Volume 3 nr 1 / 2011 - Academia Oamenilor de Stiinta din Romania

120 Alexandru Ionuț Chiuță, Liviu Mihai Sima, Nicoleta Doriana Secăreanud) As in the power stations 110 kV / MV (for example IMGB), the short-circuitpowers vary from power substation to power substation and within the samepower substation from busbars to busbars, at National Power Dispatch wemade short circuit calculation, in real terms, for the entire electric powernetwork of the electrical company in the spring time. These results are neededto determine the interaction between electrical substations of the Subwaysystem and electric power network. This interaction depends on the powerlevel installed in the electrical company’s power substations and short-circuitspower at the point of connection;e) Through the Subway system tunnel, the harmonic currents close and penetratethrough transformers - power rectifier substations of Subway. They overlapwith the currents through cable casings which connect the Subway system andthe electrical company. In this way, a parasite movement occurs betweenSubway’s power substations and the electrical company’s power substations. Inthe electrical company power substations, power transformers are installed thatsupply the Subway system. They differ in number, power and short circuitvoltage. The power transformers with different characteristics are connected inparallel for a short period, causing a loop current circulation among the powersubstations of the Subway system and the electrical company.1.2. Features of subway traina) Trains of the Subway system, depending on how they were constructed andmaintained, have characteristics that differ from train to train;b) Depending on how the subway train is driven (according to the driver mentalstate) the current shock varies, as well as the shock duration and voltage shocks- on the DC (direct current) side As a result, the energy consumption varies;c) If the DC motors are not properly maintained and do not have anti-parasiticcapacitors, the ignition phenomenon at the collector occurs. This causes stresson the train wagons and electromagnetic disturbances;d) Depending on the sensor cleaning mode and the third metal track, sparks occurduring the start.1.3. Features of runwaya) Due to poor insulation of the runway along the tunnel in some areas, variablepotentials type "hopping" occur;b) Size and change of their variation were highlighted by measuring and recordingthe voltage drop on a portion of 500 m along the tunnel “U” shape – during thetime when this portion was covered by a train in start-up;Copyright © Editura Academiei Oamenilor de Știință din România, 2011Watermark Protected