Are outdoor transformers generally dry-type or wet-type?

Outdoor areas naturally use oil-immersed transformers. Dry-type transformers are generally used only indoors!

Advantages and disadvantages of dry-type transformers and oil-immersed transformers. In terms of price, dry-type transformers are more expensive than oil-immersed transformers. In terms of capacity, oil-transformers have a larger capacity than dry-transformers. Dry-type transformers are required in integrated buildings (basements, floors, rooftops, etc.) and crowded areas. The oil transformer is located in a separate substation. The transformer inside a box substation generally uses a box substation. Oil-transformers are generally used for temporary outdoor power supply. When constructing, choose between dry-type and oil-type transformers based on the available space; opt for an oil-type transformer when there is ample space, and choose a dry-type transformer in more confined areas. In regions with a humid and hot climate, oil-based variants are more suitable. If a dry-type transformer is used, it must be equipped with forced air cooling equipment. 1. Appearance: Due to different packaging forms, in dry-type transformers the core and coils can be seen directly, while in oil-type transformers only the transformer’s casing is visible ； 2. Different lead types: Dry-type transformers mostly use silicone rubber bushings, while oil-type transformers mostly use porcelain bushings ； 3. Different capacities and voltages: Dry-type transformers are generally used for power distribution; their capacity is usually below 1600 KVA, and the voltage is below 10 KV, although there are some variants that can operate at 35 KV as well ； On the other hand, oil-filled transformers are available in all capacity levels, from small to large, and cover all voltage grades as well ； The UHV 1000KV test lines under construction in our country will definitely use oil-filled transformers. 4. Insulation and heat dissipation are different. Dry-type transformers generally use resin for insulation and rely on natural air cooling; those with larger capacity use fans for cooling. Oil-type transformers, on the other hand, use insulating oil for insulation, and it is the circulation of this insulating oil within the transformer that carries the heat generated by the coils to the transformer’s radiators for heat dissipation. 5. Applicable locations: Dry-type transformers are mostly used in areas where \"fire and explosion prevention\" is required; they are commonly employed in large buildings and high-rise buildings ； Oil-type transformers, due to the risk of oil spraying or leaking in the event of an accident, which could lead to fires, are mostly used outdoors in locations where an \"accident oil pond\" can be dug. 6. Their capacity to handle loads differs; generally, dry-type transformers should operate at their rated capacity, while oil-type transformers have a better overload capacity. 7. The cost is different: For transformers with the same capacity, the purchase price of dry-type transformers is much higher than that of oil-type transformers. Dry-type transformer models generally start with SC (epoxy resin cast encapsulated type), SCR (non-epoxy resin cast solid insulation encapsulated type), SG (open type)

(1) Difference between dry-type transformers and ordinary transformers: “Of course, what’s the same is that they are both power transformers, and they both have a core for the magnetic circuit as well as windings for the electrical circuit.” And the biggest difference lies between “oil-type” and “dry-type”. In other words, the cooling media for the two are different: the former uses transformer oil (and of course other oils such as β-oil) as the cooling and insulating medium, while the latter uses air or other gases such as SF6 as the cooling medium. Oil transformation involves placing the core and windings, which make up the transformer’s structure, inside a tank filled with transformer oil. Dry-type transformers often enclose the core and windings with epoxy resin; there is also a type that is widely used these days and does not involve such encapsulation – in this case, the windings are covered with special insulating paper dipped in specialized insulating paint, thereby preventing the windings or core from getting wet. (And since different classification methods based on manufacturing processes, applications, and structure lead to various categories, from a narrow perspective) in terms of output and usage, the voltage level of dry-type transformers currently reaches only 35 kV, and their capacity is smaller compared to that of oil-type transformers, at around 2500 kVA. Moreover, the manufacturing process for dry-type transformers is more complex than that for oil-type transformers with the same voltage level and capacity, resulting in higher costs. So currently, in terms of usage, oil is still used more. However, due to its environmental friendliness, as well as advantages such as flame retardancy and impact resistance, it is often used in indoor power supply and distribution areas with high requirements, such as hotels, office buildings, and high-rise buildings. “If you are just a transformer user, this should be enough to know.” (2) Advantages and disadvantages of dry-type transformers versus regular transformers: Each type has its own advantages and disadvantages. Oil-filled transformers are cheaper to manufacture and easier to maintain, but they are flammable and explosive. Due to their excellent fire resistance, dry-type transformers can be installed in the load center areas to reduce voltage drops and power losses. However, dry-type transformers are expensive, large in size, have poor moisture and dust resistance, and are noisy. The oil-type version is gradually being phased out in favor of the dry-type version. The dry-type version can be disassembled for easier transportation, cleaning, and maintenance; it does not require a base frame, and there is no oil leakage issue ； It is relatively easy to distinguish from the outside ； The biggest difference between oil-immersed transformers and dry-type transformers is the presence or absence of \"oil\". Since oil is a liquid that is fluid, oil-immersed transformers must have a casing; inside this casing is transformer oil, within which the transformer’s coils are submerged. From the outside, it is not possible to see the transformer’s coils ； Since a dry-type transformer contains no oil, it does not require a casing, allowing the transformer’s coils to be seen directly ； Another feature is that oil-immersed transformers are equipped with oil conservators, which contain transformer oil; however, modern oil-immersed transformers also exist without such oil conservators ； To facilitate heat dissipation, that is, to enable the insulating oil inside to dissipate heat more easily, oil-immersed transformers are equipped with radiators on the outside, similar to cooling fins. Dry-type transformers, on the other hand, do not have such radiators; instead, they rely on fans located beneath the transformer coils, which function somewhat like the indoor unit of a household air conditioner ； Due to fire safety requirements, oil-immersed transformers are generally installed in separate transformer rooms or outdoors, while dry-type transformers are definitely installed indoors, usually in low-voltage distribution rooms, alongside low-voltage distribution cabinets.

Wuning Yitang has been explained in detail; generally, oil-immersed transformers are used. Inside buildings, dry-type transformers are preferred as their capacity is relatively low. Dry-type transformers are also used in factories. I’m using a 3000 KVA 6/0.4 KV outdoor dry-type transformer, which can be placed inside a cabinet.

Oil-immersed transformers are generally used outdoors. There are also those that use box-type substations, which contain not only dry-type transformers but also high and low voltage switchgear.