Views: 250 Author: Site Editor Publish Time: 2020-12-08 Origin: Site
The overhead line is erected on the ground, which is used to fix the transmission line on the tower standing on the ground to transmit electric energy. The overhead power lines and maintenance are convenient and the cost is low, but it is easily impacted by the weather and environment (such as strong wind, lightning, pollution, ice and snow, etc.) and causes faults. At the same time, the whole transmission corridor occupies a large area of land, so it is easy to cause electromagnetic interference in the surrounding environment.
Steel-cored aluminum stranded wire or aluminum stranded wire shall be widely used for overhead lines. The cross-section of aluminum stranded wire of high-voltage overhead line shall not be less than 50 square millimeters, that of core aluminum conductor shall not be less than 35 square millimeters, and that of the empty line shall not be less than 16 square millimeters. Moreover, the conductor cross-section should meet the maximum load needed. In addition, the selection of cross-section should also meet the voltage loss of not more than 5% of the rated voltage (high-voltage overhead lines), or 2% - 3% (lighting lines with high visual requirements), and should meet certain mechanical strength.
First of all, the relevant personnel in the construction and completion acceptance must follow the relevant regulations to ensure the construction quality and safety of the line. Secondly, the route should be established reasonably, which requires a short path, a few corners, convenient transportation, and a certain safe distance from the building. Finally, according to the requirements of relevant regulations, it is necessary to ensure that the overhead line is within a safe distance of the earth and other facilities. Remote monitoring system and safety earthing and short circuit kit play an important role in it.
Line grounding can be divided into single-phase grounding, two-phase grounding and three-phase grounding. There are two kinds of grounding faults: permanent grounding and instantaneous grounding. The former is usually an insulation breakdown, conductor landing, while the latter is usually lightning flashovers and foreign matters falling on the conductor. One of the most common is the single-phase grounding of overhead lines. For high-voltage transmission lines, in addition to line protection devices, earth fault indicator, ground fault monitor, fault recorder and traveling wave fault locator will be installed in the substation. Some are also equipped with wavelet range finders. The traveling wave and wavelet distance measuring device can accurately determine the location of the grounding point, and the accuracy can reach 5km and 1-2km in general. It is very useful for fault line checking.
In the distribution line, due to the horizontal arrangement of lines and the small distance between lines, if the sag of conductors in the same span is not the same, the swing of each conductor is not the same in case of strong wind, which leads to the collision of conductors, resulting in phase to phase short circuit. Therefore, the construction must be strictly controlled, and the tension of the conductor needs to be paid attention to, so that the galloping of the three-phase conductor is equal and within the specified standard range. During the inspection of the line, if the above problems are found, they shall be handled on time. Digital cable fault indicators and automated electrical wire fault indicators can find fault problems efficiently and timely, so as to improve our work efficiency of maintaining safety.
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