Power transformers are at the heart of electrical transmission and distribution systems, and as competition increases within the energy sector, so does the pressure on transformer manufacturing industry to improve reliability and reduce costs of transformers.

The power transformer concept was conceived and developed in the late 1800’s and since then, the basic concept of transformer has remained the same. However, design and construction techniques have improved to increase both - the overall efficiency and cost effectiveness of manufactured units.

Why Modern Transformer Design

With superior expertise in designing coupled with extensive R&D efforts, modern transformers are much smaller in size, lower in cost, and are able to promise a remarkable increase in efficiency and reduce lost energy.

Especially for countries like the US, modern transformer design can play a significant role in reduction of energy loss. The U.S. has only 4% of the world’s population but produces 25% of its greenhouse gases. The country has over 9,200 electricity generating units much of them old, needing replacement and thus largely inefficient. Since 1982, growth in peak demand for electricity in the U.S. has exceeded transmission growth by almost 25% each year, even while a majority of the energy transformers in the country continue to waste away large amounts of energy.

Better transformer design and the use of superior grade electrical steel can drastically reduce no-load loss, one of the prime components of loss in an energy transformer. No-load loss can be further reduced in some cases if conventional electrical steel can be replaced with amorphous metal.

Types of Transformer Designs

Transformer life expectancy is based on a number of factors, the most important being the quality of its insulation system. Two things that damage transformer insulation are moisture and excessive heat. Addressing these two factors, modern transformer designs are developed to preserve overall insulation quality of the transformer. Some of these designs include open style, sealed tank, conservator style, and automatic gas pressure.

Open Style Design - is a tank design that has an air or gas space in the main tank above the oil level. The benefit of open style design transformer is in its lower initial cost; however, this is the least effective method of protecting a transformer’s insulating system.

Sealed Tank Design - In the sealed tank design, the core/coils and oil are completely enclosed in the main tank with no ventilation to the atmosphere. This offers better protection against the ingression of moisture and contaminants into the insulation of the transformer. One drawback of this style of transformers, however, is that if a weld, flange or gasket develops a leak in the gas head space above the oil, there will be a direct exchange of the oil with the outside atmosphere.

Conservator Type Design - The conservator design has the main tank completely filled with oil and a smaller expansion tank positioned above the main tank, with about 5 to 10 per cent the volume of the main. This design is good to protect transformer insulation.

Automatic Gas Pressure Design - The gas regulation design is very similar to the sealed tank design with the exception that the air space above the oil is kept at a positive pressure at all times by a gas regulation system. With this style, as long as the gas bottle and regulation system are intact, a positive pressure is automatically maintained on the tank, allowing no atmosphere-to-oil contact. This system is fairly reliable; however, it does come with a higher initial price tag and maintenance cost.

Trends in Modern Transformer Design

With the cost of energy increasing and pressure mounting to reduce transformer losses, attention is on modern transformer design that incorporates technology to lower energy losses in transformers. Most transformers are inherently efficient when they function at 100% load. However, 100% load is an ideal situation, and many transformers need to function at far lower loading. As transformer loading changes so does its efficiency. Low loss transformers with modern designs are said to be 30-50% more energy efficient and their losses are designed to be 30% less at 35% loading.

Modern transformer design is governed by industry trends that make these transformers stand out for their numerous energy and cost saving advantages.

Incorporating air bag in expansion tank

Newer transformer designs with conservator tanks incorporate an air bag in the expansion tank, which virtually eliminates moisture egress from oil contact with the outside atmosphere.

Artificial Intelligence techniques in transformer design

Numerous transformer design tools have been developed also such as artificial intelligence (AI) techniques in combination with finite element method (FEM). Today, AI is widely used for modeling nonlinear and large-scale systems, especially when explicit mathematical models are difficult to obtain or completely lacking. Moreover, AI is computationally efficient in solving hard optimization problems. On the other hand, FEM is particularly capable of dealing with complex geometries, and also yields stable and accurate solutions.

Innovative insulation material

Thermal deterioration of transformer insulation material reduces dielectric strength and reduces its ability to withstand short-circuit events. Innovative hybrid high-temperature insulation however can improve insulation temperature tolerance, improve winding mechanical strength, and reduce costs of maintaining and replacing transformers. Hybrid insulation consists of using layers of aramid papers and cellulose papers. Additional global design modifications include reducing the number of cooling ducts between layers and reinforcing the frame of the transformer to improve short-circuit withstand strength. Higher reliability and longer life anticipated by hybrid-insulation manufactured transformers results in cost savings to the utility.

Benefits of Modern Transformer Design

There is a gradual and increasing preference towards modern transformer design not just due to legal requirement but simply because these transformers have a higher energy efficiency and soon pay for themselves. Benefits of modern transformer design include,

• Longer transformer life
• Reduced cost of energy due to reduced wastage
• Reduced Greenhouse Gas emissions
• More efficient use of energy; higher production with lower energy use