Image © Easee
This project investigated Easee’s functional implementation of the open-PEN protection incorporated into its single-phase electric vehicle (EV) charge point product – the Easee One.
The project was motivated by the requirement in BS 7671, IET Wiring Regulations, for the protection of EV charge points from the dangers relating to a broken neutral condition on the local distribution grid. In the wiring regulations this relates to regulation 722.411.4.1, known as open-PEN protection.
Easee has implemented functionality in its Easee One product that detects an open-PEN condition, isolating the charge point outputs and electric vehicles from dangerous supply voltages when they are identified. This implementation removes the requirement of installing an earth rod at the installation property, which is expensive and introduces a risk to installers of striking buried utility services.
The primary objective of this project was to test and validate the performance of the Easee One charge point’s open-PEN protective function. The project gathered evidence on the performance of the product to permit Easee to reassure those ultimately responsible for installation that its charge point product is safe and meets open-PEN safety regulations.
The PNDC team designed a test environment to mimic a typical site the Easee One charge point might be deployed at. This was connected within the PNDC’s low voltage test lab to represent a typical electrical distribution network where open-PEN faults might occur. The test environment was configurable to emulate a range of fault conditions that could be expected when an open-PEN fault occurs. The charge point sees these open-PEN conditions with abnormal voltage conditions present at its input terminals. The Easee One charge point was tested under no-load, low-load and high-load conditions to confirm the open-PEN protection function worked in all foreseeable scenarios.
PNDC used high-frequency data loggers to monitor the test environment and the Easee One charge point. This permitted the accurate identification and timing of the Easee One protective function. This data allowed Easee and the PNDC to confirm the Easee One was effectively isolating the EV from dangerous voltages and to accurately calculate the timing of the protective switching actions. BS7671 regulation 722.411.4.1 is very specific in how quickly dangerous voltages must be isolated and timing of the protective actions is crucial to validate this.
In addition to assessing the Easee One open-PEN protection function, PNDC also:
Assessed the device under test (DUT) behaviour when closing onto a fault and confirming this does not compromise the performance or electrical isolation of the device.
Assessed the dielectric strength of the DUT using an AC withstand (ACW) voltage test.
Assessed the insulation resistance (IR) of the DUT using a DC voltage test.
Outcomes & Impact
PNDC team confirmed the open-PEN protective function of the Easee One charge point is capable of identifying the electrical conditions that are indicative of an open-PEN fault, as specified in BS 7671.
PNDC also confirmed that the conductor switching sequence and timing to isolate dangerous open-PEN induced fault voltages were followed according to regulation 722.411.4.1 requirements. The conductor switching sequence and timing requirements required to re-establish power to the electric vehicles after normal network conditions resume were also observed to be followed.
Electrical isolation devices used by Easee within its charge points were tested at a component level and at a product level. Component tests, a desktop survey of the required standards, and manufacturer tests already completed confirmed the devices used by Easee are suitable for electrically isolating the charge point outputs.
The above performance testing has provided Easee with data to validate the performance of its open-PEN protection function and allow it to be included as a valuable feature of the Easee One charge point. Open-PEN protection functionality is valuable in keeping EV drivers safe from dangerous electrical faults and allows charge point installers to deliver EV charging solutions to their customers at lower effort and costs.
The findings from this project have helped validate the technical performance of the Easee One open-PEN protective function. The lessons learned during testing have helped refine the design and implementation of this feature and provide us confidence that this important protective function works as designed. Having validated open-PEN protection makes installing EV charge points easier and ultimately cheaper for EV drivers.
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PNDC is one of the University of Strathclyde’s industry-facing innovation centres and focuses on accelerating the development and deployment of novel energy and transport technologies through multiple collaboration models and open access facility provision.