Analysis of Causes of Low Voltage Circuit Breaker Accidents and Market Development
Solidal Cable And Stranded Concentric Cable-IEC60502-1 Solidal Cable And Stranded Concentric Cable-Iec60502-1,Solidal Cable,Concentric Service Cable,Solidal Concentric Cable HENAN QIFAN ELECTRIC CO., LTD. , https://www.hnqifancable.com
Second, the development of China's low-voltage circuit breaker production enterprises China's low-voltage circuit breaker industry since 1949, on the basis of some repair, assembly of simple electrical plants, gradually developed into an independent design and production of the industry, by 1979 a total of 600 manufacturers Many, after 1985-1986, 1990-1991 two development peaks, in 1995 the low-voltage circuit breaker industry has about 1,500 production enterprises. At present, China's low-voltage circuit breaker manufacturing enterprises are mainly concentrated in Beijing, Tianjin, Liaoning, Shanghai, Jiangsu, Zhejiang, Guangdong and other places. At present, about 70% of China's low-voltage circuit breaker production has been concentrated in Zhejiang. Due to historical reasons, Zhejiang has produced counterfeit and shoddy products and imitated brands. Now it has moved to formal production, group production and brand production. Nowadays, the national low-voltage circuit breaker production base has been formed, and the products have not only spread all over the country but also entered the international market.
While promoting the development of the national economy, these enterprises have also exposed many problems. There are two main points: First, the scale of the enterprise is too small, and the number is too large. At present, among the low-voltage circuit breaker manufacturers in China, only 2-4 large-scale enterprises with annual sales income and total assets of more than 500 million yuan are the largest. Most of them are small and medium-sized enterprises, which lead to the lack of economies of scale and competitiveness. Moreover, China’s low-voltage circuit breaker manufacturing enterprises have grown from the early days of the founding of the People’s Republic of China to more than 1,500 today. The number of enterprises is too large, resulting in excessive economic resources and lack of overall innovation. Lead to low production efficiency, economic efficiency and market competitiveness. Second, the regional structure is converging and the repeated construction is serious; the low-voltage circuit breaker industry is seriously blinded by projects and paving, and the regional industry is becoming more and more assimilated. The low-level redundant construction leads to overproduction of products, low utilization of energy and raw materials, and low economic efficiency. Regional protection, vicious competition and other consequences.
Third, how to choose low-voltage circuit breaker limit short-circuit one is selected depends on the circuit breaker breaking capacity and short-circuit breaking capacity, equivalent to the International Electrotechnical Commission IEC of GB4048.2 "low-voltage switchgear and control IEC947-2 and our country Equipment Low-voltage circuit breakers are standard, and the ultimate short-circuit breaking capacity and short-circuit breaking capacity of the circuit breaker are clearly defined.
The second is to look at the clearance and creepage distance of the selected circuit breaker, determine the electrical clearance of the electrical products, must be based on the insulation of the low-voltage system, and the insulation coordination is based on the instantaneous overvoltage is limited to the specified impulse withstand voltage The instantaneous overvoltage generated by the electrical appliances or equipment in the system must also be lower than the impulse voltage specified by the power system. therefore:
(1) The rated insulation voltage of the electrical appliance should be ≥ the rated voltage of the power supply system (2) The rated impulse withstand voltage of the electrical appliance should be ≥ the rated impulse withstand voltage of the power supply system (3) The transient overvoltage generated by the electrical appliance should be ≤ the power system Rated impulse withstand voltage IV. Analysis of the cause of the accident of the circuit breaker The accident statistics of the circuit breaker for many years on the site indicate that the main types of operational accidents are as follows:
(1) Operational failure;
(2) insulation failure;
(3) Poor opening and closing performance;
(4) Poor electrical conductivity.
The causes of accidents can generally be broadly divided into two major categories: technical reasons and work reasons. The so-called technical reasons refer to the defects of the product itself or the mode of operation; the so-called work reasons refer to the fault of the workers who caused these defects. The following is a brief analysis of the reasons for these two aspects.
The first aspect: analysis of the technical reasons of the accident (1) failure of the operation failure is manifested as dragging or malfunctioning of the circuit breaker. Since the most basic and important function of the high voltage circuit breaker is to operate correctly and quickly remove the grid fault. If the circuit breaker is dragged or misplaced, it will pose a serious threat to the power grid. The main reasons are: 1) to expand the scope of the accident, which may cause only one loop fault to be expanded to the entire busbar, or even the entire plant, the whole plant power outage; The fault removal time will affect the stability of the system and increase the damage of the controlled equipment; 3 cause non-full phase operation. The result is often caused by abnormal operation of the grid protection and oscillation, which is easily expanded into a system accident or a large-scale blackout.
The main reasons for the malfunction are:
(1) Operating mechanism defects;
(2) Mechanical defects of the circuit breaker body;
(3) Operation (control) power supply defects.
(2) Insulation accidents Circuit breaker insulation accidents can be classified into internal insulation accidents and external insulation accidents. The damage caused by internal insulation accidents is usually greater than the external insulation.
1. Insulation accidents in internal insulation accidents mainly include casing and current transformer accidents, mainly due to ingress of water and moisture; followed by deterioration of oil quality and insufficient oil.
2. External insulation accidents External insulation accidents are mainly caused by flashovers and explosions caused by flashovers and lightning strikes. The main reason for the pollution flash is that the leakage distance of the porcelain bottle is small and it is not suitable for use in the dirty area. Secondly, the circuit breaker seeps oil and oil leakage, which makes the porcelain skirt easily accumulate pollution and cause flashover.