{
  "language": "en",
  "interfaceLanguage": "en",
  "url": "https://voltformer.com/articles/air-insulated-vs-gas-insulated-mv-switchgear-ais-vs-gis-selection",
  "id": "art-20",
  "slug": "air-insulated-vs-gas-insulated-mv-switchgear-ais-vs-gis-selection",
  "title": "Medium Voltage Switchgear Selection: Air-Insulated (AIS) vs Gas-Insulated (GIS)",
  "summary": "Technical comparison covering IEC 62271-200 LSC2B-PM metal-clad AIS, SF6 and Clean-Air GIS, up to 70% footprint reduction, Internal Arc Classification (IAC AFLR 25 kA 1s), and life-cycle maintenance.",
  "readTime": "8 min read",
  "date": "2026-08-05",
  "author": "Voltformer Medium Voltage Switchgear Engineering",
  "category": "Medium Voltage Switchgear",
  "tags": [
    "MV Switchgear",
    "AIS",
    "GIS",
    "IEC 62271-200",
    "IAC AFLR"
  ],
  "contentMarkdown": "### 1. Medium Voltage Switchgear Architecture\n\nSelecting medium-voltage switchgear (12 kV to 36 kV) requires evaluating civil room space costs, ambient harshness (humidity, dust, chemical pollution), and maintenance access.\n\n### 2. Comparative Engineering Evaluation Matrix\n\n| Engineering Parameter | Air-Insulated Metal-Clad AIS (IEC 62271-200) | Gas-Insulated Switchgear GIS (SF6 / Clean Air) |\n|---|---|---|\n| **Insulation Medium** | Ambient Air (Phase clearance: 120-220 mm) | $SF_6$ / Synthetic Air ($1.3 - 1.5\\text{ bar abs}$) |\n| **Footprint per Feeder (36 kV)** | $1000\\text{ mm width} \\times 2250\\text{ mm depth}$ | **$600\\text{ mm width} \\times 1100\\text{ mm depth}$ (-65% to -70%)** |\n| **Loss of Service Continuity** | **LSC2B-PM (Partition Class Metallic)** | LSC2A / LSC2B sealed tank |\n| **Internal Arc Withstand** | IAC AFLR 25 kA / 31.5 kA 1.0 s | IAC AFLR 25 kA / 31.5 kA 1.0 s |\n| **Environmental Immunity** | Sensitive to condensation, dust, marine salt | **100% Hermetically Sealed (IP65 stainless steel tank)** |\n| **Cable Termination System** | Air bushings with heat-shrink boots | Outer cone / Inner cone plug-in bushings (EN 50181) |\n| **Maintenance Interval** | 3-5 years visual inspection & busbar torquing | **Maintenance-free primary circuit for 30+ years** |\n\n### 3. Internal Arc Classification (IAC AFLR)\n\nPer **IEC 62271-200**, switchgear must pass internal arc testing to protect personnel:\n- **A:** Authorized personnel access only.\n- **F, L, R:** Front, Lateral, and Rear protection.\n- **25 kA / 31.5 kA 1.0 s:** Fault current magnitude and duration.\n\n### 4. Eco-Friendly Clean-Air GIS Trends\n\nModern regulations phase out greenhouse gas $SF_6$ in favor of Clean-Air ($80\\% N_2 + 20\\% O_2$) with vacuum interrupters, achieving **Global Warming Potential ($GWP$) $< 1$**.\n\n*Reference: IEC 62271-200:2021; IEEE Std C37.20.2-2022; CIGRE TB 740.*",
  "contentLanguage": "en",
  "sources": []
}