The Restoration Revolution: A Reliable, Real-Time Tool for Disturbance Management
For electricity providers, the responsibility – and the pressure – are enormous. However, with ageing infrastructures and growing demand, disturbances are increasingly likely to happen. Traditionally, restoration after a disturbance has been one of the most difficult things for electrical companies to handle. As system aggregation and market changes make the electrical grid even more complex, this already laborious task is made even worse.
In the face of this critical need, one company has been breaking new ground in the arena of electrical system restoration. Its unparalleled technology dramatically reduces the risk of costly power outages, and provides the means for rapid restoration. This is good news for the electrical industry and its customers. Perhaps most of all, it is good news for the man in the hot seat, the system operator.
Feeling the Heat
Picture for a moment the system operator when a disturbance occurs: amidst an avalanche of alarms, phones ringing, and harried colleagues, he faces a crisis. What tools does he have to support him? Until recently, the state of the art for restoring power after a disturbance was a compilation of offline studies – often a wall of three-ring binders in the operations room.
While hundreds of hours of systems analysis and documentation goes into restoration plans, they never match the reality of any specific disturbance. Disturbances can be dynamic: a storm, followed by fallen trees, then a fire. The operator can’t look up an ideal restoration plan for this one situation, because the situation itself is changing minute-by-minute. Plus, with new system interrelationships, the grid itself is increasingly more complex.
Even the most seasoned operator can’t rely on knowledge acquired in past circumstances to help him restore the system under new and changing conditions. He and his colleagues are left paging through volumes of painstakingly collected data that doesn’t match current conditions. As a result, there are often failures and delays before the problem can be solved.
No one would deny that the operator with the heavy responsibility to restore power deserves a more powerful tool to help him achieve that task. Today a revolutionary approach has created such a tool: the first product designed for rapid, real-time electrical system restoration.
The “Eureka” Moment
Developing a rapid, reliable restoration tool had long eluded developers because such restoration is impossible without reliable load-flow calculations. For more than 30 years, technologies based on the Newton-Raphson method have been used industry-wide to analyze the behavior of electrical power systems. This iterative approach to load flow has proved problematic in today’s environment, since it cannot effectively process large numbers of simultaneous system changes and will not function in real time when disturbances occur.
In 1991, physicist Antonio Trias was immersed in a consulting project on optimal restoration. It became clear to Trias that calculating highly accurate load flow was essential to solving the problem. Trias did extensive research, meeting with a variety of experts on the subject.
With only hours to complete his project, Trias was exhausted. An athlete, Trias often exercised to stay alert. Riding his bicycle up a mountainside in the pre-dawn hours, he had his “eureka” moment.
Trias viewed the problem from the perspective of a theoretical physicist, and took a non-iterative approach. In part, his solution allowed for the solving of the restoration problem using an A-star algorithm, which aids in identifying viable paths between the disturbance and restoration states. The potential for this approach had been identified in the past, but Trias took it further by incorporating a new, non-iterative load-flow calculation and a proprietary heuristic.
The result was nothing short of revolutionary. Trias developed a new set of algorithms that can significantly improve the reliability and restoration of electrical systems when used in place of iterative methodologies such as Newton-Raphson, as well as rules-based expert systems. Technology based on this non-iterative approach offers real-time management tools that guarantee real-world solutions, in that the solutions always correspond to the state of the physical grid.
Trias’ discovery led to the development of the Advanced Grid Observation Reliable Algorithms (AGORA™): the world’s first rapid, reliable restoration tool based on a non-iterative load-flow algorithm.
A Working Reality
AGORA allows power system operators to effectively simulate the activity on a power grid under any condition, allowing for more accurate operations and planning than ever before.
Developed with restoration as its major objective, AGORA addresses monitoring and simulation as well, offering a number of advantages over traditional methods:
- Restoration plans can be generated automatically, in real-time.
- State Estimation (SE) accuracy and robustness are improved.
- Locational Marginal Pricing (LMP) is enhanced, because the main input to LMP is SE output.
- Transmission system Available Transfer Capacity (ATC) can be accurately calculated under any system condition, in real time.
- System clearances for maintenance can be evaluated very rapidly (time is reduced from hours to minutes).
- PV and QV curves can be generated automatically, immediately.
- Contingency analysis is improved.
- A wide range of “optimization parameters” are possible, including Optimal Power Flow (OPF) calculations for optimizing generation dispatch, minimizing transmission congestion, and optimum load shedding.
The vision has become reality, and is hard at work today. Spanish utility companies including Red Electrica de Espana and the Endesa Holding have shifted away from the conventional methods of grid operations and planning to AGORA.
In 2001, PG&E became the first utility in the United States to use AGORA. What first captured their attention about this product was the unique restoration capability. Today AGORA helps PG&E manage its 18,000-mile transmission system.
Power to the People
The real power of AGORA is that its approach to load-flow calculation can provide system operators, RTOs, and even market operators with the tools they need to effectively observe and simulate activity on a power grid under any condition. It is the last statement – under any condition – where conventional technologies are not able to meet the most critical needs of operators today.
Interestingly, the only tool available for restoration also provides a path to avoid some of the conditions that result in disturbances, by creating a route to capacity maximization. In cases where a system is nearly at peak capacity, operators must keep in mind not simply generation capacity but also whether individual system elements can handle the load. To avoid system collapse and maintain required reliability reserves, operators must be conservative, because they cannot determine precisely when a problem will occur.
With AGORA, the point of potential problems can be derived with real-world accuracy. Operators can truly optimize system capacity while avoiding risk. And when unpredictable outages occur, they can do what was impossible in the past: restore systems rapidly based on real-time grid conditions. For system operators, for electricity providers, and for their customers, this capability represents a long-awaited revolution in grid management and service provision.