An earthing system connects specific parts of an electrical power system with the ground for safety purposes.
Earthing provides a simple path to the leakage, fault or overload current in the system for passing to the earth. It thus protects the system equipment and personnel working with these types of equipment from damage as well as shock.
Every building, equipment, power plant, substation facility require earthing. The main objective of earthing in an electrical network is safety.
When installing electric vehicle charge points, driving an earth rod has always been the standard way to protect users from potentially getting hurt if the system ever develops a fault.
An earth rod is a conducting element buried directly in the ground, facilitating the flow of current towards the ground.
Copper earth rods are the most cost-effective option which provides corrosion resistance as well. Highly conductive copper couplers are used to join multiple rods together to achieve the desired length to access lower resistance soil deeper in the ground.
- At present, EV charging points do require earthing and earth rods. This is being followed in western countries and is being adopted in developing countries that are embracing EV technology. The earthing process might be inconvenient, time-consuming, and problematic owing to different terrains, but for the sake of safety, it is very significant. The government of India has also given stress to this in safety provisions.
- In India, the Ministry of Power’s ‘Central Electricity Authority (CEA), incorporated certain safety provisions pertaining to the charging of electric vehicles. It is included in a CEA notification called ‘the Central Electricity Authority (Measures relating to Safety and Electric Supply Amendment Regulations, 2019)’. A section dedicated to ‘Earth Protection System for Charging Stations’ clearly states the following:
- Earthing of all EV charging stations shall be TN system as per IS 732. (In India, earthing is generally through the TN system. Neutral is double grounded at distribution transformer, neutral and earth run separately on distribution overhead line. Additional earth electrode pits are installed at user ends for strengthening earth).
- All Residual Current Device (RCDs) for the protection of supplies for EVs shall be quality tested to interrupt all live counters, including the neutral. (An RCD is an earth leakage protection device).
- All EV charging stations shall be provided with an ‘earth continuity monitoring system’ that disconnects the supply in the event that the earthing connection to the vehicle becomes ineffective.
- A protective earth conductor shall be provided to establish a connection between the earth terminal of the supply & the conductive part of the vehicle.
- For a more detailed view of safety requirements with respect to charging stations & charging points, visit this PDF link of Central Electricity Authority (CEA) and refer to ‘Earth Protection System for Charging Stations’.
- DC fast chargers require protection against ground faults on both the input and output sides. The isolation transformer inside the charger separates the input AC power from the output DC power and therefore, the output side is not grounded. Instead, a ground-fault monitor is installed on the output side to detect any earth leakage and shut off power immediately.
- In Norway, the equipment is grounded separately at the user end and has no connection to the neutral wire coming from the utility.
- Many modern EVs have ‘Ground Fault Indicators’ which are used to detect a ground fault and disconnect the charger to protect people from shock.
- In Britain, new rules were proposed that in nearly all circumstances the installer will need to install a dedicated earth rod for the charge point.
- To protect workers/employees/users who regularly come in contact with electrical equipment.
- To keep the voltage of the electrical devices in the healthy phase in case of any fault.
- A well-connected earthing system ensures that electrical faults are cleared quickly. If the fault stays within the system for a long time, it can threaten the stability of the system.
- Provides surge protection.
- Malfunctioning cables and electrical devices often leak electricity which can start a fire if not redirected safely.
New generation EV charging units have been developed without requiring an earth rod. These charging systems are specially designed to completely disconnect the charging point from the car if a fault develops.
Experts are viewing this kind of technology as an acceptable alternative to earth rods. The newer EV charging devices have in-built systems to continuously monitor voltage conditions, so if the voltage exceeds a certain amount it automatically triggers the charger to stop operating and isolate from the electric vehicle.