Showing papers on "Power-system protection published in 1995"
TL;DR: A new approach to fault classification for high speed protective relaying based on the use of neural network architecture and implementation of digital signal processing concepts is presented and its effectiveness in computer simulations on parallel transmission lines is shown.
Abstract: This paper presents a new approach to fault classification for high speed protective relaying and show its effectiveness in computer simulations on parallel transmission lines. The scheme is based on the use of neural network architecture and implementation of digital signal processing concepts. We begin by classifying several fault types like 1-phase-to-ground, 2-phase-to-ground and 3-phase-to-ground faults. We proceed with classification of arcing and nonarcing faults in order to obtain a successful automatic reclosing. Encouraging results are shown and indicate that this approach can be used for supporting a new generation of very high speed protective relaying systems. >
286 citations
05 Apr 1995
TL;DR: Details on the design, architectural features and applications of a real-time digital simulator (RTDSm) developed at the Manitoba HVDC Research Centre (Winnipeg, Canada) are presented.
Abstract: Abstruct - This paper presents details on the design, architectural features and applications of a real-time digital simulator (RTDSm) developed at the Manitoba HVDC Research Centre (Winnipeg, Canada). Custom hardware and software have been developed and collectively applied to the simulation and study of electromagnetic transients phenomenon in power systems in real-time. The combination of real-time operation, flexible YO, graphical user interface and an extensive library of accurate power system component models make the RTDS an ideal simulation tool with a wide range of applications. I. INTRODUCTION Simulation has long been recognized as an important and necessary step in the development, design and testing of power generation and transmission systems. A wide variety of both analogue and digital simulation tools are available and typically used during various stages of system development. Recent advances in both computing hardware and sophisticated power system component modelling techniques have significantly increased the application of digital simulation in the power system industry. Of particular interest in the context of this paper are the advances made in the study of electromagnetic transients phenomenon.
233 citations
TL;DR: A fault direction discriminator that uses an artificial neural network (ANN) for protecting transmission lines and is suitable for realizing an ultrafast directional comparison protection of transmission lines is described.
Abstract: This paper describes a fault direction discriminator that uses an artificial neural network (ANN) for protecting transmission lines. The discriminator uses various attributes to reach a decision and tends to emulate the conventional pattern classification problem. An equation of the boundary describing the classification is embedded in the multilayer feedforward neural network (MFNN) by training through the use of an appropriate learning algorithm and suitable training data. The discriminator uses instantaneous values of the line voltages and line currents to make decisions. Results showing the performance of the ANN-based discriminator are presented in the paper and indicate that it is fast, robust and accurate. It is suitable for realizing an ultrafast directional comparison protection of transmission lines. >
198 citations
Book•
30 Jun 1995
TL;DR: The text covers the mathematical basis of numerical techniques and relay algorithms, the basic elements of digital protection and the fundamentals underlying the commonest algorithmic forms, particularly as applied to line protection.
Abstract: Digital protection is based on the use of computers in power line relaying. Since the late 1960s, digital devices and techniques have been applied to almost all new protection schemes. Today the technology is moving towards standardised hardware platforms; at the software level, however, there remains a huge variety in approaches and protection algorithms. This book gives a fairly detailed understanding of the principles and techniques underlying the application of digital technology and algorithms to protection. It avoids going into detail of specific products: up-to-date information on these is available from the manufacturers. Instead it aims to give the reader a thorough understanding of the generic problems of digital protection. The text covers the mathematical basis of numerical techniques and relay algorithms, the basic elements of digital protection and the fundamentals underlying the commonest algorithmic forms, particularly as applied to line protection. It deals with the fundamentals of travelling-wave techniques and their application to transmission lines, and with digital differential protection of transformers and lines.
178 citations
TL;DR: A multi-criteria algorithm is developed based on fuzzy sets for the decision making part of the scheme and can enhance the sensitivity and selectivity of the digital relay and mitigate problems associated with conventional relay schemes.
Abstract: This paper presents a digital relay scheme for the primary protection of power transformers. A multi-criteria algorithm is developed based on fuzzy sets for the decision making part of the scheme. The cost of wrong decision-making and the amount of information inflow are used along with several standard criteria to improve the reliability of the protection. It is shown that the proposed scheme, if properly tuned, can enhance the sensitivity and selectivity of the digital relay and mitigate problems associated with conventional relay schemes. >
153 citations
TL;DR: In this article, a numerical algorithm for power transmission network arcing faults detection has been developed, where important features of a long arc in air are investigated and used as a basis in the algorithm design.
Abstract: To avoid automatic reclosing on permanent faults, a new numerical algorithm for power transmission network arcing faults detection has been developed. Some important features of a long arc in air are investigated and used as a basis in the algorithm design. The fact that the nonlinear arc behavior influences other voltages and currents distorting them, offered an opportunity to detect the arc by measuring and processing the transmission line terminal voltage and current. A series of simulation studies have shown that the algorithm can be used as an effective tool for arcing faults detection. >
149 citations
TL;DR: One of the algorithms, called the SMIRA algorithm, has an outage probability that is very close to the minimum and a class of distributed power control algorithms that can achieve a balanced carrier-to-interference ratio with probability one are studied.
Abstract: Power control is an effective technique to reduce cochannel interference and increase capacity for cellular radio systems. Optimum centralized power control can minimize the outage probability, but requires the information of all link gains in real time, which is very difficult to successfully implement for a large system; besides, the computational complexity of an optimum power control algorithm makes it impractical for real implementations. In this paper, we propose some centralized power control algorithms with reasonable computational com- plexity. One of the algorithms, called the SMIRA algorithm, has an outage probability that is very close to the minimum. We also study a class of distributed power control algorithms that can achieve a balanced carrier-to-interference ratio with probability one. Among the class of algorithms, we found that the one proposed in (6) gives the minimum outage probability.
126 citations
TL;DR: In this paper, a new islanding protection algorithm described in the paper has been developed to be part of an integrated protection package to cover all the protection requirements of a DSG.
Abstract: The ability to detect when dispersed storage and generation (DSG) units become islanded from the main source of generation enables the DSG to be quickly disconnected from the utility network and for that network to be rebuilt in a safe and orderly manner. The new islanding protection algorithm described in the paper has been developed to be part of an integrated protection package to cover all the protection requirements of a DSG. A selection of the results obtained from extensive laboratory and field tests are presented and show that the algorithm reliably trips for islanding conditions within 120 milliseconds, trips for load fluctuations should the DSG be operating independent of the main source of supply and restrains for single phase faults close to the DSG. >
115 citations
TL;DR: In this paper, a new approach for real-time short circuit analysis of radial and weakly meshed distribution networks is proposed, which works based on a well documented radial power flow study method, and uses a hybrid compensation method to account for loops, PV nodes, and fault currents simultaneously.
Abstract: This paper addresses a new approach for real-time short circuit analysis of radial and weakly meshed distribution networks. The approach works based on a well documented radial power flow study method, and uses a hybrid compensation method to account for loops, PV nodes, and fault currents simultaneously. The three-phase short circuit analysis, in its actual a-b-c phase representation, can be applied to balanced or unbalanced distribution systems. A distribution short circuit program which is developed based on this approach, is integrated with a three-phase power flow program to solve various types of single or simultaneous faults, including single-line to ground, three-line to ground, double-line to ground, line-to-line, and double three-line to ground faults. Results of the application of this approach to large-scale distribution networks are also reported in this paper.
115 citations
TL;DR: In this paper, the variations of Prony's parameters in terms of some of the power systems characteristics (distance between the busbar and the fault, fault resistance and capacitive current of the whole network) are presented.
Abstract: Prony's method is a technique for estimating the modal components present in a signal. Every modal component is defined by four parameters frequency, magnitude, phase, and damping. This method is used to analyse earth fault currents in Petersen-coil-protected 20 kV networks. The variations of Prony's parameters in terms of some of the power systems characteristics (distance between the busbar and the fault, fault resistance and capacitive current of the whole network) are presented. It is shown that some of the Prony's parameters relating to the fault current transient may be useful to determine what kind of fault occurred, and where it occurred. >
108 citations
TL;DR: In this article, the authors present a power swing blocking principle that has the ability to immediately clear the block when a fault occurs within the relay trip zone, which is demonstrated for extremely fast power swings.
Abstract: Any sudden change in the configuration or the loading of an electrical network causes power swings between the load concentrations of that network. In order to prevent the distance protection from tripping during such conditions, a power swing blocking device is often utilized. Conventional power swing blocking devices cannot cope with very fast power swings of up to 5 Hz/sec. This paper presents a new power swing blocking principle that has the ability to immediately clear the block when a fault occurs within the relay trip zone. This is demonstrated for extremely fast swings (greater than 5 Hz/sec) and even for two phase operation (during single pole tripping). This new principle is in a form which can be implemented on an existing digital distance protection relay. Results are presented based on extensive simulation studies carried out on a typical 400 kV system, using the Electromagnetic Transient Program (EMTP) software. >
TL;DR: In this article, the authors proposed a two-stage process to find a suboptimal solution by analyzing the mesh distribution system in which all open switches are simulated to be closed and a radial distribution system is determined as an intermediate solution.
Abstract: Feeder reconfiguration for use by distribution management systems is discussed in this paper. Multiple objectives are proposed to reflect realistic operating environments while achieving all benefits from feeder reconfiguration. The multiple objectives considered are minimization of power losses, load balancing among supply transformers, minimization of the worst voltage drop, minimization of service interruption frequency, and balanced service of important customers for enhanced service reliability. The objective function containing five different objectives are optimized subject to capacity and protection device constraints. The overall solution approach is a two-stage process. In the first stage, a suboptimal solution is found by analyzing the mesh distribution system in which all open switches are simulated to be closed. Applying special power flow analyses to this mesh network, a radial distribution system is determined as an intermediate solution. In the second stage, this solution is continuously improved by the branch exchange scheme. Special topology models are also developed to accelerate the search procedure. Use of the algorithm is illustrated by numerical examples.
Book•
01 Jan 1995
TL;DR: Fundementals of protection engineering: the principal faults on electrical power systems and system components the main criteria for detecting faults instrument transformers for protection purposes.
Abstract: Fundementals of protection engineering: the principal faults on electrical power systems and system components the main criteria for detecting faults instrument transformers for protection purposes. Analogue protection: solid state protection relays and systems application of analogue protection devices analogue protection for power systems analogue protection for machines. Digital protection: computer-based protection and control A/D conversion of input variables digital signal conditioning algorithms for digital protection logical structures for digital protection. Appendices: symbols characteristics of standard low-pass filters.
TL;DR: In this article, the authors developed an HVDC transmission line protection method based on a new working principle that allows high-speed and highly sensitive detection of faults, enhancing reliability in the supply of electric power.
Abstract: For the third project of the Hokkaido-Honshu HVDC Link in Japan, called the HVDC Link III project (rated at 250 kVDC-1200 A-300 MW), we developed an HVDC transmission line protection method based on a new working principle that allows high-speed and highly sensitive detection of faults, enhancing reliability in the supply of electric power. In general, increasing the sensitivity of relays will lead to an increased likelihood of undesired operation whereas lowering the sensitivity will impair the responsiveness of the relays. Our proposed method meets these apparently incompatible requirements very well. Basically classified as a differential scheme, the HVDC transmission line protection method compensates for a charging and discharging current that flows through the line-to-ground capacitance at times of voltage variations caused by a line fault or by the operation of DC power systems. The developed protection method is also characterized in that it uses current changes induced by voltage variations to restrain the operation of a relay. This configuration has made the proposed method far superior in responsiveness and sensitivity to the conventional protection method. A simulation using an EMTP (Electro-Magnetic Transients Program) was conducted on this method. Developed relay equipment embodying the new protection method was subjected to various verification tests, where this equipment was connected to a power system simulator, before being delivered to the HVDC Link III facility. >
TL;DR: In this paper, the authors present a summary of "System Protection and Voltage Stability", a special publication prepared by Protection Aids to Voltage Stability Working Group of the Substation Protection Subcommittee of the IEEE Power System Relaying Committee.
Abstract: This paper is a summary of "System Protection and Voltage Stability", a special publication prepared by Protection Aids to Voltage Stability Working Group of the Substation Protection Subcommittee of the IEEE Power System Relaying Committee. This summary describes the risk and mechanism of voltage collapse and suggests some operating, system upgrades, and protection solutions. Various undervoltage load shedding schemes are discussed, including actual or planned installations. >
TL;DR: This fault diagnosis expert system installed at the Tohoku Electric Power Company aims for improved practicability by using time-tagged data from circuit breakers, protective relays, and automatic reclosing relays in addition to the input data used in earlier systems.
Abstract: This paper describes a fault diagnosis expert system installed at the Tohoku Electric Power Company. The main features of this system are careful selection of the inferencing input data, rapid inferencing, integration of the expert system with other systems in a practical structure, and the adoption of a domain shell. This system aims for improved practicability by using time-tagged data from circuit breakers, protective relays, and automatic reclosing relays in addition to the input data used in earlier systems. Furthermore, this system also uses data from fault detection systems that locate fault points within electric stations. This system uses an AI-specific back-end processor to perform inferencing rapidly. Additionally, this fault diagnosis expert system is interfaced and integrated with a restorative operations expert system, an intelligent alarm processing system, and a protective relay setting and management system. The authors developed and adopted a power system fault diagnosis domain shell to ease system development, and used the protective relay operation simulation function of a protective relay setting and management system for system verification. >
TL;DR: A downed conductor, arcing fault detection system has been designed using multiple protection algorithms and the behavior of the prototype systems to staged faults, naturally occurring faults, and normal system disturbances is described.
Abstract: A downed conductor, arcing fault detection system has been designed using multiple protection algorithms. An intelligent analysis system processes the outputs from several algorithms to determine the "confidence" that a fault exists. The design includes careful attention to discriminating arcing faults from normal system activity to ensure system security. Key to the acceptance of this system is testing under actual field conditions. The results of long term tests on five utilities are presented. The behavior of the prototype systems to staged faults, naturally occurring faults, and normal system disturbances is described. Conclusions are drawn concerning the practical viability of this system. >
TL;DR: In this paper, the authors present a new piecewise constant current load model approximation technique that can solve a model as complex as the New England 39 bus system with composite voltage dependent loads much faster than in real-time.
Abstract: Electric utilities are becoming increasingly interested in using synchronized phasor measurements from around power systems to enhance their protection and remedial action control strategies. Accordingly, the task of predicting future behavior of the power system before it actually occurs has become an important area of research. This paper presents and analyses several approaches for solving the real-time prediction problem. In order to solve power systems with detailed load models fast enough for real-time prediction, the authors present a new piecewise constant current load model approximation technique that can solve a model as complex as the New England 39 bus system with composite voltage dependent loads much faster than in real-time. If the reduced order model is too large for real-time solution, then a pattern recognition tool such as decision trees can be trained off line to associate the post-fault phasor measurements with the outcome of future behavior. In this case also, the piecewise constant current technique would be needed to perform the offline training set generation with sufficient speed and accuracy. >
08 Oct 1995
TL;DR: The fault modes of a multilevel inverter are investigated with special emphasis on the five level inverter and the main focus or the paper is on device failure and the corresponding impact on the operating conditions and resulting stresses.
Abstract: Multilevel inverters are well suited for static condenser implementation in utility systems. With multilevel inverters, it is possible to realize low distortion voltage waveforms and keep losses low using suitable switching schemes. The complex topology of these inverters coupled with the large number of devices used increases the probability of device failure. In this paper, the fault modes of a multilevel inverter are investigated with special emphasis on the five level inverter. The main focus or the paper is on device failure and the corresponding impact on the operating conditions and resulting stresses. The presence of redundant states offers the possibility of continuing operation with inferior bus and device utilization following a fault. Failure of some devices is more critical than the failure of others, thereby emphasizing the need for adding redundant devices.
24 Apr 1995
TL;DR: In this paper, a multi-input multi-output (MIMO) recurrent neural network (RNN) is used as a versatile tool for the high-speed phasor detection and the adaptive identification of control and protection signals in power systems.
Abstract: A multi-input multi-output (MIMO) recurrent neural network (RNN) is used as a versatile tool for the high-speed phasor detection and the adaptive identification of control and protection signals in power systems. For the application as a phasor detector, a fast pseudo-gradient training is performed off-line to estimate the time-invariant weights of the RNN. This network is then operated in real-time, in recall mode only, to behave as a nonlinear fixed-coefficient filter. For the application as an adaptive identifier of nonlinear components, training is performed off-line for initializing the connection weights, but subsequently, they are continuously updated in real time. This results in an adaptive identifier suitable for detecting abrupt changes in complex nonlinear systems. Following an initial evaluation on synthetic signals, these two proposed RNNs are then validated using realistic waveforms generated from a series-compensated power system model.
TL;DR: In this article, the authors discuss and analyze animal-caused faults in power distribution systems and present an animal fault prevention technique that can effectively reduce these faults, and the results of such a technique are presented.
Abstract: The reliability, security and quality of power systems are significantly affected by distribution faults. One of the trends concerning distribution faults is the implementation of more preventive measures instead of reactive measures. In other words, we would like to prevent faults from happening rather than to restore the system after faults occur. Among the different categories of power distribution faults, animal-caused faults are probably the ones that can be prevented most easily and effectively if appropriate control actions are taken. This paper discusses and analyzes animal-caused faults in power distribution systems. The results of an animal fault prevention technique that can effectively reduce these faults is also presented. >
TL;DR: In this article, the fault data from both ends of the line together are brought together via data communications, either from one substation to the other or to a computer at a third site to which both substations can send the data.
Abstract: The most accurate and reliable fault location results are obtained using new algorithms that consider the fault data from both ends of the line together. Obviously, the data from the two ends must be brought together via data communications, either from one substation to the other or to a computer at a third site to which both substations can send the data. This might be a control center, relay engineer's office, or maintenance depot, which are ideal locations for really accurate fault location displays to be presented. Some two-ended location algorithms require time synchronization of the data from the two ends, which is not widely available. This article presents new calculations that do not require any such synchronization of the records to achieve excellent accuracy. Following an overview of the technical problems in computing fault location from fault voltage and current signals, a sampling of the newest and most accurate techniques that are easily implemented in existing digital devices for calculating location from one-ended or two ended line fault data records is given. >
TL;DR: In this article, the authors proposed a connectionist expert diagnosis system for the online fault diagnosis of a power substation, which can be constructed much more easily from elemental samples, such as bus voltages and feeder currents.
Abstract: This paper proposes a new connectionist (or neural network) expert system for the online fault diagnosis of a power substation. The connectionist expert diagnosis system has similar profile to an expert system, but can be constructed much more easily from elemental samples. These samples associate the faults with their protective relays and breakers as well as the bus voltages and feeder currents. Through an elaborately designed structure, alarm signals are processed by different connectionist models. The output of the connectionist models is then integrated to provide fine final conclusion with a confidence level. The proposed approach has been practically verified by testing on a typical Taiwan Power (Taipower) secondary substation. The test results show that rapid and exactly correct diagnosis is obtained even for fault conditions involving multiple faults or failure operation of protective relays and circuit breakers. Moreover, the system can be transplanted into various substations with little additional implementation effort. >
15 May 1995
TL;DR: In this article, the authors present an overview of a technique that estimates the location of a distribution line shunt fault, and some test results are also reported, but they do not discuss the reliability of the test results.
Abstract: Accurate estimation of the locations of line faults has been a subject of interest to electric power utility engineers and researchers for over twenty-five years. Almost all the research done so far has been aimed at finding the locations of transmission line faults. Lately, the location of faults on distribution lines has started receiving some attention because of public pressure on the utilities for improving the reliability of power supply. This paper presents the overview of a technique that estimates the location of a distribution line shunt fault. Some test results are also reported.
05 Apr 1995
TL;DR: This paper describes an analog cum digital model used for performance evaluation of numerical relays under real system conditions and an example of the use of this simulator, a numerical EHV4lne relay is used and the relay performance is analyzed.
Abstract: Environmental pressures, right of way problems for new transmission lines, large scale system interconnection and increasing power demand especially in developing countries call for new transmission technologies. Use of FACTS and HVDC is gaining momentum. Relaying problems in such systems require a sophisticated approach and numerical technology using high grade processors offers a promising solution. To establish the performance of such relays which are designed more as powerful schemes rather than as a conglomeration of individual relays, detailed testing is required using an elaborate real-time simulator model. These tests are not only necessary during design and development but also are required by the utilities as a part of their acceptance. Highlighting the requirements of a hybrid real-time simulator including the complete spectrum of power system dynamics, this report describes an analog cum digital model used for real-time assessment of system performance. SVCs, HVDC, ASC and CSC can be modelled fully digitally by computer simulation and transient real-time data injection as well as by an analog method using physical simulation with original converter controllers for performance evaluation of numerical relays under real system conditions. As an example of the use of this simulator, tests on a numerical EHV-line relay are described and the relay performance is analyzed.
TL;DR: A method for detecting pole slipping using power measurements taken at the generator's terminals is described, which has been shown to correctly detect pole slipping and remains stable for recoverable swing conditions and power system faults.
Abstract: The probability of pole slipping of dispersed storage and generation (DSG) synchronous machines is being viewed with concern, since this can damage the machine as well as promote power system instability. This is particularly the case for small and medium sized machines because their low inertia and high resistance make them inherently more unstable. Research has therefore been directed into new techniques for detecting pole slipping and the formulation of protection algorithms which can be included into an integrated microcomputer based protection scheme for these generators. This paper describes a method for detecting pole slipping using power measurements taken at the generator's terminals. This technique has been shown to correctly detect pole slipping using both computer simulation and a laboratory model power system. The algorithm remains stable for recoverable swing conditions and power system faults. >
TL;DR: In this article, the authors present the design, simulation, implementation and performance evaluation of a computationally efficient and accurate digital distance relaying algorithm, which provides fast and accurate fault impedance estimates for the three-zone protection of transmission lines.
Abstract: This paper presents the design, simulation, implementation and performance evaluation of a computationally efficient and accurate digital distance relaying algorithm. Published historical data were used in the first phase for validation purposes. Sample results illustrating highly accurate fault impedance estimates for various conditions are reported. The second phase uses voltage and current signals generated by the Alternative Transients Program (ATP) and a sample power system for various first-zone, second-zone and third-zone faults. Results of these studies, confirming the stability and computational efficiency of the algorithm, are presented and discussed. In the third phase, a prototype of the relay was developed and tested using real-time fault data generated from physical models of the transmission lines. Oscillographs for these conditions were recorded. Results of these tests indicating high speed relay operation are also discussed. The performance evaluation studies reported in this paper conclusively demonstrate that the new algorithm provides fast and accurate fault impedance estimates for the three-zone protection of transmission lines.
TL;DR: In this paper, a 16-bit single-board computer is used for the protection of parallel power transmission lines, which is based on comparing magnitudes of currents of two parallel lines.
Abstract: A digital algorithm for the protection of parallel power transmission lines has been implemented on a 16-bit single board computer. It has been tested on a physical model consisting of two synchronous machines connected through a double circuit line. The algorithm is based on comparing magnitudes of currents of two parallel lines. Details of the experimental set-up and the results of online tests for various operating conditions are presented. A procedure to adjust the relay settings adaptively is also incorporated. The results illustrate the successful operation of the algorithm in detecting faults on parallel lines. >
TL;DR: In this paper, the authors address grounding for transients, power, and personnel for pipelines, production facilities, gas plants, and power plants, including installations in plants and for isolated and remote equipment.
Abstract: Effective grounding is critical for protection of electrical equipment from transients. Grounding for personnel safety requires very distinct considerations. The application of the grounds may be similar in some instances. However, the installation will be radically different in isolated areas. Furthermore, the grounding of controls and computers present even more unusual requirements than the grounding of power devices. Additional concerns are circulating currents and injection of spurious noise. The paper addresses grounding for transients, power, and personnel. Designs include installations in plants and for isolated and remote equipment. The methods have been effectively used for pipelines, production facilities, gas plants, and power plants. Ten case studies of diverse applications illustrate the pertinence of the techniques and procedures. The case studies are: remote pump sensor erratic readings; unused data points inducing errors; remote sensor/input card failure during thunderstorms; data communication failure; blown fuses and data errors; conducting current flowing into grounding electrodes; fan motor failure; structural tower lightning strikes; high resistivity soil causing poor ground; and electrical shock when touching grounded metal enclosure.
TL;DR: In this article, the Static VAr Compensator (SVC) protection practices are presented, which comprise a combination of conventional protective relays as well as protection functions performed by the control system.
Abstract: Static VAr compensator (SVC) protection practices are presented. Protection schemes comprise a combination of conventional protective relays as well as protection functions performed by the control system. This paper describes different protection functions applicable to SVCs and includes a tabulated overview of possible SVC protection methods. A section is dedicated to testing SVC protection systems. The outlined test procedures may be adopted when commissioning new installations in order to demonstrate proper protection operation. Finally, an important aspect of SVC protective schemes is related to the interactions with transient overvoltages, harmonics, short-circuits, and geomagnetic induced current (GICs) of the transmission network. This paper discusses these issues and identifies areas where careful protection considerations are required. >