DC Tests for Stator and Rotor Windings Index

DC Tests for Stator and Rotor Windings Index

These tests are sensitive indicators to the presence of dirt, moisture, and cracks. They must be performed off-line with the winding isolated from ground, as shown in Fig. 16.1. Suitable safety precautions should be taken in performing all high-potential tests. When high-voltage dc tests are performed on water-cooled windings, the tubes or manifolds should be dried thoroughly, to remove current leakage paths to ground and to avoid the pos- sibility of damage by arcing between moist patches inside the insulating water tubes. For greater sensitivity, these tests can be performed on parts of the windings (phases) isolated from one another.

The charge will be retained in the insulation system for up to several hours after the application of high dc voltages. Hence, the windings should be kept grounded for several hours after a high-voltage dc test to protect personnel from a shock.

Tests using dc voltages have been preferred over the ones using ac voltages for routine evaluation of large machines for these reasons:

1. The high dc voltage applied to the insulation during a test is far less damaging than high ac voltages due to the absence of partial discharges.

2. The size and weight of the dc test equipment are far less than those of the ac test equip- ment needed to supply the reactive power of a large winding.


Ahmed Farahat is EECS engineer With 18 years of experience in the field he worked on different technological discipline and and had honored Post Graduate Diploma In Computer Science And Engineering

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