Prioritize Matching Core Electrical Parameters
This is the fundamental prerequisite for selection; mismatched parameters can directly lead to serious failures such as insulation breakdown or interruption failure.
Rated Voltage: The circuit breaker's rated voltage must be at least 1.1 times the system's maximum operating voltage (e.g., selecting a 12kV-class product for a standard 10kV system). For altitudes exceeding 1,000 meters, an additional insulation margin of 10%–15% is required for every 1,000-meter increase in elevation.
Rated Current: Calculate the sum of the rated currents of all equipment in the circuit and multiply by a simultaneity factor of 1.2–1.5; the circuit breaker's rated current must exceed this value. When handling surge loads such as electric motors, the breaker must withstand starting currents 5–7 times the rated value, while also allowing a margin for load expansion over the next 3–5 years.
Short-Circuit Breaking Current: Select based on the system's prospective maximum short-circuit current. High-capacity products (40kA and above) are preferred for main incoming circuits and large substations, while 25kA–31.5kA units suffice for standard distribution substations, ensuring reliable interruption of fault currents.
Match Installation and Switchgear Cabinet Conditions
Installation Method Compatibility: For KYN28A withdrawable (middle-mounted) cabinets, prioritize truck-type units (e.g., VS1/ZN63 series) for convenient maintenance and replacement. For XGN fixed cabinets, choose fixed-type products to lower costs. For compact switchgear in confined spaces, side-mounted structures are suitable.
Insulation Structure Suitability:Standard insulation-cylinder types are sufficient for ordinary, dry distribution rooms. For harsh environments-such as coastal areas with high humidity, high altitudes, or frequent condensation-prioritize solid-sealed pole products; these offer superior resistance to pollution and condensation, as well as a higher insulation margin.