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Analysis of operation failure low voltage buried armored cable

Information Source:Henan Huadong Cable Co., Ltd  Release date:2014-02-08

    At present the low buried cable armoring layer processing a variety of ways, both single earthing, also has two grounding. There are two hanging is not grounded. According to the site on both ends of the cable steel tape armored processing mode, cable faults, the fault point appearance form will be different.

    Both ends of the cable steel strip are suspended, not grounding. Cable short-circuit fault occurs, the breakdown point may be local cable lines appear breakdown burning holes, not make long distance large area burned carbonization. Because when the cable local accident caused sheath insulation damage mechanical injury, the system may not be immediately trip off, damage due to moisture in the soil and moisture, fire in big generate intermittent flashover phenomenon, eventually developing a permanent ground and phase short circuit and tripping outage, due to the discharge of current is limited in the cable damage location, the discharge current through the strip of land has not formed a branch circuit, so the cable fault in the cable full generally only one point fault. But this time the armored layer surface will be charged, in electrical safety considerations, armored cable ends exposed must be insulated sealing treatment.

    The cable line strip using single end grounding or double end grounding, cable faults, the fault may be a section of cable, cable local regions may appear long distance surface burning carbonization adhesion phenomenon. Because the steel to adopt this kind of connection, when the cable local single-phase grounding fault will flow in cable strip large short-circuit current; three-phase load current at the same time, cable will also appear unbalanced phenomenon, in the strip may be accompanied by eddy current phenomenon, two kinds of current common through the strip, strip would like a big power electric furnace, sheath of cables and insulated heating, plus customers switch selection, soil local cooling is not good, the thermal resistance is too large, cable local reserved coil packing, heat is not good, bad, it may cause the cable insulation, sheath appears long distance and large area burn carbonization adhesion phenomenon. Burn more random, probably near the fault point, possibly in another section, often in the most difficult heat dissipation, the largest section of the most severe thermal burn. Until the single-phase grounding for the development of two-phase short circuit system may only trip, not reclosing of transmission.

    For low voltage cable armored cable, it is necessary to strengthen the real-time online monitoring of cable of the three-phase current. At the same time, armor layer grounding, should be the installation of steel armor layer current transformer current monitor. The single-phase grounding fault of cable appears, early discovery and treatment, in order to avoid cable hair growth from burning phenomenon, cause power economic loss is not necessary, and ensure the economic type, the reliability of power grid operation, stability and safety.

    According to the analysis of the normal, buried low voltage cable short-circuit fault occurs, the fault point should generally only one. But in actual cable fault excavation process, low voltage cable fault may be two or more fault, also may be accompanied by long distance insulating sheath burning carbonization adhesion phenomenon. The author thinks that may be associated with different grounding cables or not ground pressure armored cable failure phenomenon, ideas and views are not necessarily correct. Hope to have sincere and profound view on this phenomenon of professionals will be able to put forward more analysis and views of scientific authority. In order to reveal the deep reasons of this phenomenon.

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