High-voltage power cable single-phase sheath double-end direct grounding method and system

Abstract

The invention discloses a high-voltage power cable single-phase sheath double-end direct grounding method and system. The two ends of an intermediate-phase single-core cable sheath are directly grounded; in addition, one end of the sheath of the two-phase single-core cable is directly grounded, the other end of the sheath is grounded after being connected with a protection device, and the metal sheath of the middle phase serves as a return wire, so that the equipment cost of the return wire and the protector is saved, and the risk that the return wire is stolen is avoided; especially, when a fault occurs in the intermediate phase with two ends directly grounded, the induced voltage of the fault phase sheath is obviously reduced; when any phase of which the two ends are not directly grounded fails, the induced voltage of the fault phase sheath is slightly reduced; the grounding mode provided by the invention is more suitable for cable loops laid in parallel. According to the grounding mode provided by the invention, the induced voltage of a cable sheath under a fault condition is reduced, the use of a return wire and a protector is reduced, and the engineering construction cost and the return wire arrangement time are reduced.

Description

technical field [0001] The invention relates to the technical field of high-voltage power cables, and more particularly, to a method and system for direct grounding of double ends of a single-phase sheath of a high-voltage power cable. Background technique [0002] With the rapid development of the city, the built-up area continues to extend from the center of the city, and the demand for overhead lines of 110kV and above has surged. Cables of 110kV and above are all single-core forms. According to long-term operating experience, the defects of the grounding system will evolve into cable faults, resulting in immeasurable losses. Therefore, the cable grounding system has attracted more and more attention in the industry, and the selection and The detection of ground loop current has also become an important work in the design and operation and maintenance of cables of 110kV and above. [0003] In the prior art, in the process of cable engineering design, when the cable is sh...

AI Technical Summary

Problems solved by technology

[0013] Considering the design structure of urban cable passages, it can be seen that the single-core cable grounding method of prior art 1, although the return line is canceled, cannot reduce the induced voltage of the metal sheath of the fault phase, and the induced voltage of the metal sheath of the non-fault phase is also reduced. High, which brings a great hidden danger to the safe operation of the cable

In prior art 1, under normal working conditions, the reactor is resistive, but because the power frequency is 50 Hz, the current flowing through the reactor into the ground still has a certain value, so that the value of the circulating current in the sheath is still large and cannot be ignored. At this time, the induced voltage in the sheath may be greater than the insulation withstand strength of the cable metal sheath; in addition, under the overvoltage condition, if the reactor is turned on, because the reactor is a non-ideal inductance, there is still a certain value of resistance , if a large current is conducted, the reactor may explode, and if the selection of the reactor is increased, the equipment will be bulky and difficult to install in the grounding box

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