High-Efficiency Distribution Transformers

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In electrical power systems, a distribution transformer is one of the key components of the grid. It is employed for reducing the voltage levels to a suitable value for utilization in residential, commercial, and industrial applications.

A distribution transformer is basically a link between a high-voltage transmission line and a low-voltage distribution line.

In smart grid distribution systems, a specially designed distribution transformer is used which is called High-Efficiency Distribution Transformer (HEDT). This transformer is so designed that it has minimum energy losses and higher efficiency than an ordinary distribution transformer. The use of HEDT in a smart distribution grid results in energy saving as well as reduced operational costs.

Read this chapter to learn about high-efficiency distribution transformer, its construction, properties, and advantages.

Introduction to High-Efficiency Distribution Transformer

A High-Efficiency Distribution Transformer (HEDT) is a special type of distribution transformer which is designed to have reduced energy losses and higher operational efficiency. Similar to any other type of distribution transformer a high-efficiency distribution transformer also changes the high voltage levels of transmission lines to a lower voltage level suitable for utilization in residential, commercial, or industrial applications.

Generally, the energy efficiency of a high-efficiency distribution transformer is very high, typically ranging between 96% to 99%. The main objective behind using high-efficiency distribution transformers in smart grids is to

• Reduce the energy losses
• Save energy
• Reduce operational costs
• Reduce impact on environment, etc.

Therefore, a high-efficiency distribution transformer addresses issues related to both economic and ecological points of view.

Properties of High-Efficiency Distribution Transformer

A typical high-efficiency distribution transformer has the following main properties −

Minimum Energy Losses

A high-efficiency distribution transformer is designed in such a way that it has minimum core and copper losses. This is achieved through better design and assembly processes, increasing cross-section area of windings, and using core material of better magnetic properties.

Reduced Cooling Losses

A high-efficiency distribution transformer is equipped with an efficient cooling technology. Cooling losses can also be reduced by reducing the other energy losses like core and copper losses.

Good Core Material

In a high-efficiency distribution transformer, the core is constructed from amorphous material which has less hysteresis and eddy current losses. This further improves the efficiency of the transformer.

What is Amorphous Material?

Amorphous materials are non-crystalline materials that have a random atomic structure. In an amorphous material, there are no axes of symmetry and its constituent atoms are distributed randomly within the bulk of the material.

Amorphous materials are produced by rapid solidification of a liquid alloy. This process develops specific magnetic properties and very low energy loss properties.

The non-crystalline structure of the amorphous material results in the following technical advantages when used in a transformer −

• Reduced core losses i.e., hysteresis and eddy current losses
• Enhanced magnetic properties like high permeability
• High temperature withstand capability, etc.

Construction of High-Efficiency Distribution Transformer

A typical high-efficiency distribution transformer (also referred to as amorphous distribution transformer) is shown in the following figure.

The main components of the high-efficiency distribution transformer are explained here −

• Magnetic Core − The core is the main component of a transformer that provides a closed path for magnetic flux to flow. In a high-efficiency distribution transformer, the magnetic core is made up of thin ribbons of amorphous metal.
• High Voltage Winding − The high voltage winding of the amorphous distribution transformer is made up of copper conductors of round shape. It has a rectangular shape and single-coil construction.
• Low Voltage Winding − The LV winding is also made up of copper conductors but of rectangular shape. Its construction can be helical, spiral, or foil type.
• Insulation Material − In high-efficiency distribution transformers, a high-grade insulation material is used to provide insulation between core and coils and to prevent short-circuits.
• Cooling System − The cooling system of high-efficiency distribution transformers is designed to dissipate heat at a faster rate to provide better cooling. It can be either air cooling or oil cooling.

The high-efficiency distribution transformers are produced as 1-phase or 3-phase units with 3-limbs or 5-limbs core construction. These transformers are generally designed for volt-ampere rating of up to 10 MVA.

It is also important to note about high-efficiency distribution transformers is that they have large cross-section area of core as compared to core made up of silicon steel. This is because of low saturation index of the amorphous ribbons. Due to this, a high-efficiency distribution transformer has larger physical dimensions.

Energy Savings and Economic Profiles of Amorphous Transformers

An amorphous transformer results in the following important energy saving and economic profiles −

• In an amorphous transformer, the no-load losses are very low as compared to a conventional distribution transformer with silicon steel core. This results in reduced energy losses within the transformer and improved energy saving.
• Amorphous distribution transformers have lower operating costs due to reduced energy losses. This benefit makes these transformers economical in long run.
• Amorphous distribution transformers perform better in over excitation stage.
• Due to energy saving and reduced operational cost, the amorphous distribution transformers give better return on investment.
• The reduced energy consumption in amorphous transformers helps in minimization of emission of CO2, SO2, and other greenhouse gases.

Advantages of High-Efficiency Distribution Transformers

A high-efficiency distribution transformer offers several benefits over a conventional distribution transformer. Some of the key advantages of high efficiency distribution transformers are listed below −

• As the name implies, these transformers have high overall efficiency that results in improved energy saving.
• Due to use of high-quality material and advanced design and manufacturing technologies, high-efficiency distribution transformers have longer lifespan.
• High-efficiency distribution transformers have a robust construction and hence they require less maintenance.
• These transformers improve the overall efficiency of the distribution system. This gives several environmental benefits like sustainable energy system, reduced carbon footprint and greenhouse emissions.

Conclusion

A high-efficiency distribution transformer is a specially designed transformer which consists of a magnetic core made up of amorphous metal and produce lower energy losses. These transformers are used in smart grid distribution systems to minimize the energy losses, improve the system efficiency, and maximize the energy savings.