An electric shock impedance modeling method of living organisms in low-voltage distribution network

In order to solve the refusing action and maloperation problem of electric shock of living organisms of Residual Current operated protective Device (RCD) in low voltage distribution network, an electric shock impedance modeling method is proposed in this paper. Trough building up the experiment test bed of electric shock of living organisms, electric shock voltage and current data are collected. After filtering the original electric shock signal, the electric shock voltage and current signal are transformed from time domain to frequency domain by using Fast Fourier Transform. Electric shock voltage and current power frequency component can be extracted. The total electric impedance amplitude and phase values of the living organisms are from Ohm law. Based on the group of 30 electric shock impedance values, using data fitting method to calculate the value of the living organisms electric impedance amplitude and phase. Then, the digital simulation model is set up by using Simulink of MATLAB. Through validating of the impedance modeling, the results show that the model can reproduce the transient process of electric shock organism well. Experiments and results show that the proposed modeling method can improve the operation of RCD with better accuracy and reliability.

I. Introduction

Residual Current operated protective Device (RCD) is an important measure to prevent the leakage of power grid and the electric shock of the living organisms, RCD is widely used in the low voltage power grid [1]. In terms of the action characteristic, most of the operating RCD are unable to identify organisms shock branch drain current signal. Under certain conditions, the electric shock of living organisms or equipment fault leakage will not necessarily increase the residual current, which will lead to the decrease of residual current, which may result in the failure of the RCD.