What is the difference between European box transformers and American box transformers?
05-31 2025 | By:
The box transformer is a facility that integrates high and low voltage primary equipment, transformers, and secondary equipment in a double-layer, sealed, corrosion-resistant, and movable outdoor box in the factory. The full name of the box transformer is the box-type substation, which is a box-type power equipment that combines power transformers and high and low voltage distribution devices in one or several cabinets and can be hoisted and transported. Due to its compact structure, neat appearance, convenient mobile installation, and low maintenance, it is widely used in the construction of power grids in railways, factories, and cities. The mainstream box transformers are divided into European box transformers and American box transformers. Below ZTELEC Yuguang ElectricTechnology(Henan)CO.，Ltd. briefly distinguishes between European box transformers and American box transformers
1. What is the difference between European box transformers and American box transformers?
500 kVA Padmount Transformers
Box transformers (abbreviated as box transformers) are generally composed of high-voltage rooms, transformer rooms, and low-voltage rooms. According to different product structures and different components used, they are divided into two typical styles: European box transformers and American box transformers.
Since the late 1970s, my country has introduced and imitated box-type substations from France, Germany and other countries. The structure adopts high and low voltage switch cabinets and transformers. This box-type substation is called European box-type substation, which is figuratively like building a house for high and low voltage switch cabinets and transformers.
European box-type substation
Since the 1990s, my country has introduced American box-type substations. The load switch, ring network switch and fuse structure are simplified and placed in the transformer oil tank and immersed in oil. The lightning arrester also adopts oil-immersed zinc oxide lightning arrester. The transformer eliminates the oil pillow, and the oil tank and radiator are exposed to the air. This box-type substation is called American box-type substation, which is figuratively like hanging a box next to the transformer.
American box-type substation
In terms of volume, the European box-type substation has a larger product volume due to the installation of conventional switch cabinets and transformers inside. The American box-type substation is smaller in volume due to the integrated installation.
In terms of protection, the high-voltage side of the European box-type substation adopts load switch plus current-limiting fuse protection. When a phase fuse blows, the fuse striker is used to disconnect the three phases of the load switch at the same time 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 plus a current-limiting fuse, and the high-voltage side of the American box transformer is protected by a fuse. The load switch only has the function of switching and cutting off the high-voltage load current, and the capacity is small. When a phase fuse blows on the high-voltage side, the voltage on the low-voltage side is reduced, and the undervoltage protection or overcurrent protection of the molded case automatic air switch will be activated, and low-voltage operation will not occur.
European box-type substation
From the perspective of product cost, the cost of European box transformers is high. From the perspective of product price reduction space, there is still a large price reduction space for American box transformers. On the one hand, the three-phase five-column iron core of the American box transformer can be changed to a three-phase three-column iron core. On the other hand, the high-voltage part of the American box transformer can be modified from the transformer oil tank to the outside of the oil tank, occupying the high-voltage room space.
2. System differences between European and American box transformers
2.1. American box transformers:
1) Wiring form of box transformers: one or two 10KV incoming lines; single transformer, the capacity is generally 500KVA~800KVA; 4~6 low-voltage outgoing cables
2) Main components of box transformers: transformer, 10KV ring network switch, 10KV cable plug, low-voltage pile head box and other main components.
It has the advantages of small size and low cost for installation.
2.2 Advantages and disadvantages of American box transformers
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 reduce the cost of power supply.
2) Disadvantages: Low power supply reliability; no electric mechanism, unable to add power distribution automation device; no capacitor device, which is more effective in reducing line noise than type III and type V stations; due to the different civil engineering foundations of box transformers of different capacities, the box transformer is inconvenient; when the box transformer is overloaded or the user increases the capacity, the civil engineering needs to be rebuilt, there will be a long power outage time, increasing the difficulty of the project.
2.3, European box transformer:
1) Wiring form of box transformer
a, single distribution transformer form – two 10KV incoming lines; the capacity of a single transformer is generally 500KVA~800KVA; the low-voltage outgoing cable is generally 4~6 lines.
b, two distribution transformer form – two 10KV incoming lines; two transformers, each transformer has a capacity of 500KVA~800KVA, and the line cable is generally 8~12 lines.
2) The main components of the box transformer are transformer, 10KV ring network switch cabinet, low-voltage capacitor, low-voltage switch and other main components, which is equivalent to compactly installing the equipment of the type III station in a metal box, making the type III station miniaturized. The volume of the European box transformer is higher and larger than that of the American box transformer, and the cost is also higher than that of the American box transformer.
EU substation
2.4 Advantages and disadvantages of the European box transformer:
1) Advantages: The noise is equivalent to that of the type III station and the type I station; the radiation is lower than that of the American box transformer, because the transformer of the European box transformer is placed in the metal body to play a shielding role; the distribution automation can be set up, which not only has the advantages of the type III station and the type I station, but also has the advantages of the American box transformer.
2) Disadvantages: The volume is large, which is not conducive to installation and has a certain impact on the environmental layout of the community; Second, due to the different structures of the box transformer, the places of use are also different, and the power supply network is also different. Because the structures of the American box transformer and the European box transformer are different, the reliability is different, so the applicable occasions are also different. When the capacity of the American-style box transformer is small and the building area of the community is large, the number of box transformers used will increase a lot, thereby increasing the number of load points connected to the overhead line; when the load points of the overhead line are reduced, the number of box transformers connected in series must be increased, which makes the network structure weak. To overcome the problem of small-capacity box transformers and weak network structure, it is best to use a ring network station to solve it.
2.5 Summary and analysis
1. Applicable places for American-style box transformers In view of the structural characteristics and advantages and disadvantages of American-style box transformers, American-style box transformers are suitable for multi-story residential buildings and other unimportant buildings with relatively low power supply requirements. According to our actual use, American-style box transformers are fully suitable for the power needs of multi-story residential buildings after being equipped with a small ring network switch station. Because even if the box transformer fails, it will not have much impact on residents, but it is not suitable for small and high-rise buildings.
2. Applicable places for European-style box transformers European-style box transformers are suitable for multi-story residential buildings, small and high-rise buildings, high-rise buildings and other more important buildings.
3. Development direction of box transformers
Both American box transformers and European box transformers have various shortcomings, but with the advancement of science and technology, distribution automation,
capacitor compensation and other new technologies are constantly applied to box transformers, and box transformers will definitely be the preferred solution in the power supply mode.
ZTELEC Yuguang ElectricTechnology(Henan)CO.，Ltd. designs and produces European box transformers using imported high-quality cold-rolled silicon steel sheets stacked and Y/Yn connection methods, with reasonable structure, good performance, high efficiency and low noise. The primary and secondary coils are well insulated and isolated to protect the secondary circuit from interference from the power grid and external high-frequency electromagnetic waves. Welcome to call for consultation.
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