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When influenced by quasi-dc ground currents, the magnetization characteristics of wye-connected transformers produce second harmonics that may approach or surpass second-harmonic levels commonly experienced during transformer inrush events. In this paper, we discuss a saturable transformer model simulation composed to create a matrix of tests that varied the magnitude of transformer internal fault current and the magnitude of quasi-dc ground current. We applied test currents on two transformer differential relay designs. One set of test currents was to validate that the relays remain secure for geomagnetically induced current (GIC) saturation, and the other to compare how the relays perform for internal faults with varying amounts of fault resistance and increasing levels of GIC. We explore cross-harmonic blocking and harmonic restraint as variables and evaluate the relationship of the pickup levels for the operate/restraint curve. We include recommendations for possible mitigation techniques.
This paper reviews the basics of coincidence timing for shaping distance element characteristics (mho and quadrilateral), explains the benefits of using coincidence timing, shows digital implementations that far surpass the dreams of analog relay designers, and presents test results from an implementation that uses the best of both worlds—analog principles implemented in a digital relay.
This paper addresses concerns about unintentional and dangerous mistakes hidden in plain sight when ECS design teams implement digital trip circuits based on IEC 61850 process bus protocols. It draws parallels between the circumstances surrounding infamous failures in aerospace and aviation and the hidden dangers a lack of preparedness can produce in ECS design.
This paper examines undesired operations (UOs) of differential elements that protect shunt reactors installed on high-voltage and extra-high-voltage transmission lines, particularly UOs that occur because of a CT and CT burden mismatch. Field events and tests are included, as well as a model of the power system that illustrates system sensitivity. Different techniques for mitigating UOs are discussed.
This paper presents an approach to increasing the reliability of auxiliary dc control circuits by combining multiple sources and providing ride-through capabilities in the event of a loss of all input sources. It highlights technical benefits and applications while showing how increased source diversity can improve the availability of dc control power for protection and control, as well as for tripping circuit breakers.
This paper discusses the challenges, solutions, and design details of a special protection system (SPS) installed by the transmission system operator, Elia, in Belgium. It discusses the SPS focus on security and availability, and the hardware-in-the-loop testing of the whole system before it was commissioned.
This paper reviews permissive and blocking pilot schemes for protection of transmission lines. It covers principles of operation, settings considerations, the importance of coordinating the forward and the reverse fault detectors, applications to multiterminal lines, and single-pole tripping. The paper also describes add-ons used for dependability of the permissive schemes: open breaker echo, weak-infeed logic, and channel failure logic. The paper introduces a crossover permissive-blocking scheme that eliminates the need for additional engineering required by many applications of permissive schemes, while allowing fast tripping without the coordination time. The scheme is easy to configure and test, and it uses two pilot bits in a multi-bit digital protection channel.
This paper illustrates design and operational considerations for use when replacing elements of hardwired protective relay trip circuits with digital messaging via process bus networks based on IEC 61850 GOOSE, Sampled Values, and Precision Time Protocol. The paper introduces topology designs and process bus communications designs in use at Southern California Edison and Commonwealth Edison Company, as well as research being done at Puget Sound Energy.
The challenges of designing synchronizing systems for utility and industrial power systems have become more complex. Traditional synchronizing technology limits the possible solutions to these challenges. In this paper, we discuss the challenges of conventional synchronizing systems and show the advantages of using the advanced automatic synchronizer (A25A) with new digital secondary system (DSS) technology as a practical solution.
Many utilities are migrating their network infrastructure from TDM/SONET to packet-based technologies such as MPLS. This paper uses the alpha plane with a custom phase angle comparison approach to study live data taken over a multi-week period from Central Lincoln PUD’s in-service line current differential protective relays. The paper compares the performance of SONET with a packet network before and after migration and show it is possible to achieve SONET-grade performance over packed-based network using virtual synchronous networking (VSN) technology.
This paper describes the design and testing of a system preservation scheme on an islanded system at Red Dog Mine in Alaska, and includes the considerations necessary to the unique circumstances of the system.
This paper presents a case study of double-circuit faults on SDG&E’s 69 kV system that caused multiple relays to operate. The paper explains the relay operations, focusing on the directional element, and concludes with lessons learned. The paper also emphasizes system-wide, time-coordinated event report analysis, which was indispensable to the root cause analysis.
In February of 2018, a current differential relay protecting a 138 kV/69 kV autotransformer tripped for an out-of-zone ground fault. System conditions were such that the low side of the autotransformer was open, but the relay event reports showed fault currents present on the low side. Initial investigation hinted at a CT secondary circuit problem, and three more faults that occurred the following week helped narrow it down. This paper describes the investigation into these faults, how root cause was found, and how ground potential rise can cause phantom currents to flow in relay CT circuits.
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.
This paper discusses the challenges with generator breaker failure schemes and proposes three methods of improving generator breaker failure protection under low-current conditions. The paper also provides a detailed analysis of breaker pole stuck conditions.
In this paper, we discuss the various operational technology tools available for the performance analysis of mission‐critical Ethernet-based communications networks. We describe techniques for simple test cases that provide performance quantification of the communications path in terms of determinism, latency, and availability, using as an example tests performed at the Enel Smart Grid Lab (created by E‐Distribuzione in Milan).
Many utilities with overhead distribution lines make tradeoffs when designing protection schemes. Ideally, the system minimizes fault energy by limiting fault duration in high-risk environments, yet maximizes power quality and availability in urban areas. This paper describes how these contrasting goals are achieved using wireless protection sensors to identify the faulted line section and instantly transmit fault messages to a recloser control. With this real-time information, the protection logic adapts its response for the faulted section, dynamically applying fast overcurrent elements with a truncated reclosing sequence to reduce fault energy in high-risk sections, using standard schemes elsewhere.
This paper discusses switch onto fault (SOTF) settings for dependable fault coverage and security for heavy load conditions when SOTF voltage reset is not available. A case study is included to illustrate the speed sacrifices made when a distance element, rather than an instantaneous element, must trip during an SOTF condition. The paper also discusses the effects of source impedance ratio and considerations during use of high-speed reclosing.
This paper presents an efficient and systematic approach for evaluating merging units. It offers engineers help, particularly during merging unit testing, in understanding certain characteristics of a merging unit and in gaining confidence with Sampled Values technology.
This paper describes how CTs saturate in a simple and intuitive way. The paper describes symmetrical and asymmetrical saturation, remanence, the CT equivalent circuit, the CT excitation graph, ANSI ratings, and how to analyze CT performance using simple equations and tools. It then shows how to detect CT saturation in relay event reports and how relay operation can be compromised during CT saturation.
This paper presents improvements in wind farm fault identification systems based on innovative fault sensor systems with wireless communications.
This case study, focused on Alabama Power, describes a topology-based coordination scheme that leverages the utility's high-speed communications infrastructure to provide advanced distribution protection.
This paper discusses the effects of loss of field (LOF) on the generator and the connected power system. This paper also presents the implementation details of a new adaptive P-Q plane-based LOF protection for four zones.
Avista Utilities has been in the process of upgrading a set of 8.8 MVA, 4 kV, 48-pole, 60 Hz generators at one of their hydroelectric facilities. The authors took this unique opportunity to perform destructive testing on one of these generators prior to its scheduled upgrade. This paper describes the planning and execution components of this destructive testing and also discusses the lessons learned throughout the entire process.
This paper describes the design and commissioning of a controlled switching scheme to energize and de-energize a 485 MVA, 220/18 kV transformer. It highlights the use of high-resolution oscillography to supplement breaker timing tests to obtain a critical breaker advance-time setting for the scheme. The results show that by using a controlled switching device and fine-tuning its breaker advance-time setting, inrush currents exceeding 6 pu were reduced to less than 0.2 pu.
This paper presents an out-of-phase synchronization (OOPS) protection scheme for detecting faulty generator synchronization and providing high-speed tripping. It demonstrates the performance of the scheme with a real-world event in which a steam turbine generator was synchronized 180 degrees out of phase. The paper also includes a discussion of testing methods for verifying synchronization circuits.
This paper describes a new breaker failure scheme for generator breakers that is based on voltage measurements to detect the failure of a generator breaker to open and separate the generator from the power system. The paper discusses details of the scheme and application and operation considerations relative to generating plant bus topology.
This paper discusses two of the most important IEC 61850 Edition 2 test features: Mode Control (widely referred to as "Test Mode") and Simulation. The paper first briefly describes the test features in Edition 2 and then illustrates the applications and guidelines for these features in depth, including potential pitfalls. Finally, the paper provides examples related to various utility domains as a practical guide to help the reader make informed choices on how to use these test features, independently or combined. The use cases include asset additions, commissioning, and multiowner systems.
This paper describes how an autonomous microgrid control and protection system is automatically configured without human involvement. Two variants of this solution are shared: one for a rapidly deployed, mobile power system and one that integrates a fixed campus power system.
This paper discusses the design and implementation challenges of implementing redundant logic controllers. It examines how communication channels affect data process and how reliability requirements affect design decisions. The paper also examines the decisions the implementers must make when creating a redundant controller solution. The paper includes a case study of a recent implementation, which covers a utility's decisions in implementing redundant logic controllers.
This paper investigates several features that could be integrated into solar power plant controllers. It considers the current state of the industry and examines the technical, regulatory, and implementation challenges of potential new features in power plant controls for solar power.
This paper discusses the application of software-defined networking (SDN) in a substation environment using IEC 61850 GOOSE protocol. It reviews the benefits of SDN over traditional Ethernet networking in the areas of fast failover, network visibility, network engineering, and cybersecurity.
This paper discusses the functional overlap between the data sets required by NERC PRC-002 and PRC-005 and provides several examples of how these data can enhance power system maintenance programs.
This paper describes the implementation of a circulating current scheme that uses IEC 61850 GOOSE messages to provide automatic voltage regulation for up to four paralleled power transformers.
This paper presents a design of a variable-window filter for protection applications. The filter uses a full-cycle sliding data window until a disturbance is detected, at which time the window size is considerably shortened to include only disturbance samples and exclude all pre-disturbance samples. With the passing of time, the window size grows to include more disturbance samples as they become available. When the window reaches its nominal size, it stops extending and starts sliding again. By purging the pre-disturbance data, the new filter strikes an excellent balance between protection speed and security.
This paper explains how the X/R ratio and the relay operating time affect the asymmetrical current breaker rating. The paper proposes how to derate a breaker for the relay operating time that is shorter than the standard reference relay time of 0.5 cycle. The paper calculates the “rating loss” due to fast tripping and concludes that applying customary margins when selecting breakers may be sufficient to mitigate the effect of ultra-high-speed relays without the need to replace breakers.
This paper discusses an application of software-defined networking (SDN) to meet stringent network performance and cybersecurity requirements. It compares this application to traditional spanning-tree-based networks to show SDN's ability to meet and exceed those requirements.
This paper presents a new distance protection element implementation that is based on the analogue principle of coincidence timing. The paper explains the basics of coincidence timing and the many advantages of this approach. The new algorithm has been implemented in a hardware platform and consistently operates with speed on the order of half a cycle. The paper shares laboratory test results from hardware-in-the-loop tests and illustrates the new approach using a field case.
This paper describes the design, implementation, and operational results of an in-service load-shedding scheme for a large chemical industrial complex in Mexico. The proposed load-shedding scheme uses high-speed IEC 61850 GOOSE messages and synchrophasors, which provide apparatus monitoring and control, remote load shedding, and monitoring of power measurements for onsite generators and the interconnection with the electric utility system.
This paper presents line-monitoring logic for continuous monitoring of high-voltage power lines by using traveling waves for the purpose of preventive maintenance through identifying and locating fault precursors to reduce the count of line faults and unscheduled outages.
In this paper, we consider some of the similarities and differences between IEEE and IEC guidance on CT selection. We use CT models verified using high-current tests on a physical CT. Then using these models, we determine CT sizing guidelines and relay settings for a generator and transformer differential relay.
In this paper, we make a comparative analysis of the performance, cost, complexity, resiliency, and security of several in-service digital secondary system process bus solutions for devices with complete station bus capabilities based on the IEC 61850 communications standard.
In this paper, established industrial control system (ICS) methods and standards are used to design defense-in-depth cybersecurity methods for digital communications within an energy control system (ECS) communications network.
This paper documents how PPL Electric Utilities improved high-impedance fault (HIF) detection on their distribution system by adding an HIF detection algorithm and updating metering technology while still using their existing protective relaying. The paper documents live downed conductor detection testing and the associated findings along with lessons learned from the initial pilot and subsequent enhancements to the system, including adding HIF tripping logic.
Several transmission protection misoperations have occurred because of the operation of pilot protection schemes during transmission line switching. In this paper, we discuss many solutions implemented by various utilities and compare the solutions against real-world events.
Power systems are technological marvels. However, as protection has become faster, automation more prevalent, and communications wide-spread, protection systems have become more complex. A. R. van C. Warrington wrote, "In spite of good intentions ... there is a tendency to extend the operation of relay schemes by adding additional features until complexity results and then it becomes necessary to re-design." Is there an opportunity to reset the complexity curve and still achieve high-speed, sensitive, selective, and simple protection systems that provide automation, system visibility, and cybersecurity? We believe the answer is YES!
This paper reviews the merits of controlling autoreclosing based on the location of the fault. Special attention is given to hybrid lines comprising underground cable sections and overhead line sections. The paper explains how the traveling-wave technology allows precise fault locating on these lines and how to use the fault location for autoreclosing for faults on overhead sections and blocking autoreclosing for faults on cable sections.
This paper revisits different grounding practices in distribution power systems. It discusses how system grounding and load connection impact the sensitivity of detecting higher-impedance ground faults. The paper discusses possible ways of improving the ground fault detection sensitivity for different systems. The paper illustrates that no single economical technology or practice available today can guarantee 100 percent reliable high-impedance ground fault detection. To provide a perspective with respect to ground faults versus fire ignitions, the paper reviews several staged downed conductor tests and summarizes key research findings in released energy of arcing faults and fire ignition.
This paper shows why correct CT selection is important for the reliable operation of generator differential protection and, for instances where the CTs cannot be matched properly, provides insight into different mitigation strategies. The paper examines a case from a user who encountered a generator relay misoperation during black-start conditions and discusses how the problem was solved using the strategies presented in the paper.
This paper discusses a pilot installation experience of using ultra-high-speed (UHS) protection and traveling-wave fault locating on a hybrid line at a power utility in India. The paper presents details about the hybrid line pilot installation, commissioning of the UHS relays for protection and fault locating, and overall performance of the UHS relays for faults recorded on the pilot system.
This paper offers practical corrective action plans (CAPs) that can provide PRC-026 compliance in nearly all cases without replacing the relays or preventing trips for true out-of-step power swings. The paper discusses various types of power swing blocking (PSB) and out-of-step tripping (OST) schemes and other features available in multifunction line relays that can help with compliance. Many of the CAPs presented are not the solutions you expect.
This paper provides insight into the similarities and differences in the IEEE and IEC CT sizing requirements for generator and transformer differential applications and presents easy-to-use CT requirements and setting guidance for secure protective relay application. An application example is included.
This paper describes an arc-flash event that occurred at the first 10 MW grid-tied energy storage plant in India. It explains how an installed arc-flash protection application used light sensors in conjunction with ultra-high-speed overcurrent elements to trip quickly. The paper also explains how important the inter-tripping between different voltage levels can be for reducing incident energy and preventing further damage from an arc flash.
This paper describes a new algorithm that uses only single-ended measurements to reliably detect broken conductors and estimate their location by using the charging current of the line. We can use broken-conductor detection to trip the breakers before the conductor touches the ground and creates a shunt fault and block any attempt to reclose the line onto this permanent fault. The proposed algorithm is validated by three field events from 57.1 kV and 220 kV lines and results from EMTP simulations.
This paper discusses a Public Service Company of New Mexico (PNM) project to intersect an existing 345 kV series-compensated line. It also discusses the challenges encountered when protecting overcompensated extra-high-voltage lines and provides a performance comparison of phasor-based and ultra-high-speed protective relays using real-time digital simulation.
Every high-voltage transmission line draws capacitive charging current that a line current differential (87L) relay must compensate for; otherwise, the protection scheme might misoperate. This paper reviews charging current theory, calculations, and compensation methods. It also provides guidelines to help protection engineers determine when charging current compensation is required for an 87L scheme.
This paper discusses protection scheme design methodology and challenges for shunt reactor applications. The paper discusses the possible improvements to the protection scheme design in consideration of tertiary dry-type reactors using modern relays. In addition, the paper also discusses the overall protection design as applied to the San Diego Gas & Electric (SDG&E) system for reactor bank and related tertiary bus applications.
This paper shares a set of equations for sizing chokes for isolated-parallel power systems. The theory behind each equation is shared, and chokes are sized for an example power system.
This paper explores security weaknesses in the GOOSE protocol and how to mitigate them using managed switches and software-defined networking (SDN).
In this paper, the Purdue Model is used to design defense-in-depth cybersecurity methods to implement human-to-machine and machine-to-machine digital communications within an energy control system (ECS) communications network. The ECS communications architecture is divided into multiple appropriate levels with unique requirements and features from the process up through the station and finally to the control center.
This paper discusses how a centralized user and password management system can enhance the security of secondary system infrastructure. The paper also discusses how this system can enhance substation infrastructure without interrupting operations.
Protective relays provide extensive information that can be retrieved and linked with operational and maintenance topologies, either manually or automatically. This paper details the data that can be retrieved from modern digital protective relays only and how these data can be used to develop an equipment maintenance program that saves time and money.
This paper discusses the basics of control and data planes in a network system. It also compares software-defined networking (SDN) performance with that of traditional Ethernet switches and discusses how SDN optimizes the network in an automation system.
This paper discusses how the implementation of a load-shedding system in a paper mill increased the reliability of the mill while minimizing operating costs and capital losses during unplanned events. The paper further discusses, in detail, the dynamic modeling of a double-extraction steam turbine and the validation of the load-shedding system in a closed-loop environment.
This paper presents simple rules for the correct selection of transformer differential relay compensation settings and their application to real-world installations.
This paper details an arc-flash mitigation scheme installed on 50 unit substations at a Midwestern pulp and paper mill, which reduced the average arc-flash rating by 90 percent.
This paper provides a comparative analysis of the various communications network topologies and process instrumentation and control devices. The analysis includes the reliability of various systems in terms of unavailability. The cost and complexity of each solution is also evaluated along with the level of expertise required by maintenance teams to detect failures and restore system operation. Performance is evaluated based on the speed of detection and reaction to a power system fault.
This paper explains the principles and illustrates the operation of distance protection including traditional mho and quadrilateral elements, new time-domain incremental quantity distance elements, and future distance elements based on voltage and current traveling waves.
This paper presents a turbine load-sharing and load-shedding system for an islanded liquefied natural gas (LNG) facility in Australia. The system includes three independent and redundant load-shedding schemes: process-based contingency load shedding with predefined load group and load pairs, high-speed underfrequency-based load shedding, and progressive overload shedding with system frequency supervision.
Traveling-wave fault locators are very accurate. To retain the inherently high per-unit fault location accuracy, utilities need a method to convert the per-unit fault location to the tower identifier in order to use their mapping data when dispatching line crews. This paper presents several methods for improving accuracy of tower position information for the purpose of dispatching line crews. These methods use past faults for which the location has been confirmed with high confidence, line taps, and Optical Time-Domain Reflectometry (OTDR) tests for identifying splice locations in the Optical Ground Wire (OPGW) cables.
This paper explains best-known practices and tools available for commissioning arc-flash mitigation systems. Topics discussed include how to select and configure test equipment, interpret device self-test diagnostics, and validate system performance with event reports and time-synchronized devices.
This paper discusses how ground faults affect distance relays that are set to reach through delta-wye transformers.
This paper examines single event upsets (SEUs), their causes, mitigation methods, and most importantly, how engineers can make the protection system more resilient if or when SEUs occur. The paper quantifies how often SEUs are likely to occur and suggests and compares some practical application and control design solutions.
Confidence in microprocessor-based protective relays has steadily increased over the four decades since their invention. As the service life of these devices exceeds multiple decades, questions regarding when and how to strategically replace these relays are increasing. This paper defines terms associated with the reliability of protective relays, provides field-observed life cycle reliability data, and suggests replacement strategies.
This paper examines the problem of determining a system’s X/R ratio when there are parallel circuits at the fault and no single X/R precisely describes the current. It develops a rigorous method to construct and algebraically solve the differential equation of the fault current, thus providing the accurate transient component. Examples are provided, and the concept of a variable X/R is proposed to consider the actual impact of the transient current.
This paper documents the experience of applying an ultra-high-speed relay that uses incremental quantities and traveling-wave-based protection elements on a 115 kV line. The paper provides extensive event analysis to evaluate the performance, security, sensitivity, and dependability of the relay and presents the lessons learned from the application.
Public Service Company of New Mexico (PNM) selected ultra-high-speed (UHS) line protective relays for their 345 kV lines, in addition to their phasor-based protective relays. In this paper, we discuss the procedures followed during the commissioning, bench, and end-to-end testing of the PNM UHS line protection.
This paper presents implementation details of a generator protection scheme with characteristics tailored to the generator capability curve of the machine. The proposed scheme provides improved generator protection and simplifies coordination of scheme elements with the generator underexcitation limiter.
When designing Sampled Values-based (SV-based) substations, engineers must prove that SV-based schemes are as secure and reliable as traditional protection systems. This paper discusses the impact of communications conditions on line protection, provides benchmark test results, and highlights considerations that protection engineers should factor in when implementing SV-based line protection schemes.
This paper provides accounts of undesired operations that have occurred in real recloser installations, reveals the root cause, and offers techniques to mitigate against future failures. The paper categorizes recloser installation misoperations as single-pole tripping, reclosing, and apparent miscoordination issues. The paper recommends commissioning and maintenance practices as well as tips for troubleshooting and repairing recloser systems.
This paper is a tutorial on protection applications of sequence components, focusing on advantages, limitations, and application considerations.
High-frequency traveling-wave technology is entering the power system application mainstream, bringing with it an unprecedented level of highly accurate signal detail. This paper documents and explains some of the more surprising, lesser-known, and strange-looking waveforms captured while monitoring high-voltage transmission lines with megahertz sampling.
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.
This paper examines the application of GOOSE over Ethernet radios and the associated challenges. The paper shares results from a real-world implementation, including results from GOOSE latency tests for protection and control applications.
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 explores how operational technology software-defined networking (OT SDN) can deliver benefits for OT networks in determinism, traffic control, and failure recovery by using an application-focused, proactive, and predictable design based on a deny-by-default cybersecurity architecture. This paper then describes an approach to designing and deploying an OT SDN network to incorporate these benefits by focusing on discussing design processes (such as requirement gathering, topology design, and path planning) and engineering considerations (such as automation, validation, and testing).
This paper discusses cryptographic system implementations in operational technology (OT) environments and how protocols such as IPsec, TLS, and DNP3-SA can be mapped onto common distribution communications architectures. It also provides recommendations for OT system owners and manufacturers who wish to implement cryptographic solutions.
As utilities implement packet-based Ethernet transport technology, communications engineers must design pilot channels that still meet strict protection application requirements. This paper describes a deterministic transport solution for critical traffic over packet-based wide-area networks (WANs) that is compatible with both Multiprotocol Label Switching (MPLS) and Carrier Ethernet systems. Live implementation performance data are included.
This paper reports on an experimental investigation that uses wavelength division multiplexing in high-performance power system protection applications. The investigation was performed using the latest generation of carrier-grade optical transport network (OTN) equipment. The paper documents the performance, opportunities, and pitfalls associated with this application and outlines practical strategies for the seamless integration of protection systems with the latest generation of OTN technologies.
This paper discusses many of the common challenges of integrating intelligent electronic devices (IEDs) in an IEC 61850 environment, how to diagnose problems using packet analysis tools and IEC 61850 MMS browsers, and what settings in the IED or Configured IED Description (CID) file need to be adjusted to resolve these challenges.
This paper discusses the protection of transformers with dual breaker terminals. It covers the compromises that often must be made between security and sensitivity of protection for this common configuration. The paper describes methods for designing transformer protection schemes and presents guidelines for selecting CT ratios and setting restrained and unrestrained differential elements for these applications.
This paper discusses some of the potential causes of open-phase conditions, their impacts on power system operation, the challenges in detecting them, and some novel methods developed to detect them. It discusses the implementation of these methods in microprocessor-based protective relays at several nuclear power generating stations. The paper also presents field results of a successful open-phase detection.
In distribution systems, power utilities are integrating intelligent sensors and advanced communications that go beyond substations and require minimal human interaction. This paper describes many of the technologies and sensor systems that utilities can employ to unlock new distribution applications and enable efficient energy delivery.
This paper demonstrates using the transformer through-fault capability curves of IEEE C57.109 to evaluate the through-fault damage of various reclosing sequences on an example distribution transformer. The method described in this paper provides distribution owners and operators with a tool to consider the reliability benefits of reclosing versus the loss of life of power transformers.
This paper discusses the protection and controls for two parallel 400 MVA (+31.3° to –80.1°) phase-shifting transformers at a utility's 230 kV interconnection substation.
This paper describes two categories of impedance-based double-ended fault-locating methods used in transmission systems. The first category includes methods that use local measurements and remote currents. The second category includes methods that use both local and remote currents and voltages. This paper analyzes the accuracy and limitations of known time-synchronized double-ended fault-locating methods and proposes two new methods.
This paper discusses the concept of the "resiliency transformer" and its electrical and physical characteristics. It also discusses aspects related to the design of mobile relay panels, the demonstration and staging of the units, digital secondary protection systems, digital simulations, and commissioning.
This paper describes the characteristics, dependability, and security of a high-speed wireless protection sensor system and its capability for a wireless fast bus tripping scheme. It details how Blue Ridge Electric Cooperative used this technology in a substation to reduce costs by avoiding equipment replacement and field wiring changes while improving worker safety.
This paper shares an Indian utility’s field experience with ultra-high-speed protection and traveling-wave fault locating. It discusses a pilot installation of line protective relays with these capabilities and presents the performance of both protection and fault locating functions for internal faults on the pilot line.
This paper presents a case study of a microgrid control system developed, validated, tested, and commissioned for the University of California San Diego. The system provides the ability to detect and decouple during utility disturbances, operate in islanded conditions, and provide resynchronization to the grid.
Telecommunications carriers are ending support for analog leased line services and migrating users to Ethernet-based circuits. This paper presents a solution to the migration challenge based on a technology called virtual synchronous network (VSN) and describes how the utility Consumers Energy validated this solution during trials that used leased Ethernet circuits.
Georgian State Electrosystem implemented a distributed remedial action scheme (RAS) to maintain power system stability in the Republic of Georgia. This RAS was based on customized operating principles devised specifically for Georgia’s power system. This paper describes the genesis of the project, the initial requirements, the reason a distributed architecture was selected, performance indicators, and operation examples.
Typical 100 percent stator ground protection schemes face reliability challenges when applied to multiple high-impedance grounded generators that share a common bus or generator step-up winding. This paper presents a method that allows third-harmonic and injection schemes to be effectively applied in this situation and also presents two complementary methods to facilitate selectivity when protecting units that share a bus.
This paper presents how two-terminal traveling-wave fault-locating (TWFL) methods can be applied to multiterminal and hybrid lines. Laboratory test results and field events from Bonneville Power Administration are discussed to demonstrate the performance of the proposed fault-locating method.
This paper shows how to apply multiple-criteria decision analysis techniques, such as the analytic hierarchy process (AHP), to integrate world-class manufacturing principles into the circuit design process while alleviating the increased complexity of design decisions. Systematic use of AHP in circuit design increases the quality and value of designs while reducing the cost of development.
This paper presents practical solutions for testing traveling wave-based (TW-based) relays and fault locators, including a TW relay test set and relay event playback functionality. Both approaches are capable of performing end-to-end testing when an absolute time reference is used.
Magnetizing inrush creates a spurious operating current in 87T protection. Early 87T relays used harmonics for security during inrush. Today, we can design algorithms that distinguish directly between inrush and fault currents. By using the new algorithms, we improve the sensitivity and speed of 87T protection and maintain security for transformers with cores built from improved steels.
This paper compares the performance of different third-harmonic schemes and shows how these schemes can be applied to provide secure and sensitive stator winding coverage. It also provides additional guidance regarding learning algorithms and coordination with injection schemes.
This paper describes the authors’ experience in designing, installing, and testing microgrid control systems.
This paper discusses the differences between implementing cybersecurity measures in information technology (IT) and operational technology (OT) networks. It introduces software-defined networking (SDN) technology and describes how SDN can be used to build a robust and secure OT network.
This paper reviews three unique CCVT failure events and discusses relay performance during these failures.
This paper discusses an automation system consisting of intelligent electronic devices programmed to exchange information using various protocols to control, protect, and monitor the entire substation.
Keeping in mind the future need of an intelligent power management and control system (PMCS) for smart grid applications, this paper discusses proven design concepts and reliable hardware-in-the-loop testing via a real-time digital simulator. The paper presents various PMCS building blocks, including generation control systems, voltage control systems, an islanding control system, tie-line control, high-speed generation shedding and runback, high-speed load shedding based on contingency and underfrequency, and autosynchronization systems.
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 presents practical solutions for commissioning testing, including end-to-end testing, of ultra-high-speed relays that use traveling waves and incremental quantities. The paper reviews the relay operating principles and derives adequate testing requirements. It then introduces, explains, and illustrates a testing method that relies on superposition of traveling waves and low-bandwidth signals. The method uses a separate test set to generate sharp current and voltage pulses to represent traveling waves and superimposes them on the low-bandwidth signals provided by a traditional relay test set. The method uses test software to control and synchronize both test sets.
This paper presents a tested generation control system that was designed and implemented to adapt to a generation system with multiple inertias, islands, control modes, and voltage levels that will tolerate system contingencies.
This paper describes new developments in power flow regulating tap-changer control systems for phase-shifting transformers (PSTs), which are also called phase angle regulating (PAR) transformers. This paper discusses recent advancements in the control technology and highlights a particularly challenging application of two parallel PSTs installed on San Diego Gas & Electric's 230 kV transmission system.
This paper describes the design of, and the lessons learned from, a deployment of 300 smart motor control centers for a large oil and gas project in Eurasia. Arc-flash and conventional protection schemes were provided. Manufacturing, testing, and design methods are discussed.
This paper discusses the implementation of a smart grid system for a large dispersed oil field using radios as its communications network. The solution includes high-speed load shedding, online monitoring, event reporting, oscillography, and engineering access. This paper also discusses the process used to design and test the radio technology, including the evaluation of its success metrics, network security, radio path study, and optimization.
This paper describes the design, technology, model development, and overall validation of a hardware-in-the-loop simulation system for the largest oil and gas project in the world. Lessons learned and results from recent testing are shared.
This paper introduces a deterministic packet transport method of achieving guaranteed latency for critical traffic being transported over packet-based wide-area networks. The method is standard-agnostic, and it elegantly addresses the challenge of migrating time-division multiplexing-based protection circuits to Ethernet without impacting the performance of the network.
This paper discusses application considerations for communications-assisted line protective relays using five distance zones. This discussion includes how modern microprocessor-based relays can benefit the power system when properly applied to pilot protection and backup step-distance schemes.
This paper describes an event in which lightning struck a phase conductor of a 345 kV transmission line and discharged current into the phase conductor, but the magnitude of the lightning discharge was insufficient to lead to an insulation breakdown. The paper examines and explains the response of two different line current differential protective relays during such an event.
This paper demonstrates how electromagnetic torque responses can be used to measure the impact of events on a motor in a power system. The paper shows examples of calculating electromagnetic torque using oscillographic event report data obtained from digital motor protection.
This paper highlights the use of symmetrical components for simplifying the analysis of events with non-classic fault waveforms. It first provides a refresher on symmetrical component theory and then analyzes three real-world events using a symmetrical component-based event analysis approach.
This paper describes a single-ended traveling-wave-based fault-locating method that works with currents only and explains how to perform fault locating manually using ultra-high-resolution fault records from any recording device. This paper also presents laboratory test results as well as field cases in which line crews found the actual faults.
This paper compares the performance of different third-harmonic schemes and shows how these schemes can be applied to provide secure and sensitive stator winding coverage.
This paper demonstrates how to analyze faulted transmission lines using phase components (Phase A, Phase B, Phase C) as an alternative to symmetrical components (positive-sequence, negative-sequence, and zero-sequence). The paper explores both steady-state and time-domain applications, with emphasis on generating reliable test signals. Advantages of the phase-domain approach are discussed.
This paper examines various options for obtaining bus protection redundancy. The paper includes an emphasis on examining various methods of applying dual relays in an existing high-impedance bus differential CT circuit.
This paper investigates how, by using the communications and reporting capabilities of modern intelligent electronic devices, a continuously running monitoring system can quickly identify and report signal transmission timing or delivery degradation in a protection system using high-speed peer-to-peer signals.
This paper discusses high-impedance differential protection with respect to applying the scheme with mismatched-ratio CTs. The paper describes methods for accommodating mismatched CTs and reports on high-current laboratory testing of CTs. The testing was performed to assess the risk caused by overvoltage on the end terminal of a higher-ratio CT that was tapped at a lower ratio and connected to a high-impedance differential relay.
This paper reports on an experimental investigation that uses wavelength division multiplexing in high-performance power system protection applications. The investigation was performed using the latest generation of carrier-grade optical transport network (OTN) equipment. The paper documents the performance, opportunities, and pitfalls associated with this application and outlines practical strategies for the seamless integration of protection systems with the latest generation of OTN technologies.
This paper explains how microprocessor-based protective relays are used to provide both control and protection functions for small microgrids. Features described in the paper include automatic islanding, reconnection to the electric power system, dispatch of distributed generation, compliance to IEEE specifications, load shedding, volt/VAR control, and frequency and power control at the point of common coupling.
This paper discusses the design specifications and lessons learned from a project that uses computer virtualization to reduce the computing hardware needs for a modern substation.
This paper discusses the performance comparison of wireless serial and Ethernet communications and innovative wireless network topologies that maximize overall network performance during realistic field conditions. Techniques for simple and inexpensive dual primary data paths are described.
In an IEC 61850 digital substation, merging units connected to instrument transformers stream analog measurements as data packets via an Ethernet network. This paper proposes applying software-defined networking (SDN) path programming and fast failover features to achieve Sampled Values (SV) stream redundancy. The paper also discusses using SDN to manage an IEC 61850 network by logically separating station bus and process bus traffic using SDN path programming.
This paper discusses the preliminary considerations in designing a micro transactive grid that can be used as a platform to share the investment and return of distributed energy resources with a community.
In this paper, the multi-loop fault analysis method is used to determine the sensitivity and coverage provided by various generator internal-fault protection elements for interturn, interbranch, phase-to-phase, and series faults.
This paper shares the initial results and benefits that Blue Ridge Energy Cooperative has achieved by bringing intelligent electronic device oscillography from across their system together in one application.
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, we discuss an adaptive quadrilateral distance scheme that can detect greater fault resistance than a previous implementation. We also discuss application considerations for quadrilateral distance elements.
The need for low-cost technology and the sheer number of individually terminated copper conductors in traditional wiring approaches have long fostered a dream of fully digital secondary systems based on fiber-optic communications technology. This paper provides an overview of recent standards that add to the wealth of knowledge describing this technology, explains various options and the relationship among different standards, and identifies some of the future work required in this space.
Numerous digital communications protocols are used in substations to exchange process information traditionally received as low-level analog signals via copper wires from sensors and instrument transformers at the process level. In this paper, characteristics and performance are compared for IEC 61850 GOOSE and Sampled Values messaging, IEC 61158 EtherCAT, IEEE C37.118.2-2011 Synchrophasor Protocol, and Mirrored Bits® communications for their use in copper reduction and distributed communications-assisted control strategies.
This paper discusses how electromagnetic torque can be calculated from oscillographic event report data obtained from digital motor protection. Several example cases are shared.
This paper describes a single-ended traveling-wave-based fault-locating method that works with currents only and explains how to perform fault locating manually using ultra-high-resolution fault records from any recording device. This paper also presents laboratory test results as well as a field case in which the line crew found the actual fault.
This paper describes the challenges associated with protecting pumped storage hydro units. It discusses how digital protective relay schemes provide simpler and more effective protection than traditional electromechanical relay schemes.
This paper presents a new communications-based protection scheme that uses incremental-quantity and traveling wave-based directional elements to make tripping decisions in 4 to 6 milliseconds. It includes a discussion of forward and reverse fault field events that are used to analyze the performance of a permissive overreaching transfer trip scheme.
This paper describes the components of a Sampled Values system and discusses communications network engineering challenges, solutions, and tools available to provide and verify a reliable Ethernet packet transport in the process bus system. Special attention is given to the design of large substations, which need to securely merge the station bus and the process bus into a single, substation-wide network.
This paper explains principles of fault locating based on traveling waves measured only at line terminals for hybrid lines comprising overhead and cable sections. The paper introduces adaptive autoreclosing control logic to allow or cancel reclosing based on the location of the fault. The paper includes examples that explain and illustrate these principles.
This paper presents transformer protection logic for security during magnetizing inrush conditions, especially under transformer ultrasaturation resulting in low levels of even harmonics in the differential current. The protection scheme includes inrush unblocking logic to accelerate tripping for internal short circuits. The paper explains key principles, shares implementation details, and illustrates the concepts with simulation results and field cases.
This paper describes the challenges associated with protecting pumped storage hydro units and how digital protective relay schemes provide simpler and more effective protection than traditional electromechanical relay schemes.
In this paper, we use the multi-loop fault analysis method to determine the sensitivity and coverage provided by various generator internal-fault protection elements for interturn, interbranch, phase-to-phase, and series faults.
This paper discusses the advantages of the time frame capacity factor model for utilities in determining the reliability of a power system with integrated renewable energy sources.
This paper develops an error-checking method for analog-to-digital converters (ADCs) and presents test results for a commercially available ADC which indicate that the error-checking scheme is useful for detecting catastrophic data converter failures.
This paper presents an active power control system for a phase-shifting transformer based on mission priorities. The functional design, technical details, system architecture, and implementations of power controllers are discussed. A case study presents the effectiveness of the proposed controllers.
This paper discusses the installation of a rotor angle measurement system that was commissioned for San Diego Gas & Electric. This installation provides real-time monitoring and recording of generator rotor angle as well as field excitation quantities that can be applied to meet MOD-026 and MOD-027 requirements.
This paper presents a communications-based protection scheme that uses incremental-quantity and traveling-wave-based directional elements to make tripping decisions where coupling capacitor voltage transformers (CCVTs) provide voltage signals to these elements. The paper uses field events captured during forward and reverse faults to analyze the performance of the proposed permissive overreaching transfer trip (POTT) scheme, which achieves operating times on the order of 4 to 6 milliseconds.
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 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 reviews what can be achieved with a modern controlled switching device in terms of improving power quality, protecting both the power equipment and the breaker, and improving protective relay reliability.
This paper discusses the complex challenge of achieving seamless transition between grid-tied and island operation of critical facilities while highlighting fast, reliable, and adaptive protection and control solutions.
This paper describes the modeling benefits, challenges, and lessons learned associated with controller hardware-in-the-loop testing. The microgrid system used in this study has a 3 MW battery, 5 MW photovoltaic array, 4 MW diesel generator set, and 3.5 MW combined heat and power generation system.
This paper proposes a fast, secure, zero-setting adaptive algorithm to detect and declare open line conditions using wide-area synchrophasor measurements.
In an effort to move towards smart grid, the Dubai Electricity & Water Authority initiated a long-term contract for the supply, installation, testing, and commissioning of 33 substations with modern automation systems for transmission power substations. This paper discusses the system requirements and various engineering decisions that resulted from lessons learned during the system design stage to ensure that the system is ready for future smart grid requirements. Various analysis tools and testing techniques are described that were used to quantify the performance attributes of the IEC 61850-based system design.
This paper discusses a practical technique for harvesting the maximum power from a large photovoltaic system. The technique tracks the maximum power point from the nonlinear output characteristics of the PV system using an adaptive neuro-fuzzy inference system (ANFIS) to extract the maximum power from the PV system under different conditions.
This paper explains a novel data acquisition method that supports accurate, synchronized, wide-area power flow summation at fixed millisecond intervals.
This paper provides a basic explanation of time-domain protection and traveling-wave fault location principles and discusses the power system benefits gained from ultra-high-speed protection, precise and fast fault location, and megahertz sampling rates. It also discusses real-world problems solved by applying time-domain technology.
This paper discusses the fundamentals of how to perform isochronous load sharing in an islanded power system with various makes and sizes of generators (steam and gas turbines). The paper details the decentralized generation control system and also presents other topics crucial for industrial power systems.
This paper examines methods available for fault location and describes the method employed at Fayetteville PWC. It shares the results of Fayetteville PWC's pilot project and provides the information to implement their fault location system on the reader's distribution system.
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 design and testing of the first stage of a synchronism-check upgrade to the Whakamaru Power Station. The scheme allows simultaneous synchronization of up to four 11 kV generators with up to four 220 kV lines located over one kilometer apart.
This paper examines the dynamic mho expansion for positive-sequence memory polarization during a variety of different faults and changing system conditions.
This paper highlights critical parts of the COMTRADE standard and limitations to replaying event files into a relay. It also provides readers a deeper understanding of COMTRADE files and how replaying system disturbances can yield different responses in the protection elements when compared with the original event.
This paper explains practical design principles to follow for networked protection and control systems. Proven cybersecurity best practices, system architectures, monitoring methods, and defense-in-depth techniques are described.
This paper introduces the acceptance criteria for digital messages and LAN performance between data producers and data consumers that are necessary in order to exchange signals to support distributed mission-critical applications. It also compares the attributes of five popular protocols to provide information necessary for designers to understand the behavior and performance of each protocol.
This paper describes two regional system integrity protection schemes implemented in Turkey to avoid regional blackouts and the propagation of disturbances to neighboring countries.
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 explains the technical issues that have been addressed during the past decade of Sampled Values technology development and explains how these issues are resolved with the use of software-defined networking for process local-area network packet switching and fault recovery. It also introduces the correlation between accessible electricity and economic improvements, and it discusses the importance of low installation costs, low lifecycle costs, and high availability and resistance for added or expanded power systems.
This paper analyzes the Sampled Value process bus concepts that have recently been updated by various IEC working groups. The authors are engineers with over a decade of participation in developing the IEC communications standards.
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 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 summarizes the Ethernet packet performance time definitions in IEC 61850 Edition 1 and the new IEC 61850 Edition 2 time classes, introduces subscribing device features required to confirm proper packet exchange, and illustrates case study examples of in-service local-area network (LAN) failures.
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 explains how commercial, off-the-shelf protective relays can be used to automatically island microgrids and to then automatically reconnect them to the macrogrid.
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 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 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 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 introduces new ideas and concepts that complement existing generator protection elements to provide better overall generator protection and monitoring.
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 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 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 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 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 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 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 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 discusses improvements to out-of-step protection. These improvements provide adaptive protection based on dynamical system energy balance to more effectively detect potential out-of-step conditions and provide more flexible corrective actions. This method also provides additional robustness by compensating for uncertainties in system parameters.
This paper presents a centralized microgrid control system for effective operation of wind turbines and diesel engines coupled to a flywheel electrical storage component on Saint Paul Island. The wind turbines have sufficient capacity to support the entire island without using the diesel engines, allowing the formation of an islanded power system completely powered by renewables. The control system was tested using hardware-in-the-loop simulation with a simplified electrical model of the Saint Paul system.
This paper discusses what happens when a microgrid control system fails and quantitatively evaluates the impact on microgrid reliability.
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 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 provides a clear set of procedures and equations to follow in optimal current transformer selection for low-voltage motor control centers.
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 explains a novel data acquisition method that supports accurate, synchronized, wide-area power flow summation at fixed millisecond intervals.
This paper summarizes the successful addition of a remedial action scheme to an in-service emergency control system in the country of Georgia.
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 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.
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 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 analyzes the voltage sags that occurred during a simulated transformer energization study for an offshore platform.
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 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 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.
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 is an introduction to the deployment of a network intrusion detection system for industrial control systems.
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 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.
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 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 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 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 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 explains modern nanosecond precision time technologies and new applications they enable.
Ultra-high-speed line protection is becoming a reality today, giving the industry a way to trip line faults in a few milliseconds. One relay described in this paper that uses time-domain principles incorporates incremental-quantity (TD32) and traveling-wave (TW32) directional elements in a communications-assisted tripping scheme, incremental-quantity distance element (TD21), and traveling-wave differential element (TW87). This paper introduces these time-domain line protection elements, shares key details of their implementation in hardware, and illustrates their operation using real-world faults and digital simulations. By comparing the performance of the time-domain line protection elements with the traditional phasor-based elements of the in-service relays that captured the fault records, we demonstrate the performance of the time-domain line
protection elements.
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 discusses a novel single-end traveling-wave-based fault location (TWFL) method that uses current traveling waves to identify reflections from the fault, the remote end, and any discontinuity on the transmission line. The TWFL estimation results are validated with actual line patrol findings.
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 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 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 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 discusses the implementation of a fast motor bus transfer scheme using existing protective relays. The scheme is designed to respond to local and remote (upstream) events in the substation. This makes possible an attempt to initiate a fast transfer for events that are remote to the motor bus. On a failure to achieve a fast transfer, the scheme resorts to an in-phase transfer and, if that fails, finally a residual transfer. Real-time dynamic modeling was performed to simulate motor bus decay and reacceleration. This paper provides the results of the simulations and the response of the transfer scheme.
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 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 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 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.
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 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.
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 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 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 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 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 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 briefly explains the principle of ground fault detection in an ungrounded power system and the challenges of locating the actual faulted feeder on the LADWP distribution system at present. We then discuss a new innovative algorithm developed to correctly identify the faulted feeder on the LADWP distribution system. We validated this algorithm by means of laboratory and staged-fault field testing.
This paper reviews new time-domain line protection operating principles using traveling waves and incremental quantities. We discuss operating principles of novel directional and differential elements based on traveling waves and Zone 1 distance and directional elements based on incremental quantities. This paper provides details on the actual implementation of these principles in a high-performance relay platform and shares performance results from simulations and field recordings.
This paper presents a novel approach to frequency estimation for power system applications: frequency tracking, frequency protection, and synchrophasors. We based our algorithm on autocorrelation of the waveform or correlation of the waveform and its derivative using a freely chosen window length. Because of the averaging inherent in correlation, the method has exceptional immunity to noise. We derive, explain, and illustrate the new method with simulation results. We review advantages and attributes of the new method compared with two commonly used approaches to frequency measurement: timing between the waveform zero crossings and measuring the rate of rotation of a phasor.
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 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 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 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 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 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 studies the failures of substation automation systems (SASs) and proposes an all-inclusive categorization of failures that are likely to endanger the correct operation of a power system. Understanding different failure modes can contribute to the development of a model to evaluate the combined SAS and power network in a unique framework.
This paper compares the mechanisms for quickly reconfiguring Ethernet networks to satisfy mission-critical performance metrics while providing simultaneous duplicate or redundant signal exchange. This paper also compares the attributes and complexities of duplication methods and redundancy methods that are available in software-defined networking (SDN) to 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 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.