A procedure is presented for analyzing train voltages for new railroad electrification systems which utilize single-phase current at 60 Hz and at higher voltages of 25 and 50 kV with and without auxiHary transformers. Modern catenary configurations are presented. A computer program is described which calculates the impedances of multiple track configurations and includes the effects of magnetic conductors (rails), of auxiliary transformers and of earth return. References to test results on rail impedances are also presented. A method is described to calculate train voltages for radial feed, centerfeed, and double-end feed systems and for multiple catenaries. Equivalent circuits are derived and specific examples of modern catenary systems are given.

Train Voltage Analysis for AC Railroad Electrification

INTRODUCTION E lec tr ic ra ilw ay propu lsion retu rn current flow s along the running r a ils in the im m ediate v ic in ity of trains. The ra ils act a s leaky ground cond u ctors in returning the current to the su b sta tion . If the running ra ils a lso carry track sign a llin g current, the in te r -r a il e le c tr ica l adm ittance c a u se s shunting of p art o f the track circu it current. The con n ection o f s tr u c tu r e s to the ra ils , for sa fe ty or o th er r e a so n s , m od ifies th is grounding im pedance and can cause s a fe ty p rob lem s when r a ils are used for the return of propu lsion current. It can also in ter fere with the co rrec t op era tio n o f track c ir cu its . D eterm ining the flow o f propulsion and signalling currents, and the a sso c ia te d p o te n tia ls , through the ground in an e le c tr if ie d ra ilw ay is im portant for a number o f reason s. E xcitation o f nearby ea rth retu rn circu its can resu lt in in te r fe re n c e , corro sio n prob lem s and danger to personnel. The ca lcu la tion of cu rren ts and p oten tia ls in nearbv underground condu ctors such as cab les and p ip es req u ires knowledge o f the e le c tr ic a l p ro p erties o f the earth, in particu lar th e r e s is t iv i ty o f the local soil. The tra ctio n eng in eer is in te re ste d in current propagation to d eterm in e the netw ork im pedances and track-ground v o lta g es . The ground return current problem can be analysed by co n sid er in g the d istribution o f track v o lta g es and cu rren ts. This problem was apparent in early e le c tr ic ra ilw a y s . For exam ple, Riordan [I] considered current propagation along rail tracks and their asso c ia ted co n d u cto rs, and Sunde [2] d erived general formulae for c u r re n ts and v o lta g es along stra ight, uniform w ires laid on the su r fa c e of the earth , making various assum ptions about earth in g and excita tion conditions. C urrents and potentia ls in teK.communications cab les due to harm onic com ponents o f traction current are a major problem , and Rosen's [3] ea r ly analytic m ethods have been the subject o f recen t com puter m odelling by Mellitt et al 14]. For DC-fed ra ilroads and rail tra n sit sy s tem s , e le c tr o ly t ic corro sio n m ay occur if su bstantia l current e sca p es to ground from track com ponents and m ateria ls . This co rrosion can be a particu lar problem for nearby m etal gas and w ater p ip es, and ca b les . Corrosion problem s have been con sid ered by se v e r a l authors. Takihara [5], for exam ple, evalu ated r a ilto -e a r th v o lta g e and rail current and gave e s t im a te s of rail leakage r e s is ta n c e . Kneschke 16) and Shaffer [7] prop ose design so lu tion s for particular problem s arising from s tr a y curren t e ffe c ts . S a fe ty is a lso a problem , sin ce hazardous s te p and touch v o lta g e s m ay be p resen t on the ra ils . Jacim ovic 18] has eva lu ated sa fe ty v o lta g e le v e ls and related the r esu lts to p ractica l s itu ation s. TRACK ELECTRICAL CIRCUIT AND TRANSMISSION LINE MODELLING Transm ission lin e equ ation o f propagation Currents and v o lta g e s along the balanced conductor pair r ep re se n te d by the running r a ils and shown in Figure I are d eterm ined by standard tra n sm iss io n line analysis in term s o f exponentia l, tr ig o n o m etr ic or hyperbolic functions, in exponentia l form , the line v o lta g e and current are*. V (x) = _V l_ [eYX+ u e " Yx] ( i ) 1 + U and l(x ) IL [e*^ u e ”YX]. (2 )

Investigation into track parameters for simulation of electrified railway systems

Cost considerations have been a major factor in the developments which have taken place in BR's 50 Hz a.c. electrification since 1960. The first efforts towards cost reduction were directed towards the more economical application of established techniques and included the elimination of brick buildings to house ancillary equipment and the use of switchgear in a steel housing with bare overhead connections to the contact system. Subsequently, the development of the vacuum interrupter was seen to offer prospects for still greater economy in switchgear, and a design of great simplicity has been developed in which the vacuum-interrupter circuit breakers and all ancillaries are housed in one modular enclosure. 144 vacuum-interrupter 25 kV single-pole single-phase circuit breakers are now on order. Advantage has been taken of developments in solid-state devices to develop faster protection for track feeders and to apply a supervisory system of the continuously scanning type in which the wear and tear associated with electromagnetic devices is minimal. The basic principles are given. It continues to be necessary to suppress inductive interference at source and established methods are used. The harmonics generated by the rectifiers on the motive-power units are a matter affecting the power-supply network, and information is given concerning the magnitude of these. A table of costs applicable to the beginning, the middle and the end of the period shows that they have been held down in spite of inflation.

Development of power supply and supervisory equipment for British Railways 50 Hz a.c. electrification

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Development of power supply and supervisory equipment for British Railways 50 Hz a.c. electrification