International Journal of Emerging Technology and Advanced Engineering Website: www.ijetae.com (ISSN 2250-2459, Volume 1, Issue 2, December 2011) 152 Analysis of Distribution Transformer Performance under Non-linear Balanced Load Conditions and Its Remedial Measures Sanjay A. Deokar 1 , Laxman M. Waghmare 2 1 Dnyanganga College of Engineering and Research, Pune University, Pune-411041 2 S.G.G.S., Institute of Engineering and Technology, Nanded- 431606 1 s_deokar2@rediffmail.com 2 lmwaghmare@yahoo.com Abstract— In recent years there has been very extensive use of power electronic devices, which result in harmonic proliferation in the power distribution system. In this paper, as per IEEE C 57.110 standards, procedure to calculate total loss in the distribution transformer under non-linear distortion environment is proposed. The power factor capacitor performance under non-linear load conditions is also analyzed. The relation of total current harmonic distortion in the distribution system with load power factor, transformer losses, efficiency and maximum current delivered is also analyzed. The mitigation methods are proposed to minimize the non-linear load impact on the distribution transformer performance. Instead of K-factor transformer approach, a passive harmonic filter method is developed based on higher savings in energy losses. The simulation studies, are performed using Math works MATLAB 7.0.1 for distribution system at 11/0.440 kV, 200 kVA distribution transformer under non-linear balanced load conditions. It is observed that the power factor capacitor bank acts as a source of harmonic under the non- linear load conditions in the presence of passive filters. Keywords— Harmonic Proliferation, k-Factor, Non-linear Load, Power Factor, Mitigation. I. INTRODUCTION The transformers are designed and manufactured to be used for non-linear load, at rated frequency and balanced supply voltage. The present design trend in electrical load devices is to increase energy efficiency with solid-state electronics. One of the major drawbacks of this trend is the injection of harmonics into the power systems. Almost all the utilities have expressed concern about overheating of oil immersed distribution transformers, which supply the non-linear loads. A transformer thermal response to sinusoidal loads is properly evaluated at the transformer design stage, but it’s actual response to non-linear loads should be estimated after proper evaluation of present load conditions[1].The increasing usage of non-linear loads on electrical power systems is causing greater concern for the possible loss of transformer life. Manufacturers of distribution transformers have developed a rating system called K- factor, a design which is capable of withstanding the effects of harmonic load currents. An application of this rating system to specify a transformer for a particular environment requires knowledge of the fundamental & harmonic load currents predicted. In almost all the cases, the field measurements are required to diagnose problems at a specific location, by analyzing load currents. Electrical insulation used in distribution transformers gets degraded when it is subjected to the thermal, electrical, environmental, mechanical and combined stresses during its operation. Electrical stresses are caused by voltage gradient. The average life expectancy of a transformer is decided by the average life of insulating materials. The steady-state power quality problem like harmonics and variation in frequency are responsible for accelerated aging of its insulating material. A transformer designed without considering all these issues will result into premature failure. In [2], a different method to calculate the impact of non-linear loads has been discussed. It also gives an overview of impact of nonlinear load on the distribution transformer winding losses. The standard K-factor transformer ratings and typical loads as well as its design guidelines are given in [3]. In [4], measurement methods for reactive power demand under non-linear loads have been presented. In [5], on line monitoring of all losses of both single and three-phase transformers has been investigated under a different percentage of load conditions.