Real-Time Reliability Management Tools
California ISO Phasor Tools
Due to the long-distance nature of transmission in the west, operating uncertainties introduced by incorrect load models, generation controls that are overridden or whose performance deviates from original specifications, larger than expected energy transfers, and unanticipated combinations of outages (planned and unplanned) of major transmission elements, manifest themselves in heightened concerns regarding the dynamic stability of the grid. The real-time information required to address these concerns must be: a) collected over a wide area; b) sampled at high frequency (30 times or more per second, compared to traditional monitoring at once every 4 seconds); and, most important of all, c) precisely time-stamped so that information collected from different locations can be synchronized with each other. Phasor measurement units are a leading example of the new generation of advanced measurement technology that has these capabilities. Currently, there is reasonable deployment of these units throughout the west; however, to date, they have only been used to support off-line applications, such as model validation and post-disturbance analysis.
CERTS is working to provide real-time operators, starting with CA ISO, to provide real-time information from phasors on the dynamic stability of the grid. These data, in the long run, may also provide the basis for the introduction of a new generation of automatic grid controls. The objective is being pursued by developing and demonstrating prototype tools that rely on these measurements and that have been explicitly designed to meet CA ISO's unique specifications for these applications. Research funding for this work is being provided by the California Energy Commission Public Interest Energy Research program.
The various application displays are anchored around a central Situational Awareness dashboard display providing a visual summary on the current state of the entire system and all the monitored metrics through simplistic "Traffic Lights", "Indicators" and "Gauges" (see Figure).
RTDMS provides operators and dispatchers both real-time information and alarms on:
- Local and interconnection frequency, as well as changes in frequency that are mapped to precise generation-load imbalances within the interconnection. The local frequency measurements can be used to assess system coherency and its dynamic stress under normal operating conditions, as well as estimate the point of deceleration/acceleration during a disturbance.
- Phase angle differences across different utilities with respect to their alarming thresholds to assess the static stress across the system and its proximity to instability.
- Comprehensive voltage angle and magnitude profiles offer a birds-eye view of the sources and sinks of power and identify the high and low voltage regions within the grid.
- The MW and MVAR flows, computed from the voltage and current phasors, and the tracking of these flows with respect to predefined thresholds.
Electric Power Group, LLC