A Method of Calculating Thermal Aging State of Cable Using Cable Load Current

Abstract

The invention provides a method for calculating thermal ageing states of cables by utilizing load current of cables. The method comprises the following steps: obtaining a cable laying type and environment parameters; measuring geometric structural parameters of cables and reading heat capacities and heat resistances corresponding to layers on the cables as well as resistance parameters of metal parts on the cables, wherein the environment parameters, the heat capacities, the heat resistances and the resistance parameters are used as calculation parameters; establishing a mathematic model of relationship between the load currents and temperatures of the cables in a cable group according to the calculation parameters and the geometric structure parameters of the cable in the cable group, and calculating the real-time temperatures of the cables by utilizing a real-time iteration manner; calculating the ageing additive effect of the cables according to the obtained real-time temperatures of the cables. Compared with the conventional online monitoring method, the method disclosed in the invention can be used for improving the condition that the conventional online monitoring method is large in interference and more in false alarms, and carrying out real-time online monitoring on all the cables of power grid systems so as to lighten the load of offline test work and enable the operation and maintenance personnel to pointedly detect the cables in high-danger areas.

Description

technical field [0001] The invention relates to the technical field of high voltage and insulation, in particular to a method for estimating the thermal aging state of a cable by using the load current of the cable. Background technique [0002] During the long-term operation of the cable, the XLPE insulation layer will undergo thermal aging due to the temperature generated by the load current. As the running time increases, the thermal aging of the cable will have a cumulative effect, resulting in a gradual decline in insulation performance. If it is not evaluated and monitored in time, there will be a high probability that the cable body will break down eventually, resulting in a vicious power outage. . [0003] The existing on-line monitoring methods of cables have been widely used, but the main methods rely on monitoring the changes of various weak currents to determine their insulation status. Due to various types of electromagnetic interference on site, the current c...

AI Technical Summary

Problems solved by technology

However, the amount of transmission and distribution cables in a provincial capital city is basically more than 8,000 km, and the amount of cables in megacities is even more. If the traditional off-line diagnosis method is used to regularly detect all of them, the workload is too large, and it is difficult to implement in practice. Therefore, the actual In use, only some key lines can be tested, and the coverage is limited

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