Yes, in electrical installations involving Medium Voltage (MV) cables, it's common and often recommended to provide extra cable loops at both the origin (e.g., substation) and the destination (e.g., transformer).Here's why: Slack for Termination and Maintenance

The extra loop provides slack, making it easier to terminate the cable properly during the initial installation. It also allows for future re-termination if needed, such as for troubleshooting, repairs, or connecting to new equipment.

Stress Relief

MV cables can be rigid and less flexible than low-voltage cables. The loop helps to reduce mechanical stress on the cable termination points due to vibration, thermal expansion/contraction, or slight settling of the surrounding ground or equipment. Without the loop, these stresses could damage the cable termination or the cable itself over time, leading to failures.

Future Modifications/Upgrades

Having extra cable length available can simplify future modifications or upgrades to the electrical system. For example, if a transformer needs to be replaced with a slightly different model, the extra cable can be used to accommodate the new dimensions without requiring a complete cable replacement.

Easier Cable Testing

Loops facilitate testing the integrity of the cable during commissioning and subsequent maintenance.

Fault Accommodation

In the event of a fault close to the termination point, the extra cable allows for a section to be cut back and re-terminated without requiring a complete cable replacement.

How much extra loop?

The amount of extra loop will depend on: Cable Size and Type

Larger cables generally require larger loops.

Installation Conditions

Confined spaces may limit the loop size.

Specific Project Requirements

Design standards or client specifications may dictate the minimum loop length.

Manufacturer Recommendations

Consult the cable manufacturer's recommendations.A common practice is to provide a loop with a diameter large enough to allow for easy handling and bending of the cable without exceeding its minimum bending radius. Typically, this might be several meters (e.g., 3-5 meters or more) of extra cable at each end, formed into a loop or coil. It is common to have a specific amount added that is then coiled on cable racks or trefoil cable cleats to hold the spare length.

Considerations



Space

Ensure adequate space is available to accommodate the cable loops without creating hazards or obstructing access to equipment.

Cable Management

Properly support and secure the cable loops to prevent sagging or damage. Use cable trays, cable racks, or cleats to maintain the loop's shape and position.

Earthing/Grounding

Ensure proper earthing/grounding of the cable sheath and any metallic cable supports within the loop area.

Documentation

Record the location and length of the extra cable loops in the project documentation for future reference.

Bending Radius: Ensure the minimum bending radius of the cable is never exceeded when forming the loop. Exceeding the minimum bending radius can damage the cable insulation.In summary, providing extra cable loops for MV cables is a best practice that improves the reliability, maintainability, and adaptability of electrical installations. It's a relatively small upfront cost that can provide significant long-term benefits. Always refer to relevant standards, codes, and manufacturer's recommendations for specific requirements. Flag for review