When several utilities operate interconnected power systems, a voltage sag generated in the grid of one utility may affect the loads connected to other utilities. From this point of view, it has become a crucial issue to identify the location of the source of a voltage sag. This paper describes and compares the methods for voltage sag source location. The methods are applied to locate the source of voltage sags considering symmetrical and asymmetrical faults. Radial and meshed areas are also analyzed. The results show that the available methods are not totally reliable and more research is needed to extend the location methods to meshed systems