Low voltage short circuit impedance measurement

Low voltage short-circuit impedance measurement
The low voltage short -circuit impedance measurement by means of a low voltage three phase power source can be performed because the impedance valuedoes not depend on the applied voltage.The low voltage short-circuit impedance measurement requires utilization of highly accurate instrumentation on the one side, and elimination of the errors caused by the fluctuations of low voltage power networks due to welding equipment, etc., on the other.In order to carry out these measurements a diagram developed. The diagram uses data acquisition and processing system (DAQ) that enables evaluation of the measured data, the short-circuitimpedance variation curve plotting on the spot, as well as the subsequent processing obtained data. The processing system also corrects the data with the supplyvoltage frequency variation.

Furthermore:
The short-circuit impedance measurement between allthe winding pairs and by each position of the on-load tapchanger is imperiously necessary for:
- verifying the observance of the technical conditions,the designed ones included;
- verifying the possible nonconformities in thewinding manufacturing;
- verifying the behavior of the winding operation onsite (the measurement is performed in agreement with thenorms in force);
- carrying out the system calculations and the short circuitones (including the correct protection regulation);
- verifying the loading of the same type, as well as a of different type transformer units.
The short-circuit impedance measurement can beperformed by connecting the measurement installation to a low voltage (380/220V) source provided that highly accurate instrumentation enabling the automatic data processing is used.

Taken from a paper:
Power Transformer Units Condition Assessment Using VirtualInstrumentation
Discussion welcomed.