Medium Voltage Switchgear Glossary

Direct answer: This glossary explains common terms used in RMU, GIS, AIS, MV switchgear and compact-substation projects. It is intended for EPC teams, utilities, distributors, panel builders and industrial buyers preparing technical enquiries.

RMU — Ring Main Unit

Compact medium-voltage switchgear used for ring-network distribution, feeder switching and transformer protection.

GIS — Gas-Insulated Switchgear

Switchgear whose primary live parts are enclosed in a controlled gas or sealed-insulation system.

AIS — Air-Insulated Switchgear

Switchgear using air as the main insulation medium between live conductive parts.

VCB — Vacuum Circuit Breaker

A circuit breaker using vacuum interrupters to make and break current.

SLD — Single-Line Diagram

A simplified drawing showing the electrical relationship between sources, busbars, feeders, switching devices, protection and loads.

FAT — Factory Acceptance Test

Agreed inspection and testing performed at the factory before shipment.

Rated Voltage

The voltage class assigned to equipment and used with the specified insulation level.

Rated Current

The continuous current the relevant circuit can carry under specified conditions.

Short-Time Withstand Current

The RMS current the equipment can withstand for a stated short duration.

Peak Withstand Current

The peak current associated with electrodynamic short-circuit stress.

C Unit

Common designation for a cable load-switch or ring-feeder functional unit.

V Unit

Common designation for a vacuum circuit-breaker functional unit.

F Unit

Common designation for a switch-fuse combination functional unit.

PT Unit

Functional unit for voltage transformers, voltage measurement or auxiliary supply.

Compact Substation

A factory-assembled substation combining medium-voltage equipment, transformer and low-voltage distribution in an enclosure.

Qiangchi Engineering Support

Qiangchi manufactures medium-voltage distribution equipment and supports project-specific configuration review, GA drawings, typical SLD coordination, technical clarification, inspection, FAT planning and export packing. Confirmed product options include the QCL-12 RMU, QCL-24 GIS, QCL-40.5 GIS, XGN15 AIS RMU and YB compact substation. Final values and dimensions are project-specific.

Frequently Asked Questions

What should I send for a quotation?

Send the SLD, BOQ, system voltage, rated current, short-circuit level, application, quantity, installation conditions and project specification.

Can Qiangchi propose a configuration?

Yes. A technical proposal can be prepared after review of the project requirements.

Are GA drawings available?

GA drawings are prepared according to the selected product, functional units and approved configuration.

Can FAT be arranged?

The FAT scope and witness requirements can be agreed during technical clarification.

Are all values fixed?

No. Unconfirmed values, dimensions and accessories remain subject to project-specific technical confirmation.

Where can I continue selection?

Use the Product Finder, review Selection Guides, or send the project documents directly.