Abstract: Disclosed herein is a transformer assembly, comprising a toroidal transformer element including a ring and a secondary winding wound around the ring; the ring being arranged to receive a main therethrough to form a primary winding; and a recording medium containing a set of successive incremental factors, each of the factors relating a measurement of a power component for one increment of power flowing through the secondary winding with an expected value of the power component for the increment of power flowing through the secondary winding, both the measurement and the expected value corresponding to a flow of power through the primary winding, wherein the transformer element, together with the set of factors, is capable of generating measurements of power with improved accuracy when corrected by the factors.

Abstract: Disclosed herein is a technique for calibrating a transformer element, comprising the steps of providing a transformer element with a primary winding and a secondary winding; providing a memory to store a range of expected values of a power component, each value being representative of a flow of power expected through the secondary winding for a corresponding flow of power through the primary winding; establishing a flow of power at a first level through the primary winding, thereby to establish a corresponding flow of power through the secondary winding; measuring the power component for the flow of power through the secondary winding to obtain a first measurement thereof; comparing the first measurement with a corresponding expected value and calculating a first factor according to the difference there between; and storing the first factor; varying the flow of power in the primary winding to a second level; measuring the power component for the flow of power through the secondary winding to obtain a second