A technique for the evaluation of lightning-induced voltages in complex low-voltage power-installation networks

In order to gain knowledge of the effects of lightning-electromagnetic field pulses (LEMP) in low-voltage power installations (LVPIs), the transient response of two electrical networks was measured when they were exposed to lightning electromagnetic fields in the summer of 1998. Both networks were isolated from the energy supply. One network was a simple circuit installed in a room of a single storey wooden residential house and the other consisted of the house´s whole electrical wiring circuit. The main goal of this paper is to develop a practical method with which to estimate the transient response of LVPIs to LEMP. The method uses the information contained in a small portion of the time domain waveform of the electric field, which can be approximated as a unit step function and the corresponding induced voltage, which, in turn can be approximated as the unit step response. It is shown how this unit step response can be used in determining the induced overvoltage in the network due to any complex electric-field waveform. Advantages, limitations and considerations associated with the application of this method are also discussed