EFI eV RCCBs - a reliable e-mobility protection
There are various types of RCCBs (residual current circuit breakers), they are classified also according to the shape of signal they can detect. As we are talking about standard residential installations there is usually installed A type RCCB, which can detect pure AC and also pulsating DC residual current. This is the most basic and common type of RCCB device we find in today installations.
But if there is present EV AC charger, there is also possibility of smooth DC residual current leaking to the ground, generated by the car (DC battery). This can become a problem, because standard A type RCCB will not react on pure AC residual current if there is present also smooth DC component higher than 6mA. Due to this DC component the residual current detecting transformer, which is inside RCCB device, becomes saturated and device is blinded. Therefore It won't react in case of electric shock if somebody accidently touches the line. This is the reason that according the standard IEC 61851-1 there are also special demands regarding residual current protection:
Where the EV supply equipment is equipped with a socket-outlet or vehicle connector for AC use in accordance with IEC 62196 (all parts), protective measures against DC fault current shall be taken. (Source: IEC 61851-1)
Therefore use of eV type RCCB is advised. This is the latest type of residual current protection on the market and is used for protection in EV AC chargers.This type operates as standard A type device with one addition, it will also trip if the smooth DC component of the residual current will reach 6mA.
And why exactly 6mA? That 6mA is the upper value of the pure DC residual current up to which the A type must still react in the time and value of the residual current (type AC or A) prescribed according to the EN 61008-1 standard.
Example of proper residual current protection with present one EV AC charger at home:
Image source: author's picture B. Drnovšek, 2019
AC or A type RCCB in mainboard (upstream) and EV type in EV charger
If there are installed 2 or more EV AC chargers, the AC or A type RCCB in the upstream board isn’t enough anymore, because theoretically sum of DC residual currents at all the chargers can be higher then 6mA and standard A or AC type RCCB would be blind again. The right solution in upstream board is B type, but this can be topic for next time.
Meanwhile many producers of EV AC chargers are instead eV type RCCB using »improvised solutions« for residual current protection such as combination of electronic circuit and standard electromechanical relay, which is cheaper, reliability unknown. We, as long-time producer of RCCBs, are fully aware how important is reliability of protection of your home and your loved ones. There are no short-cuts and room for mistakes. RCCB is the most reliable protection device against residual current, therefore electric shock. They are especially designed, tested and certified according international standards for residual current protection devices:
- IEC 61008-1, 61008-2-1, 61008-2-2 (Residual current operated circuit-breakers without integral overcurrent protection for household and similar uses).
- IEC 62955:2018 (Residual direct current detecting device (RDC-DD) to be used for mode 3 charging of electric vehicles). Therefore they are intended for use in permanently connected AC electric vehicle charging stations (mode 3 charging of electric vehicles).