HV testing of power transformers
Location: South Australia
Electrical testing of new power transformers is a critical task that is undertaken to identify any abnormalities with the transformer prior to energisation. The results obtained are compared to the factory test results and can be used as a baseline for all future testing.
STE were engaged by a customer to perform the site acceptance tests on four new power transformers prior to energisation in regional South Australia. The location was 390 km from head office, and the testing team drove to site taking all of the required testing equipment with them.
Our HV testing technicians conducted a full range of acceptance tests on the four power transformers – two 275kV and two15kV.
The tests conducted were inclusive of the following:
- Dissipation/power factor measurements, to ascertain the insulation condition in the bushings and between the windings
- Sweep frequency response analysis, to evaluate the mechanical integrity of core, windings and clamping structures within the transformer
- Leakage reactance, to confirm the integrity of the windings, including displacement and/or distortion
- Insulation (megger), to confirm the condition of the internal insulation
- Excitation, to detect poor electrical connections
- DC winding resistance, to confirm the continuity of the windings
- Power transformer turns ratio test, an AC low voltage test which determines the ratio of the high voltage winding to all other windings at no-load; and
- Dirana tests, to determine the water content and oil conductivity of the insulation mediums.
Close interaction with the client throughout the testing procedures ensured that the project’s main objectives were achieved. The results obtained from the suite of tests conducted were all within the industry’s standards, and the transformers were energised without incident.