How Much Do You Know About Box Transformers?
Introduction history of European style box type substations:Since the late 1970s, China has introduced and imitated box type substations from France, Germany and other countries. The structure adopts high and Low Voltage Switchgear and transformer composition. This type of box type substation is called European style box type substation, which is metaphorically referred to as building houses for high and low voltage switchgear and transformers.
Introduction history of American style box type substations: Since the 1990s, China has introduced American style box type substations, which simplify the structure of load switches, ring network switches, and fuses by immersing them in the transformer oil tank. The lightning arrester also adopts oil immersed zinc oxide lightning arrester. The transformer eliminates the oil pillow, exposing the oil tank and radiator to the air. This type of transformer is called an American transformer, which is metaphorically referred to as hanging a box next to the transformer.
Q: So what is the difference between American and European style boxers?
Answer: 1. Due to the simplified structure, the footprint and volume of the American box type substation are greatly reduced. Due to its small size and only one side opening door, its required footprint is only 1/4 of that of the European box type substation, and its volume is only 1/5 to 1/3 of that of the European box type substation with the same capacity. Meibian has the advantage of being smaller in size, which cannot be compared to Oubian.
2. From the layout perspective, the low voltage room, transformer room, and high voltage room of the American box transformer are not arranged in a zigzag pattern, but in a zigzag pattern.
3. From the perspective of product cost, European style boxes have become more expensive.
4. From a protection perspective, the high voltage side of American box type transformers adopts fuse protection, while the load switch only functions to switch and cut off the high voltage load current, with a smaller capacity. When a phase fuse is blown on the high voltage side, the voltage on the low voltage side decreases, and the undervoltage protection or overcurrent protection of the plastic shell automatic air switch will be activated, and low voltage operation will not occur.
The high voltage side of the European box transformer is protected by a load switch and a current limiting fuse. When a phase fuse is blown, use the firing pin of the fuse to simultaneously disconnect the three phases of the load switch to avoid phase loss operation. The load switch is required to have the ability to cut off the transfer current. The low-voltage side is protected by a load switch and a current limiting fuse,
1、 Specific comparison in product structure
1. American Box Transformer:
1) The wiring form of the transformer box: one or two 10KV incoming lines;
A single transformer with a capacity generally ranging from 500KVA to 800KVA; 4-6 low-voltage outgoing cables
2) The main components of the transformer are:
The main components include transformers, 10KV ring network switches, 10KV cable plugs, and low-voltage pile head boxes. It has the advantages of small size, low cost, and easy installation.
Advantages and disadvantages of American box type transformer:
1) Advantages: Small size, small footprint, easy to place, easy to disguise, and easy to coordinate with the environment of the community. It can shorten the length of low-voltage cables, reduce line losses, and also lower the cost of power supply matching.
2) Disadvantages:
1、 Due to the immersion of the load switch in oil, the oil was carbonized and decomposed by the arc, producing harmful gases such as acetylene, resulting in a decrease in performance and causing accidents. Cannot see obvious disconnection points, making maintenance inconvenient;
2、The American box transformer itself does not come with low voltage protection and metering. To meet the needs of domestic users, domestic box transformers are equipped with low-voltage distribution cabinets on the low-voltage side. Due to the prolonged exposure of the box type transformer to direct sunlight, it affects the heat dissipation of the molded case Circuit Breaker, making it unable to disconnect loads and short-circuit currents normally, which can easily lead to high-voltage side faults;
3、 The Meibian has a smaller size, and with the addition of capacitors, its heat dissipation conditions are not as good as the Oubian; After the volume of the Meibian becomes smaller, its functional expansion is not as good as that of the Oubian. Due to the different civil foundations of different capacity box transformers, it is inconvenient to increase the capacity of the box transformers. When the box transformers are overloaded or users increase capacity, the civil engineering needs to be rebuilt, which will result in a longer power outage time and increase the difficulty of the project. But European transformers can change their capacity by replacing transformers, while American transformers cannot;
4、 The high-voltage part of the Meibian transformer consists of plug-in fuses and load switches, which is not as extensive as the scheme of the Oubian transformer;
5、 European transformers can add metering for high voltage, while American transformers cannot.
2. European style box transformer:
1) Wiring form of transformer box
a 、 Single transformer form - two 10KV incoming lines;
The capacity of a single transformer is generally between 500KVA and 800KVA; Low voltage outgoing cables generally have 4-6 circuits.
b 、 Two transformer forms - two 10KV incoming lines; Two transformers, each with a capacity ranging from 500KVA to 800KKVA; Low voltage outgoing cables generally have 8-12 routes.
2) Main components of the transformer box
The main components include transformers, 10KV ring network switchgear, low-voltage capacitors, low-voltage switches, etc., which are equivalent to compactly installing the equipment of Type III stations in metal boxes, making Type III stations smaller. The volume and cost of European style box transformers are higher and larger than those of American style box transformers.
1) Advantages: The noise level is comparable to that of Type III and Type I stations; The radiation is lower than that of American box transformers because the transformers of European box transformers are placed inside a metal box to provide shielding; Distribution automation can be set up, which not only has the advantages of Type III and Type I stations, but also has the main advantages of American box type transformers.
2) Disadvantages: Large size, not conducive to installation, and has a certain impact on the environmental layout of the community;
In short, Meibian has a smaller footprint and a more reasonable design structure, which can reduce the corresponding cable length; The Euro variant has a large volume, but complete functions, and flexible expansion and modification plans.
2、 Product selection for different usage scenarios
Due to the different structures and reliability of American and European box transformers, their applicable scenarios are also different. When the capacity of American box type transformers is selected to be smaller and the building area of the community is larger, the number of box type transformers used will increase significantly, resulting in an increase in the number of load points supported on overhead lines; When reducing the support load points of overhead lines, it is necessary to increase the number of box transformers connected in series, thereby making the network structure weak. To overcome the problem of weak network structure caused by the transformation of small capacity boxes, it is best to use ring websites to solve it.
Given the structural characteristics and advantages and disadvantages of American style transformer substations, they are suitable for power consumption in multi story residential buildings and other unimportant buildings with relatively low power supply requirements. Based on our actual usage, the American style transformer with a small ring network switch station is fully suitable for the power supply needs of multi story residential buildings. Because the box type substation has malfunctioned, the impact on residents is not significant, but it is not suitable for small and high-rise buildings.
2. Application scenarios of European box transformer
European style box substations, also known as outdoor complete substations or modular substations, are widely valued for their advantages such as flexible combination, easy transportation, migration, easy installation, short construction period, low operating costs, small footprint, pollution-free, and maintenance free. In the construction (renovation) of rural power grids, it is widely used in the construction and renovation of 10-110kV small and medium-sized substations, factories, mines, and mobile operation substations in urban and rural areas. Due to its ease of penetrating into load centers, reducing power supply radius, and improving terminal voltage quality, it is particularly suitable for rural power grid renovation and is known as the target mode of substation construction in the 21st century.
3、 The Development Prospects of Box Transformation
At present, European style box transformers have been widely used in urban and industrial power grids below 22kV in foreign countries, thus changing the installation of transformers on poles and the spider web style wiring method. It has played a good role in the safe and reliable operation of the power grid, reducing substation investment, and accelerating construction speed, and is one of the new development trends of substation equipment.
In addition, the color design of the box shell can be coordinated with the usage environment, which is beneficial for beautifying the environment. Therefore, it will be widely applied in cities, rural areas, industrial and mining enterprises, and public buildings in China.