After several years of large-scale rural power grid transformation, rural power distribution lines have been completely renewed, and the distribution network failure rate has been greatly reduced. However, due to many reasons, the rural 10kV distribution network failure rate still accounts for a considerable proportion of power grid failures. Proportion. According to the current relevant provisions in the "Standards and Assessment Rules for Building First-Class County-Level Power Supply Enterprises", the power supply reliability rate of rural power distribution systems is required to reach 99.4%. Therefore, in order to improve the level of modernization of the distribution network of rural power supply enterprises, in addition to actively preventing distribution In addition to the occurrence of network failures, the key point is to race against time to complete the fault repair work when the 10kV rural distribution network fails, so as to achieve the power supply reliability index. Therefore, the efficient and satisfactory completion of distribution network fault repair work not only plays a decisive role in improving the reliability of distribution network power supply, but also reflects the company's high-quality service level to a large extent. So, how can we improve the efficiency of rural 10kV distribution network fault repair? 1. The first prerequisite for completing emergency repair work. At present, most rural 10kV distribution networks still use radial networks. Compared with dual power supplies, multiple power supplies and ring network power supply lines, it is easier to locate the nature and scope of faults, so the efficiency of emergency repairs is improved. , there is great potential that can be tapped. (1) Directly locate the fault point according to the user’s repair phone number. When receiving a repair call from the user, the user should be asked about the general situation of the fault point so that the repair personnel can bring the corresponding repair tools and materials. In addition, it is best to leave the user's phone number so that you can contact the user in time if there is an unknown situation during on-site repairs. (2) Based on the action type and characteristics of the power-off protection device, roughly locate the nature and scope of the fault, so as to provide a basis for "prescribing the right medicine" for emergency repair work in advance: ① Differential protection and gas protection actions. Differential and gas protection actions are generally caused by internal faults in the substation. The specific situation should depend on the action of the high-voltage side circuit breaker and its protective device of the substation. ②The current quick-break protection tripped. The current quick-break protection range is the largest when a short circuit occurs in the maximum operating mode of the system, accounting for about 50% of the total length of the line. When the line is in the minimum operating mode, the protection range is the smallest, accounting for about 15% to 20% of the total length of the line. Therefore, if the current quick-break protection device trips, it means that the fault point is usually located in the front section of the line (nearest the substation side). ③The overcurrent protection device trips. The protection range of the overcurrent protection device is 100% of the protected line. However, usually the overcurrent protection device is also equipped with a time delay relay. When used in conjunction with the quick-break protection device, the trip is usually triggered when a fault occurs in the rear section of the line. ④ Current quick-break protection and over-current protection trip at the same time. This situation generally indicates that the fault point is located in the fair range of quick-break protection and over-current protection, and the fault point is mostly located in the middle section of the line. ⑤The distance protection device trips. The tripping of the distance protection device is generally caused by a short circuit between lines. One section of the protection range is 80% to 85% of the entire length of the line (calculated from the power point). The second-stage protection not only protects the end of this section of the line and the next section of line, but also takes into account the backup protection of the first-stage protection. ⑥A grounding signal occurs during line insulation monitoring (the neutral point is not directly grounded in the distribution network). The occurrence of a ground signal in line insulation monitoring generally indicates that the line has a single-phase grounding, and the line insulation monitoring range is the entire length of this section of line. (3) Install line grounding short-circuit indicators on the T-contact branches of each distribution line to assist in indicating the scope and nature of the fault. The ground short-circuit indicator is generally installed first on the T-contact branch line that is easily accessible by vehicles, followed by the T-contact branch line that is easily accessible by walking, and finally other T-contact points are installed depending on the specific situation. In this way, when a fault occurs on the line, vehicles can be used as much as possible to improve the efficiency of fault inspection. Since 2001, Xiaochang Power Supply Bureau has successively installed line grounding short-circuit indicators on 247 T contacts of the 10kV rural distribution network in its jurisdiction. The operation practice of the past two years has shown that the fault range indication is relatively accurate, which facilitates the smooth completion of emergency repair work. Gain valuable time. (4) Where conditions permit, the fault recorder installed in the substation can be used to more accurately locate the nature and scope of the fault. In actual work, the above-mentioned relay protection actions, grounding short-circuit indicator actions, etc. should also be comprehensively considered according to the specific circumstances and line layout, so that dangerous fault points can be easily found. At the same time, the analysis is required to be as accurate as possible, and efforts are made to avoid misjudgments that may lead to repair vehicles and personnel going in the wrong direction. 2. Install automation equipment. Install feeder automated circuit breakers or pole-mounted circuit breakers and isolating knife switches on T-contact branch lines with a high frequency of branch line faults, so that when the line fails, the faulty branch line can be cut off as soon as possible and put into emergency repair, with the maximum Ensure that health equipment lines continue to operate safely to the maximum extent and improve power supply reliability. 3. Improve the accident emergency plan. Formulating and improving the accident emergency plan and carrying out regular accident drills are important guarantees for the excellent completion of accident repair work. (1) Carry sufficient emergency repair tools, equipment and instruments according to the fault situation to avoid "waiting for rice to finish cooking" during emergency repair work, which will affect the emergency repair efficiency. (2) Make overall arrangements for the division of labor and operating procedures of the emergency repair site personnel, so that the emergency repair work is linked to each other. This requires careful consideration and skillful drills in accident emergency plans and accident drills. 4. Benefits of accident emergency repair work Conscientiously implementing the eight-character policy of "safety first, prevention first" is the greatest benefit of accident emergency repair work.
(1) Frequently inspect lines and equipment. Especially in the early stage of the load peak, it is necessary to promptly grasp the health level of distribution lines and equipment, register equipment and lines with Class II obstacles, and arrange planned maintenance in a timely manner to eliminate defects. At the same time, it can also provide a certain basis for the analysis of dangerous points of line failure when the line fails before the defect can be eliminated in time. (2) Install line lightning arresters in areas with high lightning strike rates in distribution networks to improve the lightning resistance level and power supply reliability of distribution lines. (3) Mobilize qualified important line users to build backup power supplies, which not only reduces the pressure on emergency repairs of distribution network accidents, but also allows emergency repair personnel to use their emergency repair efforts "on the cutting edge" under high failure rates. (4) When the peak load period arrives, it is necessary to do a good job in load forecasting, and at the same time actively cooperate with the dispatching department to re-adjust the action values ??of some relevant relay protection devices in the substation to prevent the relay protection device from malfunctioning during the peak load period. The action trips the line. (5) When the speed of accident repair work conflicts with safety work, "safety first" should be chosen without hesitation, because safety is the greatest benefit. Through the above measures, the Xiaochang Power Supply Bureau's rural 10kV distribution network failure recovery time in 2002 has been controlled within 2 hours (general areas), including remote mountainous areas within 6 hours, and the rural power supply reliability reached 99.52%, which is the first time for Xiaochang County to pass Hubei The provincial electric power company's "first-class county-level power supply enterprise" acceptance has laid a solid foundation and achieved good social and economic benefits.