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GPS-Based Power System Measurements and their Application

In the early 1990s, the Power Authority installed a system of GPS-based measurement devices called Phasor Measurement Units (PMU) to better understand the state’s transmission system behavior during normal and abnormal conditions. These devices provide accurate and time-synchronized snapshot measurements at their locations.  Time synchronization was not possible before the availability of the satellite-based global positioning system (GPS).  NYPA in close collaboration with the NYISO has been working on the architecture of the PMU networks, their operation and maintenance, as well as development of new applications for the PMU data.

NYPA’s Synchronized Measurement System has four separate functions:

• Geomagnetically Induced Current (GIC) monitoring, where the system records the impact of solar storms on the power grid.

• Disturbance monitoring, in which “snapshots” of transmission line power flows are taken when disturbances occur;

• Harmonics monitoring system (HMS), where periodic snapshots of the system are recorded for monitoring the level of imperfection of the power system currents and voltage waves;

• A pioneering application at NYPA’s Energy Control Center at Marcy, where synchronized measurements are fed into a state-estimator to help system operators get a better definition of the state of the system at key locations across the entire power system.

Following the blackout o f August 2003, data recorded by NYPA’s Synchronized Measurement System was one of the important sets of measurement that provided precise and time-synchronized information to help piece together the sequence of events.

This information was used internally by NYPA and shared with NYISO, NERC and DOE to determine the timeline of events and operator actions.

A post-blackout study led to task force, led to creation of the Eastern Interconnection Phasor Project (EIPP), now called the North-American Synchro-Phasor Initiative (NASPI) with a goal of improving power system reliability throughout most of the nation through wide area measurement, monitoring and control. Key to this plan is the establishment of a network of data recording instruments that monitor the equivalent of the system’s heartbeat and blood pressure, very close to real time.

Long term, NASPI’s objective is to provide early warning about possible system disturbances while they are still manageable, prevent cascading of future outages, develop advanced computational tools and offer useful data for post-disturbance analysis of wide-area events, such as in August 2003.