Measuring temperature rise at transformer core under nonlinear loading

The life of power distribution transformers has been greatly reduced by the significantly addition of electronic loads in the distribution system. The characteristics of loads now becoming more nonlinear which in turn produce more harmonics. Power transformers are constantly affected due to its location between the variety of loads at consumer´s side and the power supply side. Additional loss at transformer core caused by harmonics is translated by the increasing heating it experienced. This paper focuses on measuring temperature of the core as transformer is connected with nonlinear loads. A circuit producing harmonic rich load current is subjected to 75VA power transformer. Tests are conducted at 100% of nameplate rating using purely resistive loads and by connecting nonlinear loads. Differences in type of loads are made in order to magnify the additional heat effect of harmonics in power transformer operation. Laser radiating thermal device is used to measure heat at three different points.