Automated Testing of Step-up Transformers in Solar and Wind Power Generation Systems

Transformers employed in wind and solar energy generating systems are exposed to harsh environment and operating conditions, and therefore, have high failure rates. However, condition monitoring relies on conventional off-line testing, which are difficult and costly to apply on-site due to the remote location of these systems. A new test concept for automated testing of step-up transformers using the utility-side inverter available in the system is proposed in this paper. The idea is to use the inverter to inject variable voltage and frequency test signals into the low voltage (LV) winding of the transformer for detecting faults whenever the wind or solar energy system is shut down. An equivalent circuit analysis is given to show that defects in the transformer can be detected from the change in impedance over a wide frequency range. An experimental study performed under emulated inter-laminar insulation failure and insulation contamination in the transformer is given to validate the proposed method. The study demonstrates that the proposed method can provide remote and automated detection of faults in the transformer using existing hardware with sensitivity superior to conventional tests.