AIS vs GIS: How to Select Switchgear for Space, Maintenance and Duty

Air insulated switchgear (AIS) and gas insulated switchgear (GIS) can both serve medium-voltage distribution. The defensible choice satisfies the project’s clearances, service method, environment, extension plan and electrical duty. Compare the complete installation, not only cubicle width or price.

See Shenheng Power medium-voltage switchgear for the site’s product families. Keep the single-line diagram and fault study beside this comparison.

What AIS and GIS actually change

Decide by space and layout

GIS is often considered where land or building volume is constrained. Its cubicle width is not the whole footprint: cable boxes, control panels, lifting paths, pressure-relief provisions and maintenance clearances still need space. AIS may need more clearance, while a withdrawable arrangement can make breaker handling easier.

Ask for a GA drawing showing:

• front and rear service clearances, aisles and door swings;
• cable trench, gland-plate and termination space;
• lifting and removal paths for serviceable parts;
• bus-section, metering and protection interfaces; and
• reserved bays for future extension.

Compare maintenance as a work method

For AIS, define inspection access, cleaning, breaker withdrawal, earthing and interlock proving. For GIS, define compartment access, gas-density or pressure monitoring, approved handling equipment and the boundary between factory and site work.

1. List outage tasks: inspection, mechanism service, cable testing, relay testing and earthing verification.
2. Mark which tasks require isolation or specialist intervention.
3. Check that room access, lifting equipment, test points, spares and trained personnel support the tasks.
4. Put the method and documentation into the RFQ.

Read medium-voltage switchgear components and selection and the KYN28 buyer guide when reviewing candidate documents. Where the network concept includes a ring-fed distribution path, use the RMU selection guide to define the separate RMU questions; it does not replace the AIS/GIS duty and layout review above.

Let electrical duty set the gates

State nominal and highest voltage, normal and emergency load, short-circuit current and duration, making and breaking duty, insulation level, earthing arrangement, internal-arc access category and protection functions. IEC 62271-200 provides the standard context for AC metal-enclosed MV assemblies; the applicable edition belongs in the specification.

The supplier should return a model-specific schedule covering ratings, type-test evidence, interlocks, cable interfaces, environmental limits and extension boundaries. A GIS label does not remove the need for a fault study, and an AIS label does not prove an internal-arc or breaker duty.

RFQ decision sheet

1. One-line diagram, voltage, frequency, phase sequence and transformer interface.
2. Load schedule, motor or converter duty, harmonics and future capacity.
3. Fault level, withstand duration, peak withstand and breaker duties.
4. Insulation levels, internal-arc category and environment class.
5. GA constraints, cable entry, trench, lifting route and service aisles.
6. Maintenance philosophy, outage windows, tools, training and spares.
7. Protection, metering, communications, interlocking and testing.
8. Applicable IEC edition, local code and documentation deliverables.

A switchgear path for constrained MV rooms

If the room is constrained and the brief points toward a metal-enclosed GIS arrangement, review the Shenheng customized KYN28-12 switchgear system. This is a document-request path, not a blanket recommendation. Send duty, GA constraints, cable arrangement, protection schedule, service philosophy and standards, then request the current datasheet, GA drawing, type-test scope, interlock description and extension plan.

References

• IEC 62271-200 publication overview – standard scope and MV terminology.
• Hitachi Energy GIS overview – GIS enclosure and lifecycle context.
• Eaton VacClad-W AIS information – AIS metal-clad architecture.
• Schneider Electric medium-voltage switchgear – product-family context.
• Shenheng Power medium-voltage switchgear – product pathway.