Study Of Voltage Sag Source Location And Economic Assessment Of Voltage Sag

Voltage sag has been one of the most important problems of power quality. In this paper, voltage sag source location and economic assessment are studied respectively in view of measurement and prediction. In the first part, the change of low-frequency signal energy of three-phase instantaneous power is extracted and calculated based on wavelet-multiresolution method to certain the sag source location relative to the monitoring points. The results of typical sag events when tested using this method shows that the method is simple and reliable. In the second part, sag transmission characteristic is analyzed in system side and the equipment failure rate is calculated in sensitive customer side. Then the customers'actually sag effects are assessed comprehensively by sag frequency indicators put forward in this paper and the NPV(net present value) method is selected to decide the most appropriate improvement plan.The Interval best method is proposed under the situation of uncertainty sag loss. The result of this method when applied in an plant example shows the assessment process is clear and feasible. Finally, the new idea of sag improvement that is the choice of access point for sensitive customer is proposed.