Automated Inverter-Embedded Testing of Step-Up Transformers in Renewable Energy Systems

초록

Transformers are employed in renewable energy systems such as wind and solar power generation for stepping up the voltage supplied to the grid. They are known to have higher failure rates compared to grid transformers, as they are exposed to a hostile environment and fluctuating operating conditions. However, testing relies on on-site tests, which are costly to perform as they are installed in remote locations that are difficult to access. In this paper, a new approach for transformer testing using the inverter available in the system, is proposed. The main idea is to use the inverter as the test equipment for injecting test signals into the transformer low voltage (LV) winding to obtain the frequency response of admittance for detecting faults whenever the renewable energy system is de-energized. An equivalent circuit analysis is given to show that defects in the core, winding, insulation, and LCL filter can be detected from the change in admittance over a wide frequency range, similar to frequency response analysis (FRA) commonly used for transformer testing. Experimental test results of the proposed method and FRA performed on a 380/690V, 15 kVA, 3 phase transformer are given under emulated core insulation failure, insulation contamination, and poor electrical contacts for validation.

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