Authors:
John Choi – Industry Marketing Lead, Transportation and Industrial Batteries and EV Charging, Energy and Industrial Automation (EIA)
Frederick P. Reyes – Principal Engineer, Energy and Industrial Automation (EIA); Distinguished Member of Technical Staff, William Henry Merrill Society
The personnel protection system (PPS) for electric vehicle supply equipment (EVSE) helps enhance the safety of people and property. The testing, evaluation and certification of these critical systems can help boost consumers’ confidence in the growing electric vehicle (EV) market. UL Solutions plays a critical role in helping manufacturers demonstrate their dedication to the safety of these systems, which are a critical link between EVs and the electrical grid. This article covers:
- The main components of EVSE, which protect users from potential hazards, such as electric shock and fire
- How the testing process examines the mechanical and electrical construction of the systems, focusing on components that protect users from electrical hazards
- Why collaboration among manufacturers, code authorities and installers is essential in building a safer EV ecosystem
Continue reading below to explore those topics.
The Importance of Safety Standards for EVSE
The rise of EVs marks a significant shift in the automotive landscape, bringing with it a heightened focus on safety protocols and standards that govern EV infrastructure. As EV adoption accelerates, the need for certification and testing of the PPS for EVSE becomes paramount. These systems enhance user safety and play a crucial role in fostering public confidence in EV technology.
EVSE serves as the critical link between EVs and the electrical grid, providing the necessary infrastructure for safely charging batteries. As such, certification is essential for demonstrating that these systems meet applicable standards for reliability and safety, including:
- UL 2231-1, the Standard for Personnel Protection Systems for Electric Vehicle (EV) Supply Circuits; Part 1: General Requirements
- UL 2231-2, the Standard for Personnel Protection Systems for Electric Vehicle (EV) Supply Circuits, Part 2: Particular Requirements for Protection Devices for Use in Charging Systems
- UL 2594, the Standard for Electric Vehicle Supply Equipment
- UL 2202, the Standard for DC Charging Equipment for Electric Vehicles
The main components of EVSE, including EV couplers, cables and charging stations, must undergo rigorous safety evaluations to assess whether they can protect users from potential hazards, such as electric shock and fire.
Key Elements of the PPS
At the heart of EVSE lies the PPS, primarily composed of charge-circuit interrupting devices (CCIDs) and isolation monitors/interrupters (IM/I). These elements perform vital functions, including:
- Preventing electric shock – CCIDs, such as ground-fault circuit interrupters (GFCI), act as a safeguard by monitoring for ground faults and have a long-standing track record of significantly reducing the risk of electric shock.
- Mitigating fire risks – By swiftly disconnecting power when a high-impedance ground fault with a magnitude below the overcurrent protection handle rating is detected, CCIDs help prevent electrical fires caused by faulty wiring or device malfunctions.
- Enhancing safety in challenging conditions – These devices are particularly crucial in wet outdoor environments where the chances of electric shock are elevated.
- Helping with compliance – Codes and standards, including the National Electric Code® (NEC), require Listed PPSs compliant with UL 2231-1 and UL 2231-2, which outline safety benchmarks for EV supply circuits. This compliance is vital for both residential and commercial charging installations.
Comprehensive Safety Evaluations for EVSE
North American EVSE undergoes assessments based on key UL Standards, helping demonstrate these systems meet applicable safety criteria. The testing process examines the mechanical and electrical construction of the systems, focusing on components that protect users from electrical hazards. Notably, Level 1 and Level 2 EVSE typically integrate CCIDs for centrally grounded systems, functioning similarly to ground fault circuit interrupters (GFCIs), whereas Level 3 direct current (DC) fast charging stations typically use an isolated DC supply system, ideal for implementing IM/I for monitoring insulation resistance.
Testing to UL 2231: A Commitment to Safety
Certification to UL 2231 underscores a commitment to enhancing the safety of EV charging systems. This Standard stipulates performance evaluations that encompass testing requirements to monitor, detect and comply with stringent interrupting times. The rigorous testing also borrows testing concepts for reliability to determine the efficacy of the protective system while operating in extreme conditioning during the environmental testing sequence. The suite of UL 2231 construction and performance tests is essential for assessing user personnel protection. UL 2231 also requires certain critical safety functions to be evaluated for known and identified risks.
PPSs continue to rely on programmable components responsible for protective functions, such as decision to interrupt the circuit, auto-reclosure and auto-supervisory circuit functions. Evaluation according to UL 1998, the Standard for Software in Programmable Components, and UL 991, the Standard for Tests for Safety-Related Controls Employing Solid-State Devices, assesses inherent risks associated with programmable components responsible for safety-related functions.
Conclusion: Paving the Way for Safer EV Adoption
As EVs continue to penetrate the automotive market, the relevance of robust testing and certification cannot be overstated. Evaluating EVSE for compliance with UL Standards and those of other regulatory bodies not only helps protect individuals but also facilitates consumer confidence and industry growth.
As we look to the future of transportation, prioritizing safety through certified PPSs in EV infrastructure will be instrumental in achieving a safer, more reliable EV experience for everyone. Collaboration among manufacturers, code authorities and installers is essential in building this ecosystem, which ultimately paves the way for a more sustainable electric future.
