Tan Delta Tests are carried out for Transformer Bushing and for the Transformer Winding. Transformer Bushing Tan Delta Test is similar to the CT Tan Delta Test and lnk to the Artivle on CT Tan Delta Test is :    .In this Article we are going to discuss in detail about Transformer Winding Tan Delta Test

Why is Capacitance and TanDelta Test carried out for Transformer Winding?

The Objective of this Test is to ascertain the general condition of the ground and inter-winding insulation of transformer

      What are the Precautions to be taken before carrying out the Test?

      1. The test set is a source of high voltage electrical energy and operator must use all practical safely precautions to prevent contact with energized parts of the test equipment and related circuits.
      2.  Never connect the test set to energized equipment.
      3. The ground cable must be connected first and removed last.
      4. The ground terminal of the input supply card (green lead) must be connected to the protective ground (earth) terminal of the line power source.
      5. Keep the high voltage plugs free from moisture, dust during installation and operation.
      6. Adequate clearance (Min 1 foot i.e. 30 cm) arc maintained between energized conductor and ground to prevent any arc over.
      7.  It should be ensured that test specimen is de-energized and grounded before making any further connection and no person may come in contact with HV output terminal or any materiel energized by the output.
      8. Porcelain of the bushings shall be clean and dry. Remove any dirt or oil with clean dry cloth.
      9. Test shall not be carried out when there is condensation on the porcelain. Preferably, tests shall not be carried out when the relative humidity is in excess of 75%

       

        Test Procedure:

        1. Isolate Transformer from High Voltage & Low voltage side with physical inspection of open condition of the concerned isolators/disconnector.
        2. Measure and record the ambient temperature and relative humidity for reference.
        3. Short the Terminals of the bushings of each winding together using bare braided copper jumper. These jumpers shall not be allowed to sag.
        4. Connect the ground terminal of the test set to a low impedance earth ground (to Earth mat of the substation).
        5. Connect the external interlock cable to the ‘Interlock terminal of the test set.
        6. Test kit HV Lead connected to Transformer Hv Winding & Test Kit LV Lead connected to Transformer LV Winding. Carry out the Test in UST, GST and GSTg mode.
        7. Test kit HV Lead connected to Transformer LV Winding & Test Kit LV Lead connected to Transformer HV Winding. Carry out the Test in GST and GSTg mode.

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