Non-conventional instrument current transformer test set for industrial applications

Due to the increasing presence of renewable energies and advances in power electronics, the power systems are nowadays working with more and more disturbing sources. Increasing performances are then required to voltage and current instrument transformers, in terms of both accuracy and frequency bandwidth. With reference to these requirements, low power non-conventional instrument transformers, which typically show better performances than the conventional inductive instrument transformer, are expected to rapidly diffuse in power system monitoring applications. Because of the low level of their output, the calibration of such instruments cannot be performed with the classical set-ups designed for conventional instrument transformers. In the paper, a test set for the calibration of non-conventional current instrument transformer working with current down to the 0.1 mA level, is presented. The considered set-up, intended for use in industrial environment, allows calibration from DC to 4 kHz with target uncertainties within 100 μA/A and 100 μrad. The working principle and the configuration of the developed test set are discussed and preliminary experimental results related to its characterization are shown.