Worlds First 550 kV Bypass Triggered Gap Successfully Passes All Type Tests

Recently, a Chinese manufacturer of bypass triggering devices, in collaboration with numerous enterprises, successfully developed the world’s first 550 kV bypass triggering gap for explosion prevention in ultra-high-voltage (UHV) converter transformers. The device has now passed the long-duration current-carrying pressure withstand test, completing all required validation tests. This milestone marks the successful development of a sub-millisecond ultra-high-speed bypass protection device based on a novel principle and application, filling an international technological gap.

Converter transformers are critical components in UHV DC transmission projects. In the event of an internal short-circuit fault, high-energy arcs in transformer oil rapidly generate large volumes of high-temperature, high-pressure gas. The resulting mechanical shock can crack the transformer tank or bushings, potentially triggering explosive combustion of the hot gas—a serious threat to grid safety that urgently demands a solution. To address this, the Chinese manufacturer proposed a new high-speed bypass triggering gap based on an innovative principle, designed to rapidly divert and extinguish internal arcs to prevent explosions.

Responding proactively to strategic requirements from State Grid Corporation of China, the manufacturer took the lead in forming a joint R&D task force with multiple enterprises and invited power industry experts to evaluate and validate the technical approach. Within just six months, the team accomplished key breakthroughs in:

• Bipolar sequential plasma jet conduction,

• Self-magnetic field arc rotation control,

• High-current arc erosion resistance and rapid dielectric recovery,

• Highly reliable measurement and control systems, and

• High-potential control enclosures featuring thermal insulation, anti-condensation, and electromagnetic interference (EMI) shielding.

The newly developed 550 kV bypass triggering gap features a single-break design and bilateral triggering technology. When triggered, exploding wires in both upper and lower electrode chambers simultaneously eject plasma jets toward each other, enabling the SF₆ gas gap to conduct within 1 millisecond—even under extremely low arc voltage conditions in oil. This rapidly diverts and extinguishes the internal arc in the converter transformer. After the AC circuit breaker interrupts the fault current, the arc between the gap electrodes is extinguished, significantly reducing both arcing duration and cumulative energy in the transformer, thereby effectively mitigating explosion risks. Additionally, this device can provide ultra-fast fault bypass protection for critical equipment such as power electronic valve groups, further enhancing the safety and stability of UHV DC transmission systems.

Looking ahead, the Chinese bypass triggering device manufacturer will continue to adhere to market-driven innovation, guided by a strong sense of political responsibility and historical mission. Leveraging the synergies of industry–academia–research collaboration, the company will persistently advance core technology development and contribute “Pinggao strength” to elevating China’s hard power in energy and electric power technologies.