Probabilistic Assessment of Lightning Related Risk of Transmission Lines Based on Frequency Dependent Modeling of Tower-Footing Grounding System

This paper presents a probabilistic evaluation, based on Monte-Carlo method, for the estimation of insulation risk of failure of overhead transmission lines (TLs). The proposed method takes into account the wide-band model of tower-footing grounding system. The wide-band model of grounding system in frequency domain is obtained by the method of moment solution to the governing electrical field integral equations. The electrical parameters of soil are considered to be either constant or frequency dependent. The time-domain representation of the grounding system is inferred through pole-zero characterization of its associated frequency response. The case of a typical 400-kV transmission line is modelled in EMTP_RV with the tower-footing grounding system integrated with the transmission line (TL) system. The results of the paper show that the failure risk of transmission lines is affected by the grounding system model. This effect is more pronounced when the soil electrical parameters are assumed to be frequency dependent

Locating lightning strikes and flashovers along overhead power transmission lines using electromagnetic time reversal

The paper presents a method to identify the location of direct lightning strikes to overhead transmission lines and potential subsequent flashover(s). The method is based on the electromagnetic time reversal theory and relies on the use of a single measurement point to record voltage transient signals originated by a direct lightning strike either on the phase conductors or shielding wires, and possible flashovers. The measurement system is supposed to be installed on the secondary winding of the transformer located at the line feeding substation. The performance of the proposed method, applicable for different power network topologies, is validated by using different numerical simulations applied to various case studies. The paper also discusses the impact of the grounding system model, high-frequency transformer model, presence of surge arresters as well as soil electrical parameters

Impact of Grounding Systems Frequency Dependency on Lightning Arresters Transient Response

The paper presents a frequency-domain method for the analysis of lightning surge response of overhead transmission lines equipped with surge arresters. The model takes into account the frequency dependence of the grounding system. The transmission line is represented in frequency domain by making use of the BLT (Baum- Liu-Tesche) equations while the grounding system, to which the arrester station is connected, is simulated using general electromagnetic model solved by means of the Method of Moment (MoM) in frequency domain. The lightning-originated overvoltages in presence of the surge arrester are then calculated in frequency domain using the Arithmetic Operator Method (AOM). The validity of the proposed approach is tested by comparing its results with those obtained using the Electromagnetic Transient Program (EMTP), for a simple configuration. The efficiency of the proposed technique is demonstrated considering the case of a more complex grounding system

Analysis of Transmission Lines With Arrester Termination, Considering the Frequency-Dependence of Grounding Systems

The paper proposes a modeling technique to analyze the response of a transmission line terminated by a lightning arrester connected to a grounding system buried in a lossy ground. In this technique, the transmission line ismodeled in the frequency domain with the aid of Baum\u2013Liu\u2013Tesche equations, while the grounding system to which the arrester is connected is treated using a general electromagnetic approach. The electromagnetic approach is based on the solutions to Maxwell\u2019s equations obtained by using themethod ofmoment in the frequency domain. The arrester nonlinearity is included in the frequency-domain analysis using the arithmetic operator method. To examine the performance of the proposed modeling technique, numerical results are presented for a single-conductor transmission line connected to a typical lightning arrester. The results are first compared for a simple grounding configuration of a vertical rod with those obtained using the wellknown electromagnetic transient program, showing the validity of the proposed technique. The generality of the technique is then demonstrated by studying the results of a more complex case of a typical grounding grid. It is shown that the early time responses of the lightning overvoltages are affected by the harmonic impedance of the grounding system

A Full Wave Analysis of Lightning-Induced Voltages on Distribution Lines Considering the Conductive Coupling between the Lightning Channel and the Grounding System

Two approaches for the numerical solution of the full-wave Maxwell’s equations, based upon the finite element method and the method of moments, are here used for the computation of lightning induced voltages on overhead distribution power lines. The methods are well suited to consider both induced and conductive coupling mechanisms between the lightning return stroke channel, the overhead line conductors and the grounding system of the line. It is noted that this last effect is traditionally disregarded in the computation of lightning induced overvoltages. It is shown that the conductive coupling might result in the reduction of the lightning overvoltages induced on overhead lines. This finding justifies the inclusion of the conductive coupling in the available approximate formulae used for the calculation of lightning induced overvoltages