1. Select the circuit breaker corresponding to the voltage level based on the power grid level
The standard voltage (12/24/40.5/72.5/126/170/245/363/420/550/800/1100kV) is matched with the corresponding nominal voltage of the power grid. For example, for a 35kV power grid, a 40.5kV circuit breaker is selected. According to standards such as GB/T 1984/IEC 62271-100, the rated voltage is ensured to be ≥ the maximum operating voltage of the power grid.
2. Applicable scenarios for non-standard customized voltage
Non standard customized voltage (11/22/44/52/132/230/275/300/345/400/380/765kV) is used for special power grids, such as the renovation of old power grids and specific industrial power scenarios. Due to the lack of suitable standard voltage, manufacturers need to customize according to power grid parameters, and after customization, insulation and arc extinguishing performance must be verified.
3. The consequences of selecting the wrong voltage level
Choosing a low voltage level can cause insulation breakdown, leading to SF leakage and equipment damage; Choosing a high voltage level significantly increases costs, increases operational difficulties, and may also result in performance mismatch issues.

1. The core differences between porcelain column circuit breakers and tank circuit breakers—two main structural types of high-voltage circuit breakers—lie in six key aspects.
2. Structurally, porcelain column types are supported by porcelain insulation pillars, with open-layout components like arc extinguishing chambers and operating mechanisms. Tank types use metal-sealed tanks to encapsulate and highly integrate all core parts.
3. For insulation, the former relies on porcelain pillars, air, or composite insulating materials; the latter combines SF₆ gas (or other insulating gases) with metal tanks.
4. Arc extinguishing chambers are mounted on the top or pillars of porcelain columns for the former, while built inside metal tanks for the latter.
5. In application, porcelain column types suit outdoor high-voltage distribution with a dispersed layout; tank types adapt flexibly to indoor/outdoor scenarios, especially space-constrained environments.
6. Maintenance-wise, the former’s exposed components enable targeted repairs; the latter’s sealed structure reduces overall maintenance frequency but requires full inspections for local faults.
7. Technically, porcelain column types offer intuitive structure and strong anti-pollution flashover performance, while tank types boast excellent sealing, high SF₆ insulation strength, and superior resistance to external interference.

The leakage rate of SF₆ gas must be controlled at an extremely low level, typically not exceeding 1% per year. SF₆ gas is a potent greenhouse gas, with a greenhouse effect 23,900 times that of carbon dioxide. If a leak occurs, it can not only cause environmental pollution but also lead to a decrease in the gas pressure within the arc quenching chamber, affecting the performance and reliability of the circuit breaker.

To monitor the leakage of SF₆ gas, gas leakage detection devices are typically installed on tank-type circuit breakers. These devices help to promptly identify any leaks so that appropriate measures can be taken to address the issue.

The double-break structure is preferred, while the single-break structure is only suitable for scenarios with voltage ≤760kV and small short-circuit current. Special requirements for voltage equalization: ① The value of the voltage equalizing capacitor should be increased by 10%-15% compared with that of standard 800kV equipment (e.g., 2000pF for 756kV equipment and 1800pF for 800kV equipment); ② Adopt a double-ring nested voltage equalizing ring, with the ring diameter increased by 5%-8% compared with that of 800kV standard equipment; ③ The break spacing should be reduced in proportion to the voltage (e.g., 8%-10% reduction for 756kV compared with 800kV) to balance insulation performance and structural dimensions.