Effective utilization of cables and transformers using passive filters for non-linear loads Shady H.E. Abdel Aleem a , Murat Erhan Balci b,⇑ , Selcuk Sakar c a Dept. of Mathematical, Physical & Life Sciences, 15th of May Higher Institute of Engineering, Cairo, Egypt b Dept. of Electrical and Electronics Engineering, Balikesir University, Cagis Campus, Balikesir, Turkey c Department of Electrical and Electronics Engineering, Gediz University – Izmir, Seyrek/Menemen, Izmir, Turkey article info Article history: Received 22 February 2014 Received in revised form 2 February 2015 Accepted 20 February 2015 Keywords: Harmonic distortion Non-sinusoidal conditions C-type filters Optimal design Cable derating Transformer derating abstract In the literature, it is well known that transformers and cables have excessive losses or overheating under non-sinusoidal current conditions. Accordingly, they have reduced current carrying capabilities (or loading capabilities) for that kind of conditions. This paper aims to employ passive filters for the effective utilization of the cables and transformers in the non-sinusoidal systems. Consequently, an optimal pas- sive filter design approach is provided to maximize the power factor expression, which takes into account frequency-dependent line losses, under non-sinusoidal background voltage and line current conditions. The individual and total harmonic distortion limits placed in IEEE standard 519 are taken into account as constraints for the proposed approach. Besides, keeping the load’s displacement power factor at an adequate range is desired by the proposed approach. The proposed approach and the traditional optimal passive filter design approach, which aims to maximize the classical power factor expression, are comparatively evaluated for an industrial power system with a group of linear and non-linear loads, overhead transmission lines, cables and a transformer. Numerical results show that the proposed one has a considerable advantage in the improvement of the total supply line loss and the transformer’s loading capability under non-sinusoidal conditions when compared to the traditional one. On the other hand, for the simulated system cases, both approaches lead to almost the same current carrying capability value of the cables. Ó 2015 Elsevier Ltd. All rights reserved. Introduction Power electronic devices such as adjustable speed drives, power rectifiers and inverters, are widely employed to control large power electrical loads in present day’s power systems [1]. The loads controlled via power electronic devices, generally called as non-linear loads, draw non-sinusoidal or harmonically contami- nated currents from the utility. Since non-sinusoidal currents cause non-sinusoidal voltage drops on the lines, these loads also result in distorted point of common coupling (PCC) voltages. Accordingly, in the literature, great interests have been focused on the adverse effects of the harmonics on the power distribution equipment such as cables [2–7] and transformers [8–13]. It is seen from these studies that due to the fact that the resistances of the cables and the transformer windings increase with the frequency, they have excessive losses even if the root-mean-square (rms) value of the harmonically distorted load currents are lower than their sinusoidal rated currents. Therefore, current harmonics cause the reduction of their useful life [14]. To prevent cables and trans- formers from these adverse effects of the harmonics, they should be derated under non-sinusoidal current conditions [6,13]. The needed derating factor (maximum permissible current carrying or loading capability) can be calculated as the ratio between the non-sinusoidal load current’s rms value, which leads to the rated loss of the equipment (transformer or cable), and the equipment’s rated sinusoidal current. Power factor is conventionally used as an indicator of how effectively are utilized the power transmission and distribution equipment in the power systems [15,16]. Accordingly, passive filters are widely designed to maximize the classical power factor expression in the literature [17–20]. However, it can clearly be seen from [21] that maximization of classical power factor definition, which is calculated as the ratio between active and classic apparent power, does not achieve the minimum loss case of a power system having transmission and distribution lines with frequency-dependent resistances. http://dx.doi.org/10.1016/j.ijepes.2015.02.036 0142-0615/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +90 2666121194; fax: +90 2666121257. E-mail address: mbalci@balikesir.edu.tr (M.E. Balci). Electrical Power and Energy Systems 71 (2015) 344–350 Contents lists available at ScienceDirect Electrical Power and Energy Systems journal homepage: www.elsevier.com/locate/ijepes