Bushing-Type Current Transformers for High-Accuracy Revenue-Metering Equipment [includes discussion]

Abstract

in the same structure. The coupling of primary and secondary circuits is through air; there is no saturable material involved.The story told by Fig. 10 of the paper can be told more completely by the equation:W=watts loss in the housing, per unit length K = a constant determinable for a given geometry of design (like a circular cylindrical housing) I=current in main bus D =diameter of circular bousing A =phase-to-phase distance This equation has been found by test to be applicable over a very wide range of variation of both D and A. The value of K is much higher for the center phase than for the outside phases and is approximately (but strictly not exactly) the same for both outside phases. The equation is given in its simplest form. Completely expressed, it takes care of different housing materials (resistivities) and thicknesses.