Unperturbed Electric Field and Operator Current Towards Ground in HV Substations: a linear relationship between two measurements

As a part of the monitoring of the electric field (E-field) generated in HV substations, a proportionality was observed between the unperturbed E-field and the electric current flowing towards ground from the body of an operator equipped with insulating footwear, measured by an ammeter, in different substation locations. This proportionality cannot be assumed a priori, as the human body capacitive coupling with the HV and surround conductors in the complex substation layout can strongly vary, depending on the measurement point. In the paper, the validity of the proposed indirect approach is validated and quantified, considering an operator moving inside an HV substation. The rationale is discussed by a specific FEM analysis including an anthropomorphic body and confirmed through experimental validation measurement. The linear dependence between the unperturbed E-field and the current flowing from the operator to ground can help speed up and simplify the human exposure assessment to the E-field through indirect, but still sufficiently accurate measurements.