Cable installations vary in design from one installation to the next. CMP cable cleats have been designed and tested in accordance with IEC 61914 to ensure that regardless of the cable formation there is a suitable cable cleat available for selection.
The advantage of installing three single core cables in such a configuration is that it minimises the induction of eddy currents, therefore reducing the effect of localised heating, whilst maintaining the current carrying capacity
of the circuit.
Trefoil cable cleats are devices used to hold the three single core power cables in a triangular touching (trefoil) formation, along the length of the laid cables.
Short circuit fault conditions of single core cables in trefoil formation result in high dynamic electromagnetic forces; these forces need to be restrained correctly in order to prevent extensive damage to the cable management system, and more importantly potential loss of human life.
PARALLEL / FLAT FORMATION OF SINGLE CORE CABLES
The formation of a number of cables laid in a plane, usually with equal spacing between adjacent cables.
CMP Products manufactures a variety of cable cleats designed to support and restrain cables installed in parallel / flat formation, and manufacture these cable cleats in a number of materials to ensure that the cable cleat is suitable for its intended environment. The CMP Products cable cleats have also been tested for short circuit conditions in parallel / flat formation in accordance with IEC 61914.
The formation of three cables so laid to be mutually equidistant. Viewed in cross-section, the lines joining the cable centres form an equilateral triangle.
CMP Products manufactures several cable cleats designed and tested specifically for cables laid in trefoil formation. This range of cable cleats has been successfully tested and certified in accordance with IEC 61914, and these tests include some of the most extreme short circuit conditions ever tested, and greatest electromechanical forces on the cable ever experienced, by any cable cleat for the relevant cable diameters.
Below image shows (right to left) multicore cable, trefoil formation, parallel / flat formation of single core cables
Cable consisting of multiple conductors, with a common overall covering.
There are currently no standards for the testing of cable cleats during short circuit conditions when used with multicore cable. Nevertheless there is also a need to restrain, keep safe, and preserve the integrity of multicore cables, whether or not they are equipped with some form of mechanical protection or armour. Multicore cables by their very nature have additional layers of insulation and / or fillers as well as an outer jacket or sheath that are intended to keep them intact during their service life. It is a common assumption that the multicore cables which are equipped with armour and an outer jacket or sheath would contain the forces experienced during a short circuit. However, CMP Products continues to test its range of cable cleats on multicore cables during short circuit conditions, for project specific installations.