Method for establishing steady-state thermal circuit model of 10kV three-core cable based on segmentation method

Abstract

The invention discloses a method for establishing a steady-state thermal circuit model of a 10kV three-core cable based on a segmentation method. The method comprises the following steps: according to symmetry of temperature distribution of a radial section of the three-core cable, symmetrically segmenting the radial section of the three-core cable to form 1 / 3 radial-section three-core cable parts, wherein each segmented part contains a cable core; according to a heat transfer principle, establishing a simplified steady-state thermal circuit model of the 10kV three-core cable; for each segmented 1 / 3 three-core cable part, calculating the thermal resistance of each material layer; by a node voltage method in a comparison circuit, establishing a temperature equation for each node, and deducing a calculation formula for working out a conductor temperature from a cable skin temperature of the 10kV three-core cable under a steady-state condition. According to the method, the radial section of the three-core cable is symmetrically segmented into three parts by the segmentation method, so as to establish the steady-state thermal circuit model of the segmented 1 / 3 three-core cable part, so that a steady-state thermal circuit calculating model of the cable in the practical application can be guided, and deducing calculation of the real-time conductor temperature from the real-time cable skin temperature can be achieved.

Description

technical field [0001] The invention relates to the technical field of power cable analysis. Specifically, it relates to a method for constructing a steady-state thermal circuit model of a 10kV three-core cable based on a division method. Background technique [0002] With the rapid development of my country's economy, the demand for urban electricity is increasing, which directly leads to the increasing current carrying capacity of urban distribution network cables. Therefore, it is very likely that the ampacity of the distribution network cable exceeds the upper limit, that is, the cable overload situation. When the cable is in severe overload operation, due to the overheating of the cable core, the temperature of the insulation layer exceeds its maximum withstand temperature, resulting in a decrease in the insulation performance of the insulation layer, accelerating the aging of the cable, and even causing the cable to fail, thereby affecting the reliability of the city'...

AI Technical Summary

Problems solved by technology

At present, the research method of estimating the cable conductor temperature from the surface temperature of the cable is mainly the thermal circuit method. Due to the special structure of the upper three-core cable, when using the thermal circuit method to calculate, in addition to the IEC standard, domestic scholars have proposed a three-core cable with the same structure according to its special structure. Axialization method is used to establish the thermal circuit. Although the above methods can also calculate the cable conductor temperature from the cable skin temperature, they all take the entire three-core cable as the research object.

At this time, it is necessary to consider the mutual heat transfer between the three wire cores inside the three-core cable and the influence of the three wire cores on the external heat transfer, which greatly increases the complexity of the research and also increases the difficulty of establishing the thermal path model. It is difficult to accurately calculate the temperature of the three-core cable to the conductor, so that the ampacity of the running cable cannot be correctly determined

Images