1. Classification by Voltage Level
| Category | Voltage Range | Typical Applications | International Standards |
|---|---|---|---|
| Low-Voltage (LV) Switchgear | ≤1 kV (AC) | Building power distribution, factories, commercial facilities | IEC 61439 (GB 7251) |
| Medium-Voltage (MV) Switchgear | 1 kV–35 kV (or up to 66 kV*) | Regional power distribution, industrial substations, wind farm grid connections | IEC 62271 (GB 3906) |
| High-Voltage (HV) Switchgear | ≥35 kV (or ≥66 kV*) | Transmission networks, power plant outlets, substation hubs | IEC 62271 (GB 11022) |
Note: Voltage classifications vary by country (e.g., ANSI defines MV up to 69 kV in the U.S., while Europe often uses 36 kV as the upper MV limit).
2. Technical Features Comparison
| Feature | LV Switchgear | MV Switchgear | HV Switchgear |
|---|---|---|---|
| Insulation | Air-insulated | Air/SF6 gas/vacuum insulation | SF6 gas/composite insulation/oil insulation |
| Circuit Breaker | MCCB, MCB | Vacuum/SF6 circuit breakers | SF6 breakers, GIS (Gas-Insulated Switchgear) |
| Design | Drawer-type/fixed, modular | Metal-clad (e.g., KYN28), compartmentalized | Outdoor installation, highly integrated GIS |
| Protection | Overload, short-circuit, leakage | Relay protection, arc flash detection | Differential protection, auto-reclosing |
| Common Models | GCS, MNS, GGD | KYN28, XGN15, UniGear ZS1 | GIS (e.g., ABB ELK-4), AIS (Air-Insulated Switchgear) |
3. Application Scenarios
- LV Switchgear:
- End-user distribution: buildings, data centers, solar inverters.
- Motor control: MCC panels for pumps, fans.
- Example: GCS drawer-type cabinets distributing 380V power in commercial buildings.
- MV Switchgear:
- Regional grids: 10kV distribution in industrial parks.
- Renewable energy: 35kV collector systems for wind farms.
- Example: KYN28-12 switchgear for 10kV feeder protection in substations.
- HV Switchgear:
- Transmission networks: 110kV+ substations.
- Power plant integration: GIS connecting generators to transformers.
- Example: 500kV GIS stations for ultra-high-voltage transmission.
4. Safety & Maintenance
- LV: Regular inspections of contacts and cooling; basic electrical certification required.
- MV: Mandatory five-prevention interlocking; maintenance requires de-energizing and HV certification.
- HV: Remote monitoring/robotic maintenance; critical insulation checks (e.g., SF6 gas purity).
5. Key Differences Summary
| Aspect | LV | MV | HV |
|---|---|---|---|
| Core Function | Power distribution | Regional protection | Bulk power transmission |
| Complexity | ★★☆ | ★★★ | ★★★★ |
| Cost | Low (1k–1k–10k) | Medium (10k–10k–100k) | High (100k–100k–1M+) |
| Failure Impact | Localized (single site) | Regional (community) | Grid-wide (intercity) |
FAQs
Q1: Can MV switchgear replace LV switchgear?
No. Mismatched insulation and breaking capacity may cause breakdowns.
Q2: GIS vs. AIS in HV systems?
GIS uses SF6 gas for compact urban substations; AIS relies on air insulation for cost-effective rural setups.
Q3: How to choose voltage levels for projects?
- LV: End-user equipment (<1 km supply radius).
- MV: Regional distribution (1–20 km).
- HV: Long-distance transmission (>20 km).
This comparison ensures optimal selection of switchgear for safety, efficiency, and cost-effectiveness in power systems.