TY - JOUR N2 - In Polish coal mining, medium voltage power distribution networks operate with an insulated neutral point. Zero-sequence current transformers are the basic sensors that generate input signals for earth-fault protection relays. In the literature, the problem of frequency response analysis of various types of current transformers has been examined many times, e.g. [1] [2], but not for zero-sequence current transformers so far. As part of the work, two types of zero-sequence current transformers in the range from 0.1 Hz to 100 kHz were tested. Both the change of the current ratio and the angular shift between the transformer secondary current and the total primary current were analyzed. L1 - http://journals.pan.pl/Content/117125/PDF/94_2734_Kulinski_skl_br.pdf L2 - http://journals.pan.pl/Content/117125 PY - 2020 IS - No 4 EP - 705 DO - 10.24425/ijet.2020.134030 KW - zero-sequence current transformers KW - ground-fault protection relays KW - frequency response A1 - KuliƄski, Krzysztof A1 - Heyduk, Adam PB - Polish Academy of Sciences Committee of Electronics and Telecommunications VL - vol. 66 DA - 2020.12.02 T1 - Frequency Response Testing of Zero-Sequence Current Transformers for Mining Ground Fault Protection Relays SP - 701 UR - http://journals.pan.pl/dlibra/publication/edition/117125 T2 - International Journal of Electronics and Telecommunications ER -