Method for calculating current of single-core cable sheath

Abstract

The invention relates to a method for calculating the sheath current of a single-core cable, aiming at accurately calculating the sheath current of the single-core cable and providing guidance for reasonably configuring the sheath current and reactive power for laying and transformation of the cable. The method comprises the following steps: (1) determining the radius a of a cable core, the outerradius b of an insulating layer, the relative dielectric constant Epsilon, the relative permeability [mu]0 of the insulating layer, the resistance Rt of a cable sheath and the conductivity gamma of the insulating layer according to cable parameters; (2) determining a cable length l, a power supply voltage level Us, a power supply frequency f, a power supply voltage level Us and a cable grounding end grounding resistor Rd according to cable operation conditions; 3, calculating capacitive current IC of the single-core cable sheath; (4) calculating the inductive current IL of the single-core cable sheath; 5, calculating the resistive current of the single-core cable sheath; 6, calculating single-core cable sheath current through the following formula I: I =-j (IC+IL)+IR.

Description

technical field [0001] The invention relates to a power system, in particular to a method for calculating the sheath current of a single-core cable, which is suitable for calculating the no-load or light-load sheath current of cable lines. Background technique [0002] In recent years, urban overhead transmission lines have seriously affected the city environment, and urban overhead lines are gradually being replaced by underground cables. There are factors such as distributed capacitance and coupling inductance between the cable core and the metal sheath, so the single-ended grounding cable will generate a large sheath current even when it is no-load. When the cable voltage level is low, the no-load sheath current is small, but as the voltage level and transmission distance increase, the sheath current increases significantly. For example, the sheath current of a cable with a voltage level of 110kV and above can reach dozens of amperes under light load or no-load condition...

AI Technical Summary

Problems solved by technology

Excessive sheath current not only reduces the transmission efficiency of the transformer, the utilization rate of equipment and the voltage quality of the power supply system, but also has a serious impact on the corrosion of cable joints and the operating life of cables

In the no-load operation of the single-ended grounding cable, the capacitive current accounts for the main part of the sheath current. In actual operation, there is also compensation for the excessive capacitive current of the cable. However, even for cables with the same voltage level, due to various structural parameters , the degree of compensation is difficult to get effective cooperation

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