ABSTRACT
Poynting’s theorem can be applied to calculation of active, reactive, and apparent power flowing into the investigated space. The power of electric current flowing through electric line conductors is transported by an electromagnetic field surrounding these conductors. Mathematically, the whole flux of power flowing along conductors can be calculated by the integration of the power flux density, that is, the Poynting vector, through an infinite plane perpendicular to the conductor axes. From the total power flux flowing in surroundings of the conductors and meeting the barrier in the form of impenetrable transformer cover, one can distinguish the components of Poynting vector in particular points of space. In the case of a metallic connection, when the isolation gap does not exist, a short-circuit occurs and then no power flux or current can penetrate through the cover. The total power flow into a transformer exclusively through holes filled by dielectric can be easily checked quantitatively.
