Direct digital protection of h.v. d.c. convertors

It is shown that the logic state of valve currents within an h.v. d.c. convertor can be processed to provide discrete and unambiguous indication of convertor faults. A scheme consisting of the interconnection of a number of identical logic computing elements is described and is shown to have a high `fail-safe¿ potentiality. The method is based on a generalised table of valve-current states derived in a companion paper.