Proximity Pilot (PP) serves as a charge cable detection and current limitation. The Proximity Pilot is implemented differently in Type 1 and Type 2 plugs. For Type 1 plugs only, the Proximity Pilot also takes care of mechanical locking and sparkleless disconnections.
Charge Cable Detection
It is important for the EV to ‘know’ that the EV is connected to an EV Charger. While with fuel cars it occasionally happens that people drive away with the hose still inserted, with electric charging the likeliness of this happening is much bigger as one will not be waiting next to the car for the charging to finish. The Proximity Pilot in the plug serves this purpose by creating a circuit via a resistor to the PE pin.
The value of the resistor differs in the Type 1 and the Type 2 plug. In the Type 1 plug it is 150 Ohm. In the Type 2 plug it can have different values. The most common two are 680 Ohm and 220 Ohm although the standard does define 1500 Ohm and 100 Ohm too.
Current Limitation (Type 2 only)
The function of current limiting applies only to Type 2 plugs. The reason is that Type 2 plugs are both on vehicle side as on charger side. This is a main difference from the Type 1 plug which only has a vehicle side plug. In North America and Japan, who don’t use type 2, the cable is always tethered to the charger making it integral part of the Electric Vehicle Supply Equipment (EVSE). This implies that the current capacity of the cable is compatible with the charger. For a cable that is not part of the EVSE, the cable can have conductor thickness which is not enough to carry the maximum current the EV can draw and thus overheating the cable resulting in dangerous situations.
The resistor value in the type 2 plug indicates the conductor size of the cable. The conductor size determines the maximum current the cable can handle. The following values apply:
* In a 1 phase system it maximum current may be even 70 ampère.
** In many European countries, the local regulations demand a maximum of 16 Ampère for fixed wiring of 2.5 mm2. Also regular over current protection is maximised at 16 Ampère. Therefor 16 Ampère is most often used for home chargers.
Sparkeless Disconnect (Type 1 only)
As the type 1 has a fixed 150 ohm resistor, no current limitation can be indicated. For charger points with a socket, the Type 2 plug connected at the charge point will indicate the current capacity to the charge point. For tethered cables, it is assumed the current limitation is set in accordance with the power supply and the cable capacity, which ever has the lowest value. See also PWM Signal for how this is enforced.
The Type 1 plug has a button with a mechanical lever which hooks into the socket of the car. The position of the lever is monitored with a (micro)switch. The plug can only be disconnected from the car if the button is pressed and thus activating the switch. This will cause the proximity pilot resistor to change from 150 Ohm to 500 ohm. With this, the EV will detect the attempt to disconnect the charge cable and will stop the charging process immediately. As the contacts will not carry current anymore, there are no sparks. It is safe and the contacts will last longer. How this is achieved in a type 2 plug can be read here.