Unearthed DC or AC mains earth fault monitor - uses function or waveform generator to form reference sawtooth or triangular voltage

摘要

Earth fault monitoring of unearthed d. c. and a. c. current mains, and of apparatus operating from the mains network for the production and processing of energy, use an additionally shaped voltage such as a saw-tooth or triangular voltage generated by means of a function or waveform generator supplied from the mains network being monitored. Variations in the supplied saw-tooth or triangular voltage via a measuring instrument relative to earth is used as a measurement for the earth fault. The function generator is connected into the circuitry such that a triangular or saw-tooth voltage can be fed into a gating unit, the latter consisting of two operational amplifiers and an Optron that serves as a voltage divider within the gating unit circuitry.