Precision power analyser for transformer testing

The new 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, the new instrument combines exceptional accuracy and long-term stability with the ability to carry out measurements at low power factors: a challenging area for transformer manufacturers.

In developing the new WT3000T, Yokogawa has worked closely with transformer manufacturers, who require an accurate instrument to provide direct readout of key parameters along with clear overload and safety indication.

Of particular concern to transformer manufacturers is the economic impact of transformer losses in the power generation and distribution sector. If a transformer exceeds its specified loss under no-load conditions, the cost penalty for the manufacturer can be as high as €8000 per kilowatt. Hence the accuracy of the measurement system becomes critical: the more precise the measurement, the less likelihood there will be of penalty charges.

Not only does the WT3000T offer excellent accuracy at the low power factors that often compromise the integrity of transformer measurements: it also has accredited calibration via VSL (the National Metrology Institute of the Netherlands), which guarantees that the integrated transformer measurement system meets the requirements of the IEC60076-8 standard covering power transformer applications.

At the standard commercial AC frequencies in the range 45-66 Hz, the WT3000T offers an accuracy of better than 0.6% at a power factor of only 0.01 (at 100 V and 1 A). It also provides 6-digit resolution through the use of 32-bit RISC processing and high-quality 16-bit analogue/digital convertors. The instrument’s accuracy is also indispensable for additional measurements on capacitors, line filter coils or other power-factor correction circuitry used in the power grid.

The instrument’s accredited calibration certificate, provided at delivery by VSL, is based on tests performed at a frequency of 53 Hz and at power factors of 1, 0.5, 0.05, 0.01 and 0.001. Because of its high stability and precision, the WT3000T can itself be used as a calibration standard. The long-term stability of the WT3000T means that its recommended calibration interval is two years, offering additional benefits in terms of minimising downtime and saving money.

The WT3000T provides direct readout of corrected power under small load conditions according to the formulas in the IEC and ANSI/IEEE standards. The large (8.4-inch) colour LCD screen makes measurements easy to read.

Clear on-screen indicators alert the operator when the voltage and/or current inputs of the power meter are overloaded, allowing the power to the device to be disconnected to prevent potential costly damage.

Yokogawa in power measurement

Since its origins in 1915 as a meter research institute, Yokogawa has been a major force in power measurement, and is now the largest power meter manufacturer in the world. In 1950, Yokogawa introduced the thermodynamic power meter, and then achieved worldwide recognition with the patented 2885 standard watt convertor. This was used by many laboratories and organisations as a primary standard, and was followed by further innovative power meters such as the 2531, 2533, PZ4000 and WT3000.