An Algorithm for a No-Contact Digital Three-Phase Voltage Detector

Abstract

Operating-lock systems are intended to prevent emergencies and injury-causing hazards at power substations. To arrange operating locks in switch and control gear (SCG) cells, it is necessary to have technical tools of no-voltage and voltage detection on conductor buses. The use of no-contact capacitance voltage detectors is an efficient way to make the installation process less labor-intensive. A matter of substantial interest is the design of a no-contact device able to indicate the absence or supply of voltage in each separate conductor bus and initiate phase rotation. The designed voltage detector uses a system of three capacitance electric- field detectors installed in the SCG opposite to the respective lines. Each of the detectors is affected by the fields generated by all the lines when energized. Thus, the output signal of each detector is the sum of partial signals conditioned by the voltage of each separate phase. Each of the three partial components in such signals is detected by digital signal processing. The operation of the detectors under uncertainty was modeled by the Monte Carlo technique in the MATLAB environment. Each imitative test with a random set of parameters results in vector responses from the detectors. The test results help draw diagrams on a complex plane for full-phase and open-phase modes. It is shown that the pertinence of signal vectors to a specific region makes it possible to unambiguously identify the absence or supply of voltage for each separate conductor bus.