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.
Industrial control system (ICS) owners and operators are increasingly requesting the implementation of cryptographic protocols into critical energy system devices for securing data-in-motion against common threat scenarios. We argue that IEEE 802.1AE Media Access Control Security (MACsec) is the security solution for critical local-area networks (LANs) due to attractive qualities such as simplicity of design and use, and low maintenance requirements. Further, we demonstrate that MACsec may be combined with other cryptographic protocols into a complete secure transport solution for LANs and routed networks.
This paper discusses power-system-related events that occurred from commissioning to after handover in a 110, 35, 10, 6, and 0.38 kV power generation, transmission, and distribution system. Some events involve a single relay; others include complex schemes involving multiple electronic devices, communication protocols, and their impact on overall power system performance. The paper describes the root-cause investigation for each event, as well as the solutions that the engineering team applied.
In this paper, we analyze notable field events recorded during open-phase tests at solar facilities. These events reveal system overvoltages and excessive harmonics at several sites. To address these concerns, we use field events to demonstrate the effectiveness of voltage-based detection schemes. These schemes consider the total harmonic distortion of the phase voltages and a zero-sequence overvoltage element.
This paper provides guidance on setting impedance-based directional thresholds as well as the overcurrent elements that supervise the directional elements. The paper discusses biassing directional thresholds towards security, dependability, or an equal balance between security and dependability.
This paper provides a step-by-step guide to comply with NERC PRC-027-1 by exploring the following areas: an introduction and purpose of the standard, a systematic approach to developing processes and protection settings, common and unique coordination challenges, and methods to automate repetitive tasks. Furthermore, the process put forth in this paper was used as the basis of the PRC-027-1 compliance program for the Metropolitan Water District of Southern California (MWD). Real-world challenges associated with this process from an end-user point of view are also discussed.
A case study in planning, designing, developing, testing, and validating a microgrid control system (MCS) for a university campus consisting of two buildings supplied by one utility feed. Each building contains a battery energy storage system (BESS), a photovoltaic (PV) rooftop installation, a building energy management system (BEMS) with optimization capability, as well as existing protection, control and visualization systems.
This paper presents the main challenges found during power system studies for the Panama transmission system and provides remedial action solutions implemented using modern technologies and wide-area, high-speed communications.
In this paper, we revisit and update the original paper, “Assessing the Effectiveness of Self-Tests and Other Monitoring Means in Protective Relays,” using field data and expanding the system model to consider improved mean time between failures (MTBF), variances in hardware designs, and the impact of firmware updates in assessing the effectiveness of relay self-testing. Finally, we describe and evaluate four practical levels of detecting the health of a protective relay. These are real-time monitoring of relay self-test alarms, continuous monitoring of communications and analog inputs, performing visual inspections, and lastly, identifying failures that are not detectable without a manual test. By using data and targeted approaches, protective relay users can know and improve relay availability, reduce failures, and optimize protection system testing intervals.
This paper shows how to use event report data to locate DLG faults with several different nonstandard configurations. The paper shows how to analyze these DLG faults by solving voltage loop equations written in the phase domain, using A, B, and C components rather than symmetrical components. The paper demonstrates the applicability of these techniques to a real-world fault.
This paper presents a novel, synchrophasor-measurement-based algorithm that can detect faulty VT circuits weeks before failure, indicate which phase is failing, and provide alarms to power system operators in near-real time. The results from tests of the algorithm using field-measured synchrophasor data are also presented in the paper.
The paper describes a bus protection application for a 1,500 MVA nuclear power plant with external fault current levels exceeding 300 kA. The CTs were inside the generator step-up (GSU) delta winding which challenged bus protection application. This paper talks about the EMT modeling and the hardware-in-the-loop (HIL) testing performed to test the differential element security for external faults, dependability for internal faults, and alarming for a CT failure condition.
This paper introduces distance elements suitable for protecting lines near wind-turbine generators and inverter-based sources. The paper includes application recommendations for the directly tripping underreaching distance elements (Zone 1), the instantaneous overreaching distance elements in pilot protection schemes (Zone 2), and the step distance protection elements.
This paper introduces the use of inverse-time undervoltage and inverse-time overvoltage characteristics in point of common coupling (PCC) protection schemes as a means of detecting distribution feeder faults and determining whether the associated distributed energy resource (DER) should be isolated from the feeder. A method for coordinating inverse-time voltage characteristics at the PCC with inverse-time overcurrent characteristics of other protective devices on the distribution system is also provided.
The Lone Star Transmission, LLC 345 kV transmission corridor comprises two series-compensated lines: 224.9 mi and 189.6 mi. These lines share the same series-compensation sites and include shunt reactors at one of the capacitor locations. Hence, the protection is complex, and accurately locating faults can be difficult with phasor-based impedance and line current differential protection. This paper discusses a system-based testing approach for verifying the performance of ultra-high-speed (UHS) line protective relays. It explains a simulation testing software model and the variety of operational scenarios simulated to improve Lone Star’s protection philosophy for these series-compensated transmission lines in the future. The paper includes the results from these tests, the related optimization of the UHS relay settings, and an evaluation of the UHS-based protection scheme field experience performance for three events.
This paper describes a method to estimate transmission line parameters in traveling-wave (TW) relays. The proposed method uses time-synchronized voltage and current measurements from both ends of a line and TW fault location data available in the event report. Positive-sequence line impedance (Z1) is estimated using prefault positive-sequence quantities. Incremental zero-sequence quantities and TW fault location data are used for zero-sequence line impedance (Z0) estimation. The use of incremental quantities provides better Z0 estimates for both transposed and untransposed lines. Line parameter estimates from both simulation and field events demonstrate the robustness of the proposed method.
This paper shows how distance elements can be combined with the double-ended traveling-wave fault location method to make reclosing decisions on simple hybrid lines.
This paper investigates methods to measure the speed and performance of digital trip circuits and provides speed comparisons for multiple trip circuit technologies. It also offers guidance, resources, and standards to implement digital trip circuits in protection systems.
This paper describes a new synchronous generator model that was developed in a Real-Time Digital Simulator (RTDS). The paper discusses how the model was used to validate a new generator relay. Considerations for the dependable application of stator ground protection, the differential element, split-phase protection, and the negative-sequence directional element for different generator faults including ground faults, phase faults, turn-to-turn faults, and series faults, are provided.
Fault location, isolation, and service restoration (FLISR) technologies improve the reliability of the distribution grid, and hence, the control algorithm, communications network, and device settings for the FLISR system should be thoroughly assessed. This paper details contingencies that should be tested for a new FLISR system using an example hardware-in-the-loop (HIL) system with recloser controls connected to a centralized FLISR system and a mesh radio communication network. It explains methods to obtain expected restoration times for the example system, report the results for the example system, and analyze those results.
This paper focuses on a new, resilient approach to time synchronization using time distribution over the wide-area network (WAN)) using Precision Time Protocol (PTP). This solution uses the concept of a time distribution gateway that is able to receive network time either via PTP telecom profile, via GPS directly, or through IRIG-B from a local GPS time source to then provide a submicrosecond timing reference for critical substation applications.
This paper introduces a method for distinguishing between open-phase, element fault, and system unbalance conditions for distribution poletop capacitor banks. It also establishes a method for identifying the open or faulted phase to assist in timely maintenance.
This paper discusses the issue of coordination of resistive reach of phase and ground distance elements used for transmission line protection. It addresses the considerations and benefits of coordinating this aspect of distance elements considering possible fault resistance.
This paper discusses the impact of inverter-based resources (IBRs) in traditional digital protection relays applied in the interconnection transmission line between the IBR and bulk power system and discusses how to properly handle this kind of source by presenting modern protective relays features, time-domain functions, and special settings for traditional protection intelligent electronic devices (IEDs).
This paper discusses the concepts, design, benefits, and deployment of a traveling-wave fault locating (TWFL) system for a 500/230 kV transmission system in Brazil with line lengths ranging from 158 to 355 km (98 to 221 mi). It also discusses the concepts of different fault-locating methods.
This paper discusses how Red Eléctrica de España, the transmission system operator in Spain, successfully applied double-ended traveling-wave-based fault locating (DETWFL) on a pilot project where relay-to-relay communications were unavailable. The paper describes the offline DETWFL method and includes an analysis of a B-phase-to-ground fault on a transmission line to illustrate the performance of this method. It provides a summary of results from five faults that occurred on this line while relay-to-relay communications were unavailable. These results highlight the improved accuracy of the offline DETWFL method as compared to the single-ended impedance-based and single-ended traveling-wave-based methods.
This paper reviews the fundamentals of CT and VT connections. It discusses several basic and advanced testing and commissioning approaches that can help find common wiring errors and improve protection. The paper describes several actual field events of undesired or unexpected relay performance due to improper CT or VT circuit connections, setting or drawing errors, and details on how testing and commissioning checks would have prevented these events from happening.
This paper discusses methods to test and verify transformer differential protection systems. It covers using metering and recordings to verify that current transformer circuits and compensation for magnitude, phase shift, and zero sequence are correct, as well as methods to troubleshoot problems when they are not correct. A new comprehensive differential metering report that simplifies the task is introduced.
This paper discusses PNM’s EHV transmission line protection standard and its application to more than six 345 kV transmission lines on which PNM has successfully installed this new line protection.
This paper introduces several of the necessary test processes and performance metrics sufficient for an IEC 61850-9-2 process bus-based protection system installation. Also discussed are the lessons learned from commissioning a process bus-based distributed busbar protection system.
The metric introduced in this paper, threat availability, is used to measure and contrast the potential success of a cyberattack or mitigation control.
This paper introduces distance elements suitable for protecting lines near wind-turbine generators and inverter-based sources. The paper begins by analyzing issues with distance elements that use memory polarization for directionality and negative-sequence current for faulted-loop selection and reactance comparator polarization. The analysis is based on worst-case assumptions derived from field cases and published findings, it avoids modeling by using proprietary and uncertain information about the sources, and it does not assume that the source fault response complies with any local, international, present, or pending interconnection standards. The paper identifies parts of the distance element logic that do not work well in applications near unconventional sources and replaces the problematic parts with alternatives that perform satisfactorily. The solution is based on an offset distance characteristic to avoid memory polarization. It further uses separate directional elements to directionalize the offset distance elements by taking advantage of the system fault current contribution rather than the source current contribution. This paper is an abbreviated version of the SEL technical paper, "Distance Elements for Line Protection Applications Near Unconventional Sources."
This paper introduces a novel protection principle for lines connected to the bulk power system at one end (system terminal) and terminated exclusively on power transformers or current-limiting reactors at the other end (transformer terminal). The new protection principle operates as fast as 1 to 2 ms and covers the entire line length without the need for a protection channel. The new principle is based on the current traveling-wave magnitude measured at the system terminal of the line. This paper is an abbreviated version of the SEL technical paper, "Traveling-Wave Overcurrent – A New Way to Protect Lines Terminated on Transformers."
This paper discusses the infrastructure and performance differences controlling inverter generation with synchrophasor data vs. traditional SCADA protocols like DNP3 or Modbus.
This paper presents a method for evaluating the loadability of incremental-quantity distance (TD21) protection elements. Responding to changes in voltages and currents, the TD21 elements are not impacted by heavy load or power swings. However, switching operations that result in sudden changes in load, including both load pickup and load rejection, may impact security of the TD21 elements. Traditional methods of evaluating protection element loadability do not apply to incremental quantity-based protection elements and schemes. This paper closes the gap by introducing a simple and practical method of evaluating TD21 loadability. The paper provides a short overview of the key TD21 design details and describes a TD21 loadability evaluation method.
This paper describes a case study, performed with the University of North Carolina at Charlotte and a local utility company, that comparatively evaluates the cost, reliability, and performance of substation protection and control design between traditional substation architecture and two process bus solutions (P2P- and IEC 61850-based).
This paper provides details about the experience NamPower—the national power utility in Namibia—had with ultra-high-speed (UHS) protection and traveling-wave fault locating (TWFL) while UHS relays were installed to monitor a 220 kV transmission line. It provides the analysis of a C-phase-to-ground fault on the line, discusses observations made from the event records, and relates the concepts of UHS protection and TWFL with the event data. It presents the performance of the protection elements, fault locating, and transient recording capabilities of the UHS relays. The paper compares the observed fault-clearing time of the phasor-based relays to the expected fault-clearing time with UHS relays installed on the line. It also relates fault-clearing time to the concept of critical clearing time and highlights the potential increase in critical clearing time margin when using UHS relays for fault clearing to benefit system transient stability. Additional observations from 1 MHz transient records, such as post-fault arcing and breaker reignition, are discussed, which can aid with asset management and preventive maintenance.
This paper focuses on the islanded operation of a utility distribution system energized from a BESS and PV inverters. Grid forming with droop control (GFMD) BESS inverters are used to provide resiliency. The protective relaying scheme recognizes the islanded state and communicates the new mode of operation to downstream reclosers by a frequency shift to enable adequate sensitive overcurrent elements and appropriate underfrequency load-shedding thresholds.
This paper reviews applicable standards and references, and describes the reasons for installing various protective elements at the utility-industrial interface.
With the goal of modernizing its line protection technology and the need for system-wide consistency, Public Service Company of New Mexico (PNM) standardized their extra-high-voltage (EHV) transmission line protection to include ultra-high-speed (UHS) line relays. The standardization allowed PNM to create a new line protection philosophy that allows single-pole tripping and reclosing, a new panel design, and an updated breaker failure scheme. The new protection standard employs best-known practices and innovative methods for designing, testing, and commissioning a protection system using UHS relays. This paper discusses the PNM EHV transmission line protection standard and the application of the standard to more than six 345 kV transmission lines on which PNM has successfully installed this new line protection. The paper also discusses the validation testing of the protection scheme using hardware-in-the-loop simulation with a real-time digital simulator (RTDS). Onsite commissioning, end-to-end testing, and lessons learned are also discussed.
In this paper, the authors share their experience and best practices in applying HIL techniques for the petrochemical industry. The paper discusses best practices for constructing and validating models, connecting hardware to simulators, and running an effective HIL factory acceptance test. The authors highlight several in-service petrochemical projects that used HIL simulations and benefited from the resulting cost reduction and risk mitigation.
This paper introduces a novel protection principle for lines terminated exclusively on power transformers and current-limiting reactors: the traveling-wave overcurrent (TW50) element. This element operates in as fast as 1 to 2 ms and covers the entire line length without the need for a protection channel. The paper illustrates this protection principle with several field cases and provides application recommendations and the expected TW50 dependability for line faults.
This paper is a comprehensive review of setting considerations for distance elements in line protection applications and discusses the following:
This paper discusses the Power Management System (PMS) provided for a remote facility that is situated above the arctic circle and does not have any utility connection. The PMS includes high-speed load-shedding, automatic generation control for frequency management, unique reactor control for limiting current (amperes), and VFD control for voltage stability, reactive load sharing, and automatic synchronization of different electrical islands. This paper also discusses control hardware-in-the-loop (c-HIL) testing using a real-time transient-level computer model of the power system which was used for functional testing of the PMS including protection and automation prior to field deployment.
This paper discusses the updates to the generation-dropping Jim Bridger RAS algorithm to integrate additional wind generation assets with existing coal-fired generation. The updates to the RAS algorithm include monitoring the new 500 kV transmission line and wind generation assets and using new criteria for selecting a combination of thermal and wind generation for tripping and new unit-selection logic.
This sequel to the original “Beyond the Cookbook” paper continues to discuss the challenges encountered when creating line relay setting calculations and how to apply practical solutions outside of cookbook guidelines. This sequel also expands upon subjects that are only touched on in the original paper; for example, line current differential (87L) protection, three-terminal line protection, accounting for a high source impedance ratio (SIR), switch-onto-fault (SOTF) protection, and more.
In this paper, we provide application guidance to set conventional line protection schemes reliably in systems with inverter-based resources (IBRs). The guidance is based on a study performed as part of a collaborative effort by NERC, Sandia National Laboratories, four IBR manufacturers, and two relay manufacturers. The IBR manufacturers provided “real-code” models for their Type 3 Wind, Type 4 Wind, and PV Solar, which were used in PSCAD simulations and subsequently played back through relay hardware. The paper shares relay oscillography to explain the challenges and solutions.
This paper describes a novel maintenance mode for IEC 61850-based DSS IEDs to keep protection functions enabled during maintenance. It describes in detail how the maintenance mode can be implemented using the IEC 61850 standards.
This paper shares NamPower’s field experience with ultra-high-speed protection and traveling-wave fault locating on a 220 kV line. It discusses observations made from transient event records captured during a C-phase-to-ground fault on the line. It presents the performance of protection elements, fault locating, and transient recording capabilities, which have the potential to benefit system stability and aid with preventive maintenance of assets.
This paper analyzes the impacts of time synchronization and network issues on protection functions for an IEC 61850-based DSS. Test cases that demonstrate disabling of protection functions due to loss of a time source and a delay in protection function operation during network congestion are presented.
This paper compares the performance of two protection systems by measuring the same analog quantities. One system takes measurements through direct wiring, and the other receives information over Ethernet using the IEC 61850 Sampled Values protocol. The tests use a real‐time digital simulator responsible for generating the analog quantities of the faults and measuring the response time of both systems by closing their respective digital contacts and consequently opening the circuit breakers.
This paper discusses how a transmission system operator in Spain successfully applied double-ended traveling-wave-based fault locating (DETWFL) offline when relay-to-relay communications were unavailable. It also discusses the possibility of using DNP3 over Ethernet to retrieve event information, allowing for automatic DETWFL calculations offline. Finally, it includes the analysis of a B-phase-to-ground fault to illustrate the performance of the applied offline DETWFL method.
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 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 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 analyzes the impact of line length, fault location, and locations of external and internal discontinuities on traveling-wave (TW) protection and fault-locating functions. The paper explains the underlying principles and derives a method to calculate the minimum line length that yields an expected level of accuracy and dependability. The paper serves as a tutorial on propagation and timing of TWs and is of interest to those practitioners who evaluate, test, apply, and troubleshoot TW-based devices.
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 reasons why many security techniques commonly applied in IT systems and based on cryptography may
be unsuitable for application in critical portions of energy systems. It proposes for system owners an approach to designing energy systems that separates system elements into those that are dynamic and static, and it builds on that approach with recommendations for OT cryptographic security controls in energy system networks.
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.
Modern digital secondary system technology uses digital communications among relays and remote digital sensors over high-speed fiber connections to perform fault detection and trip circuit control. A cyber vulnerability assessment of each proposed communications design is essential to evaluate the energy control system’s reliability. Many cybersecurity technologies from numerous industries are promoted for use in DSS communications with unknown impacts. This paper introduces appropriate metrics and a cyber vulnerability assessment framework, using the attack tree method, to compare the cyber risk of available technologies to determine the dependability and security of digital control and protective trip circuits.
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.
This paper explains the challenges of measuring line current accurately at dual-breaker terminals and the impact on line protection. It then discusses solutions to improve relay security at dual-breaker terminals.
This paper proposes a new rate-of-change-of-frequency scheme that allows for fast underfrequency load shedding to minimize frequency excursions. It also presents simulations showing that the scheme is secure from misoperations for source transmission line operations.
Three-terminal transmission lines pose protection challenges not encountered with more familiar two-terminal lines. A three-terminal line in Oncor Electric Delivery’s power system is considered in this paper. Different topologies and contingencies affect infeed and outfeed levels, requiring careful selection of protection element settings and directional element polarizing quantities. Lessons learned are generalized so they may be applied to optimize security and dependability in any three-terminal line application.
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 logic, 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 multibit digital protection channel.
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.
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 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 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.
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 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 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 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 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 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 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 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.
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 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.
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.
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.