The article describes a problem that occurs in electrified railway transportation, involving the interaction between the earth-return circuits of different power systems. One of the analysed circuits is the earth-return circuit of a high-voltage power grid, the other is the return path of a 3 kV DC traction power supply system. The paper presents the results of the field tests carried out so far and discusses a mathematical model developed in the Matlab-Simulink environment with the aim of determining the interaction between both of the said systems. Keywords: earthing, traction substation, traction return system

When comparing the performance indicators of electrical networks with different types of neutral grounding, along with the fulfilment of the requirement to ensure reliability of power supply to consumers, serious attention is drawn to the main network parameters influencing the performance of power supply systems. Analysis of research and its results, reported above, on the influence of the neutral ground of power networks on the reliability and electrical safety conditions of the power supply systems as a whole, on the damage of distribution networks and electrical equipment as well as on the working capacity of relay protection devices, provides an opportunity to estimate each specific operation mode of the neutral and to develop recommendations aimed at strengthening the positive indicators of the corresponding modes. Other things being equal, reliability of power supply to electrical receivers or reliability of distribution networks is mainly determined by the damage to network elements and the performance of relay protection devices. The degree of influence of these factors on the reliability of distribution networks depends on the neutral mode, which in turn determines the level of internal overvoltages and the nature of transient processes at earth fault.

Icing on the overhead contact line exclude the possibility of efficient current collection from the overhead contact line. The effects of icing can result in losses for carriers due to delay or cancellation of trains and also cases of damage to the traction infrastructure and pantographs. The existing methods of de-icing the traction network (mechanical, chemical and electrical) are currently ineffective. Therefore, it is necessary to develop a new electrical method that takes into account the detailed current fl ow in the over-head contact line. This article presents a model for calculating the current fl ow in the overhead contact line and the resistances of droppers, suspension elements, and distance holders measured on the basis of actual measurements. Keywords: simulation model, de-icing of the contact line, current flow in the contact line

Elektryczne pojazdy trakcyjne do niezawodnej pracy i utrzymywania osiągów eksploatacyjnych, na które zostały zaprojektowane, wymagają niezawodnego zasilania. Zasilanie to jest gwarantowane poprzez system zasilania trakcyjnego. Cechą charakterystyczną dla obciążeń trakcyjnych jest ich duża zmienność, pobór prądu przez pojazd trakcyjny dużej mocy, przy niedostosowanym układzie zasilania jak i niedostosowanej sieci trakcyjnej powoduje zbyt duży spadek napięcia na pantografie, przez co pojazd traci właściwości trakcyjne, na które został zaprojektowany. Niniejszy artykuł poświęcony jestprogramowi napisanemu w środowisku MATHCAD do obliczania napięcia na pantografie elektrycznego pojazdu trakcyjnego, który zmienia swoje położenie, oraz obliczania prądów obciążeniowych i zwarciowych w sieci trakcyjnej.

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