The testing of indoor load switches should cover their entire lifecycle, focusing on four core aspects: "ensuring reliable insulation, normal mechanical operation, safe switching capability, and operational compatibility." The main testing categories include:
1. Insulation Performance Testing: Use a megohmmeter to measure insulation resistance between phases, from phase to ground, and between moving and fixed contacts (≥0.5 MΩ for low voltage, ≥1000 MΩ for high voltage). High-voltage switches require additional power-frequency withstand voltage tests (e.g., a 10kV switch withstands 42kV for 1 minute without breakdown or flashover).
2. Mechanical and Contact Testing: Perform 3–5 open/close operations to verify smooth operation without jamming and compliance with travel specifications. Measure contact resistance using a DC double-arm bridge (≤50 μΩ). Simultaneously, verify terminal tightening torque and grounding continuity (grounding resistance ≤4 Ω).
3. Operational Status Monitoring: While under load, use an infrared thermometer to measure temperature rise at terminals and contacts (≤60K, with a maximum difference of ≤10K between phases). Periodically re-measure insulation resistance (a decrease of no more than 30% compared to initial values).
4. Special Compatibility Testing: For switches equipped with fuses, simulate a fault to verify that the switch can reliably trip after the fuse blows. In humid or high-dust environments, monitor cabinet humidity and clean insulating components regularly.
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