Thinking about Application of Vacuum Circuit Breaker

Thinking of the Application of Air Circuit Breaker Li Weiping Shaanxi Provincial Local Electric Power Group has the advantages of strength, long electrical life, convenient on-site maintenance, and high technical content. In the basic construction of electric power system and non-oiling transformation, the voltage level of 40.5kV and below is open. Broken equipment selection, and is widely used as the preferred equipment for the selection of high-voltage circuit breakers. The development and application of any new product or new technology is not foolproof, there will inevitably be a shortcoming, and there will be a gradual improvement process. The universal application of vacuum circuit breakers should be treated with caution and reasonable choices for certain problems to ensure the safe operation of the power system.

\ Division 1 problem in the application of vacuum circuit breakers. At present, in the advertisement of vacuum circuit breakers, product samples, and instruction manuals, the term “maintenance-free” is generally referred to. In fact, this is unrealistic. High-voltage vacuum circuit breakers are equipped with a relatively good quality vacuum interrupter, their electrical performance and mechanical performance are significantly improved, on-site installation, maintenance is relatively simple, but it is absolutely not "maintenance-free." Each type of vacuum circuit breaker is composed of hundreds of components in terms of its structure. The manufacturing plant of these components may only design and process some of its components, and a considerable portion of it depends on external cooperation. . The selection of materials, fixtures, processes, and inspections of these parts are all related to the electrical and mechanical properties of the entire product. Therefore, the “maintenance-free” formulation is not proper and the application of vacuum circuit breakers is “misleading”. ". According to the requirements of the standard, it should be more appropriate to “small maintenance” and “long maintenance cycle”.

Mechanical life. Mechanical life is the main assessment index of the product quality of high voltage vacuum circuit breakers. According to relevant data, the National High-voltage Electrical Appliance Quality Inspection Center conducted 6.3%, 91.3%, 58.8%, 60-, 57.1-, and 78.6- for high-voltage vacuum circuit breakers made in China, which is worrying. One of the major problems is that the mechanical life does not meet the requirements of the company's standards, and the main parameters of the mechanical properties also exceed the product specifications.

Usually a high-voltage circuit breaker is composed of hundreds of parts, and the machining and process defects of each part and the interlocking linking of the parts will directly affect the mechanical characteristics of the high-voltage circuit breaker. At the same time, most of the auxiliary switches, micro switches, speed reducers, and connection terminals that are provided with the operating mechanism are outsourcing parts. There is a certain degree of dispersion and the quality is difficult to reach 100%. These problems directly affect the vacuum. The main factor of mechanical life of circuit breakers. Some vacuum circuit breakers have a nominal life of 30,000 times, and some even reach 60,000 or 100,000 times. Such publicity is doubtful. Is the current domestic vacuum interrupter and its associated components able to pass through? Does the product's true mechanical life test pass? Therefore, in the selection of high voltage vacuum circuit breakers, it is not appropriate to believe that the product specification is inaccurate. Based on the actual test report, if it can safely and reliably operate 20,000 times, it is enough to meet the application requirements of the operation site.

Fracture power frequency withstand voltage. At present, on-line monitoring of the arc-extinguishing chamber vacuum degree in vacuum circuit breakers still has no mature technical means. Many research institutes are still in the research and development stage for the on-line monitoring of vacuum interrupter vacuum degree. In practical applications, the arc extinguishing chamber should be used. The regular power frequency withstand voltage of the fracture is used as the judgment basis for the strength of the insulating medium between the fractures of the vacuum circuit breaker. The decrease of the vacuum degree of the arc-extinguishing chamber may cause a discharge breakdown between the dynamic and static contacts when the circuit breaker is opened, which seriously threatens the safe operation of the high-voltage vacuum circuit breaker. Therefore, in the vacuum circuit breaker repair process specification, the cycle and the standard of the power frequency withstand voltage test for the vacuum circuit breaker arc extinguish chamber are clearly defined, and attention must be given to the application in the application of the vacuum circuit breaker. It is not advisable to rely on misleading suggestions from certain manufacturers.

Selection of rated current value and rated short-circuit current value. The choice of the rated current value and the rated short-circuit breaking current value should be based on the actual capacity of the power grid, and the tendency to overcome the value of the insurance factor as large as possible is better. Excessive values ​​not only result in a situation in which the large horse-drawn cart is extremely uneconomical, but also affects the small inductive or capacitive current performance of the opening and closing, resulting in the occurrence of a cut-off overvoltage. According to relevant reports, the rated current of the 10kV power grid in operation in China is about 93.1% of the total number of feeders at and below 2000A. Therefore, the selection of the rated operating current should be based on 2000A and below. The selection of the maximum short-circuit current value should be based on the 16kA of 10kV and 16kA of 35kV given in the document "Guidelines for Urban Network Planning and Renovation * 1993, No. 228", and it is advisable to blindly pursue an excessively large insurance factor.

Use ambient temperature. The ambient temperature of high-voltage vacuum circuit breakers is nominally -304 to +404. In actual use, when the ambient air temperature is low, the friction force of the circuit breaker transmission mechanism is significantly increased, and the circuit breaker is divided into normal temperature conditions. The closing and closing operation force apparently cannot meet the frictional requirements of the mechanism when the low temperature is overcome, resulting in the inability to place the closing and closing. If you break or close the short-circuit fault current at this time, there will be an abnormality or even an explosion. Therefore, for the use of environmental temperature specified in the product specification in the special use of the scene, should be chasing -1A switch cabinet should pay attention to the problem of reform Wang Hongbin Ningxia Yinnan Power Supply Bureau (751100) proposed solutions.

1 The origin of the problem The vacuum circuit breakers that can be installed in the GG-1A switch and are equipped with CD10 type actuators are of many types. Their principles are similar and their performance is similar. When replacing the circuit breaker, each user unit is used to removing the original SNi-10 low oil circuit breaker and installing a vacuum circuit breaker. The CDd type operating mechanism is left intact, and the length of the vertical pull rod is slightly modified to enable vacuum. The circuit breaker is divided and operated, and the contact distance and overtravel can be adjusted. It is considered that the replacement of the circuit breaker is completed.

In fact, the circuit breaker replacement work is not as simple as described above. If the replacement is not thorough, vacuum circuit breakers will cause problems such as rejection, rejection, burn-in and turn-off coils, and relay protection circuit equipment. Therefore, the cooperation of the vacuum circuit breaker and the original CDd type operating mechanism requires installation and commissioning and testing by professional technicians with strong working experience at the site to ensure that the vacuum circuit breaker equipped with the CDd type operating mechanism can be changed. reliability.

2 Analysis of Causes The following analysis is based on the most representative ZN/0-10 type vacuum circuit breakers equipped with CDd type actuators.

The lower limit of the ambient temperature is used for the test of the closing speed and the closing speed. After passing the verification, the test is approved and must not be followed blindly.

Insulation faults still rank first in vacuum switchgear. According to relevant reports, a total of 398 insulation faults occurred in China's high-voltage switchgear from 1998 to 2002, of which 6 to 35 kV insulation faults totaled 300 times, accounting for 75.4% of the total insulation faults. Insulation faults occurred in high-voltage switchgears of 6 to 35 kV. Insulation faults of vacuum switchgears totaled 138 times, accounting for 46% of insulation faults, and still mostly occupied. Therefore, the manufacturing department must conscientiously implement a comprehensive quality management system, improve the level of technology, ensure assembly quality, and provide qualified products and spare parts. The operating department shall strengthen the usual maintenance inspections, discover hidden dangers, promptly eliminate defects, strictly implement pre-test procedures, ensure that inspections are in place, ensure the quality of the test, improve the health of the equipment, and must not take lightly the vacuum switchgear in operation.

Auxiliary switch problem. The failure of the auxiliary switch will not only cause system power failure and expand the scope of the accident, but also may cause damage to the closing and closing coils, and even cause equipment damage or personal injury. For this reason, the relevant higher authorities have held special discussions on the auxiliary switch. The analysis and verification meeting determined that the traditional auxiliary switch lip-type plug-in structure is a butt-sliding type structure.

Analysis of failure statistics, in the case of faulty cabinet failure, the burn-in of the closing and closing coils was 76 times, and the auxiliary switch failed 35 times, accounting for 55% of the malfunctions. It can be seen that the auxiliary switch did not convert properly, corrosion, disconnection, moisture, and wiring. Loose terminals are still problems that cannot be ignored in the operation and maintenance of high-voltage switchgear. Vacuum circuit breakers are no exception, maintenance must be in place, it is better to use docking sliding auxiliary switch.

2 Application prospects of vacuum circuit breaker With the rapid development of computer technology, electronic technology, communication technology and sensor technology, vacuum circuit breakers have been widely used in the power industry, the level of intelligence of high-voltage switchgear equipment is increasing day by day, vacuum circuit breakers in products During the manufacturing process, product design should be continuously improved, the level of manufacturing process should be improved, the quality of assembly should be ensured, and the reliability of equipment operation should be improved. High-voltage vacuum circuit breakers have played a positive role in promoting smart selection, optimizing equipment condition maintenance, lowering operation and maintenance costs, accelerating automation of power systems, and establishing a scientific and rational state assessment system. The application prospects are relatively optimistic.

Tensioner Pulley

Guangzhou Taixin Auto parts Trading Co., Ltd. , https://www.taixinautoparts.com