This paper introduces the concept of using terrestrial private communications networks for the distribution of high-accuracy time and provides methods for mitigating specific GPS vulnerabilities.
This paper describes a three-terminal line differential protection project designed for a rail company as part of a refurbishment project. The paper explains each of the different technologies used for this project, including line differential over Ethernet, coarse wave division multiplexers, and managed switch configuration. It also provides details of the performance of the system in terms of speed and stability.
This paper presents actionable information regarding the critical requirements of a fully trusted industrial control system network. It examines the strengths and weaknesses of existing solutions for implementing trust management.
This paper demonstrates intelligent electronic device (IED) resiliency to high-altitude electromagnetic pulse (HEMP) events through analysis and test results. It presents substation grounding and wiring practices that are HEMP resilient and also highlights available HEMP standards as they relate to IEDs and substation control houses. This information will help utilities prevent unnecessary mitigation efforts and address the concerns regarding the effects of HEMP on substations and substation IEDs.
Southern California Edison is protecting a new 500 kV mutually coupled transmission line incorporating both overhead and underground sections. This paper discusses the protection challenges faced with this type of arrangement and describes using real-time digital simulation to evaluate the performance of the protection system.
This paper outlines the benefits of using digital communications between primary substation equipment and the protective relays installed in the control house. The authors discuss two methods used to implement a process bus—a switched network and a point-to-point network—and then introduce a new point-to-point, EtherCAT-based digital substation technology that is robust, simple to use, and secure.
This paper describes the components of a wireless protection sensor system, its integration with protection devices, and how the fault information can be transmitted from the sensors to such devices at protection speeds. Additionally, this paper discusses how protection devices use this low-latency fault information to securely speed up the operation speed of and improve the selectivity of distribution protection schemes.
This paper discusses the functionality and merits of the high-speed distribution protection implemented for the City of College Station's multiple distribution substations using communications-assisted special protection and control schemes. These schemes were implemented to improve the reliability, selectivity, and availability of the power system.
This paper describes an event in which a negative-sequence overcurrent (51Q) element operated for a fault on an adjacent feeder, discusses the impact of voltage unbalance on induction motors, and shares lessons learned to assist engineers to securely set 51Q elements.
This paper provides procedures and guidelines for successfully designing and integrating IEC 61850 GOOSE protection schemes while keeping the feasibility of initial commissioning and future expansion and testing in mind.
This paper discusses motoring events and the resulting active and reactive power flows, examines existing reverse power relays used for generator protection, and presents a new algorithm for dependable motoring detection. It also reviews current transformer and voltage transformer accuracy as defined by ANSI IEEE C57.13 and IEC 61869.
This paper provides an analysis of the Ukraine cyber-induced power outage on December 23, 2015 and provides mitigation methods and recommendations that would have protected the Ukraine control system.
This paper outlines the three distinct advantages that software-defined networking (SDN) brings to Ethernet-based control systems: dramatically improved packet delivery performance under both normal and fault event conditions, greater cybersecurity without added complexity, and centralized situational awareness with disruptionless change control, enabling seamless scalability.
This paper details a system developed with American Electric Power for monitoring and automatically diagnosing the health of circuit breakers. It presents an overview of real-time data parameters recorded to provide important health diagnostic information that provides insight into the remaining expected life of the breaker. The system uses this information to reduce operations and maintenance costs by eliminating regularly scheduled manual tests and shifting to as-needed maintenance rather than regularly scheduled maintenance.
This paper compares the intrinsic performance of conventional mho elements and incremental quantity-based distance elements, irrespective of the ways they are implemented. Specifically, it explains that incremental distance elements have superior performance, but they have to be supplemented by conventional mho elements because the incremental elements are only available for a short time.
This paper describes the design of a system that combines event files stored in protective relays and synchrophasor data streamed from phasor measurement units (PMUs) for wide-area system analysis.
This paper describes the design, construction, and commissioning of the microgrid controls for the Duke Energy McAlpine Creek microgrid project and the lessons learned from its implementation.
In this paper, we use high-resolution event data to discuss switching surges caused by high-speed reclosing on high-voltage lines and their impact on bus differential relays.
This paper presents simple rules for the correct selection of transformer differential relay compensation settings and their application to real-world installations.
This paper introduces new ideas and concepts that complement existing generator protection elements to provide better overall generator protection and monitoring.
This paper describes the analysis and resulting investigation that occurred when a CT secondary wire made contact with a transformer bushing, causing an outage at a 138 kV substation.
This paper describes the practical implementation details and operational experience of a new oscillation detection system initially operated at San Diego Gas & Electric. Several examples are provided of successful detection and analysis of events using this system.
This paper addresses the use of IEC 61850 network engineering and testing guidelines for performing network acceptance testing and for troubleshooting in-service Ethernet networks. The paper also explains best practices to configure systems to constantly perform self-tests and monitor and record performance statistics.
This paper describes the authors’ experience in designing, installing, and testing microgrid control systems.
This paper describes the logic design, communications infrastructure, and real-time testing of a remedial action scheme implemented in southern Peru.
This paper reviews a number of typical settings found in incremental quantity- and traveling-wave-based protection elements and provides setting guidelines and examples for various applications, including series-compensated lines and lines with tapped loads.
This paper provides insights into how mutual coupling affects ground distance, ground overcurrent, and directional elements in different system configurations; offers practical advice for identifying situations where mutual coupling must be considered; and provides step-by-step guidance for setting ground distance and directional overcurrent elements on transmission lines that are affected by mutual coupling.
This paper examines the dynamic mho expansion for positive-sequence memory polarization during a variety of different faults and changing system conditions.
This paper focuses on defining and measuring the performance of ultra-high-speed line protective relays, including traveling-wave protection elements.
This paper discusses relay testing concepts, using a line distance relay element as an example.
This paper describes a defense-in-depth scheme that applies specifically to the industrial control system realm, with implementation details and an example system.
This paper provides a clear set of procedures and equations to follow in optimal current transformer selection for low-voltage motor control centers.
This paper summarizes the successful addition of a remedial action scheme to an in-service emergency control system in the country of Georgia.
This paper explains a novel data acquisition method that supports accurate, synchronized, wide-area power flow summation at fixed millisecond intervals.
This paper discusses how to use event data (voltages, currents, and fault location) from relays at two ends of a transmission line to calculate positive-, negative-, and zero-sequence line impedances. Impedances calculated from real event data can be used to validate relay settings and short-circuit models.
In this paper, we briefly discuss the types of underground cables, their bonding and grounding methods, and the fundamental differences between overhead transmission lines and cable electrical characteristics. Finally, we discuss the application of short-circuit protection for high-voltage ac cables.
This paper proposes a new principle for generator turn-to-turn fault protection based on the ampere-turn balance between the stator negative-sequence current and the double-frequency component of the field current. The paper describes two protection elements using this principle: a stator-rotor current unbalance element that uses the current magnitudes and a stator-rotor current differential element that uses the current phasors. The paper derives the new methods, discusses their dependability, sensitivity, and security, and illustrates their operation with computer simulations and test results from a physical made-to-scale generator.
This paper discusses key elements of creating a reliable motor protection system, including thermal modeling, the detection of broken rotor bars, and arc-flash detection.
This paper provides eight basic guidelines to improve cybersecurity for industrial control systems.
This paper analyzes the voltage sags that occurred during a simulated transformer energization study for an offshore platform.
This paper describes the impacts of photovoltaic (PV) installations on power systems and discusses different mitigation methods to address them. The paper proposes a solution to minimize the impacts by using the concept of coordinated control between the substation and the PV generation plant.
This paper describes the implementation of a power management system for a mature oil field facility and how the system was optimized to use utility generation, its own generation, or both combined for the reliability, stability, and scalability of the facility power system.
This paper demonstrates that errors will exist with a conventional single- or double-ended fault location calculation if the fault occurs during a pole-open condition. Compensated algorithms are presented that achieve accurate fault location under these conditions.
This paper describes common failure modes for substation clocks and their recovery mechanisms. It also describes test setups with pass/fail criteria to characterize substation-hardened clocks under conditions of electrical and environmental stress.
This paper proposes a modular microgrid unit (MMGU) that can work autonomously but is also capable of connecting to other MMGUs to form an expandable microgrid.
This paper presents common challenges in distribution protection and demonstrates solutions using the multiple protection elements and custom logic available in modern distribution feeder relays and recloser controls. Solutions are provided to prevent false trips due to inrush, improve protection response times, mitigate conductor slap issues, and improve the performance of noncommunicating loop schemes.
In this paper, a real-world event and simulations are used to study the impact of dc winding resistance testing on the magnetizing current of a transformer. Solutions are provided to mitigate possible unintended operations.
This paper describes a new falling conductor detection scheme that trips the affected circuit section in the narrow time window between the moment of the break and the time the conductor hits the ground. The affected circuit section is de-energized while the conductor is still falling, eliminating the risk of an arcing ground fault or energized circuits on the ground.
This paper discusses the design and implementation of a distribution automation system developed to detect electric faults using fault indicators and automatically reconfigure the distribution system topology to isolate faulted sections and restore service to the de-energized loads.
This paper discusses protection system designs for three single-phase-and-spare transformer banks. Ways to improve sensitivity and make it possible to precisely indicate the fault location in the bank are illustrated with examples. The paper also discusses how to design the system to easily reconfigure the differential zones for any spare substitution configuration.
This paper is an introduction to the deployment of a network intrusion detection system for industrial control systems.
Two drastically different types of differential relays, one with a single set of very high-impedance inputs and another with multiple sets of low-impedance inputs, are available for bus differential protection. This paper discusses for each type of relay the concepts used, the pros and cons, and the importance that current transformer selection plays in applications.
This paper discusses improving the security and dependability of line current differential protection schemes on series-compensated transmission lines prone to current inversion.
This paper describes the protection challenges and solutions associated with the Penonomé wind power plant in Panama. The paper discusses protection coordination requirements and results, provides recommendations for future enhancements of the protection system, and concludes with a description of an actual event involving two cross-country faults in a 34.5 kV system.
This paper explains modern nanosecond precision time technologies and new applications they enable.
This paper describes and evaluates several commonly applied line protection schemes using analysis tools like fault trees, power system studies, and event analysis. The paper compares the protection schemes in terms of speed, sensitivity, security, dependability, and selectivity.
This paper analyzes and explains why the compensator phase distance elements operated for a utility that experienced a phase cross-connect condition when personnel inadvertently crossed two phases during line switch installation. This paper also discusses the theory of operation of compensator phase distance relays and methods for making elements secure in similar phase cross-connect conditions.
This paper describes the effect geomagnetically induced currents have on CTs and the resulting impact on protection security and dependability. The paper supports its claims with simulated as well as experimental results.
This paper discusses the installation and commissioning of a generator rotor angle and field quantities measurement system at a 740 MVA combined cycle plant. The paper discusses the lessons learned and possible applications using these measurements.
This paper describes the communications requirements for various protection and control applications, and it discusses the advantages and disadvantages of communications technologies. The paper also describes how network topologies can improve security and dependability, and it discusses cybersecurity practices that are suitable for securing protection communications links.
This paper details the threats that SCADA and industrial control systems face, how to detect and counter those threats, and how to apply countermeasures, new technologies, and safe practices to these systems.
This paper describes the post-fault analysis following a three-phase intercircuit fault on parallel 138 kV transmission lines. Fault study data associated with single fault conditions on each line are compared with time-synchronized disturbance data from protective relays.
This paper provides an overview of winding insulation failure modes related to ground faults and discusses all common ground fault protection schemes in detail. The paper contrasts the following aspects of these schemes: sensitivity, speed, security, availability, complexity, and setting considerations.
This paper provides explanation and comparison of methods of fault identification, isolation, and recovery of data paths in Ethernet networks for high-speed automation and protection applications. SDN is introduced as a new and improved Ethernet transport technology for mission-critical applications.
This paper shares details about three challenging case studies and their root causes.
This paper compares the results of using two different wireless technologies, serial radios and cellular modems, to simultaneously stream synchrophasor data from four different locations along a rural feeder to a photovoltaic generation site.
This paper discusses Phase 2 of the ongoing distribution automation pilot project by Central Lincoln People's Utility District, focusing on the fault indicators used in the project and highlighting lessons learned.
This paper describes the new high-speed data acquisition and precise synchronization strategies used for the design of the communications network required for an HVDC link between Spain and France. Various contingency scenarios to improve the availability and reliability of the system are discussed along with several new hardware and software redundancy methods to improve the overall control system dependability and security.
A centralized series of dual triple modular redundant special protection systems have been implemented in Taiwan. This paper covers their design, testing, and implementation.
This paper describes a new directional power algorithm in the form of an adaptive characteristic that provides a dependability bias to ensure tripping during an inadvertent motoring event.
This paper illustrates the methods and benefits of supervising the timely and accurate receipt of GOOSE messages and calculating a binary logic representation of the success of digital message exchange of protection signals. This status, referred to as message quality, is used as a qualifier in communications-assisted protection and automation logic to adapt the logic immediately after communications fail.
This paper analyzes the performance of CTs under the presence of geomagnetically induced currents (GICs). The paper proposes a simple CT model to analyze the GIC problem and applies it, as well as laboratory tests on a physical CT, to explain and quantify the impact of GICs on CTs. We conclude that the impact to protective relays is minimal.
This paper describes new special-purpose test devices and procedures to verify Ethernet network configuration and performance. The results of research using these test procedures are explained, which reveal new network topology recommendations and associated configuration recommendations for protection signal messages, such as multicast GOOSE messages.
This paper describes the shortcomings of PRP and HSR and how to create Ethernet redundancy and duplication via software-defined networking (SDN). Examples illustrate how SDN methods create lossless signal delivery (with the use of Ethernet packets) and address issues of teleprotection, interlocking, and automation applications based on IEC 61850 GOOSE messaging.
This paper provides guidance to transmission system operators and protection and control engineers on how to overcome the technical limitations imposed by traditional technology for synchronizing islanded microgrids with advanced technology.
This paper presents a country-wide remedial action scheme (RAS) implemented in Usinas y Trasmisiones Eléctricas (UTE) in Uruguay. The RAS consists of six different schemes operating independently and, in certain cases, simultaneously to calculate power system states and take the remedial actions.
This paper analyzes event reports that indicated an arcing ground on the neutral end of a large generator. It investigates the limitations of ground protection techniques as well as techniques to overcome these limitations when detecting an arcing ground fault.
This paper compares the mechanisms for quickly reconfiguring Ethernet networks to satisfy mission-critical performance metrics while providing simultaneous duplicate or redundant signal exchange. The paper also describes the redundancy and duplication methods that are available in software-defined networking.
This paper addresses the use of IEC 61850 network engineering and testing guidelines for troubleshooting Ethernet networks. The paper shares practical examples of detecting problems, finding root cause, and correcting communications problems in operational systems in South Africa, Asia, and Europe.
This paper describes the protective relaying scheme used in the harmonic filters of a bipolar 600 kV installation, associated with a 2,400-kilometer dc transmission line in Brazil.
This paper explains why new design possibilities provided by modern IEDs make it difficult to describe protection and control system functionality using traditional schematic diagrams. The paper describes one utility's experience as they worked to modernize their logic and documentation, and it discusses the new guidelines they developed and adopted for logic diagram creation.
This paper is a case study describing the implementation and testing of an advanced automatic synchronising system for a complex and flexible 330 kV bus arrangement used for connecting two hydroelectric generating stations to the transmission grid.
This paper presents the advanced solutions implemented for the protection of a crucial metropolitan distribution network that consists of several parallel circuits between a single-source substation and two load-serving substations.
This paper describes a point-on-wave model development and simulation study that supports a broader investigation of the effect of air conditioning and similar loads on the recovery of electric utility voltage after faults.
This paper summarizes present protection recommendations and their limitations for the three most common types of PSTs. The paper then reports on the further development of a differential element that has been in successful use for many years, is sensitive to all fault types (including turn-to-turn faults), and can be applied to any type of PST using only CTs on the source and load sides of the PST zone.
This paper illustrates the benefit of measuring I0p (the parallel line zero-sequence current) for fault location.
This paper identifies how accurately loads must be modeled, specifically for frequency stability studies. It also provides a simple reference that engineers can use to specify the level of detail required when load modeling industrial power systems.
This paper shares the methods used to find root cause and solve a governor-induced frequency instability problem.
This paper discusses a fully redundant power management system for a major oil field in Saudi Arabia with a production capacity of 750,000 barrels of oil per day.
This paper provides a theoretical view of how ungrounded and grounded systems behave as well as techniques for providing proper protection for both. It discusses a case study in which a particular system can change between effectively grounded and ungrounded and remain in service.
This paper discusses the line parameter estimation methods for underground cables and presents results from field data and simulations.
This paper presents the functionality, validation, and performance of a state-of-the-art islanding detection and decoupling system in a simulated model for a real-world application.
This paper discusses the implementation of high-speed islanding detection and zone interlocking schemes at a North American refinery using automation controllers. It discusses the scheme layout, protocols used, and algorithms developed to integrate the schemes to achieve optimal performance.
This paper provides field cases that investigate protection system performance when systems are subjected to unexpected switching or interruptions in dc or communications links.
This paper describes a smart automatic synchronizing system that can connect multiple generators in an industrial power system during islanded and utility-connected modes via six different bus-tie and utility tie breakers. The automatic synchronizing system performs matching by controlling multiple governor and exciter interfaces within the facility.
This paper describes the objectives and operating principles of a centralized and automated underground distribution automation system (UDAS) that was developed and applied for rapid fault detection, isolation, and service restoration.
In this paper, the effect of breaker pole scatter on quadrilateral ground distance elements is investigated using a simple two-source power system with two short transmission lines. A case study is included.
This paper discusses complications that can arise from paralleling current transformers and highlights relay design improvements that have been made to add security to these applications.
The paper discusses the benefits of integrating modern substations with a scalable enterprise approach to ensure consistency among substations for operations maintenance and quicker deployment while reducing costs and increasing cybersecurity. Application examples are included.
This paper looks at various commonly used transmission line protective elements and points out characteristics of the line and system to look for when standard reaches and margins cannot be used.
Today's relays are predominantly based on phasors, and as such, they incur a delay associated with the full-cycle observation window required for accurate phasor estimation. This paper discusses a number of protection techniques based on incremental quantities and traveling waves that significantly speed up line protection.
This paper is a transcript of a panel session discussing the relationship between regulators and operators. Panel participants included representatives from Lower Colorado River Authority, the North American Electric Reliability Corporation, Texas Reliability Entity, a law firm, and the National Transportation Safety Board.
This paper explains the principles of negative-sequence differential protection, its basis for excellent sensitivity and speed, and the need for securing it with external fault detectors to deal with the saturation of current transformers. The paper also derives two new protection principles based on negative sequence for generator turn-to-turn fault protection.
This paper presents guidelines developed by CFE to improve and standardize generator protection. Based on the results of simulations and field experiences, the paper describes setting guidelines and improved protection schemes for loss-of-field (40) and stator ground fault (64G) protection.
In this paper, we use gathered event reports to analyze an intercircuit fault that occurred multiple times between two separate voltage levels after a snowstorm. Also discussed are improvements to relay performance during intercircuit faults, including line current differential.
This paper presents the fault current characteristics of a Type 4 wind turbine generator, a case study of a misoperation of directional overcurrent relays in a wind power plant, and recommendations for protecting wind power plants.
This paper teaches how to calculate the source impedance ratio to classify the electrical length of a transmission line for determining protection requirements and setting criteria.
This paper discusses the design and implementation of a system that delivers wide-spectral bandwidth data with precise time stamps over a wide area.
This paper explores technology options for extending local-area networks (LANs) to devices in a substation yard by using wireless technology.
This paper provides a general overview of out-of-band management technology and discusses how it can be applied to a SCADA system to allow remote maintenance of network and computer assets, reduce costs, and improve system reliability.
This paper shows how time-division multiplexing (TDM) and Ethernet communications can be integrated to leverage the benefits of each technology. It also evaluates communications-assisted relay protection schemes and considers future relay protection methods.
This paper investigates the benefits that whitelist malware protection provides power systems and shows that correctly combining malware protection and embedded architecture improves the reliability and cost of ownership of the whole system.
This paper describes how Westar Energy implemented a cost-effective distribution automation system that is now providing a very capable and fully automated fault location, isolation, and service restoration and volt/VAR distribution solution.
This paper discusses ways to overcome undesired tripping on distribution feeders on inrush conditions using both settings changes and second-harmonic blocking.
This paper describes the development of a new Pacific Gas and Electric Company (PG&E) 500 kV transmission line and breaker protection standard, including the motivations for embarking on the project, challenges encountered, and lessons learned during the design effort.
This paper discusses the replacement of the existing motors at a major gas plant in Saudi Arabia with 27,000 hp synchronous motors. It discusses in detail the thermal model selection, custom thermal protection, relay settings, and the coordination study for these motors.
This paper discusses the centralized ground fault detection system for the LADWP ungrounded distribution system. It explains the ground fault detection of ungrounded distribution systems and innovative algorithms developed to identify ground faults, as well as laboratory test and staged-fault field test results.
This paper describes an ac railway electrical distribution system and the challenges associated with the protection of its feeders.
This paper takes an in-depth look at the injection-based stator ground protection principle, reviews state-of-the-art techniques, and reports on a standalone injection-based relay capable of offering 64S 100 percent stator ground protection all of the time.
This paper discusses a generator percentage differential element that uses external event detection logic to provide additional security for external events without sacrificing dependability.
This paper provides a discussion of event analysis and complex faults, along with a few key characteristics to assist in analyzing event report data generated by a complex fault. Finally, an in-depth analysis of a complex intercircuit fault that occurred on the LCRA TSC 138 kV system is provided.
This paper describes a case study of using IEC 61850 GOOSE messaging to simplify lockout and breaker failure tripping in a 345 kV wind generation integration substation.
This paper describes a photovoltaic (PV) plant control system in the field, its operation, and the practicality of solving challenges associated with interconnecting large utility-scale PV installations with the bulk market.
This paper describes the development of a control system that applies local information in coordination with synchrophasor measurements to assess the complete state of the power system and differentiate a local phenomenon from the possibility of an overload-related cascade.
This paper explains the basics of how steam turbines produce power, how they are controlled for extraction and droop, and how governors provide dynamic disturbance rejection in an electric power system. This paper shares a case study project at a refinery and includes discussion of steam control, turbine speed and power control, adaptive boundary conditions, extraction turbine basics, and autosynchronization.
This paper introduces a reliable islanding detection solution, using multiprinciple detection techniques and voting supervision logic, that was proposed, implemented, and tested at a refinery in Texas.
Currents associated with balanced and unbalanced faults through three-phase transformers with various combinations of delta and wye windings are reviewed in this paper and used to develop alternative transformer differential relay testing methods using existing relay test sets with two or three current outputs.
Using dissimilar relays in a pilot scheme presents coordination difficulties due to different operation principles that result in different sensitivities, speeds, and transient responses. This paper presents problems and challenges discovered in real-world applications of dissimilar relays in a pilot scheme. The paper also presents solutions to minimize the risk of misoperation and achieve good fault coverage.
This paper proposes a method to measure transmission line parameters for protective relay settings. This method relies on synchronized phasor measurements taken at both ends of the line and compares them with the calculations from both the equivalent PI circuit and the distributed constant line parameters.
This paper contains illustrations of test methods in IEDs and test devices to verify the performance of Ethernet networks as previously described in the paper "Design and Validation Practices for Ethernet Networks to Support Automation and Control Applications."
The Lower Colorado River Authority (LCRA) is protecting a series-compensated line on their transmission grid for the first time as part of the Competitive Renewable Energy Zone (CREZ). This paper discusses experiences in designing, setting, and validating the new protection system.
This paper examines several common methods for defining restraint and slope characteristics and provides guidance on selection of the correct slope setting.
This paper describes a new fault locating algorithm for two-, three-, and four-terminal lines that is suitable for integration in a line current differential protection scheme.
This paper revisits the IEEE dielectric strength standard, safe design and work procedures regarding CTs, and what happens when a CT is open-circuited under load. The case study emphasizes the critical importance of commissioning tests and root cause analysis to power system reliability.
This paper describes an inverse-time element that adapts to power system operating conditions without changing settings groups.
This paper analyzes various capacitor bank configurations and proposes an economical method to help locate the faulty elements or units for each configuration. The paper also provides results that verify the proposed methods using a Real Time Digital Simulator.
This paper discusses the islanding scheme design at Manifa Central Processing Facility (CPF), the fifth largest oil field in the world, and how the design allows the critical CPF to correctly and quickly identify an islanding condition.
This paper describes the replacement of electromechanical relays with microprocessor-based relays at a steel mill. The microprocessor-based relays enable enhanced safety, event analysis, protection, monitoring, and control.
This paper addresses how event report data from intelligent electronic devices can be transferred into and stored in industrial process historians.
This paper describes testing methods to verify the design and validation of Ethernet networks.
This paper is a tutorial on the protection of mutually coupled transmission lines.
This paper reviews the protection requirements for generators during periods of off-nominal frequency operation. Traditional methods and a novel approach for frequency tracking and compensation are reviewed.
This paper explains the transformer ultrasaturation phenomenon and illustrates it with actual field cases. The paper presents practical solutions to the protection security problem caused by the low level of second harmonic in the inrush current during ultrasaturation, ranging from simple setting and logic choices to a new method of detecting magnetizing inrush with enhanced security.
This paper discusses the physics, theory, and implementation challenges of traveling wave fault locating on overhead transmission lines. It also discusses integration of traveling wave fault locating in microprocessor relays and presents Bonneville Power Administration’s field experience using these relays.
This paper describes the factors influencing the design of the stator winding of a synchronous generator and examines the degree of protection afforded by the various types of differential elements (phase, negative, and zero sequence) for stator winding faults.
This paper discusses the potential misoperation of a high-impedance bus differential relay when surge arresters are located within the relay zone of protection.
This paper discusses the design and implementation of the SONET communications, distribution automation, and video surveillance systems at Taylor Electric Cooperative, Inc. in Texas. These systems help increase service reliability and minimize the impact of an outage to their customers.
This paper discusses an automated fault detection, isolation, and restoration scheme that provides the City of Wadsworth with both an effective volt/VAR control system and a dynamic, system-wide, high-speed trip blocking scheme that can be flexible and continue functioning as the system topology changes.
This paper reviews various approaches to protecting tapped lines, including pilot protection schemes with distance and zero- and negative-sequence directional elements, time-overcurrent elements, line current differential schemes, and stepped distance backup.
This paper presents Precision Time Protocol (PTP) fundamentals and discusses considerations for designing power system networks to achieve submicrosecond accuracies.
This paper discusses how to address the communications integration and activation of adaptive control strategies for photovoltaic solar sites and other distributed energy resources.
This paper gives an overview of commonly used time systems and technologies used to deliver precise time, discusses GPS-based time system vulnerabilities, and explains how to design resilient time-distribution systems for power system applications to mitigate these vulnerabilities.
This paper describes the implementation of a centralized synchronizing scheme for substations with complex topologies.
This paper describes the protection challenges of ac underground cables and transmission circuits with mixed conductor technologies, discusses the challenges of calculating the relay ac input quantities for faults along the underground cable circuit, and then provides solutions for the proper protection of underground cables and mixed conductor technology circuits.
Electrical protective relays contain a great deal of equipment condition monitoring data. Multiple systems are available to read this information for use in both operations and maintenance. This information can then be used to improve operation and maintenance efficiencies. This paper focuses on turning this existing relay information into scheduled work activities that achieve real cost savings.
This paper examines typical implementations for shunt reactors, considers their advantages and disadvantages, and presents protection requirements and solutions required by each implementation.
This paper discusses the San Diego Gas & Electric design process for a special protection system to mitigate high interconnection loading under extreme conditions. The scheme is scalable and accommodates design changes with minimum effort.
This paper discusses methods to calculate line impedance values. A new proposed method uses single-pole open conditions to calculate the line impedance values. The proposed method is validated using EMTP simulations and field data.
In 2012, CFE launched two projects to provide electric service to two isolated rural communities located in the mountains near Tepic, Nayarit, Mexico. This paper describes the off-grid solar-powered microgrids; their protection, control, and monitoring systems; and the operational experience accumulated thus far.
This paper discusses different performance criteria for speed, reliability, dependability, and availability based on international standards. Using these criteria, protection engineers specify the behavior they require for the application and network designers select the technologies and implementation to satisfy the requirements.
The purpose of this paper is to identify factors that determine the resistance coverage for both the mho and quadrilateral elements. These factors are the network parameters such as the source and transmission line sequence impedances, the distance to the fault, and, in the case of quadrilateral elements, the resistance reach setting. Some basic rules are derived based on the testing of elementary networks.
This paper examines several common bus configurations, presents appropriate protection schemes for each configuration, and analyzes the protection scheme complexity, advantages, and disadvantages.
This paper helps identify possible bus protection upgrades that may be required to maintain coordination, minimize equipment damage, and prevent misoperations that can result from the addition of distributed generation.
This paper discusses the philosophy of a comprehensive low-voltage motor control center protection and control system.
This paper discusses the implementation of an Ethernet communications ring network that is used for SCADA, load shedding, and high-speed IEC 61850 GOOSE controls at a large industrial facility.
This paper explains an adaptive underfrequency-based load-shedding scheme that uses an inertia compensation load-tracking (ICLT) algorithm.
This paper describes the methods used to detect communications errors, explains how to convert the commonly used bit error rate measurement obtained from a given communications channel into a quantitative estimate of undetected bit errors, and discusses diagnostic features found in modern digital relays.
This paper presents the integrated system design challenges of the Boquerón 3 substation in Panama. It also presents the technologies and solutions applied to successfully integrate intelligent electronic devices (IEDs) via IEC 61850 with a local human-machine interface (HMI) serving as a local control without IEC 61850.
Practical testing recommendations are presented in this paper. Several common 87L testing scenarios are discussed, including single-relay tests using loopback communications, single-relay tests of the operating and restrain characteristics of the relay using test mode, multiple-relay tests of the characteristics and channel using test mode, and multiple-relay tests of the characteristics and channel without test mode where real-world conditions are simulated.
This paper discusses the factors to consider for sizing current transformers for line protection applications.
This paper provides a tutorial on traveling wave (TW) fault location and describes a TW fault locating algorithm that uses time-synchronized measurements of the TW currents at the line terminals to determine the fault location.
This paper discusses details of the Central American power system, the deployment of PMCUs, a modal analysis-based scheme, and the communications network of the scheme. It also presents events that show how the active power-based and modal analysis-based SCS avoided power system collapse.
This paper discusses the different reactor types currently used, their characteristics, CT selection and performance issues, and different types of reactor faults. The paper also provides guidelines to practicing engineers to evaluate reactor protection design and determine protection elements and relay settings for a high-voltage transmission line shunt reactor.
This paper discusses several key aspects of the electrical design, protection and control, communications network design, testing, and commissioning of an IEC 61850-based substation.
This paper discusses the practical considerations of using this coil in a relay. Complicating and mitigating factors are discussed, along with the performance impact on the relay and practical experiences in the field.
This paper focuses primarily on describing the OT world for those familiar with IT and presents the major OT requirements, security concerns, and the ramification of an impaired OT system compared with an IT system.
This paper briefly touches on protection security but focuses on the dependability of line current differential protection under a number of specific system conditions, including series compensation, power swings and off-nominal frequency, and inverter-based sources. This paper reviews the impact of each of the mentioned conditions and provides illustrations using simulations.
This paper shares new advances in technical solutions that secure supervisory control and data acquisition (SCADA) and energy management system (EMS) communications.
Modern microprocessor-based relays allow for much better protection schemes to protect the distribution substation assets. This paper analyzes several schemes that have recently been implemented at Mid-Carolina Electric Cooperative in South Carolina.
This paper describes the benefits of applying multifunctional technology to water canal control automation systems. Similar to a power distribution application, standardized logic and communications protocols and rugged devices are used to monitor and control water flow while also managing power necessary for the process.
This paper describes several best practice approaches for securing wide-area network (WAN) communication for critical infrastructure applications.
This paper describes a cybersecure synchrophasor platform (CSSP) that uses standard rack-mounted hardware and software in a single bay rack. It is installed at the University of California, San Diego (UCSD).
This paper is a case study of the design process and validation of a simple and effective solution to satisfy the NERC PRC-005 protection system maintenance program requirements. The example solution is a protection system monitoring application for an in-service system at a hydroelectric generating station.
This paper analyzes the key requirements of condition-based maintenance for protection systems. The paper proposes a relay supervisory system (RSS) as a part of protection systems to improve condition-based maintenance and mitigate hidden failures. The paper illustrates the structure and functions of the RSS with several real-world projects.
This paper examines the use of rotor shaft angle measurement in a generator combined with the electrical angle of the output voltage. This provides for the direct measurement of system conditions that could only be estimated or approximated with earlier technologies.
This paper describes novel protection elements that accommodate the unique protection, monitoring, and control challenges of VFD-operated motors.
Four examples of thermal limit curves and their equations are used to discuss the varying plotting practices in use. The paper also includes a method to calculate the stator thermal time constant using two points read from the overload curve when not available from motor data.
This paper presents the use of distance relays for distribution protection to solve some of the distributed generation integration problems. This paper provides real-world event report data to further demonstrate the performance of distance protection on the distribution system.
This paper discusses both existing and future applications for synchrophasor technology in distribution systems.
This paper reviews the design choices available in the development of robust precise time-distribution systems, analyzes the various failure scenarios of wide-area network time systems, and develops test methods to measure time-distribution performance. Finally, the paper discusses methods to minimize or eliminate precise time failures in power system applications requiring precise time.
This paper explores the impact of charging current on the various types of protection elements employed to protect line and cable circuits. It reviews methods used to mitigate the effects of charging current and provides general guidance on settings.
In this paper, we review the benefits afforded by SPS with regard to the robustness and stability of the power system and discuss the challenges issued by SPS to both the power system and the power engineer.
This paper discusses the available technologies in communications, synchrophasors, and monitoring. Examples of small and large systems are described while discussing the types of contingencies monitored. This paper considers a large triple modular redundant subcycle RAS that manages four 530 MW generators and multiple high-voltage transmission circuits.
This paper addresses the automation of distribution systems to reconfigure the network in the case of system disturbances and changes in loads. A discussion of control actions to minimize the number of customers impacted by system events is provided. Additional control functions of an advanced system are also discussed.
This paper discusses details of the Central American power system, the deployment of phasor measurement and control units, a modal analysis-based scheme, and the communications network of the scheme. It also presents events that show how the active power-based and modal analysis-based supplementary control scheme avoided power system collapse.
This paper is a tutorial on how distance relays cope with power swing conditions on the power system. It discusses different methods of detecting power swings and the best method to separate the system to maintain stability and avoid a major blackout if a power swing condition becomes unstable.
This paper shows how modern microprocessor-based relays can simplify applications under temporary bus configurations, eliminate the need for any manual reconfiguration, and improve the performance of protection.
This paper briefly touches on protection security but focuses on the dependability of line current differential protection under a number of specific system conditions, including series compensation, weak systems, open-pole conditions, power swings and off-nominal frequency, and inverter-based sources.
This paper illustrates the calculation of fault currents and voltages during intermediate faults in underground cables, taking into consideration the cable sheath bonding and grounding method.
This paper reviews principles of protection against internal short circuits in transformers of various constructions.
This paper describes a zero-setting power-swing blocking protection method that is independent of network parameters and is based on monitoring the line swing-center voltage rate of change.
This paper examines different communications paths for protection signals, such as spread-spectrum radio, fiber-optic cable, phone lines, and copper pilot wire.
This paper looks at SONET and Ethernet technologies and how they address security and dependability concerns.
In this paper we describe specific requirements of IEEE 1613 along with illustrations of test equipment and fixtures. We provide testing pictures to illustrate testing methods that ensure communications equipment meets these requirements and provides error-free performance. We provide testing results and correlate successful margin testing with observed field reliability.
This paper reviews various channel and time backup strategies for 87L protection schemes and considers utility practices and regulatory constraints related to line protection redundancy, forced line outages, preferred balance between protection dependability and security, ability to provide adequate protection coverage with distance or overcurrent elements, and availability of an independent pilot channel for directional comparison backup schemes.
This paper describes the benefits and shortcomings of TDM- and packet-based communications, when each technology is appropriate for different types of services and/or data, and how combining both transport technologies provides a robust network system that meets the needs of both real-time protection engineers and corporate information technology professionals.
Several classic papers explain the fundamentals of capacitive voltage transformer (CVT) design, operation, and transient response. Distance elements can overreach, particularly in high source-to-line impedance ratio (SIR) applications, which can result in undesired Zone 1 operations. Because this continues to be a problem in real applications, this paper revisits documented field cases using event data in hopes of shedding new light on this known problem.
The paper “Simultaneous Faults on the 11 kV System of an Offshore FPSO Vessel” provides a case study of simultaneous faults that occurred December 5, 2009, on the 11 kV power system of a floating production, storage, and offloading vessel located in the Norwegian sector of the North Sea. This paper includes additional analysis and forensic work that were not available at the time the previous paper on this event was published.
Synchronizing a generator to the power system must be done carefully to prevent damage to the machine and disturbances to the power system. Traditionally, power plants include a synchronizing panel to indicate what adjustments the operator should make to the governor and exciter and when it is acceptable for the operator to close the breaker. In many cases, the process is automated using an automatic synchronizer with manual control available as a backup.
This paper describes the design of a load tap changer control for up to four parallel transformers using a modified circulating current approach.
One of the traditional techniques for detecting power swings uses a dual-quadrilateral characteristic. It is based on the measurement of the time interval it takes the positive-sequence impedance to cross two blinders. Another technique monitors the variation of the swing center voltage approximation. This paper presents a performance comparison between applications of these two techniques in cases derived from a sample network transient simulation and in cases recorded during real operations in the field.
Nucor Steel experienced sporadic tripping of their instantaneous ground fault protection on the feeders to their arc furnaces during magnetizing current inrush to the transformer upon energization. The engineering staff at Nucor Steel gathered event reports from the microprocessor-based feeder relay both to diagnose the cause of the tripping and to characterize the inrush current of the electric arc furnace transformer. With this information, they set about to design a relay setting scheme that would remain secure during inrush while not sacrificing sensitivity or speed. This paper reviews the factors affecting magnetizing current inrush on an electric arc furnace transformer and then describes the steps the Nucor Steel engineers took to analyze and solve the problem.
This paper compares the improved performance of remote communications-assisted decisions and explains important digital message performance metrics useful in the design and specification of communications channels.
This paper provides examples to illustrate basic programming techniques. IEC 61131 logic processing examples are shown using data types from IEC 61850 MMS, GOOSE, and DNP3 protocols. Additionally, innovative IEC 61131 logic solutions are shown that enhance secure access control of NERC CIP critical cyberassets in any electrical substation.
This paper demonstrates the use of synchrophasor data in displaying and analyzing system events in order to improve system response to load and transient events. Examples are given of actual events captured using wide-area and local synchrophasor measurements.
This paper describes how using a closed-loop feedback control scheme and a proportional and integral controller can maintain the power factor in the required range.
This paper examines various time sources available for use in power system applications, including GPS, Network Time Protocol/Simple Network Time Protocol (NTP/SNTP), IEEE 1588, National Institute of Standards and Technology (NIST) radio station WWVB, and rubidium standards. Each time source is analyzed and evaluated in the following areas: accuracy, distribution methods, applications, costs, benefits, and weaknesses. Time-distribution systems are described that address reliability, scalability, cost, and security.
This paper reviews the first principles of dependable and secure Ethernet message delivery and the methods network designers need to understand and use to increase the likelihood of success.
This paper explores a method of voltage control, with the purpose of energy conservation. The traditional approach of conservation voltage reduction is not always the right approach for all types of feeder loads; some loads run more efficiently at a higher voltage.
This paper compares two similar utilities who took two very different approaches on technology and competing in the ever-changing utility world. One chose to be on the very leading edge of technology while the other chose to keep things as they were and not change with the times.
This paper is a case study of the design process and validation of a hydroelectric generating station protection system monitoring (PSM) application that provides an automated system to meet many of the requirements of NERC PRC-005.
While different IEDs have different functions available for automation and integration, a major difference between serial and Ethernet ports is that these multiple functions may be performed on the same Ethernet port. Automation capabilities in IEDs increase with the use of Ethernet connections, but the connection and processing complexities increase also.
This paper addresses the performance, reliability, security, and cost tradeoffs of wireless communications approaches for power delivery automation applications.
This paper discusses a best engineering practice of designing the Ethernet communications network based on the application requirements without directly specifying an Ethernet network redundancy method. In essence, it is a bottom-up approach to Ethernet network design based on protection and control requirements.
This paper presents a fully automated real-time fault location system that provides accurate fault location information for multiple transmission lines and makes the results available to system operators and maintenance personnel.
This paper presents a fully automated real-time fault location system that provides accurate fault location information for multiple transmission lines and makes the results available to system operators and maintenance personnel.
Distribution network operation periodically exceeds the loading capabilities of a substation power transformer. This can result in accelerated insulation aging and, in some cases, failure due to complete deterioration of the insulation. The solution described in this paper allows users to monitor critical substation transformer assets with a comprehensive transformer thermal model per IEEE C57.91-1995.
This paper details the protection methods applied to traditional grounded and ungrounded capacitor banks, as well as a number of novel banks with connections that are far from traditional. This paper discusses the application, sensitivity, and speed of the applied protection schemes.
This paper illustrates how teleprotection schemes can be designed to suit both the new challenges in distribution networks and the characteristics of the wireless channel.
This paper investigates several real-world events with data from both motor starting reports and event records. The data demonstrate the value of having devices capable of recording motor data during starts and fault events and of capturing and reviewing such data for the purpose of determining root cause.
This paper first presents the challenges in the existing power system and the requirements for the ECS. Then the ECS solution design and communications network are described.
This paper discusses the implementation and application aspects of traveling wave fault location in a protective relay. Performance limitations are discussed, as well as system requirements and practical installation considerations.
Line current differential schemes that use external time sources must provide a well-defined response that suits user preferences in situations when the time source is lost or degraded beyond the point of safe usage in protection applications. This is often referred to as time fallback logic. This paper presents several time fallback modes, varying with respect to balancing protection security and dependability.
This paper describes a new algorithm for fault location for two-, three-, and four-terminal lines suitable for integration in a typical line current differential scheme. The paper presents the new algorithm in detail, includes examples of its operation, and presents test results based on simulations as well as some application considerations related to the loss of communications or data synchronization between the 87L scheme relays.
This paper presents collected events to demonstrate the use of synchrophasor data to update and improve system models and system operation. Examples are given of responses to events captured using wide-area synchrophasor measurements. Phase angle, frequency, and voltage responses are displayed with discussion of the events, synchrophasor data views, and insights to be gained from the different data types. This paper
advances the understanding of wide-area measurement systems, which provide the newest development in system monitoring.
This paper details how security and dependability are addressed in a low-impedance relay. The characteristics of zone switching, current transformer location during breaker bypass, and transition transients are addressed. Reliability and security of low-impedance systems are compared to distributed and high-impedance protection schemes. Conclusions on speed requirements and impacts on protection are presented.
Auxiliary process units, such as power plants or water treatment facilities, serve key roles in supporting operations and maintaining regulatory compliance. This paper describes field-proven control technologies and methods to remotely control and monitor these units in order to improve process visibility, optimize staff deployment, increase monitoring equipment reliability, and maintain regulatory compliance. It includes a discussion of integrated web-based operator interfaces, the application of network security mechanisms, and appropriate control system environmental specifications.
This paper presents the advantages of fast overcurrent detection combined with arc-flash measurement to produce a sensitive, fast, and secure tripping scheme.
The purpose of this paper is not to review generators’ protection principles, because this has been done extensively elsewhere, but rather to revisit the basic physical and engineering principles behind the interaction between a synchronous generator AVR and its associated limiters and some of the generator protective functions.
Commissioning protective relays has changed with the increased use of microprocessor-based relays. Many relays have multiple functions, and logic that used to be contained in wiring diagrams or control schematics now resides in relay settings.
The paper employs MATLAB simulations to compare the dynamics of the thermal model with that of an overcurrent implementation during cyclic overloads.
This paper discusses the thermal protection provided by rotor and stator thermal models defined by the thermal limit curves and supporting motor data.
The purpose of this paper is to show how power swing representation in the impedance plane will depart from the classical theory when complex AVRs are used on modern generators.
This paper illustrates the use of synchrophasor data to view frequency stability, verify system independence, and observe the synchronization point.
This paper discusses a reactive power control system that utilizes a central automation controller to regulate both power factor and voltage at the point of utility interconnection.
This paper is a tutorial on the operating characteristics of 87L elements. We focus on practical implementations actually available in present 87L relays.
This paper discusses the test setup and procedures necessary to perform arc-flash detection system testing.
This paper centers on the selection of the impedance plane for analyzing the operation of distance, power swing detection, and directional elements.
This paper assesses the probability of an out-of-phase reclosing event and identifies and quantifies the stress to the various elements that make up the distribution network. The analysis is compared with relevant standards and guidelines. As a result, the reader will gain better insight into the requirements for anti-islanding.
This paper examines the design and implementation of a breaker failure scheme using a synchronism-check element in addition to the traditional overcurrent element.
This paper presents several approaches to testing 87L schemes. These approaches include verification of relay hardware, firmware and settings, channel performance, and, if used, external time sources. The paper also describes features of line current differential relays and multiplexers to aid testing.
This paper describes the application of Ethernet-based protection signaling (IEC 61850 GOOSE messaging) to implement the complete protection and control system of the Tabasco 400/230 kV substation.
This paper presents best practices and lessons learned for the design, maintenance, analysis, and reporting for underfrequency load shedding implemented in microprocessor-based relays.
This paper considers line current differential schemes from the point of view of communications and data synchronization. The goal is to improve understanding among relay practitioners of some of the unique and key aspects of digital line current differential schemes: communications, data handling, and synchronization. This paper also seeks to improve the appreciation of line current differential protection applications and related network requirements among utility communications engineers.
The paper studies the different trajectories of the current ratio depending upon contingency conditions: the type of element (phase or sequence), the line loading, the line length, the level of fault resistance, the level of CT saturation if any, the presence of an open pole, or similar conditions.
This paper examines the effects of saturation on various elements, and gives application guidelines that eliminate or minimize the risk of CT saturation.
This paper reviews basic concepts of differential relays and CTs and then describes a study that was performed to determine secure settings for a relay in a specific bus protection application.
In this paper, we describe the effects of single-pole tripping (SPT) and single-pole reclosing on power system transient stability. We discuss the application requirements for SPT schemes, describe SPT schemes applied in Mexico, and provide statistical data on SPT scheme operation.
Symmetrical components are a practical tool for analyzing unbalanced conditions on balanced systems.
This paper describes a sequenced automatic restart logic algorithm programmed in microprocessor-based relays for medium-voltage induction motor protection that were installed in a large greenfield petrochemical complex.
This paper presents a new, reliable solution using arc-flash light detection supervised using overcurrent protection to reduce the risk of an arc flash in low- and medium-voltage panels and switchgear equipment, thereby eliminating false trips from lighting and providing the fastest detection and tripping possible.
This paper uses a greenfield offshore platform project as the impetus for investigating the technical details of modern communications networks and their potential impact on power system operations, while navigating some largely misunderstood concepts.
This paper considers the sensitivity of essential line protection elements: ground distance and ground directional overcurrent elements applied as time-coordinated functions or in pilot-assisted protection schemes and line current differential schemes.
This paper discusses the existing SCADA system and the recently installed wide-area monitoring system at the Power Grid Corporation of India Limited Northern Regional Load Despatch Centre.
In this paper, we show how fully redundant cybersecure systems can be assembled using standard PMUs and standard commercial software. Using the information available from the fully redundant system, we also show an example of how real-time grid damping calculations can be used to prevent grid collapse.
A mobile protection unit implements a minimize-simplify-optimize philosophy to provide a custom designed and manufactured, portable, completely self-contained, fully functional, quickly transportable substation relay enclosure. The unit is designed to meet relay protection and teleprotection communications requirements for a diverse set of applications, permitting the rapid and temporary restoration of transmission facilities or feeders to supply load following a catastrophic event.
This paper provides a road map for both compliance and day-to-day operations to maintain safe and secure control systems for any industry.