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URBAN CONSTRUCTION APPLICATION

2022-07-06210 have been browsing

10kV outdoor vacuum circuit breakers are mainly used in urban power supply lines as segmental protection, reducing the power supply radius and improving the reliability of power supply. my country’s urban network transformation has just started, and large-scale use has not yet begun. In addition to funding issues, the selection and trial of circuit breakers, as well as the determination of the mode and method of urban network automation control are the main keys. In the urban network automatic power distribution system, high-end products may be applied in batches. However, for many urban power grids, it is impossible to use automated networks on the line, so ZW1-10 type products will be widely used.

 

At present, the number of cities in my country is about 666, and there are 221 cities above the prefecture level. Through comprehensive analysis of information, the urban network needs more than 150,000 outdoor circuit breakers.

 

Due to the obvious lack of short-circuit current breaking capacity of DW5 and other types of outdoor column oil circuit breakers, and lessons that are easy to cause accidents, they are gradually eliminated in the transformation of urban (agricultural) power grids; outdoor column vacuum circuit breakers and SF6 circuit breakers It is the basic product selected by the user. The above two circuit breakers with completely different insulating media and arc extinguishing principles show their respective advantages and disadvantages in actual operation. The objective characteristics of the product itself and the special requirements of the materials used in the production process make the vacuum circuit breaker more popular. This is due to the improvement of the vacuum technology level and the technological progress of the production plant, which also contains the increasing confidence of the majority of users in the vacuum switch.

 

The worldwide debate on vacuum and SF6 switches in the 1970s continues today, but the content of the debate has changed. The debate that year promoted the development of vacuum circuit breakers. For example, the use of CuCr contact material and longitudinal magnetic field to increase the breaking current makes a great breakthrough in the breaking capacity of the vacuum circuit breaker; the use of low overvoltage contact material reduces the overvoltage, and the current cutoff level is reduced to 1/10 of the conventional value. ; Reduce the number of parts and improve reliability; reduce the size and manufacturing cost of vacuum interrupters, and miniaturized vacuum interrupters have appeared. As a result, some of the important arguments of the 1970s debate also ceased to exist with the passage of time and the development of vacuum technology, with a large number of vacuum circuit breakers entering the grid. For example, by 1978 in Japan, all 250,000 oil-on-pillar circuit breakers were replaced with vacuum circuit breakers on the column; in the late 1980s, the market share of British vacuum circuit breakers was about 50%, and SF6 accounted for 20%; according to EEC (Community) statistics, In the medium voltage market in the early 1990s, the sales ratio of SF6 and vacuum circuit breakers was 2:3; in recent years, the market share of vacuum circuit breakers in my country was even better than that of SF6 circuit breakers; Among all kinds of 10kV circuit breakers, SF6 circuit breakers account for 4.78%, and vacuum circuit breakers account for 64.93%. In 1997, SF6 circuit breakers accounted for 6.34% (about 6,000 units), and vacuum circuit breakers accounted for 70.79% (about 50,000 units). The market share and sales growth rate of vacuum circuit breakers increased simultaneously.

 

With the current level of technology, the fracture resistance with a vacuum gap of 1mm can reach 50kV. In the 1980s, Japan began to produce 145kV single-fracture arc-extinguishing chambers with a breaking current of 31.5kA. The breaking current of its 84kV vacuum circuit breaker is increased to 50kA.

 

The results of the debate that year promoted the improvement of the level of the two technologies, because both technologies have issues that need to be overcome. For example, the current cut-off problem of vacuum circuit breakers also exists in SF6 switches at the same time. Siemens experts have pointed out that the overvoltage generated by SF6 circuit breakers when breaking no-load transformers is even higher than that of vacuum circuit breakers.

 

To solve the problem of overvoltage during the operation of vacuum circuit breakers, RC protection devices or metal oxide arresters are widely used in China as overvoltage protection for vacuum circuit breakers, but there are still a few overvoltage phenomena that cause electrical equipment to be overvoltage. destroy. According to the analysis, most of the reasons are the improper use and coordination of these protective devices. If the selection or parameters are properly coordinated, the problem can be solved.