Protective systems. Part IV: Automatic selective isolation of sustained earth faults on a network protected by Petersen coils

This paper explains what is believed to be a unique method evolved for protection of a grid network of 37.5-kV transmission lines against line-to-earth faults, which enables automatic selection and isolation of a section subjected to a sustained fault to take place without utilizing earth-fault current for the operation of protective relays, or pilot wires between sectionalizing stations remote from one another. The scheme provides for the installation of Petersen coils together with special automatic selectors and associated equipment, and has been employed with considerable success since 1936 for protection of the Ganges Canal hydro-electric grid in the United Provinces, India.