power systems loss

(From npsc2010.uceou.edu ) The performance of transformer, the most ancient power system static element, is affected due to presence of distortion in the input supply voltage and non-linearity in the load current. Due to extensive use of modern power electronics controlled devices, the degree of non-linearity in the load current has increased in recent years. 

CALCULATION OF TRANSFORMER LOSSES UNDER NON-SINUSOIDAL CURRENTS USING:TWO ANALYTICAL METHODS AND FINITE ELEMENTS ANALYSIS An article discussing effects of non-sinusoidal currents to the transformer losses. This article was made through the effort of M.Yazdani-Asrami, M.Mirzaie and A.Shayegani-Akmal of Babol University of Technology, Babol, Iran. Introduction Transformers are the most important component in power system and are interfaces between consumers and suppliers. Contemporary with ever-increasing electrical energy demand, the number and capacity of installed transmission transformers and especially distribution transformers are increasing. However, considering the point that the efficiency of these components is 97-99%, there was not enough attention to the amount of loss and performance of transformers. By considering the large number of transformers in transmission and distribution networks, it can be seen that the total power loss of these components is high. So, any reduct

TRANSFORMER LOSSES AND THE EFFECT OF HARMONIC CURRENTS ON THESE LOSSES TUTORIAL DISCUSSION (From ANNEX D of IEEE STD C57.110-1998) Power transformers with ratings up to 50 MVA are almost always of core form construction. High-voltage and low-voltage windings are concentric cylinders surrounding a vertical core leg of rectangular or circular cross section. The vertical core legs and the horizontal core yoke members that constitute the magnetic circuit are made up of thin steel laminations. In the top and bottom yoke regions there are usually external clamping structures (clamps) that may be made of either metallic or insulating materials. Oil-immersed transformers are contained within a steel tank, while dry-type transformers may be either freestanding or surrounded by a metal enclosure. If direct current is passed through the transformer winding conductors, a simple I 2R loss will be produced, where R is the dc resistance of the winding. However, if an alternating current (ac) of the

HARMONICS EFFECT TO TRANSFORMER LOSSES How does harmonics contributes to transformer losses? Harmonics or harmonic distortion in electrical definition is a type of disturbance both found in the voltage and current waveform. Most common source of this distortion is primarily associated with non-linear loads like electronic loads. These electronic loads can either be from a single phase or three-phase form. Harmonics is said to be caused by a non-sinusoidal load currents usually are blamed from commercial power supplies and motor drives like personal computers and other electronically driven devices. Harmonic distortions to either voltage or current are also reflective to the other according to the ohm’s law principle. Previously we have discussed that transformer loss are usually categorized as no-load loss (referred sometimes as excitation loss), load loss (also called as impedance loss), and total loss (the sum of no-load loss and load loss). If you try to recall our discussions re