8 ELECTRIC.IE • The Magazine & Website for the Irish Electrical Industry • Phoenix Contact Safe electric vehicle charging – Protecting charging infrastructure from transient overvoltages Users and operators of charging stations expect one hundred percent availability from them. When a charging station is out of order, one side has limited mobility, and the other faces lost sales and repair costs. Short voltage spikes, known as transient overvoltages, are responsible for a signi cant proportion of failures. Protective measures to prevent transient overvoltages can help (Figure 1) Sensitive electronics in charging devices The equipment in charging devices depends heavily on the type of charge. A battery charging device is needed for all types of charging. For AC charging, the charging device is located in the vehicle, and for DC charging it is located in the stationary charging device. All charging devices have a charging controller. In AC charging devices, residual current devices (RCDs) are used to detect faulty currents, known as residual currents; in DC charging devices, insulation monitoring devices (IMDs) are used. Public charging stations also usually have operator terminals, billing systems and communications equipment. Charging parks include additional equipment for load distribution and for energy management. All of these components react sensitively to transient overvoltages, and must be protected from them (Figure 2). Hazard due to the effects of lightning and switching overvoltages With charging equipment, indirect lightning strikes – which are lighting strikes close by – must be taken into consideration. If the equipment is away from buildings, direct lighting strikes are more unlikely. In addition, comprehensive protection against direct lightning strikes is expensive — a lightning protection system is made up of an arrester, protective devices, a suitable grounding system, a dense potential equalization system, and lightning current carrying-capable surge protective devices (SPDs) of type 1. Therefore, most charging parks and individual charging stations do not include a lightning protection system of this type. Direct lightning strikes on charging devices are simply accepted as a risk. Figure 2 : Charging station for AC charging in public areas: The sensitive electronic components are protected by overvoltage protection devices of various types. Figure 1 : Protection even against storms: Charging devices need to function safely and reliably in all types of weather. Dipl.-Ing. Holger Heckler, Product Marketing Lightning and Surge Protection Trabtech, Phoenix Contact GmbH & Co. KG, Blomberg, Germany; and Dipl.-Ing. Axel Rüther, Electronics Sales Marketing, Phoenix Contact Deutschland GmbH, Blomberg, Germany.
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