Evaluation of Current Transformers Impact on Harmonics Caused by High Impedance Faults

The contact between an energized conductor and a low-conductivity surface can originate High Impedance Faults (HIFs). Current signals measured during HIFs have low amplitude, hindering their detection by traditional protection methods, and are usually nonlinear. Therefore, many HIF Detection Methods (HIFDMs) are based on the signals' harmonics, which have peculiar characteristics during HIFs. However, most existing HIFDMs do not consider the influence of current transformers (CTs) at the interface between the power grid and the relay during the testing stages. In this context, this paper analyzes CT's influence on the amplitude and angle of harmonics extracted from current signals measured during HIFs and on existing HIFDMs. The results demonstrate the influence of CT transformation ratio, overload factor, ratio error, and HIF incidence bus on the analyzed parameters. Thus, this paper has the goal to assist researchers in developing methodologies tested in increasingly realistic situations.