ANALYSIS OF ELECTRICAL SAFETY STANDARDS IN YUTONG ELECTRIC BUSES

ABSTRACT

This article analyzes the YESS (Yutong Electric Safety Standards) system used in Yutong electric buses and its role in ensuring electrical safety. The study examines in detail the five levels of protection provided by the YESS system, including vehicle safety, system safety, battery pack safety, component safety, and monitoring safety. It also considers the protection of batteries from internal and external risk factors, the use of advanced nitrogen protection technology, and real-time monitoring capabilities. The results indicate that the YESS system significantly improves the safety of electric buses and complies with international standards.

АННОТАЦИЯ

В данной статье проведён анализ системы YESS (Yutong Electric Safety Standards), применяемой в электробусах Yutong, и её роли в обеспечении электрической безопасности. В исследовании подробно рассмотрены пять уровней защиты системы YESS, включая безопасность транспортного средства, системы, аккумуляторных блоков, компонентов и мониторинга. Также изучены вопросы защиты аккумуляторов от внутренних и внешних факторов риска, использование азотной защитной технологии и возможности мониторинга в режиме реального времени. Полученные результаты показывают, что система YESS значительно повышает уровень безопасности электробусов и соответствует международным стандартам.

Keywords: Yutong electric buses, YESS system, electrical safety, battery safety, nitrogen protection system, thermal management, short circuit, monitoring system, LFP batteries, ECE R100 standard.

Ключевые слова: электробусы Yutong, система YESS, электрическая безопасность, безопасность аккумуляторов, азотная защитная система, тепловое управление, короткое замыкание, система мониторинга, аккумуляторы LFP, стандарт ECE R100.

INTRODUCTION. On August 31, 2021, China held the Yutong Power Battery Safety Protection Standard conference and battery testing event, which was broadcast live worldwide. During the event, the latest technology in electric bus safety - YESS (Yutong Electric Safety Standards) - was presented. This is the world’s first electric vehicle safety technology applied in mass production for commercial vehicles. YESS offers five levels of protection: Vehicle safety; System safety; Battery pack safety; Component safety; Monitoring safety.

Figure 1. Structure of Yutong electric buses

Vehicle safety is integrated into the system at the design stage. Battery packs are installed in the upper, rear, and lower parts of the bus body. It fully takes into account collision scenarios involving heavy trucks and passenger cars. The targeted improvement of the collision protection structure meets the most stringent standards and comprehensively enhances collision safety performance.

The integrated structural protection effectively reduces the risk of short circuits and resulting fires caused by the penetration of foreign objects into the battery under extreme conditions (Fig. 1). At the same time, a protective layer made of steel plates and insulating materials is installed between the battery compartment and the passenger cabin. It can withstand exposure to flames at temperatures of 1000-1300°C for a long time, and the fire cannot penetrate it. This protective layer ensures that passengers have sufficient time to evacuate the bus in extreme situations.

METHODOLOGY. Yutong uses the world’s first nitrogen protection system designed for batteries. This system is based on aviation-grade high-purity nitrogen extraction technology. It replaces the oxygen-containing air inside the battery pack with nitrogen, ensuring that battery cells are in an inert nitrogen environment. This effectively blocks the interaction between combustible materials and oxygen and prevents further damage to the battery cells after thermal overheating (Fig. 2). In addition, it operates in conjunction with the BMS system’s 24-hour full-time monitoring. It detects the sealing of the battery pack and the nitrogen concentration in real time and provides early warnings. This significantly improves the safety and reliability of the battery.

Figure 2. Battery cell overheating protection system

Battery pack safety. In-depth study of short-circuit protection devices prevents the occurrence of unprotected “blind spots.” All battery packs are equipped with short-circuit protection devices that provide multi-level coordinated system protection. In the event of external overloads or short circuits, the faulty circuit is disconnected in a timely manner. This ensures complete protection against short circuits and overloads under all operating conditions and prevents the escalation of battery-related safety incidents at the system level (Fig. 3).

Figure 3. Battery cell overheating protection system

Multi-level structure with double safety (Fig. 4): A protective layer made of mica is installed inside the upper cover of the block. An ASC protective cover is added to the outer side of the battery pack. As mentioned above, it can withstand exposure to flames at temperatures of 1000-1300°C for a long time, and the fire cannot penetrate it.

Figure 4. Multi-level structure with double safety

Component safety. Special attention has been paid to the development of liquid-based heating technology, which, together with liquid cooling technology, forms an integrated thermal management system (Fig. 5). This system ensures the normal operation of the battery in low-temperature environments and significantly reduces the number of high-voltage components used in the battery pack, thereby enabling control over the risk of high-voltage-related failures. When combined with external insulation measures of the battery, it is possible to reduce the temperature difference within the battery system by up to 50%. In other words, while the temperature difference in conventional batteries ranges from 15-20°C, in the YESS system this indicator is reduced to 7-10°C.

Figure 5. Liquid-based battery protection

Monitoring safety. A comprehensive monitoring system operating 24/7 has been developed to track battery data in real time. Through this system, battery safety is fully controlled at all times and in all locations. This ensures an increased level of safety, the ability to operate under any weather conditions, and adaptability to road conditions.

Yutong buses are equipped with world-class lithium iron phosphate (LFP) batteries. These batteries have successfully passed dozens of rigorous safety tests, including overcharging and over-discharging, short circuit, impact, penetration, compression, heating, vibration, and seawater tests. All battery packs fully comply with the European EU ECE R100 safety standard. The ECE R100 standard includes more than 20 tests related to electrical safety, impact, short circuit, and thermal stability of batteries. The ASC protective cover protects the battery from fire, extreme cold, sunlight, and intense heat. In cooperation with the liquid cooling/heating system, it ensures safe operation at temperatures ranging from -40°C to 55°C.

RESULTS. According to research data, more than 30% of failures in electric vehicle batteries are caused by external damage. Therefore, YESS is not limited to protecting only the battery but covers the entire vehicle, enclosing the battery within a high-strength, frame-like structure with a safety distance to prevent collisions.

Regarding internal failures (such as ISC – internal short circuit and TR – thermal runaway), the YESS safety system is the first in the industry to apply nitrogen protection technology. This technology completely displaces oxygen from the battery enclosure to prevent combustion.

When it comes to separating external and internal risk sources, YESS provides multi-level protection of thermo-electric connections to ensure battery safety.

Component protection can be applied even under extreme conditions, including high voltage. It uses a multi-layer liquid thermal technology suitable for commercial use to prevent overheating of the battery enclosure.

In addition, YESS performs real-time monitoring. It continuously monitors the condition of batteries across all aspects and offers a mobile application with intelligent cloud management capabilities.

With full confidence in this technology, Yutong has equipped battery packs according to the YESS standard and tested them under extreme conditions such as overheating and overcharging, proving their safety and stability.

Table 1.

Values

CONCLUSION. Since entering the market of new energy vehicles in 2008, Yutong has sold more than 150,000 units worldwide to date, with a total operating mileage reaching 24.8 billion km. This is equivalent to circling the Earth approximately 620,000 times. Striving to eliminate concerns regarding electric vehicle safety, Yutong has reached a new level with its comprehensive YESS safety solution, which views the entire vehicle as an integrated system.

Yutong continues to modernize its technology and improve the YESS system to ensure that every journey on Yutong electric buses is safe, environmentally friendly, and comfortable for passengers.

References:

1. Yutong Bus Co., Ltd. Yutong Power Battery Safety Protection Standard (YESS) Conference Materials. Zhengzhou, China, 2021.
2. UNECE. Regulation No. 100 – Uniform Provisions Concerning the Approval of Vehicles with Regard to Specific Requirements for the Electric Power Train. United Nations, 2018.
3. JSC “Toshshahartranskhizmat”. Annual Reports on the Technical Operation of Buses. Tashkent, 2022–2024.
4. Yutong Bus Co., Ltd. Technical Specifications for Yutong E12 and ZK6126HG Buses. Zhengzhou, China, 2021–2023.
5. Zhang, X., Li, J. Safety Analysis of Lithium-Ion Batteries in Electric Vehicles. Journal of Power Sources, 2020.
6. International Association of Public Transport (UITP). Electric Buses for Urban Transport: Global Overview. Brussels, 2021.
7. Chen, M., et al. Battery Safety Technologies for Electric Vehicles: A Review. Renewable and Sustainable Energy Reviews, 2019.
8. Khamroyev, R.K. Analysis of the Potential for the Use of Electric Vehicles and Their Operational Performance. Universum: Technical Sciences, 2021, No. 12(93), pp. 90–92.