The Complete Guide to Telephone Pole Transformer

Although telephones are no longer in high demand, this does not affect telephone pole transformers since telephone pole transformers have a lot of purposes. When it comes to the pole mounted transformer connections, there are plenty of them, Pole-mounted transformer installation takes time and accuracy because telephone pole transformer explosions do happen.

With the help of DAELIM, a professional telephone pole transformer manufacturer in China, you will be able to understand all these topics.

Furthermore, DAELIM aims to assist you with your purchase decision as well.

But before going through what telephone pole transformers are capable of, it is important to know the basics first.

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Pole Power Transformer

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What is a Pole Transformer?

From the name itself, telephone pole transformers, this type of transformer belongs to the category of pole transformers, which are public distribution transformers that have the shape of a barrel.

Moreover, this type of transformer is mounted to a utility pole.

This means that this transformer is above-ground and can be safely exposed to the public but pole-mounted transformer installation must be observed to avoid telephone pole transformer explosion.

pole-mounted transformer and single phase transformer
pole-mounted transformer and single phase transformer

How Can Pole-mounted Transformers be Distribution Types?

Distribution transformers are transformers that perform the very last voltage transformation in a distribution grid.

Moreover, distribution transformers have the ability to convert voltages that are used in transmission lines to one suitable consumer and commercial use. (Normally down to 240 volts)

Furthermore, they are widely used in transmission systems and electrical power distribution systems as well.

This type of transformer also has the highest power in terms of voltage-ampere ratings, and they also have the highest continuous voltage rating.

When it comes to the power rating, this is normally determined by what type of cooling methods are used in the transformer.

What Transformer is Used in Distribution?

DAELIM Three-phase distribution transformers are used to hold electrical energy from the main distribution circuit to a minor distribution circuit.

This type of transformer is also able to transmit the current to a secondary distribution circuit.

Moreover, this reduces the voltage of the primary distribution circuit.

What is the Main Difference between Distribution Transformers and Power Transformers?

You may be wondering why telephone pole transformers are not power transformers, that is because power transformers are primarily used for transmission networks with a significantly higher voltage.

On the other hand, distribution transformers are focused on distribution networks that are defined by lower voltages.

Furthermore, distribution transformer ratings usually range from 11kV, 6.6 kV, 3.3 kV, 440V, 230V, etc.

Different Types of Public Transformers

Although the majority of transformers are commonly located at power plants and other high-voltage areas, there are a few types of transformers out there that can be safely placed in public.

However, this does not mean that all outdoor transformers are safe to be exposed outside.

This simply is not the case because most outdoor transformers do not pass the fire code of buildings and other establishments.

This includes telephone pole transformers since they can be located outdoors, but they are definitely not safe to make contact with.

This is also the reason why they are mounted to a pole instead of being mounted on the ground.

Pad-mounted Transformers

Speaking of ground, ground-mounted transformers or pad-mounted transformers also belong to the category of outdoor transformers since they are located outdoors but unlike pole-mounted transformers, this type of transformer is basically a transformer that sits on a solid pad that can be made out of wood or concrete.

Moreover, pad-mounted transformers are not like pole-mounted transformers that have a lot of pole-mounted transformer connections.

Pad-mounted transformers basically looks like a huge locker that is enclosed in a metal housing to prevent outside elements (e.g., people, animals, debris, calamities, etc.) from disturbing its operation.

Single Phase and Three Phase Pad-mounted Transformer From Daelim
Single Phase and Three Phase Pad-mounted Transformer From Daelim

Pole-mounted Transformers

When it comes to pole-mounted transformers, as mentioned, they are distribution transformers that have a shape of a barrel, and they have numerous pole-mounted transformer connections linked to their bodies for distributing electricity to the consumers.

Pole-mounted transformers are also known for their single-phase functions.

A single-phase transformer is basically a type of power transformer that primarily uses single-phase alternating current or most commonly known as A.C.

This means that the transformer relies on a voltage cycle that operates in a unified time phase.

In other words, the ratio of the primary windings or input windings to secondary or output windings will determine the change in current.

What is a Telephone Pole Transformer?

So, what is a telephone pole transformer? A telephone transformer either means there is a telephone on a pole transformer or a pole transformer that has pole-mounted transformer connections associated with telephone lines.

This means that this type of transformer makes phone calls possible through their distribution networks.

How does a Telephone Pole Transformer Work?

When it comes to how telephone pole transformers work, in normal cases, electricity will flow to the transformer on the high-voltage side of where it goes into a coil of wire.

Usually, there is a wound around an iron core.

As electricity flows through the coil, it is expected that it will create a magnetic field that will induce a voltage in the other coil.

Each coil basically has a different number of turns.

What is Inside a Telephone Pole Transformer?

Although telephone pole transformers are small, this does not mean that it will include accessories like surge arresters or protective fuse links.

Self-protected transformers also include an internal fuse and surge arrester.

Other transformers also have these components that are mounted separately that are outside of the tank.

Telephone pole transformers are also considered as a static device.

Meaning, this transforms electrical power from one circuit to another without disturbing or changing the frequency.

They also have the ability to increase or decrease the voltage that is corresponding to the decrease or increase in the current.

Inside a Telephone Pole Transformer
Inside a Telephone Pole Transformer

What does a Telephone Pole Transformer Do?

A telephone pole transformer also has the ability to convert higher voltage electricity that is carried by primary wires and lower the voltage for the consumers to safely use it. Guy wires are responsible for stabilizing utility poles.

Ground wires also run the entire length of the pole, and it also directs any electricity on the pole safely into the ground.

How much does a Telephone Pole Transformer Cost?

In terms of how much a telephone pole transformer cost, the average price for them is between $3,000 to $7,000 each, but this will depend on how much electricity is there to handle.

For the best quotes and services, DAELIM will gladly accommodate your needs.

power pole transformer
power pole transformer

What are the Requirements for Installing Telephone Pole Transformers?

When it comes to the pole-mounted transformer installation, there are plenty of factors to consider first.

Since transformers are important for bringing the right amount of voltage from one source to another, it is expected for the pole-mounted transformer installation to be in an appropriate environment.

This is to make sure that the telephone pole transformer is safe and secure.

A single mistake during the installation could lead to so many dangerous events such as an electric shock.

This is why before setting up and connecting a transformer in your vicinity, check the following factors below first.


A safe area for your telephone pole transformer is crucial for liquid-filled transformers that include their location.

These transformers must be located in an area that passes the common fire hazard specifications.

Furthermore, the position of the telephone pole transformer should be placed in a way that there is no possibility of a leakage.


Earthing or grounding is specifically for pad-mounted transformers and other types of transformers that are placed on the ground.

To begin with, the tank should be permanently grounded with a correctly sized and proper installment of permanent ground after its placement.

This is to be done when further inspection is carried out or after the transformer’s assembly.

Wiring Connections

Have you noticed that some pole mounted transformer connections are messy?

That is because of unorganized work.

We in DAELIM practice proper cable management that covers wires with plastic or wood molding for distribution lines connected to telephone pole transformers.

The guy wires are also critical for protecting the pole line from damage that is caused by the strain of line conductors, calamities, debris, pole-mounted equipment, etc.


As mentioned, there are many types of transformers out there that can be mounted to a single pole as long as the weight of the transformer is manageable or equally distributed throughout the total weight of the safe limit of the pole.

Sub-100 kVA single-phase transformers are also mounted above the secondary mains.

For transformers that are larger than 100 kVA, a platform or a pad mount is recommended.


When it comes to the cooling medium of transformers, there are basically two types of insulation: oil and forced air.

In terms of forced air insulation, these are primarily used by dry-type transformers, while oil or mineral oil are used by oil-filled transformers.

Dry-type transformers ventilation is crucial and there should be access to clean and dry air to cool the transformer while it is operating.

There should be enough space allocated as well for heat to dissipate easily.


Humidity is also a factor you need to consider before you install your telephone pole transformer.

This is because of rain, which means there should be regular maintenance involved especially for liquid-filled transformers like telephone pole transformers.

If the humidity exceeds 70%, it is recommended that air should be consistently used to pump into gas space for 20-30 minutes before maintenance servers can enter the tank.

Fluid check

A fluid check is also important in terms of inspection.

If the insulating liquid needs to be drawn, you will need to make sure that all equipment like pumps and hoses should be clean and dry, this is to make sure that the equipment has been used for any other liquid.

Cleaning contaminated items thoroughly is also advised before using since you must also have clean and dry storage options for retaining the liquid and also filter the liquid before filling the tank with oil again.

You must also make sure that the liquid level should not go below the top of the windings in the process of rearranging or removing it.

Maintenance of the Pressure

A pressure that is positive is required at all times, this means it involves low ambient temperatures as well.

To allow this, there must be a sufficient gas pressure that is maintained.

Pressure vacuum gauges also show pressure variations with ambient temperature, which must be monitored consistently as well.

Overall Maintenance

Of course, maintenance should also be considered for the overall transformer.

All pole mounted transformer connections as well as the bushings should be checked for tension of gaskets, and draw lead connections as well along with the electrical clearances.

There should be an inspection for the removal of all tools as well. Keep in mind that the effort you put into maintaining your transformer will determine its overall performance and longevity.

If you do not have a standard transformer, that means that you are not protected from all hazards, so be sure to get a premium transformer that is from a trusted and reliable company.

How Long do Telephone Pole Transformers Last?

Telephone pole transformers can have a life expectancy of up to 20 to 25 years or even more than 50 years if properly taken care of.

Just make sure to follow the advice that DAELIM has given.

Has there been any Telephone Pole Transformer Explosions?

Although rare, telephone pole transformer explosions do happen for several reasons.

The most common reason why is because of lightning strikes during a strong rain or typhoon.

Lightning strikes can easily damage the wiring and transformer equipment, or the overall transformer itself.

Extreme weather conditions like strong winds and rain can also cause trees to fall on transformers, which can cause explosions.

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.

Custom Telephone Pole Transformer

When you need to find more than just existing transformers, Daelim’s Transformer Service Center can help you design and produce distribution transformers that meet your unique needs.

We have our own factory and a professional team of engineers, which can design and modify application requirements that meet all your conditions.

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