A Calculation Method of Induced Current in Sheath Under Multi-phase and Multi-point Grounding of Cable Metal Sheath

Abstract

The invention discloses a method for calculating the induced current of a metal sheath of a cable under multi-phase and multi-point grounding, which comprises the steps of S1, calculating and measuring the resistance R and reactance X of the metal sheath of the cable, the grounding resistance R1 and R2 at two ends of the cable and the earth leakage resistance Re; S2, calculating the length proportions [alpha]i, [beta]j and [gamma]t of each small section to the total line, and measuring fault grounding resistance Rki, Rgj and Rft; S3, calculating the metal sheath reactance Zki, Zgj and Zft of each section of the branches of the three-phase cable, and calculating circuit induced electromotive forces Uki, Ugj and Uft, which are generated by wire core current of the three-phase cable, of eachsection; S5, calculating induced electromotive forces Uki', Ugj' and Uft', which are generated by circulating current in the sheath of the three-phase cable, of each section; and S6, calculating induced current Iki, Igj and Ift of each section of the branches of the three-phase cable. The induced current value on each section of the cable under the multi-phase and multi-point grounding condition can be conveniently calculated according to the invention.

Description

technical field [0001] The invention relates to the technical field of power cables, in particular to a method for calculating induced currents of multi-phase and multi-point grounding undersheaths of cable metal sheaths. Background technique [0002] The induced current of the high-voltage cable sheath is an important part of the sheath circulation. Relevant standards have been formulated for the limit of the sheath circulation value in engineering. Excessive sheath circulation will lead to power loss, insulation aging, reduced current carrying capacity, and serious heating. It will even burn the ground wire, causing the power system to malfunction. [0003] At present, domestic and foreign scholars have proposed the calculation model and calculation method of the sheath induced current during the normal current-carrying operation of the high-voltage cable. The changing law and trend of current provide a reliable reference standard for cable design and operation. [0004]...

AI Technical Summary

Problems solved by technology

[0004] However, as the cable is laid for a long time, the previous mechanical damage, insect bites and chemical erosion can cause multi-point grounding of the cable metal sheath. When the fault grounding points are in different phases, multi-point multi-phase fault grounding occurs

However, the existing calculation models and calculation methods cannot meet the calculation requirements, that is, the magnitude of the sheath induced current in the fault state cannot be calculated, and the distributed sheath induced current cannot be calculated.

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