The Complete Guide to Medium Voltage Transformers

Power distribution involves the transmission and transformation of electricity in different voltage levels. Transformers play a crucial role in power distribution from power plants of high voltage levels to households of lower voltage levels.

Distribution transformers are specifically the transformer type necessary for this distribution of power. Under normal circumstances, distribution transformers involve medium ranges of voltages.

Most of these transformer types are referred to as medium voltage transformers, and that’s the topic of this article. Here, you learn about the importance and all relevant information about medium voltage transformers.

Now, if you are looking for medium voltage transformers and similar electrical products, you better make a note of DAELIM. Jiangsu Daelim Electric Co. Ltd launched their transformer brand to answer the ever-changing market demands for high-quality transformers.

Daelim Belefic is synonymous with excellence and cost-efficiency and has been a renowned product for over 15 years. The company makes its products under compliance with ANSI, IEEE, CSA, and IEC standards.

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What Are Medium Voltage Transformers?

Medium voltage transformers are transformers operating in the voltage range of 2 kV to 35 kV. This voltage range is common for the distribution transformers, which generally classify them as medium voltage types.

The medium-voltage distribution transformers are responsible for stepping down electricity in usable customer ratings. It provides final voltage transformation, which defines it as the final gateway for energy distribution.

Typically, several homes can be connected to one distribution transformer. However, there are cases wherein customers request a much larger amount of power. In this scenario, they may connect directly to the distribution level or on sources designated by the power provider.

Customers with special requirements can connect to the secondary distribution lines through service drops or by bi-directional transmission.

The Standard Medium Voltage Transformer Ratings And Sizes

As aforementioned, the standard range of medium voltage transformers is around 2 kV to 35 kV.

However, transformer sizing comes in a different unit which is kVA.

The kVA unit represents kilovolt-amperes or 1,000 volt-ampere ratings.

It is the amount of voltage multiplied by the current in amperes.

For example, a transformer with a 1.0 kVA rating implies it can handle 100 volts at 10 amps of current.

Manufacturers can have varying transformer sizes that they distribute.

It is typical to have a 75–5,000 kVA range concerning the range for medium voltage transformers.

For specificity, it is imperative to consult with your manufacturer or supplier which rating applies best to your application.

What Are The Differences Between LV, MV, HV, and EHV Transformers?

Voltage rating classification revolves around the terms LV, MV, HV, and EHV. The respective terms represent the following:

LV or Low Voltage

Low voltage ratings are within the ranges of 50 volts to 1000 volts or 1 kV. It is the typical range for household and small, medium applications.

MV or Medium Voltage

This voltage range is within 2 kV to 35 kV. It is the range common in power distribution lines and medium industrial needs.

HV or High Voltage

Meanwhile, the high voltage range is around 35 kV to 245 kV. This voltage range is what substations or power transformers use to operate.

EHV or Extremely or Extra High Voltage

As the name suggests, these are extreme voltage ratings exceeding the 245 kV mark.

What Are The Common Types Of Medium Voltage Transformers?

Pad-Mounted Transformers

The pad-mounted transformer is a ground-installed distribution transformer encased in a metal cabinet atop a small concrete pad.

These are distribution transformer types prominent among residential subdivisions and are power-efficient, tamper-resistant, and compact.

They are ideal for applications where public safety is paramount.

The pad-mounted transformers can either be a single-phase or three-phase system.

Depending on this phase design, it can cater to varying amounts of loads.

Three-phase pad-mounted transformers offer higher load capacities and are typically oil-submerged.

This same regard in the cooling mechanism is a consideration as oil contents can be hazardous if mismanaged.

Manufacturers typically produce pad-mounted transformers within the range of 75 to around 5000 kVa.

In many cases, the transformer package includes safety switches and built-in fuses.

Furthermore, like many distribution transformer types, this type can also cater to numerous service lines or households.

A typical pad-mounted transformer set comprises the core/coil assembly (including the transformer) immersed in oil or the like.

Additionally, a wiring cabinet with high and low-voltage wiring compartments encloses high and low-voltage bushings, respectively.

It is also typical to weld the cover to prevent unauthorized access to the enclosure.

Single Phase and Three Phase Padmounted Transformer From Daelim
Single Phase and Three Phase Padmounted Transformer From Daelim

Pole-Mounted Transformers

Another medium-voltage transformer type is the pole-mounted transformer.

This type might be the most publicly familiar as it is the cylindrical component mounted on a power pole.

You can also say that pole-mounted transformers are the overhead counterpart of pad-mounted transformers but are more common in remote areas.

Pole-mounted transformer rating can range from 16 kVA to 100kVA. Like all transformer types, it can either be a single or three-phase design.

Although most pole-mounted transformers are single-phase, three-phase designs can have significant advantages.

Among these advantages, the most notable is that three-phase types can be cleanly installed and more efficient.

Furthermore, manufacturers design these transformer’s cases to reduce the accumulation of water and corrosive materials, ideal for harsh environments.

They are also better at handling high voltages than standard transformers.

Pole-Mounted Transformers
Pole-Mounted Transformers

Substation Transformers

This transformer is the substation’s core and regulates the voltage coming out of the power generation.

Typically, you can rate these transformers through their input and output voltage relationships.

A typical rating includes 15 kV, 25 kV, or 35 kV on the primary at a power rating of about 5-20 MVA.

In addition, its secondary voltage can come around 15 kV or even less than 600 V.

As typical for higher ratings, substation transformers are usually oil-submerged.

This oil content serves as a temperature regulator that keeps the device working even at extremely high loads.

Other common features among distribution transformers are fins for oil circulation and heat dissipation.

Other models have fans or pumps to circulate oil forcibly.

What Are The Medium Voltage Transformer Clearances?

Medium-voltage transformer clearances can vary per type.

The local building department establishes transformer spacing guidelines for a transformer located near a building or structure.

For pad-mounted transformers, the typical clearance requires up to 4ft minimum vertical clearance assuming no windows are within the vicinity.

Furthermore, the sides of the unit must be clear for a minimum of 3ft.

Also, the transformer needs to be 10ft horizontally far from building fenestrations and fire hydrants.

Meanwhile, pole-mounted transformers should be 5 meters high from the ground level and mounted on designated locations.

Lastly, for substation transformers, it is the local energy regulating bodies that assign the clearances.

However, the common standard is for it to be enclosed in a fenced and secured compound.

It also requires the necessary provision for safety controls and checks.

What Are The Standard Sizes Of Transformers?

Transformer manufacturers can designate different transformer sizes, both for convenience and asset standards.

However, in terms of common market options, here are the corresponding standard sizes:

  • 3 kVA
  • 6 kVA
  • 9 kVA
  • 15 kVA
  • 30 kVA
  • 37.5 kVA
  • 45 kVA
  • 75 kVA
  • 112.5 kVA
  • 150 kVA
  • 225 kVA
  • 300 kVA
  • 500 kVA
  • 750 kVA
  • 1,000 kVA

To get the specific ratings that you need, do consult with your manufacturer. A set of specifications is a standard for full product information.

How Many Volts Are Considered High Voltage?

A system or line should be within the 35 kV to 245 kV range to be considered as high-voltage.

What Is Standard Voltage?

The population uses mains electricity to power machines and appliances in homes and businesses in many parts of the world.

It is delivered by AC power lines, which run through buildings or run underground.

Voltage and frequency are different in every region. In the United States, a voltage of 120 V and a frequency of 60 Hz is used.

In other parts of the world, they use a voltage of 230 V and a frequency of 50 Hz.

Also, note that a different combination can exist, like 230 V at 60 Hz.

Medium voltage transformers are probably the most widespread range type of transformers.

After all, these transformers are responsible mostly for power distribution and are directly proportional to the population density.

Aside from being widely distributed, it is also a device that requires high-need for efficiency and reliability.

Thus, it is imperative to find a trusted name in selecting medium voltage transformers.

In this regard, DAELIM is among the top transformer manufacturers.

After building a reputation in the Chinese market, DAELIM continues to establish itself as among the resounding names in the electric market globally.

With its high regard for quality, Daelim developed Daelim Belefic, a transformer brand that is both competent and cost-efficient.

Daelim Belefic is your partner for electrical solutions and products. For inquiries, contact DAELIM today.

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 Medium Voltage 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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