Distribution Transformer, Types of Distribution Transformer And Connection

A Distribution Transformer is a type of step-down transformer used in urban areas. It reduces high voltage/voltage levels that go from the substation to the level used before the user can reach the premises. A distribution transformer or service transformer is a transformer that provides the final voltage exchange.

Distribution Transformer, Types of Distribution Transformer

The Distribution Transformer is a gallon isolated transformer that converts high voltage electricity to a suitable voltage level suitable for homes and businesses. A power distribution system, it reduces the voltage used in the distribution lines to a certain level.

Electrical energy is transmitted through the distribution transformer to reduce the high voltage level in the distribution network to the low usage level. A Distribution Transformer is a service that ensures the final exchange of voltage in the distribution system and reduces the voltage used in the distribution lines to the level used by the customer.


There are four types of distribution transformer connections: Star Star, Delta Delta, Star Delta, Delta Star, and Zig Zig / Delta Zig Zig.
Distribution transformers connected to Delta Star. This circuit requires three conductors on the high voltage side and four conductors on the low voltage side, and it also provides Star Point wire. It can handle both single-phase and three-phase loads.

The two most commonly used three-phase winding configurations are delta and star, named after the Greek and English letters that each looks like. In a delta configuration, the three windings are butt-connected to form a closed path.

Delta-connected transformers are widely used in low-power distribution networks. With the primary windings providing a three-wire balanced load to the utility and the secondary windings providing the required 4-wire neutral or ground connection.

Although delta windings are often operated without grounding, the delta portion can be center-tapped and grounded, or the corner of the delta can be grounded. In a star configuration, one end of each of the three windings is connected to neutral. A phase is connected to the other end of the three windings. Neutral is usually grounded.

Types of Distribution Transformer

Single-phase transformer
Three-phase transformer
Pad Mounting transformer
Pole mounted transformer
Underground transformer

Single-phase Transformers

Single-phase transformers accept single-phase AC power and single-phase AC power, usually at higher or lower voltage levels. Energy is transferred from one circuit to one or more circuits by electromagnetic induction.

It is used in electricity distribution in the suburbs because the total demand and related costs are lower than those of a three-phase distribution transformer. It is used as a step-by-step transformer to reduce the home voltage to a reasonable value without changing the home frequency.

Single-phase transformers are used in power supply and other equipment to convert alternating voltage and current from one value to another. Transformers are important in ensuring the electrical insulation required for the safe operation of many laboratory tools and medical equipment. Therefore, it is often used to operate electronic appliances in residential areas.

Single-phase transformers are widely used in commercial low-voltage devices as electronic equipment. They work as a step-down voltage transformer and reduce the cost of household voltage. On the other hand, a rectifier is usually connected to convert AC to DC voltage, used in electronic applications.

Three-Phase Transformer

The three-phase transformer is considered the backbone of the power distribution system. It is used to transmit enormous amounts of energy. Its main function is to increase and decrease voltages at different stages of the power system network.

Three-phase transformers are used in almost all areas of electrical power systems such as power generation, transmission, and distribution, and all industrial branches are supplied with or connected to a three-phase system. Therefore, three-phase transformers are used to increase or decrease the voltage in three-phase systems.

Three-phase transformers are so common in power distribution systems that we need three-phase transformers to step up or step down voltage. Three-phase transformers are more economical for supplying large loads and high power distribution. Although most of the equipment used is connected to single-phase transformers, they are not preferable for high power distribution in terms of economy.

Pad Mounting Transformer

The Pad-mounted transformer is an earthing distribution transformer that is usually housed in a locked metal cabinet located on a small concrete site. These distribution transformers are generally located in residential areas. Since all live contact points are enclosed in a grounded metal box, such a transformer can be located in residential areas and does not need to be fenced, like transformers in substations.

Since all live connection points are securely enclosed in a grounded metal enclosure, the site transformer can be installed in locations where there is no room for an attachment. Padmount transformers are used with underground power distribution lines at service points to lower the primary line voltage to a lower secondary voltage supplied to utility consumers. One transformer can serve one large building or several houses.

A Pad-mounted transformer is usually a special type of enclosure for larger transformers installed in locations accessible to the general public. The transformer typically has features such as tamper-proof design, tamper-proof bolts and screws, lockable compartments with hinged doors, bottom entry of primary and secondary cables, and blanked vents, if applicable.

Pole Mounted Transformer

Pole-mounted transformers, the most common type of distribution transformer used is a single-phase oil-filled pole transformer, commonly referred to as a “pole” or “overhead” transformer. Differences in air transformers are usually related to their physical dimensions and how they are connected to obtain different output secondary voltages.

Pole-mounted transformers are power distribution transformers mounted on poles of electrical networks (wood or concrete) and are usually located at the level of overhead cables. Pole mounted transformers are common bread box transformers used to convert distribution voltage to 110/230 V power used in homes and small commercial installations.

Made from high-quality copper wire and insulating oil, these Pole-mounted transformers can be specially designed or configured to meet power companies’ requirements in most countries. We do our best to meet customer needs.

Underground Transformer

Underground transformer Image, Most of the transformers serving consumers from underground distribution lines, are called site transformers. They are electrically the same as the pedestal units, but packaged in a box-shaped, oil-filled metal enclosure and installed on a concrete foundation at ground level or platform.

An underground cable enters and exits the unit out of the ground and out of sight. Underground transformers and substations face a unique set of challenges during installation and operation. Placing transformers underground is an ideal solution for power supply where surface ground availability is limited, such as in densely populated urban areas.

However, in such cases, the need to reduce fire and environmental risks becomes a critical issue. There is another commercially available underground transformer. This type is truly an underground device as it is completely below ground level. It is designed for installation in a maintenance hole or small underground storage.

It resembles a ceiling block in general appearance, but since it is underground. The high and low voltage terminals must be completely insulated and waterproof. Explosion-proof air-filled transformer with power up to 300 kVA, which can be used near the face in mines with safety lights. The Nitrogen Filled Transformer for Mining is the latest trend.

While the line of power substations for underground networks is designed for all transformer substations applications for public or private distribution networks. These prefabricated substations comply with the design standards for MV / LV substations.

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