Purchase your copy of IEC as a PDF download or hard copy directly from the official BSI Shop. All BSI British Standards available online in. Find the most up-to-date version of IEC at Engineering IEC Edition INTERNATIONAL. STANDARD. NORME. INTERNATIONALE. Railway applications – Fixed installations.
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The negative return portion of a modern direct current dc traction power system, which includes the tracks the running railsis normally isolated from earth to the maximum extent practical.
The purpose of this isolation is to prevent stray dc currents from flowing through the earth and potentially causing corrosion of nearby metallic infrastructure.
DC traction power supply – Rail Electrification – Global
The isolation of 6218-1 tracks from the earth is not perfect. Each track tie and insulated rail fastener assembly can be electrically represented as a resistor of high ohmic value connected between the rails and the earth.
For modern dc traction power systems in particular, however, this resistance is high enough for the rails to be considered essentially ungrounded with respect to local electrical ground earth. The lack of an intentional connection between the tracks and earth allows voltage differences to occur along the rails, and between the rails and nearby structures.
These voltage differences are caused by the flow of current through the running rails back to the substations. Since the shells of rail vehicles are typically at the same voltage as the wheels and rails, this voltage difference could be impressed on a passenger entering or exiting a train from a grounded platform.
Or they could iex impressed on a person walking along the tracks. Voltage-limiting equipment that can be installed in passenger stations and other accessible locations has been developed in response to the requirements of EN These devices quickly connect the running rails to the station structure to eliminate unsafe voltage differences.
DC traction power supply system
If an earth fault occurs broken catenary conductor falling on the ground, for examplethere may not be a low-resistance circuit back to the substation due to the electrical isolation between running rails and earth ground. Without a low-resistance path back to the substation, there may be a resulting low-level short circuit current flow insufficient to operate the substation protective systems.
As a result, the area in the vicinity of the fault may potentially be elevated to unsafe voltage levels. Equipment intended to detect this condition and connect the substation negative dc bus to the substation grounding grid is gradually being incorporated into modern North American jec traction power substation design.
EN includes voltage-time curves that dictate the maximum permissible magnitudes and durations for ac and dc voltages; equipment built to EN must clamp the highest voltages in no more than 20 milliseconds.
This paper will review current American and European standards and codes for maximum permissible rail voltage on direct current traction power systems.
The maximum permissible voltage levels will be explained and compared. The principles of negative grounding device operation and corresponding voltage settings will also be discussed.
American Society of Mechanical Engineers. A Review of Current Standards and Codes for Maximum Permissible Rail Voltage Rise on Direct Current Traction Power Systems The negative return portion of a modern direct current dc traction power system, which includes the tracks the running railsis normally isolated from earth to the maximum extent practical. Stell, R W Benjamin Conference: Figures; References; Tables; Pagination: Traction power Geographic Terms: Europe ; United States Subject Areas: Nov 9 3: