How to Read an RMU Single-Line Diagram (SLD)

Direct answer: An RMU SLD shows how incoming feeders, outgoing feeders, transformer protection, busbars, earthing switches, metering and protection devices are electrically connected. Read it from the power source through each functional unit to the protected load.

Key Points

• Identify source, busbar and power-flow direction
• Mark each incoming, outgoing and transformer feeder
• Read device symbols for load switch, circuit breaker, fuse and earthing switch
• Check CT, VT/PT, relay, metering and remote-control requirements
• Confirm normal-open points and interlocking logic

Selection Guidance

A typical ring arrangement may use two cable switch units and one transformer protection unit, but the correct configuration is project-specific. The SLD must also match cable entry, rated current, short-circuit level and protection philosophy.

Information Required for Engineering Review

Provide the nominal voltage, highest system voltage, rated current, short-circuit level and duration, frequency, application, SLD, BOQ, protection requirements, cable details, installation conditions and quantity. Qiangchi will confirm the project-specific configuration and document requirements.

Engineering Documents and FAT

Available project support may include configuration review, technical clarification, GA drawing, typical SLD coordination, component schedule, routine-test documentation, FAT planning and export packing. Final scope is confirmed according to the approved specification.

Frequently Asked Questions

Can the final selection be made from the voltage and current alone?

No. The SLD, fault level, functional units, protection, cables and service conditions must also be reviewed.

Are all configurations the same size?

No. Dimensions depend on voltage class, functional units, cable arrangement and optional devices. Use the approved GA drawing.

Can Qiangchi review an EPC specification?

Yes. Send the SLD, BOQ and specification for a project-specific technical review.

What is checked during FAT?

The FAT scope may include visual and mechanical checks, wiring verification, interlock checks, functional tests and routine electrical tests according to the agreed inspection plan.

Which standards apply?

The applicable IEC or project standard is confirmed during technical clarification. Project-specific requirements must be stated before design approval.

Where can I compare related products?

Review typical SLD resources, GA drawings or use the Medium Voltage Product Finder.