket circuits, lighting circuits, immersion heaters and electric showers), these would be in parallel rather than in series with the RCD serving the EV charging point and therefore there is no concern regarding selectivity. Figure 3 on the next page shows a typical installation for 7kW EV supply equipment / charging point in a domestic situation. Many of the EV charging points on the market have in-built d.c. earth leakage detection which disconnects the supply if the fault current exceeds 6 mA. They also have active load management systems which monitor the incoming mains to the consumer unit and regulate the output from the EV charging point to ensure the main OCPD is not overloaded. Wireless Power Transfer (WPT) Amendment +A1 2024 also makes reference to Wireless Power Transfer (WPT) technology for EVs. There are two broad categories of WPT. (i) Static Wireless Charging System (SWCS) – Charging while the car is parked / static and (ii) Dynamic Wireless Charging System (DWCS) – Charging while the car is in motion In a SWCS installation the vehicle parked over a base transmitter. High frequency a.c. power is transferred by magnetic induction to the vehicle receiver. This is then converted back to d.c. to charge the battery. While this technology is still in the developmental stage it is likely to become commercially available as an option to current wired arrangement in the coming years. Open PEN detection in BS 7671 It is worth noting that the draft for public enquiry of the A1 Amendment (NSAI: - Draft I.S. 10101:2020/ prA1:202x) proposed Open PEN detection similar to what has been included in BS 7671:2018 Amendment 2:2022. An open neutral or open PEN fault can cause significant deviations in the L-N voltage especially when there is significant load imbalance in the
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