Current Instrument Transformer Error Calculations

A nonlinear differential equation describing the steady-state operation of a current instrument transformer is formulated based upon a Rayleigh hysteresis loop approximation of the magnetic core effects. Using a harmonic-balance technique, a suitable approximate solution of this equation provides expressions for the RCF (ratio correction factor) and phase angle errors for the transformer directly in terms of the magnetic properties of the core material and the transformer instrument burden.