Tap Changer & Winding Analyzers

The Tap Changer & Winding Analyzer TWA40D is designed for a simultaneous three-phase tap changer analysis and six-winding resistance measurement of both the primary and the secondary transformer windings. This is performed with only one single-step cable setup, with test currents of up to 40 A. Once all 6-8 bushings are connected and the transformer configuration selected, the instrument adjusts the test procedure automatically.

Dynamic resistance graphs are recorded for all three phases simultaneously, so the synchronization is verified using the cursors provided in the DV-Win software. All three phase traces are plotted on the same graph. This unique feature enables checking the on-load tap changer phase synchronization. In addition, the tap changer motor current is recorded, and displayed on the same graph. These advanced tap changer analysis features enable detecting problems with contacts, diverter switch, transition resistors, motor and mechanism, etc. The built-in tap changer control unit enables remote control of the tap changer operation from the instrument’s keyboard.

The TWA40D enables performing both single-phase and three-phase demagnetization. Demagnetizing the magnetic core of a transformer requires alternating current applied with decreasing magnitude down to zero. The TWA40D provides this alternating current by internally changing the polarity of a controlled DC current. During the demagnetization process the TWA40D supplies current at decreasing magnitude for each step, following the proprietary developed program.

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