In household a properly designed electrical diagram should also include overvoltage protection. This overvoltage protection saves complete household against over voltage, which comes from the grid, when thunderstorm or something similar is in the nearby and causes voltage peaks. This household (external) overvoltage cuts the peak in more levels ( Class I, Class II, Class III) of the overvoltage and ensures that voltage in household grid stays in normal value. This overvoltage protection must be installed on all phases. See some instructions about that topic on site:
http://www.tsipower.com/uploads/white-papers/WP-IEC-61312-Surge-Protective-Device-Coordination-2012-06-14.pdf
Residual current protection and over current protection do not protect your household against over voltage.
Our INCH have installed internal over voltage protection Type III, if over voltage protection in house hold (external) does not work. INCH internal overvoltage protection trips to try to save the connected car on the charging station. In this case is also mother board burned. But in-built over voltage protection Type III can not cut the whole over voltage peak, which comes from the grid, if Type I and Type II doesn’t exist in household over voltage protection system and doesn’t cut off the voltage peak till value, which can be taken over by Type II.
Possible naming:
Class A (operated by an electrical distributor)
Class B same as Class I or Type 1 (build in main electrical cabinet)
Class C same as Class II or Type 2 (lightning protection, can withstand indirect impact)
Class D same as Class III or Type 3 (protections in devices, in our case - varistors)
What could go wrong?
If the station is connected incorrectly, it will damage several variators.
There are two scenarios of overvoltage: interphase or earthing overvoltage.
If one or the other happens, it will damage one varistor. If both happen at the same time multiple varistors.
When this happens, it can also damage cables and connectors!
IMPORTANT: always check the connection (in electrical cabinet and in charging station) before the first start-up.