The worldwide market for large (high-end) transformers is significant with sales in excess of US$2 billion. In the United States, total sales of power transformers reached nearly US$11 million in 1996. However, the market for transmission and larger distribution substation transformers has been flat at best and declining slightly at worst in the mature electrical markets of North America and Western Europe.

In fact, most transformer manufactures will state that if it wasn't for exports sales, the North American plants would be suffering. Currently, only about 20% of the world demand for large power transformers comes from the United States and Canada. In the 1970s and earlier, North America represented about 40% of world demand.

The chart on this page illustrates demand among various world markets for large power transformers. Note the importance of the Asian Pacific market and the growing importance of South and Central America. In terms of units, more than 8000 transformers of at least 2 MVA and up to more than 100 MVA were sold in 1996.

In the coming era of open access, more and more importance will be placed on the reliability of large power transformers because these units will be requited to carry higher loads more frequently under conditions of severe failure penalties.

In one recent Newton-Evan's survey, about 80% of the utility spokespersons interviewed indicated their belief that in this increasingly competitive climate, utilities would have to extend transformer life rather than simply replace current installations. More than half thought that the utilities would have to develop centralized monitoring of transformer operating characteristics.

While most utility operations officials say that power transformers should be monitored for temperature, pressure voltage, and a few other characteristics, many of the older, oil-filled transformers installed in transmission and distribution substations are now being monitored on-line for potentially dangerous dissolved gases. These monitoring devices provide an early warning system for potential catastrophic failures of critical transformers, and are now installed in about 8000 sites around the world.

Most utilities perform some type of chemical or dissolved gas analysis periodically on their important or "critical" transformers, perhaps as frequently as quarterly or at least annually, for about 60,000 of the more than 170,000 transformers installed in utility- and industrial-operated substations in North America.

As for the market for transformer monitoring systems that can monitor variables in addition to fault gases matures, there will be a new market segment emerging for total transformer monitoring units, and it is these units that will become key aspects of substation automation programs over the next few years.

The same study found that about half of utilities run their critical large power transformers above thermal limits, if only on certain occasions. About half believe that such practices are more likely in the future.

When all of this is viewed in light of the aging population of large power transformers in North America and Europe, more and more on-line monitoring devices will have to be installed as a prudent measure to minimize the likelihood of catastrophic failures in an open access environment.