Keywords: rural distribution network; reliability
Foshan, as one of the big cities, has developed economy, and the rural 10kV distribution network is quite special. First of all, the rural industrial electricity consumption is large, and the distribution of factories is complex, which leads to the long power supply radius of 10kV line, and most of them are radial power supply or tree power supply, and there are many transformer nodes in the feeder, which leads to the high load density of the line, even reaching1/0kV feeder using * * 50 transformer. Secondly, due to the rapid economic development and relatively backward planning, there are few feeder branches in 10kV rural power grid, and almost all user transformers are connected from the main line. Finally, due to the lack of funds and backward construction of rural power grid, the load of rural power grid 10kV line is relatively large, especially in Foshan, an economically developed area, and the load rate of 10kV feeder is almost above 70%, which is not conducive to the power supply of the ring network. The above three shortcomings of rural power grid seriously restrict the improvement of power supply reliability of rural power grid. However, in any case, the main reasons that affect the reliability of power supply in 10kV distribution network can be divided into two categories: planned outage and fault outage. Taking Foshan rural power grid as an example, the ratio of planned outage to failure outage is about 60% and 40%.
The reasons for power failure are mainly divided into three categories: external damage, equipment problems and the influence of user equipment. Due to the rapid development of Foshan Chancheng and Guicheng districts, subways, highways and buildings are in the peak period, which poses a great threat to these 10kV distribution lines. However, due to the inadequate inspection management, the cable line failures caused by external damage are increasing year by year, and even in some places, external damage accounts for more than 50% of its failure rate. In addition, the influence of user equipment on reliability is also prominent, because Foshan rural power grid has a large line load, many factories, many user transformers and many access points, which has a great influence on line tripping. In this area, because the transformers in factories are generally small, they all use drop fuses and indoor FN5 load switches, and their fuse tubes are often not explosion-proof. When the transformer is overloaded or the user equipment fails, it is easy to cause the fuse tube to explode, causing instantaneous short circuit, causing line tripping and reducing reliability.
In view of the unique situation of Foshan rural power grid, Foshan Gaoming Power Supply Bureau has strengthened reliability management in recent years, paid close attention to technical equipment and management means, and summarized a series of measures to improve power supply reliability, which has achieved great results.
1. Strengthen the optimization of distribution network and realize the ring network power supply.
According to the situation of rural power grid 10kV distribution network, do a good job in network optimization, increase the power grid construction and transformation, and continuously strengthen the power grid structure. First, speed up the commissioning of new substations, add 10kV feeder lines, optimize high load rate lines, reduce line load rate, and improve the power supply foundation of ring network. Secondly, a contact switch is added at the end of the feeder to realize "hand in hand" ring network power supply. If the 10kV feeder is out of power, the power supply can be switched, especially when the head end of the line is out of power, which can greatly reduce the influence range of power outage and improve the reliability of power supply. Third, realize the reasonable increase of circuit breakers and line segmentation, and shorten the line user base. In case of planned maintenance power outage or fault power outage, open the switch closest to the fault point, and then restore the main power supply to ensure that the power outage range is reduced and the power supply reliability is improved.
2. Strengthen the management of power outage plan
, unified deployment, to achieve a total power outage.
In order to improve the technical management level in an all-round way and do a good job in planned power outage, line maintenance and fault repair, it is necessary to control the source of assessment indicators and strictly control the index data.
There are the following measures to strictly control the planned power outage indicators: First, do a good job in comprehensive power outage and power outage plan management, require a good annual plan and a good monthly plan for power outage application, so that managers can apply for unified deployment according to all plans, and the same work line can carry out comprehensive power outage to reduce unnecessary power outages. Second, strengthen the management of maintenance work.
, fully prepare for the power outage, and really make use of the maintenance work during the power outage. In addition, the maintenance process is continuously optimized, and standardized operation management is carried out according to the operation instruction.
, improve the work efficiency of the construction party, shorten the maintenance time, and finally achieve the purpose of shortening the power outage time of line users.
3. Adopt new technologies and methods to reduce the line failure rate in many ways.
There are the following measures to reduce line faults: First, strengthen the maintenance and management of equipment.
PDA, a scientific and technological means, is used to inspect the equipment regularly to ensure the reliable operation of the distribution network and low-voltage network, thus reducing the fault rate of the line. Implement the management system that all lines are responsible to people, and ensure that each line is inspected and maintained by the responsible person.
. It also plays a supervisory role for the person responsible for the trip line inspection. Secondly, increase efforts to prevent line failures caused by external damage. By patrolling the 10kV line, we can see whether there is any construction near the site. If there are signs of early construction, it is necessary to intervene in advance and notify the construction unit to pay attention to the equipment and facilities at the construction site, especially the underground laying of cables, so as to avoid line failures caused by barbaric construction. In addition, if necessary, a notice board must be erected near the corridor of 10kV line to remind the construction party that there are high-voltage cables underground to prevent cable implementation from being damaged due to negligence in construction. The contradiction that the failure of 10kV line leads to the failure of user equipment and affects the power failure of other users is more obvious in Shenzhen. Because factory transformers generally use drop switches and FN-5 load switches, and fuse tubes are often not explosion-proof, when the user transformer fails, it is easy to cause other users in the whole feeder.
Power failure reduces the reliability of rural power grid. Therefore, it is also very important to do a good job in the management of user equipment to avoid the expansion of accidents. Therefore, the power supply department needs to regularly check the users' electrical equipment, suggest users to use new technologies and equipment, and at the same time, try to ask users to replace the safety tube of the load switch as explosion-proof. At the same time, in the distribution network planning, if a new user transformer is connected to the power grid, it is required to install a circuit breaker in front of the user equipment access point. If the user equipment fails, the fault point can be disconnected first to restore the power consumption of other users, so as to improve the reliability of power supply as much as possible.
4. Actively carry out live working.
Electrical equipment needs to be tested, inspected and maintained frequently in long-term operation. Live working is an effective measure to avoid maintenance power failure and ensure normal power supply. In rural distribution network, because its 10kV lines are mostly radial and tree-shaped power supply networks, the power supply rate of its ring network is low, and its 10kV lines are mostly overhead lines. If live working is carried out, the defects of overhead lines are eliminated, and circuit breakers and switches are replaced, the effect of live working is remarkable. Especially in the economically developed areas of Foshan, there are many projects to expand or increase the capacity of customers. If each customer is newly connected to the 10kV distribution network, there will be a power outage, which will affect the power outage of the whole line and seriously reduce the reliability of power supply. Therefore, actively carrying out live working can not only improve the power supply reliability index of enterprises, but also be an indispensable and important technical means to create international advanced power supply enterprises.
Foshan is a metropolis with rapid growth from several grades. Based on its historical development, rural power grid also plays an important role. It is Foshan's urban positioning that brings new opportunities for the development of rural power, but also puts forward higher requirements. Therefore, improving the power supply reliability of rural distribution network is the need of Foshan power grid development and the special need to adapt to Foshan's economic development.