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The transient monitoring (TM) function occupies a very important place in digital protection devices. Its role is to detect as quickly and precisely as possible any significant change in the behavior of incoming voltage and current measurements (i.e., a change in the signal model). It is indeed believed that fault inceptions and switching events occurring in the vicinity of the protective relay can be detected by the monitoring of the voltages and currents. The precise time of jump detection allows, for example, the relay to place data windows at a correct position and to trigger accurate protection calculations. Accurate signal change detection could also be implemented in digital fault recorders (as a starting condition) or even in offline event analysis for phasor synchronization or fault location. By nature, ADAMO is an adaptive transient monitor: the filter coefficients and filter length keep changing to adapt to the incoming signals. The method is based on a least square minimization of the residual signal given by a short Fourier filter with two adapted coefficients. At a very low computation cost, the algorithm gets rid of all the disadvantages of the classical methods and allows a greater sensitivity.
Date of Publication: Jan. 2004