STRAY CURRENTS (EN: stray currents; DE: Streustrome, Schleichstrome, Irrstrome, Blindstrome; FR: courants vagabonds; ES: corrientes vagabundos; RU: блуждающие токи) are the currents of the leakage into the ground from the grounded electrical devices (rails of the electrified transport, working groundings of the electrical power transmission lines, electrical power cables at the places of the breach of insulation, and so on).
The shape, amplitude, and direction of the stray currents are not constant. At the mining works, the stray currents can cause the injuries of the people, fires, early explosions of the electrical detonators, interferences within the channels of communication, intensification of the corrosive destruction of the metallic equipment and built structures, which are located within the ground (pipelines, communication cables, casing strings of the drilled wells, and so on). In the corrosive sense, there are especially dangerous the stray currents from the sources of the direct or rectified current. Within the anodic zones, where the current flows into the ground from the metallic parts, the destruction of the metal proceeds with the speed of up to 10 millimetres per year.
They perform the protection against the corrosion, which is caused by the stray currents, using the amplified and polarized drainages, cathodic stations, or polarized protectors. For example, for the protection of the steel pipelines, they use the cathodic polarization (against the stray currents of the industrial frequency) with the protective potential within the limits of 0.87-2.5 volts according to the copper-sulfate electrode for the comparison. In order to limit the magnitude of the stray currents from the current-conducting railway tracks, they perform their sectioning, the decreasing of the electrical resistance of the joints, they increase the contact resistance between the rail and ground, they decrease the distance between the traction substations and suction points. Within the networks of the alternating current, they limit the magnitude of the stray currents with the usage of the protection against the short-circuits with the ground.
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