T&D World Magazine

Three Winding Temperatures Added to the Transformer Advantage Line

Weschler's line of transformer and LTC temperature monitors has been further enhanced with the introduction of a new three-winding capability. With this option, users can display current and temperature for up to three windings on a substation transformer.

Many transformers can be adequately monitored from a single winding. However, with higher transformer loads, some utilities may prefer to monitor multiple windings. In the Weschler units, winding temperature is calculated using a sophisticated algorithm based on IEEE Std C57.91-1995. The Transformer Advantage analyzes transformer parameters to determine thermal time constants for the oil and each winding. These time constants are changed dynamically based on load and cooling conditions. Rate of change information is also used to further improve the reading accuracy.

Feedback from up to five cooling stages can be monitored to determine the actual condition of each stage and its contribution to the overall heat removal in the transformer. Most temperature monitors are open loop; they assume each stage is operating properly. A few more sophisticated temperature monitors use a voltage measurement to detect cooling stage operation. This method cannot determine the condition of a fan or pump. The Transformer Advantage measures the actual current draw in a motor or flow rate in a pump to assess the condition of that stage. In addition to more accurate temperature readings, this method will provide warning of reduced transformer capacity due to a partial cooling failure.

These new features are available on all Weschler Advantage models using the calculated winding temperature method. The Advantage CT/LTC offers both transformer and LTC temperature monitoring in one unit. Analog, digital and DNP3.0 outputs facilitate remote monitoring or connection to a substation network.

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