Cables

Most energy efficiency improvement initiatives focus on end-use equipment, such as motors, and distribution equipment, such as transformers, losses in cables are frequently overlooked. Installation standards are based on two conditions: that the working temperature of the conductor should not exceed the maximum for the insulation – 70 C for PVC, 90 C for XLPE – and that the voltage drop should not exceed 4% (2.5% recommended). Either way, this represents a significant energy loss over the lifetime of the installation.

Increasing the cross-section of conductors reduces these losses, improves power quality, allows headroom for future load growth and improves reliability. The method of determining the lowest lifetime cost – taking full account of energy costs, capital investment and installation costs - is explained in Pub 116. Since the calculations are quite complex, our ‘Energy efficient power cable selection software’ is available to calculate the minimum (BS 7671) conductor size and the size that will yield the lowest lifetime cost.

Publications and Software

To see all Electrical Application publications and software click here.

D10 Energy Efficient Power Cable Selection
This program calculates cable size taking account of type of cable, installation method, circuit length, overload protection, ambient temperature and circuit grouping. Results are presented for the minimum size (i.e. BS 7671) and for each incremental size up to the most economic size. For each size, the overall lifetime cost and the payback period are calculated. The economic calculations take account of load growth, discount rate and increases in energy costs. Cable and installation costs can be modified by the user to suit local conditions. 1998.

Pub 116 Electrical Energy Efficiency
Life time running costs must be taken into account when designing electrical installations or selecting replacement cables, motors and transformers. Both financial appraisal and technical consideration of electrical energy efficiency of motors, cables, busbars and transformers, with actual case histories showing savings to be made can be found in this book. 1997. 80pp.