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What is Distribution Transformer

 

 

A distribution transformer is a type of electrical transformer that reduces the voltage of electricity from the distribution lines to a level suitable for use in homes, businesses, and other end-user facilities. It acts as the final step in the voltage reduction process before electricity reaches consumers.These distribution transformer are vital for converting high-voltage electricity from transmission lines into lower voltages suitable for end-users, including residential, commercial, and industrial facilities.

GNEE EC offers both liquid-immersed transformers and dry-type transformers that are manufactured in accordance with the most demanding international standards and industry demand.

 

Distribution transformers are electrostatic devices responsible for distributing electrical energy to homes, businesses, and end-users. Typically, the primary voltage of these transformers is less than 35 kV. They primarily function as step-down transformers, adapting grid-level voltages to levels appropriate for local consumption. Voltage standards for distribution transformers vary across different markets. For instance, common distribution transformer voltages in the American market include 7.2 kV, 13.8 kV, 14.4 kV, 24.94 kV, and 34.5 kV. In Europe and Austrilia, typical distribution network voltages are 3.3 kV, 6.6 kV, 11 kV, and 33 kV.

 

As one of the world leaders in distribution transformers, GNEE EC offers the widest portfolio of distribution transformer products that are designed for reliability, durability, and efficiency required in utility, industrial, and commercial applications.

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types of Distribution Transformer
 

Distribution transformers can be categorized based on 3 factors:

Based on Cooling Methods

Dry-Type Transformer:These transformers do not use liquid for cooling and are instead cooled by air circulation. Dry-type transformers are highly favored in environments where fire safety is a major concern, such as indoors, in underground installations, or near residential areas.

  • Lower no-load loss

    Adopts high-quality amorphous alloy ribbon, the no-load losses are reduced by up to 70%

  • Low noise

    Develops a unique iron core mounting technology and uses vibration analysis simulations to reduce noise

  • Small footprint

    A compact design, easy installation

  • Maximum safety

    High mechanical strength, waterproofing, and anti-short-circuit capability

Oil-Immersed Transformer: Oil-immersed transformers use oil both as an insulator and coolant. This type provides better insulation and effective cooling, allowing the transformer to be smaller in size and cost-effective compared to dry-type transformers.

Product Advantage:
  • Low loss: low no-load loss,low load loss, low operating costs.
  • Powerful anti-short circuit capacity, high anti-lightning impulse capacity.
  • Long service life: The oil tank adopts a fully sealed structure, the tank and the box edge can be connected by bolts, which can be isolated from the external environment to prolong the service life of the transformer.
  • High reliability: The seal parts of the oil tank have been improved to increase the reliability.

Based on Installation Environment

Pole-Mounted Transformer: These transformers are installed on utility poles, typically at a height to keep them out of reach. They are designed for rural and suburban overhead distribution where space is not constrained. The elevation helps in cooling by air and protects against vandalism. These are generally single-phase transformers due to their application in less densely populated areas.

 

Pad-Mounted Transformer: Suited for urban areas, pad-mounted transformers are placed on a concrete pad and enclosed in tamper-proof metal cabinets. They are commonly used where underground power distribution is prevalent, offering both safety and aesthetic benefits by hiding the transformer components from public view. These are often three-phase transformers to cater to higher load demands in commercial zones.

 

Submersible Transformer: These are specially designed for operation in conditions where water exposure is possible, such as flood-prone areas or within underground networks. Submersible transformers are robust, completely sealed, and capable of operating while submerged, addressing unique environmental challenges without compromising the reliability of power distribution.

Based on Phase Configuration

Single-Phase Transformer: These are typically used in residential settings where the demand for electricity is relatively low and distributed over a wider area. Single-phase transformers are simpler in design and cost-effective, suitable for stepping down the voltage for home use from the nearest distribution line.

Three-Phase Transformer: In commercial and industrial settings where large amounts of electrical power are required, three-phase transformers are essential. They distribute power more smoothly and efficiently, providing a continuous power flow that is ideal for heavy-duty machinery and commercial systems. These transformers are more complex and expensive but necessary for balancing and handling high power demands.

 

Each transformer type is tailored for specific operational needs, balancing factors like cost, safety, environmental concerns, and power handling capabilities. These variations allow for flexibility in addressing the unique demands and constraints of different electrical distribution networks.

Distribution Transformer

 

Distribution Transformers

 

01

Single Phase

This distribution transformer is designed for single-phase power systems. The primary winding of this transformer is connected to an incoming 3-phase supply line through 3 separate terminals. It has one secondary winding for each phase and is connected to the load through different terminals. The secondary voltage is equal to the sum of all three phases multiplied by their respective turns ratio of the primary windings.

10KV oil-immersed distribution transformers

 

02

Three Phase

On the other hand, this type of distribution transformer is intended for three-phase power systems. It has three secondary windings connected in a delta connection with a shared neutral wire (ground). Each of these three secondary windings has a different voltage depending on their turn ratio relative to one another.a three-phase transformer with four poles will have three secondary windings with 120 degrees and one voltage winding connected to all three others equally (in parallel).

1500 kva Pad Mounted Transformer

 

03

Pad-Mounted

These transformers are installed directly on concrete pads or pad foundations. It can be used in place of conventional pad-mounted transformers by using a direct burial cable, which allows you to bury power lines underground without worrying about corrosion or breakage.
Typical applications include small commercial buildings, apartment complexes, and industrial plants where the need for more than one phase is minimal or not required (one phase may be used for lighting while another is used for heating). Or it can also be used in areas with no overhead wires, or safety may be an issue due to high voltage lines being present near an electrical substation.

25kva single-and-three-phase-power-pole-mounted

 

04

Pole Mounted

These are designed to be mounted on poles above ground level so they can be easily accessed when necessary. They are also used for pole-mounting of special purpose transformer banks such as capacitor or recloser banks. Pole-mounted transformers may have an internal grounding system or an external grounding connection point for use with a separate grounding electrode system. This type of distribution transformer may also include other features such as bushings, lightning arrestors, and surge arrestors.

oil filled Distribution Transformers

 

Understanding the differences between distribution and power transformers

Understanding Distribution Transformers and its Types
Also known as a service transformer, distribution transformers are types of step down transformers. They provide the final voltage transformation before the electric current is passed to the circuit via distribution lines. Distribution levels consist of power of up to 10MVA that is transmitted.
There are two types of distribution transformers that are used today – liquid and dry type transformers. Liquid filled transformers are known for their compact size, and efficient power distribution ability. Dry type transformers are specifically designed for application safety and fire protection.
Both transformers are cooled passively. Liquid filled transformers remove heat via the tank walls using thermal conduction. Dry type transformers have internal convection air flow for core cooling.

A Look at Power Transformers
Power transformers are designed for applications where the power exceeds 10MVA. These transformers are designed in medium or large sizes, and with greater insulation than other transformers. This results in increased cooling. Power transformers are designed to provide benefits of low noise levels, and performance efficiency, while complying with special safety and reliability requirements.
Power transformers can be designed as liquid filled Transformers, or as Generator Step-up Units (GSUs). The GSUs transform electric current from medium to high voltage levels. Power transformers can be used along with phase shifters to balance the power flow, and optimize power transmission.

The Differences between the Two Transformer Products
As you may realize there are certain differences between these two transformers.
One is designed for applications with power requirements up to 10 MVA while the other is for application greater than 10 MVA.
Distribution transformers are designed in compact sizes, while power transformers are designed in medium and large sizes.
The cooling of power transformers is achieved through high levels of insulation. Distribution transformers may use thermal conduction, or convection for passive cooling.

 

Distribution Transformer Construction

The designing of a distribution transformer can be done similarly to small size transformers. The main parts of this transformer mainly include Oil Tank, Conservator, Buchholz Relay, Breather Unit, Oil Indicator, Temperature Detector, Pressure Relief Device, Thermal Relay, Radiator, and Bushing.
The oil tank is used to soak the windings by placing it in.
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 be easily contacted & enlarge throughout loading so that the temperature of the oil can be increased & decrease.
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.
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.
The oil indicator indicates the level of the oil within the conservatory unit.
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.
Pressure relief device decreases the pressure within the transformer to avoid an explosion of the transformer.
Thermal relay is used as an indicator for the temperature of the winding
The radiator is used to increase the transformer's cooling efficiency.
The bushing is used to connect the internal windings of the transformer with the help of an exterior electrical network.

Vacuum Cast Resin Dry Type Transformer

What is the purpose of Distribution Transformers

 

 

Stepping Down and Regulating Voltage – Residential societies and homes require a low-voltage power supply. Though the input voltage supply to transformers is usually high. But distribution transformers ensure that they supply low voltage output when transmitting power to residential areas. They are capable of regulating voltage by stepping-down voltage to the required voltage level. Distribution Transformers can reduce high voltage of thousands of kV to low voltage of hundreds of kV.


Electrical Isolation – Other than stepping down the voltage, the distribution transformer also helps in offering isolation between the distribution channels and the recipient channels. It acts as a wall between the two to safeguard the electrical appliances and machinery from getting damaged due to faulty power supply. It usually happens when there is a sudden voltage surge or short circuit from the end of distribution channels.


Safety to Electrical Appliances – High voltage power supply and fluctuation in voltage are the major reasons for the occurrence of electrical shocks and electrical hazards. It can cause short circuits, damage to electrical appliances, damage to property and life, and fire. The distribution transformers help in supplying consistent and safe voltage for the functioning of electrical appliances. It minimizes the risk of electrical hazards and offers safety to both appliances and life.


Reduces Power or Energy Loss – During the transmission of power to long-distance places, the power distribution channels transmit high-voltage power. It helps in reducing the problem of power loss when the transmission takes place.the high voltage power is not suitable for electrical appliances or machinery. That is when distribution transformers come to the rescue by cutting on power loss and stepping down the voltage. It not only saves from power or energy loss but also helps supply reliable voltage for electrical devices.

 

Distribution Transformer Design
 

A distribution transformer includes four main components that determine its design. These main parts are the input connection, the output connection, the windings or coils, and the core. 

1. Input Connections

Input connections are also introduced as the primary section since electricity goes into the system; it should be connected to this site.

2. Output Connections

The output section has another name, which is the secondary part of the transformer. In that section, electrical energy is sent to the electric instrument in your factories or house. Commonly, the voltage in the transformer's output section (or secondary side) is lower than in the primary section.
One of the basic differences between a power transformer and a distribution transformer is that a power type commonly has one secondary and one primary or one output and input setup. A distribution transformer may have one primary section and two or more secondary components, according to the purpose.

3. Winding

All forms of transformers include two windings, and the distribution transformer is identical. It is classified into primary and secondary types. The primary one has a performance of drawing energy from the supply. The secondary type transmits electric energy to electrical equipment.

4. Core

The transformer core presents a path that determines the magnetic flux produced in the transformer. Commonly, the core is not a solid steel bar. It consists of several laminated steel sheets, or plates folded neatly. This model is to eliminate or reduce the heating.
The transformer's cores have two forms employed based on users' demand: Core Type and Shell Type. The major difference between these forms is how the primary and secondary sections folded around the steel core.
Core type: The windings are turned in the laminated core.
Shell type: The laminated core wraps the components.
Once the input voltage enters the primary winding, alternating current begins to move in this winding. When the current goes across it, a constant changing and alternating field are produced in the transformer's core. Once this magnetic field operates through the secondary winding, a new alternating voltage is created in that one. Click here to see the foundation of a distribution transformer completely.

 

 
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The products have passed SGS, intertek, CCC, CE and other international certifications. Noise, easy installation, energy saving and emission reduction, long service life, etc. The product production cycle is short, easy to install, and fast delivery. At present, the company has more factories.Our team is composed of very professional engineers. We strive to deliver you on time within the budget Power equipment, and provide excellent product quality. Provide you with the ultimate experience.

 

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FAQ
 

Q: Which transformer is used in an electrical distribution system?

A: A step-down transformer is used in an electrical distribution system

Q: What is the difference between distribution & power transformer?

A: The power transformer is used in transmission networks with high voltages whereas a distribution transformer is used in low voltage distribution networks.

Q: What are the types of transformers?

A: The different types of transformers are step up, step down, power, distribution, instrument, potential, comprising current, single-phase, 3-phase, auto, etc.

Q: Why transformers are rated in kVA?

A: Because they do not change the power factor (PF) of their output power.

Q: What is the formula for kW to kVA?

A: Apparent power (kVA) = Actual power (kW) / power factor (pf)

Q: What do distribution transformers do?

A: Distribution transformers are the last port of call on a distribution grid. The grid will soak up high amounts of electrical energy and distribute it accordingly for the customer, be it household or commercial use.
The distribution transformer is responsible for outputting the correct voltage. It converts the voltage from the transmission lines and delivers it for domestic or industrial usage.

Q: How does a distribution transformer work?

A: Due to the fact that a distribution transformer has no moving parts, the concept of how it works is fairly simple…
The main body of the transformer houses two or more coils of insulated wires wound on a steel core. As soon as voltage is introduced to one of the coils (Primary/Input Coil), the core magnatises. As a result, voltage transfers into the other coil (Secondary/Output Coil). It's down to the turn ratio of the two coils to determine the change in voltage levels and final distribution.

Q: Why do we use distribution transformers?

A: Distribution transformers are used for the correct distribution of electrical energy to the necessary consumer.
Typically, distribution transformers are needed to manage the voltage output (often at a low level).industrial purposes may require a low voltage of less than 33KV whilst more domestic users only need between 220v-440v.
Not only do distribution transformers help to distribute the correct levels of energy but they combat energy waste and core losses too – critical for today's climate.

Q: What makes distribution transformers effective?

A: Efficiency and simplicity are key two factors in a distribution transformer's performance.
For obvious, global reasons, modern distribution transformers are designed with efficiency in mind.because a distribution transformer is always “online” and operates at loads less than full load, they are designed to reduce core losses by operating for maximum efficiency around 60-70%. The ability to handle clusters of loads, reduces thermal energy waste too. Having said that, older transformers are not as savvy and may need to be updated.
Although distribution transformers are bulky and weighty, they are not excessive in size. This means most installs are swift and they can be placed almost anywhere, as long as it's not over a great distance so that the voltage drops.

Q: Where are distribution transformers installed?

A: Depending on the type of distribution transformer, they can be squeezed in to the tightest of spaces; generally, you'll find them in open and expansive spaces on solar or wind farms, for example. Generally, you will see two different types of distribution transformer: pole mounted (if transmission lines run above ground) and pad mounted (transmission lines underground).

Q: What happens when a distribution transformer fails?

A: The transformer failures will results in loss, repair or replacement of transformer and also, power loss due to power not supplied to consumers.

Q: What is the most common cause of transformer failure?

A: The most common causes of transformer failure include overloading, deterioration, power surges and moisture. Many of these failures occur within the transformer winding insulation and often times can be detected early by conducting rigorous visual, mechanical, and electrical inspections throughout its service life.

Q: How do I choose a distribution transformer?

A: It is advisable to choose the distribution transformer's phase configuration according to the applications. Check the efficiency – When selecting distribution transformers one must look for efficiency. An efficient transformer helps in reducing power loss by converting the voltage in the right way.

Q: How do I know what size transformer I need?

A: To determine the size of the transformer needed, follow the steps below:
Note down the load voltage.
Next, note down the load current.
Multiply the voltage by the current.
Divide the result by 1000.
The result is the minimum kVA(kilovolt-amperes) for a single-phase transformer.

Q: What is the difference between a power transformer and a distribution transformer?

A: While power transformers are designed to step up or down voltage levels for transmission purposes, distribution transformers are made specifically to provide stepped-down voltages to consumers. There are various distribution transformers available on the market, each with its advantages and disadvantages.

Q: What is the difference between station transformer and distribution transformer?

A: Power Transformer: is strategically located in key junctures of the electricity network at power stations and major Substations. It is a central command to transmit electricity over the distance. Distribution transformers: are installed in close proximity to end users, who live in urban and industrial areas.

Q: How do you tell if a transformer is bad?

A: Exterior bulging on the transformer.
Insulation color change.
Vibration changes.
Incorrect or lack of voltage.
Burn marks on or near the unit.
Irregular operation temperature.
Automatic protection devices activate when transformer first energizes.
Low insulation resistance.

Q: What is the standard of distribution transformer?

A: Distribution transformers are to be procured with Standard ratings as per IS. The maximum allowable losses at rated voltage and rated frequency permitted at 75°C for Distribution transformers can be chosen by the utility as per IS 1180 (as amended).

Q: Why are distribution transformers important?

A: Their role is crucial in reducing voltage from high transmission levels to lower distribution levels. These transformers find application in supplying power to residential neighborhoods, shopping centers, and small industrial facilities.

Q: What is the difference between single-phase and three-phase distribution transformer?

A: Single-phase transformers are naturally less efficient than three-phase ones. This is largely because a single-phase system faces more power loss and voltage drop due to the intermittent nature of the power flow. Three-phase transformers, with their continuous and overlapping power supply, are more efficient.

Henan GNEE Electric Co., Ltd. is well-known as one of the leading distribution transformer manufacturers and suppliers in China. Please feel free to wholesale cheap distribution transformer in stock here from our factory. Quality products and low price are available.

Amorphous Metal Transformer, encapsulated dry type transformer, Amorphous Alloy Steel Transformers

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