Minimum Bending Radius and Installation Temperature

Bending radius

The manufacturer states the minimum bending radius for its XLPE power cable range as a multiple of the cable's own overall diameter:

• Single-core cable — 20 × cable O.D.
• Multi-core cable — 15 × cable O.D.

The radius is measured to the inside of the bend, and it applies to the finished cable diameter rather than to the conductor size. Bending below this limit overstresses the insulation on the outside of the bend and can deform the conductor screen on medium-voltage constructions — damage that does not show up on a routine electrical test but reduces the working life of the cable.

Pulling around a bend is more demanding than bending into position: the cable is under tension and sidewall pressure at the same time. Where a route has several bends, the limiting factor is usually the combination, not any single radius.

Temperature limits during installation

Sheath compounds stiffen as they cool, and a stiff sheath cracks when bent or pulled. The manufacturer's data gives a minimum installation temperature of 0 °C and a minimum ambient temperature of -15 °C for both the XLPE and LSOH ranges.

Below the installation limit the practical remedy is to warm the cable before handling — storing the drums in a heated area and pulling during the warmer part of the day — rather than pulling cold and hoping for the best. Sheath cracking from cold-weather installation typically appears as damage at bends and at the point where the cable leaves the drum, and it is not repairable in place.

Magnetic ducts and single-core cables

The application note on the manufacturer's XLPE sheets is explicit: laying single-core cable in magnetic ducts is not allowed.

The reason is induction. Alternating current in a single-core conductor induces a circulating current in any closed magnetic loop around it, and a steel duct is exactly such a loop. The duct heats, losses rise, and the effective current rating of the circuit falls below the value it was designed for. Multi-core cables do not have this problem because the fields of the conductors largely cancel, which is why duct material is a decision that has to be made with the cable construction in mind.

Traction versus mechanical force

The manufacturer describes the standard YJV construction as suitable for laying indoors and outdoors, able to bear a certain traction during installation but not external mechanical forces.

That distinction matters for route selection. A cable can be pulled into position and still be unsuited to a location where it will be struck, crushed or abraded in service. Where the installation exposes the cable to mechanical damage, the correct response is to specify an armoured construction or mechanical protection at the design stage — not to select a heavier unarmoured cable and hope it absorbs the abuse.