High Voltage Distribution Transformer

A High Voltage distribution transformer is an electrical unit that distributes the conversion of voltage. Which should be transmitted in a power matrix. It converts the electromotive force that’s distributed to a version that is usable in all kinds of your properties, usually to a minimum of 240 volts.

Daelim Belefic has been creating classy power-based items and tools for over 15 years. Daelim’s project retail slogan is DAELIM EDGE + ADVANTAGE. This slogan has been the key to allowing Daelim to provide various qualities and excellence. Speedy customer care delivered customized according to client needs.

The brand has expert engineers who can find solutions to every crisis involving electric items. Daelim has more than one standard in upholding the quality of its products. Thus, Daelim offers varying high-quality electric items.

Pad-mounted Transformer

We can provide you single phase and three phase pad mounted transformer

Dry-type Transformer

Type:Cast resin; Rated Capacity: Up to 25MVA; Rated Voltage: Up to 36KV;

Pole Transformer

TypeCSP type Frequency: 50/60Hz; Rated Power: 5~167kva

Dry-type Transformer

Frequency: 50/60Hz Rated voltage:10kv, 20kv,30kv Rated Power: 400~2500kva

High Voltage Distribution Transformer: The Ultimate FAQ Guide

What Is A Transformer?

To begin with, you should know what a transformer is before we go through the details of high voltage transformers.

Chances are, you have passed by a transformer without noticing it, that is because they come in all shapes and sizes. There are transformers that are as small as a barrel, and there are transformers that are as big as a car as well.

Regardless, all of these transformers have one thing in common, and that is to regulate currents, voltages, or electricity in general.

When it comes to changing voltage levels, transformers are also capable of transferring electricity from one circuit to another. During this process, the frequency will not be disrupted. Most transformers only function with the use of an AC supply.

Fluctuation in supply voltage will be affected by the changing currents.

This means that if there is an increase in the current, there will be an increase in voltage as well, and vice versa.
In addition, transformers promote safe electrical transmissions since their function is to regulate voltage levels by either increasing or decreasing the voltage levels. This is also called step up and step down. This can be done at long distances as well.

What Is A High Voltage Distribution Transformer?

To put it in simpler terms, a high voltage transformer is a type of transformer that effectively operates at high voltage levels. They are commonly used in high voltage laboratories for experimental purposes.

High voltage transformers are designed to work with transient voltages and surges at normal operations when the insulation under test wears down.

Since they are built to withstand impulse voltages, the insulation of high voltage transformers are precisely designed and formed. Common examples of these are single-phase core-type transformers and Oil-Immersed Distribution Transformer.

220 kVA High Voltage Distribution Transformer

What Are Single-Phase Core-Type Transformers?

This transformer is fairly common since you can see them on utility poles, both concrete or wooden ones. They can also be mounted as a cluster.

They have the shape of a cylinder with a sealing structure. Each of which is connected with grounding devices, hooks, supporting lugs, one or two high voltage bushings on the cover, eyebolt, and connecting terminals.

Single-phase distribution transformers can be used alone for the supply of a single phase load. It can also be used for the supply as one of three units in a bank for the supply of a three phase load.

They are specifically designed for servicing residential overhead distribution loads. They are also compatible with specific commercial loads, industrial lighting, and diversified power applications.

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How does High Voltage Transformers Works?

The core of high voltage Distribution transformers works directly to the path of its magnetic field, which is between the primary and secondary coils to prevent wasting energy. Once the magnetic field reaches the second or secondary coil, this forces electrons to move, which then creates an electric current through electromotive force.

High voltage transformers are usually oil-immersed,which means that its insulator is mineral oil. Bakelite sheets are what keeps the high tension windings and low tension windings separated. High voltage transformers that are used for HV cable testing are also required to supply sufficient electric currents.

In return, this can generate a lot of heat, and this is where its cooling system comes in. However, its cooling system does need the right maintenance in order for it to survive in the long run.

When it comes to insulator testing purposes, the required current is low but while the insulator breaks down during the process of testing, you can expect a huge flow of current through the High Voltage Transformers.

For this current to be controlled, there should be a high resistance connected in series with the transformer since insulation testing does not require high currents. High voltage transformers are used for this application, and they do not need to have a high kVA rating.

630 kVa Mini Substation and Miniature Substation
High Voltage

Any number beyond 500 kV is no longer considered economical to use for a single transformer. This is because the size is simply too much. For situations like these where more than 500 kV is needed, there should be at least two units conjured in series to produce the required voltage.

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Low Voltage

Low voltage is supplied to the low voltage winding of a step up High Voltage Transformers. The tank of this transformer will be earther. For the secondary, it is connected to the tank of the transformer that is earthed.

Through the high voltage bushing is where another end comes. The bushing is specifically designed and manufactured to withstand full secondary high voltage to meet ends with the earthed potential of the transformer tank.

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Tapping Terminal

There will be another tapping terminal that will through the high voltage bushing. The high voltage end and the tapping terminal ends are all connected across the primary of the second High Voltage Transformer.

Secondary Winding

One of the ends of the secondary winding of the second transformer is connected to its tank. However, the tank of the second High Voltage Transformer is not earthed compared to the first transformer. The second transformer is isolated and insulated from the earth for the full secondary voltage of the transformer.

Voltage Regulation

There is one element you should avoid from high voltage Distribution Transformers, and this is the surges from the high voltage side of the transformer. In terms of accuracy for voltage measurement, the voltage regulation of the transformer should be sufficiently smooth.

Sudden variation of voltages during the test should also be avoided. Voltage regulators should not disrupt the voltage waveform once the test is ongoing,

The output voltage of high voltage transformers are regulated by changing the input voltage on the primary side of the transformer.

What Are Distinguishing Functions and Features of Distribution Transformers?

Construction Features

The construction features that make up a distribution transformer bear striking resemblances to tiny transformer units. There are primary parts that cover a distribution transformer. They are an oil tank, a conservator. Buchholz relay, a breather unit, an oil indicator, a temperature detector unit, a pressure relief tool, a thermal relay, a radiator, and a bushing. 

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Oil Tank

The oil tank in a High Voltage distribution transformer functions in a distribution transformer. The unit absorbs the air by taking it all in. This part moderately balances the amount of air a distribution transformer has. Balanced air amount in a distribution transformer enables the electrical unit to power transmission evenly to multiple outlets.

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The conservator is at the top of the High Voltage transformer’s oil tank in the external area of the electrical unit. You can see it’s attached to the primary tank via a metallic tube. The tank’s oil moves when it’s loaded, so the oil’s temperature goes up and down. 

Buchholz Relay

Buchholz relay simultaneously functions with the conservator. Buchholz Relay does show when there are problems with a High Voltage distribution transformer, such as insufficient oil. Because of this, there exists an inappropriate oil flow that takes place between a tank and the transformer itself. 

Breather Unit

The breather unit has a silica gel that takes in the moisture oil produces. It transforms the oil from blue to pink and cannot take in moisture in the oil.

Oil Indicator

It shows the oil level in the conservatory unit.

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Temperature Detector

A temperature detector is a device used to track the oil’s temperature. If the oil’s temperature goes up at some point, then the distribution transformer shall stop operating. 

Pressure Relief Device

This device minimizes the High Voltage distribution transformer’s pressure to prevent it from exploding. 

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Thermal Relay

The thermal relay indicates the winding’s current temperature. 


This device is used to augment the efficiency of the cooling operation of the High Voltage distribution transformer.

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A bushing is used to connect the High Voltage distribution transformer’s windings connected within it with the aid of an external electric network. 

10KV High Voltage Distribution Transformer

What’s the Difference between HV Power Transformers and Distribution Transformers?

Unlike distribution transformers, HV Power Transformers execute the distribution and absorbing means of electricity. The voltage level of power transformers fluctuates between 756kV and 11kV. You see, power transformers have more MVA ratings as compared to distribution transformers. 

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HV Power Transformers generally have a greater voltage level than distribution transformers. 

Difference in Ratings

The average market ratings of power transformers include 400kV, 200kV, 66kV, and 33kV. Meanwhile, distribution transformers’ ratings average within 6.6kV, 3.3kV, 440v, and 230 volts.

The difference in Load Operations

HV Power Transformers are at total capacity for entire load operations, with few glitches. Distribution transformers operate in substantially lower levels of load operations. 

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Efficiency Level Difference

HV Power Transformers operate at 100 percent efficiency with a proportionate ratio of output/input. Besides, distribution transformers’ efficiency level is 50 to 70 percent, based on the All Day Efficiency calculation. 

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Difference in Uses

HV Power Transformers work in stations where power is generated, and substations produce power distribution. Distribution transformers produce energy within their own premises. 

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Size Difference

HV Power Transformers are significantly bigger than distribution transformers.

Critters Vulnerability

One thing that the distribution transformers and HV Power Transformers have in common is their critter vulnerability. Such a similarity that both transformers have produces power knockouts. Animals chew on and, in turn, destroy the parts of both distribution and power transformers

What are the Types of High Voltage Distribution Transformers?

Single Phase High Voltage Transformer

A single-phase distribution transformer is usually suitable for use for an outlet where it’s not needed to have a supply in a three-phase fold.

Your single-phase transformer is used most of the time to repair overhead distribution loads. In-home and industrial properties and other light commercially-based electric purposes. 

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Three-Phase High Voltage Transformer

This High Voltage Transformer distributes electricity from the primary outlet to a secondary power unit. A three-phase distribution transformer minimizes the voltage level of the primary power outlet. This transformer lessens the amount of voltage availability of the primary power outlet per the needs of users. 

To add to it, the functions of a three-phase High Voltage Transformer constantly change. This transformer operates in compliance with the individual requirements of each country. A three-phase transformer with a pad is primarily good for use in primary underground outlets. 

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High Voltage Distribution Transformer Connections

These connections vary based on the structural modifications of the distribution transformer enforced. A single-phase distribution transformer has one or two units of bushings in wye-shaped forms. The primary parts of these connections consume three, or four-wire wye connections gathered. 

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What are the Common Applications for a High Voltage Distribution Transformer?

As your High Voltage distribution transformer shifts its power from a high voltage power to a low voltage one. It’s used primarily on residential and commercial properties. This transformer separates primary and secondary windings. A distribution transformer spreads the electricity supply where access to power is difficult. Such a supply comes from the power plants. 

What’s more, a distribution transformer provides power to home and commercial properties, with voltage below 33KV and 440 volts to 220 volts. 

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Which Transformer is Used in Distribution?

Pad-Mounted transformer

A High Voltage pad-mounted distribution transformer has a locked steel cupboard that forms on a concrete pad. This pad-mounted transformer is seen in locations where there is no fenced protection. It’s also used in power distribution outlets within a primary electrical unit. To minimize the provision of primary voltage to users. 

One unit of a pad-mounted distribution transformer can serve users in many properties. The power level of this transformer is within 75 KvA and 5000 KvA and features outlets that have definite uses. 

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Key Features:
  • Few volume amounts. The setting is in default streamline. This feature allows the transformer to be placed above single and dual pole structures. 
  • No imminent danger threats against walking people and animals. Such a situation as a pad-mounted transformer is located almost 5 meters on top of the ground. 
  • A pad-mounted transformer can withstand harsh environmental and climate conditions.

What is a High Voltage Pole-Mounted Distribution Transformer?

A High Voltage pole-mounted distribution transformer is located atop an electric service pole above the primary head cables.

This transformer modifies high-level voltage to a low-level one. Approximately measuring 120/240 electrical volt levels. A pole-mounted transformer is usually used in rural neighborhoods, having voltage power ranging from 16 KVA to 100 KVA. 

More so, this small-sized transformer can easily fit a structure that’s of a single pole. This transformer is resistant to bad weather conditions in neighborhoods that are not easily accessible. 

This transformer’s tanks are resistant against eroding elements and accumulation of liquid. When located in offshore premises, a pole-mounted distribution transformer is zinc spray resistant. While a pole-mounted transformer located in substantially eroded areas uses a stainless tank.

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Are High Voltage Distribution Transformers Dangerous?

There are no studies or evidence that prove that exposing oneself near or fram from magnetic fields from transformers, power lines and other electrical sources cause any health effects.

In fact, many scientists believe that exposing oneself to low-level EMF’s near power lines is safe. However, the study with regards to health risks from these fields are still continuously researched. For now, there is simply no evidence for health risks being near high voltage transformers or power lines.

In short, you cannot get any diseases or health risks just by standing near or far from operating High Voltage Transformers.

What Causes High Voltages?

The most common cause or main cause for voltage surges in power systems are because of lightning impulses, and as well as switching impulses. But this is only one of the causes. For over voltage in power systems, this might be due to insulation failures, arcing ground, resonance, etc.

What Will Happen If The Voltage Is Too High?

The amount of current in a single circuit will depend on the voltage being supplied.

If the voltage is too high, the wire will possibly melt. Other devices might stop working or even burst into flames, causing an explosion afterward.

For high voltage transformers, they also have their limits as well. Too much voltage will cause the transformer to fail, but if the over voltage is within 1 to 10 percent past the limit, the transformer will most likely be okay and heat up a little more.

However, it is highly recommended that you do not use your transformers to operate past their limits for safety purposes. Too much voltage will destroy your transformer and endanger those who are near the transformer since it might burn up and explode.

What are the advantages & disadvantages of High Voltage Transformer?

Below are the advantages and disadvantages of high voltage Distribution Transformers. This section is specifically made for you to help you with your purchase decision.

Should you have any more questions or concerns about high voltage transformers or other transformers, do not hesitate to contact DAELIM’s team of professionals.

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Advantages of High Voltage Transformer

Here are the main advantages of using high voltage transformers.

Easy To Understand

Transformers are static devices, which means they have no moving parts in them but they do have the following:

  • Primary Winding
  • Secondary Winding
  • Magnetic core
  • Tank
  • Breather
  • Radiator
  • Buchholz Relay


The alternating current magnetic field created in one of the windings induces a current in the other winding that is proportional to the number of turns. High voltage transformers are used in electrical power systems to transfer power through electromagnetic induction from circuit to circuit with the same frequency level.

However, it is possible to encounter power losses, voltage drops, and waveform distortion during the process.

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Easy To Use

High voltage transformers are fairly easy to use, but for those of you who are worried that the high voltage transformer you are going to purchase will work differently, you can contact DAELIM to assist since they offer after-sale services.

Transformers will always be an important device in the power distribution system and power electronic system, which is why knowing how to properly use it is essential to utilize its benefits and for safety purposes.

High voltage transformers has the ability to step down high voltages in transmission as well.The same goes for increasing, but never go over its limit to avoid danger,

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Highly Efficient

Distribution, transmission, and power generation are the three fundamentals of today’s power system. High voltage transformers play a vital role in this, especially for high voltage applications, because their capabilities made electricity economic delivery at long distances possible.

When it comes to distribution, high voltage is stepped down for industrial, residential, and commercial use with distribution transformers.

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High voltage transformers can be used in various ways including stepping up and stepping down voltage levels, distributing power from one circuit to another, etc. 

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Disadvantages of High Voltage Transformer

Below are the following drawbacks of high voltage transformers, if there is an element that you find that is not suitable, then do reconsider your thoughts and check other high-quality transformers that are compatible to what your purpose of using one is.

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Requires cooling

Transformers have different cooling mediums. Some transformers only require forced air while other types use mineral oil. Both have their pros and cons as well. 

For forced air, it helps users save money since air is sufficient for cooling the transformer’s temperature. When it comes to using oil as the cooling medium, it is considered the most effective way of cooling. However, it will cost more because mineral oil itself can be expensive, as well as its maintenance. 

High temperatures in a transformer will degrade the longevity of the insulating materials used in the windings and structures. But with proper regulation, our transformer’s materials will remain in pristine condition. 

In fact, increasing the cooling rate of a transformer will increase the capacity. Regardless, you will need to spend for the cooling medium of your transformer, as well as do regular check ups for its maintenance. 

You can also take advantage of external cooling. This include heat exchangers, fans, oil pumps, and heat exchangers, which once again, will cost you more

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Works only in AC

HV Power Transformers are known to not pass DC. This means that transformers can be used to keep DC voltages on the output of an amplifier stage. For the AC signal, it is coupled through the HV Power Transformer between amplifier stages. 

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Outdated Technology

Even though high voltage Distribution Transformers are widely used, there are several characteristics of it that do not meet the standards of the modern distribution grid. This is why transformers are not advisable to be placed inside establishments. Even building fire codes are not compatible with transformers. 

To meet the requirements or standards of the modern distribution grid, a new design and build is required. This is why a lot of manufacturers are on the process of manufacturing an intelligent transformer.


A lot of high voltage transformers degrade or deteriorate in just a course of a year for various reasons, in which the majority of these reasons can be prevented with proper maintenance. With that being said, this is the reason why transformers can be a hassle, due to its regular check up routine. 

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As a High Voltage distribution transformers power up residential and commercial properties. Now you need this for your electrical home and industrial needs. 

Daelim came up with the term Electric, keeping in mind the Belefic Edge concept. Keeping this slogan concept in mind enables Daelim to produce only high-class electric items for its clientele. Edge is what Daelim brings to every product its competitors try to beat. 

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About Bin Dong

Hello, I am Bin, General manager of Daelim which is a leading transformer manufacturer. If you have problems when you are looking for the equipment, what you need to do is tell us.