Pay attention to the heating phenomenon of power cables

2018年08月01日

The insulation strength of power cables refers to the ability of insulation structures and insulation materials to withstand electric fields without breakdown damage. In order to check the quality of power cables and ensure the safe operation of products, all insulation type power cables are generally tested for insulation strength. . The dielectric strength test can be divided into a withstand voltage test and a breakdown test.

 

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The withstand voltage test is to apply a certain voltage to the sample under certain conditions, and after a certain period of time, whether or not the breakdown occurs is used as a criterion for judging whether the test article is qualified. The voltage of time is generally higher than the rated working voltage of the sample, the specific voltage value and the withstand voltage time, which are specified in the product standard. Through the withstand voltage test, the reliability of the product operating under the working voltage can be tested and the seriousness of the insulation can be found. Defects can also find some shortcomings of the production process, such as: severe external damage to the insulation, serious defects on the conductor that cause the electric field to be sharply distorted; insulation has penetrating defects or large conductive impurities in production.

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The reasons for the heating of the power cable during operation are as follows: 1. The cable conductor resistance does not meet the requirements, causing the cable to generate heat during operation. 2. The cable selection type is improper, causing the conductor cross section of the cable to be used to be too small, and an overload phenomenon occurs during operation. After a long time of use, the heat generation and heat dissipation of the cable are unbalanced to cause heat generation. 3. When the cable is installed, the arrangement is too dense, the ventilation and heat dissipation effect is not good, or the cable is too close to other heat sources, which affects the normal heat dissipation of the cable, and may also cause the cable to generate heat during operation. 4. The joint manufacturing technology is not good, the crimping is not tight, and the contact resistance at the joint is too large, which may cause the cable to generate heat. 5. The insulation between the phases of the cable is not good, resulting in a small insulation resistance and heat generation during operation. 6. The partial sheath of the armored cable is damaged. After the water enters, the insulation performance will be slowly destructive, resulting in a gradual decrease in the insulation resistance, which will also cause heating in the cable operation.

 

    The rushing international breakdown test is to measure the breakdown field strength or breakdown voltage under certain test conditions by increasing the voltage until the sample breaks down. The power cable breakdown test can be used to assess the safety margin between the cable's ability to withstand voltage and the operating voltage. One of the important parameters in cable design when penetrating the field strength, if there is a fever, you need to pay more attention.



This article comes fromLinyi City Benliu International Trade Co., Ltd.



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