Extensive application of power electronics and other nonlinear components and loads creates single-time (e.g., spikes) and periodic (e.g., harmonics) events that could lead to serious problems within power system networks and its components (e.g., transformers). Some possible impacts of poor power quality on power transformers are 9 saturating transformer core by changing its operating point on the nonlinear ~-i curve, 9 increasing core (hysteresis and eddy current) losses and possible transformer failure due to unexpected high losses associated with hot spots, 9 increasing (fundamental and harmonic) copper losses, 9 creating half-cycle saturation in the event of even harmonics and DC current, 9 malfunctioning of transformer protective relays, 9 aging and reduction of lifetime, 9 reduction of efficiency, 9 derating of transformers, 9 decrease of the power factor, 9 generation of parallel (harmonic) resonances and ferroresonance conditions, and 9 deterioration of transformers' insulation near the terminals due to high voltage stress caused by lightning and pulse-width-modulated (PWM) converters.Pfe = Phys + Peddy = ghys (Bmax)Sf + geddy(Bmax)2f 2, (2-1) where Phys, Peddy, Bmax, and f are hysteresis losses, eddy-current losses, maximum value of flux density, and fundamental frequency, respectively. Khys is a constant for the grade of iron employed and Keddy is the eddy-current constant for the conductive material. S is the Steinmetz exponent ranging from 1.5 to 2.5 depending on the operating point of transformer core.9 Elsevier Inc. All rights reserved. I ~,H I i r 9 FIGURE 2.4 Magnetic field strength inside and outside of a conductor. / / I i \ % o 9 "% ~Ho3 / %% u / / %