SafePlus Ring Main Units Ensure Uninterrupted Power for China’s Largest-Diameter Undersea Shield Tunnel
On January 21, 2025, Shenzhen achieved a major milestone in transportation construction. The Mawan Undersea Tunnel, China’s largest-diameter undersea shield tunnel, was officially opened to traffic. It is located in the Guangdong-Hong Kong-Macao Greater Bay Area. The tunnel starts from Yueliangwan Avenue, crosses Qianhai Bay northward, and ends at Xixiang Avenue. Its total length is about 8.05 kilometers, including two shield tunnels with a maximum excavation diameter of 15.5 meters. Notably, 1.1 kilometers of the tunnel is underwater, making it Shenzhen’s first real cross-sea tunnel. Its opening not only breaks the transportation barrier between Qianhai and Xixiang in western Shenzhen but also provides strategic support for the interconnection of the Greater Bay Area’s road networks.
However, the stable operation of this “undersea giant” depends entirely on reliable power supply.
The seabed stratum crossed by the tunnel has extremely high chloride ion content. Its corrosiveness is much stronger than that of ordinary land environments. Furthermore, the interior of the tunnel remains humid and hot for a long time. Water vapor and corrosive substances in the air mix, which puts forward strict requirements for the performance of power distribution equipment. More importantly, as a key urban transportation infrastructure, the critical loads in the tunnel—such as emergency lighting, ventilation systems, and fire-fighting equipment—must be supplied with “zero-interruption” power. If a power failure occurs, it may lead to traffic paralysis and even trigger safety accidents.
Faced with this complex challenge, ABB
a global leader in the electrical and automation industry, cooperated closely with Shenzhen Auster Electric Technology Co., Ltd. A customized power distribution solution centered on the SafePlus series ring main units was developed for the Mawan Undersea Tunnel. This solution is not a simple combination of equipment. Instead, in-depth research and development and scenario-specific design were carried out based on the actual situation of the tunnel. By this means, the alignment between power distribution needs and power supply continuity goals is realized.
From the design perspective, the solution is highly consistent with the design institute’s dual-ring network concept.
Two independent power sources are configured for each power distribution room. This “double insurance” design ensures that if one power source fails, the other can be switched on immediately. Thus, power supply interruptions caused by single power source failures are fundamentally avoided. At the same time, the tunnel has limited space and complex equipment installation conditions. To solve this problem, the equipment layout and installation process were optimized. The entire power distribution system is like “power armor” tailored for the tunnel—it does not occupy too much space and can maximize the protection effect.
In terms of product performance, ABB’s SafePlus series ring main units show strong advantages.
These units adopt a fully insulated and sealed structure. All live components are sealed in a gas tank welded by a fully automatic robot. This design fundamentally isolates internal components from humid air and corrosive substances. In addition, the units are equipped with a reliable mechanical interlock device, which can standardize the on-site operation sequence and prevent faults caused by human operation errors. Special pressure relief holes and pressure relief channels are also set up to ensure the safety of operators.
Modular design is another prominent feature of the SafePlus series ring main units.
These units adopt a structure where six units share one gas chamber.
Even if a single gas chamber fails, only that gas chamber needs to be shut down. The other gas chambers can resume power supply in a short time, which greatly reduces the impact range of the fault and the recovery time. Moreover, the circuit breaker of the units uses a German-imported vacuum interrupter. Its vacuum degree is less than 10⁻⁸ mbar. Combined with high-purity copper-chromium alloy and a rotating contact design, it ensures strong breaking capacity, which perfectly meets the tunnel’s demand for high reliability of power distribution equipment. In addition, the gas tank of the units has an IP67 protection level and a compact size. This not only ensures the stable operation of the equipment in the harsh tunnel environment but also effectively reduces the space occupation cost, leaving more space for the layout of other facilities in the tunnel.
Li Haiqun, General Manager of Shenzhen Auster Electric Technology Co., Ltd., said when talking about this cooperation: “The ABB SafePlus series ring main unit solution and the special tunnel engineering solution can adapt to all scenarios from voltage level to capacity range relying on their modular design and intelligent configuration system. This on-demand customization capability allows us to quickly and accurately meet the needs of power grid users and truly realize the agile response from design to delivery.”
Luo Hui, Head of ABB Electrification China’s Power Distribution Systems Business Unit, emphasized:
“This cooperation is the result of the in-depth integration of ABB’s technical advantages and Auster Electric’s channel capabilities. We are very honored to provide a power distribution solution for this key project of the Mawan Undersea Tunnel and help improve the reliability of the tunnel’s power system. In the future, ABB will continue to explore innovations in the smart grid field with partners based on the integration of technological iteration and market demand. We will give full play to our expertise in urban power grid upgrading, transportation infrastructure, and new energy infrastructure to help users improve their competitiveness in design, construction, and operation and jointly build a safe, intelligent, and efficient power distribution ecosystem.”
In fact, this is not the first time ABB has supported major transportation infrastructure projects in China.
Over the years, ABB has been committed to empowering China’s transportation construction with technology. From the bridge-tunnel hybrid corridor of the Hong Kong-Zhuhai-Macao Bridge to the Yingbin 3rd Road Tunnel of Shanghai Hongqiao Hub, from the Qinling Zhongnanshan Tunnel and Chongqing Fuling Juyun Shilongshan Tunnel to the urban tunnels around sports venues in Beijing and Hangzhou, ABB’s power distribution equipment can be seen everywhere. As a global technology leader with a history of more than 140 years, ABB integrates engineering experience and digital technology. It continuously injects “electrical power” into the high-quality development of China’s transportation industry and helps build a more sustainable and efficient future transportation network.
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