1. Model Code Interpretation
Disconnector model codes typically include design standards, voltage class, current capacity, and application scenarios. Examples:
GN30-12 and GN19-12C:
GN: "Indoor High-Voltage Disconnector" (G = Disconnector, N = Indoor).
Numeric codes: "30" or "19" = design series; "12" = rated voltage 12 kV; "C" = equipped with grounding blade.
Current rating: E.g., "630A" indicates a rated current of 630A. Selection should exceed the system's maximum load by 20% margin.
Additional symbols:
ST: Pollution-resistant type.
CST: Plateau-adapted pollution-resistant type (for harsh environments).
Key Parameter Analysis
Rated voltage: Must ≥ system's maximum operating voltage (e.g., 12 kV for 10 kV systems).
Short-time withstand current (Icw): Must match system short-circuit current. Formula:
Icw≥Prospective short-circuit current×Fault duration/Nominal time.Icw≥Prospective short-circuit current×Fault duration/Nominal time.
Mechanical endurance:
M2 class (10,000 cycles): General applications.
M3 class (30,000 cycles): Frequent operations (e.g., railways/industrial systems).
2. Outdoor vs. Indoor Disconnector Differences
Protection rating:
Outdoor: IP65 or higher (dust/waterproof), e.g., GN19-12CST (plateau/pollution-resistant).
Indoor: Typically IP40, with attention to cabinet heat dissipation.
Case study: Indoor units mistakenly installed outdoors caused insulation failure due to rainwater ingress.
Material & corrosion resistance:
Coastal areas: 304 stainless steel or galvanized coating.
Arctic regions: -40°C low-temperature certification.
Operation mechanism:
Outdoor: Three-phase linkage mechanism.
Indoor: Manual or single-pole electric operation.
Maintenance:
Outdoor: Regular dust removal and anti-corrosion inspection.
Indoor: Focus on contact oxidation and lubricant degradation.
3. Selection Pitfalls & Recommendations
Pitfall 1: Ignoring environmental adaptability. Example: Using standard models in plateau areas without derating caused overheating.
Pitfall 2: Confusing disconnectors with load switches, risking arc faults.
Recommendations:
Prioritize environmental certifications (e.g., pollution/plateau ratings).
Validate Icw and mechanical endurance against operational demands.
Use outdoor-specific designs for exposed installations.