Development of Medium Voltage Distribution Equipment Market

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 to energy-saving products

The medium-voltage distribution transformer 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 growth has also slowed 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 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.

24 kV distribution equipment demand

Since the 20 kV voltage level can replace both voltage levels of 35 kV and 10 kV at the same time, the voltage matching between the upper and lower stages is reasonable. 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 becomes clear

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. However, our country has a ratio of 6:1. This makes our transmission system not only highly expensive 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 a decade 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.

Anti-serious environmental products are booming

The environmental problems in China 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 has been accelerating, land area per capita has continued to shrink, urban land prices have risen rapidly, and high-power-consumption industries have developed rapidly. The grid capacity per unit area has increased. 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 switch

Less maintenance and maintenance-free switches are hot topics that users are concerned about. With the advancement of vacuum switch technology, improvement of process materials for spring mechanisms, and significant improvement in mechanical life and electrical life, some manufacturers have introduced useful online detection function products. At the same time, it also introduced a low-maintenance, maintenance-free complete switchgear (fool-type product) that can achieve true meaning.

Permanent magnet mechanism performance needs to be improved

The permanent magnet mechanism electronic control system reliability is not high enough, still is the soft rib 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 and box-type substations are popular

Installation and commissioning of switching stations and substations are often limited by site conditions, such as incomplete installation of work tools and inadequate experience in installation and commissioning. 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.

Phase-controlled switch-disconnector switch starts to develop

Using conventional circuit breakers to open and close capacitor currents, or to switch off small inductor currents, can create 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.