Zaptec Go (UK 7kW open PEN fault version) has integrated PEN fault protection to ensure safe operation in compliance with BS 7671:2018 Amendment 1:2020 clause 722.411.4.1 (iv). This article describes this feature.  An independent test report is available to confirm this; see the attachment. 

How PEN fault protection works

The PEN fault protection is triggered if the charging station detects a voltage of more than 253 V rms or less than 207 V rms between the line and neutral conductors for more than 5 seconds.

• When triggered: Live, neutral, and earth connections to the vehicle will be disconnected. 
• The charging station will display a red light, and charging (if active) stops immediately. 
  
• After the charging station detects normal voltage for 30 seconds, it will return to normal operation.
• If not charging: it returns to ready mode (white light).
• If charging: it resumes charging (blue pulsing light) up to 10 times before permanently locking out. To reset this lockout state, disconnect the charging cable. The charger will then return to normal operation once it has detected normal voltage for 30 seconds.
• This message will also be shown in the Advanced settings screen of the relevant charger in the Zaptec app.
  
  

What to do if a PEN fault is detected

A detected PEN fault means that an abnormal supply voltage has been detected that is outside of the statutory requirements. This is a potential safety hazard.

• Action required: Contact the Distribution Network Operator (DNO) by calling 105 to report the issue.
• Diagnostics: The DNO should then investigate the reason for the abnormal supply voltage and make repairs, if necessary. Additional diagnostic information is available from the charger to help with any investigation. This information can be requested by contacting Zaptec support. 

Why is PEN fault protection necessary

In the UK, it is a legal requirement that EV chargers that are used to charge vehicles outdoors are protected from neutral faults when connected to a PME network. This ensures that the user cannot get an electric shock if the supply neutral becomes disconnected. This is done by disconnecting the live neutral and earth connections to the vehicle if a fault is detected, in accordance with IET wiring regulation 722.411.4.1.

This is because many UK electricity supplies combine the earth and neutral into one Protective Earth-Neutral (PEN) conductor, using a supply system known as PME (Protective Multiple Earth). Normally, this is a safe system. It becomes unsafe if the PEN conductor becomes disconnected (or "open") from earth. During this state, if someone simultaneously touches something connected to the PEN conductor (such as an EV plugged in to a charger) and something at true earth potential (such as a metal fence), the usual earth-leakage protection RCD will not operate - and the person could receive a fatal electric shock. To protect against this, it is necessary to either provide a dedicated earth to the EV charger, or fit a PEN fault protection device that will automatically disconnect the PEN.

If there is a true earth available (TT or TN-S) and the earthing system is in good order, PEN fault protection may not be required. If there is any doubt, then PEN fault protection must be fitted. 

Identification and electrical connections

The Zaptec Go (UK 7kW open PEN fault version) can be easily identified by the "ZGBxxxxxx" serial number. It has three connections: Live, Neutral, and Earth (PE).

Updated 10 December 2024 13:41