Regenerative Active Electronic Load With Current, Voltage and Frequency Control for Power Transformer Testing

The long duration test of electrical equipment is an important tool for users and manufacturers to determine precise information as, for example, equipment operational limits, lifespan, thermal behavior, etc. Although useful, these long duration tests are usually conducted using passive elements such as in the burn-in test, consuming a great amount of energy and with limited flexibility to emulate different loading profiles (e.g., current and voltage levels, harmonics content, etc.). In this context, to perform tests in power transformer emulating its real operation conditions can be a difficult task, since the standards procedures do not emulate the loading levels and the burn-in test consumes a high quantity of energy. Moreover, in distribution networks, the transformers are submitted to an increasing level of nonlinear voltage and current. Thus, it is important to test them under these conditions. The use of active electronic loads (AEL) is an alternative to solve these problems since the device structure can have regenerative proprieties and its control can emulate different types of load. This paper presents an AEL to perform tests in power transformers with low energy consumption that is capable of imposing controlled voltage and current (frequency, level, and harmonic distortion) to the transformer under test. The proposed methodology is validated by experimental results of a 50 kVA prototype.