GIS, SIS, Or Eco-Friendly: Can You Distinguish Between These Switchgear Types?

Solid-Insulated Switchgear (SIS)

Core Features: Using solid insulating material (primarily high-performance epoxy resin) as the primary insulating medium, primary live components (such as vacuum interrupters, isolating fractures, busbars, etc.) are cast and encapsulated into modular "solid-sealed poles" using the APG (Automatic Pressure Gelation) process.

Insulating Medium: Solid epoxy resin.

Advantages:

1. Truly Environmentally Friendly: Completely eliminating SF₆ gas, eliminating the risk of greenhouse effects, and representing one of the mainstream technologies for environmentally friendly cabinets.

2. Smaller Size: High insulation design flexibility allows for extremely compact designs. 3. High Reliability: Also featuring a fully sealed or fully encapsulated structure, this design offers strong weather resistance and is maintenance-free.

Disadvantages:

1. Heat Dissipation Challenges: Epoxy resin has a lower thermal conductivity than gas, making heat dissipation a key challenge during high-current operation.

2. Partial Discharge: Tiny air gaps or defects within solid insulation can easily cause partial discharge, which can gradually worsen and is difficult to detect online.

3. Recycling: Epoxy resin materials are difficult to recycle at the end of their lifespan.

How to Identify: Open the cabinet door and you will see the core component, which is a yellow or orange epoxy resin casting (encapsulated pole).

Gas-Insulated Switchgear (GIS)

Core Features: Key components of the main circuit (such as circuit breakers, disconnectors, earthing switches, busbars, etc.) are sealed in a welded stainless steel gas tank, which is filled with SF₆gas or a SF₆gas mixture at a certain pressure.

Insulating and Arc-Quenching Medium: SF₆gas. This gas has extremely excellent insulating and arc-extinguishing properties.

Advantages:

1. Compact Structure: Because the insulation strength of SF₆ is much higher than that of air, the distance between conductors can be significantly reduced, resulting in a compact switchgear, saving space.

2. High Reliability and Maintenance-Free: The fully sealed structure makes it completely immune to external environmental influences, and the internal components require virtually no maintenance.

3. High Safety: Live parts are completely enclosed, providing excellent operator safety.

Disadvantages:

1. Environmental Issues: SF₆ is a prohibited strong greenhouse gas, and leaks can have long-term environmental impacts.

2. High Process Requirements: The welding and sealing of the gas tank are extremely demanding. Once a leak occurs, fault location and repair are extremely difficult.

How to Identify: The most distinctive appearance is the presence of one or more large, welded stainless steel sealed gas tanks, typically fitted with a pressure gauge or density relay.

Environmentally Friendly Switchgear

Core Features: Its core goal is to reduce or eliminate the use of SF₆ gas. Any switchgear that achieves this goal can be called an environmentally friendly switchgear.

It is not a single switchgear type, but rather encompasses multiple technical approaches:

Solid Insulation Switchgear: This refers to the solid-state switchgear described above and is currently the most mainstream technology for environmentally friendly switchgear.

2. "Environmentally Friendly Replacement" for Gas Cabinets: The SF₆ gas in the gas cabinet is replaced with an environmentally friendly inert gas, such as dry air or nitrogen (N₂). The structure remains the sealed gas box of the gas cabinet. However, because the insulation performance of these gases is significantly inferior to that of SF₆, to ensure insulation distance, these cabinets are typically larger than SF₆ gas cabinets.

3. Composite Technology: Insulation is achieved using a combination of "solid insulation + slightly positive pressure dry air/nitrogen."

How to Identify: Check the product nameplate, technical data, or manufacturer's promotional information. If it is clearly labeled "SF₆-free," "Zero-GWP," or "Green," and indicates that the insulating medium is dry air, nitrogen, or a solid material, it can be identified as an environmentally friendly cabinet.