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1. Definition of Power Transformer and Distribution Transformer

What is a Power Transformer?

In case you didn’t know yet, a power transformer is a static electrical machine.

Energy transformers play a crucial role in the power distribution system.

From a standard standpoint, the transformers are composed of different major parts:
  1. Secondary winding
  2. The primary winding and;
  3. Core

What is a Distribution Transformer?

On the other hand, a distribution transformer can transformers the voltage level to the final value.

Therefore, it’s being prepared for immediate use.

It steps down the voltage at a particular point within the system.

2. Purpose Difference of Power Transformer and Distribution Transformer

As mentioned earlier, distribution transformers are a kind of a step-down transformer.

They lessen the enormous amount of voltage which comes from the power plant to the least value.

Thus it can be efficiently utilized to transformer the electric current down the line further.

They present the final voltage transformation before the electric power is transported to the circuit through the distribution line.

In short, distribution transformers are used only for distribution purposes.

On the other hand:

Power transformers are the device which is employed within the power distribution industry.

Their role is to send an electric current from low to high voltage levels.

In a nutshell:

Power transformers are used for transmission and receiving purposes.

3. Voltage Parameters

The step-down application is composed of 400 kV, 200 kV, 110 kV, 66 kV, and 33 kV.

Typically, they are generated more than 200 MVA.


The distribution transformers are utilized for lower voltage distribution networks as a means to end user connectivity.

They are composed of 230 V, 440 V, 3.3 kV, 6.6 kV, and 11 kV, and are rated less than 200MVA.

4. Size Difference

Typically, the size of power transformers is bigger as compared to its counterpart, distribution transformers.

Plus, the installation process is very complicated and challenging.

On the contrary:

Distribution transformers are much smaller and lighter compared to power transformers.

The installation process is simple as well.

5. Usage Difference

Power transformers are utilized for transmission as a step up devices.

So the l2r loss can be lessened for particular power flow.

Such transformers are made to use the core to the maximum and will work much clear to the knee point of the B-H curve.

That brings down the mass of the core massively.


Such transformers have the matched copper losses and iron losses at peak load.

But wait! There’s more!

Distribution transformers can’t be designed like that.

Thus, the all-day-effectiveness come into picture while making it.

It varies on the standard load cycle for which it needs to supply.

6. Designed Efficiency

Power transformers are intended to work for commercial uses.

That reason accounts to its load setting at maximum.

What’s more:

They are made for maximum efficiency of 100%.

Because they have to offer maximum efficiency, they use heavy load which guarantees their complete load bearing capacity.

When we talk about the distribution transformer:

The power of these transformers can be evaluated through its load bearing efficiency within the day.

That’s because it is made to serve a maximum of 60% to 70% of the load.

You see:

There’s a full load during peak hours of the day, and often, it turns out to be idle.

7. Load Fluctuations Difference

You need to bear in mind, that power transformers are there to offer continuous power supply.

This power supply is at all times free of value and disturbance.


They have the least load fluctuations.

You are aware that distribution transformers are intended for residential supply most of the time.

And so:

Distribution transformers could have regular load fluctuations.

8. Metal Loss

The power transformer incurs iron and copper losses within the day.

That’s because the large current is continuously passed within the transformer.

Nevertheless, in the distribution transformer, the iron losses happen for twenty-four (24) hours.

As you can see, the copper losses are based on the load cycle.

9. Considering Time & Operation

The average loads of power transformers are closer to full load or fully loaded.

And such are made in such a fashion which maximum efficiency at a full load state.

Such is independent of time.

Thus, in measuring the efficiency, the power basis is sufficient.

What about the distribution transformer?

As explained earlier:

The average loads for distribution transformers are 75% of full load.

They are made in such a fashion which maximum efficiency happens at 75% of full load.

As such are time-dependent, the entire day efficiency is determined to measure efficiency.

10. Winding Connection Type of Power Transformer and Distribution Transformer

The windings in power transformer can be linked to a double star or loop (Z).

The variance among such types of couplings is in the:
Current and;
Line and phase values of voltage


The 3-pillars of 3-phase distribution transformers are active.

That denotes that if the transformers are working, they are surrounded by winding wherein the current will flow.

In brief:

The power transformer has primary windings which are linked in the star.

The secondary is connected to a delta connection.

The distribution transformers, however, the primary bound is connected the delta.

The secondary is connected in star type connection.

11.Types of Network

Distribution networks are utilized in the distribution network of low voltages.

Power transformers are utilized in transmission network of high voltages.

12. Flux Density

In power transformer, the flux density is at all times higher.

If you compare to the power transformer, the distribution transformer’s flux density is very low.

13. Designing of the Core

Regarding designing of the core, there are also vast differences between power and distribution transformers.

Did you know that power transformers are created to employ the core for maximum?

It will work close to the saturation point of the B-H curve.

Its job is to help bring down and lessen the mass core.

For the meantime:

As compared to power transformers, the flux density of the distribution transformer is somewhat low.

14. The Number of Input and Output


A power transformer features 1 secondary and 1 primary.

It also has one output and one input.

On the other hand, a distribution transformer might have one primary and one divided.

It is also called as “tapped” secondary, or two or more secondaries.

15. The Transmission Line Difference

Now, what about the line difference in the transmission?

What is the difference now?

In case you didn’t know yet:

The power transformer connected in the substation end of the transmission line is Star-Delta.

It is for the purpose of a step down the voltage level.

For the moment:

In the case of a distribution transformer, it is customarily utilized in 3-phase step-down distribution transformer.

In short:

They are in Delta-Star transmission line.

16. Judgement Standard

The performance of the power transformers is usually judged by commercial efficiency.


The performance of a distribution transformer is judged from all – day – efficiency.

17. Configuration Difference

When we talk about the structure:

A power transformer features:
one primary and;
one secondary setup with one input and output pin

When we talk about distribution transformer, you will understand that it might have:
a single primary and;
a “tapped” secondary.

More than one secondary, for example, two or more of them.

18. Force Difference

Power transformers are no doubt have massive electric resonance.

As a result:

Their flux density is at all times higher compared to distribution transformers.

And so is their magnetic repulsion.

You see:

Distribution transformers could not match that criterion.

19. Voltage Fluctuation

If we explained about voltage fluctuation, you’d notice differences as well.

Did you now that power transformers provide continuous power supply free of disturbance and value?


You can expect smooth performance because they have the least fluctuations.

Unfortunately, that is not the case with a distribution transformer.

That’s because they are intended for residential supply most of the time.


They can have consistent load fluctuations.

20. Types

Distribution transformers are categorized further into 2 types:
liquid transformers and;
dry type transformers

The dry type distribution transformers are famous for their efficient usage in applications where fire protection and safety is needed.

The liquid distribution is popular for its efficient power distribution ability and compact size.

Both types have its ways of being cool.

Dry type features an internal convection air flow for the core cooling.

The liquid transformers employ thermal conduction to eliminate heat with the tank walls.

Similar to distribution transformers, power transformers are also categorized into 2 kinds:
Generator Step-up Units and;
Liquid units

Both of these two can be employed together with phase shifters to optimize power transmission and balance the power flow.

21. Cooling

In terms of cooling:

Power transformers take advantage of cooling via high levels of insulation.

On the other side of the story:

Distribution transformers are cooled with the help of internal convection air flow and thermal conduction.

22. Applications

Power transformers are created for applications along with power requirements of more than 10 MVA.

On the flip side:

Distribution transformers are created for applications along with power requirements which is below 10 MVA.

23. Load Resistance

Power transformers, as what the name tells are power loaded.

For instance:

They sometimes work at virtually full load capacity.

That’s because heavy current utilization is needed.


When it comes to a distribution transformer, typically the load is somewhat light within the day.

That’s because it works decently for domestic purposes.


They do not need substantial current supply.

To sum up everything:

You need to bear in mind that the transformer is fundamentally an energy converter.

Electric power is transmitted from the main to the secondary winding, along with only changes in the size of current and voltage.

The efficiency of transmission of power or electricity is relatively high.

Plus, in case of power transformers is virtually 100%.

Power transformers have the power to step up the voltage to send it across more extended distances.

Simply put, the losses raise as the voltage lowers in transmission lines.

Distribution transformers are considered a step-down.

They middle-low voltage range transformers.

They lessen the voltage to be utilized where required.

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