Kirsty Johnson, Technical Sales Director at Surge Protection Devices, discusses the requirements for surge protection in EV charge point installations.
The electric vehicle market is on the increase, according to the society of motor manufacturers and traders (SMMT). In January 2020, 4,054 purely electric cars were registered, yet by January 2021 (despite the pandemic) this figure was 6,260. This is purely sales of electric vehicles (not the hybrid variants), so the market is a growing sector with a 54.4% increase.
Traditional brand name car manufacturers now offer the ability to buy our favourite cars, in a more environmentally friendly design. We therefore have to consider the electrical implications of EV charger installation. To successfully reach ambitious targets of reducing petrol cars and replacing them with electric, the public must be assured that they can charge their car when theyβre out and about, meaning that the continuity of service of EV equipment is a key aspect of EV chargers.
Every so often we all worry if we’re going to make it to the petrol station in time, but can you imagine arriving at a service station only to find out the chargers are out of service and the next one is 20 miles away? Not ideal for consumer confidence. To ensure the continuity of service, the installer must understand where issues can arise. From a surge protection point of view, electric vehicle charger installation should be carefully considered.
By their very nature, EV chargers are both sensitive (limited impulse withstand capacity) and exposed to overvoltage. In fact, quite a few EV charge point manufacturers will specify that an SPD should be installable or theyβll mention surge protection in the productβs warranty details.
Where is the risk of damage?
EV chargers are installed outside, therefore they’re liable to experience the effects of nearby lightning strikes. There is an increased risk of the charger being damaged from the effects of lightning, if the installation has an external lightning protection system, or if the EV unit is supplied directly from the main incomer of a building fed by an overhead supply.
Damage could also come from the installation, in the form of switching overvoltages. Overvoltages could also come from the supply network, or be created by equipment within the electrical installation. This form of repetitive overvoltage could damage the sensitive components used in EV chargers. Also, EV chargers can cause issues with the electrical installation. We have to consider that any cable that enters an installation can bring with it the risk of overvoltage. As mentioned previously, the effects of nearby lightning strikes are a risk to the electrical installation, along with the EV charger unit. Inverter technology can produce overvoltages, which can potentially cause damage to sensitive equipment inside the installation.
So, our risks are:
a) Damage to the EV charger
b) Damage to the car
c) Damage to the electrical installation
Using section 443 in BS 7671:2018 we can consider the requirements of SPDs. As a reminder, 443.4 states that: Protection against overvoltages shall be provided where the consequences caused by overvoltage could:
i. result in serious injury to, or loss of, human life
ii. result in interruption of public services and/or damage cultural heritage
iii. result in interruption of commercial or industrial activity
iv. affect a large number of co-located individuals
The obvious starting place would be to consider the public service obligation. If an EV charger is for public use, then under 443.4, it should be protected by an SPD. This ties in to the continuity of service. If an EV driver arrived at a service station to find that the chargers were out of use, that could cause severe interruption. There’s also the risk to life implication that must be considered if O-PEN technology is used.
O-PEN devices are designed for use in installations where there is a PME earthing arrangement. When the PEN conductor is broken, the neutral voltage can rise with respect to true earth and the normal protective earth forms the return path for any current that could flow. This could cause a car that is plugged in to charge to become live and, if contact was then made with the car, there is a danger of electric shock. The O-PEN device notices the rise in voltage on the neutral and disconnects the supply to the car charger, should a fault occur.
A number of EV charger units now rely on O-PEN technology to disconnect the supply to the charger in the event of a fault. If this technology is damaged, however, by the effects of lightning or some other form of overvoltage, the disconnection will not happen. In the event of a fault, this would mean that an electric shock could occur.
For all EV installations I’d recommend the use of an SPD, which is to protect the car charger itself, along with the installation. According to BS 7671, this will then become a βyou shallβ install surge protection on installations where the charger is for public use, or O-PEN technology is used.
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