Smart electrical grids consititute today a proliferating topic that introduce new technologies including electric vehicles, smart metering and demand side management. They fundamentally use renewable energy sources and provide better energy saving. The utilization of power electronics interfaces such as in photovoltaic panels, batteries, or direct current loads in the power grid results in power quality issues that affect its reliability. This chapter presents an overview of the common power quality disturbances in traditional as well as in smart grids. It discusses the techniques to measure and detect these disturbances and describes the measurement parameters and configurations in smart grid platform in order to classify and mitigate them. The chapter includes a state of art review on the detection, classification and mitigation of these disturbances. It also discusses the trends and opportunities on the open issues for the research community to deal with in the future.