Shanxi Allen electric transmission and distribution equipment Co., Ltd. has been specialized in power construction, power installation and distribution installation for many years. It is a famous power installation company in Shanxi Province. Distribution lines are relatively complex projects in power installation projects. However, our company has rich experience in this field and has completed a lot of cases of 10kV distribution line construction and transformation projects, Next, our company will explain to you the fault analysis and preventive measures of distribution line engineering. Distribution line is an important part of power system. Distribution lines have many points, wide areas, long lines, complex paths, uneven equipment quality, and are greatly affected by climate, geography and environment. In addition, due to the direct connection to the client, the power supply and consumption situation is complex, which directly or indirectly affect the safe operation of distribution lines, resulting in high equipment failure rate and far more complex failure causes than transmission lines. According to statistics, 50 10 kV distribution lines within the jurisdiction of Guyuan Power Supply Bureau participated in the fault trip assessment, with a total length of 2310 km. In 2006, there were 24 fault trips of 10 kV distribution lines, reaching 0.01 times / km & bull; Year (0.48 times / piece & bull; year). Through fault analysis, try to find out the objective law of distribution line fault, and put forward preventive measures.

1. Annual line fault tripping trend

It can be seen from Figure 1 that the number of line trips is the most in May and June each year, while fault trips do not occur in November and December. Distribution lines are exposed in the field and are vulnerable to external factors, especially climate factors. From April to August, there are many thunder and lightning weather, with drought, little rain, little snow and occasional heavy rain. It belongs to a typical continental arid climate, with more dust, less rainfall and large temperature difference between day and night. The seasonal characteristics of climate change determine that the seasonality of distribution line fault is also very obvious. From the annual tripping situation, the line fault tripping is more serious between April and August, which is closely related to lightning weather. In normal weather in other months, the number of line trips is relatively small. In recent years, winter has been a warm winter. The climate in November and December is relatively warm and stable, so the equipment operation is also relatively stable. From the above analysis, it shows that the overall ability of 10kV distribution line to resist natural disasters is still low, that is, the safety factor of equipment is low. 2 distribution lines with serious tripping according to statistics, the distribution lines with high fault times in the whole year, 5 lines with annual fault times of 2 or more, and the total number of trips is 13, accounting for 54.1% of the total number of trips in the whole year. It shows that the fault tripping of 10kV distribution line is concentrated on several lines. Except for the 111 Zhongshan street line of Beijiao substation, several other lines have not been completely transformed. The line condition is poor, the line components are seriously aged, and the hidden trouble of the line has not been eliminated. As long as there is system equipment fault, or affected by climate, external force damage and other factors, The line trips, especially when the climate changes suddenly, the line trips are more serious and relatively concentrated. For example, three failures of 122 Honghe line in Pengyang substation occurred between April and August, and all of them were related to lightning. Therefore, during the equipment operation of these lines, it is necessary to strengthen management, eliminate defects, and carry out transformation in time to further reduce the fault trip rate. 3. Analysis of 10kV line fault trip

See Table 1 for classification statistics of 10kV distribution line faults.

It can be seen from table 1 that the main cause of line fault is the serious aging of insulators in some unmodified lines, the inherent hidden dangers of equipment have not been eliminated, and the line trip is particularly serious in case of sudden climate change. Secondly, the outdoor cable head is seriously struck by lightning, which shows that there are problems in the manufacturing process of cable head, and the ability of cable head to resist lightning attack is poor. In addition, tree barriers and user equipment faults are also important factors causing line faults. The faults caused by the above reasons account for 66.7% of the whole line faults. 4 cause analysis of line fault 4.1 the general situation of some unmodified distribution lines caused by the defects of line equipment is that the line is long, there are many branches, the equipment is seriously aged, there are many low-value insulators, there are many lightning arresters damaged, the conductor is loose, the sag of some spans is too large, and the conductor is easy to mix. These may cause line failure and cause high failure rate. In terms of operation, the zero value and low value insulators are not replaced in time, which is easy to cause grounding fault. Some distribution line arresters are not maintained for a long time, and the lightning protection effect is poor, which is easy to cause line grounding or lightning overvoltage accident in thunderstorm days. In the production of outdoor cable head, due to the rough process and poor treatment of cable head sealing and grounding, the ability of cable head to resist lightning attack is poor. It is easy to cause the cable head to be burned by lightning, and then trip the line. Failure of distribution transformer is also easy to cause line tripping, such as line failure caused by burning of drop fuse and broken lead. 4.2 the line fault tree barrier caused by external factors is an important cause of line tripping, especially the action tripping in windy and rainy days. If the reclosing is successful, it may be caused by the tree barrier. Tree barrier cleaning has always been a difficult problem in the line operation of power supply enterprises. The difficulty of tree barrier cleaning is mainly difficult to cut down, difficult to prune, large contradiction with tree owners, and the phenomenon of planting with clearing is more serious. There are also many line trips caused by user equipment faults. For a long time, the equipment of some users can not be maintained, the equipment is aging and old, the insulation condition is poor, and it is prone to failure, which often causes the tripping of distribution lines. External force damage is another main factor causing line tripping. This kind of damage mainly comes from villagers' private operation of transformers and thieves' theft of power equipment or wire cutting on the line. In case of the above phenomena, the bare metal may be directly overlapped on the running bare conductor, resulting in phase to phase short-circuit fault tripping. Vehicle hitting the pole is also an important external force damage factor. After the pole is hit, it is easy to cause line tripping. This phenomenon mainly occurs in densely populated areas such as urban areas, counties or market towns. In these areas, the pole density is large, there are many vehicles, and the pole is also more likely to be hit. Foreign matter conduction is also an external factor causing line tripping. When the iron wire is thrown on the line, the line trips immediately. 5 preventive measures 5.1 strengthen operation management. From the perspective of operation, operators shall inspect the equipment on time according to the requirements of operation regulations, timely and accurately provide equipment defects, provide basis for maintenance test, timely find accident hidden dangers and conduct maintenance in time, so as to reduce the line failure rate. From & ldquo; Strict & rdquo& ldquo; Diligent & rdquo& ldquo; Fine & rdquo& ldquo; Cooked & rdquo; Work hard. The operation and maintenance of insulators, lightning arresters and cables shall be strengthened. Carry out preventive tests periodically, strengthen maintenance, eliminate equipment defects in time and leave no hidden dangers. In view of the poor manufacturing process of cable head, the skill training of cable maintenance personnel shall be strengthened and the examination shall be carried out. 5.2 for the renewal and transformation of distribution lines, we should seize the opportunity of rural power network improvement project, completely transform the unmodified lines, update line equipment, and enhance the ability of distribution lines to prevent natural disasters. At present, several lines with serious line tripping should be included in the plan as soon as possible to carry out line transformation, so as to make the equipment meet the safety requirements. If the line is not equipped with section circuit breaker, it shall be reconstructed as soon as possible. 5.3 strengthen the tree barrier cleaning work. For the insulation transformation of some sections, the tree barrier cleaning shall be further strengthened. In the tree concentration area under some conductors and the tree barrier disaster area, the line insulation transformation shall be considered to reduce the line fault tripping. Overhead insulated conductor shall be adopted for insulation transformation in combination with the current line status. 5.4 strengthen the supervision of users' equipment. Considering the problem of economic investment, some users are not willing to invest in equipment maintenance subjectively, so that there is a certain degree of management vacuum in equipment safety management. Therefore, some users' equipment is old and can not be maintained. This situation is extremely unfavorable to the safe operation of distribution lines. Power supply enterprises should strengthen supervision and urge users to maintain or transform their equipment. Check frequently and put forward rectification suggestions to users. For the equipment that does not meet the operation conditions, it is recommended that the user exit the operation to prevent greater losses. 5.5 do a good job in preventing external force damage. The external force damage of distribution lines is relatively serious. Measures shall be taken to prevent. Hang warning signs, write propaganda slogans, etc. on the line tower, advise not to climb the live tower, do not break the line insulator or throw iron wire foreign matters on the conductor, and do not fly kites near the line. We should strengthen the prevention of external damage and theft in the hardest hit areas. Distribute leaflets, post posters and paint slogans in a planned and organized way, actively carry out mass line protection, establish mass line guards and reward meritorious personnel. For illegal buildings, they should be explained and discouraged from the early stage of construction. Solve the obstacle removal work in the line corridor year by year. For those who steal electric energy or power facilities, cause relatively serious property losses or cause major accidents, they shall be put on file for investigation through the public security system to effectively crack down on the arrogance of thieves. Get in touch with the urban construction department and the construction department, cooperate with the planning, design, construction and other work in safety production, and avoid potential power accidents. The causes of distribution line faults are complex, which makes the line fault rate high. Preventing distribution line faults is a long-term and arduous task, which should be summarized and improved through practice. It is an important work to carefully analyze and study the internal and external causes of distribution line faults, and then take effective preventive measures to ensure the safe operation of distribution lines. Distribution line fault tripping is closely related to seasonal changes. Line operators and safety managers shall actively pay attention to local weather forecast. Analyze short-term and historical meteorological data and take preventive measures in advance. Upgrading some lines and improving line operation and maintenance level is an important guarantee to reduce distribution line fault tripping.