references

A 230 kV transmission line fault led to customer-initiated simultaneous loss of approximately 1,500 MW of voltage-sensitive load that was not anticipated by the BES operators. The electric grid has not historically experienced simultaneous load losses of this magnitude in response to a fault on the system, which has historically been planned for large generation losses but not for such significant simultaneous load losses. Simultaneous large load losses have two effects on the electric system: First, frequency rises on the system as a result of the imbalance between load and generation; second, voltage rises rapidly because less power is flowing through the system. In this incident, the frequency did not rise to a level high enough to cause concern. The voltage also did not rise to levels that posed a reliability risk, but operators did have to take action to reduce the voltage to within normal operating levels. However, as the potential for this type of load loss increases, the risk for frequency and voltage issues also increases. Operators and planners should be aware of this reliability risk and ensure that these load losses do not reach intolerable levels.

This Glossary lists each term that was defined for use in one or more of NERC’s continent-wide or Regional Reliability Standards and adopted by the NERC Board of Trustees from February 8, 2005 through February 26, 2025

The PJM Manual for Emergency Operations focuses on how PJM and the PJM Members are expected to respond to emergency conditions and is the designated PJM RC, BA and TOP Operating Plan to mitigate operating Emergencies per EOP-011.

The fundamental principles, essential functions, and optional functions of a virtual synchronous machine (VSM) to make power electronic converters standardized for different applications and suitable for single-unit operation, multi-unit operation, islanded/off-grid operation, and grid-tied operation, facilitating the large-scale utilization of DER and the integration of power electronic converters into the grid, and advancing energy freedom and energy access are defined in this standard.

NERC is a not-for-profit international regulatory authority with the mission to assure the reliability of the BPS in North America. NERC develops and enforces Reliability Standards; annually assesses seasonal and long-term reliability; monitors the BPS through system awareness; and educates, trains, and certifies industry personnel. NERC’s area of responsibility spans the continental United States, Canada, and the northern portion of Baja California, Mexico. NERC is the ERO for North America and is subject to oversight by the U.S. Federal Energy Regulatory Commission (FERC, also known as the Commission) and governmental authorities in Canada. NERC’s jurisdiction includes users, owners, and operators of the North American BPS and serves more than 334 million people. Section 39.11(b) of FERC’s regulations provides that “The Electric Reliability Organization shall conduct assessments of the adequacy of the Bulk-Power System in North America and report its findings to the Commission, the Secretary of Energy, each Regional Entity, and each Regional Advisory Body annually or more frequently if so ordered by the Commission.”

The Energy Act of 2020 calls for the U.S. Department of Energy to make available to the public an update to Lawrence Berkeley National Laboratory’s prior study entitled United States Data Center Energy Usage Report (2016). This report, designed to meet that Congressional request, estimates historical data center electricity consumption back to 2014, relying on previous studies and historical shipment data. This report also provides a scenario range of future demand out to 2028 based on new trends and the most recent available data.

Chairman Willie Phillips dissented from the decision on the “first of its kind” co-location proposal, saying it could harm national security and grid reliability.

The State of Reliability (SOR) report seeks to inform regulators, policymakers, and industry leaders on the most significant reliability risks facing the BPS and describe the actions that the ERO Enterprise has taken and will take to address them. This year’s SOR report is comprised of two publications: this 2024 SOR Technical Assessment, which provides NERC’s comprehensive annual technical review of BPS reliability for the 2023 operating (calendar) year, and the 2024 SOR Overview, which is a high-level summary of the Technical Assessment, summarized by important findings.

This document explains the technical rationale and justification for the proposed Reliability Standard TPL-008-1. It provides stakeholders and the ERO Enterprise with an understanding of the technology and technical requirements in the Reliability Standard. This Technical Rationale and Justification for TPL-008-1 is not a Reliability Standard and should not be considered mandatory and enforceable.

The PJM Manual for Transmission Operations is one of a series of manuals within the Transmission set. This manual focuses on specific transmission conditions and procedures for the operation of the Bulk Electric System and Designated Transmission Facilities.

The PJM Manual for Energy Management System Model Updates and Quality Assurance is one of a series of manuals within the Transmission set. This manual focuses on specific process and procedures for the updating and verifying the PJM EMS model.

This manual focuses on PJM and PJM Member pre-scheduling activities that set the stage for the scheduling and dispatching phases of the PJM RTO operation.

The PJM Manual for Energy & Ancillary Services Market Operations is one of a series of manuals within the PJM Energy Market Manuals. This manual focuses on the Day-ahead and Real-time scheduling activities that are performed by the PJM staff and the PJM Members. The manual describes the rules and procedures that are followed to schedule resources.

This manual focuses on the activities that occur in the real-time operation of the PJM Energy Market. The manual describes how PJM dispatches and controls Capacity Resources, and how PJM monitors transmission facilities. It also describes how PJM provides Ancillary Services.

The PJM Region Transmission Planning Process Manual is one of the PJM manuals in the PJM Regional Transmission Expansion group. This manual focuses on the process for planning baseline expansion facilities under the PJM Region Transmission Planning Process. Capitalized terms not defined as they are used have the meaning defined in the PJM’s Open Access Transmission Tariff (OATT) and in the Operating Agreement (OA.)

This manual focuses on the markets and operations requirements for generating entities to connect to the PJM system and their responsibilities as signatories to the Operating Agreement of PJM Interconnection, L.L.C.

The concept of synchro-waveforms has recently emerged as a promising frontier in power system monitoring and data-driven applications. By providing access to raw waveform samples, synchro-waveforms can capture not only the typical major disturbances but also the seemingly minor, yet sometimes highly informative, disturbances in voltage and current that are missed by other time-synchronized measurements, such as synchrophasors. As a result, synchro-waveforms can support a wide range of existing and new measurement-based applications in power system monitoring, control, and protection. However, several open issues remain in this field. The true value of synchro-waveforms has yet to be fully realized. At the same time, their much higher data volume and faster reporting rate compared to synchrophasors introduce new challenges in power system data analytics that must be addressed. This technical report identifies and addresses some of these challenges through a collaborative effort. It explores currently available technologies and case studies in this rapidly evolving area, while also examining future needs in data handling, standardization, and real-time processing capabilities. Specifically, the chapters in this report cover the following core subjects: synchro-waveform technology and infrastructure; data collection, storage, and communication; different forms of synchro-waveform data representation; basic methods for working with synchro-waveform data; case studies and future applications; and synchro-waveform standardization needs. This report was prepared with contributions from a diverse group of individuals with varying expertise. While some sections reflect on well-understood concepts, many sections seek to explore preliminary ideas. Together, these contributions provide valuable insights and suggestions for future directions in this field. This report serves as a resource for industry, academia, and all stakeholders interested in leveraging synchro-waveform data for enhanced situational awareness and other power system applications. Its ultimate goal is to raise awareness within the power systems community and related disciplines about the growing field of synchro-waveforms and the diverse range of emerging topics in this domain.

A key issue in creating the next generation of energy management system (EMS) and advanced distribution management system (ADMS) platforms will be the ability to represent and exchange power system network model data in a consistent manner. To this end, the Common Information Model (CIM) stands out as the only standardized vocabulary (or ontology) for defining power system network models and asset data in a comprehensive, consistent manner across the generation-transmission-distribution boundary. The CIM is freely available to use and extend. The CIM is maintained by the UCAiug (informally known as the CIM User’s Group) under an Apache 2.0 license. The CIM Users Group collaborates with the IEC and other standards communities for the development of technical and informative specifications. Although portions of the information model are referred to by the corresponding IEC standards naming, it is not necessary to purchase any of the IEC standards to use the CIM information model. This document provides a roadmap for power system engineers and application developers not familiar with semantic modeling to start using the CIM for modeling, simulation, optimization, and development of advanced power applications. The key classes needed for defining power system topology and equipment are explained systematically. Key focus areas include modeling of lines, transformers, generators, switching equipment, loads, and distributed energy resources (DERs).

Over the past decade, there has been a global growth in datacenter capacity, power consumption and the associated costs. Accurate mapping of datacenter resource usage (CPU, RAM, etc.) and hardware configurations (servers, accelerators, etc.) to its power consumption is necessary for efficient long-term infrastructure planning and real-time compute load management. This paper presents two types of statistical power models that relate CPU usage of Google’s Power Distribution Units (PDUs, commonly referred to as power domains) to their power consumption. The models are deployed in production and are used for cost- and carbon-aware load management, power provisioning and infrastructure rightsizing. They are simple, interpretable and exhibit uniformly high prediction accuracy in modeling power domains with large diversity of hardware configurations and workload types across Google fleet. A multi-year validation of the deployed models demonstrate that they can predict power with less than 5% Mean Absolute Percent Error (MAPE) for more than 95% diverse PDUs across Google fleet. This performance matches the best reported accuracies coming from studies that focus on specific workload types, hardware platforms and, typically, more complex statistical models.

This document provides a high-level mathematical formulation and explanation of the objective function used in the clearing of the Energy and Ancillary Service Markets. The intent of this document is to provide a better understanding of the mechanics.

Data centers have become a widespread power electronics (PE) load, which has significant impact on the power grid. In order to investigate the data center load characteristics, this article proposes a complete dynamic model for a typical data center ac power distribution system. A generalized model with mode transition is proposed to coordinate different power stages in the data center power system. Meanwhile, to help evaluate the grid dynamic performance and transient stability, an all-in-one load data center power emulator is developed on a reconfigurable PE converter-based hardware testbed (HTB). The dynamic power model is digitized and simplified to be implemented in two local voltage source inverters on the HTB. This proposed data center power emulator has been verified experimentally in a regional network. Dynamic performances during voltage sag events and server load variations are emulated and discussed. The article details the design, development, and verification of the data center model and power emulator. The proposed model and emulator provide an effective, easy-to-use tool to better design data centers and study the interaction with the power system.

Initiated in 2020 by transmission owner PPL Electric Utilities and facilitated by PJM, PPL Electric Utilities has said it expects the activation of dynamic line rating (DLR) technology to expand capacity and promote market efficiency on three historically congested lines. PPL Electric Utilities estimates that this DLR project can save customers $23 million annually in congestion costs.

A digital twin is a virtual representation of an object or system designed to accurately reflect a physical object.

The NERC Resources Subcommittee (RS) drafted this reference document at the request of the NERC Operating Committee as part of a series on operating and planning reliability concepts. The document covers balancing and frequency control concepts, issues, and recommendations. Send questions and suggestions for changes and additions to balancing@nerc.com.

Since the publication of the original paper on power system stability definitions in 2004, the dynamic behavior of power systems has gradually changed due to the increasing penetration of converter interfaced generation technologies, loads, and transmission devices. In recognition of this change, a Task Force was established in 2016 to re-examine and extend, where appropriate, the classic definitions and classifications of the basic stability terms to incorporate the effects of fast-response power electronic devices. This paper based on an IEEE PES report summarizes the major results of the work of the Task Force and presents extended definitions and classification of power system stability.

It is in the public interest for NERC to develop guidelines that are useful for maintaining and enhancing the reliability of the Bulk Electric System (BES). The subgroups of the Reliability and Security Technical Committee (RSTC)—in accordance with the RSTC charter1 are authorized by the NERC Board of Trustees to develop reliability and security guidelines. These guidelines establish a voluntary code of practice on a particular topic for consideration and use by BES users, owners, and operators. These guidelines are coordinated by the technical committees and include the collective experience, expertise, and judgment of the industry. The objective of this reliability guideline is to distribute key practices and information on specific issues critical to appropriately maintaining BES reliability. Reliability guidelines are not to be used to provide binding norms or create parameters by which compliance to NERC Reliability Standards are monitored or enforced. While the incorporation, of guideline practices, is strictly voluntary, reviewing, revising, or developing a program using these practices is highly encouraged to promote and achieve appropriate BES reliability

Common Information Model Primer helps readers understand how the Common Information Model (CIM) is used at electric utilities. The primer explains how the CIM originated and was developed through the years, with the support of working groups of Technical Committee 57 of the International Electrotechnical Commission. The basics of Unified Modeling Language are explained for readers new to the language of the CIM. Building from examples of commonly understood objects, the concepts underlying the CIM are introduced in a step-by-step fashion. This conceptual understanding prepares the reader for an introduction to the complexities of electric power system modelling and data exchange approaches. The seventh addition expands upon Section 8, going into detail about other tools for generating schema from the CIM UML and addressing updates to these tools that have added support for JSON Schema generation. Learning aids include questions and answers to reinforce learning of key CIM concepts, as well as case studies illustrating how utilities and vendors leverage the CIM for business benefit.

The notion of uncertainty is of major importance in machine learning and constitutes a key element of machine learning methodology. In line with the statistical tradition, uncertainty has long been perceived as almost synonymous with standard probability and probabilistic predictions. Yet, due to the steadily increasing relevance of machine learning for practical applications and related issues such as safety requirements, new problems and challenges have recently been identified by machine learning scholars, and these problems may call for new methodological developments. In particular, this includes the importance of distinguishing between (at least) two different types of uncertainty, often referred to as aleatoric and epistemic. In this paper, we provide an introduction to the topic of uncertainty in machine learning as well as an overview of attempts so far at handling uncertainty in general and formalizing this distinction in particular.

This report recounts the factors contributing to disruptions in electricity and natural gas service in Texas during Winter Storm Uri, with a particular focus on blackouts on the Electric Reliability Council of Texas (ERCOT) grid during the period from February 15-18, 2021. Our goal is to create a common basis of fact to educate the debate over strategies to avoid similar problems in the future. We specifically limited the scope of this report to the events during February 2021, a comparison of the February 2021 event to the previous energy system disruptions in 1989 and 2011 during winter storms, and the economic consequences of the event in February 2021. An appendix describes the long-term evolution of the ERCOT electricity market and provides historical context. This report is not intended to comprehensively address all issues stemming from such a complex event, but may inform subsequent assessments. This report does not recommend policies or solutions.

Energy management system application program interface (EMS-API) - Part 600-1: Common Grid Model Exchange Standard (CGMES) - Structure and rules

The Division of Energy Market Assessments, in the Office of Energy Policy and Innovation, serves the public by overseeing the nation’s natural gas and electric power markets and related energy and financial markets. Market Assessments conducts daily assessments of these markets and reports its findings and recommendations to the Commission and the public. This site presents information for the public on natural gas and electric market conditions relevant to the Commission and identifies emerging trends in those markets. The content will be updated and additional information will be added as it becomes available. FERC provides market assessments of interstate electricity and natural gas markets and publishes analyses and reports including the Winter Energy Market Assessment, the Summer Market and Reliability Assessment, the State of the Markets Report, and the Energy Primer.

The resilience of the electric grid is the foundational building block for our decarbonized clean energy future. While the concept of resiliency is not new, its application to the electric grid is not as straightforward due to the lack of a consistent definition of resilience or a mature set of metrics by which resilience or its application can be measured. This report provides an overview of resilience definitions, including its relationship with reliability, the existing frameworks for holistically defining resilience planning and implementation process, and the metrics to evaluate and benchmark resilience. It provides recommendations on how to use those frameworks and metrics and evaluates technologies, tools, and methods to improve electrical system resilience. To provide a practical perspective to addressing resilience, the report includes the progress made by electric grid operators in collaboration with regional authorities to strengthen the resilience posturing, including some of the more common practices and use cases to increase system resilience, enhance broader preparedness, and to combat the impacts of the various external impacts to the electric power grid. Those use cases include Southern California Edison, Con Edison, Entergy, Florida utilities, San Diego Gas & Electric, ComEd, Austin Energy, as well as transmission and distribution system hardening practices, wild-fire risk mitigation lessons learned from California, and NERC reliability and cyber-security standards.

A task force set up jointly by IEEE Power System Dynamic Performance Committee (PSDPC) and CIGRE had addressed the issue of stability definition and classification in power systems from a fundamental viewpoint and had closely examined the practical ramifications. The relevant report published in 2004, primarily dealt with fairly slow, electromechanical phenomena, typically present in power systems dominated by synchronous machines and their controls. Since that time, the dynamic behavior of power systems has gradually changed due to the increasing penetration of converter interfaced generation technologies, loads, and transmission devices and has progressively become more dependent on (complex) fast-response power electronic devices, thus arising new stability concerns. In recognition of this change, a Task Force was established by IEEE PSDPC in 2016 to re-examine and extend, where appropriate, the classic definitions and classifications of the basic stability terms. This report summarizes the results of this work and presents extended definitions, characterization and classification of power system stability.

Digital Twin technology is an emerging concept that has become the centre of attention for industry and, in more recent years, academia. The advancements in industry 4.0 concepts have facilitated its growth, particularly in the manufacturing industry. The Digital Twin is defined extensively but is best described as the effortless integration of data between a physical and virtual machine in either direction. The challenges, applications, and enabling technologies for Artificial Intelligence, Internet of Things (IoT) and Digital Twins are presented. A review of publications relating to Digital Twins is performed, producing a categorical review of recent papers. The review has categorised them by research areas: manufacturing, healthcare and smart cities, discussing a range of papers that reflect these areas and the current state of research. The paper provides an assessment of the enabling technologies, challenges and open research for Digital Twins.

The purpose of this document is to provide the contextual and assembly UML models and the schema of the CRAC_MarketDocument. The schema of the CRAC_MarketDocument could be used in various business processes. It is not the purpose of this document to describe all the use cases, sequence diagrams, business processes, etc. for which this schema is to be used.

The objective of this implementation guide is to make it possible for software vendors to develop an IT application for TSO and RSC to exchange information relative to contingency list, remedial actions and additional constraints used for coordinated capacity calculation process. The implementation guide is one of the building blocks for using UML (Unified Modelling Language) based techniques in defining processes and messages for interchange between actors in the electrical industry in Europe.

In August 2017, the Department of Energy (DOE) issued a Staff Report to the Secretary on Electricity Markets and Reliability (DOE Grid Report) regarding reliability and resilience in light of the changing energy environment. One recommendation in the DOE Grid Report stated that NERC should consider adding resilience to its mission and broadening its scope to address resilience. In response to the DOE report and NERC assessments, the NERC Board of Trustees (NERC Board) directed the Reliability Issues Steering Committee (RISC) to develop a framework for resilience and examine resilience in today’s environment. At the November 2017 NERC Board Meeting, Board Chair, Mr. Roy Thilly commented that, “Resilience is already built into what NERC does, and NERC is not looking to expand scope but rather to examine resilience more closely. The NERC Board requested that the RISC report back with a framework on how to think about resiliency in the context of reliability.” In accordance with the NERC Board’s directive, the RISC has worked with NERC stakeholders to reexamine the meaning of resilience in today’s changing environment and how resilience impacts NERC activities. Meanwhile, the DOE and Federal Energy Regulatory Commission (FERC) have continued evaluating the relationship of resilience and reliability. This report summarizes the results of the RISC’s examination of resilience, including the RISC Resilience Framework. Since its inception and consistent with section 215 of the FPA, NERC has focused on the grid’s ability to withstand and manage event impacts, and respond to emerging issues and risks to ensure the Reliable Operation of the BPS. Resilience is a performance characteristic of the Reliable Operation of the BPS and a critical part of ERO Enterprise activities. Per its statutory mission, NERC has an essential leadership role in identifying and mitigating evolving and emerging risks to reliability. Further, as a learning industry, NERC supports sharing of lessons learned and monitors system performance to identify evolving and emerging risks. Through its subject authority over Bulk Electric System (BES) reliability and its reliability programs, NERC can identify and share ways industry can increase resiliency of the BES to resist anticipated threats. In particular, NERC must develop and enforce Reliability Standards for Reliable Operation on the BES of the BPS and conduct periodic assessments of the reliability and adequacy of the BPS in North America. For more than 50 years, “reliability” for the BPS has been defined to consist of two fundamental and aspirational concepts: adequacy and operating reliability.

This standard provides interconnection and interoperability technical and test specifications and requirements for distributed energy resources (DERs). Additionally, several annexes are included in this standard that provide additional material for informative purposes, but are not required to be used in conjunction with this standard.

The 2012 Probabilistic Assessment Report (2012 ProbA) is designed to complement the 2012 LTRA by providing additional probabilistic statistics of EUE and LOLH. This assessment includes the results of each assessment area’s third and fifth year forecasts (i.e., 2014 and 2016 results) from the 2012 LTRA. The assessment areas represented are shown in Figure 1. For the most part, the same base case was used for both the 2012 LTRA and the 2012 ProbA model runs; however, for some assessment areas, different base case data may have been used due to the vintage of the data available or other analytical restrictions. NERC’s ProbA is a compilation of 11 separate assessments conducted by five Regional Entities (REs) and six individual assessment areas, covering the total 26 assessment areas. These studies varied in scope from the whole of WECC to individual PCs (e.g., MISO, PJM, and SaskPower). These individual assessments were then combined into NERC’s ProbA for the whole NERC footprint. A July 2012 conference call and a following formal letter in August that requested supporting information and data initiated the 2012 ProbA. To minimize the burden on industry, the assessment was designed to coincide with the finalization of the data for the 2012 LTRA. The analysis was conducted over the next six months with initial individual drafts due in December 2012 and final reports in February 2013. The final comprehensive NERC report combining these assessments will be presented for the approval of the NERC Planning Committee at its June 2013 meeting. Last year NERC conducted the Pilot Probabilistic Assessment 2011, 3 which was based on 2010 LTRA data; this initial effort was approved by the NERC Planning Committee in June 2012. Only FRCC, the NPCC Assessment Areas, the SERC Assessment Areas, Manitoba, MISO, and PJM were capable of conducting such studies as part of the pilot report. NERC compared the results of the pilot report and the 2012 ProbA for the areas in both studies. With the approval of the pilot report, the Planning Committee concluded that the probabilistic assessment complemented and enhanced the efforts of the Reliability Assessment Subcommittee (RAS) and should be a biennial report with the participation of all assessment areas across the whole NERC footprint. This is the first such report in the series of probabilistic assessments covering all of the NERC Assessment Areas.

Evaluating the impact of unplanned outages is a key aspect of real-time operations at PJM. Contingency evaluation impacts the decisions of the various application users. Transmission Dispatchers, Generation Dispatchers and Operations Planners evaluate contingencies that affect their decisions regarding transmission system reliability and markets. This paper presents various aspects of the contingency usage at PJM including the applications that utilize contingency lists, modeling of contingencies and monitoring of contingency results.

This standard defines a common format for the data files needed for the exchange of various types of power network events in order to facilitate event data integration and analysis from multiple data sources and from different vendor devices. The flexibility provided by digital devices in recording network fault event data in the electric utility industry has generated the need for a standard format for the exchange of data. These data are being used with various devices to enhance and automate the analysis, testing, evaluation, and simulation of power systems and related protection schemes during fault and disturbance conditions. Since each source of data may use a different proprietary format, a common data format is necessary to facilitate the exchange of such data between applications. This will facilitate the use of proprietary data in diverse applications and allow users of one proprietary system to use digital data from other systems.

The problem of defining and classifying power system stability has been addressed by several previous CIGRE and IEEE Task Force reports. These earlier efforts, however, do not completely reflect current industry needs, experiences and understanding. In particular, the definitions are not precise and the classifications do not encompass all practical instability scenarios. This report developed by a Task Force, set up jointly by the CIGRE Study Committee 38 and the IEEE Power System Dynamic Performance Committee, addresses the issue of stability definition and classification in power systems from a fundamental viewpoint and closely examines the practical ramifications. The report aims to define power system stability more precisely, provide a systematic basis for its classification, and discuss linkages to related issues such as power system reliability and security.

This paper studies the recovery of the voltage after a voltage dip due to a fault in a three-phase system. The instant of voltage recovery corresponds to the instant of fault clearing. For single-phase and phase-to-phase faults, a single point-on-wave of voltage recovery can be defined. For two-phase-to-ground and three-phase faults, the recovery takes place in two or three steps. The voltage recovery is described in a systematic way by using a classification of three-phase unbalanced voltage dips. The voltage recovery needs to be modeled correctly for studies of equipment immunity against voltage dips.

Reaffirmed 2005. A common format for data files and exchange medium used for the interchange of various types of fault, test, or simulation data for electrical power systems is defined. Sources of transient data are described, and the case of diskettes as an exchange medium is recommended. Issues of sampling rates, filters, and sample rate conversions for transient data being exchanged are discussed. Files for data exchange are specified, as is the organization of the data. A sample file is given.

This book is concerned with understanding, modelling, analyzing, and mitigating power system stability and control problems. Such problems constitute very important considerations ni the planning, design, and operation of modern power systems. The complexity of power systems is continually increasing because of the growth in interconnections and use of new technologies. At the same time, financial and regulatory constraints have forced utilities to operate the systems nearly at stability limits. These two factors have created new types of stability problems. Greater reliance is, therefore, being placed on the use of special control aids to enhance system security, facilitate economic design, and provide greater flexibility of system operation. In addition, advances in computer technology, numerical analysis, control theory, and equipment modelling have contributed to the development of improved analytical tools and better system-design procedures. The primary motivation for writing this book has been to describe these new developments and to provide a comprehensive treatment of the subject.

A method for online transient stability assessment of large power systems is proposed. It consists of: replacing the multimachine system by a two-machine dynamic equivalent, further amenable to a one-machine-infinite-bus system; reducing the stability problem to a sole algebraic equation, devised from the equal area criterion, or equivalently from the Lyapunov direct criterion; and using this equation to derive one-shot stability analysis strategies. A technique for system admittance matrix reduction is developed that proves efficient, especially for large systems and multiple-contingency evaluation. The method’s main appeal is rapidity: it is about one order of magnitude faster than the most efficient direct criterion. Other attractive features are flexibility and ability to encompass various simulation conditions. Extensions to online sensitivity analysis and control are suggested.

This paper presents proposed terms, definitions and symbols in pursuit of Electric Utility Industry uniformity and common understanding in the analysis of subsynchronous resonance. For the purpose of this paper the discussion is limited to series compensated transmission systems. These definitions are recommended, where applicable, in other unique areas encompassing subsynchronous oscillations. The work presented is a product of the Subsynchronous Resonance Working Group as part of the activity of the IEEE System Dynamic Performance Subcommittee.

This paper presents a Common Format for the exchange of solved load flow cases. This format is presently being used throughout most of the eastern and north central United States and parts of Canada. By publishing through the national organization, it is intended that a common reference be established and maintained for those who wish to use the format. The paper presents a detailed description of the format as well as procedures for making revisions and additions.

A method of dynamic aggregation is introduced to define power system transient stability indices based on the previously used concepts of potential and kinetic energies. The indices are easier to compute and less conservative than those introduced by other authors. They reflect quantitatively the seriousness of the system instability threat created by actual or postulated faults. They are thus useful for purposes of on-line system security monitoring and interpretation of transient stability studies.

A method is presented for analyzing the results of stability calculations using generator transfer admittances to calculate power flows between generators. It is shown that the equations for power flow from any generator to all other generators can be used to define an equivalent system bus unique to that generator. Functions which indicate the capability of a generator to maintain synchronism are presented with illustrations of their application.

A new measure of the relative transient stability of a multimachine power system based on the Lyapunov stability theory is introduced. Techniques of sensitivity analysis are used to determine numerically the influence of variations or errors in the estimation of the system parameters on the transient stability of a power system. In particular, data is presented for an application of these ideas to a one machine infinite bus system.

The transient tability of the general 2-machine system is considered in this paper. Introduction of an equivalent system with concentrated inertia at one end is shown to facilitate the direct application of the equal area method of analysis to the general 2-machine system. Heretofore the equal area method has been confined to certain special 2-machine systems.