Any high voltage (HV) electrical system requires specialised personnel training, protective equipment and precautionary measures to ensure the safety of people working on the floor. In this article, we cover the basics of safety-related pointers that one needs to be aware of while working on high voltage electric vehicles. All the professionals, as well as employers in the EV domain, should be aware of these basics.
When is an Electric Vehicle designated as a ‘High voltage’ system?
In the automotive industry, high-voltage refers to voltages above 60 V DC. At this level, the need for contact protection becomes mandatory.
The voltage range varies for different category of vehicles. Electric two-wheelers and three wheelers ranging from 24V to 72V are present in the market, depending on vehicle’s power and acceleration requirements. However, for 2Ws and 3Ws, voltage up to 60V is preferred to keep the homologation process simpler and the costs low. 48V systems are most preferable for electric 2W and 3W and vehicles like Mahindra Treo and Ather 450 fall in this category.
For electric 4Ws, the range is generally between 300 to 500 V, whereas, electric buses from 800V to 1200V are available in Indian market today.
What all components of an HV Electric Vehicle are ‘High Voltage’?
Any component that has a connection with the HV battery pack, is a high voltage component.
– Traction Battery Pack
– DC-AC Inverter
– Electric Motor
– DC-DC convertor
– On-board charger
– PTC Heater
– Power Distributor
The cables of all energy distribution components are colour-coded in Orange to specify live components for easy identification.
What are the safety risks associated with high voltage systems?
The risk associated with working on high voltage systems is an ‘Electric Shock’, that could be fatal under some conditions.
Please note that electric currents of more than 0.5 mA in AC voltage and more than 2 mA in DC voltage are capable of causing injury, while the degree of the harm depends on the intensity of current, resistance met, the path taken by the current in human body and duration of contact.
What regulatory requirements/norms do the employers have to follow to ensure the safety of employees?
The employers are liable to ensure the safety of employees and are mandated to adhere to Occupational Safety and Health Standard e.g. OSHA 1910.132 and equivalent Indian standards created by BIS.
The employers need to ensure that the employees receive necessary safety trainings, and have access to PPE kits for working in an environment with safety risks.
What all equipment is included in the safety kit?
PPE or Personal Protective Equipment has many components, including:
– Insulated gloves (to prevent electric shock)
– Goggles (to protect the eyes)
– Non-slippery Insulated boots
– Hot stick (a long insulated pole that can be used to separate a person under electric shock from contact)
Alongside the equipment, the floor area should have warnings and indicators to imply the zone is a high-risk zone because of the presence of high voltage systems.
What all job profiles in the EV industry need to be cognizant of these safety norms?
– Automotive Service Technicians
– Engineers working in Vehicle Electrification projects
– Manufacturers of High Voltage EV Components, such as high voltage Battery Packs
– Testing Professionals working on EV Projects
– Research scholars and Students working on EV Projects
What is the Standard Operating Procedure (SOP) for safe disconnection of high voltage systems in an electric or hybrid vehicle?
Step 1: Turn the ignition key OFF and remove the ignition key from the Vehicle
Step 2: Setup a barrier around the Vehicle (Approx. 1 meter away from Vehicle)
Step 3: Place a HV Warning Sign on the vehicle
Step 4: Remove the negative terminal of the 12V Battery & Insulate it.
Step 5: Secure the bolts if any at safe place (or it may lead to short circuit).
Step 6: Check the voltage tester for proper functioning with a 12V Battery.
Step 7: Remove watch or any metal objects from your body & wear the HV protection gloves in your hands.
Step 8: Unlock the Service plug and then disconnect it from the HV Battery pack.
Step 9: Wait for few minutes (As specified by the manufacturers).
Step 10: Ensure zero voltage (0V) at terminals with multimeter before proceeding with any service activity.
As India moves ahead with electrification of its public transport and other mobility options, it becomes extremely important to have safety guidelines in place for handling of HV systems. The employers need to ensure sufficient hours of training for all stakeholders to avoid any accidents at work. The presence of High Voltage systems also makes the infrastructure requirements of an EV service station more sophisticated with the need for special tools, equipments and appropriately trained professionals.