Development History of Box-type Substation

Box-type substation is suitable for residential district, urban public transformer, busy city, construction power supply and so on. Users can choose box-type substation according to different use conditions and load levels.Since its inception, box-type substations have developed rapidly, accounting for 70% of distribution transformers in developed countries in Europe and 90% in the United States.

For box-type substations, China has imported and copied box-type substations from France, Germany and other countries since the late 1970s. It is structurally composed of high and low voltage switchgear and transformer, which is called European box transformer, which is likened to building a house for high and low voltage switchgear and transformer.

Since the 1990s, China has introduced American box-type substations, which simplify the structure of load switches, ring network switches and fuses into transformer oil tanks and immerse them in oil.The lightning arrester also adopts oil-immersed zinc oxide arrester. The transformer removes the oil pillow, the fuel tank and the radiator are exposed to the air. This kind of box transformation is called the American box transformer, which is likened to a box hanging next to the transformer.

European box-type substation

The box body of an European-style substation is composed of a base, a shell and a top cover.The base is generally made of channel steel, angle steel, flat steel, steel plate, etc., welded or bolted to form; in order to meet the needs of ventilation, heat dissipation and in and out lines, strip holes and circular holes of moderate size should be made in the corresponding position.The box shell, top cover channel steel, angle steel, steel plate, aluminum alloy plate, colored steel plate, cement plate, etc., are bent, welded or connected with screws, hinges or related special accessories.

No matter what kind of material box-type substation shell, according to the standard it must have: sunscreen, rain, dust, rust, anti-small animals (such as snakes) entry five protection functions.In order to prevent the strong solar radiation in hot summer, the shell of European substation is generally equipped with thermal insulation material with low thermal conductivity as packing.Commonly used fillers are: rock wool board, polystyrene foam and so on.

In the traditional “combined substation” with unified design, the shell is generally filled with thermal insulation fillers, which is no longer used by most designers, because although the thermal insulation fillers can prevent strong sunlight radiation in hot summer, at the same time, it also hinders the emission of a large amount of heat from transformer operation, so the designers not only retain the method of flushing louvers on the shell. At the same time, the method of increasing the heat dissipation area and strengthening the air convection is adopted to dissipate heat, and the manufacturing cost can be reduced at the same time.The surface of the European box-type substation: there are many methods on the surface of the European box-type substation.

The traditional painting, baking and plastic spraying methods are mostly used in northern China; in the economically developed areas of southern China, in addition to the above-mentioned methods, color ceramic tiles or veneers are also pasted on the shell of the cement plate structure for surface treatment. In particular, the appearance of the boxes placed in the residential area is more coordinated and unified with the style of the local buildings.

American box-type substation

Box-type substations in China were originally developed from European-type box-type substations, and their volume is often relatively large. With the opening up of China’s foreign economy and the vigorous development of the market economy, American box-type substations entered the Chinese market in the 1990s and developed rapidly in the Chinese market with its unique characteristics.This kind of American box-type substation can be seen almost everywhere in China from south to north and from east to west, and most of them are imitated by domestic manufacturers, and their quality can be said to be uneven.

The main features of American box-type substation:

The overload capacity is strong, allowing 2 times overload for 2 hours and 1.6 times overload for 7 hours without affecting the variable life of the box.

The use of elbow plug-in connector, can be very convenient for the connection of high-voltage incoming cable, and can be used as a load switch in emergency, can be electrified and unplugged.

The double fuse protection is adopted, and the plug-in fuse (BAY-o-net) is a double-sensitive fuse (temperature and current) to protect the short-circuit fault on the secondary side of the box-type substation. The backup current limiting protection fuse (ELSP) protection box is used to protect the high voltage side. Transformers generally use high ignition point oil (FR3).

All components such as fuses for high voltage load switch protection are placed in the same fuel tank with transformer cores and windings.

JONCHN Box-type Substation

Compared with the American box-type substation, the box-type substation produced by JONCHN has added grounding switch and lightning arrester, and there is a mechanical interlock between the grounding switch and the main switch, which can ensure the absolute safety of the person during box transformer maintenance.The box-type substation produced by JONCHN adopts load switch and intelligent vacuum circuit breaker protection instead of American box transformer fuse as protection. Its biggest feature is that there is no need to replace the fuse, the vacuum circuit breaker automatically cuts off the power supply when the line fails, and the main switch circuit breaker can be closed only after troubleshooting, which is not available in the American box transformer.

The box-type substation generally adopts the structure of independent units, which are respectively equipped with transformer room, high-voltage switch room and low-voltage switch room, which are connected by wires to form a complete power supply system.

The transformer room is usually placed in the middle. In order to facilitate the needs of maintenance, replacement and capacity increase, the transformer can be easily pulled out of the box or hoisted from the upper part. Because the transformer is placed in the shell, its favorable factor is that it can not only prevent the temperature rise caused by sunlight directly shining on the transformer, but also effectively prevent external force collision, impact and touch inductive accidents; the disadvantageous factor is the higher requirements for the heat dissipation of the transformer.

​The high-voltage switchgear room is equipped with independent closed high-voltage switchgear, inflatable or vacuum load switch is installed in the cabinet, SF6 load switch is installed in the wire cabinet, and SF6 vacuum circuit breaker is installed in the outlet cabinet, which has various functions of line protection to ensure the normal operation of the circuit. In addition, it is also equipped with a grounding switch, which is interlinked with the main switch, that is, only after separating the main switch can the grounding switch be closed, and after closing the grounding switch, the main switch can not be closed, so as to ensure the safety of maintenance. The cabinet is also equipped with a high-voltage lightning arrester, the operation of the whole switch is very convenient, as long as the use of a special matching handle, all the switches can be turned on and off. At the same time, the on-off state of the main switch can be observed through the transparent window.

Low-voltage switchgear: generally low-voltage switchgear is equipped with main switch, each distribution branch switch, low-voltage lightning arrester, voltage and total current, branch current instrument display, at the same time, in order to better protect the safe operation of the transformer, measures are often taken to monitor the oil temperature in the upper layer of the transformer.

When the oil temperature reaches a dangerous temperature, it can automatically stop the low-pressure side work (disconnect the low-pressure side load), of course, its action value can be set according to the requirements.

The switchgear of the box-type substation produced by JONCHN are made into independent cabinets and installed in the shell, which can be easily replaced and maintained, and at the same time improve the protection ability and safety. Its steel plate shell is treated with special technology, so that its protection ability can reach more than 20 years. At the same time, the upper cover adopts a double-layer structure to reduce the thermal radiation of sunlight, and its appearance can be matched with a variety of colors coordinated with the use environment according to user requirements, so as to achieve the effect of embellishment with the natural environment.

The box-type substation produced by Nakagawa, more accurately, should be called European-American integrated box transformer, which is more appropriate. The appearance of the box-type substation is the same as the European-type box-type substation, and its volume is slightly smaller than that of the European-type box-type substation and larger than that of the American-type box-type substation. This is because the transformer, load switch and low voltage outlet mode of the box-type substation produced by Nakagawa are basically the same as the American box-type substation, but it has an independent transformer room. As both high and low voltage outlets are on the side wall, protective rails and other facilities are considered on both sides of the transformer room. Because of the compact structure of the box-type substation, the top cover design retains the natural ventilation cooling and cooling mode.

Application and after-sale

Box-type substation is the main direction of current rural power network transformation and substation construction in the future, but JONCHN after-sales service team will play a significant role in after-sale installation and maintenance, fire prevention, capacity expansion and other issues.

Looking forward to the future, box-type substations will be widely used in cities, rural areas, industrial and mining enterprises and public building facilities. It will be used by more and more people because of its advantages of high quality and low price, making the operation level of power grid to a new level.