Selection Steps: A Five-Step Process
The selection of high-voltage switchgear involves five steps: voltage level → main wiring scheme → rated parameters → cabinet structure → short-circuit verification.
Industry experts note that the selection process follows this sequence: voltage level (10kV/35kV), main wiring (single/double busbar), rated parameters (current/breaking capacity), cabinet structure (e.g., KYN28 metal-clad/withdrawable type), and short-circuit verification (dynamic and thermal stability).
Selection should allow for a margin (to accommodate load growth), and type testing (GB/T 3906) serves as the basis for selection.
Five-Step Process
- Voltage level: System voltage (10kV/35kV), matching the power grid;
- Main wiring scheme: Single busbar/double busbar/ring main (power supply reliability);
- Rated parameters: Rated current (internal equipment) and breaking current (short-circuit level);
- Cabinet structure: KYN28 (metal-clad/withdrawable)/fixed type/XGN (structural form), selected based on the application;
- Short-circuit verification: Dynamic and thermal stability (short-circuit current verification), checking the cabinet body and components.
Key Selection Points
First, allow for a margin.
Include a margin for current/capacity (accounting for 20%–30% load growth) to accommodate future expansion.
Second, rely on test data.
Verify type test reports (GB/T 3906) regarding breaking capacity and internal arc withstand to ensure a sound basis for selection.
Third, ensure environmental compatibility.
Selection based on environmental conditions (altitude, temperature, pollution levels) and specific application requirements (e.g., high-altitude or anti-pollution capabilities).
Also, consider the manufacturer’s technical proposal and verify the specifications against the selection calculations.
Pitfalls to Avoid
First, “insufficient specifications”—specifically, inadequate breaking capacity (posing a short-circuit risk);
always verify breaking capacity.
Second, “lack of type testing”—avoid units lacking type tests (often associated with obscure brands) and always check the type test reports.
Third, “environmental oversight”—failure to account for derating due to high altitude or high temperatures;
ensure selection aligns with the actual operating environment.
Trends and Recommendations
High-voltage switchgear is moving toward “intelligence,” with trends favoring smart switchgear (featuring online monitoring) and eco-friendly units (SF6-free).
For those responsible for selection, the recommended approach is: “five-step selection, adequate safety margins, and verification through testing.”
Accurate selection ensures safe and stable power supply.
