At the core of the development of “Smart Transmission Grids” is the design, implementation, and testing of synchronized phasor measurement data applications that can supplement Wide-Area Monitoring, Protection, and Control Systems(WAMPAC). Nevertheless, the development of new PMU data-based WAMPAC applications has been relatively slow. The great potential of WAMPAC systems is being limited by this, and efforts are needed so that new applications can be developed. The slow rate of development of these applications is strongly related to, among other factors, the application development approach used. This article starts by discussing the needs and approaches for developing WAMPAC applications that exploit synchronized phasor measurements, and illustrates how one of these approaches has been achieved. A preliminary work carried out to develop and implement a Smart Transmission System Laboratory (SmarTS Lab), a hardware and softwarebased system for developing and analyzing “Smart Transmission Grids” paradigms and applications for WAMPAC systems, are described. The laboratory’s conceptual architecture and hardware and software implementation are presented, and some of its components are described. Finally, the article illustrates proofof-concept examples of how PMU data-based applications can be developed.