What is the principle of a 35KV box transformer substation?
- 2019-05-23-

Zhejiang Yingce Electric Power Engineering Co., Ltd.'s construction projects include industries such as electromechanical, electronics, power transmission and transformation, and solar power generation. Today, we will introduce box-type substations.


Box-type substation (referred to as box-type transformer) is a compact complete set of high-voltage switchgear distribution transformers, low-voltage switchgear, power metering equipment, and reactive power compensation devices combined in one or more boxes according to a certain wiring scheme.电 装置。 Electric device. Models include 35KV and 25KV box transformers, which are suitable for use in three-phase AC systems with a rated voltage of 10 / 0.4KV for line and power distribution.

Compared with European-style box transformers of the same capacity, the structure of American-type box transformers is more reasonable. Because the European-style box transformer is a transformer and ordinary high-voltage electrical equipment are installed in the same metal shell box, the transformer's room temperature is very high, causing heat dissipation difficulties and affecting output; on the other hand, ordinary high-voltage load switches and fuses are used in the box And low-voltage switchgear, so the European-style box becomes larger. The American box transformer is different in structure from the European box transformer. From the perspective of layout, the low-voltage room, transformer room, and high-voltage room are not mesh-shaped layouts, but are character-shaped layouts. From a structural point of view, this box type is divided into front and rear parts with high and low voltage operation intervals. The operation interval includes high and low voltage terminal blocks, load switch operating handles, no-load voltage regulating section switches, and plug-in fuse The fuel tank and heat sink are at the rear. Put the transformer winding, iron core, high-voltage load switch and fuse into the transformer tank.

Lightning arresters also use oil-immersed metal oxide arresters. The transformer eliminates the oil pillow, and adopts the principle of constant volume of oil plus air gap to design a sealed fuel tank. The fuel tank and radiator are exposed to the air, and there is no difficulty in heat dissipation. Low-voltage circuit breakers use molded case circuit breakers as main circuit breakers and outgoing circuit breakers. Due to the simplified structure, the footprint and volume of this box-type substation are greatly reduced. Due to its small size and only one door opening, its required area is only 1/4 of the European-style box-type transformer, and its volume is only It is 1 / 5-1 / 3 of European-style transformer with the same capacity.

The high-voltage side of the American box transformer is protected by a fuse, and the low-voltage side is protected by a plastic case automatic air circuit breaker, which is the same as the protection mode of China's 10kV distribution transformer. The high-voltage fuse protects the internal fault of the transformer, and the automatic air circuit breaker protects the over-current, short-circuit and under-voltage faults of the low-voltage line. Disadvantages of American box change. Because the load switch is immersed in oil, the oil is carbonized and decomposed by the arc, and harmful gases such as acetylene are generated, which reduces the performance and an accident has occurred. No obvious disconnection is visible, and maintenance is inconvenient. Because the American low voltage protection and measurement method is different from China, the American box transformer itself does not have low voltage protection and measurement. In order to meet the needs of domestic users, domestic box transformers are equipped with low-voltage distribution cabinets on the low-voltage side. Since the box-type transformer is exposed to direct sunlight for a long time, the heat dissipation of the molded case circuit breaker is affected, so that the circuit breaker cannot normally open the load and short-circuit current, and it is easy to cause high-voltage side failure.

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