When it comes to testing the safety of roadside EV chargers, not all products are created equal. Here, Mark Johnson of Metrel UK Ltd compares test equipment from a selection of major manufacturers.
According to an article in Autocar published back in July, an unreliable charging infrastructure is preventing the electric vehicle (EV) roll out. This is hardly surprising given the ad hoc manner of the development of the infrastructure and the lack of strategic control in Britain.
Today, there are in the region of 28,000 charging stations in the UK, 10,000 of which are privately owned. To add an additional level of confusion, there are at least ten manufactures of vehicle charging equipment approved by the Office for Low Emission Vehicles. Each manufacturer is required to train electrical engineers on the installation of their equipment, but this can be as cursory as working through a web-based programme and answering some questions.
Meanwhile the 18th Edition requires that each charging point ‘shall be protected by either an RCD type B or an RCD type A and appropriate equipment that ensures disconnection of supply in case of a fault current above 6 mA DC’. That is how they should be installed, but there is no comment on how they should be tested on installation or, into the future, to ensure proper functioning and reliability.
From a survey run by one of the test instrument manufacturers, half of all installers have experienced out of the box failure of new RCDs, so for safety’s sake it is valuable to test newly installed RCD protection.
Between charger and tester: The interface
Strangely, while the charging station product market is relatively well developed, the equipment market for testing them is not. At the last count only three manufacturers produced interfaces for testing roadside chargers without opening them up.
One marketed by a charger manufacturer was originally dedicated to testing their equipment, though this has changed recently to be more universal. Two test equipment manufacturers sell adapters that can interface between any charge point and any manufacturers’ tester.
Of the adapters, the Rolec EVTU0018 can test single-phase installations, while the Metrel A1532 and Fluke/Beha EV-520-uk will allow testing of single and three- phase units. They simulate the charging state of the vehicle, disconnected, charge ready, active charging (with and without ventilation) and pilot error, and permit the system to be electrically tested as a whole, and not just discrete parts.
And because there is no need to open the box, testing is quick and there are no warranty implications. However, there is a problem with these adapters; they are only as good as the tester you connect them to.
Testers: The limitation
Returning to the 18th Edition stipulation, the electrical vehicle supply equipment (EVSE) must be protected by type B RCD or a type A RCD and something to disconnect the supply when more than 6 mA of DC fault current are present.
Any all-in-one tester will test type A RCDs, premium testers such as the Fluke 1663 and 1664, and the Megger MFT1721 and MFT1741 will test type B RCDs. Until now it was only the Metrel range of three multi-function testers that would test type B RCBs and that offer a standard 6 mA DC disconnection test, classed as type EV RCDs to confirm all types of charger protection conform to the 18th Edition.
Recently the Fluke 1664 FC has been marketed as part of a kit to cope with EVSE testing and Megger has introduced a MFT1741+ so that they have an EVSE capable tester. However, this entails buying a new machine.
Test automation
Many years ago, Megger pioneered the Auto RCD test, and the contractors were slow to adopt it, possibly due a failure to explain just how useful a function it could be. It is now one of the most popular functions on their testers and they have extended it to do EVSE breaker testing, however they have not moved on to adopt more automatic testing functions. It is known that they are working on their data/results storage capabilities, hoping to make it more usable.
At the premium end of their range, Fluke has incorporated automatic installation testing, allowing the scripting of up to seven installation tests, saving time by reducing the need to remake connections. But they, ‘do not have a fixed 6 mA DC test for RCDs. The only technique that could be used is to run a ramp test using the 10mA RCD setting.’
Consequently, the Fluke 1664FC may not be used in any automatic mode to test vehicle chargers, but results, once obtained, can be saved to the cloud via a smartphone running IOS or Android and shared easily.
All three of Metrel’s testers have automated testing for EVSE points using the Autosequence function. The operator opens the test, enters the parameters of the test such as earthing system type and starts the test, changing the vehicle status button when prompted. Not only the functional tests and breaker tests but a full electrical test is completed.
The future
The future is always difficult to predict. One thing is certain – 28,000 charge points are not sufficient in a population of approximately thirty million vehicles. A recent estimate put the figure at 2.5 million high speed public charge points.
There will be a lot more installations to be tested both initially and on an ongoing basis. The electrical distribution companies are talking about using the population of electric vehicle storage systems to both store and manage supply from their renewable generation, charging in off peak and buying energy back in the peak. Although it sounds complicated and would require a much smarter grid.
It is known that some companies are working on a consumer device that they can plug in to check a charger’s safety before they attach their valuable vehicle, to confirm it is not going to burst into flames.
At recent exhibitions, an e-mobility analyser was displayed – a much more sophisticated interface. It supports diagnostic testing and verification of electrical safety and function of type 1 and type 2 supply equipment, as well as testing mode 2 and 3 charging cables and their communications, monitoring between vehicle and charging station during operation, using either a multi-function tester or, using an Android app and mobile phone, to control testing, as well as monitor and store the results.
