As fuel costs rise and power outages become more frequent across the country, the US power generation and distribution system has become a focus of attention. So has the need to conserve energy and the need to invest in energy efficient products of all kinds. Of particular interest are products such as power transformers that remain energized and consume power 24 hours a day.
The transformer is a critical component of the power network. If even a single unit is turned off for a short period of time, a large number of homes and commercial establishments are plunged into darkness, resulting in substantial economic loss.
Unfortunately, a significant amount of equipment in the utility network is over 40 years old and needs to be replaced in the near future. According to the Department of Energy (DOE), distribution transformers that are 30 years old or older can waste between 60 and 80 billion kWh per year. A better designed transformer could generate annual energy savings of up to $1 billion. Therefore, maintenance, upgrading and the purchase of new transformers are quickly becoming imperative.
The importance of transformers
The distribution transformer is the single most important piece of electrical equipment installed in an electrical distribution network. It also has a huge impact on the overall cost, efficiency, and reliability of a network. Select and purchase energy efficient distribution transformers that are optimized for:
* A particular distribution network
* The utility’s investment strategy
* Network maintenance policies
* Local service and charging conditions
– will provide definite benefits (better financial and technical performance) for both utility companies and their customers.
As climate change looms on the horizon, there is also increasing interest in protecting the environment from greenhouse gas emissions. The regulatory requirement now is to install high-efficiency distribution transformers that have fewer energy losses, ultimately resulting in fewer pollutants being released into the environment.
transmission losses
Transformers are not perfect devices; they do not convert 100% of the power input into usable power output. The difference between the energy input and that available at its output is quantified as energy loss. There are two types of transformer losses: no-load losses and on-load losses.
* No-load losses
No-load losses are also known as core losses. This loss is calculated based on the amount of power required to magnetize the transformer core. Since most distribution transformers are energized 24/7, no-load losses are present at all times, whether a load is connected to the transformer or not. When the load is light, the no-load losses account for most of the total losses.
*Loss of charge
Load losses, on the other hand, are those losses incidental to the transportation of a load. These include losses in the windings, eddy losses due to parasitic flux in the windings and core clamps, and circulating currents in the parallel windings. Because the load losses are a function of the square of the load current, they increase rapidly as the transformer is loaded. Load losses account for most of the total losses when a transformer is heavily loaded.
Decide which transformer to buy
Many electrical distribution companies claim that they purchase distribution transformers using some type of loss assessment procedure. However, the cost of the transformer is still an important factor in determining which transformer to buy. The components of a transformer, design, construction and installation affect its cost. For example, amorphous metal core transformers have 75% less no-load loss than a silicon steel core transformer, but cost 25% more than a silicon steel transformer.
Transformer losses affect the cost of design, construction, and installation. The transformer manufacturer typically incorporates the cost of losses into the transformer cost to optimize the transformer design.
Most companies that buy transformers look at the quote rather than the total cost of ownership (TCO). TCO over the life of the transformer tends to be high for less energy efficient transformers, while initial cost is higher and TCO is low for energy efficient transformers.
However, the payback period for high-efficiency transformers is relatively short, often less than 2 years. The Internal Rate of Return in energy efficient transformers is constantly above 10% and sometimes up to 70%.
Making purchasing decisions for a great power transformer is more complex than simply comparing manufacturers’ prices. It requires a company to know its requirements and compare not only the cost of transformers but also the TCO over a period of two to three decades. If this is done accurately, the cost effective solution invariably turns out to be the energy efficient transformer, even if it has a slightly higher initial cost.
When buying transformers, it’s not ‘short run’; these infrastructure investments are typically made with 30 to 50 years of service in mind. Energy efficient transformers are definitely the only way to go, given the strong economic case they make in the long run.