A novel analytical approach to design a core balance current transformer for earth leakage application

In most earth leakage applications, the detection of a current leakage to the earth is carried out using a current transducer, called a core balance current transformer (CBCT). The phases and neutral conductors pass through a toroidal CBCT. The design procedure of the CBCT is thus a very important aspect in accurately determining an earth leakage. This paper describes an analytical model to design a CBCT for such an application. The algorithm predicts the operating permeability of the core using an iterative method removing the ambiguity brought on by assuming a constant permeability value. A comparison of its effectiveness with a finite element analysis (FEA) and actual test results for a specific material is also compiled.