The Crystal Ball Gazing with Electrostatic Precipitators: V-I Curves Analysis

Abstract

Have you dreamed about knowing what happens inside an electrostatic precipitator (ESP) without opening it? Well, the main defects can be revealed using voltage — current curves. When the unit is operating, it is impossible to intervene in the electrofilter. Many parameters can be used to demonstrate an increase in dust emission levels which might result in a malfunctioning of the ESP itself or of other components of the unit. When the external elements of the electrostatic precipitator have been eliminated, attention can be focused on the Electrostatic precipitator itself. If a diagnosis can be performed “in state” before shutting down the unit, valuable gains can be made in time and efficiency during the maintenance operation. V-I curves constitute an invaluable aid, indeed, they are the signature of the ESP itself and are more precise than the maximum recorded voltage and current points. The voltage-current curves were obtained in experimental pilot conditions and in an industrial situation to demonstrate the four main defects most commonly encountered in ESP. the fouling of the emissive wires; the misalignment of plates and wires; insulators problems; the presence of back-corona. In parallel, a modelling of the physical phenomena corresponding to these defects confirmed the modification of the curve. So, it is possible to predict the defects by analysing the V-I curves. To facilitate the V-I curves analysis of a significant size ESP, software was created in order to give: a display by field and file, the V-I curves; a comparison of different sets of data to follow the evolution of the curves; a defect mapping (clogging, misalignment or insulators problem, back-corona). Subsequent validation on different ESP of the EDF fleet confirmed the power and the reliability of the software.