Locating the source of voltage sags: Full review, introduction of generalized methods and numerical simulations

Locating the source of voltage sags in order to identify the events causing the problem and improving mitigation strategies is a major issue. When two utilities manage interconnected networks or manage a micro grid and an upstream grid, an occurred fault in one area may cause voltage sags that affect sensitive customers/critical loads in another area. From this viewpoint, this paper first reviews and analyses with detail different methods for voltage sag source location. Then eleven generalized method are introduced. A comparative analysis is performed between some of the discussed methods by applying extensive numerical simulations in a Brazilian regional utility by using PSCAD/EMTDC and MATLAB. The location of each monitor represents a difference kind of system topology (radial, interconnected, one source, two sources and interconnected microgrids). In the following, the effectiveness of methods was obtained and comprised for each monitor location and for the whole system.. The results obtained show that the effectiveness of methods based on instantaneous positive sequence components and Clarke's components is equal in many methods except distance relay and resistance sign methods, and that the effectiveness is lower, higher or equal than methods based on positive sequence phasors. The phasor based methods had less effectiveness. The generalized methods based on reactive power using instantaneous positive sequence components and Clarke's components gave the right location in 88% of total simulated cases. The results also provided a comprehensive background to propose future works and to select the best method especially at interconnection point of a micro grid with the presence of renewable distributed energy sources.