Safety Norms for working on High Voltage Electric Vehicles

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.

We would like to thank Prasanth Kumar P and Aravind M from Haritha TechLogix for sharing their inputs on the subject.

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.

Source: Delphi Deutschland

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.

Also Read: EV Safety Features and Testing Standards

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

– Compressor

– PTC Heater

– Power Distributor

High Voltage Components of an EV | Source: Haritha TechLogix Training Material

The cables of all energy distribution components are colour-coded in Orange to specify live components for easy identification.

Volkswagen Showcar ID. CROZZ
Reference image: Volkswagen MEB platform shows Orange cables

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.

Concluding Thoughts

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.

Also Read: Top EV Training Providers in India

One thought on “Safety Norms for working on High Voltage Electric Vehicles

  • August 25, 2020 at 5:20 am
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    Article is good from the employee safety point of view. Electrical safety for passenger vehicle is very much important and may OEMs are not adhering to it in order to save the cost.

    Power Supply used in e-vehicles (4 wheelers, e-cars, e-buses and e-trucks) is Ungrounded Power Supply System (Floated Power Supply System or IT Power Supply System). The system without neutral grounding (in case of AC supply) at source side and in case of DC supply negative terminal is not grounded at source side is known as the Ungrounded Power Supply System, or in other words, in the Ungrounded Power Supply System, none of their conductors is connected to the ground at source side.

    Advantage of having Ungrounded Power Supply Systems are given below
    • This kind of power supply makes sure the continuous availability of power supply even in the presence of earth faults.
    • It also reduces the chances of fire accidents which may happen because of earth faults.
    • It also reduces the chances of getting electrical shocks because of earth faults.

    Because of aforementioned advantages it is widely used in various applications such as Electrical Vehicle and its infrastructure, Power Generation Plants (Renewable and Non-renewable), Transmission & Distribution Stations, Defense (Navy Ships, Army Tanks, Air Force Fighters), Core Industries (Coal, Steel, Aluminum, Zinc and other metals), Hospitals, etc

    To monitor the electrical conditioning of Ungrounded Power Supply System, IEC60364 (for EV segment it is IEC 60364-7-722) has laid down the guidelines which recommends to use the Insulation Monitoring Devices working on Active Measuring principle and this Insulation Monitoring Device must be in accordance with IEC 61557-8. This standard says that Insulation Monitoring Device must be capable of measuring insulation value of electrical system including Symmetrical and Asymmetrical earth faults. It also be able to give the pre-warning alarm before situation becomes critical.

    To save the cost, OEMs are using so called Insulation Monitoring Device which doesn’t comply with IEC 61557-8 standard. Such Insulation Monitoring Device works on Passive Measuring Technology. All the various types of Passive measuring technology is mentioned below and the Disadvantages of using Passive Measuring Technology are also given below

    Passive Measurement Method 1:

    In this method, IMD measures the voltage shift of each pole of power supply w.r.t. ground and gives the tripping command. This Passive measuring technology is not successful for those situations where Symmetrical earth fault comes into picture because under symmetrical earth fault condition voltage of one pole doesn’t not shift to other pole and IMD working on passive technology doesn’t sense the SYMMETRICAL EARTH FAULTS and go blind under Symmetrical earth fault condition which may further lead to major electrical hazard or accidents. Symmetric earth fault is that scenario where same resistance fault happens on all the conducting poles of power supply.

    Passive Measurement Method 2:

    In this method, conductive phase i.e. positive terminal or negative terminal is connected to ground through a high resistance, by doing this we have purposely converted the Ungrounded Power supply to Grounded power supply which will nullify all the benefits, mentioned above, of Ungrounded power supply. Because of this method, we have purposely given the fault current the required path to go back to the source through these high resistances which will lead to unwanted shutdown, fire accidents and electrical shocks. Because of these high resistance, current is limiting in its value and many OEMs are accepting it. However, as we know that one energy transfers from one form to another. So, this small leakage current generates the heat and it reduces the life of wires and which further lead to electric spark / electric hazards.

    To overcome above disadvantages of Passive measuring technology/ methods, IEC60364-4-41 has recommended to use the Insulation Monitoring Device working on ACTIVE Measuring principle in accordance with IEC61557-8.

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