Filtered Frequency Spectrum Method to Compute the Ground Potential Rise Due to Lightning Strikes

The concerns regarding the Ground Potential Rise (GPR), which is generated by lightning strikes and can result in hazardous voltages in the vicinity of ground electrodes, have driven the development of models for Lightning Protection Systems (LPS) that take into account soil properties. Utilizing an appropriate model that generates approximate results for diverse LPS geometries, a devised direct time-domain assessment of GPR can provide an efficient and fast estimation. This proves particularly valuable in the development of practical resources for LPS projects, encompassing analysis of physical installation aspects and evaluation of (1) risks linked to concealed grid ruptures or disconnections, and (2) potential enhancements through alterations in electrode geometries and positioning. The influence of frequency-dependent soil parameters (FDSP) is crucial and cannot be overlooked when attempting to realistically express GPR, especially for higher soil resistivity. This article introduces an approximate method known as the Filtered Frequency Spectrum Method (FFSM) to efficiently evaluate GPR while considering FDSP. The simulations utilize ATP-EMTP and MATLAB. The lightning current’s frequency spectrum is obtained through Fast Fourier Transform (FFT); the spectrum is then segmented into bands using filters. For each band, a circuital model is constructed using Transmission Line Modeling. The resulting GPR is calculated as the sum of the filtered results.