Quantifying the Impact of Varying Inductive Burden When Inductive Current Transformers Are Used for Harmonic Current Measurements for Grid Code Compliance

When using inductive current transformers (ICTs) for harmonic current measurements, the measurement chain consists of various components that add load (burden) to the secondary circuit of a current transformer (CT). This burden can be resistive or inductive, as defined in IEC 61869 and IEEE C57.13. This article investigates and evaluates the influence of varying burdens on harmonic current measurements when outdoor (hairpin design) ICTs are used. Purely resistive and resistive-inductive burden with a power factor of 0.8 was considered-aligned with the IEC 61869 standard for power frequency measurement accuracies. The results presented in this article indicate that there is a significant increase in higher order harmonic current measuring errors when the inductive burden is connected to a CT. This is verified with simulations, where an additional stray capacitance is included in the typical CT equivalent circuit. It is therefore important to measure and quantify the burden and its influence on measurements when conducting field power quality (PQ) measurements. Once quantified, this can be used to compensate for these errors and improve the accuracy of the current harmonic measurements-especially when conducting PQ studies as part of grid code compliance.