Electrical Complete Equipment: A Guide to Modern Power Distribution Solutions

2026-08-14 19:30:29

High-voltage switchgear is the backbone of any medium-voltage distribution network. It isolates faults, protects transformers and routes power through ring networks, substations and industrial plants. Choosing the correct technology—gas-insulated, solid-insulated, air-insulated or metal-clad withdrawable—depends on voltage level, environment, space and operational requirements.

Common HV Switchgear Types

Gas-Insulated Ring Main Units (RMUs)

Gas-insulated RMUs seal all live parts inside a stainless-steel tank filled with an insulating gas. This construction makes the equipment immune to dust, moisture, pollution and small animals, so it performs reliably in harsh outdoor or coastal environments.

• Rated voltage: 12 kV / 24 kV

• Rated current: 630 A typical

• Short-circuit withstand: 20 kA / 25 kA common

• Enclosure protection: up to IP67 for the gas tank, IP4X for the cabinet

• Applications: urban ring networks, cable branch boxes, compact substations, industrial distribution

Environmentally friendly variants use dry air instead of SF₆, eliminating greenhouse-gas concerns while keeping the same compact footprint.

Solid-Insulated RMUs

Solid-insulated switchgear casts live conductors, vacuum interrupters and load-break switches in epoxy resin. The result is a fully insulated, maintenance-free assembly with excellent performance in high humidity, high altitude or heavily polluted areas.

• Rated voltage: 12 kV

• Frequency: 50 Hz

• Insulation: solid epoxy, no gas filling required

• Altitude: suitable up to 4,000 m

• Protection: IP67 live parts, IP3X enclosure

Because there is no gas to monitor, solid-insulated RMUs are often chosen for remote or unmanned substations.

Air-Insulated RMUs

Air-insulated RMUs use atmospheric air as the primary insulation medium and are usually the most economical choice for indoor switch rooms. They use SF₆ or vacuum load-break switches and are widely deployed in city distribution networks, residential substations and commercial buildings.

• Rated voltage: 12 kV / 24 kV

• Enclosure: metal-enclosed, IP3X or IP4X

• Standards: IEC 62271-200, GB 3906

Metal-Clad Withdrawable Switchgear

For applications that require frequent operation, protection and monitoring, metal-clad withdrawable switchgear offers the highest flexibility. Circuit breaker trucks can be withdrawn for maintenance without de-energizing the entire panel.

• KYN28-12: 3.6 / 7.2 / 12 kV, currents up to 3,150 A, designed for indoor substations and industrial plants.

• KYN61-40.5: 40.5 kV class, used in high-voltage substations, power plants and large industrial facilities.

These panels comply with GB 3906, GB/T 11022, DL/T 404 and IEC 298, and they support five-prevention interlocking for operator safety.

Selection Checklist for HV Switchgear

1. Confirm system voltage and short-circuit level.

2. Determine indoor or outdoor installation and required IP rating.

3. Choose insulation medium: SF₆, dry air, solid epoxy or air.

4. Decide on fixed or withdrawable circuit breaker configuration.

5. Plan for future expansion and automation interfaces.

6. Verify compliance with IEC, GB or local utility standards.

Frequently Asked Questions

What is the advantage of a gas-insulated RMU over air-insulated?

Gas-insulated RMUs are much more compact and immune to environmental contamination. They are ideal for outdoor cabinets, coastal areas and places with limited space.

When should I choose solid-insulated switchgear?

Choose solid-insulated switchgear when you need maintenance-free operation in high humidity, high altitude or polluted environments, and when you want to avoid gas handling entirely.

Is metal-clad switchgear necessary for a simple substation?

For simple ring-network or transformer substations, an RMU is usually sufficient. Metal-clad withdrawable switchgear is better for large substations, generator outlets and circuits that require frequent switching or advanced protection.

Need Help Selecting HV Switchgear?

Our team can recommend the right RMU, metal-clad panel or compact substation for your voltage level and environment. For technical datasheets and a project-specific proposal, feel free to consult us via email.