MV Cable Termination for Switchgear: Key Design and Specification Considerations
Medium-voltage switchgear specifications often focus on rated voltage, continuous current, short-circuit capacity and protection systems. However, one critical interface can create significant installation problems when overlooked: MV cable termination.
The connection between incoming or outgoing medium-voltage cables and switchgear must accommodate the cable dimensions, termination accessories, electrical clearances, earthing arrangement and physical installation requirements.
A switchgear panel may fully comply with its electrical ratings but still be unsuitable for the cables specified by the EPC contractor.
This problem often becomes apparent only when equipment arrives on site and cable installation begins.
For industrial, utility, mining and renewable energy projects, medium voltage cable termination requirements should therefore be confirmed before switchgear manufacturing starts.
This guide explains the key engineering considerations that help avoid installation delays, equipment modifications and unexpected procurement costs.
Why Cable Termination Design Matters in MV Switchgear
Cable termination provides the electrical and mechanical connection between the power cable and the switchgear.
It must maintain appropriate insulation performance, electrical contact, mechanical stability and safe operation under normal and fault conditions.
The termination arrangement also needs to accommodate cable handling, future maintenance and testing requirements.
Depending on the switchgear design, cables may connect through conventional terminations, screened separable connectors or other manufacturer-approved interfaces.
The correct solution depends on the system voltage, cable construction, switchgear architecture and installation conditions.
Leistung Energie's medium voltage switchgear specification checklist highlights cable termination space, cable entry and cable trench requirements as important considerations during equipment selection.
For EPC contractors, the key principle is straightforward: cable compatibility should be verified during engineering, not left to installation teams.
Confirm Cable Size and Conductor Configuration Early
One of the first requirements in any switchgear cable termination design is confirming the cable specification.
Engineers should identify the conductor material, cross-sectional area, insulation system, cable diameter and construction.
Common MV cable conductors include copper and aluminium, while cross-sectional areas vary according to circuit capacity and installation conditions.
Cable Conductor Size Affects More Than Current Capacity
Larger conductors may be required for high-current feeders, long cable routes or specific voltage-drop requirements.
However, increasing conductor size also affects termination dimensions and installation flexibility.
Larger cables may require:
Larger termination accessories
Additional cable support
Greater bending space
Larger cable compartments
Different connection hardware
The outer cable diameter is particularly important because two cables with similar conductor sizes may have different overall dimensions due to insulation, screens, armour and sheath construction.
Cable specifications should therefore include actual dimensional data rather than conductor size alone.
Number of Cables Per Phase
High-capacity feeders may require multiple parallel cables per phase.
For example, a transformer incomer may use two or more single-core cables per phase to achieve the required current capacity.
This creates additional space requirements inside the MV switchgear cable compartment.
The design must accommodate cable spacing, termination positions, conductor connections and mechanical support.
Engineers should also confirm current sharing, cable grouping and thermal performance under the proposed arrangement.
A compartment suitable for one cable per phase cannot automatically be assumed to accommodate multiple parallel cables.
Top or Bottom Cable Entry: Which Is More Suitable?
Cable entry direction is an important mechanical interface between switchgear and civil works.
Many substations use bottom cable entry through a cable trench or basement.
However, top entry may be required for overhead cable routing, existing installations or specific switchroom arrangements.
Bottom Cable Entry
Bottom entry is common in industrial and utility switchrooms where cables approach from underground trenches.
The design must coordinate the switchgear floor opening, gland plate, cable trench and cable bending arrangement.
Insufficient trench depth can make it difficult to route large cables into their final termination positions.
Top Cable Entry
Top entry can be useful where floor access is restricted or cables are routed through overhead containment systems.
However, it requires careful consideration of ceiling height, cable support, entry sealing and switchgear construction.
Top entry should only be specified where the manufacturer provides an approved arrangement.
For both configurations, engineers must confirm compatibility with enclosure protection, internal arc performance and the switchgear's tested construction.
Separable Connectors vs Conventional Cable Terminations
The choice of termination technology depends heavily on the switchgear architecture.
Air-insulated switchgear commonly uses conventional cable terminations where the insulated cable cores connect to terminals within the cable compartment.
Compact gas-insulated or solid-insulated equipment may use screened separable connectors designed to mate with specific bushings.
Conventional Cable Terminations
Conventional terminations may use heat-shrink, cold-shrink or other approved insulation and stress-control technologies.
These arrangements generally require adequate space around each cable termination to maintain electrical clearances.
They also need suitable access for installation and inspection.
Screened Separable Connectors
Separable connectors provide a defined insulated interface between cables and compatible switchgear bushings.
They can be particularly useful in compact installations where exposed live connections are undesirable.
However, compatibility must be verified.
The connector and bushing must have matching electrical ratings, mechanical interfaces and manufacturer-approved configurations.
For 33kV cable termination, the appropriate cable accessory voltage class and insulation requirements must also be confirmed against the system's highest operating voltage.
Neither termination method should be selected solely because it appears more compact.
The decision should consider maintainability, installation capability, electrical performance and equipment compatibility.
Minimum Bending Radius Can Determine the Switchgear Layout
The minimum bending radius is one of the most frequently overlooked aspects of MV cable installation.
Power cables cannot be bent indefinitely without risking damage to insulation, screens or other cable components.
The required bending radius depends on cable construction and the manufacturer's installation instructions.
Large single-core cables may need substantial space between the point of entry and the termination position.
This becomes particularly important when cables enter from below and must change direction inside a relatively narrow compartment.
Engineers should coordinate:
Cable entry position
Minimum bending radius
Termination height
Available trench depth
Cable support locations
Installation access
The cable route should be checked using actual cable dimensions and the switchgear manufacturer's drawings.
A general arrangement drawing that shows sufficient cabinet height does not necessarily demonstrate that the cables can be installed correctly.
Cable Compartment Dimensions and Installation Clearance
The MV switchgear cable compartment should be evaluated as a practical installation space rather than simply an enclosure dimension.
Engineers should confirm the usable internal width, depth and height after allowing for internal equipment.
This may include current transformers, cable supports, busbar connections, surge arresters, earthing components and barriers.
Allow Space for Installation and Maintenance
Cable installers need sufficient access to prepare conductors, install stress-control components, position connectors and complete the required electrical connections.
Limited working space can increase installation time and create workmanship risks.
The specification should therefore identify whether cable termination access is required from the front, rear or both sides.
The switchroom layout must also provide the necessary operating and maintenance clearance.
These considerations are particularly important in prefabricated e-houses and containerised substations where the available footprint is limited.
Earthing and Cable Screen Arrangements
Correct earthing is essential for safe and reliable MV cable connection.
MV cable screens provide a path for capacitive and fault-related currents, depending on the cable design and earthing arrangement.
The project must establish the appropriate screen bonding method.
This may involve single-point bonding, both-end bonding or another engineered arrangement depending on cable length, induced voltages, fault duty and system design.
The switchgear specification should identify the required screen earthing connections and associated hardware.
Cable gland plates and metallic support arrangements should also be coordinated to avoid unintended heating or circulating-current problems, particularly with single-core cables.
These details should be reviewed together with the project earthing study rather than determined independently during installation.
CT Arrangement and Protection System Interfaces
Cable terminations may share space with current transformers and other protection equipment.
Depending on the switchgear design, CTs may be installed around conductors, cables or dedicated primary connections.
Earth-fault protection may also require a core-balance current transformer.
The physical position of these devices can affect cable routing and screen earthing.
For example, the routing of cable screen earth conductors through or around a core-balance CT may influence the measured residual current.
The arrangement must follow the approved protection design and equipment manufacturer's instructions.
Proper coordination between the cable supplier, switchgear manufacturer and protection engineer is essential.
Testing Access Should Be Considered Before Procurement
Cable testing is another important interface that can be overlooked during switchgear specification.
Following installation, medium-voltage cable circuits may require electrical testing in accordance with the project commissioning procedure and applicable standards.
The design should allow safe access for approved testing methods without unnecessary dismantling.
Testing arrangements may need to accommodate cable isolation, earthing, test connections and the protection of sensitive equipment.
For switchgear using separable connectors, the manufacturer should confirm the permitted cable testing procedure and any required test accessories.
Cable testing should not be performed through connected equipment unless the procedure and equipment ratings explicitly permit it.
What to Include in an MV Cable Termination Specification
Before issuing a switchgear purchase order, engineers should confirm the following information.
Specification Area | What Engineers Should Define |
System voltage | Nominal and highest system voltage |
Cable conductor | Copper or aluminium |
Cable size | Conductor cross-sectional area |
Cable construction | Insulation, screen, armour and sheath |
Cable quantity | Number of cables per phase |
Cable entry | Top or bottom entry |
Termination type | Conventional or separable connector |
Bending radius | Manufacturer's minimum requirement |
Cable compartment | Usable dimensions and termination space |
CT arrangement | Position and cable routing |
Earthing | Screen bonding and earthing connections |
Surge arresters | Requirement and installation location |
Testing access | Isolation and test connection arrangements |
Documentation | Cable interface and installation drawings |
This information should be submitted with the project's single-line diagram and cable schedule.
For renewable energy projects, the cable interface becomes particularly important where multiple feeders connect solar inverters, wind turbines or battery storage blocks to the collector substation.
The existing 33kV switchgear design should therefore be reviewed against the complete collector cable arrangement.
Cable Termination Requirements Before Factory Acceptance Testing
Factory Acceptance Testing should verify that the supplied switchgear matches the approved cable interface requirements.
Although final cable terminations are often completed on site, FAT can confirm cable compartment construction, termination connection points, CT arrangements, earthing facilities and installation clearances.
Before FAT, engineers should review the approved general arrangement drawings, cable connection diagrams and manufacturer installation instructions.
The documentation should also identify any cable termination accessories supplied separately and any installation work excluded from the switchgear manufacturer's scope.
Resolving these interfaces before delivery reduces the likelihood of unexpected modifications during site installation.
Common MV Cable Termination Mistakes to Avoid
One common mistake is ordering switchgear based only on electrical ratings without confirming cable dimensions.
Another is assuming that a standard cable compartment will accommodate multiple large cables per phase.
Other risks include selecting incompatible separable connectors, overlooking cable bending radius, failing to coordinate CT positions and providing insufficient installation clearance.
Engineers should also consider the relationship between cable compartments and Internal Arc Classification.
Unauthorised modifications to cable compartments, gland plates or pressure-relief arrangements may compromise the intended switchgear design.
The best approach is to resolve cable interfaces before manufacturing drawings are approved.
Conclusion
MV cable termination is a critical interface between medium-voltage switchgear and the wider electrical distribution system.
A successful design requires more than selecting the correct cable size.
Cable quantity, conductor construction, termination technology, bending radius, cable entry, compartment dimensions, earthing, CT arrangements and testing access must all be considered together.
For industrial, utility, mining and renewable energy projects, these requirements should be established before equipment procurement.
A well-defined cable termination specification helps reduce installation delays, improve equipment compatibility and support reliable long-term operation.
The key procurement principle is simple: confirm the cable interface before ordering MV switchgear—not when the equipment arrives on site.
Planning an MV Switchgear Project?
Leistung Energie Australia provides medium voltage switchgear solutions for industrial, utility, mining, renewable energy and power infrastructure applications.
If your project involves large MV cables, multiple cables per phase, compact switchrooms or specialised cable termination requirements, these interfaces should be reviewed early during equipment selection.
Contact Leistung Energie Australia to discuss your MV switchgear specification, cable connection requirements and upcoming electrical infrastructure project.
Comments