Method applied to calculating thermal resistance and thermal resistance of high-voltage cable capacity-increasing soil

Abstract

The invention discloses a method applied to calculating the thermal resistance and thermal resistance of high-voltage cable capacity-increasing soil. The method comprises the following steps that S1, based on the heat transfer theory, a first-order thermal resistance and thermal capacitance T-type thermal circuit model of the external environment of a cable is established; S2, a thermal transfer formula is established based on the definition of the thermal resistance and the thermal capacitance and the heat conservation law; S3, the step value is set and calculated, and the thermal resistance and thermal capacitance of the external laying environment are obtained through the cable metal sheath temperature, cable outer sheath temperature and environment temperature measured in real time according to the two-point interpolation derivation formula. According to the method, the thermal capacitance and thermal resistance of the soil are solved through multiple algebraic equations obtained through the values, measured at different layers and different times, of the cable, the measurement efficiency is high, measurement is easy and convenient, and the method is suitable for popularization.

Description

technical field [0001] The invention relates to the field of increasing the capacity of high-voltage cables, in particular to a method for calculating the thermal resistance and heat capacity of soil applied to increasing the capacity of high-voltage cables. Background technique [0002] With the increasing demand for power, higher requirements are placed on the load of the cable, but it must be ensured that the temperature of the cable conductor during operation cannot exceed the allowable value. Therefore, accurate calculation of conductor temperature has become an important means to monitor whether the cable is running safely. Due to the existence of thermal resistance and heat capacity of the actual cable laying environment, it will affect the heat transfer process of the cable. Therefore, when calculating the conductor temperature, the part of the cable heat dissipated into the environment cannot be ignored, otherwise the calculation of the conductor temperature direct...

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Problems solved by technology

[0004] However, both the IEC standard and the environmental parameters obtained by engineers from experience have certain defects. These recommended values ​​only have a certain reference value in specific areas, considering the actual cable laying environment and the influence of seasonal climate changes on soil properties. , especially the moisture content of the soil has a great influence on the thermal resistance coefficient of the soil. The error caused by this standard or empirical value will cause great inaccuracy in the calculated cable conductor temperature, making it not much The practical significance of the use of

The steady-state measurement method is very labor-intensive, and each measurement takes more than ten days, which is obviously not very practical

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