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Real-Time Grid Reliability Management

Publications with Abstracts

North American SynchroPhasor Initiative
2006
EIPP Real-Time Dynamics Monitoring System
Parashar, M., Electric Power Group; J. Dyer, Electric Power Group; and T. Bilke, Midwest ISO. February 2006
1 MB PDF, 8 pp

The Eastern Interconnection Phasor Projects (EIPP) is a Department of Energy (DOE) and Consortium for Electric Reliability Technology Solutions (CERTS) initiative to deliver immediate value of phasor technology to the Eastern Interconnection (EI) participants. With the current EI phasor network comprising of approximately 25 Phasor Measurement Units (PMU) and 5 Phasor Data Concentrators (PDC) is operational, this paper focuses on the efforts by the EIPP Real-Time Applications Task Team (RTTT) to develop and deploy real-time wide area monitoring capabilities on grid dynamics to operators and reliability coordinators through the Real-Time Dynamics Monitoring Systemtm (RTDMS) as well as some of the planned activities that are currently underway.

Real Time System Operations 2006 to 2007
2008
Real Time System Operations 2006 to 2007
Eto, J., M. Parashar and N. Lewis
1.6 MB PDF, 63 pp

The Real Time System Operations (RTSO) 2006-2007 project focused on two parallel technical tasks: (1) Real-Time Applications of Phasors for Monitoring, Alarming and Control; and (2) Real-Time Voltage Security Assessment (RTVSA) Prototype Tool. The overall goal of the phasor applications project was to accelerate adoption and foster greater use of new, more accurate, time-synchronized phasor measurements by conducting research and prototyping applications on California ISO&39;s phasor platform - Real-Time Dynamics Monitoring System (RTDMS) &45; that provide previously unavailable information on the dynamic stability of the grid. Feasibility assessment studies were conducted on potential application of this technology for small-signal stability monitoring, validating/improving existing stability nomograms, conducting frequency response analysis, and obtaining real-time sensitivity information on key metrics to assess grid stress. Based on study findings, prototype applications for real-time visualization and alarming, small-signal stability monitoring, measurement based sensitivity analysis and frequency response assessment were developed, factory- and field-tested at the California ISO and at BPA. The goal of the RTVSA project was to provide California ISO with a prototype voltage security assessment tool that runs in real time within California ISO&39; s new reliability and congestion management system. CERTS conducted a technical assessment of appropriate algorithms, developed a prototype incorporating state-of-art algorithms (such as the continuation power flow, direct method, boundary orbiting method, and hyperplanes) into a framework most suitable for an operations environment. Based on study findings, a functional specification was prepared, which the California ISO has since used to procure a productionquality tool that is now a part of a suite of advanced computational tools that is used by California ISO for reliability and congestion management.

Appendix A: California ISO Real-Time Voltage Security Assessment (VSA) Project: Summary of Survey Results on Methodologies for Use in Real-Time Voltage Security Assessment
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
156 KB PDF, 13 pp

The California ISO Real-Time Voltage Security Assessment (VSA) project is designed to research methods and analytic approaches for utilization in developing tools for use by dispatchers that provide real time assessment of voltage margins and contingency rankings. As the first step to achieve this objective, CERTS/EPG formulated a survey to reach out to experts in this field for comments, information, suggestions, and recommendations. The survey can be found in Appendix A. Two projects were suggested to the reviewers. The first was a proposal to develop a Real-Time Voltage Security Margin Assessment tool with the ability to identify abnormal reductions of nodal voltages, weak elements and regions most affected by voltage problems. The other was to develop a Real-Time Angle Stability Margin Assessment tool with the ability to use phasor measurement unit (PMU) data to calculate "distance to instability".

Appendix B: California ISO Real-Time Voltage Security Assessment (VSA) Summary Report
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
719 KB PDF, 50 pp

The Voltage Security Assessment (VSA) project is designed to be part of the suite of advanced computational tools for congestion management that is slated for practical applications in California in the next few years. Modern voltage assessment methods include the development of such advanced functions as identification of weak elements, automatic selection of remedial actions and automatic development of composite operating nomograms and security regions. Real-time production-grade VSA tools are becoming increasingly available nowadays. These tools are integrated with EMS/SCADA systems and use results from the state estimator.

Some advanced contemporary real-time applications already promote the idea of using the security regions determined in parameter space with the composite boundaries limited by stability, thermal, and voltage constraints. At the same time, the majority of the tools are still based on the static system power flow models and implement such traditional approaches as sink-source system stressing approach, P-V and V-Q analyses, V-Q sensitivity and modal analysis. Unfortunately, many of the most promising methods suggested in the literature have not been implemented yet in the industrial environment, including the state-of-the-art direct method to finding the exact point of collapse. Currently there exists no real-time monitoring tool for voltage security assessment. The problems of voltage security will be exacerbated by the effects of multitransfers through the network. These sets of simultaneous transfers are manifest because of the buying and selling of electric power across the boundaries of control areas. Moreover the point of production and the point of delivery may be in geographically distant locations.

An extensive analysis of existing VSA approaches was conducted. This included research by EPG, surveys from the leading experts' opinion worldwide, feedback from industrial advisors and brainstorm meetings with the projects' consultants. A state-of-the-art combination of approaches and computational engines was identified and selected for implementation in this project.

Appendix C: California ISO Real-Time Voltage Security Assessment (VSA) Prototype Functional Specifications/Prototype Development
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
94 KB PDF, 15 pp

Research and develop a voltage security assessment (VSA) prototype to monitor system voltage conditions and provide real time dispatchers with reliability information related to reactive margin, abnormal nodal voltages, weak elements and contingency rankings.

Appendix D: California ISO Phasor Application Summary Report
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
899 KB PDF, 30 pp

A PIER-funded multi-year project is currently being conducted by CERTS in cooperation with CA ISO aimed at research and demonstration activities of real-time applications of phasors for monitoring, alarming, and control. The proposed applications of phasor measurements will provide the real-time operating staff with the previously unavailable, yet greatly needed, tools to avoid voltage and dynamic instability, and monitor generator response to abnormal significant system frequency excursions. Perhaps of equal or greater importance, in the near term, the measurement infrastructure will provide California ISO with an alternate, independent real-time monitoring system that could act as an end-of-line backup for failures affecting California ISO's current Supervisory Control and Data Acquisition/Energy Management System (SCADA/EMS); in the long term, it would become a key element of California ISO's next generation monitoring system necessary for advanced real time control. Some of the proposed applications include the use of phasor measurements for wide-area visibility, real-time monitoring and alarming, small-signal stability assessment, frequency data collection, nomogram validation and improvements, improved state estimation, and real-time control.

Phasor measurement technologies are a leading example of a new generation of advanced grid monitoring technologies that rely on high speed, time-synchronized, digital measurements. These characteristics are essential for monitoring real-time grid performance, validating (or replacing) off-line nomogram studies, providing advance warning of potential grid instabilities, and, ultimately, enabling the development and introduction of advanced automatic grid control approaches (such as adaptive islanding).

Appendix F: Prototype Phasor-Based Real-Time Monitoring Software Tool — User Guide
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
2.4 MB PDF, 78 pp

The California ISO Real-Time Dynamics Monitoring System is designed to monitor the dynamics within the WECC grid and assess the system behavior during normal and disturbance conditions. Intended users are operating authorities such as independent system operators (ISOs), regional transmission organizations (RTOs), reliability coordinators, and control area dispatchers in their management of grid reliability.

Appendix G: Scoping Study Report on Improving Load and Generator Response Models
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
678 KB PDF, 82 pp

This report is a scoping study to examine research opportunities to improve the accuracy of the system dynamic load and generator models, and data and performance assessment tools used by California ISO operations engineers and planning engineers, as well as those used by their counterparts at the California utilities, to establish safe operating margins. Model-based simulations are commonly used to assess the impact of credible contingencies to determine system operating limits (path ratings, and so forth) to ensure compliance with North American Electric Reliability Corporation (NERC) and Western Electricity Coordinating Council (WECC) reliability requirements. Improved models and a better understanding of the impact of uncertainties in these models will increase the reliability of grid operations by allowing operators to more accurately study system voltage problems and the dynamic stability response of the system to disturbances.

Real-Time Grid Reliability Management PIER Final Project Report
2008
Real-Time Grid Reliability Management PIER Final Project Report
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. December 2008
661 KB PDF, 62 pp

The increased need to manage California's electricity grid in real time is a result of the ongoing transition from a system operated by vertically integrated utilities serving native loads to one operated by an independent system operator supporting competitive energy markets. During this transition period, the traditional approach to reliability management—construction of new transmission lines—has not been pursued due to unresolved issues related to the financing and recovery of transmission project costs. In the absence of investments in new transmission infrastructure, the best strategy for managing reliability is to equip system operators with better real-time information about actual operating margins so that they can better understand and manage the risk of operating closer to the edge. A companion strategy is to address known deficiencies in offline modeling tools that are needed to ground the use of improved real-time tools.

This project developed and conducted first-ever demonstrations of two prototype real-time software tools for voltage security assessment and phasor monitoring and prepared a scoping study on improving load and generator response models. Additional funding through two subsequent work authorizations has already been provided to build upon the work initiated in this project.

Appendix A: California ISO Real-Time Voltage Security Assessment (VSA) Project: Summary of Survey Results on Methodologies for Use in Real-Time Voltage Security Assessment
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
156 KB PDF, 13 pp

The California ISO Real-Time Voltage Security Assessment (VSA) project is designed to research methods and analytic approaches for utilization in developing tools for use by dispatchers that provide real time assessment of voltage margins and contingency rankings. As the first step to achieve this objective, CERTS/EPG formulated a survey to reach out to experts in this field for comments, information, suggestions, and recommendations. The survey can be found in Appendix A. Two projects were suggested to the reviewers. The first was a proposal to develop a Real-Time Voltage Security Margin Assessment tool with the ability to identify abnormal reductions of nodal voltages, weak elements and regions most affected by voltage problems. The other was to develop a Real-Time Angle Stability Margin Assessment tool with the ability to use phasor measurement unit (PMU) data to calculate "distance to instability".

Appendix B: California ISO Real-Time Voltage Security Assessment (VSA) Summary Report
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
719 KB PDF, 50 pp

The Voltage Security Assessment (VSA) project is designed to be part of the suite of advanced computational tools for congestion management that is slated for practical applications in California in the next few years. Modern voltage assessment methods include the development of such advanced functions as identification of weak elements, automatic selection of remedial actions and automatic development of composite operating nomograms and security regions. Real-time production-grade VSA tools are becoming increasingly available nowadays. These tools are integrated with EMS/SCADA systems and use results from the state estimator.

Some advanced contemporary real-time applications already promote the idea of using the security regions determined in parameter space with the composite boundaries limited by stability, thermal, and voltage constraints. At the same time, the majority of the tools are still based on the static system power flow models and implement such traditional approaches as sink-source system stressing approach, P-V and V-Q analyses, V-Q sensitivity and modal analysis. Unfortunately, many of the most promising methods suggested in the literature have not been implemented yet in the industrial environment, including the state-of-the-art direct method to finding the exact point of collapse. Currently there exists no real-time monitoring tool for voltage security assessment. The problems of voltage security will be exacerbated by the effects of multitransfers through the network. These sets of simultaneous transfers are manifest because of the buying and selling of electric power across the boundaries of control areas. Moreover the point of production and the point of delivery may be in geographically distant locations.

An extensive analysis of existing VSA approaches was conducted. This included research by EPG, surveys from the leading experts' opinion worldwide, feedback from industrial advisors and brainstorm meetings with the projects' consultants. A state-of-the-art combination of approaches and computational engines was identified and selected for implementation in this project.

Appendix C: California ISO Real-Time Voltage Security Assessment (VSA) Prototype Functional Specifications/Prototype Development
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
94 KB PDF, 15 pp

Research and develop a voltage security assessment (VSA) prototype to monitor system voltage conditions and provide real time dispatchers with reliability information related to reactive margin, abnormal nodal voltages, weak elements and contingency rankings.

Appendix D: California ISO Phasor Application Summary Report
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
899 KB PDF, 30 pp

A PIER-funded multi-year project is currently being conducted by CERTS in cooperation with CA ISO aimed at research and demonstration activities of real-time applications of phasors for monitoring, alarming, and control. The proposed applications of phasor measurements will provide the real-time operating staff with the previously unavailable, yet greatly needed, tools to avoid voltage and dynamic instability, and monitor generator response to abnormal significant system frequency excursions. Perhaps of equal or greater importance, in the near term, the measurement infrastructure will provide California ISO with an alternate, independent real-time monitoring system that could act as an end-of-line backup for failures affecting California ISO's current Supervisory Control and Data Acquisition/Energy Management System (SCADA/EMS); in the long term, it would become a key element of California ISO's next generation monitoring system necessary for advanced real time control. Some of the proposed applications include the use of phasor measurements for wide-area visibility, real-time monitoring and alarming, small-signal stability assessment, frequency data collection, nomogram validation and improvements, improved state estimation, and real-time control.

Phasor measurement technologies are a leading example of a new generation of advanced grid monitoring technologies that rely on high speed, time-synchronized, digital measurements. These characteristics are essential for monitoring real-time grid performance, validating (or replacing) off-line nomogram studies, providing advance warning of potential grid instabilities, and, ultimately, enabling the development and introduction of advanced automatic grid control approaches (such as adaptive islanding).

Appendix F: Prototype Phasor-Based Real-Time Monitoring Software Tool — User Guide
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
2.4 MB PDF, 78 pp

The California ISO Real-Time Dynamics Monitoring System is designed to monitor the dynamics within the WECC grid and assess the system behavior during normal and disturbance conditions. Intended users are operating authorities such as independent system operators (ISOs), regional transmission organizations (RTOs), reliability coordinators, and control area dispatchers in their management of grid reliability.

Appendix G: Scoping Study Report on Improving Load and Generator Response Models
Eto, J., M. Parashar, B. Lesieutre, and N. Lewis. October 2008
678 KB PDF, 82 pp

This report is a scoping study to examine research opportunities to improve the accuracy of the system dynamic load and generator models, and data and performance assessment tools used by California ISO operations engineers and planning engineers, as well as those used by their counterparts at the California utilities, to establish safe operating margins. Model-based simulations are commonly used to assess the impact of credible contingencies to determine system operating limits (path ratings, and so forth) to ensure compliance with North American Electric Reliability Corporation (NERC) and Western Electricity Coordinating Council (WECC) reliability requirements. Improved models and a better understanding of the impact of uncertainties in these models will increase the reliability of grid operations by allowing operators to more accurately study system voltage problems and the dynamic stability response of the system to disturbances.

Reliability Adequacy Tools
2008
NERC Frequency Monitoring and Analysis (FMA) Application: Functional Specifications
CERTS - Electric Power Group. December 2008
1.0 MB PDF, 32 pp

For the last three years, NERC, with the assistance of the Department of Energy (DOE) and the Consortium for Electric Reliability Technology Solutions (CERTS), has been developing and deploying various components of the Reliability Monitoring and Compliance Platform (RMCP) block for Wide- Area Monitoring and Compliance. One of the components of the NERC RMCP is the Frequency Monitoring and Analysis application which has been specified as part of NERC responses to some of the August 14, 2003 blackout recommendations, and is being developed to gather, transmit, process, archive, and provide access to Interconnections frequency phasor data to allow NERC Subcommittees and Staff for timely post analysis of frequency abnormalities, frequency response analysis, and to help validate new reliability performance metrics.

The purpose of this document is to define the functional requirements for the NERC Frequency Monitoring and Analysis (FMA) project using the North American Syncro Phasor Initiative (NASPI) phasor infrastructure with TVA serving as host for Eastern interconnection frequency data source, both for real time and for archived phasor frequency data. The document describes the adopted Hardware- Software architectures using Phasor measurements based on requirements specified by NERC Resources Subcommittee. This document also describes requirements for wide area frequency data collection, alarm, event data collection and archiving, data processing and storage, user Interface and visualization requirements.

Synchronized Sampling Uses for Real-Time Monitoring and Control/RTGRM: Implementation Specification for Visualization Tools
Kezunovic, M. and C. Zheng. December 2008
1.4 MB PDF, 55 pp

This report is the third deliverable from several consecutive research and development activities. Prior work on the project explored requirement specifications and functional design for the control center visualization tools.

During this phase of the project, the implementation specification of our proposed graphical user interface (GUI) software has been developed and explained in detail. The main research achievements are:

  • The overall implementation flow chart of the software has been developed and explained;
  • Both external and internal logic of the software represented in the implementation flow chart have been specified;
  • The Object-oriented Programming (OOP) technique has been selected as the primary programming technique;
  • The software programming flow chart has been defined and general programming sequence has been established;
  • Two types of data interpreters have been explained; detailed inputs and outputs of the interpreters have been specified;
  • The programming specification of all GUI modules within the graphical software has been outlined and block diagrams for each module has been specified;
  • Options for receiving satellite images from commercial providers have been investigated;
  • The hierarchical view, which is for normal state monitoring purpose, is set to be a combination of four other views: model, equipment, aerial and topological.
  • Implementation plans for software maintenance and security considerations during development have been specified;
  • A general schedule for developing the graphical software is established, which has specified three phases throughout the programming process;

Since the implementation specification for the graphical tools has been outlined, our investigation will now move on to the development of the control center visualization software. As soon as the whole development of GUI is completed, on-site demonstration using field cases will be carried out.

Statistical Analysis of Abnormal Behavior: Project Overview
Ferryman, T., and B. Amidan. November 2008
1.1 MB PDF, 26 pp

This report documents the interim status of PNNL work conducted over the several months associated with developing an analysis capability to monitor the electrical power grid and alert domain experts of abnormal events as detected by this multivariate analysis tool. The report draws from material presented to domain experts on October 16 and 22, 2008. This report is organized as follows:

  • Section 1 describes the background of this ongoing project.
  • Section 2 describes the overall goals of the project.
  • In Section 3, the PNNL approach and technical accomplishments achieved to date are noted. Included are enumeration of the 12 major steps and key R&D breakthroughs in selective steps.
  • Section 4 presents concluding remarks.

Although the R&D effort on this project is not complete, this report provides an update on the current status of work and progress to date toward the objective of this initial proof-of-concept study.

Synchronized Sampling Uses for Real-Time Monitoring and Control/RTGRM: Functional Design for Visualization Tools
Kezunovic, M. and C. Zheng. October 2008
1.1 MB PDF, 38 pp

Prior work on the project explored requirement specifications for the control center visualization tools. This report is the second deliverable from several consecutive research and development activities.

During this second phase of the project, we focused our efforts on designing functionalities of the proposed graphical user interface (GUI) software. A set of specific solutions for the GUI applications, as well as the user interfaces have been discussed in detail in this document. The main research achievements are:

  • The design for the overall control center visualization GUI tool has been specified for future applications
  • The GUI has two parts: one for fault event view (fault location) and the other for the power system monitoring view in the normal state (alarm processor).
  • The functions of GUI for each application module (fault location and alarm processor) have been specified in detail;
  • For faulted systems, four different views are proposed: equipment model view, aerial view, electrical view and topological view;
  • Hierarchical view is proposed for the purpose of supervision of normal state of the power system;
  • Construction view and operational view using equipment models are designed to better demonstrate behavior of different devices;
  • Both 2-D satellite image and 3-D models are integrated to represent an aerial view module;
  • Real-time power flow and transmission line alarms are displayed in the electrical view. Component connection and equipment status are shown in topological view;
  • Other features such as detection of cascading events and risk based failure analysis for power apparatus could be added to the GUI in the future.

Now when the functional design for GUI has been specified, our investigation will move on to the implementation specifications and development of the visualization tools. As soon as the whole development of GUI is completed, on-site demonstration using field cases will be carried out.

Real-Time Voltage Security Assessment (RTVSA) Summary Report
Parashar, M., and A. Agarwal, Electric Power Group; Y. Makarov, Pacific Northwest National Laboratory; and I. Dobson, University of Wisconsin, Madison. June 2008
965 KB PDF, 49 pp

Over the past 40 years, more than 30 major blackouts worldwide were related to voltage instability and collapse. Among them, at least 13 voltage-related blackouts happened in the United States, including two major blackouts in the Western Interconnection in 1996 and a wide-scale blackout in the Eastern Interconnection in 2003. Several times, the blackout investigation teams indicated the need for on-line power flow and stability tools and indicators for voltage performance system-wide in a real-time. These recommendations are not yet completely met by the majority of U.S. power system control centers. The gap between the core power system voltage and reliability assessment needs and the actual availability and use of the voltage security analysis tools was a motivation to come forward with this project. The project's aim was to develop state-of-the-art methodologies, prototypes, and technical specifications for the Real-Time Voltage Security Assessment (RTVSA) tools. These specifications can be later used by selected vendors to develop industrial-grade applications for California ISO, other California Control Area Operators, and utilities in California.

An extensive analysis of existing VSA approaches was conducted. This included research by Consortium for Electric Reliability Technology Solutions (CERTS), surveys from the leading experts' opinion worldwide, feedback from industrial advisors, and brainstorm meetings with the projects' industry and academia consultants. A state-of-the-art combination of approaches and computational engines was identified and selected for implementation in this project. Subsequently, a multi-year project roadmap was developed which has guided the CERTS research on evaluating and demonstrating the recommended approaches on the California ISO test cases.

Real-Time Voltage Security Assessment (RTVSA) Report on Algorithms & Framework
Parashar, M., and A. Agarwal, Electric Power Group; Y. Makarov, Pacific Northwest National Laboratory; I. Dobson, University of Wisconsin, Madison. June 2008
675 KB PDF, 73 pp

Over the past 40 years, more than 30 major blackouts worldwide were related to voltage instability and collapse. Among them, at least 13 voltage-related blackouts happened in the United States, including two major blackouts in the Western Interconnection in 1996 and a wide-scale blackout in the Eastern Interconnection in 2003. Several times, the blackout investigation teams indicated the need for on-line power flow and stability tools and indicators for voltage performance system-wide in a real-time. These recommendations are not yet completely met by the majority of US power system control centers. The gap between the core power system voltage and reliability assessment needs and the actual availability and use of the voltage security analysis tools was a motivation to come forward with this project. The project aims to develop state-of-the-art methodologies, prototypes and technical specifications for the Real-Time Voltage Security Assessment (RTVSA) tools. These specifications can be later used by selected Vendors to develop industrial-grade applications for California Independent System Operator (CA ISO), other California Control Area Operators, and utilities in California.

Phasor Technology Applications Feasibility Assessment and Research Results Report
Parashar, M., and W. Zhou, Electric Power Group; D. Trudnowski, Montana Tech; Y. Makarov, Pacific Northwest National Laboratory; I. Dobson, University of Wisconsin, Madison. June 2008
2.5 MB PDF, 66 pp

Phasor technology is one of the key technologies on the horizon that holds great promise towards improving grid reliability, relieving transmission congestion, and addressing some of today's operational challenges within the electric industry. This technology complements existing SCADA systems by providing the high sub-second resolution and global visibility to address the new emerging need for wide area grid monitoring, while continuing to use existing SCADA infrastructure for local monitoring and control.

Recent advances in the field of phasor technologies offer new possibilities in providing the industry with tools and applications to address the blackout recommendations and to tackle reliability management and operational challenges faced by system operators and reliability coordinators. The utilization of real-time phasor measurements in the fields of visualization, monitoring, protection, and control is expected to revolutionize the way in which the power grid of the future can identify and manage reliability threats and will respond to contingencies.

Phasor measurement data provide precise real-time direct monitoring capability of the power system dynamics (beyond the static view currently available via SCADA) at a very high rate. They also have the capability of accurately estimating and dynamically tracking various system parameters that provide a quantitative assessment of the health of system under the current operating condition and the prevalent contingency. In particular, synchronized phasor measurements provide an accurate sequence of snap-shots of the power system behavior at a very high rate (30 samples per second) along with precise timing information. The timing information is essential for real-time continuous estimation of system parameters that classify the power system. A precise estimate of the load, generator and/or network parameters consequently provide the most accurate assessment of the system limits of the current operating system. This time series data along with real-time system parameter estimates based on the data can be utilized to improve stability nomogram monitoring, small signal stability monitoring, voltage stability monitoring and system frequency response assessment. A main advantage of such methodologies is that they can measure actual system states and performance and do not rely on offline studies for its assessment, nor do they rely on comprehensive system models, which can be outdated or/and inaccurate.

Real-Time Voltage Security Assessment (RTVSA) Algorithm's Simulation & Validation Results
Parashar, M., and A. Agarwal, Electric Power Group. January 2008
308 KB PDF, 21 pp

The Real-Time Voltage Security Assessment (RTVSA) project is designed to be part of the suite of advanced computational tools for congestion management that is slated for practical applications in California within the next couple of years. Modern voltage assessment methods include the development of such advanced functions as identification of weak elements, automatic selection of remedial actions and automatic development of composite operating nomograms and security regions. With all the research advancements in the area of Voltage Security Assessment over the past few decades, the feasibility of deploying production-grade VSA tools that run in real time and integrate with existing EMS/SCADA systems utilizing results from the state estimator, are increasingly becoming a reality.

Some advanced contemporary real-time applications already promote the idea of using the security regions with the composite boundaries limited by stability, thermal, and voltage constraints. At the same time, the majority of these tools are still based on the static system power flow models and implement such traditional approaches as sink-source system stressing approach, P-V and V-Q analyses, V-Q sensitivity and modal analysis. Unfortunately, many of the most promising methods suggested in the literature have not been implemented yet in the industrial environment, including the state-of-the-art direct method to finding the exact Point of Collapse. Currently there exists no real-time monitoring tool for voltage security assessment. The problems of voltage security will be exacerbated by the effects of multi-transfers through the network. These sets of simultaneous transfers are manifest because of the buying and selling of electric power across the boundaries of control areas. Moreover the point of production and the point of delivery may be in geographically distant locations.

The RTVSA application is based on an extensive analysis of the existing VSA methodologies, by surveying the leading power system experts' opinion worldwide, and also with feedback from industrial advisors. Through this process, a state-of-the-art combination of approaches and computational engines was identified and selected for implementation in this project. The suggested approach is based on the following principles and algorithms:

  • Use the concepts of local voltage problem areas and descriptive variables influencing the voltage stability problem in each area. Utilize information about the known voltage problem areas and develop formal screening procedures to periodically discover new potential problem areas and their description parameters.
  • Use the descriptive variable space to determine the sequence of stress directions to approximate and visualize the boundary. The stress directions are based on pre-determined generation dispatches and load scaling patterns..
  • Use hyperplanes to approximate the voltage stability boundary.
  • To calculate the approximating hyperplanes, apply a combination of the parameter continuation techniques and direct methods as suggested in this report. Introduce a sufficient additional security margin to account for inaccuracies of approximation and uncertainties of the power flow parameters.
  • Compute the control actions most effective in maintaining a sufficient security margin.
  • Produce a list of abnormal reductions in nodal voltages and highlight the elements and regions most affected by potential voltage problems. The list of most congested corridors in the system will be ranked by the worst-case contingencies leading to voltage collapse.

The initial framework of this project was originally formulated by California ISO. The key elements of the suggested approach which are the use of parameter continuation, direct methods, and the hyperplane approximation of the voltage stability boundary were approved by a panel of leading experts in the area in the course of a survey conducted by Electric Power Group, LLC (EPG) in 2005. These concepts were also verified in the course of face-to-face personal meetings with well-known university professors, industry experts, software developers and included email discussions and telephone exchanges. CERTS industrial advisors approved these developments during various CEC Technical Advisory Committee (TAC) meetings conducted in the past years.

In 2005, the project development team successfully implemented the parameter continuation predictor-corrector methods. Necessary improvements were identified and developed. The PSERC parameter continuation program and MATLAB programming language were used in the project. During 2006-07, research work included the implementation of Direct Methods to quickly and accurately determine the exact Point of Collapse (PoC), Boundary Orbiting techniques to trace the security boundary, the investigation of descriptive variables, and the validation of techniques for analyzing margin sensitivities.

The above mentioned techniques have been tested using a ~6000 bus state estimator model covering the entire Western Interconnection and for the Southern California problem areas suggested by California ISO. These results are presented within this report.

2007
Real-Time Voltage Security Assessment (RTVSA) Tool Functional Specifications For Commercial Grade Application
Parashar, M., Electric Power Group; A. Agarwal, Electric Power Group; Y. Makarov, Pacific Northwest National Laboratory; and I. Dobson, University of Wisconsin, Madison. April 2007
633 KB PDF, 30 pp

Voltage stability is the ability of a power system to maintain acceptable voltages at all buses in the system under normal operating conditions and after being subjected to a disturbance. A system enters a state of voltage instability when a disturbance, increase in load demand, or change in system condition cause a progressive and uncontrollable decline in voltage. The main factor causing voltage instability is the inability of the power system to meet the demand for reactive power. Voltage collapse is the process or sequence of events accompanying voltage instability which leads to a low unacceptable voltage profile in a significant part of the system.

Objectives

Develop functional specifications for a Real-Time Voltage Security Assessment (RTVSA) tool that monitors voltage stability margin in real time, and help the real time dispatchers to manage this margin by controlling VAR resources, generation dispatch, and other resources on the transmission system. This application is expected to seamlessly integrate with the CA ISO's real-time network analysis sequence (EMS) and run automatically after each successful state estimation process at every 5 minute intervals or on demand. The tool will help to identify the following:

  1. Available voltage security margin
  2. The most dangerous stresses in the system leading to voltage collapse
  3. Worst-case contingencies resulting in voltage collapse and/or contingencies with insufficient voltage stability margin
  4. Contingency ranking according to a severity index for voltage stability related system problems
  5. Weakest elements within the grid and the regions most affected by potential voltage problems
  6. Controls to increase the available stability margin and avoid instability
  7. Information about voltage problems at the look-ahead operating conditions and for the worst-case contingencies (contingencies with large severity ranks) that may appear in the future
  8. A real-time dispatcher's situational awareness-type wide area graphic and geographic displays.

Approach

An extensive analysis of existing VSA approaches was conducted. This included research by Consortium for Electric Reliability Technology Solutions (CERTS), surveys from the leading experts' opinion worldwide, feedback from industrial advisors and brainstorm meetings with the projects' industry and academia consultants. A state-of-the-art combination of approaches and computational engines was identified and selected for implementation in this project. Subsequently, a multi-year project roadmap was developed which has guided the CERTS research on evaluating and demonstrating the recommended approaches on the CA ISO test cases.

This document describes the design, functional and visualization requirements for a Real-Time Voltage Security Assessment (RTVSA) tool, as well as CA ISO's preferences on certain implementation and visualization techniques.

2006
CA ISO Phasor Applications Summary Report
Consortium for Electricity Reliability Technology Solutions (CERTS). February 2006
899 KB PDF, 30 pp

A PIER TRP funded multi-year project is currently being conducted by CERTS in cooperation with CA ISO aimed at research and demonstration activities of Real-Time Applications of Phasors for Monitoring, Alarming, and Control. The proposed applications of phasor measurements will provide the real-time operating staff with the previously unavailable, yet greatly needed, tools to avoid voltage and dynamic instability, and monitor generator response to abnormal significant system frequency excursions. Perhaps of equal or greater importance, in the near term, the measurement infrastructure will provide CA ISO with an alternate, independent real-time monitoring system that could act as an end-of-line backup for failures affecting CA ISO's current SCADA/EMS; in the long term, it would become a key element of CA ISO's next generation monitoring system necessary for advanced real time control. Some of the proposed applications include the use of phasor measurements for wide-area visibility, real-time monitoring and alarming, small-signal stability assessment, frequency data collection, nomogram validation and improvements, improved state estimation, and real-time control.

Phasor measurement technologies are a leading example of a new generation of advanced grid monitoring technologies that rely on high speed, time-synchronized, digital measurements. These characteristics are essential for monitoring real-time grid performance, validating (or replacing) off-line nomogram studies, providing advance warning of potential grid instabilities, and, ultimately, enabling the development and introduction of advanced automatic grid control approaches (such as adaptive islanding).

CA ISO Real-Time Voltage Security Assessment (RTVSA) Summary Report
Electric Power Group. February 2006
719 KB PDF, 50 pp

The Voltage Security Assessment (VSA) project is designed to be part of the suite of advanced computational tools for congestion management that is slated for practical applications in California in the next few years. Modern voltage assessment methods include the development of such advanced functions as identification of weak elements, automatic selection of remedial actions and automatic development of composite operating nomograms and security regions. Real-time production-grade VSA tools are becoming increasingly available nowadays. These tools are integrated with EMS/SCADA systems and use results from the state estimator.

2005
CA ISO Voltage Security Assessment (VSA) Functional Specification Prototype Development
Consortium for Electricity Reliability Technology Solutions (CERTS) and Electric Power Group. May 2005
94 KB PDF, 15 pp

Research and develop a Voltage Security Assessment (VSA) prototype to monitor system voltage conditions and provide real time dispatchers with reliability information related to reactive margin, abnormal nodal voltages, weak elements and contingency rankings.

CA ISO Real Time Voltage Security Assessment (VSA) Project: Summary of Survey Results on Methodologies for Use in Real Time Voltage Security Assessment
Consortium for Electricity Reliability Technology Solutions (CERTS) and Electric Power Group. April 2005
156 KB PDF, 13 pp

The CA ISO Real Time Voltage Security Assessment (VSA) project is designed to research methodologies and analytic approaches for utilization in developing tools for use by dispatchers that provide real time assessment of voltage margins and contingency rankings. As the first step to achieve this objective, CERTS/EPG formulated a survey to reach out to experts in this field for comments, information, suggestions, and recommendations. The Survey can be found in Appendix A. Two projects were suggested to the reviewers. The first was a proposal to develop a Real-Time Voltage Security Margin Assessment tool with the ability to identify abnormal reductions of nodal voltages, weak elements and regions most affected by voltage problems. The other was to develop a Real-Time Angle Stability Margin Assessment tool with the ability to use Phasor Measurement Unit (PMU) data to calculate "distance to instability".

2003
Supplier and Control Area Performance Monitoring System: Utilization of Grid-3P for Automatic Generation Control (AGC), Frequency Response Reserves (FRR) and Ancillary Services (AS) Regulation
Martinez, C., J. Dyer, and M. Skowronski, Electric Power Group. February 2003
347 KB PDF, 20 pp

The Consortium for Electric Reliability Technology Solutions (CERTS) has been working with NERC, Regional Transmission Organizations, Independent System Operators, and other electric industry organizations to research, develop, and disseminate new methods, tools and technologies to protect and enhance the reliability of the U.S. electric power system under the emerging competitive electricity market structures. The monitoring system offers a base from which grid security and market efficiency can be improved to help protect the market from "gaming" and other forms of market manipulations. CERTS has developed the Grid Real-Time Performance Monitoring and Prediction Platform (Grid-3P) to manage grid reliability and monitor market performance in real time. The purpose of the Supplier and Control Area Performance Monitoring System is to provide real-time intelligence on grid operations that will enable operators to monitor performance of Suppliers to provide competitive services and respond to their performance in a predictable manner.

Real-Time Voltage Monitoring and VAR Management System©
Martinez, C., J. Dyer, and M. Skowronski, Electric Power Group. February 2003
279 KB PDF, 20 pp

The Consortium for Electric Reliability Technology Solutions (CERTS) has been working with NERC, Regional Transmission Organizations, Independent System Operators, and other electric industry organizations to research, develop, and disseminate new methods, tools and technologies to protect and enhance the reliability of the U.S. electric power system under the emerging competitive electricity market structures. This Summary Report provides a description of the Real-Time Voltage Monitoring and VAR Management System tool being developed to provide the capability to monitor grid and market performance in real-time and manage grid reliability.

2002
CERTS Area Control Error (ACE)-Frequency Real-Time Monitoring System
Electric Power Group. October 2002
739 KB PDF, 14 pp

The ACE-Frequency Monitoring System using CERTS' Grid-3P, will enable NERC Reliability Coordinators to monitor ACE-Frequency performance and compliance with performance operational guides within their jurisdictions, and will also allow NERC Staff and Subcommittees to analyze and assess control data to improve reliability performance. The ACE-Frequency Real-Time Monitoring System translates raw operational control data into meaningful operations performance information for end users. Should an abnormal interconnection frequency occur, a Real-Time Interconnection Abnormal Frequency Notification (AFN) is automatically issued via email or beepers describing the date, time, and magnitude of the frequency abnormality to specific Operational Authorities, NERC Resources Subcommittee members, and NERC Staff. The notification recipients using the ACE-Frequency Monitoring System functionality can quickly assess the abnormality's root cause by drilling down from wide-area to local-area visualization displays that include appropriate information and analysis graphs to easily identify and assess those control area(s) out of compliance and potential originators of the notified interconnection frequency abnormality.

The key elements of the ACE-Frequency Monitoring System include the following:

  • Enables monitoring of ACE for each of the 123 Control Areas operating in the U.S. The data is updated every one to four minutes.
  • The Grid-3P visualization infrastructure provides color coded graphics displays indicating status of a region control area, reliability authority or interconnection.
  • Monitoring functions that provide details of various functions allowing users to drill down to the desired level of data and graphic displays for key diagnostics.
  • The Real Time Interconnection Abnormal Frequency Notification (AFN) issues email notifications and enables the user to assess the root-cause for abnormal frequencies.
  • ACE-Frequency Data Collection Tool archives raw data from the NERC Database for review and analysis.
Human Factors Aspects Of Power System Voltage Visualizations
Wiegmann, D.A., A.M. Rich, T.J. Overbye, and Y. Sun. Proceedings of the 35th Hawaii International Conference on System Sciences. September 2002
181 KB PDF, 6 pp

This paper presents experimental results associated with the human factors aspects of using color contours to visualize electric power system bus voltage magnitude information. Participants were divided into three groups: the first group only one-line numeric data, the second only one-line contour data, while the third saw both. The purpose of the experiment was to determine how quickly participants could both acknowledge low voltage violations and perform corrective control actions. Results indicated the contour only visualization resulted in the quickest voltage violation acknowledgments, while the numeric data only visualization resulted in the quickest solution times. Testing was done using a modified version of the IEEE 118 bus system.

CAISO-CERTS Synchronized Phasor Measurements Applications User Guide
Consortium for Electricity Reliability Technology Solutions (CERTS). March 2002
1015 KB PDF, 70 pp

This user guide is intended for the operations engineering staff that will be utilizing synchronized phasor measurement (SPM) base applications to measure and analyze post disturbance analysis. This will be done via an integration of three separate tools. They are as follows:

  • PSMTools — Pacific Northwest National Lab
  • Synchronized Phasor Management Outlook Tool — Southern California Edison
  • Streamreader and PhasorFile Tools — Bonneville Power Administration

Information for hands-on use of these tools is presented in the Tools section of this User's Guide. Theoretical background information, such as systems architecture, engineering value information, and fundamentals that are not directly applicable to the hands-on use of the tools, is available in the Appendix.

For the purposes of this Users Guide, these three tools will collectively be referred to as Synchronized Phasor Measurement Tools (SPM).

PSMTools R 12 — The system developed at Pacific Northwest National Lab (PNNL), was developed for analysis only, and was not designed for monitoring.

Phasor Management Outlook Tool R 0.9 — The system developed at Southern California Edison was intended for both monitoring and analyzing the data.

StreamReader and PhasorFile Tools R 1.0 — The system developed at Bonneville was intended for monitoring the data only. There is no function for analysis.

The four major processes for the utilization of synchronized phase measurements are:

  • Data Acquisition
  • Post Disturbance Analysis
  • Result analysis, Model Validation, and Remediation Planning
  • RAS Threshold Validation

Further details for each of these high level processes can be found in the Appendix.

This guide is intended for post disturbance analysis and model validation only. Once the data has been gathered, the raw data can be cleaned and filtered and the post disturbance analysis can begin. Phase-2 of the CERTS project will produce a complement user guide for dispatchers.

2001
Human Factors Analysis Of Power System Visualizations
Overbye, T.J., D.A. Wiegmann, A.M. Rich, and Y. Sun. Proceedings of the 34th Hawaii International Conference on System Sciences. September 2001
394 KB PDF, 6 pp

This paper describes an experimental approach to formally testing the usability of different power system visualizations. In particular, the ability of participants to assess and correct power system voltage problems was tested. Participants were divided into three groups: the first group only saw tabular data, the second group one line data, while the third group saw one-line data and a color voltage contour. The time to acknowledge the voltage violations and the time to correct the violations were assessed.

Grid Reliability Management Tools
Eto, J., Lawrence Berkeley National Laboratory; C. Martinez, Southern California Edison; and J. Dyer and V. Budhraja, Electric Power Group. IEEE Power Engineering Society Winter Meeting. January 28-31, 2001
36 KB PDF, 5 pp

Evidence of reliability challenges comes from increasing incidence of transmission congestion, price spikes, voltage degradation, and managed and unmanaged outages are all indicators of stress on the system. Traditional grid operations and reliability management strategies and tools did not envision today's high-pressure environment in which there are increased demands on existing corridors to support greater trade. In particular they did not envision reliance on a competitive market for the buying and selling of electricity and reliability-related (or ancillary) services. Operators are being constantly challenged to manage these increasingly unpredictable power flows with an aging and increasingly inflexible transmission infrastructure. The tools and technologies available for this task - developed originally to support centrally-planned, vertically-integrated operations—are currently inadequate for managing reliability in competitive, region-wide electricity markets.

In 1999, for the first phase of its work in the area of Real-Time Grid Reliability Management, CERTS created prototypes for operational software tools to help dispatchers maintain and enhance electric system reliability (see Figure 1). The Department of Energy's Transmission Reliability program funded the initial development of the prototypes. The California Energy Commission's Public-Interest Energy Research Program is currently funding demonstrations of the prototypes at the California Independent System Operator (ISO). CERTS is also in discussions with utilities and ISO's in other regions of the country, as well as the North American Electric Reliability Council for additional demonstrations and extensions of these prototypes.

2000
Reliability Adequacy Tool for Ancillary Services
Consortium for Electric Reliability Technology Solutions. April 2000
525 KB PDF, 45 pp

CERTS is developing a series of integrated computer base reliability adequacy tools that will help power system Operating Authorities (e.g. ISOs, RTOs and Security Coordinator) comply with the North American grid reliability standards. As part of the integrated approach, an Ancillary Services Performance, Tracking and Predictive Adequacy Application (ASPTP) is being developed for a Host Control Area located within the Western System Coordinating Council (WSCC).

The purpose of this document is to define the functional and design specifications for a ASPTP application for Ancillary Services such as Regulation, Operating Reserves Spinning, Operating Reserves Non-Spinning and Replacement Reserves. The functionality of this application has been identified and defined based on current market processes used to acquire Ancillary Services in California and on the reliability standards of three organizations, a) NERC and its Policy 1 and 10, which addresses generation control and ancillary services. b) The WSCC and its reliability policies and guidelines and, c) additionally, feedback from other CERTS related projects.

The document also describes the process to define the graphic-geographic visual components and perspectives that will allow for effective visual analysis to respond to the new operational challenges raised by competitive and deregulated environments and operations of bigger and more complex control areas.
System Security Tools
2006
Slow Coherency Based Controlled Islanding - A Demonstration of the Approach on the August 14, 2003 Blackout Scenario
Yang, B., V. Vittal, and G.T. Heydt.
464 KB PDF, 9 pp

This paper demonstrates the use of a slow coherency based generator grouping algorithm and a graph theoretic approach to form controlled islands as a last resort to prevent cascading outages following large disturbances. The proposed technique is applied to a 30,000-bus, 5000-generator, 2004 summer peak load, Eastern Interconnection data and demonstrated on the August 14, 2003 blackout scenario. Adaptive rate of frequency decline based load shedding schemes are used in the load rich islands to control frequency. The simulation results presented show the advantage of the proposed method in containing the impact of the disturbance within the islands formed and in preventing the impact of the disturbance from propagating to the rest of the system. This is demonstrated by the significant reduction in line flows in the rest of the system and by improved voltage and relative angle characteristics. Based on the suggestion in the joint US-Canadian task force final report on the blackout, load shedding without any islanding is also performed and results obtained are compared with the proposed controlled islanding method. The islanding method outperforms the load shedding only method in reducing the transmission line flows but both methods have similar effects on voltage and relative angle behavior.

2005
Risk Analysis of Critical Loading and Blackouts with Cascading Events
Dobson, I., and B. Carreras. January 2005
4.4 MB PDF, 147 pp

The project overall objective is to contribute to transmission system reliability by understanding large, cascading failure blackouts. The project analyzes cascading failure and large blackout risk by developing and studying power system and probabilistic models of cascading failure. These models show that blackout risk can sharply increase at a critical loading as power system loading is increased and can explain the distribution of blackout sizes observed in NERC data. The probabilistic models show how to relate the tendency for failures to propagate to the probability of various sizes of blackouts.

2004
System Islanding Using Minimal Cutsets with Minimum Net Flow
Wang, X., and V. Vittal. October 2004
250 KB PDF, 6 pp

Slow coherency has effectively proved its capability in determining sets of generator groups among weak connections in any given power system. In this paper, we provide two comprehensive approaches to deal with islanding the actual system based on the grouping information, by using the minimal cutsets technique in graph theory. The issue of minimal cutsets has been widely discussed in areas related to network topology determination, reliability analysis, etc. The results of this paper also show potential in application to power system islanding. The verification of the islanding scheme is provided based on a WECC 179-Bus, 29-Generator test system.

Integrated Security Analysis Final Report
Sauer, P.W., University of Illinois at Urbana-Champaign; K. Tomsovic, Washington State University; J. Dagle, S. Widergren, T. Nguyen and L. Schienbein, Pacific Northwest National Laboratory. July 2004
725 KB PDF, 72 pp

As economic pressures result in greatly expanded utilization of facilities, the issue of power system security analysis is key to reliable operation at maximum efficiency. Security analysis in this context refers to the ability of a power system to withstand pre-specified disturbances called contingencies. This report presents results on the identification of the current state of power system security analysis for operations and the potential integration of the various existing power system security analysis tools. Current security analysis consists of numerous software tools (some off-line and some on-line) that predict operator guidelines for transaction scheduling. A survey of selected operators in representative locations in both the East and Western US was conducted to determine the effectiveness of current tools and the need for future improvements. The primary outcome of that survey indicated that:

  • There is a wide variation of satisfaction with the quality of the models used
  • Network model reduction is done offline
  • Virtually all operators are satisfied with their SCADA systems
  • Virtually all operators have operational online power flow tools
  • Most operators are satisfied with their state estimation tools
  • Most operators are satisfied with their static contingency analysis tools
  • Very few optimal power flow (OPF) tools are in use
  • Almost no security constrained OPF tools are in use
  • Some voltage analysis or dispatch is done off line
  • Almost all transient stability analysis is done off line
  • Virtually no midterm, long-term, or eigenvalue stability analysis is performed

This project also investigated alternative frameworks for the integration of existing tools into a comprehensive package that can be more responsive to changing conditions and simultaneous transactions. This portion of the project leveraged resources with a Power Systems Engineering Research Center (PSERC) project by the same title. These alternative frameworks build on the availability of raw data from existing security tools for both static and dynamic considerations as follows:

  • On-line estimation of security margins using current operating practices
  • Creation of families of estimators, each specialized for specific system limits
  • Testing of estimators on simulated systems
  • Automate the process of evaluating security margins in off-line studies

The results show that it is possible to accurately estimate security margins for large systems on-line. The main limitation of the approach resides in the ability of time-consuming off-line studies to accurately model system dynamics. Directions for further development are proposed in a Roadmap For Future Security Analysis.

Probabilistic Load-Dependent Cascading Failure with Limited Component Interactions
Dobson, I., University of Wisconsin; B. Carreras, Oak Ridge National Lab; and D. Newman, University of Alaska. IEEE International Symposium on Circuits and Systems, Vancouver Canada. May 2004
109 KB PDF, 4 pp

We generalize an analytically solvable probabilistic model of cascading failure in which failing components interact with other components by increasing their load and hence their chance of failure. In the generalized model, instead of a failing component increasing the load of all components, it increases the load of a random sample of the components. The size of the sample describes the extent of component interactions within the system. The generalized model is approximated by a saturating branching process and this leads to a criticality condition for cascading failure propagation that depends on the size of the sample. The criticality condition shows how the extent of component interactions controls the proximity to catastrophic cascading failure. Implications for the complexity of power transmission system design to avoid cascading blackouts are briefly discussed.

2003
Blackout Mitigation Assessment in Power Transmission Systems
Carreras, B.A., V.E. Lynch, D.E. Newman, and I. Dobson. Hawaii International Conference in Systems Sciences. January 2003
422 KB PDF, 10 pp

Electric power transmission systems are a key infrastructure and blackouts of these systems have major direct and indirect consequences on the economy and national security. Analysis of North American Electrical Reliability Council blackout data suggests the existence of blackout size distributions with power tails. This is an indication that blackout dynamics behave as a complex dynamical system. Here, we investigate how these complex system dynamics impact the assessment and mitigation of blackout risk. The mitigation of failures in complex systems needs to be approached with care. The mitigation efforts can move the system to a new dynamic equilibrium while remaining near criticality and preserving the power tails. Thus, while the absolute frequency of disruptions of all sizes may be reduced, the underlying forces can still cause the relative frequency of large disruptions to small disruptions to remain the same. Moreover, in some cases, efforts to mitigate small disruptions can even increase the frequency of large disruptions. This occurs because the large and small disruptions are not independent but are strongly coupled by the dynamics.

A Probabilistic Loading-dependent Model of Cascading Failure and Possible Implications for Blackouts
Dobson, I., B.A. Carreras, and D.E. Newman. Hawaii International Conference in Systems Sciences. January 2003
193 KB PDF, 9 pp

A model has been developed to study the global complex dynamics of a series of blackouts in power transmission systems [1, 2]. This model has included a simple level of self-organization by incorporating the growth of power demand and the engineering response to system failures. Two types of blackouts have been identified with different dynamical properties. One type of blackout involves loss of load due to lines reaching their load limits but no line outages. The second type of blackout is associated with multiple line outages. The dominance of one type of blackouts versus the other depends on operational conditions and the proximity of the system to one of its two critical points. The first critical point is characterized by operation with lines close to their line limits. The second critical point is characterized by the maximum in the fluctuations of the load demand being near the generator margin capability. The identification of this second critical point is an indication that the increase of the generator capability as a response to the increase of the load demand must be included in the dynamical model to achieve a higher degree of self-organization. When this is done, the model shows a probability distribution of blackout sizes with power tails similar to that observed in real blackout data from North America.

2002
An Initial Complex Systems Analysis of the Risks of Blackouts in Power Transmission Systems
Dobson, I., D.E. Newman, B.A. Carreras, and V.E. Lynch. Power Systems and Communications Infrastructures for the Future. September 2002
250 KB PDF, 7 pp

Electric power transmission systems are a key infrastructure and blackouts of these systems have major direct and indirect consequences on the economy and national security. In particular, electric power blackouts have cascading effects on other vital infrastructures. While it is useful to analyze the detailed causes of individual blackouts, in this paper we focus on the intrinsic dynamics of series of blackouts and how this complex system dynamics impacts the assessment and mitigation of blackout risk. Indeed, the mitigation of failures in complex systems needs to be approached with care.

Congestion Management Requirements, Methods and Performance Indices
Kirby, B.J., J.W. Van Dyke, C. Martinez and A. Rodriguez. Report: ORNL/TM-2002/119. June 2002
774 KB PDF, 56 pp

Catastrophic disruptions of large, interconnected infrastructure systems are often due to cascading failure. For example, large blackouts of electric power systems are typically caused by cascading failure of heavily loaded system components. We introduce the CASCADE model of cascading failure of a system with many identical components randomly loaded. An initial disturbance causes some components to fail by exceeding their loading limit. Failure of a component causes a fixed load increase for other components. As components fail, the system becomes more loaded and cascading failure of further components becomes likely. The probability distribution of the number of failed components is an extended quasibinomial distribution. Explicit formulas for the extended quasibinomial distribution are derived using a recursion. The CASCADE model in a restricted parameter range gives a new model yielding the quasibinomial distribution. Some qualitative behaviors of the extended quasibinomial distribution are illustrated, including regimes with power tails, exponential tails, and significant probabilities of total system failure.

Dynamics, Criticality and Self-organization in a Model for Blackouts in Power Transmission Systems
Carreras, B.A., I. Dobson, V.E. Lynch, and D.E. Newman. Hawaii International Conference in Systems Sciences. January 2002
223 KB PDF, 16 pp

Catastrophic disruptions of large, interconnected infrastructure systems are often due to cascading failure. For example, large blackouts of electric power systems are typically caused by cascading failure of heavily loaded system components. We introduce the CASCADE model of cascading failure of a system with many identical components randomly loaded. An initial disturbance causes some components to fail by exceeding their loading limit. Failure of a component causes a fixed load increase for other components. As components fail, the system becomes more loaded and cascading failure of further components becomes likely. The probability distribution of the number of failed components is an extended quasibinomial distribution. Explicit formulas for the extended quasibinomial distribution are derived using a recursion. The CASCADE model in a restricted parameter range gives a new model yielding the quasibinomial distribution. Some qualitative behaviors of the extended quasibinomial distribution are illustrated, including regimes with power tails, exponential tails, and significant probabilities of total system failure.

Examining Criticality of Blackouts in Power System Models with Cascading Events
Dobson, I., J. Chen, J.S. Thorp, B.A. Carreras, and D.E. Newman. Hawaii International Conference in Systems Sciences. January 2002
350 KB PDF, 10 pp

As power system loading increases, larger blackouts due to cascading outages become more likely. We investigate a critical loading at which the average size of blackouts increases sharply to examine whether the probability distribution of blackout sizes shows the power tails observed in real blackout data. Three different models are used, including two simulations of cascading outages in electric power transmission systems. We also derive and use a new, analytically solvable model of probabilistic cascading failure which represents the progressive system weakening as the cascade proceeds.

2001
Complex Systems Approach to Cascading Failures
Carreras, B.A., I. Dobson and J.S. Thorp. December 2001
954 KB PDF, 56 pp

This document is the first year report of a two-year CERTS (Consortium for Electric Reliability Technology Solutions) project studying large scale blackouts and cascading failures of electric power transmission systems. The project is inventing new methods, models and analysis tools from complex systems, selforganized criticality, probability, and power systems engineering so that the risks of large blackouts and cascading failures can be understood and mitigated from novel global and top-down perspectives.

Time-space Methods for Determining Locational Reserves: A Framework for Location Based Pricing and Scheduling for Reserve Markets
Thorp, J., C.E. Murillo-Sanchez and B. Thomas. November 2001
301 KB PDF, 20 pp

Currently there are no well functioning reserve markets in use in the US. There is some evidence that a well functioning reserve market can help mitigate price spikes and solve the capacity problem. Currently reserves are thought of as having time dependent properties, that is, they must be spinning or able to synchronize in ten minutes or able to synchronize in thirty minutes. However, it is well known that given a network that can become constrained on voltage or real power flows, reserves must also be spatially located in order to handle all the contingencies that could occur. To date, there is no credible science-based method for assigning reserves in this way. Virtually all methods are ad-hoc and are based on engineering judgment and experience. The purpose of this work is to develop a sound basis and a methodology for assigning both real energy as well as reactive reserves.

Advanced Measurements and Control
2010
MANGO — Modal Analysis for Grid Operation: A Method for Damping Improvement through Operating Point Adjustment
Huang, Z., R. Diao, N. Zhou, J.C. Fuller, F.K. Tuffner, W.A. Mittelstadt, Y. Chen, J.F. Hauer, D.J. Trudnowski, and J.E. Dagle. October 2010
2.7 MB PDF, 92 pp

Small signal stability problems are one of the major threats to grid stability and reliability in the U.S. power grid. An undamped mode can cause growing oscillations and may result in system breakups and large-scale blackouts. There have been several incidents of system-wide oscillations. Of those incidents, the most notable is the August 10, 1996 western system breakup, a result of undamped system-wide oscillations. Significant efforts have been devoted to monitoring system oscillatory behavior from measurements in the past 20 years. The deployment of phasor measurement units (PMU) provides highprecision, time-synchronized data needed for detecting oscillation modes. Measurement-based modal analysis, also known as ModeMeter, uses real-time phasor measurements to identify system oscillation modes and their damping. Low damping indicates potential system stability issues. Modal analysis has been demonstrated with phasor measurements to have the capability of estimating system modes from oscillation signals, probing data, and ambient data.

With more and more phasor measurements available and ModeMeter techniques maturing, there is yet a need for methods to bring modal analysis from monitoring to actions. The methods should be able to associate low damping with grid operating conditions, so operators or automated operation schemes can respond when low damping is observed. The work presented in this report aims to develop such a method and establish a Modal Analysis for Grid Operation (MANGO) procedure to provide recommended actions (such as generation re-dispatch or load reduction), and aid grid operation decision making for mitigating inter-area oscillations. This project directly contributes to the Department of Energy Transmission Reliability Program's goal of "improving reliability of the nation's electricity delivery infrastructure."

2008
Smart Transmission Grid Applications and Their Supporting Infrastructure
Bose, Anjan. October 2008
181 KB PDF, 18 pp

In this paper we assume that time synchronized measurements will be ubiquitously available at all high voltage substations at very high rates. We examine how this information can be utilized more effectively for real time operation as well as for subsequent decision making. This new information available in real time is different, both in quality and in quantity, than the real time measurements available today. The promise of new and improved applications to operate the power system more reliably and efficiently has been recognized but is still in conceptual stages. Also, the present system to handle this real time data has been recognized to be inadequate but even conceptual designs of such infrastructure needed to store and communicate the data are in their infancy.

In this paper, we first develop an information infrastructure to handle ubiquitous phasor measurements recognizing that the quantity and rate of data would make it impossible to store all the data centrally as done today. Then we discuss the new and improved applications, classified into two categories: one is the set of automatic wide area controls and the other is the set of control center (EMS) functions with special attention to the state estimator. Finally, given that the availability of phasor measurements will grow over time, the path for smooth transition from the present day systems and applications to those developed here is delineated.

2007
Automated Circuit Breaker Monitoring
Kezunovic, M., Maja Knezev, Zarko Djekic. November 2007
2.6 MB PDF, 159 pp

A complete system for automated monitoring of multiple circuit breakers is developed for DOE by Texas A&M University. This system is characterized by a wireless-based architecture for data communication between newly developed Circuit Breaker Monitors (CBMs), as well as concentrator computer with intelligent software for automated analysis.

Circuit breakers are very important elements of the electrical power system. Usually, circuit breakers are manually initiated to interrupt current flow during normal operating conditions. They may also be automatically initiated to interrupt short-circuit currents during faults. The ability to operate a breaker and isolate a portion of the power system is very critical task and circuit breakers must be very reliable.

This document consists of three parts. The first two parts give the hardware and software prototype specification respectively. The third part provides details of the filed demonstration. The solution is aimed at automating the analysis of switching sequences using GPS-synchronized records from the control circuitry collected by CBM devices installed at each breaker.

Hardware report is described in PART 1. It defines improvements in the circuit breaker monitoring (CBM) device made during the year 2006. Signal conditioning board, communication protocol and time synchronization module have been modified and upgraded. These modifications are necessary to enable monitoring over the entire power system and to reduce cost of the device. Report presents lab and field-test setups. Two CBM units are developed and installed at CNP substation in south Houston area. Functional requirement specification for automated circuit breaker monitoring device is created and attached in the appendix. Final reports for year 2003 and 2005 are also provided in the appendices of PART 1.

The software specification is given in PART 2. This part of the report describes the types of sequences to be analyzed and their properties of interest. The specification outlines the system architecture pointing out how multiple CBM devices are synchronized using GPS receivers located in substations. The specification gives details of the requirements for the application software consisting of modules that perform signal processing for feature extraction and expert system reasoning for analysis conclusions. The specification of the software also includes detailed requirements for the user interface, which is needed at a location where the users of the information are situated. The specification outlines requirements for software testing.

Third part (PART 3) presents in-service demonstration of hardware and software developed for DOE by Texas A&M University. The topology builder software is used to provide spatial component of the sequence analysis. This tool enables user to draw topology of the power system, which should be analyzed. The Sequence Analyzer application, which makes it possible to track sequence of events and make conclusions about their effect, is demonstrated. Finally, status of hardware is briefly presented, which is specified in more details in PART 1.

This solution is developed and tested at a prototype stage and is now ready for further design tuning and filed deployment leading to a commercial product.

2005
Archiving and Management of Power Systems Data for Real-Time Performance Monitoring Platform
Martinez, C., Electric Power Group; H. Huang, and R. Guttromson, Pacific Northwest National Laboratory. January 2005
643 KB PDF, 40 pp

The intent of this document is to lay a general foundation for effective and systematic management of data and information for real-time performance monitoring of large power systems. It does so through a consideration of overall data applications, and by drawing upon industry experience in the operation of wide area measurement systems. The treatment of these topics is intendedly broad, and digressions into underlying details have been avoided so far as possible. The reader may note, for example, that the distinction between data and information is not absolute—e.g., the information produced by one process may serve as raw input for some later process at higher level. There is also some ambivalence in terms such as "archive" and "real time." Their meaning was fairly clear for analog data streams, but it is much less so for high performance digital systems. Such terminology should be interpreted according to context, and with support from the various cited references. A Glossary is provided in Section 9 as a guide to acronyms.

2004
Real-Time Monitoring and Assessment of Circuit Breaker Operations for Diagnostics and Control Applications
Kezunovic, M., G. Latisko, and N. Ved, Texas A&M University. December 2004
342 KB PDF, 14 pp

Circuit breakers (CBs) are very important elements in the power system. They are used to switch other equipment in and out of service. Circuit breakers need to be reliable since their incorrect operation can cause major issues with power system protection and control. Today's practice in monitoring circuit breaker operation and status in real time is reduced to the use of Remote Terminal Units (RTUs) of Supervisory Control and Data Acquisition (SCADA) system to assess CB status. More detailed information about the control circuit performance may be obtained by CB test equipment typically used for maintenance diagnostics [1].

This paper addresses two important issues: a) how improved CB monitoring may be implemented in real-time, and b) what would be the benefits of such an implementation.

The results reported in this paper are coming from two research projects, conducted using funding from CenterPoint Energy and DOE-CERTS aimed at development of software for automated analysis of CB data and the other covering development of the CB data acquisition unit respectively. The paper is devoted to description of a prototype implementation of a real-time CB monitoring system. The system consists of a new CB monitoring data acquisition IED that is located at circuit breaker and captures detailed information about its operation in real-time. The CB files are transferred to the concentrator PC where the application software performs automated analysis and makes an assessment about the operational status of the breaker. The software is based on signal processing and expert system processing. Application example using actual field data is discussed.

The paper ends with some conclusions, acknowledgments and a list of references.

"Data Acquisition Unit" Requirements and Specifications CERTS Project Final Report for FY 03
Kezunovic, M., and P. Teodorovic, Texas A&M University. August 2004
342 KB PDF, 14 pp
2003
Software Requirements Specification for Management for Grid Control
Smathers, D., L. Kidd, S. Goldsmith, L. Phillips, D. Bakken, A. Bose, and D. McKinnon. April 2003
29.4 MB PDF, 80 pp

This Software Requirements Specification defines the functions of a simulation power grid model. The model defines grid control functions that focus on real-time control and related communication of information among entities that share the operation of the power grid. Deregulation of the power markets necessitates increased communications among entities who have economic motivation to restrict access to important information from other market participants. New power market concepts will impact how planning and real-time control are performed. The simulation power grid model provides the tool for investigating issues of distributed computing, data sharing, data access, communication system capacity, and communications reliability. The model enables researchers to develop intelligent distributed control agents for managing Area Control Error and transmission security. The software requirements specification is defined using a subset of the Unified Modeling Language, a class diagram describing all of the objects along with their attributes, methods, and some modified use cases.

Communication Models for Third Party Load Frequency Control
Bhowmik, S., K. Tomsovic, and A. Bose. 2003
296 KB PDF, 6 pp

With deregulation of the power generation sector, the necessity for an enhanced and open communication infrastructure to support an increasing variety of ancillary services is apparent. A duplex and distributed communication system seems to be the most suitable solution to meet and ensure good quality of these services. Parameters needed and additional limits introduced by this new communication topology must be investigated and defined. This paper focuses on the communication network requirements for a third party load frequency control service. Data communication models are proposed based on queuing theory. Simulation is performed to model the effects of certain types of signal delays on this ancillary service.

2002
A New Scheme for Voltage Control in a Competitive Ancillary Service Market
Nobile, E., and A. Bose. 14th PSCC, Sevilla, 24-28 June 2002
423 KB PDF, 5 pp

This paper shows how a competitive ancillary service market for voltage control/reactive power might operate and what it might look like, given the eminently local nature of the service. An automatic voltage control would dynamically manage the reactive power available in a certain geographic region and a local market in reactive power could then be developed similarly to that proposed for the load-following ancillary service. Coordination among these regions would be required.

2000
Increasing Information Flow Between PDCs
Dart, E., Sandia National Laboratory. December 2000
87 KB PDF, 5 pp

The goal is to be able to receive, on a local PDC, all the phasor data collected by a remote PDC. For a fully configured PDC, this means 16 PMUs, with 10 phasors per PMU for a total of 160 phasors. For a fully configured expanded PDC, this means 32 PMUs, with 10 phasors per PMU for a total of 320 phasors.

Dynamic Performance Validation in the Western Power System
Hauer, J.F., M.J. Beshir, and W.A. Mittelstadt, in association with the WSCC Performance Validation Task Force APEX 2000 Conference in Kananaskis, Alberta. October 2000
246 KB PDF, 8 pp

Accurate knowledge and prediction of system behavior is essential to the reliable and economic operation of large power systems. This paper describes the efforts underway to meet this need in the western system.

Agent Concept for Intelligent Distributed Coordination in the Electric Power Grid
Smathers, D., and S. Goldsmith, Sandia National Laboratories. April 6, 2000
278 KB PDF, 15 pp

Intelligent agents and multi-agent systems promise to take information management for real-time control of the power grid to a new level. This report presents our concept for intelligent agents to mediate and coordinate communications between Control Areas and Security Coordinators for real-time control of the power grid. An appendix describes the organizations and publications that deal with agent technologies.

Operating Environment and Functional Requirements for Intelligent Distributed Control in the Electric Power Grid
Smathers, D., and A. Akhil, Sandia National Laboratories. April 3, 2000
301 KB PDF, 22 pp

The restructuring of the U.S. power industry will surely lead to a greater dependence on computers and communications to allow appropriate information sharing for management and control of the power grid. This report describes the operating environment for system operations that control the bulk power system as it exists today including the role NERC plays in this process. Some high-level functional requirements for new approaches to control of the grid are listed followed by a description of the next research steps that are needed to identify specific information management functions.

http://certs.lbl.gov