Common Structure Of Cast Resin Dry Type Transformer Shell
Cast resin dry type transformer are widely used in substations, industrial and mining enterprises, hospitals, residential areas and other occasions because of their advantages of fire prevention, safety, reliability, energy saving, maintenance-free, low loss, low noise, long life, small size and light weight. It mainly comes in two mainstream forms: Epoxy Insulation (ORDT for short) and Paint Impregnated Unsealed (OVDT for short). The former has mechanical strength and short-circuit resistance, and is moisture-proof, dust-proof and corrosion-resistant. After the end of life, it can only be buried deep. The latter has good insulation voltage resistance, heat resistance and flame retardancy. The insulation class can reach H class. After the end of life, it can be degraded and recycled. Cast resin dry type transformers are usually equipped with an enclosure. Its shell material, structure, way of entering and exiting, sealing heat dissipation, basic form, etc. are important factors that must be considered in the design of dry-type transformer shell.
material and structure
The cast resin dry type transformer shell can effectively close the dry-type transformer, play a role in safety protection, avoid the exposed conductors on the dry-type transformer from causing harm to the human body, prevent snakes, mice and other small animals from approaching or climbing to cause short-circuit accidents, shielding electromagnetic radiation, Reduce the impact of noise on the surrounding environment. Therefore, currently used dry-type transformers are usually equipped with an enclosure.
material
Cast resin dry type transformer shells are generally made of stainless steel, aluminum alloy, steel plate and other materials. Commonly used stainless steel brands are 201 (17cr-4.5ni-6mn-n) and 304 (18cr-9ni). 201 stainless steel has poor corrosion resistance and is easy to rust in outdoor environments; 304 stainless steel has good corrosion resistance and can be used outdoors, but the price is relatively high; 316 (17crni-12mo2) stainless steel has good corrosion resistance and high price, and is generally used for special harsh environment. Aluminum alloy has good thermal conductivity and slightly poor strength. Cold-rolled steel plates are commonly used in steel plates, which can be the same color as the switch cabinet, have good strength, and are low in price, but have a long production cycle. In the design process, appropriate materials can be selected according to the user's economic situation and use environment.
structure
There are two common structures of cast resin dry type transformer enclosures: integrated and assembled. The former is mainly used in the early stages. Its advantages are that it does not need to be assembled on site and is easy to install, but the big problem is that it is inconvenient to transport. If it is covered on the dry-type transformer, it is inconvenient to fix the dry-type transformer on the transport vehicle. If it is fixed on the vehicle separately with the dry-type transformer, it will occupy a large vehicle space and the transportation cost will be higher. In addition, when the door of the power distribution room is narrow, the integration will also encounter the problem of not being able to enter the power distribution room. Currently, most choose the latter. The assembled dry-type transformer enclosure consists of left and right frames, front and rear door frames, top cover and connection accessories. It can be assembled on site, easy to transport, and easy to enter the power distribution room.
Individual locations have limited levels of operations and maintenance staff. The door of the cast resin dry type transformer shell is opened with electricity, causing personal injury accidents that should not have occurred. Therefore, designers should clearly request in the technical agreement that the front and rear doors should be equipped with travel switches and electromagnetic locks. The travel switch can be connected to the secondary switch circuit of the high-voltage switch cabinet. Once the door is opened, the travel switch acts, and the secondary switch circuit of the high-voltage switch cabinet is tripped to ensure the safety of the operator. Even if the individual user does not connect the travel switch to the high-voltage switchgear, this protection is meaningless, and the electromagnetic lock (220V power supply from the transformer) can also ensure that the door cannot be opened unless it is urgently unlocked. The high-voltage column insulator on the dry-type transformer can also be replaced with a sensor, and a live display is installed on the door to visually see the live state of the transformer.
Cast resin dry type transformer enclosures shall be assembled in stainless steel. The way of entering and exiting the line is selected according to the situation of the project site. IP20 is used for indoor protection grade, and IP23 is used for outdoor. The designer should comprehensively consider the appearance size of the dry-type transformer casing. In addition to ensuring a safe distance, the heat dissipation performance should also be considered and the foundation should be accurately matched.
