Specific requirements for inductive voltage transformers (VTs).
It covers transformers used in AC systems with frequencies ranging from 15 Hz to 100 Hz, typically for voltages above 1 kV, though it also provides the basis for low-voltage applications. iec 618691 pdf
An In-Depth Guide to IEC 61869-1: The Foundation for Modern Instrument Transformers typically for voltages above 1 kV