Electromagnetic influence of electric railway system on metallic structures

U radu je istražen elektromagnetski utjecaj sustava električne željeznice na metalne strukture s naglaskom na željeznički sustav kao izvor utjecaja. Opisan je ustroj sustava napajanja električne željeznice i načini prenošenja poremećaja na osjetljive sustave s posebnim naglaskom na magnetsku spregu. Predložena je metodologija točnijeg određivanja elektromagnetskih utjecaja elektrovučne mreže i postrojenja na metalne strukture. Uvažene su karakteristike različitih konfiguracija sustava napajanja i međusobnog odnosa izvora smetnje i osjetljivih elemenata na kojima se promatrao iznos utjecaja. Identificirani su parametri o kojima ovise elektromagnetski utjecaji poput različitih pogona elektrovučnog sustava, izvedaba kontaktne mreže, povratnog puta struje, svojstava tla i izvedaba osjetljive strukture. Pojedinačno je utvrđen značaj svakog od parametra te doneseni zaključci o mjerama kojima se postiže smanjenje utjecaja. Razvijen je model za proračun induciranih napona za karakteristične konfiguracije elektrificirane željeznice te su rezultati proračuna verificirani. Model je verificiran temeljem obavljenih mjerenja induciranog napona te je ustanovljeno dobro podudaranje izračunatih i izmjerenih vrijednosti. Inducirani napon kvalitativno je analiziran za različita elektrovučna vozila ovisno o struji napajanja i struji rekuperacije. Prikazan je model lokomotive s diodnim ispravljačem i istosmjernim motorom te elektromotornog vlaka s asinkronim motorom. Uz različite modele sprege određen je oblik induciranog napona za ove tipove vučnih vozila. Uspoređeni su rezultati proračuna modelom i mjerenja struje napajanja u elektrovučnim podstanicama. Radom je opisan cjelovit pristup problematici određivanja elektromagnetskih utjecaja sustava električne vuče na metalne strukture, razvijen i provjeren model određivanja tih utjecaja te predložene mjere za smanjenje utjecaja.The dissertation is the result of research in the field of electromagnetic compatibility. The influence of AC electric railway system to the metallic structures is studied. Common operation of the electric railway system and the sensitive metallic structures as a telecommunication lines and pipelines in the narrow corridors represents a potential risk to their safe and reliable operation. Electromagnetic effects of the electric railways are primarily manifested as an inductive coupling due to electric current flow through contact line. In accordance with the conditions of the electric railway system operation, power supply system causes the induction on the metallic structures in the common corridor. The induced voltage is directly proportional to the supply current value, but also depends on a numerous of other technical and geographical parameters. The aim of the thesis is to identify and quantify the variable parameters which affects to the value of the inductive coupling, and consequently the value of the induced voltage on sensitive structures. Geographic parameters are related to soil properties and environmental conditions and it is necessary to be thoroughly familiar with them. Technical parameters describe the construction of the railway power system, as well as additional elements which ensure the reduction of electromagnetic influences. In the doctoral thesis electric railway system is expounded on the components. The model of railway system includes the models of different elements whose parameters have an impact on the value of electromagnetic interference. Parametric analyses of certain technical parameters to the influence and induced voltage are performed. The value of the influence and operation conditions requested to ensure reliable and safe operation of a common interaction of electric railways and sensitive metal structures are determined and revised. The dissertation consists of seven chapters. It begins with an introduction in which the problem of electromagnetic influences and motivation to research are clearly and transparently describes. The basic elements of the electric railway are briefly described. Assumptions for the development of the models are carried out and recent research are presented. In the second chapter detailed structure of the electric railway system is presented. All elements for power supply in the electric railway system at the 25 kV, 50 Hz are described. Geometric and electrical parameters of electric traction transformers, contact network, rails and return wire are given. Elements of electric traction vehicles and locomotives electric models with a diode rectifier and DC motor and with an induction motor are described in details. Current supply value and waveform for certain electric traction vehicle are determined and analysed. The third chapter is devoted to the analysis of the modes of disturbance transmission to the sensitive metallic structures. The problematic of inductive coupling and theoretical description of the problem of protection from adverse influences are presented. The impact of the individual structure elements to inductive coupling is analysed. Technical systems commonly exposed to adverse influences of electric railway are described and modelled. The fourth chapter is devoted to determining the electromagnetic influence. The procedure to determine the induced voltage is given. A model for determining the electromagnetic influence based on the theory of electrical circuits is developed and presented. The return current value in the rails and return wire for typical configuration is calculated depending on the variable parameters as a soil specific resistance, rail admittance and different parameters of return and protection wire. For each of the models the influence is determined and the effects of certain parameters to induced voltage are detected. The results of the calculation by the developed models is compared with values calculated using the applicable standards. It is concluded that the developed model provides a more complete view to the electromagnetic impact compared with standards in use. Verification of the model is described in the fifth chapter. Two case studies of single track railway without a return conductor is presented. Based on the supply current measurements and induced voltage on telecommunication lines have been compared with the values obtained by model. It can be concluded that the calculation by model gives more accurate results. It is demonstrated that the electric railway is a dominant source of electromagnetic influences and the developed model describes modelled systems and the interface between them in a suitable manner. Qualitative analysis of the measured results and calculations is made in the sixth chapter. Calculation results of induced voltage by the various models of transmission lines and sensitive metallic structures are compared. It can be concluded that the different approaches of the induced voltage calculation are necessary depending on the type and the operation mode of electric traction vehicles. The harmonic analysis of the induced voltage is calculated. In addition, the effects of railway recovery current on the metal structure are analysed. The importance of the induced voltage calculation by real waveform of supply current is demonstrated regarding the different coupling of each harmonic. The research summarization is given in the seventh chapter of the thesis with accent to the scientific contributions that are achieved