Air Insulated Dry Type Transformer

Gas insulated transformers can be divided into two types: dry-type and wet type. Dry type gas insulated transformers use SF6 gas as the insulation and cooling medium, hence they are called SF6 gas insulated transformers. This type of transformer technology is already quite mature.

The main difference between gas insulated transformers and ordinary oil immersed transformers lies in the insulation cooling medium and cooling mechanism. For self cooling gas insulated transformers, the insulation cooling medium is SF6 gas, and the transformer body is placed in a box filled with SF6 gas. The heat emitted from the iron core and winding due to losses is dissipated to the surrounding medium through the natural convection and radiation of SF6 gas through the cooler and box wall. There are two ways to improve the heat dissipation inside the transformer: one is to increase the thermal buoyancy of SF6 gas; The second is to reduce the total flow resistance of SF6 gas circulation. Due to the fact that the heat dissipation coefficient of the winding surface in SF6 gas is one order of magnitude smaller than that in transformer oil, the capacity of self cooling gas insulated transformers cannot be very large, generally not exceeding 5000kVA..

Box Structure
When viewed from the top, the pressure vessel structure with a rectangular box should be able to withstand strong varying stresses, which are:
(1) When the body is damp and dry, evacuate to 133 degrees Celsius 3Pa, The strong stress exerted by the atmosphere when the vacuum degree is maintained for 12 hours;
(2) The strength test is conducted on the box, and the stress is generated by maintaining a pressure of 245.2kPa for 10 minutes;
(3) Perform leak detection assessment, fill SF6 gas at 196.1kPa, and assess the stress generated after 12 hours.
Cooling method and device
The cooling method is GNAN/GFAN/GFAF. GFAN refers to the self cooling mode of air pump operation; GFAF is a strong internal and external circulation mode where both the air pump and fan operate.
cooling system:
(1) Heat sink. Arrange on one side. Divide into 4 groups of 8 pieces, with each pair of heat sinks and an air pump forming a unit. Install a cooling fan on the side of the box above each set of heat sinks.
(2) SF6 gas circulation channel. Two air flow ducts with air pumps are installed on both sides of the lower part of the box near the radiator, and each duct is connected to two sets of heat dissipation fins to form a unit of piping. There are also two pipes connected to the upper end of the radiator on the 10kV outlet side of the top of the box, but they are arranged in a cross shape with the lower pipe. Facing the 10kV outgoing line, the air pipe on the top right is connected to the connecting pipe on the left heat sink, and the air pipe on the left is connected to the connecting pipe on the right. The circulation channel that constitutes the airflow is: air pump → lower pipe → box → upper pipe → heat sink → air pump.

1. Good fire and explosion resistance performance
SF6 gas is a non combustible gas with high pressure resistance and stable performance. The solid and liquid materials used in gas insulated transformers (for evaporative cooling transformers) are also non combustible. Therefore, gas insulated transformers have no risk of combustion and explosion, which is their main advantage over oil immersed transformers.
2. Moisture resistant
The gas insulated transformer is placed in a fully sealed box filled with SF6 gas, and external moisture, dampness, and dust cannot enter the box. Therefore, gas insulated transformers can be adapted to harsh environments with high humidity, dust and sandstorms, such as underground railways, coal mines, etc.
3. Low maintenance volume
The gas insulated transformer is sealed with inert SF6 gas, and the insulation material inside is almost not degraded. The body of the transformer is isolated from the outside air and will not be affected by external factors like H-class dry-type transformers and cast transformers. It also does not require complex oil treatment and maintenance work like oil immersed transformers. Therefore, there is almost no need for maintenance.
4. Small footprint and light weight
Compared with air, SH6 gas has good insulation and heat dissipation performance, and the installation space of gas insulated transformers is smaller than that of oil immersed transformers and dry-type transformers. SF6 gas weighs only 1/70 of transformer oil at 2 atmospheres and 20 ℃. Therefore, the weight of gas insulated transformers can be reduced by 20% -30% compared to oil immersed transformers. As the capacity of the transformer increases, the magnitude of the reduction may be greater.
5. Widely applicable
Generally, disaster resistant transformers such as dry-type transformers and silicone oil transformers have small single capacity and low voltage levels. Therefore, its scope of use is limited, and gas insulated transformers, due to the use of evaporative cooling, allow for a relatively large single capacity of up to 300000 kVA and high voltage levels, which can enter the field of ultra-high voltage.

Baoding Yuanchen Transformer Manufacturing Co., Ltd. (1999 to present) has gone through more than 20 years of development, with a plant area of ​​98,000 square meters and a building area of ​​26,800 square meters. The company has a complete technical system, covering the entire process of product development, manufacturing and service. The core products are nearly 100 specifications in six categories, including 35KV and below oil-immersed power transformers, with an annual output of 5 million KVA. The company has made remarkable achievements in the construction of management systems, and obtained ISO 9001 quality management system, ISO 14001 environmental management system and ISO 45001 occupational health and safety management system certification in October 2020. Qualifications and honors include: recognized as a national high-tech enterprise in 2016 (re-examined in 2019 and 2022), rated as a specialized and new small and medium-sized enterprise in 2022, and its oil-immersed transformers were selected in the recommended catalog of energy-saving technology and equipment in the field of national industry and information technology in 2022.

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1. Provide technical consultation for customers. Suppliers can provide technical information, instructions for use and other information of the products, and answer customers' technical questions by phone, email, etc.
2. Provide customers with transformer testing and trial operation services. Suppliers can test and test transformers during the sales process to ensure the safety and stability of transformers and provide customers with a better service experience.

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