A group of national laboratories is working on simulations of Puerto Rico's electric transmission and distribution system to assess fuel availability and power generation options, to evaluate the use of distribution generation such as microgrids and to consider sensor deployment for improved situational awareness.

Researchers were commissioned by the Energy Department's Office of Electricity to evaluate and analyze options and to offer tools as recovery efforts continue following Hurricanes Irma and Maria, which struck the U.S. territory in the fall of 2017. Participating laboratories include Oak Ridge National Laboratory, Argonne National Laboratory, the National Renewable Energy Laboratory, Pacific Northwest National Laboratory and Sandia National Laboratories.

Hurricane Maria was the second strongest storm on record to hit Puerto Rico. By 8:00 p.m. on September 20, 2017, the Puerto Rico Electric Power Authority (PREPA) reported that nearly all of its customers were without power, with the exception of facilities running on generators.

In June, the U.S. Department of Energy released a 60-page report offering recommendations for hardening Puerto Rico’s electric power grid.

The report said that the U.S. territory’s energy infrastructure must be designed, built, managed and maintained to withstand environmental and man-made disasters, recover quickly from events and incorporate lessons learned in the wake of Hurricane Maria.

The report offers recommendations in four areas -- transmission and distribution, generation, microgrids and system operations, management and planning.

Damaged power lines along a road in Humacao, Puerto Rico. Source: Air Force photo by Master Sgt. Joshua L. DeMottsDamaged power lines along a road in Humacao, Puerto Rico. Source: Air Force photo by Master Sgt. Joshua L. DeMottsOak Ridge Model

As part of the recovery effort, scientists and engineers at Oak Ridge National Laboratory (ORNL) in Tennessee built a model of the Puerto Rico electric grid as part of the project. They created a planning model to populate protective relay schemes to safeguard the flow of electricity. Researchers also are deploying sensors across the island to monitor the grid and validate the model’s accuracy.

PREPA now has at its disposal an ORNL-developed dynamic protection-planning model that can be used to predict the electrical system's behavior in the event of severe weather or other impacts. The tool is designed to take the projected path of a hurricane and provide predictive analysis of how transmission equipment could be impacted. The information could be crucial for planning and recovery efforts.

The tool combines system planning models that utilities use to predict system behavior with detailed information about protective relay hardware. Protective relays control circuit breakers that isolate system disturbances and prevent their spread, such as when a tree falls on a power line and triggers a fault.

The simulation provides what the researchers said is a more "realistic, complete, and accurate analysis" of system events. The tool provides insight into protective relaying schemes and could yield suggestions for siting strategic infrastructure so that outages are minimized and do not cascade system-wide.

Islanding

For a power grid facing an immediate threat, the tool could support tasks such as predictive islanding. In that scenario, the tool could proactively isolate portions of the grid that are expected to be hit the hardest to keep as much of the system running as possible.

Another modeling tool being developed for Puerto Rico will analyze locations where new power generation can be sited and most cost-effectively integrated into the grid. The tool is intended to tell planners how much power can be injected into the system at different points without having to perform potentially expensive upgrades.

ORNL’s computational scientists are also evaluating locations on the island where equipment such as spare generators and transformers could be placed for easy, secure access after a natural disaster.

Monitoring

To help visualize the Puerto Rican grid and validate modeling work, ORNL researchers are deploying 20 GridEye sensors that monitor and report on the island’s grid state.

GridEye sensors such as the one shown at the top are being deployed in Puerto Rico to monitor the power grid state in real time and validate modeling and simulation tools developed by ORNL. Source: ORNLGridEye sensors such as the one shown at the top are being deployed in Puerto Rico to monitor the power grid state in real time and validate modeling and simulation tools developed by ORNL. Source: ORNLThese sensors are plugged into standard 120-volt outlets and record real-time data on electrical disturbances using a triangulation algorithm. The sensors were developed at the University of Tennessee and have been deployed at hundreds of locations across the U.S. to provide wide-area situational awareness of the grid.

In Puerto Rico, the sensors are being located inside utility substations, universities and commercial buildings. They are connected to the internet and synchronized with each other via a global positioning system to provide voltage, frequency and other measurements, and to give essential accuracy to researchers’ models.

The sensors provide data on changes such as demand load fluctuations and generator fluctuations at a much higher resolution than was possible previously on the utility system. The next phase could involve developing a tool that uses GridEye data to generate alerts to PREPA of any major system changes.

Microgrids

ORNL also is analyzing potential investments in microgrids for commercial and industrial customers. In its work for Puerto Rico’s economic development authority, researchers at Oak Ridge and at Sandia are working to provide technical analysis of proposed microgrid projects for industrial corridors. This includes analysis and selection of sites around the island where industrial properties could most benefit from microgrids. Researchers take into account fuel availability, cost and reliability constraints, local geography, existing power infrastructure, and industrial tenants.

ORNL researchers are also working on ideas to harden the grid physically with potential designs for a more flexible system of utility poles that could bend rather than break in high winds or that could be collapsed ahead of a storm to protect electric lines and then unfolded afterward.