Quick answer
Verify an RMU cable connector against the actual cable, bushing interface, insulation level, screen and earthing method, dimensions, test access and installation procedure. A connector that matches a nominal voltage or conductor size may still fail the mechanical, electrical or space requirements of the offered RMU. Put the connector reference, bushing type, cable construction, termination boundary, accessories and acceptance evidence in the purchase order rather than writing “compatible cable connector” as a generic option.
Start with the bushing and cable interface
Send the supplier the cable data sheet and a marked single-line diagram. Record conductor material and size, insulation, screen or sheath construction, number of cores, phase arrangement, operating voltage, highest voltage for equipment, fault duty, cable entry direction, termination length and any bending or support limits. State whether the cable connector is supplied by the RMU manufacturer, cable contractor or another approved accessory supplier.
| Compatibility item | What to confirm | Evidence to request |
|---|---|---|
| RMU bushing | Interface type, dimensions, contact arrangement and supported accessory family | Bushing drawing, connector list and assembly detail |
| Cable construction | Conductor, insulation, screen, sheath, diameter and core arrangement | Cable data sheet and termination selection record |
| Electrical duty | Voltage, insulation, short-circuit, earthing and test requirements | Approved specification and applicable accessory evidence |
| Mechanical fit | Phase spacing, connector depth, cover, bend radius and support | Compartment drawing with installed connector |
| Earthing and screen | Screen bonding, earth braid, test point and fault indication | Earthing diagram and terminal schedule |
| Installation and test | Sequence, torque, tools, isolation and permitted test interface | Manufacturer procedure and test record |
IEC 60502-4:2023 specifies type-test requirements for accessories for certain medium-voltage extruded-insulation cable systems. It does not pair any connector with any RMU, approve a project installation or replace the equipment manufacturer’s compatibility evidence. See the IEC 60502-4 publication.
Do not compare voltage labels alone
Two connectors can share a voltage class while differing in bushing geometry, screen arrangement, contact size, stress-control components, installation length or test access. Conversely, a cable connector family may support several cable sizes only within a stated range. Ask for the complete connector reference and the exact RMU bushing drawing.
An ABB SafeLink catalogue illustrates a product-specific termination arrangement with a cable bushing, contact hardware, reducer or lug options and stated tightening instructions. The dimensions and torques belong to that product family; they must not be copied into a Jinxing purchase order. Use the ABB SafeLink catalogue as an example of the evidence a buyer should request.
For installation, Schneider Electric’s Ringmaster AirSeT instructions state that MV cable connection follows the cable and equipment procedure and warn against forcing a cable onto a bushing. That is a manufacturer-specific safety instruction, not a universal RMU method. See the Schneider MV cable connection instructions.
Show the installed connector in the compartment drawing
Ask for a drawing that shows the connector, bushing centre, cover, phase spacing, cable bend, support, screen earth and access to the test or voltage-detection interface. Include single and double-cable arrangements when relevant to the project. A connector may fit the bushing but prevent the cover from closing or leave insufficient space for the cable’s minimum bend radius.
Record the force and support path from the cable. The RMU should not carry an unplanned mechanical load from a rigid or badly supported cable. Identify gland plates, cleats, brackets, earthing braid, stress-control parts and sealing items. If the cable termination is supplied loose, list storage, installation and test responsibility separately.
The existing RMU cable compartment checklist covers the broader compartment layout. The RMU cable test and earthing guide focuses on permitted test states, while the switchgear retrofit cable-interface guide covers reuse of existing cables. This article focuses on proving connector-to-bushing compatibility before purchase. Use the Jinxing ring main unit page and project enquiry page to request an itemised interface review.
Include the acceptance and future-change boundary
State what is checked at the factory and what is checked after the cable is installed. The accepted record can include connector identity, bushing reference, installation method, tightening record, screen-earth continuity, phase identification, test access and photographs where required by the project. The applicable tests and values must come from the approved specification and manufacturer instructions.
If the cable supplier, utility or future extension may change the connector, record that as an open interface. A new connector can affect the RMU cover, cable compartment, earthing, test method and outage plan. Do not approve a substitute from a different manufacturer solely because its catalogue lists the same voltage and conductor range.
Example: replacing a cable-fed RMU
Consider a replacement RMU where the existing cable is short and its screen arrangement is not fully documented. The buyer should survey the cable, identify the installed termination, request the offered RMU bushing drawing and compare retermination, cable extension and full cable replacement. The quotation should state the connector, accessories, field work, outage, testing and exclusions. This creates a connection decision that engineering and procurement can both review.
RFQ checklist
- Cable data sheet, conductor, insulation, screen, sheath, size and core arrangement.
- RMU bushing reference, interface drawing, voltage and insulation requirements.
- Connector manufacturer and part number, accessory set and supported cable range.
- Phase spacing, depth, cover, bend radius, support, gland and earthing details.
- Test points, voltage detection, screen bonding and permitted test method.
- Factory-fitted, supplied-loose and field-installed components with owners.
- Installation sequence, tools, tightening record, safety controls and outage.
- Factory, site and cable-termination tests with accepted handover evidence.
FAQ
Is a cable connector compatible when its voltage rating matches the RMU?
No. Bushing geometry, cable construction, screen, dimensions, stress control, earthing, installation method and test access must also be confirmed.
Can the cable contractor choose a connector after the RMU is ordered?
Only when the RMU manufacturer and project engineer approve the exact connector and interface. The purchase order should keep the connector reference and responsibility visible.
Does IEC 60502-4 certify the connector-to-RMU combination?
No. It sets type-test requirements for certain cable accessories. Compatibility with a particular RMU bushing and project installation still requires the applicable manufacturer and engineering evidence.