1.2 Safety Standards for UL Energy Storage Systems
UL(Underwriter Laboratories Inc.) The Safety Laboratory is the most authoritative independent and profit-making professional organization engaged in safety testing and identification in the United States, and its main safety standards for electrochemical energy storage are as follows:
UL 1973 STANDARD FOR SAFETY ANSI CAN/UL-1973:2018，Batteries of Stationary,Vehicle Auxiliary Power and Light Electric Rail(LER)Applications
UL 9540 Energy Storage Systems and Equipment Test Standard
UL9540A Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems
UL1973 covers battery systems for energy storage in stationary applications such as photovoltaics, wind storage or UPS, as well as battery systems for light electric tracks and stationary railway applications, such as railway substations, and, in a similar way to IEC62619, covers common safety requirements. However, unlike IEC, UL does not plan to compile lithium battery safety standards for energy storage systems for power grid applications, and the battery range in the standard includes other types of batteries in addition to lithium-ion batteries, such as sodium-B batteries and flow batteries. The UL1973, which was newly revised in 2019, specifies safety-related requirements or test methods in detail from the aspects of structural requirements, electrical tests, mechanical tests, environmental tests, cell failure tests, and production line tests.
UL9540 is a safety standard for energy storage systems for three types of energy storage technologies (electrochemical energy storage, mechanical energy storage and thermal energy storage), which covers charging and discharging systems, control and protection systems, power conversion systems, communications, cooling and heat management systems, fire protection systems, fuel or liquid pipelines, containers, system installation, etc., including off-grid operation and grid-connected operation of energy storage systems. UL9540A is mainly used to evaluate the thermal runaway characteristics of battery energy storage systems, and selects the appropriate fire and explosion protection mechanism through test data, which is a standard for specific test methods. The purpose is to help suppliers clarify the separation requirements of the system from the wall, the heat generation of the system, the combustible parts, the type of gas produced by combustion and the selection of fire extinguishers.
In summary, the UL energy storage safety standard has the characteristics of comprehensive coverage, specificity and strong application, and is a relatively mature product safety standard.
1.3 Domestic Safety Standards for Energy Storage System Products
Different from IEC and UL, the national standard does not separate the safety standards of energy storage systems into standards, but stipulates them in chapters in technical specifications or operational management specifications. The following are national standards related to the safety requirements of lithium battery energy storage systems:
GB/T34131 Technical specifications for lithium-ion battery management systems for electrochemical energy storage power stations
GB/T36276 lithium-ion battery for power energy storage
GB/T36547 Electrochemical energy storage system access to the power grid technical regulations
GB/T36548 electrochemical energy storage system access to the power grid test specifications
GB/T36558 General technical conditions for electrochemical energy storage systems for power systems
GB/T36549 electrochemical energy storage power station operation indicators and evaluation
GB/T51048 electrochemical energy storage power station design specifications
Among them, the standards involving battery system safety are mainly GB/T34131GB/T36276GB/T36558. These standards have made a clear definition of some common terms, symbols, test items and test methods in the functional energy storage industry, and have played a leading role in the development of the domestic energy storage industry. In the battery or battery system’s initial charge and discharge energy, rate charge and discharge performance, energy retention and recovery ability, cycle performance and other tests related to battery capacity, the use of constant power charge and discharge mode for assessment, for the grid energy storage application has practical significance, to promote the healthy development of the energy storage industry. The tests directly related to safety have been charging test, overdischarge test, external short circuit test, crush test, drop test, low air pressure test, heating test, thermal runaway test, salt spray and high temperature and high humidity test, insulation performance test, and withstand voltage performance test. Battery management system BMS separately presents a technical specification, the relevant electromagnetic compatibility tests are specified in this standard, when testing, BMS does not need to be connected with the real battery into the system for testing. Such an arrangement is conducive to the separate inspection of BMS products, but the inspection of the battery system may be biased.
In addition to the national standard, the relevant domestic industry group alliances such as the energy industry of the National Energy Administration, the CEC of the China Electricity Council, the Zhongguancun Energy Storage Industry Technology Alliance CNESA, and the China Chemical and Physical Power Industry Association CIPAS have also issued the line (group) standard: NB/T42091 technical specifications for lithium-ion batteries for electrochemical energy storage power stations
TCIAPS0003 Secondary lithium-ion monomer batteries and battery system safety requirements for power energy storage systems
T/CEC172 Safety requirements and test methods for lithium-ion batteries for power energy storage
T/CNESA1000 Specification for Evaluation of Electrochemical Energy Storage Systems
T/CNESA1001 General technical requirements for DC power connectors for power energy storage
T/CNESA1002 Technical Specification for Battery Management Systems for Electrochemical Energy Storage Systems
Among them, NB/T42091 was released earlier than the national standard, TCIAPS0003 is mainly modified with reference to IEC62619, and T/CEC172 is based on the national standard, the battery safety related specifications and test methods are integrated into a standard document, except for individual articles and test methods, there is not much difference in general. The T/CNESA1000 released by the Zhongguancun Energy Storage Alliance combines the national standard and IEC standards and proposes a complete set of scoring methods. T/CNESA1001 standardizes the general technical requirements for DC power connection machines for power storage systems, and carries out detailed structural, electrical, and environmental adaptability requirements for connectors, terminals, seals, and cables used in the system. T/CNESA1002 is based on GB/T34131 the technical specifications of the battery management system have been improved and supplemented.
2 Comparative Analysis of These Safety Standards
In addition to the safety of the battery system, the safety of the external integrated system, including the energy storage inverter (PCS), is also an indispensable part. However, due to the difference in the power grid access requirements of various countries and regions, this part is not suitable for direct comparison, the scope of this study does not include the access part of energy storage and power grid, that is, PCS to the power grid part, mainly to study the safety standards of common lithium-ion battery systems. Therefore, the standards involved in this regard are mainly UL1973, IEC62619, GB/T36276 and GB/T34131. In order to facilitate the comparison of various aspects of the requirements in the standard, taking the UL standard as a reference, the standard clauses are divided into four categories: structural safety, battery body safety, system safety and environmental safety.