Economic optimisation of electric conductors in commercial and public buildings using methodology proposed by IEC 287-3-2

Panel: Panel 2. Comfort and energy use in buildings

Authors:
Carlos G. Tanides, School of engineering, University of Buenos Aires & Instituto Argentino de Normalización (IRAM)
María J. Cánepa, School of engineering, University of Buenos Aires & Instituto Argentino de Normalización (IRAM)
Osvaldo D. Petroni, School of engineering, University of Buenos Aires & Instituto Argentino de Normalización (IRAM)
Juliana Rizzone, School of engineering, University of Buenos Aires & Instituto Argentino de Normalización (IRAM)
Héctor L. Soibelzon, School of engineering, University of Buenos Aires & Instituto Argentino de Normalización (IRAM)

Abstract

The main goal of this work is to study the impact of optimising the size of electric conductors within commercial and public buildings in order to minimise electric losses and, at the same time, to reduce electric billing. Norm IEC 287-3-2 establishes a methodology for doing so by considering total cost of installing and operating a cable during its economic life. As a consequence, the electric conductor selected, generally, results with a larger cross-sectional area. In this analysis for the computation of total costs it was considered the influence of taking into account the voltage drop and the replacement of electrical overcurrent protections, when necessary, due to the increased short-circuit current resulting from the diminished circuit impedance for larger cables.

Finally, the methodology was specifically applied to the Paseo Colón building of the School of Engineering of the University of Buenos Aires, analysing a representative sample of 78 electric sectional switchboards where there were measured the electrical load curves and calculated the specific loss load factor of each sector. From the study it was determined the convenience of selecting the cable size resulting from the method proposed by IEC. The total costs savings between “conventional” and “efficient” conductors considering the whole building is around 40%, with a maximum of 55% in the best case, and considering overall energy utilisation of the building, reductions obtained are of 4.9% of the electric power demand and 1.1% on energy consumption.