Yokogawa’s measurement accuracy leads to major cost savings for transformer industry

One of the world's leading suppliers of test facilities for the manufacturers of power turbines and transformers is using digital power analysers from Yokogawa because their accuracy offers major potential cost savings for end-users.

Claes Hugoson, CEO of Elektrisk Drivteknik AB, based in Kungalv, Sweden, travels around the world to build test rooms to measure and verify the performance of the transformers used with power turbine generators. "The accuracy of these measurements is currently one of the most important factors in minimising the no-load losses in these transformers", he comments: "The manufacturers of power turbines frequently have a penalty clause in their contracts regarding the level of these losses, and they risk paying heavy fines if the no-load losses are too high." The level of these fines can be judged by the fact that it can cost 100,000 Swedish Krona (about 11,500 euros) per kilowatt lost, making it vital to be able to measure the losses with great precision."  

There are always no-load losses in a transformer, whether or not power is being drawn from it. Some of these losses are used in the magnetisation of the transformer, while others are caused by the actual iron core, depending on the input voltage. Resistive Joule heating losses in the primary windings, as well as the reactive leakage flux, also contribute to the no-load losses.

"The active no-load losses are roughly one per cent of the reactive losses, so measuring correctly with high precision and high repetitive accuracy is of the utmost importance. The instrument must be totally reliable, since even a small error in the measurement could have enormously expensive consequences", Claes Hugoson points out.

"There are currently three manufacturers globally for this type of power-measuring instrument", says Claes Hugoson, "but when I started my own company I noticed the Yokogawa WT3000T digital power analyser was very popular with the manufacturers of power transformers."

The Yokogawa WT3000T is a precision power analyser specifically targeted at the needs of the power transformer industry. Based on the company's highly successful WT3000 instrument, it combines exceptional accuracy and long-term stability with the ability to carry out measurements at low power factors, which normally have a dramatic effect on accuracy. For commercial frequencies from 45 to 66 Hz and even at a power factor as low as 0.01, the WT3000T offers an accuracy of better than 0.6% of reading at 100 V and 1 A.

Claes Hugoson had a bit of luck when he started his own company by being given a couple of projects from the transformer industry. Today, his clients include the biggest players in this market, and his work now involves travelling around the world setting up test rooms for measurements on new power transformers. "For each client, I make sure a test room is erected where we can test the transformer before it is installed with the customer. I also help to tune all the equipment and to train the personnel in measurement techniques." To help him, he also has a consultant who looks after the transient voltage and partial discharge measurements."

In some cases, it is necessary to add a measurement transformer between the measurement instrument and the actual transformer, depending on how high the voltage is. The measurement transformer transforms the voltage or the current to a level that can be handled by the measurement equipment. Claes Hugoson also takes responsibility for this part of the measurement system. "It is important that the measurement system is considered as a whole, including the power analyser, transducers for current and voltage, and additional components such as measurement transformers."

Finally, Claes Hugoson emphasises that the equipment he supplies to clients is based on his own considerable experience in this sector: "It is a question of trust when I negotiate with my customers that I have the same instrument in my own instrument cabinet as they have in their plant."

"My experience in this sector reinforces my belief that it is important to maintain power measurement accuracy thorough the transformer life cycle from R&D, though production and installation, to service and maintenance", he adds, "and the Yokogawa WT3000T has certainly enabled us to rise to this challenge."

Yokogawa is the world's largest manufacturer of power meters and analysers. The WT3000T digital power meter is part of a wide range of products that deliver guaranteed power accuracy for applications from production line testing to the highest precision laboratory measurements in research and development.