Distributing Time-synchronous Phasor Measurement Data Using the GridStat Communication Infrastructure Ryan A. Johnston, Carl H. Hauser, K. Harald Gjermundrød, and David E. Bakken Washington State University, Pullman, Washington ryan.a.johnston@gmail.com, {hauser,kgjermun,bakken}@eecs.wsu.edu Abstract The emergence of phasor measurement units (PMUs) coupled with GPS time devices makes it feasible to directly compare timestamped measurements collected at different locations without needing to account for clock drift. GridStat is a flexible publish-subscribe status dissemination middleware framework with capabilities that include rate-filtered multicast for each subscription. In this paper we explore GridStat's ability to hide the complexities of distributed systems from application developers while efficiently providing time-synchronous groups of PMU data from physically disparate locations. . 1. Introduction The growing availability of synchronous phasor measurement units (PMUs) and their deployment on power grids is making available a wealth of new real-time data about the state of the grid. PMU data contains much more information than is typically measured in existing SCADA systems. PMU measurements are synchronized and timestamped using a global clock (GPS). A PMU’s measurements, made 20 to 60 times per second, allow derivation of the bus current, voltage, phase and frequency where it is attached. Existing mechanisms for using these data are mainly targeted at collecting them in archival central repositories for use in after-the-fact analysis of system response to normal and abnormal events. These collection mechanisms have limited ability to support use of the data for real-time applications. Nevertheless, the ability to receive status data from a variety of remote locations opens new, largely unexplored opportunities for improving the power grid’s control systems to provide better reliability and efficiency. Ongoing research, [18, 19], suggests that PMU data will be valuable in fast control applications, but widespread use of such mechanisms will require a more flexible communication infrastructure than exists today. Current fast controls are either local or require dedicated point-to- point communication links. Such a communication infrastructure makes it expensive to accommodate changing needs. GridStat is a middleware framework for dissemination of operational power grid status data (both digital and analog). Middleware is a layer of software above the operating system which provides a common programming abstraction across a distributed computing system. Its high-level building blocks shield the programmer from many different kinds of heterogeneity that are inherent in a distributed system, including that of CPU, operating system, and programming language. A fundamental design motivation of GridStat was to provide flexible, managed, low-latency sharing of status data among entities that participate in operation of an interconnected power grid, [7]. GridStat’s management capabilities are intended to ease the deployment of applications by encapsulating solutions to problems such as quality of service (QoS), reliable delivery, and security in the communication infrastructure rather than leaving their solution to applications. GridStat was designed to provide high-bandwidth communication for power grid data, delivering the right data to the right computer at the right frequency with the ability to easily adapt to changing needs. GridStat and PMUs thus appear to be highly complementary technologies. In this paper we explore the fit. After describing the PMU data stream (section 2) we show how GridStat’s mechanisms (section 3) might be exploited in applications using PMU data (section 4). Of course the performance of the communication infrastructure is important if PMU data is to be used in fast controls. Section 5 presents performance results using the current GridStat prototype on emulated PMU data streams. We wrap up with a short discussion of related work (section 6). Proceedings of the 39th Hawaii International Conference on System Sciences - 2006 1 0-7695-2507-5/06/$20.00 (C) 2006 IEEE