Janusz Prusak

The article presents some of the results of measurements of loads for a selected tram traction substation for a continuous period of time covering sixteen weeks (112 days). Particular attention was paid to overloads occurring in consequent days. The second part of the article presents the analysis of overloads relating to the time interval of 60 minutes in successive days. This analysis was implemented in Matlab using a two-layer feedforward artificial neural network (ANN). The results of the approximation of the analyzed overloads are promising. A continuation of research may lead to the formulation of mathematical equations that might be useful for designers in terms of sufficiently precise calculations of overloads of rectifier units of DC traction substations.

The article presents the global distribution of energy losses in a DC electric traction in specific cases and the impact of changing parameters on the efficiency of electricity transmission on the railway.

The article addresses – based on an existing section of a tram line – the evaluation of the capability to substitute an existing train substation (as a civil structure) with several smaller ones. Taking into consideration the real estate prices and the shortage of available plots in the centers of larger cities, the localization of a substation building poses a significant location and budget challenge, when it comes to new tram lines. Additionally, such objects (substations) often spark concern and protests among the tenants of the nearby houses, as they are considered to be the source of a dangerous electromagnetic radiation and, sometimes, noise. The possibility to significantly reduce the size of those objects would mitigate the aforementioned challenges – both environmental and budget-related.

Atmospheric icing on traction lines is very important problem because it causes difficulties of using electric vehicles by people and can result to breaking of traction lines. Heating the wire can preventing atmospheric icing.

The paper presents the load currents of two tram traction substations. These substations power lines with different characteristics of tram traffic. Loads were analysed for one working day and one public holiday. Attention was paid to the differences and similarities in the current waveforms. The demand level was assessed, with respect to the rectifier units in the substations. The time series method was used, inter alia, and chiefly an analysis of the characteristics of autoregression and partial autoregression was carried out, to act as a diversity index with respect to the nature of variability in the analysed traction load currents.

This paper presents further results of research on the load variability of rectifier units for the selected tram traction substation. Actual measurements were used in the performed analysis. This time, the analysis was focused on the characteristics of maximum loads and overloads for time periods of five minutes and sixty minutes, for a number of selected cases. The second part of the article discusses the effectiveness of the use of artificial neural networks of the feedforward type with one hidden layer with eight neurons to analyse the overloads of the traction substation over a longer time scale. The obtained positive results indicate that this type of research should be continued, using different variants of artificial neural networks.

The existing railway from Kraków to Zakopane is characterised by complex horizontal (curves) and vertical (slopes and rises) profiles. Although the railway is attractive to tourists, it is not highly valued by carriers. This article describes a new route with profile modifications. The new route would be possible mainly due to civil engineering structures such as tunnels. It would make it possible to reduce travel time significantly and reduce energy consumption.

The first part of this paper presents a comparison of the measured and simulated results of the load variability of rectifier units of a tram traction substation. The subject of the tests was a power supply substation for the contact line of a tramway, the profile and traffic of which was known. After a positive appraisal of the applied simulation method, an assessment of the range of load variability for the rectifier units took place for a hypothetical situation involving the concentrated disposition (layout) of the traction substations (socalled micro-substations). The results acquired under the described circumstances are presented in the second part of this paper.