Method for determining power-frequency design field intensity of high-voltage crosslinked polyethylene cable

Abstract

A method for determining the power-frequency design field intensity of a high-voltage crosslinked polyethylene cable comprises the step of manufacturing insulation test blocks of the crosslinked polyethylene cable, the step of manufacturing and preprocessing pin electrodes, the step of manufacturing test specimens for an electrical tree test, the step of conducting an electrical tree initiation test and data processing under a power frequency voltage, the step of conducting an electrical tree initiation test and data processing under the 400 Hz alternating voltage, the step of determining the critical voltage of electrical tree initiation through an impressed voltage and electrical tree initiation time, the step of calculating the critical field intensity of electrical tree initiation according to the size of an electrode system, and the step of determining the power-frequency design field intensity of the crosslinked polyethylene cable through an electric field enhancement coefficient. According to the method, the number of the needed test specimens is small, operation is simple, and control is easy. The determined power-frequency design field intensity can truly and effectively reflect power frequency voltage resistance of the high-voltage crosslinked polyethylene cable with the long service life. The method can be directly used for insulation thickness design of the cable, and guarantees that high-voltage power cables which can meet the technical requirement for long-time and reliable operation and have economic advantages are designed during new product development.

Description

technical field [0001] The invention relates to a method for determining the power frequency design field strength of a cable, in particular to a method for determining the power frequency design field strength of a high-voltage XLPE cable. Background technique [0002] Due to the advantages of convenient installation, easy maintenance, and environmental friendliness, AC polyethylene insulated cables have been widely used in AC and DC transmission and distribution networks. In recent years, in newly installed AC lines with a voltage level of 150kV and below, the usage of XLPE insulated cables has exceeded that of traditional oil-paper insulated cables; and in the field of ultra-high voltage power transmission, the usage of XLPE cables has also on the rise. As early as the 1990s, AC 500kV XLPE cable products had passed the test and put into practical operation in Japan. In contrast, although more than 90% of the cable lines in the domestic power grid system use XLPE cables,...

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Problems solved by technology

[0024] In order to solve the above-mentioned problems in the prior art, the object of the present invention is to provide a method for determining the power frequency design field strength of high-voltage XLPE cables, which overcomes the problem of using the 1-hour power frequency breakdown field strength to carry out the cable insulation design voltage. The shortcoming that the withstand index has a great influence and the voltage withstand index is difficult to accurately measure, it also overcomes the need to measure the long-term power frequency breakdown field strength for cable insulation design using the power frequency design field strength, and uses the breakdown test to determine the high voltage crosslinking. The long-term power frequency breakdown field strength of polyethylene cables has the disadvantages of high equipment requirements, difficult operation, time-consuming and labor-intensive, and large sample volume

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