Currently, the grids are being run by aging SCADA systems with primitive communication protocols, and little or no communication between the generational plants. There is poor monitoring, poor metrics, and no real concept of distributed control…. Without human operators, there is no way to manage and monitor the grid..
“Synchrophasor” technology will improve the situation. By collecting the phase angle differences from various locations of the grid at the SAME instant, we can monitor the state of the grid and take corrective action in real time by letting the operator know where the grid is going unstable. NASPI seeks to improve the power system reliability and visibility. The NASPI community has put together the NASPInet initiative which is an effort to develop an data communications infrastructure for the electric grid. From the maintaining low-latency for coast-to-coast data transmission to supporting a network where thousands of sensors will exchange information in real time, the NASPInet initiative is perhaps one of the most demanding project in developing a real-time distributed system. At the heart of the NASPInet architecture is a Phasor Measurement Unit, or the PMU. This simple device receives a GPS clock signal and voltages and currents from the electric power system. The measured values are then time-stamped, and are called synchrophasors since they are time-synchronized phasor values. The word phasor indicates a measurement of both the signal magnitude and the angle.The PMU data does not provide new ways to remedy a fault in the grid, but provides high-fidelity information before the occurrence of the event for the operator to take corrective action.
Figure 3: PMU data for an event that occurred on February 7, 2010. The frequency excursions captured by the PMUs helped capture more accurate information about the event (Courtesy naspi.org)
A Phasor Data Concentrator (PDC) correlated the phasor data from a number of PMUs and PDCs by time and feeds it as a single stream to other applications. PDCs allow us to capture wide-area disturbances, improve system security, and coordinate substation visualization. The Phasor Gateway in NASPInet lexicon controls access to all signals from its substations. Think of it as a router that enables NASPI network to access data from within the organization by verifying cyber security, access rights, data integrity, among other things. The Phasor Gateway is extremely critical because it also manages traffic format, timing compatibility, and setting traffic priority according to classes of data.
NASPInet will enable exchange of different classes of data with different priorities. For example, NASPInet will enable exchange of large-volume historical data with high reliability but with not strict end-to-end latency needs. On the other hand, NASPInet can mandate strict latency needs on exchange of PMU data while allowing some samples to be lost. To do this, NASPI defines classes of data, which indicate the type of contract a publisher and a subscriber need to have when exchanging that class of data.
Smart grid oct10 sso
Bringing Real-Time Monitoring to the Grid
Supreet Oberoi Vice President, Engineering
DDS communications model
• Participants scope the global data space (domain)
• Topics define the data-objects (collections of subjects)
• Writers publish data on Topics
• Readers subscribe to data on Topics
• QoS Contracts control information flow
• Listeners notify the application of events
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