RMU Tender Checklist: A Practical Specification Template for Utilities and EPCs

RMU Tender Checklist: A Practical Specification Template for Utilities and EPCs

RMU tenders often fail for one simple reason: too many assumptions. Suppliers respond with different insulation levels, cable interfaces, protection scopes, and “standard” options, and evaluation becomes slow and error-prone.

This checklist is a practical template you can paste into your RFQ to make RMU offers comparable and procurement-ready.

A) System Information (Provide This Upfront)

• Network nominal voltage: e.g., 11kV / 24kV / 36kV class.
• Frequency: 50Hz or 60Hz.
• System grounding method: solid, resistance, isolated, compensated.
• Maximum short-circuit level at site: kA and duration (e.g., 20kA/1s).
• Installation: indoor room vs outdoor kiosk; altitude; temperature range; pollution class.

B) Functional Configuration (Single-Line Diagram)

Attach a single-line diagram. Also state the required functional units:

• Ring ways: quantity and whether they are LBS ways.
• Transformer feeder: fused switch or circuit breaker feeder (and quantity).
• Additional feeders: metering feeder, outgoing feeder, bus coupler (if needed).

C) Electrical Ratings

• Rated voltage and insulation level: power frequency withstand and impulse withstand.
• Rated current: busbar and each functional unit.
• Short-time withstand current: with duration.
• Peak withstand current: if required.
• Earthing switch making capacity: if specified by utility standards.

D) Protection and Control Scope

Define which protection approach you need:

• LBS + fuse: specify fuse coordination approach and indication requirements.
• CB + relay: specify relay functions (OC/EF, directional if required), trip circuit, and control voltage.
• CT/VT: ratios, classes, burdens, and mounting arrangement if metering/protection is required.

E) Cable Interfaces and Compartment Requirements

• Cable type and size: conductor cross-section and insulation type.
• Interface standard: separable connectors/bushings, test points, voltage indication.
• Cable entry: bottom/top/side; minimum bending radius constraints.
• Earthing: screen earthing arrangement and earth bar requirements.

F) Safety Requirements

• Interlocks: earthing/access interlocks, key interlocks, padlocking points.
• Internal arc classification: if required by the project.
• IP rating: enclosure and cable compartment requirements.

G) Automation and Monitoring (If Required)

• Motorization: which switches/breakers are motorized.
• FPI: local indication and remote comms requirements.
• SCADA IO list: status, alarms, control commands, and protocol constraints.
• Auxiliary supply: control power voltage, battery/UPS if required.

H) FAT and Documentation

Specify acceptance requirements such as:

• Routine tests: dielectric tests, functional tests, interlock verification.
• Mechanical endurance: if required by the procurement spec.
• Documentation: drawings, wiring diagrams, test reports, operation manuals.
• Spare parts: recommended spares list and quantities.

Internal Links

RMU category page: Ring Main Units.

Related MV panels: Switchgear.

Conclusion

A strong RMU tender is specific about insulation level, fault duty, interfaces, and protection scope. If you provide the system data and the single-line diagram, you will receive more comparable bids and avoid late-stage changes that delay delivery.

Enwei Electric can align RMU configuration options to your tender requirements when the checklist items above are clear and complete.

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