Viktors Nikolajevs, UK Key Account Manager at CTEK, takes a closer look at the requirements for PEN protection in EV charging applications and dispels a few myths along the way.

As the number of electric vehicle charging points in the UK increases at pace to meet UK government Net Zero targets, so there is an increased safety risk from (thankfully rare) open Protective Earth and Neutral (PEN) faults.

Should a PEN fault occur, the entire steel body of the vehicle would become energised and when the user comes in contact with it, they will become the only path to Earth.

DNOs report approximately 400 faults per year with typically only 1% resulting in electric shocks. But as the numbers of EVs grow, their increased numbers of users are at risk of electric shock during such PEN faults.

When a PEN fault occurs, the user is still at risk of getting an electric shock, even if RCD protection is in place. RCDs will still see the imbalance between the Line and Neutral conductors and break as expected.

However, the PE conductor will be effectively live under fault conditions and not break without dedicated means of isolation.

The most effective prevention is detecting the fault when it occurs before the end-user comes in contact with an energised vehicle body.

Requirements for electrical installations 

BS 7671:2018+A2:2022+A3:2024 outlines a requirement for PEN fault protection devices when using PME earthing under clause 722.411.4.1 for chargepoints located outdoors or that might reasonably be expected to be used to charge a vehicle located outdoors. The protection device is supposed to disconnect all live and PE conductors should a fault occur. Alternatively, the clause also permits the use of earth electrodes.

However, there is no underpinning BS product standard for PEN protection devices and the clause states that such functionality could be included within the charging equipment.

This prompted some EV charging equipment manufacturers to develop a variety of built-in solutions, mostly based around detection of Phase to Neutral voltage ranges of 207 V to 253 V.

Requirements for EV charging equipment standards 

This approach contradicts the requirements of Section 8.4 of the product standard for all EV charging equipment, BS EN IEC 61851-1:2019 Electric vehicle conductive charging system – General. 

The section states that for Modes 3 and 4 permanently connected EV supply equipment, protective earthing conductors shall not be switched.

EV charging equipment with enabled built-in PEN protection (i.e. the ability to switch PE) do not currently meet the product standard. There is a pending UK-only deviation for this standard that would allow PE switching inside of the charging equipment if the following conditions are met:

• Only manual reset permitted. Automatic reconnection prohibited.
• Full BSI Kitemark certification via type testing required.
• Functional test button required.

Not meeting the product standard raises potential issues such as liability in case of injuries and property damage, site insurance policy validity, CE/UKCA marking and certification, and suitability for grants, such as OZEV, since all of these typically require confirmation of compliance with EN 61851-1.

Requirements for OPDD standards 

IET has recently published IET01:2024 Open combined protective and neutral (PEN) conductor detection devices (OPDDs), which acts as the product standard for devices with PEN protection functionality.

The standard describes the operational requirements and their corresponding product markings.

Importantly, it increases the operational voltage range to minimise the risks of nuisance tripping in the areas with higher nominal voltage, in some cases from 184V up to 262.2V, and in certain cases as far as 273V.

IET01 permits PEN protection to be built-in to the EV charging equipment but drives the point that it must comply with EN 61851-1. This is done in preparation for the deviation mentioned previously and it aligns with requirements such as manual reset only and functional test button requirements for built-in devices.

It is important to note, that the extended voltage ranges are likely not to apply to built-in protection devices as EN 61851 will most likely retain the ESQCR voltage references of 207V to 253V. Whilst IET01:2024 is not referenced in any other standards or regulations at the time of writing, some of the DNOs have added the compliance with IET01 into the application process.

Summary

At the time of writing, EV charging equipment with active built-in PEN protection (the ability to switch PE conductor internally) does not meet BS EN IEC 61851-1 requirements in relation to PE conductor integrity within the charging station, pending the deviation.

If such devices do not have built-in test buttons and allow for automatic resets, they are also non-compliant with IET01, meaning that some DNOs may reject installation applications.

For locations where PEN protection is required, ideally external OPDDs in line with IET01 should be used in combination with EV charging equipment that does not switch PE conductors internally. This will ensure current and future compliance of the EV charging equipment, protective devices and the installation overall.

Under Construction (Design and Management) Regulations 2015 (CDM), installers may also be held accountable for using non-compliant equipment, as they may be classed as the system designers.

It is the responsibility of system designers to verify the equipment compliance and, if the equipment is found not to be compliant (even if the manufacturer claimed otherwise), the system designers are still completely responsible for the installation design and equipment used.

With this in mind, it is always recommended to request the manufacturer’s supply certification from third-party independent bodies such as BSI, Intertek or equivalent.

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