A Computer Based System For EHV Line Monitoring And Control

A real-time digital data-acquisition and processing system has been operating continuously since late May 78 in an Hydro-Quebec 735 kV substation. This paper describes the actual implementation and reports the operating experience. The prototype was developped in the first stage of a research project on computer-based line protection. The software is designed to accomodate (i) relaying algorithm (ii) auto verification (iii) self-evaluation and (iv) communication functions. All these functions are performed on line. Relaying algorithm consists of a one-cycle Fourier analysis and a continuous calculation of impedances. The sampling rate is controlled by the computer to synchronize to the power system frequency. Upon detection of a perturbation, five to fifty cycles of rel evant voltage and current waveform samples are "frozen" and transmitted via a phone link to IREQ main computer for permanent storage and further processing. Performances of the protection algorithm are evaluated auto matically against the actual protection system. An auto-answer modem allows the control of the remote system.