Distribution transformer is a transformer that provides the final voltage transformation in the electric power distribution system, stepping down the voltage used in the distribution lines to the level used by the customer. In the distribution system, there are different kinds of transformers available like single phase, three-phase, underground, pad-mounted, pole-mounted transformer.
Distribution Transformer VS Power Transformer
The power transformer is used in transmission networks with high voltages whereas, and the distribution transformer is used in LV/MV distribution networks.
Types of Distribution Transformer
Generally, this transformer is available in different sizes with efficiencies along with insulating oil. The selection of this transformer mainly lies in the requirement and budget of the user. There are four types of distribution transformer connections available like star-star, delta-delta, star-delta, delta-star and Zig Zag/delta zigzag.
The mainly parts of this transformer include Oil Tank, Conservator, Buchholz Relay, Breather Unit, Oil Indicator, Temperature Detector, Pressure Relief Device, Thermal Relay, Radiator, and Bushing.
1. The oil tank is used to soak the windings by placing it in.
2. A conservator is arranged above the oil tank at the outside of the transformer frame. It is connected to the main tank with the help of a metallic tube. The oil within the tank can 3. be easily contacted & enlarge throughout loading so that the temperature of the oil can be increased and decrease.
4. Buchholz relay is used when a conservator tank is used. Because it indicates errors like loss of oil once it goes low, improper flow of oil between the tank & transformer.
5. Breather Unit includes silica gel that absorbs moisture in the oil. It changes its color from blue color to pink color it is not capable to absorb moisture in the oil.
6. The oil indicator indicates the level of the oil within the conservatory unit.
7. The temperature detector monitors the temperature of the oil. If the temperature of the oil increases to a certain level then the transformer will be disconnected from the service.
8. Pressure relief device decreases the pressure within the transformer to avoid an explosion of the transformer.
9. Thermal relay is used as an indicator for the temperature of the winding
10. The radiator is used to increase the transformer’s cooling efficiency.
11. The bushing is used to connect the internal windings of the transformer with the help of an exterior electrical network.
Pad Mounted Type
Pad mounted transformer is a ground mounted electric power distribution transformer in a locked steel cabinet mounted on a concrete pad. Since all energized connection points are securely enclosed in a grounded metal housing, a pad mounted transformer can be installed in places that do not have room for a fenced enclosure.
The Pad-mount transformer is oil filled unit. The core and coils are enclosed in a steel oil-filled tank, with terminals for the transformer accessible in an adjacent lockable wiring cabinet. The wiring cabinet has high and low voltage wiring compartments. High and low voltage underground cables from below enter the terminal compartments directly. The top of the tank has a cover secured with carriage bolt-nut assemblies. The wiring cabinet has sidewalls on two ends with doors that open sideways to expose the high and low voltage wiring compartments.
Dry-type transformers, also known as cast resin transformers, the windings and core are kept within a sealed tank that is pressurized with air. These transformers simplify installation since they are dry, without cooling oil, and so require no fire-proof vault for indoor installations. The epoxy protects the windings from dust and corrosive atmospheres.
Pole Mounted Type
Pole mounted transformers are electric utility distribution transformers that are mounted on an electrical service pole and are usually at the level of the overhead cables. These are used for changing high distribution voltage to low like 120/240-volt power. These types of transformers are used in a wide rural area, ranges from 16 kVA to 100kVA. These are available in small size and easy to fit on single-pole structures. These transformers are reliable to harsh climates when they used in remote areas.
More Details Reference
Pole Mounted Transformer:
Dry Type Transformer:
Pad Mounted Transformer:
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