Distribution network; Fault; Lightning accident; Operational hidden danger
Foreword:
Starting with the analysis of common distribution network faults, we can improve the understanding of faults, give full play to people's role and avoid line damage. Only by finding out the cause of the accident can we better implement the control of distribution network, improve the quality and efficiency of line use, improve the utilization rate of distribution network lines and strengthen the operation and maintenance of distribution network.
1 common 10kV distribution network accidents and their causes analysis.
1. 1 Lightning strike fault and its causes
The most common distribution network accident is lightning strike. Take 10kv distribution network as an example for analysis. Due to the overhead erection of 10kV lines, the erection path is long, mostly in open areas, and there are few high-rise buildings around the distribution network. Therefore, it is easier to be struck by lightning in thunderstorm season every year, which is one of the common faults of 10kv overhead lines. Common fault phenomena, such as disconnection, burning of distribution transformer, bursting or breakdown of insulator, etc.
Because of the hidden dangers and poor quality of insulators. Especially, the P- 15kV pin insulator has serious quality defects, which can easily lead to the indirect short circuit or grounding of the 10kV line when it is struck by lightning.
10kV line lacks lightning protection measures. Erecting lines in open areas is easy to cause lightning strikes. Usually, 10kV lines are rarely equipped with lightning wires, and inductive lightning or direct lightning are all looking for the weakness of line facilities, thus causing line damage.
Lightning arrester in distribution network fails or its performance declines. And because some users have not realized the importance of lightning arresters to distribution lines, the power supply department does not cooperate well with the prescribed pre-test, and often encounter some cases in which the discharge capacity, withstand voltage capacity or model of lightning arresters are unqualified. Unqualified prefecture level, due to the long-term lack of maintenance of the distribution grounding device and serious corrosion of the underground connection part, the grounding resistance value can not meet the established requirements, and the discharge ability of the distribution network is poor, which leads to the decrease of lightning current flowing into the earth and the high residual voltage of the line. The circuit damage accident caused by external force makes the circuit equipment obsolete, and some functions of the equipment deteriorate after long-term use.
1.2 Faults and Causes of Drop Fuses
There are four kinds of failures of drop fuse, such as accidental drop of fuse, poor operation, burning tube and accidental melting of melt. These failures are all caused by poor equipment, but they are also different. For example, the main reasons for the poor operation of welded pipes are poor assembly, mechanical corrosion or jamming, and interface melting scar; The reason why the fuse tube falls down by mistake is that the fuse tube itself is of poor quality and poor assembly, and it will fall down when it encounters strong wind, or the spring pressure of the contact above the fuse is insufficient, and the right-angle protrusion in the duckbill is worn or burned out. Another reason is that the fuse tube is not closed tightly when working.
2 Take accident protection measures
2. 1 lightning protection measures
The first lightning protection measure we took was to install and replace the porcelain cross arm or insulator with higher withstand voltage grade on the distribution network line. Lightning strike accidents are common in 10kv overhead pin-type lines, especially in areas with long lightning period and more thunderstorm days such as South China, and the quality of pin-type insulators is unqualified. In view of this phenomenon, we can properly use insulators with 20kV voltage level on distribution lines to improve the lightning withstand level of the lines.
We can install metal oxide surge arresters on distribution lines. For example, lightning arresters should be installed on 10kv lines, and lightning arresters should also be installed on post switches, distribution transformers and cable heads of distribution networks. The old FS- 10 valve-type or silicon carbide magnetic blow lightning arresters should be eliminated and replaced with new ones.
Rectify and inspect the grounding device. Regularly and strictly check and measure the 10kv distribution network to ensure the practicability of grounding resistance, and rectify the unqualified resistance to keep the grounding resistance within 10ω.
Correctly configure SF6 circuit breaker. The action current should be set correctly, and the circuit breaker model with delayed action time should be adopted. At the same time, we should pay attention to the different delay before and after the circuit breaker, forming a level difference. This can reduce the tripping times of instantaneous impulse current, avoid the phenomenon that circuit breakers act in different positions at the same time, and narrow the power outage range as much as possible.
2.2 Take measures to prevent external damage.
To prevent external force collision, reduce or eliminate the collision between vehicles and towers, paint striking reflective paint on the towers of traffic roads, and hang red and white reflective sign tubes on the stay wires of towers to fully attract the attention of drivers.
Strengthen the publicity and education of distribution network faults and set up eye-catching danger signs near high-voltage poles. High-voltage lines with key expenditures are prohibited from illegal construction and flying kites, suggesting some behaviors that seriously endanger personal safety. Constantly strengthen the crackdown on stolen equipment and distribution network line equipment.
It is necessary to regularly inspect the cable foundation, illegal buildings and tower foundation of the operation department 10kv line to ensure the normal operation of all kinds of equipment, ensure the timely maintenance and treatment of defective equipment, and timely rectify and clean up illegal buildings.
The signs of underground cables have been further improved. For dangerous areas, we can make or paste some signs and warning signs, which must have the words "high voltage danger of power cables" clearly and conspicuously, and always be installed on the ground along the cables.
2.3 Fail-proof Measures for Drop Fuses
In view of the above four kinds of falling fuse failures, preventive measures should be taken according to their different reasons. We can take the following measures: reassemble the melt, apply lubricating oil, remove rust, file the scar, and replace the parts if it is serious. Re-adjust the fuse tube when it falls by mistake, and replace the spring, duckbill or fuse in time. After the fuse tube is closed, make sure it is closed in place and pull the operating ring several times.
Operation, Maintenance and Management of 3 10kv Line
First of all, in the operation of 10kv line, we should always pay attention to the feeder compliance, so as to adjust the overloaded feeder in time, prohibit the overload operation of the line and ensure the service life of the line.
Secondly, the configuration and installation of high and low voltage fuses in the operation of distribution transformers are carried out in strict accordance with the rated capacity to ensure the timely development of line load measurement, so as to take timely countermeasures and implement capacity expansion and load balance adjustment.
Thirdly, in order to improve the wire contact, we should start with the construction technology of the installation link, carry out the construction in strict accordance with the specified requirements, strictly control the quality, and conduct regular operation inspection and maintenance.
Finally, in order to find faults in time, eliminate potential safety hazards and reduce fault losses. We can install short circuit fault indicator on 10kV line. Even if the 10kV line is short-circuited, the short-circuit fault indicator can quickly cut off the fault, which ensures the safety of the line to a certain extent, improves the safety factor of the distribution network and prolongs the service life of the line.
4 Conclusion:
Because the distribution network is an important link between users and the power system, and its operating environment is quite complex, its own operating safety level will directly affect the economic benefits of power enterprises. Therefore, we must pay more attention to the safe operation of the distribution network, strengthen the safe operation management of the distribution network, ensure that it has high economic and technical indicators, enhance the power supply capacity of the power grid, and increase social satisfaction. In this paper, the common faults of distribution network are analyzed, and their root causes are explored, so as to help find and solve faults in time, prevent and eliminate faults as soon as possible, minimize fault losses and realize the normal and safe operation of distribution network system.
References:
[1] Xu Layuan; Pang Lacheng; Chen Caifeng. Present situation and development of distribution automation equipment in China [J]; Electric power equipment; 200 1 03
[2] Huang Zhu. Several problems that should be paid attention to in live working of distribution lines [a]; Proceedings of the 2005 annual meeting of the seminar on transmission and distribution technology of electrical (electrical) engineering society in six provinces and one city in East China [c]; In 2005
[3] Chen, technical questions and answers on the operation and use of power equipment [M]. Beijing. China Water Conservancy and Hydropower Press. 2002
Author's resume:
Liu Yushi, male, born in 1990, is currently studying in the School of Power Electronics Engineering, North China Electric Power University.