Practical Approach for Current Transformer Sizing with Analytical Saturation Compensation
Аннотация
Current transformers (CTs) are essential components for accurate measurement and reliable operation of protection systems in high-voltage power networks. However, CT performance is significantly affected by magnetic core saturation and remanent flux, which may lead to distorted secondary currents, malfunction of intelligent electronic devices (IEDs), and loss of selectivity in protection schemes. Traditional verification methods defined in international and national standards such as IEC 61869, IEEE C37.110-2023, and GOST R 58669–2019 provide analytical and graphical approaches for CT sizing, but they differ in terms of accuracy and consideration of remanence. Moreover, practical challenges arise due to the limited availability of factory test data during early design stages. Recent advances in predictive diagnostics, mathematical reconstruction algorithms, and optical CT technology aim to mitigate saturation-related problems and improve reliability. This paper provides a comparative assessment of different CT sizing methods, focusing on the influence of remanent flux on saturation behavior. A 220 kV substation model with a connected Battery Energy Storage System is used as a case study. The evaluation highlights the discrepancies between IEC, IEEE, and GOST approaches and emphasizes the importance of considering remanent flux when specifying CT requirements. The obtained results demonstrate that CT class selection strongly affects the time to saturation, and neglecting remanence can lead to underestimation of risks for protection systems.