Surge protection for electric mobility
The market for electric mobility is on the move. Alternative drive systems are registering a steady increase in registrations, and particular attention is also being paid to the need for nationwide charging points. For example, according to calculations by the german BDEW association, 70.000 normal charging points and 7.000 quick charging points are required for 1 million e-cars (in germany).
Three different charging principles can be found on the market. In addition to wireless charging based on the induction principle, which is still relatively uncommon in europe (at the moment), battery exchange stations have been developed as a further alternative as the most convenient charging method for the user. The most widespread charging method, however, is wired conductive charging ... and this is precisely where reliable and carefully designed lightning and surge protection must be ensured. If the car is considered a safe place to be during thunderstorms due to its metal body and thus following the principle of Faraday's cage, and if the electronics are also relatively safe from hardware damage, the conditions change during conductive charging. During conductive charging, the vehicle electronics are now connected to the charging electronics, fed by the power supply system. Overvoltages can now also couple into the vehicle via this galvanic connection to the power supply network. Lightning and overvoltage damage is much more likely as a result of this constellation and the protection of the electronics against overvoltages is becoming increasingly important. Surge protection devices (SPD) in the charging infrastructure offer a simple and efficient way of protecting the electronics of the charging station and, in particular, those of the car from cost-intensive damage.
A typical installation location for such loading equipment is in the private environment in the garages of private homes or underground car parks. The charging station is part of the building. The typical charging capacity per charging point here is up to 22 kW, the so-called normal charging, whereby according to the german current application rule VDE-AR-N 4100 Charging devices for electric vehicles with rated power ≥ 3.6 kVA must be registered with the grid operator, and even require prior approval if the total rated power to be installed is > 12 kVA. IEC 60364-4-44 should be specifically mentioned here as the basis for determining the requirements of the surge protection to be provided. It describes "Protection against transient overvoltages due to atmospheric influences or switching operations". For the selection of the components to be installed here, we refer to IEC 60364-5-53. A selection aid created by CITEL facilitates the selection of the arresters in question. Please look here.
Charge mode 4
Last but not least, charging mode 4 describes the so-called fast charging process with > 22 kW, mostly with DC up to currently typically 350kW (perspectively 400kW and more). Such charging stations are mainly found in public areas. This is where IEC 60364-7-722 "Requirements for special operating facilities, rooms and systems - Power supply for electric vehicles" comes into play. An overvoltage protection against transient overvoltages due to atmospheric influences or during switching operations is explicitly required for charging points in publicly accessible facilities.
If the charging stations are installed outside the building in the form of charging points, the required lightning and surge protection is selected according to the selected installation site. The application of the lightning protection zone (LPZ) concept in accordance with IEC 62305-4:2006 provides further important information on the correct design of lightning and surge arresters.
At the same time, the protection of the communication interface must be taken into account, especially for wall boxes and charging stations. This extremely important interface should not only be considered due to the recommendation of IEC 60364-4-44, as it represents the link between the vehicle, the charging infrastructure and the energy system. Here too, protection modules tailored to the application ensure the reliable and safe operation of electric mobility.
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