Electrical appliances with a rated voltage of 3kV and above are mainly used for breaking and closing conductive circuits. From 2007 to 2012, the total industrial output value of the high-voltage circuit breaker manufacturing industry increased year by year, with a year-on-year growth rate of more than 10%, and the industry maintained a relatively fast development speed.
1. Introduction of high voltage circuit breaker
In 2012, the industry achieved a total industrial output value of 204.709 billion yuan, a year-on-year increase of 15.74%; from 2007 to 2012, the sales revenue of the high-voltage circuit breaker manufacturing industry increased year by year, of which the sales revenue in 2011 was 172.009 billion yuan, a year-on-year increase of 18.96%; Revenue was 201.021 billion yuan, a year-on-year increase of 16.87%. Compared with 2011, the year-on-year growth rate of the industry's total industrial output value and sales revenue in 2012 both declined.
From 2007 to 2012, except for 2010, the production and sales ratios of other years were less than 100%, reflecting the oversupply of the industry. Among them, it was 99.64% in 2012, a decrease of 0.04 percentage points compared with 2011. The phenomenon is more serious. With the continuous expansion of the market size and industrial scale of the industry, the growth rate of the industry has shown a downward trend, indicating that the competition pattern of the high-voltage circuit breaker market has changed. The focus of the development of the high-voltage circuit breaker industry is to improve the production efficiency and service quality of the entire power industry. And strive to realize the diversification of products and services within its own field. That is, the industry has entered a period of strategic adjustment.
The strategic adjustment methods of the high-voltage circuit breaker industry are mainly divided into: vertical extension and horizontal expansion. Among them, vertical extension refers to the deep development of the system and quality of the industry scale, such as the innovation of high-voltage load switch equipment technology; horizontal expansion refers to focusing on high-voltage An expansion of the scale and structure of the circuit breaker industry.
1.1 Problems and reasons
Reasons why the high voltage circuit breaker cannot be closed
1.1.1 Electrical circuit failure:
Closing fuse blown or poor contact.
The DC voltage is too low.
The operating handle and the auxiliary switch are poorly connected or disconnected.
The closing coil of the contactor is short-circuited.
For the Huguan that is closed by the motor, the resistance of the closing circuit breaks or does not return after tripping.
1.1.2 Mechanical failure:
The switch body and contactor are stuck (such as SN1-10 guide tube protruding, DW2-35 lifting pin is too long, etc.).
The big shaft moves in series or the pin falls off.
The closing bracket is stuck due to excessive sludge.
The bracket has a large slope and is not straight or has a small angle.
If the three points are too high, the opening pin will not be hooked firmly.
The mechanism is stuck and has not returned to the ready-to-close position.
The closing buffer gap is small, and the overrunning stroke of the closing coil iron core is small.
1.2 Search method
When the electric closing fails, it should be judged whether it is the electrical part or the mechanical part. If the contactor does not operate, it means that the control circuit is faulty; if the contactor operates but the closing iron core does not move, it means that the main closing circuit is faulty; if the main closing iron core operates, but the neck is jammed or the mechanism is not hanging firmly The shedding phenomenon is generally a mechanical failure, and this situation is sometimes related to the electrical part. According to the above analysis and judgment, gradually narrow the scope until the cause is found out and dealt with in time.
2. Classification of high voltage circuit breakers
2.1 High voltage circuit breaker
The circuit breaker plays two roles in the power system: one is the control function, that is, according to the operation needs of the power system, put a part of the power equipment or lines into or out of operation; the other is the protection function, that is, when the power equipment or lines fail , The relay protection device acts on the circuit breaker to quickly remove the faulty part from the power system to ensure the normal operation of the non-faulty part of the power system.
There are many types of high-voltage circuit breakers, but in terms of their structure, they are composed of five basic parts: breaking elements, supporting insulators, transmission elements, bases and operating mechanisms. The breaking element is the core element of the circuit breaker, and tasks such as control and protection must be completed by it. The other components are all set up to complete the above tasks in cooperation with the breaking elements.
Circuit breakers can be divided into the following types according to the arc extinguishing medium used:
2.1.1 Oil circuit breaker: A circuit breaker that uses transformer oil as the arc-extinguishing medium is called an oil circuit breaker. For example, the oil of the circuit breaker also serves as the insulation after breaking and the insulation medium between the live part and the grounding shell, called multi-circuit breaker. Oil circuit breaker; oil is only used as the arc extinguishing medium and the insulating medium after the contact is broken, and the insulating medium between the live part and the ground uses porcelain or other medium, which is called a less oil circuit breaker. It is mainly used in all levels of voltage grids that do not require frequent operation and high-speed breaking.
2.1.2 Sulfur hexafluoride (SF6) circuit breaker: a circuit breaker that uses SF6 gas with excellent arc extinguishing performance and insulation performance as the arc extinguishing medium, called SF6 circuit breaker, and is widely used in power systems. It is suitable for occasions where frequent operation and high-speed breaking are required. In my country, it is recommended to use SF6 circuit breakers at 7.2-40.5, especially SF6 circuit breakers are almost all used above 126KV. But not for high altitude areas.
2.1.3 Vacuum circuit breaker: A circuit breaker that uses the high dielectric strength of vacuum to extinguish the arc, called a vacuum circuit breaker, has been widely used in the power supply (distribution) network of 7.2-40.5KV voltage level and is mainly used for frequent Operation and occasions requiring high-speed breaking, but when used in seaside areas, attention should be paid to anti-condensation, because it will reduce the arc-extinguishing capacity of the circuit breaker's arc-extinguishing chamber.
The above three forms of circuit breakers are mainly used in the power system, and some old circuit breakers, such as air circuit breakers, have been phased out.
2.2 Isolation switch
The high-voltage isolating switch is mainly used to isolate the high-voltage power supply to ensure safe maintenance, so its structural feature is that it has a clearly visible disconnection gap after disconnection. Another structural feature of it is that there is no special arc extinguishing device, so it cannot be operated under load. But it allows a certain small current to be turned on and off, such as no-load transformers with excitation current not greater than 2A, no-load lines with charging capacitor current not greater than 5A, and voltage transformer circuits. The indoor isolating switches used in switchgear mainly include GN19 series, GN6 and GN9 series. The isolating switch is mainly composed of a conductive part, an insulating part, a transmission part and a base part.
2.3 High voltage load switch
The purpose of the load switch corresponds to its structural characteristics. From a structural point of view, there are two main types of load switches, one is independently installed on the wall or on the structure, and its structure is similar to an isolating switch; the other is It is installed in the high-voltage circuit breaker cabinet, especially if it uses vacuum or SF6 gas, it is closer to the circuit breaker. The purpose of the load switch is the comprehensive use of these two types of load switches.
2.3.1 When the load switch is in the disconnected position, it has an obvious disconnection point like an isolating switch, so it can play the role of electrical isolation. Necessary conditions for providing reliable power outages to equipment or lines that are out of power.
2.3.2 The load switch has a simple arc extinguishing device, so it can divide and close the load current within the rated current of the load switch itself. It can be used to divide and combine transformers and capacitor banks of a certain capacity, and distribution lines of a certain capacity. In some workshops, the transformer is far away from the circuit breaker in the high-voltage power distribution room. When there is a power failure, no obvious disconnection point can be seen in the transformer room of the workshop. A high-voltage load switch is often installed on the wall of the transformer room, which can be operated nearby. The no-load current of the transformer can also provide an obvious disconnection point to ensure the safety and reliability of power failure.
2.3.3 A load switch equipped with a high-voltage fuse can be used as a circuit breaker with limited breaking capacity. At this time, the load switch itself is used to divide and close the load current under normal conditions, and the high-voltage fuse is used to cut off the short-circuit fault current. However, most of the load switches here are vacuum type or sulfur hexafluoride type, and the entire ring network cabinet is not large in size, and the maximum capacity of the transformer can be 1250KVA.
3. Industry development of high voltage circuit breakers
3.1 Background and development
During the "Twelfth Five-Year Plan" period, China's high-voltage switchgear industry should take the opportunity of comprehensive construction of a strong smart grid and rely on UHV AC and DC transmission projects to enhance independent innovation capabilities, vigorously improve the intelligent level of switchgear, and promote environmental protection, energy saving, Emission reduction equipment; UHV power transmission technology and advanced electrical equipment and integration technology should be the key development areas, in-depth research on 1000kV UHV power transmission and key equipment and core technologies, and accelerate the complete localization of AC and DC high-voltage equipment; and through the Preliminary research on advanced electrical equipment and integration technology, and strive to make key breakthroughs in key technologies of superconducting power equipment; strive to promote industrial structure optimization and upgrading, further enhance the overall technical level and international competitiveness of the industry, and strive to realize the transformation of the high-voltage switch industry from large to strong change.
3.2 Development Trend
It is suggested that during the "Twelfth Five-Year Plan" period, large-scale backbone enterprises in the high-voltage switchgear industry should further carry out technical research on the core technology and key components of UHV switchgear, so as to realize the goal of UHV equipment based on domestic, independent research and development, and full localization. Combined with the construction of smart grid, digital substation, distribution network automation, etc., vigorously promote the intelligentization of switchgear. Since the intelligent switchgear technology is still a weak point in the industry, it is recommended to develop the easy ones first and then the difficult ones, such as: first develop the intelligent circuit breaker for the distribution network, and then develop the switchgear for the intelligent distribution network, smart grid GIS, GCB and others Smart components, etc., focus on the overall integration of switch primary equipment and secondary control and the development of interface technology. Actively carry out research in the field of switch simulation technology, research on 126-252kV GIS reliability theory system, research on voltage and current sensing technology and on-line monitoring technology of power equipment. Intensify the research and development of energy saving and environmental protection, high reliability and less (free) maintenance switchgear. Strengthen miniaturization, large capacity, common box technology and product development. Actively carry out the research and development of switches for special occasions, special switchgear and renewable energy power generation (such as wind power, etc.). Strive to carry out research and development of forward-looking and directional technologies and equipment (such as high-voltage bypass switches, superconducting switches, etc.). Continue to carry out research on UHV transmission projects, focus on the construction of ±800kV UHV DC projects, conduct in-depth research on key technical issues in system research and complete sets of equipment, and conduct research on key issues involved in the preliminary feasibility study of ±1000kV DC projects Research, focusing on the research and development of key technologies involved in the UHV DC project and the complete set of dual DC transmission engineering systems on the same tower; continue to carry out research on AC flexible power transmission engineering systems and complete sets of technologies; Super, UHV DC project construction, etc. At the same time, in the field of testing and testing technology, continue to carry out industry testing and testing technology research, and further expand testing service business. The focus is to further improve and improve the test and detection technology of AC and DC UHV equipment; carry out short-circuit test methods for large generators, ±800kV DC converter valve operation test technology, UHV DC converter valve insulation test technology, special environmental test technology, Research on anti-seismic performance test technology of high-voltage electrical equipment, reliability test technology of switchgear, and test technology of intelligent power equipment.