Medium voltage distribution equipment market development trend

Medium-voltage power distribution equipment is a basic device that covers a wide range of power grid systems. Due to the large amount of usage, and as a bridge for users to communicate with the main grid in the grid system, their technological development trends are also of great concern to users and manufacturing companies. With the expansion of power grids and the construction of smart grids, the technical development of medium voltage power distribution equipment presents the following new trends:

Medium-voltage distribution transformers develop medium-voltage distribution transformers for energy-saving products. This is a product with a large raw material cost. Due to the recent rapid decline in the prices of conductive, magnetic, and insulating materials, the price of products has dropped simultaneously, the output value has shrunk, and the output has increased. Slow down. Thanks to the transformation of the urban farm network and the promotion of energy conservation and consumption reduction, the medium voltage distribution transformers currently being promoted are coil core transformers. Regarding the development trend of the power distribution system in the future, the use of amorphous alloy transformers with lower losses, pre-installed substations, and combined transformers is the best way to improve the economic operation of distribution systems.

Intelligent switchgear technology needs to be broken in May of this year. State Grid Corporation of China proposed to build a strong smart grid in three phases. Building a strong smart grid requires equipment with digital, informatization, and on-line detection capabilities. At present, relay protection devices, current and voltage transformers used in medium-voltage networks are mostly based on iron-core and electromagnetic induction principles, and are non-linear measurement and protection components. The microprocessor type relay protection device, photoelectric sensor, electronic sensor, etc., are not used much or are not at a high level. Therefore, on-line inspection items with a high medium-voltage switch accident rate, such as the degree of vacuum of the vacuum switch, heat and mechanical characteristics of the busbars and external contacts, disconnection of the trip coil circuit, and partial discharge, must be truly online. A major breakthrough must be achieved in the near future.

The demand for 24 kV power distribution equipment is large because the 20 kV voltage level can replace two voltage levels of 35 kV and 10 kV at the same time, and the voltages at its upper and lower stages are matched with reasonable ones. The 20 kV distribution network has a larger distribution capacity than the 10 kV distribution network, and the transmission radius is doubled. And this voltage level has the advantages of simplifying the circuit, saving energy and reducing consumption, reducing network loss, optimizing distribution network and distribution equipment. Therefore, the 20 kV voltage transmission line has been listed in the national voltage standard of GB156-1993 and has been piloted for many years in Suzhou Singapore Industrial Park. In 2007, the State Grid Corporation officially promoted this voltage level. At present, Jiangsu, Liaoning, and Guangdong provinces have been promoting this voltage level in urban and rural areas. It is expected that they will gradually become a climate in the next two years. In the next 5 to 10 years, the market will reach 10 kV and 35 thousand. Volt quite. Following the market demand for R&D, there are currently more than 50 medium-voltage switchgear companies conducting type testing of new products with a 20 kV voltage rating. For a long period of time, the main power distribution equipment of this voltage class will have a large market. space.

The division of labor of the equipment is increasingly clear that the buck side of the high voltage substation is the head end of the medium voltage distribution network. The end of the medium-voltage network enters the user's power distribution room or control equipment. General distribution transformers of 1000 kVA and above are equipped with switching equipment called primary switching equipment. The switchgear with a distribution transformer of 1000 kVA or less is a secondary switchgear. In the past, a circuit breaker was used for switchgears, and a secondary switchgear was also used for circuit breakers. The division of work between the two was unclear and the use ratio was out of balance. The ratio of circuit breakers and load switches and contactors used in foreign medium voltage networks was 1:10. And our country is 6:1. This makes our transmission system not only high investment but also unreasonable. Can not play their respective advantages. If the circuit breaker protects the internal fault of the transformer, it is not as effective as the current limiting fuse due to the long operating time, and the frequent operating function is inferior to the high voltage contactor. Therefore, after more than ten years of efforts, the number of circuit breakers and load switches and contactors used in China is now close to 1:1, and will be further adjusted to 1:2 to 3 in the coming years.

Anti-serious pollution products have become more and more prosperous. China's environmental problems have become increasingly severe, and the influence of pollution and acid rain has further widened. According to statistics from the State Grid Corporation of China, in recent years, the accident rate of medium voltage switch insulation has accounted for more than 50% of the total failure rate. This will catalyze the birth of a new generation of switchgear that can withstand harsh environmental conditions, such as solid sealed pole vacuum circuit breakers and vulcanized coatings. The double busbar adopts silicon-rubber insulation switchgear, C-GIS equipment or indoor power distribution room with moisture-proof, dust-proof and air-conditioning functions, and devices with anti-condensation function.

The demand for miniaturization and large-capacity power distribution equipment is heating up. The process of urbanization in China is accelerating, the per capita land area is continuously shrinking, the urban land price is rapidly rising, the high-power-consumption industry is developing rapidly, and the capacity per unit area of ​​the power grid is increasing. These factors impose higher requirements on the miniaturization and large capacity of the switchgear.

In order to reduce the size of switchgears, the use of hybrid components and modular complete sets of equipment has increased year by year, and 24KV and 40.5KV C-GIS equipment have been developed. For 12 kV products, rated currents of 3150 A and 5000 A have been proposed. For large cities where the expected voltage level has not increased to 20 kilovolts, this demand will become even more urgent in the coming years.

Less maintenance, maintenance-free oil-free switches are less concerned about maintenance, maintenance-free switch is a hot topic of concern to users, with the progress of vacuum switch technology, spring mechanism process material improvements, mechanical life and electrical life is significantly improved, some manufacturers The company launched a line of useful online detection products, and also introduced a low-maintenance, maintenance-free switchgear (fool-type products) that can achieve true meaning.

The permanent magnet mechanism performance needs to improve the permanent magnet mechanism electronic control system reliability is not high enough, is still the weakness of the permanent magnet mechanism. At present, the reliability, safety, and economy of the permanent magnet mechanism still do not meet the requirements of users. Therefore, the permanent magnet mechanism needs to be further improved, especially in the outdoor column switch, electrified railway power network switch, maintenance-free switch, phase selection switch and other equipment, with small operating power, frequent operation, the permanent magnet mechanism will be promoted application.

Prefabricated switchgear stations and box-type substations are popularly installed and debug switchgear stations and substations are often subject to field conditions, such as incomplete installation of tools and equipment, and inadequate installation and commissioning experience. Therefore, in the accident statistics of the switchgear, failures caused by improper installation are still many. Now, domestic and foreign customers all require complete assembly and commissioning of the complete switchgear station and box-type substation before leaving the factory. This simplifies the on-site workload, improves work efficiency, reduces costs, reduces installation accidents, and increases the success rate of one-time operation of the equipment. Therefore, in the future, complete equipment requirements can simplify on-site installation and commissioning and increase the overall installation and commissioning of the plant. This is one of the development directions of the complete switchgear.

The development of phase-changeable closing switches has started to use conventional circuit breakers for capacitive current switching, or small inductor current switching, which can cause overvoltage problems. The use of expensive large-capacity switches, or the use of current limiters to help break the high short-circuit currents, all require expensive costs. With the development of the permanent magnet mechanism and the advancement of electronic control technology, the current industry companies have developed and produced controlled-phase opening and closing switches, which are applicable to ordinary switches for large short-circuit current breaking and small current opening and closing, and have an enlarged switching function. And there is a big potential market. However, the user's performance on controlled phase switch-off has not yet reached a high degree of recognition. Therefore, it is recommended that it be tried on a network test station before it can be used in the power industry.