Grounding Performance under Lightning Surges in High Voltage Substations

Postponed access: the file will be accessible after 2019-05-31To achieve electromagnetic compatibility (EMC) and sufficient protection against lighting transients in the power transmission system, understanding of the grounding system transient behavior becomes crucial when deviating from international design standards and recommendations. To consider design deviations the present work is focused towards developing a method of integrating simplified grounding system models in transmission systems and perform lightning transient analysis on both parts to evaluate a particular design case. Firstly, the grounding system models for substation grounding grids, with a variety of configurations and sizes, is implemented. The characteristic transient response of the grounding system is visualized through simulations to study the sensitivity of configurations and modified soil parameters during current injections. The method of implementation allows for a detailed view and pre-processing of large data-sets from simulations. The advantages of this method is used to extract overall measured values to create a tool for EMC analysis and in addition processing different parameters and functions of the grounding system. Secondly, the grounding system model is integrated into transmission systems using a newly released interfacing application. The application allows for co-simulation between the development software of the grounding system and a specialized tool for the transmission system. The innovation of this modeling approach is given as a contribution to an international conference by submitting a paper. Finally, the integrated grounding models and transmission system are studied with two substation design cases; a short and long cable between surge arrester and transformer. The short cable case follows well-known design standards where the long cable case is a design deviation which is common in larger domestic hydropower plants. Even though the long cable case is deviating from design recommendations, the results show a less negative impact on the grounding system compared to the short cable case.Masteroppgave i energiMAMN-ENERGENERGI39

Recent trends in power systems modeling and analysis

In recent years, the explosion of renewable energy sources, the increase in the demand for electrical energy, and several improvements in related technologies have fostered research in many relevant areas of interest

Integration of Frequency Dependent Soil Electrical Properties in Grounding Electrode Circuit Model

The effect of frequency dependent soil properties on the impedance and transient response of the grounding electrode was investigated. The frequency dependent soil models as proposed by Scott, Smith-Longmire, and Visacro-Alipio were critically reviewed. A novel method was proposed to integrate the frequency dependent soil electrical properties in the circuit model of grounding electrode. To validate the application of the method in circuit model, the voltage responses of the grounding electrode obtained by the circuit and electromagnetic models were compared. The voltage responses obtained by the circuit and electromagnetic models were in excellent agreement in terms of voltage peaks and wave shapes. The differences between voltage peaks obtained by the circuit and electromagnetic models were found less than 1%

AC Interference on Gas Pipeline due to Phase to Ground Faults in Overhead Transmission Line

The purpose of this research is to investigate the severity of voltages induced on gas pipeline installed in parallel to a 115 kV overhead transmission line. The overhead transmission line (OHTL) is configured as a single-circuit. One of the phases exposed to single phase to ground fault. Transmission of high voltage along the same right of way (ROW) with metallic conductor may possibly introduce interference on metallic conductors such as gas pipeline (GPL) due to power frequency voltage as well as due to phase faults and switching phenomena. Two main approaches were used to compute the induced voltages, namely the method of moment (MOM), which is based on electromagnetic field theory, and circuit based method. The simulation considers the length of OHTL and GPL are 30 km and 10km respectively. The pipeline buried at 1 m underground in homogenous earth structure with various soil resistivites ranged from 10 to 1000 Ω-m. The transmission line consists of 150 towers and 200 m span length. The separation distance between the GPL and OHTL is varied from 5 to 100 m. The phase to ground fault current changed from 0.5 to 10 kA. Several observation points are made throughout the corridor, to examinant the induced voltages at different locations. The result show that, the soil resistivity, separation distance, and fault current had significant effect on pipeline induced voltage. In case of the observation points lying on the soil or on the outer surface of the pipeline coating, the induced voltage increased, when the soil resistivity increase, as expected. In case of the observation points placed inside the pipeline metal, and the pipeline is well coated, the induced voltage will decreased, when the soil resistivity increase

Simulation and Analysis of High Voltage Engineering in Power Systems

This book address important issues regarding the modelling and simulation tools and techniques that are applied in high-voltage engineering in modern power systems. The presented conceptual, constructive, empirical, experimental, and theoretical results are obtained in the area of high-voltage engineering. Special attention is given to protection methods against direct lightning strikes, partial discharge tests, discharges’ influence on different structures, cable screening, and induced voltages, among others