In general, a smart grid is a modernized electrical grid that uses digital technology for measurement, control, and protection functions to ensure a network security. It tries to solve the problem of weather-dependant fluctuations of renewable energy power supplies (e.g. wind turbines, or photo-voltaic systems) when they are connected to an actual power system. In two papers in this issue, we present some of the challenges raised by Smart Grids in instrumentation and measurement applications, putting emphasis on synchrophasor estimation. In this part 1 article, we describe the problem of identifying a normal condition from a fault condition and between a fault condition and an oscillation using phasor estimations in protective relays. In "Synchrophasor Measurement Challenges in Smart Grids," we discuss a novel synchrophasor- estimation algorithm that improves the accuracy of the estimates under oscillations conditions and serves to identify electromechanical modes in Smart Grids. This algorithm ameliorates protection as well as measurement applications in smart grids