what is Difference Between Power And Distribution Transformer?

Power transformers are made to change the voltage up or down so electricity can travel long distances more easily. On the other hand, distribution transformers are used to lower the voltage even more so that it is safe and ready to use in homes and businesses.

Key Difference Between Power and Distribution Transformer

1. Power transformers are made to be very efficient, aiming for 100% efficiency. Efficiency means how much output power you get compared to the input power.

2. Distribution transformers are less efficient, usually between 50% and 70%. Their efficiency is measured by something called All Day Efficiency.

3. Power transformers are mainly used in power plants and big transmission stations where electricity is sent over long distances.

4. Distribution transformers are placed closer to homes and factories to provide electricity for everyday use.

5. Power transformers are much bigger in size compared to distribution transformers.

6. In power transformers, losses from iron and copper happen all day long. But in distribution transformers, iron losses happen all day, while copper losses change depending on how much electricity is being used.

7. Where They Are Used:
Power transformers are used in the high-voltage transmission network to carry electricity over long distances. Distribution transformers work in the lower-voltage distribution network to send electricity to homes and businesses.

8. Voltage Levels:
Power transformers handle very high voltages like 400 kV, 200 kV, 110 kV, 66 kV, and 33 kV. Distribution transformers work with much lower voltages such as 11 kV, 6.6 kV, 3.3 kV, 440 V, and 230 V.

9. Load Operation:
Power transformers usually run at full load because the amount of electricity flowing through them stays quite steady. Distribution transformers, however, often work below full load because the electricity demand changes a lot during the day.

What is a Transformer?

A transformer is a device that helps change the voltage and current in an electrical circuit, without changing the frequency. Think of it like a bridge that safely moves electricity from one place to another, either by increasing (stepping up) or decreasing (stepping down) the voltage, depending on what’s needed. It doesn’t store energy or create it—it just transfers it in a smarter way. Transformers work using a simple idea called electromagnetic induction.

There are different types of transformers based on how they’re built and what they’re used for. Some common ones include:

• Auto-transformers
• Current transformers
• Potential transformers
• Power transformers
• Distribution transformers

While all these types are designed to either increase or decrease voltage and current, this explanation focuses on two important types: power transformers and distribution transformers.

What is a Power Transformer?

A power transformer is a special electrical device that helps move electricity from one place to another by changing its voltage level. It can either increase the voltage (step-up) or decrease it (step-down), depending on what’s needed. This change helps electricity travel long distances more safely and efficiently.

What makes a power transformer unique is that it has no moving parts. It quietly does its job without any noise or motion. Only a few small parts, like tap changers, may move occasionally, but that doesn’t happen during normal use.

Power transformers work only with AC (alternating current) electricity. They use a simple principle called mutual inductance, where two coils help pass energy from one side to the other. Even though the voltage and current change, the total power and frequency stay the same. That means the amount of electricity being sent and received doesn’t change — just the way it flows.

These transformers are mostly found in power stations — the places where electricity is made. They help send that electricity over long distances to homes, offices, and factories. They also help connect different power stations that may not use the same voltage levels. This connection makes the whole power system stronger and more reliable.

In short, without power transformers, we couldn’t send electricity across cities and countries. They are the silent heroes behind every light switch we flip and every device we charge.

Power transformers are usually very large. They are built to handle very high power levels—usually more than 200 MVA (that’s 200 million volt-amperes!). Because of their big job, they often take up a lot of space and can weigh hundreds of tons. You’ll find these in big power stations or transmission systems that carry electricity over long distances.

• Core and winding size: These are thicker and bigger in power transformers to handle large amounts of electricity.
• Cooling system: These often need oil and special cooling systems with fans or radiators to keep from overheating.

Ratings:

• Power Rating: Usually starts from 1 MVA and can go above 1000 MVA.
• Voltage Rating: High voltage levels (used in transmission lines).
• Frequency: Normally 50 Hz or 60 Hz, depending on the country.
• Impedance: This is a small percentage that tells us how much voltage drops when the transformer is under load.
• Temperature and Cooling Class:
  • For smaller power transformers: ONAN (Oil Natural Air Natural)
  • For larger ones: OFAF (Oil Forced Air Forced)

What is a Distribution Transformer?

A distribution transformer is a machine that helps bring electricity safely into our homes, schools, shops, and offices. The electricity that comes from power plants is very strong — too strong for us to use directly. That’s where the distribution transformer comes in. It takes this high-voltage electricity and turns it into a lower, safer level that we can use in our everyday lives.

These transformers are usually placed on poles or in small boxes near streets and buildings. They are the last step in the journey of electricity before it reaches us. They don’t change the type of electricity — just its strength, so it’s ready for use.

A distribution transformer is a special type of electrical device used in power systems. Its main job is to reduce high voltage to a lower, safer voltage that we can use in homes, offices, and factories.

You can think of it like a bridge that connects the powerful electricity from power stations to the appliances we use every day. It takes the high voltage coming from power lines and steps it down to a level that’s safe and useful for lights, fans, machines, and more.

This transformer is called a step-down transformer because it lowers the voltage. It works with both single-phase and three-phase systems, depending on the need.

Distribution transformers come in different voltage levels like 11,000 volts (11 kV), 6,600 volts (6.6 kV), 3,300 volts (3.3 kV), 440 volts, 120 volts, and even 110 volts.

These transformers are carefully designed to work best when they are carrying about 60% to 70% of their full load. This makes them very efficient and helps save energy.

In short, a distribution transformer quietly works behind the scenes to make sure we get just the right amount of electricity—safe, steady, and reliable.

Types of Distribution Transformers

Distribution transformers help deliver electricity safely and efficiently by adjusting voltage and sharing power where it’s needed. They come in different shapes and sizes depending on how and where they are used. Here are four main types of distribution transformers, explained simply:

1. Single Phase Transformer

This type is made for single-phase power systems, which means it handles one set of electric current. The transformer connects to a three-phase power supply but uses only one phase at a time. It has one secondary coil that sends electricity to homes or small businesses. The voltage on the output side depends on how the coils are set up inside the transformer.

2. Three Phase Transformer

These transformers are used where three-phase power is needed, such as big buildings or factories. They have three separate coils, each working with one phase of electricity. These coils are arranged so they share a neutral wire, which helps balance the power. The voltage in each coil can be different but is carefully controlled to work together smoothly.

3. Pad-Mounted Transformer

Pad-mounted transformers sit on concrete pads at ground level. They are often used where it’s better to keep wires underground, like in neighborhoods or small business areas. Since the wires are buried, there’s less chance of damage from weather or accidents. These transformers are good for places where only one or two phases are needed.

4. Pole-Mounted Transformer

These transformers hang high up on poles, usually along streets or rural areas. They are easy to reach for repairs or maintenance. Pole-mounted transformers can also come with extra parts like lightning protectors to keep them safe during storms. They help deliver electricity where it’s hard to run underground wires.

Difference Between Power and Distribution Transformer

what is Difference Between Power And Distribution Transformer?

Definition

A distribution transformer is a type of transformer that helps bring electricity to our homes and offices. It takes high voltage electricity and changes it into a lower voltage that is safe and useful for everyday things like lights, fans, and appliances.

On the other hand, a power transformer is much bigger and stronger. It is used where electricity travels over long distances. This transformer handles very high voltages and helps move large amounts of power from one place to another, like from a power station to a city.

Purpose of Transformers

A distribution transformer helps bring electricity safely to your home or business. It takes the high voltage electricity that travels through big power lines and reduces it to a much lower voltage that we can safely use in our lights, fans, TVs, and other everyday appliances.

On the other hand, a power transformer works earlier in the process. Its job is to take electricity from power stations and increase its voltage. This high-voltage electricity can travel long distances through big wires without losing much energy. Once it reaches near the cities or towns, other transformers reduce the voltage again for safe use.

In short:

Power transformer = Raises voltage to send electricity far away.
Distribution transformer = Lowers voltage so we can use it.

Leakage Reactance in Transformers

In transformers, leakage reactance is a natural part of how they work. It affects how well energy moves from one side of the transformer to the other.

• Distribution transformers are made to send electricity to homes, schools, and small buildings. They need to be very good at giving a steady and smooth supply of power. That’s why they are built with low leakage reactance. Low reactance means less energy is lost along the way, and the voltage stays stable for everyday use.

• Power transformers, on the other hand, are used in big power stations and long-distance power lines. They deal with very large amounts of electricity. These are designed with high leakage reactance on purpose. It helps protect the system during short circuits and controls the flow of current during sudden changes. This makes them stronger and safer for heavy-duty work.

In short, distribution transformers focus on steady delivery, while power transformers focus on strong protection. That’s why their leakage reactance is designed differently.

Location of Transformers

Distribution Transformers are placed on poles close to where electricity is used, like homes, shops, and small factories. These transformers are installed near the end-users to make sure electricity is delivered at the right voltage and with minimal loss.

Power Transformers, on the other hand, are set up at power stations and large substations. These are used in the early stages of electricity travel — right after it’s generated and while it’s being sent across long distances through high-voltage transmission lines.

In short:

• Distribution Transformers are found near your home or business.
• Power Transformers are placed at big power plants and main transmission centers.
  
  

Function

In real life, distribution transformers are mainly used to reduce high voltage and make it lower so that homes, schools, shops, and small factories can use it safely. They take the electricity coming from big power lines and step it down to a level that is safe and usable for everyday things.

On the other hand, power transformers are mostly used to increase the voltage. This happens when electricity needs to travel long distances. Higher voltage helps it move faster and more efficiently through power lines. But power transformers can also step down the voltage when needed — for example, before it reaches the distribution transformer.

Power Rating of Transformers

Transformers are used to transfer electrical energy from one place to another, and they come in different types based on how much power they can handle.

Distribution Transformers
These are the transformers you often see near homes and small buildings. They are made to handle less power—usually less than 200 MVA. They help bring electricity from the big power lines down to the level we use every day.

Power Transformers
These are much bigger and are used in power stations or large industrial areas. They carry a power rating of more than 200 MVA. Their job is to move large amounts of electricity over long distances.

Voltage Rating

Different types of transformers are used for different purposes, and one of the main differences between them is their voltage rating.

Distribution Transformers

These are the transformers you see near homes, shops, and small factories. They help bring electricity from the big power lines down to a level we can safely use. The voltage ratings for distribution transformers are usually:

• 11,000 volts (11 kV)
• 6,600 volts (6.6 kV)
• 3,300 volts (3.3 kV)
• 440 volts (V)
• 220 volts (V)
• 110 volts (V)

These voltages are suitable for homes and local areas. The lower the voltage, the closer it is to being ready for everyday use.

Power Transformers

These are used in large power plants and substations. Their job is to carry electricity over long distances at high voltages. This helps reduce energy loss during the journey. The voltage ratings for power transformers are much higher:

• 33,000 volts (33 kV)
• 66,000 volts (66 kV)
• 132,000 volts (132 kV)
• 220,000 volts (220 kV)
• 440,000 volts (440 kV) or even more

These transformers are powerful and designed to handle large amounts of electricity.

In Simple Terms:

• Distribution transformers give us electricity at a level we can safely use.
• Power transformers carry electricity over long distances at very high voltages.

Winding Configuration

In a distribution transformer, the main (primary) winding is connected in a delta shape. The second (secondary) winding is connected in a star shape. This star connection gives us a neutral point, which is important when we need single-phase power, like in homes and small offices.

In a power transformer, both the primary and secondary windings are usually connected in a delta shape. But there are some special situations—like in power plants—where the primary winding is connected in a star shape and the neutral is connected to the ground (earthed). In these cases, the secondary side is connected in delta.

Number of Primary and Secondary Windings

A distribution transformer has one primary winding. On the secondary side, it can have one winding or more than one, depending on how it is used. Sometimes, the secondary winding is “tapped,” which means it can provide different voltage levels from the same winding.

On the other hand, a power transformer usually has one primary winding and one secondary winding. It is more straightforward because it is designed for sending electricity over long distances, without the need for multiple voltage levels.

Size

A distribution transformer is small in size. It is made to fit easily on poles or near homes where electricity is used.

A power transformer is much bigger. It is used in large power stations and needs more space because it handles a lot more electricity.

Operation During Light Loads

Distribution transformers stay connected all the time, even when the electricity demand is very low. This means they keep working at light loads for most of the day.

On the other hand, power transformers are usually turned off or disconnected when the load is light. They only operate when there is a higher need for electricity.

When They Work

Distribution transformers work all the time — both when there is electricity flowing through them (load) and when there isn’t (no-load). On the other hand, power transformers only work when electricity is flowing (load).

Load Fluctuations

Distribution transformers are built to handle big changes in the amount of electricity they carry. They can easily adjust when the load goes up or down a lot. On the other hand, power transformers usually deal with smaller changes in the load, so their design reflects that.

Flux Density in Transformer Cores

In transformers, flux density is an important factor. A distribution transformer usually has a lower flux density in its core. This means the magnetic field inside it is not very strong. On the other hand, a power transformer has a higher flux density. Its core carries a much stronger magnetic field to handle bigger loads.

Operating Conditions of Transformers

Distribution transformers usually work with less power than their full capacity. This means they don’t always use all the energy they can handle.

On the other hand, power transformers are made to work at their full capacity most of the time. They carry the maximum load they are designed for.

Maximum Efficiency

Distribution transformers work best when they carry about 60 to 70% of their full load. This means they use energy very efficiently in this range. On the other hand, power transformers reach their highest efficiency when they are running at full load.

Leakage Reactance in Transformers

Transformers have something called leakage reactance, which affects how electricity flows inside them.

In distribution transformers, the leakage reactance is kept small. This helps the electricity move smoothly and efficiently to homes and businesses.

On the other hand, power transformers are made with higher leakage reactance. This design helps protect the transformer and manage the flow of power better when dealing with big electrical loads.

Voltage Regulation

Distribution transformers help deliver electricity to homes and businesses with steady and reliable voltage. This means the power they provide stays strong and stable, so your devices work properly without flickering or damage. For these transformers, keeping the voltage steady is very important.

On the other hand, power transformers, which are used in big power plants and electrical stations, don’t focus much on voltage regulation. Their main job is to move large amounts of electricity over long distances, so voltage stability is not their top priority.

Applications of Transformers

Distribution Transformers:
These transformers help deliver electrical power safely and reliably to homes, shops, and small businesses. They take the electricity from the local power lines and make sure it reaches consumers at the right voltage to use.

Power Transformers:
Power transformers are mainly used in places like power plants and large substations. They either increase (step-up) or decrease (step-down) the voltage of electricity to make it easier and safer to send over long distances or to prepare it for local use.

Detailed Explanation of Transformer Parameters

Let’s break down the important parts of a transformer in simple words so anyone—even a child—can understand.

1. Rated Voltage

• Primary (High Voltage or HV) Side:
  This is the side that receives electricity from the power grid. The voltage here is usually 11,000 volts (11 kV), 22,000 volts (22 kV), or 33,000 volts (33 kV). This depends on how far the electricity has to travel and what the network needs.
• Secondary (Low Voltage or LV) Side:
  This is the side that sends electricity to homes and businesses. For a three-phase supply (used in industries and larger buildings), it gives 400 volts. For a single-phase supply (used in houses), it gives 230 volts.

2. Voltage Tolerance

Electricity is never exactly the same all the time. There are small ups and downs. So, transformers are designed to handle that:

• On the primary side: It can take up to 10% more or less than its rated voltage.
• On the secondary side: It tries to stay within 5% of the normal voltage so your lights and machines work properly.

3. Tap Changer Range

This is like a fine-tuning tool inside the transformer.

If the voltage goes too high or too low, the tap changer adjusts it back to normal. It can usually increase or decrease the voltage by 5% or 10%, in small steps of 2.5% each. This helps keep the power steady.

4. No-Load Voltage Ratio

This simply means the voltage difference between the primary and secondary when nothing is connected—no machines, no lights.

Example: If a transformer is marked 11 kV/400 V, that means it reduces 11,000 volts down to 400 volts when nothing is being used.

5. Impedance Voltage (Z%)

This tells us how much the transformer resists the flow of current inside itself. It’s written as a percentage—normally between 4% to 6%.

A higher impedance means the transformer gives better protection during a short circuit, but it also reduces the voltage more under heavy load.

6. Phase Configuration

This shows how the wires are connected inside the transformer:

• Primary side: Can be Delta (Δ) or Star (Y) shape.
• Secondary side: Usually Star (Y) with a neutral wire, which makes it safer and more useful for homes and buildings.

7. Frequency

This is how fast the electricity “vibrates” every second.

• In Europe and Asia, it’s 50 times per second (50 Hz).
• In North America, it’s 60 times per second (60 Hz).

The transformer must match the frequency of the country it’s used in.

8. Voltage Regulation

As you use more electricity, the voltage might drop. Voltage regulation tells how well the transformer keeps the voltage steady.

Good transformers can keep the voltage change within 2% to 5%, even if the load goes up or down.

9. Insulation Level

Electricity needs to be handled safely. The wires and parts inside the transformer are covered with special material called insulation to stop electricity from jumping or leaking.

• On the primary side (high voltage): Needs stronger insulation, like 28 kV for an 11 kV transformer.
• On the secondary side (low voltage): Needs lower insulation, like 3 kV, since the voltage is much less.

FAQ