Core Electrical Parameter Matching Standards
These are mandatory requirements for selection; the equipment must precisely match the system conditions at the installation site:
Rated Voltage and Insulation Level:The rated voltage of the circuit breaker must be greater than or equal to the system's maximum operating voltage (e.g., 12kV class for 10kV systems; 40.5kV class for 35kV systems). Power-frequency withstand voltage and lightning impulse withstand voltage must comply with the GB 1984 standard; for high-altitude locations, the insulation margin must be increased by 10% for every 1,000m rise in elevation.
Rated Current: The rated current must be greater than or equal to the circuit's maximum continuous operating current. A margin of 1.2 to 1.5 times should be reserved to accommodate load expansion over the next 3–5 years and prevent future overheating due to overload.
Short-Circuit Breaking Capacity: The rated short-circuit breaking current must be greater than or equal to the prospective maximum short-circuit current at the installation site (common specifications include 20kA, 25kA, and 31.5kA). Corresponding short-time withstand current and duration requirements must also be met to ensure dynamic and thermal stability.
Protection Coordination Verification: The ratio of the single-phase-to-ground short-circuit current at the end of the line to the circuit breaker's instantaneous trip setting current must be ≥1.25. This ensures precise protection operation during faults and achieves selective coordination with upstream and downstream protection devices.
Structural and Operating Mechanism Selection Standards
Mechanical configurations should be selected based on operating frequency and installation conditions:
Operating Mechanism Type: Spring-operated mechanisms require no external power source, offer high reliability, and suit most standard applications. Permanent magnet mechanisms feature fewer components and low maintenance requirements, making them ideal for frequently operated renewable energy plants.
Mechanical Life Requirements: For standard applications, the mechanical life should be ≥10,000 operations (Class M2). For distribution network automation scenarios requiring multiple automatic reclosing operations, models with higher mechanical life ratings should be prioritized.
Installation and Enclosure Protection: The protection rating for outdoor applications must be at least IP54; IP65 or higher is recommended for coastal areas with high salt spray or dusty environments. Enclosures should be made of corrosion-resistant stainless steel to meet sealing and anti-corrosion requirements for long-term outdoor operation.