Companies providing facilities at any premises for employees and or visitors to plug in their “own” electrical appliances, are required by Law to manage any direct or indirect hazards related to the use of that equipment – Suitable and sufficient assessment of the “Risks” also applies to the charging of EVs on site.
RIDDOR report the number of fatalities at work due to contact with an electrical supply (workers and member of the public), as circa 32 deaths between 2014 -2018. The number of electrical accidents is harder to pin down. HSE info suggests it could be in the region of 1000 or more per year. The HSE highlight the increased risks associated with using damaged electrical equipment outside (Electrocution Hazard), particularly portable flexible leads plugs and sockets.
Mode 2 Charging
These cables were originally designed to provide a safer method for opportunistic charging, when connecting directly to a standard domestic socket. Extension leads rolled out on pavements and drives overnight and the safety aspects of connecting to 13A ring main, without the appropriate RCD protection, still pose a high risk to the user and other persons who may come into contact with faulty or damaged electrical equipment. The fire hazards associated with overheating of sockets and extension cables are well documented.
Mode 2 charging cables are portable devices, for use outside. Providing facilities for this method of charging at a place of work, business or public building, raises complex safety issues*. Duty Holders are responsible for managing the risks associated with portable appliance use on site, either by an Employee or a Visitor.
It should be noted that the OLEV’s minimum technical specifications covering EVHS and WCS, do not recognise Mode 1 or 2 as compliant methods of charging.
RCDs associated with Mode 2 charging
From January 2018, IC-CPDs manufactured to IEC 62752:2016 used in Mode 2 charging cables , had to include the facility to detect DC residual currents and disconnect if > 6mA DC. i.e. mitigate the risk of DC fault currents associated with EV battery charging and upstream Type A RCDs. That is, RCD blinding and loss of 30mA protection for the circuit, that may be feeding other appliances. The IC-CPD 30mA detection function does not provide electrical isolation, this is only achieved by unplugging the charging cable. i.e. to meet Regulation 722.531, there must be a separate RCD within the circuit. Using a dedicated 13A socket /circuit limits risks to that area of the installation.
*Mode 2 charging cables manufactured before January 2018 that do not include the 6 mA DC detection feature, are not designed for connection to circuits that are only protected by Type A RCDs.
This issue is addressed in the context of the 18th Edition; “protective measures against DC fault current shall be taken, except where provided by the EV charging equipment” i.e. if the IC-CPD does not provide the required measures, the Regulations specify Type B RCDs or Type A + disconnection of the supply in case of DC fault currents if > 6 mA. The Doepke Type A EV RCD provides this combined functionality.
Mode 3 Charging
In theory this method of charging should be the safest, using dedicated charging infrastructure, robust plugs and simple cable connection between the EV and the charge point. The revised Standards, Regulations and Codes of Practice give clear guidance on design requirements to achieve safe and reliable performance over a number of years. The facility for tethered cables simplifies the H & S management process, as opposed to portable cables, which could be damaged prior to use on site. Damaged cable insulation poses a risk to the user and other members of the public, particularly children who are attracted to the bright colours and interesting qualities.
RCDs associated with Mode 3 charging
IEC 61851-1:2017 included the requirement for specific protective measures to be taken against DC fault currents, without exception i.e. 6 mA DC detection and disconnection of the supply to be included in the charge point when associated with a 30mA Type A RCD. Or by external means such as Type B RCD or Type A plus 6 mA DC detection and disconnection technology.
This revised safety requirement is reflected in 722.531.2.101 (18th Edition) and the revised Code of Practice for EV charging installations 3rd Edition.
Meeting the above is relatively straight forward, for an installation supplying one Mode 3 charge point (see figure 1). The considerations relate directly to the EV that will be connected to the charge point and the EV Manufactures requirements for charging*. For example, to meet the 18th Edition requirements, Tesla specify the use of DFS4 AEV with their Mode 3 charge points and their vehicles. The DFS4 AEV RCD includes 6 mA DC detection + 30 mA Type A protection.
*EV Manufactures may specify Type B RCDs if the EV cannot charge due to the 6 mA DC detection feature.
The 6 mA DC fault current detection feature built into EV chargepoints, is not classed as a protection function. A separate 30mA RCD is required to disconnect and isolate the circuit under fault conditions; see RCD requirements detailed at the end of 722.531.2.101. Single chargepoints incorporating an RCD may require an additional Type A RCD at the origin of the charge point supply e.g. Regulation 411.3.2 and 522.6.202. Note charge points must not be connected into circuits contain Type AC RCDs upstream.
Installation designs supplying two or more Mode 3 charge points (see figure 2), must take account of the combined effects of leakage currents when charging multiple vehicles. Refer to the Code of Practice for EV charging equipment installations 3rd Edition clause 8.5.3: Type B RCDs must be used where the DC component of the residual current could exceed 6 mA.
Documented Inspection & Testing
Keeping records on site helps to demonstrate the effective management of H & S policy and provides Duty Holders, with a recognised method of monitoring and reviewing safety compliance. In the absence of any specific guidance for EV charging installations, refer to the IET CoP 4th Edition for In-service Inspection and Testing of Electrical Equipment.
The RCD six monthly test interval is based on fixed equipment in a controlled, clean environment inside a building. Charge point mounted RCDs are subjected to a different set of environmental conditions.
High Risk Environments
Duty Holders are required to control and reduce risks, namely sufficient to prevent danger so far as is reasonably practicable (SFAIRP) and as low as is reasonably practicable (ALARP). Inspection, necessary testing and the period between these activities, should reflect the actual conditions of a specific installation based on the Risk Assessment for that Site.
The environmental conditions, location (site access), amount of use and possible vandalism, may lead to an increased risk associated with the EV charge point and any associated charging cables. For example, if the site is accessible 24 hours a day, it may be considered reasonable on the bases that the cost to implement is low, to carry out a visual inspection of EV charging infrastructure, on a daily basis or as deemed necessary by the Dutyholder.
More detailed checks and tests should be completed on a regular basis, refer to the EV charge point instructions, the EV manufacture and the advice given in Regulations for higher risk environments.
Levels of pollution and significant fluctuations in temperature and humidity associated with road side and carpark installations, may impact on RCD protection availability - See PD IEC/TR 62350:2006.
The HSE's Electricity at Work Regulations guidance (HSR25 3rd Ed.) Regulation 4(2) states: “Practical experience of use may indicate an adjustment to the frequency at which maintenance needs to be carried out” i.e. the intervals between inspection, testing and maintenance must be based on the actual service conditions and experience related to that installation. That is, to verify RCD protection availability, initially checks and tests would have to be performed more frequently, to determine the optimum time between tests.
If the RCD test button is operated and the RCD fails to trip, the installation must be checked by an appropriately electrically skilled person, before the charge point is returned to service. Doepke can provide HD version RCCBs for installations subjected to tough ambient conditions.
RCDs selected strictly in accordance with the Regulations, installed and maintained correctly, perform a key safety function in all EV charging infrastructure. RCDs that are tested regularly (using the test button), will give a longer and more reliable service life than devices that are tested infrequently.
