Discussion on the grounding of power lines in the

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Brief discussion on the grounding of power lines in medium-sized cities

Abstract: combined with engineering examples, this paper introduces in detail all aspects of the grounding of power lines in medium-sized cities, so as to provide reference for the grounding of power lines in medium-sized cities in the future

key words: power line grounding discussion 1 Since the reform and opening up, Yuncheng area, located in the south of Shanxi Province, has developed rapidly, its economic strength has been continuously strengthened, and the pace of urban construction has been significantly accelerated. In 2001, Yuncheng City was approved as a prefecture level city by the State Council. Just after the establishment of the new municipal Party committee and municipal government, it made the decision of entering the three lines of the main streets of the city around the construction of a strong city in economy, tourism and industry, And organized the implementation of the third line grounding project of Zhongyin Avenue, and opened the construction of measurement accuracy of 10kV power line grounding in Yuncheng urban area. Up to now, Yuncheng Power Supply Branch has overcome various difficulties. After cooperating with the municipal government to complete the power line grounding project of Zhongyin Avenue, it has successively organized and implemented a number of power line grounding projects, such as Hedong street, Renmin South Road, Nanfeng square section of Yudu Avenue, huaidong Road, Yudu Avenue, Yuncheng West substation and Yuncheng North substation outgoing line. As engineering designers, Over the past few years, we have gained a lot in the access of power lines to the ground. 2. The entry of urban power lines into the ground is the requirement of economic development. In recent years, on the one hand, the power load in Yuncheng urban area has increased continuously and rapidly, and residents' expectations for power supply reliability have increased; On the other hand, the requirements of urban planning and construction are getting higher and higher, and the beauty of the city appearance has been paid more and more attention by the society. Due to the limitation of corridors and the number of circuits on the same pole, the transmission capacity of many streets can not keep up with the development of social electricity; Overhead lines have many faults and inflexible operation modes, which often cause large-scale power cuts and seriously affect the normal life of residents; Overhead lines are generally located on the side of the street, limiting the growth height of trees in the green belt; The private pulling and disorderly pulling of overhead lines across the street and other lines on power poles seriously affects the beauty of the city; Due to the influence of live lines and the interference of all aspects of society, the construction of urban overhead lines is difficult, and it is easy to cause accidents such as broken conductors and electric leakage that endanger personal safety. With the rapid development of cities in China, overhead lines have exposed many contradictions that are incompatible with urban development. Although the construction investment cost of cable line is high, which is several times that of overhead line, because it is laid underground, it does not occupy the ground and space, which is conducive to the beauty of the city; The same underground cable channel can accommodate multiple circuits, and the adaptability of transmission capacity is strong; Natural conditions (such as lightning, rain, salt fog, pollution, etc.) and the surrounding environment have little impact on the cable, and the power supply reliability is high; The cable is hidden underground, which is relatively safe for people; The operation and maintenance cost of the cable line is relatively small, and the construction is less difficult; With ring cabinet, junction box and other equipment, it can connect multiple lines to form a power supply network. The operation mode is extremely flexible, which can greatly reduce the number and scope of power outages, and it is easy to realize distribution automation. Therefore, with the development of urban economy, cable lines will increasingly replace overhead lines for urban power distribution because of their incomparable advantages. 3. Selection of cable laying method the civil engineering construction cost of cable route is generally large, and the cable laying method directly affects the construction cost of civil engineering, so reasonable planning and correct selection of cable laying method is the primary link of cable grounding work. The cable laying method shall be selected according to the engineering conditions, environmental characteristics, cable type, quantity and other factors, and shall meet the requirements of reliable operation, easy maintenance and the principle of technical and economic rationality. The laying methods of cables generally include direct burial laying, pipe laying, cable trench laying, tunnel laying, etc. The direct buried laying method is generally easy to implement, which has the significant advantages of long-term favorable PCB manufacturers, scattered PCB enterprises, serious product homogenization and low investment. However, due to the limitations of being easy to be damaged by external forces, aging, difficult to replace after accidents, and unable to repair after laying, it is not suitable to be used in urban trunk lines, and can be used for cable branch lines or user lines. Cable trench laying is relatively common, but after a long operation time, the trench cover is prone to fracture and incomplete damage during aging test, and the surface water is easy to overflow into the trench, which has a great impact on the beauty of the ground. Through the analysis of various laying methods, combined with the current situation of high groundwater level, poor urban drainage system and frequent ground water in Yuncheng City, the laying methods in Yuncheng City focus on pipe laying and tunnel laying (we will also discuss these two methods below), which have their own characteristics, See Table 1 for the comprehensive comparison: as mentioned above, the stability of this type of model is related to the sample. We used low friction high-strength vinylon cement cable duct and made economic accounting. The comprehensive cost per linear meter of laying 10 cable ducts is relatively close to the comprehensive cost per linear meter of 1.1m wide x1.9m high tunnel. Therefore, we believe that: in the area where the number of cable loops is small (planned 10 loops and below), the growth of power load is slow; Or areas with many underground obstacles and small load growth space, such as old urban areas, should give priority to the use of pipe laying; In areas with a large number of cable circuits (planned 10 circuits and above), the power load increases rapidly and the load is relatively important; Or areas with less underground obstacles and large load growth space, such as new urban areas and substation outgoing lines, should give priority to tunnel laying. Advantages and disadvantages: tunnel laying has good ventilation and heat dissipation, large cable carrying capacity and large transmission capacity, which is conducive to long-term safe operation. Operation, maintenance and overhaul are very convenient, especially it is easy to find accident hidden dangers and accident fault points, and it is easy to rush to repair, so as to shorten the time of power failure due to accident. It can accommodate multiple circuits and has strong adaptability and is not easy to be damaged by external forces. Generally, it is a brick concrete structure with local materials, simple construction technology and reliable construction quality. The cable construction period is short and it is easy to construct. The power system has a lot of internal operation experience and is easy to manage. It is applicable to areas with straight streets, especially in new urban areas, where the number of circuits is large and the load is important. The drainage problem is difficult to solve. Investment is larger than pipeline. The path adaptability is poor, and it is not suitable for road crossing or corridor difficult areas. Cable fire prevention is difficult to solve, and the investment in fire prevention measures is large

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