Power Management Technology secures Microgrid Resiliency

February 21, 2016 by Jeff Shepard

A new microgrid control solution from Schweitzer Engineering Laboratories, Inc. (SEL) marks the latest of University of California, San Diego's ongoing improvements to its campus electrical utility system. The recently installed high-speed islanding detection and load shedding system integrates SEL intelligent controls and adaptive wide-area protection technology with the campus' onsite generation, load and energy storage.

Today onsite generation at UC San Diego covers approximately 85 percent of the campus’ annual load and 75 percent of peak demand—a total of approximately 50MW. The remainder is imported from the San Diego Gas & Electric (SDG&E) grid. UC San Diego’s diverse portfolio includes a 2.8-MW fuel cell, 2.2-MW solar network, a 30-MW gas-turbine cogeneration plant, a 2.5-MW energy storage system and a chiller plant.

“The university’s electrical network represents a state-of-the-art microgrid system,” said Krishnanjan Gubba Ravikumar, SEL group manager. “The system is being protected by advanced wide-area monitoring and controls for ensuring overall system stability.”

The sustainable energy project, which is being hailed as the nation’s flagship microgrid system, started in the wake of the 2011 Southwest blackout. When the power outage disrupted critical operations, campus officials recognized the need for an islanded system.

“At a university like UC San Diego, the importance of ensuring a reliable source of energy cannot be overstated,” said John Dilliott, associate director of energy and utilities for the university. “As one of the nation’s 10 largest centers for science, engineering and medicine, we need to do everything possible to prevent a power supply disruption.”

To keep the system operating in harmony and help secure a steady supply of energy for its 45,000 end-customers and 450 buildings, the SEL microgrid solution uses advanced generation control and high-speed load-shedding to mitigate system blackouts. Real-time synchrophasor measurements detect islanding conditions and help the subcycle-responding microgrid controller seamlessly disconnect from the utility grid and maintain high power quality across campus.

Because operating requirements for islanded power systems change substantially after a disconnection, adaptive wide-area protection technology is used to help ensure safety of personnel and assets. Distributed energy resources can pose sensitivity and selectivity problems for protective devices since they alter fault current properties and conditions in an islanded power system. SEL’s adaptive relay protection uses selective operation of different time-current characteristic curves so the system is able to detect tripping conditions for different modes of operation.