ABSTRACT
Signal conditioning is the function of preparing a signal for processing by the application algorithms. In the case of the control processes in power supply substations, this involves primarily digital filtering and less frequently correlation or the determination of the symmetrical components. The positive, negative and zero-sequence components of three-phase sinusoidal variables are measured in order to determine the degree of their imbalance. The symmetrical components of a three-phase system can be obtained directly using orthogonal functions. Digital versions of the analogue symmetrical component filters could be constructed without difficulty, but it is better to take advantage of digital techniques to obtain the phase-shifts needed. The orthogonal components can be similarly determined when using filters based on even and odd Walsh functions or other functions symmetrically or antisymmetrically disposed to the center of the data window.
