A Placement Approach of Two-Stage Monitors Making Both Voltage Sag and Fault Position Observable

To obtain such information as voltage sag level and the reason causing voltage sag,based on monitor reach area and fault location method a two-stage placement approach of monitors,which makes the voltage sag occurred in the whole power grid and the fault position leading to the voltage sag observable,is proposed.Based on the monitor reach area method,the placement scheme of monitors for the first stage is determined to implement the voltage sag in the whole power grid observable;based on the fault location method a concept of virtual monitoring is led in and using the information of three phase bus voltage and phase angle caused by different types of faults,which is calculated by short-circuit calculation and symmetrical component method,the fault position that causes the observed voltage sag can be determined and a fault location matrix for the whole power grid can be built;through gradually increasing monitors in the residual buses all pseudo-fault points can be eliminated thus the placement scheme for the second stage is determined,thus the fault positions in the whole power grid become observable.Simulation results of IEEE 30-bus system show that the proposed method is correct and available.