Georgios C. Christoforidis

Inductive interference on pipelines buried in multilayer soil due to magnetic fields from nearby faulted power lines

The interference of power transmission lines to buried pipelines, sharing the same rights of way, has been a research subject for many years. Especially under fault conditions, large currents and voltages are induced on the pipelines, posing a threat to operating personnel, equipment, and the integrity of the pipeline. The soil structure is an important parameter that affects the level of this interference. In this study, the influence of a soil structure composed of layers with different resistivities, both horizontally and vertically, on the inductive part of this interference is investigated. The method used to determine the inductive interference comprises finite-element calculations and standard circuit analysis. The results show that good knowledge of the soil structure is necessary in order to estimate the above interference with minimum error. Therefore, it is desirable that soil resistivity measurements are made both at adequate depths and at locations far away from the rights-of-way.

A hybrid method for calculating the inductive interference caused by faulted power lines to nearby buried pipelines

The interference of power transmission lines to nearby buried pipelines has been a research subject for many years. Especially during fault conditions, large currents and voltages are induced on the pipelines, which may pose a threat to operating personnel and equipment. In this work, a new hybrid method employing finite element calculations and standard circuit analysis is discussed that may be used in order to calculate the induced voltages and currents on a pipeline running in parallel to a faulted line. Nonparallel exposures are converted to parallel ones and dealt with similarly. The fault is assumed to be a single earth-to-ground one and outside the exposure, so that only inductive interference is considered. A specific case taken from literature is used to validate the proposed method. The results obtained are in good agreement with previously published ones. Important parameters such as the earth resistivity, location of grounding and pipeline coating resistance are evaluated, producing graphs that may be useful to engineers.

Inductive interference calculation on imperfect coated pipelines due to nearby faulted parallel transmission lines

The interference of power transmission lines to nearby pipelines and other metallic structures has been a research subject over the past 20 years. Especially during fault conditions, large currents and voltages are induced on the pipelines. Several methods have been proposed over the years and more recently one utilizing finite element calculations. The last method has the disadvantage that if it considers the pipeline to have a perfect coating, which is rarely the case as defects appear on the coating soon after the pipeline is buried in the ground. In this work a hybrid method employing finite element calculations along with Faraday’s law and standard circuit analysis is discussed. The method is used in order to calculate the induced voltages and currents on a pipeline with defects, running in parallel to a faulted line and remote earth. Non-parallel exposures are converted to parallel ones and dealt with similarly. The defects are modeled as resistances, called leakage resistances. The fault is assumed to be a single earth-ground one and outside the exposure so that conductive interference is negligible. A sample case is analyzed and discussed. The results show that although the pipeline defects act in a way as to reduce the levels of induced voltages and currents, large currents can flow to earth through the defects that may damage the pipeline. # 2003 Elsevier Science B.V. All rights reserved.

Layer recurrent neural network solution for an electromagnetic interference problem

The paper presents an original contribution related to the implementation of a neural network artificial intelligence (AI) technique through Matlab environment, on the study of induced AC voltage in the underground metallic pipeline, due to nearby high voltage grids. The advantage yields in a simplified computation model compared to FEM, and implicitly a lower computational time. In comparison with other neural network solutions identified in the literature, where the induced AC potential is directly evaluated, the authors of this paper propose a new neural network solution to evaluate MVP on the studied domain, using a larger training database for a large panel of different geometries.

Induced voltages and currents on gas pipelines with imperfect coatings due to faults in a nearby transmission line

An improved hybrid method is discussed, employing a finite-element method along with Faradays law and standard circuit analysis, in order to predict the induced voltages and currents on a pipeline with defects on its coating, running parallel to a faulted line and remote earth. Such defects are a frequent situation especially when old pipelines are considered and are modeled as resistances, called leakage resistances. The fault is assumed to be outside the parallel exposure so that conductive interference is negligible and therefore the problem is a two-dimensional one. Input data are power line and pipeline configuration, physical characteristics of conductors and pipeline, fault and power system terminal parameters and location and value of leakage resistances. Simulation results show that for small values of leakage resistances, defects act as a mitigation method for the induced voltages on the pipeline. However, in that case large currents that flow to earth through the defects can damage the pipeline.

Evaluation of induced AC voltages in underground metallic pipeline

Purpose – The purpose of this paper is to make a study of electromagnetic interference between electrical power lines and nearby underground metallic pipelines.Design/methodology/approach – The equivalent electrical circuit of the studied electromagnetic interference problem between electrical power lines and nearby metallic pipelines is created and solved using a loop currents technique based on a hybrid method. The used circuit solving technique was implemented in a software application developed by the authors.Findings – The authors have identified the influence of phase sequence on induced voltage level in an underground pipeline for a double circuit electrical power line. Also the effect of different normal operation and phase to earth fault currents have been revealed.Practical implications – The study has been made through a research project with the Romanian gas transportation company, in order to find the proper protection techniques for underground metallic pipelines.Originality/value – The pape...

Inductive interference of power lines on buried irrigation pipelines

In this paper the inductive interference between power lines and parallel buried irrigation pipelines is investigated, using a hybrid method employing finite element formulation and circuit analysis. A specific configuration taken from the literature is examined during an unbalanced operating condition. This is a common case and may go unnoticed for days, which can result in shocks to persons touching pipeline risers. Also, a general case encountered frequently in the Greek distribution network is studied, producing graphs that may be useful to the engineer. It is found that a detailed knowledge of the overall configuration is needed in order to calculate the inductive coupling with minimum error. Otherwise, computed results are usually on the safe side. Moreover, it is realized that under certain circumstances the current flowing through a person touching a riser may be higher than the acceptable limits.

Electromagnetic interferences between HV power lines and metallic pipelines evaluated with neural network technique

The paper presents the development of a neural network for a study case of an electromagnetic interference between high voltage power lines and metallic underground pipelines, for various constructive geometries. Results gained with neural networks are compared to the finite element solutions considered as standard ones. Our contribution relates to the implementation and test of the neural network technique, to the study of electromagnetic interference in the studied case.