25MVA Transformer Explained

MVA transformers are distributed power transformers created to supply large industrial companies such as factories and power plants. There are several MVA transformers available to suit your electrical power needs. Today, we will talk about the 25 MVA transformer, its features, specifications, and types. 

When supplying electrical power in large establishments, you need a sustainable high-power transformer you can rely on for its maximum function. Thanks to transformers, you are able to use the appliances, machines, and equipment you need for your everyday life. 

25MVA Transformers

Being in the transformer industry for more than 15 years, DAELIM strives to remain on top with its top-notch electrical equipment products and services. Clients trust this company because of its reliability, as they strictly follow international standards, such as ANSI, IEEE, IEC, CSA, AS/NZ, and the like. 

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

Table of Contents

What Is a 25MVA Transformer?

25MVA Transformers1

25 MVA transformers are suitable for distributing electrical power in larger diverse areas. They allow convenient electrical energy conversions between primary distribution circuits and generators.

Generally, similar to 1MVA and 10MVA transformers, they are the transformers of choice for supplying larger and higher electrical power frequencies and intensities in company establishments and tall buildings. The main benefits of these power transformers are the capacity to power appliances in high-use rooms, such as the kitchen area and the laundry room. 

These transformers have undergone standard testing procedures, ensuring that their quality is top-notch and reliable. 

The following are the tests done:

  • Insulation resistance
  • Withstand voltage testing
  • Amount of windings resistance
  • Inspection of vector group and voltage ratio
  • Impedance test
  • No-load test with a rated voltage and frequency
  • Oil leakage test
  • Withstand testing with induced over-voltage
  • Partial discharge measurement

25 MVA Transformer Specification

40 MVA Oil Immersed transformer

Since these are power transformers, they are mainly responsible for generating and distributing electrical power while simultaneously reducing power loss risk during its electrical power transmission. 

Additionally, 25 MVA transformers can function efficiently and effectively when turned on at full capacity 24/7. 

The following are the main specifications of these distribution power transformers:

  • Usage: For power distribution
  • Number of coils: two windings
  • Transformer Type: Oil-immersed
  • Frequency: 50 Hertz
  • Cooling Method: ONAN
  • Efficiency: Level II and III, 3 to 5 Star

Aside from the main specifications, these transformers also have the following features:

Read on:2022 Ultimate Oil Immersed Transformer Guide

Dielectric Strength

These transformers’ heavy-duty design and construction contributed to their dielectric strength and withstanding impulse voltage. This ensures a low capacitance between the ground and the winding, preventing creepage problems because of proper insulating material coordination. 

Thermal Capability

The heat from the coils inside the transformer and the iron cores creates the magnetic circuit to allow its transmission to the insulating oil. From the insulating oil, it will radiate through the cooler to the air. Maintaining a transformer’s cooling effect is important because it affects its capacity and insulation life. 

Mechanical Strength

Additionally, these transformers’ mechanical strength is also top-quality because of their tank design and winding, allowing even mechanical force distribution to effectively support short-circuit strength. 

Types of 25 MVA Transformer

25MVA transformers have several categories, classifications, and styles. However, they can be divided into two main types: Step-down substation MVA transformers and dry-type ones. 

Step-Down Substation

Types of 25 MVA Transformer1

A step-down substation transformer is mainly placed in distribution substations and is responsible for reducing the voltage to a level suitable for smaller distribution lines and cables. Homeowners normally require these transformers because they only need a small amount of voltage to power up their residences’ appliances, lights, and other machines. 

Additionally, step-down substation MVA transformers can also be located at the switching points of electrical grids. When placed near the grids, they allow proper connection of the grid’s different parts and are the main source of electrical power for transmission lines. Generally, a step-down substation transformer can convert a transmission voltage into a subtransmission voltage at 69 kV. 

The power converted in sub-transmission voltage lines becomes the electrical source of distribution substations. 

Learn more  about Transformer Step Down , Everything You Need To Know



Dry-type MVA transformers do not need liquid incorporation to dissipate heat within the equipment and maintain the required temperature for its maximum efficient function. Instead of liquid, the coils are constructed within a gaseous medium or dry insulation. 

Generally, dry-type transformers can survive extreme environmental conditions because air is created by impregnating vacuum pressure in polyester, VPI epoxy, silicone varnish, or cast resin. However, you need to remember that these transformer types require regular maintenance and inspection to ensure that they are clean with no blockages, preventing overheating.

The best advantage of dry-type transformers is not having to perform oil analysis. They are preferred to be placed in indoor areas with a higher risk to fire exposure. Generally, there are three types of dry-type transformers:

Try for free Dry-type Distribution Transformers Solution for Public Building


Ventilated dry-type transformers use fan-assisted or natural circulation through several ventilation openings to maintain a transformer’s ideal temperature for proper function. 


Encapsulated transformers, also known as potted or compound-filled, have enclosed windings within a matrix of solid-insulating materials, including gravel, resin, sand, or epoxy, for proper heat dissipation. 


Non-ventilated dry-type transformers are preferred when the atmosphere is at risk for corrosive, conductive, and combustible materials that can potentially harm the transformer. These dry-type ones allow heat dissipation through the enclosure’s surface area.

25 MVA Transformer Power for Mining

Bitcoin mining power systems mainly use MVA transformers to allow efficient generation of power for mining. These transformers can convert medium voltage from one substation, supplying the ideal mining power supply. Crypto power is commonly at 1000 kVA to 5,000 kVA increments. 

The main purpose of bitcoin mining is to generate a network for transaction confirmations essential in maintaining and developing blockchain ledgers. 

Keep reading:The Best Crypto Mining Farm Guide – Bitcoin Mining Power Supply

What do you mean by a transformer's polarity?

A transformer’s polarity pertains to the induced voltage’s relative direction from low to high voltage terminals. In simpler words, polarity refers to how a transformer releases and brings out the leads. 

For instance, during an AC half-cycle, when the applied current is traveling from H1 to H2, the direction of the secondary induced voltage will be from Y1 to Y2. 

What if the transformer isn't grounded?

Generally, transformers do not need to be grounded because grounding is mainly done to increase safety and security when using appliances that use the electrical power from the main supply. However, grounding transformers and connecting them to neutral power systems makes it safer for you and your personnel. 

The main purpose of neutral transformer grounding is to maintain a continuous and permanent conductive path to the Earth’s magnetic field. This is assuming that the transformer has enough levels of the following:

  • Ampacity to carry faulty currents
  • Low impedance, limiting the rise of voltage above the ground
  • Protection to allow the operation of the devices connected to the circuit

When a transformer is properly grounded, it reduces shock hazards to your personnel and limits potential damage to your equipment. On the other hand, failing to connect it to a neutral wiring system for grounding can lead to life-threatening situations, leading to injury and even death. 

Is it possible to use single-phase transformers on a three-phase source?

Yes, single-phase transformers can be used on three-phase transformer sources. You need to connect the primary leads to the random two wires of the three-phase source. After the connection, the transformer functions as a single-phase. 

Read on: Single Phase Transformer VS Three Phase Distribution Transformer

The Future of 25MVA Transformers 

25 MVA transformers are useful in industrial establishments, generating electrical power and converting it to a voltage level you need. They range in various models and types, and proper handling and maintenance are the secrets to their longevity and maximum function for your business’s efficiency. 
At DAELIM, we value our clients and want them to experience the best possible transformer they need. With our premium-quality transformers and services, we can guarantee that we offer our products at the most affordable price, staying on top of our competitors. 

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