A bstract. The aim of the work is to compare the advantages and disadvantages of two feasible methods of evaluation of voltage dips “origin” intended as the network where the “fault” has probably occurred. The first method, mainly based on the simultaneous monitoring of an event by nearby primary substations connected to a common high voltage network, has been extensively applied since 2009 to the QuEEN (Quality of the Electric Energy) monitoring system data, by RSE within its research activity. The second one requests the monitoring of both primary substation medium voltage bus-bars and has been proposed as a possible method for the new on-going Italian national monitoring system, developed by the Italian DSOs, by a technical committee on National Monitoring. This method, which has been shared as a possible and feasible method by all the participants to the committee (DSOs, TSO, researchers and the Italian regulator), can be applied at a few QuEEN substations compliant with its requirements. The first method requires the knowledge of the high voltage network topology and, when applied at research level, requires time-expending visual analysis of voltage dips waveforms to compensate the lack of “confidential” information. The second method has lower effectiveness but, being a local method, can be applied also to networks including only one substation.