Power System Protection

In modern railway traffic systems, direct current (DC) electrification is a prevalent choice, with numerous traction networks adopting a variety of voltage levels to accommodate varying load current dynamics. These dynamics are influenced by passenger density, aggregate demand for electrical power, headways, and frequency of locomotive operations. Load currents are prone to surges during periods of dense traffic and transient phases such as acceleration, deceleration, and the start-stop sequences of trains. Such surges hold the potential to precipitate fault currents within the traction system, which are similar to those engendered by external anomalies. Conventional protection systems, such as the Détection Défaut Ligne'-French for 'Line Fault Detection), may not always effectively identify remote faults or prolonged overcurrent situations. These scenarios necessitate an advancement beyond the traditional fault detection methodologies, which are primarily reliant on fixed thresholds and may not account for the dynamic nature of the railway system's electrical load. This paper addresses the limitations inherent in the existing DDL protection mechanisms by focusing on the feeder attributes specific to the DC Traction System. In pursuit of this objective, we introduce an innovative adaptive current DDL algorithm to refine the rigid threshold paradigm inherent in the conventional approach. To facilitate a pragmatic assessment, the Rapid Rail network of Malaysia serves as a reference for emulating the railway's electrical system. This comprehensive analysis yields insights that are potentially useful for safety protocols in DC electrified railroad traffic systems

This work models a photovoltaic (PV) inverter connected to an IEC microgrid system. The purpose of this study was to find the characteristics of symmetrical components before and after a high impedance single phase short-circuit fault. The IEC microgrid system is tailored to the distribution system in Indonesia, where the applied voltage is 20 kV. Only parameters related to the short-circuit study are included in the model. A second-order generalized integrator frequency-locked-loop is utilized to represent the 3-phase PV inverter. The inverter model, previously treated as an ideal current source, and positive sequence current are no longer employed, as they fail to depict the characteristics of symmetric components during a phase-to-ground short-circuit fault. The IEC microgrid system connected to the PV inverter is simulated using ATPDraw-electro magnetic transient program (EMTP). Simulation results reveal that the changes in the symmetric component values of current after a fault experience a very insignificant increase. Meanwhile, the positive sequence voltage values following the short-circuit fault exhibit a negligible decrease. In contrast, the negative sequence and zero sequence voltage components after the short circuit fault undergo a significant increase.

The main purpose of this paper is to present architecture of automated system that allows monitoring and tracking in real time (online) the possible occurrence of faults and electromagnetic transients observed in primary power distribution networks. Through the interconnection of this automated system to the utility operation center, it will be possible to provide an efficient tool that will assist in decisionmaking by the Operation Center. In short, the desired purpose aims to have all tools necessary to identify, almost instantaneously, the occurrence of faults and transient disturbances in the primary power distribution system, as well as to determine its respective origin and probable location. The compilations of results from the application of this automated system show that the developed techniques provide accurate results, identifying and locating several occurrences of faults observed in the distribution system.

The main purpose of this paper is to present architecture of automated system that allows monitoring and tracking in real time (online) the possible occurrence of faults and electromagnetic transients observed in primary power distribution networks. Through the interconnection of this automated system to the utility operation center, it will be possible to provide an efficient tool that will assist in decisionmaking by the Operation Center. In short, the desired purpose aims to have all tools necessary to identify, almost instantaneously, the occurrence of faults and transient disturbances in the primary power distribution system, as well as to determine its respective origin and probable location. The compilations of results from the application of this automated system show that the developed techniques provide accurate results, identifying and locating several occurrences of faults observed in the distribution system.

Power system-controlled islanding is one of the mitigation techniques taken to prevent blackouts during severe outage. The implementation of controlled islanding will lead to the formation of few islands, that can operate as a stand-alone island. However, some of these islands may not be balanced in terms of generation and load after the islanding execution. Therefore, a good load shedding scheme is required to meet the power balance criterion so that it can operate as a balanced stand-alone island. Thus, this paper developed a load shedding scheme-based metaheuristics technique namely modified discrete evolutionary programming (MDEP) technique to determine the optimal amount of load to be shed in order to produce balanced stand-alone islands. The developed load shedding scheme is evaluated and validated with two other load shedding techniques which are conventional EP and exhaustive search techniques. The IEEE 30-bus and 39-bus test systems were utilized for this purpose. The results proves that the load shedding based MDEP technique produces the optimal amount of loads to be shed with shortest computational time as compared with the conventional EP and exhaustive search techniques.

The increase in global and Nigerian demand for electricity due to technological advancements has brought about numerous challenges, including voltage instability, power factor problems, and high-power losses in electrical power distribution networks. This paper presents the placement of a Static Var Compensator (SVC) in the power distribution network of Town One Station, Kaduna, Nigeria, to investigate its impact on improving and addressing the network's poor voltage profile and reducing the active power loss experienced by the network. For analysis, the bus voltage, power, and the current passing through the chosen feeders were measured and noted appropriately. The network parameters, including route length, transformer parameters, and maximum power flow, were obtained from the Kaduna Electricity Distribution Company in Kaduna, Nigeria. The distribution network was modelled and simulated in the ETAP software environment, both with and without Static Var Compensator (SVCs). The results obtained from the simulation indicated that buses 5, 7, 8, and 47, among others, have a voltage magnitude of 0.743-0.932 pu, which is clearly outside the acceptable limit of 0.95-1.05 pu. Further results showed that the network experienced real and reactive power losses of 8,527 kW and 23,535 kVAr, respectively. After the placement of the SVC with a 5.75MVAR rating, the active power loss decreased from 8527 kW to 6751 kW, indicating a 20.82% reduction in total active power loss experienced by the network. Additionally, the minimum network's bus voltage improved from 0.743 to 1.02 p.u.

This paper summarizes the technical activities of the Task Force on Power System Dynamic State and Parameter Estimation. This Task Force was established by the IEEE Working Group on State Estimation Algorithms to investigate the added benefits of dynamic state and parameter estimation for the enhancement of the reliability, security, and resilience of electric power systems. The motivations and engineering values of dynamic state estimation (DSE) are discussed in detail. Then, a set of potential applications that will rely on DSE is presented and discussed. Furthermore, a unified framework is proposed to clarify the important concepts related to DSE, forecasting-aided state estimation, tracking state estimation, and static state estimation. An overview of the current progress in DSE and dynamic parameter estimation is provided. The paper also provides future research needs and directions for the power engineering community.

This paper presents electromechanical and microcontroller-based over-current protective relays for electric distribution feeders. The objective is to determine the reliability of the system by comparing the performance of electromechanical and microcontroller-based relays. Electromechanical over-current protective relay on 33kV Itire-Ijesha distribution feeder was analyzed and modeled using MATLAB/Simulink. A numerical relay was proposed and also modeled using the real data of the existing Itire-Ijesha 33kV distribution feeder. While electromechanical relay was simulated as an instantaneous relay, the numerical relay was programmed and simulated as an IEEE moderately inverse definite minimum time (IDMT) relay. The simulation was for single line-to-ground fault, double line-to-ground fault as well as line-to-line fault. Comparing the performances of the two different models, numerical relay tripped in mini-seconds while the electromechanical relay model tripped in seconds. In conclusion, therefore, the numerical relay proved to be superior, smarter, and more reliable than the electromechanical relay.

A multi-terminal high voltage DC (MTDC) grid, is an optimum and cost-effective transmission network to minimize the energy crisis worldwide largely. However, the core demand for a fast DC protection scheme with an extraordinary strict fault clearance time of a few milliseconds, is a key research gap in this network, holding back its development and scalability. To bridge this gap, this paper proposes a novel protection scheme for a meshed MTDC grid. The main goals of the scheme include accurate discrimination of a faulty line, rapid fault detection, fault location estimation, significant fault current reduction, and fully selective isolation of only the faulted line, while continuing normal power flow in the healthy grid zones. Reliability of the scheme for long and extra-long-distance power transmission is increased by aiding the differential protection and Type-D traveling wave (TW)-based algorithms utilizing the distributed optical current sensing technology with the other auxiliary methods and backup plans. These auxiliary methods include independent discrete wavelet transform (DWT), current derivative polarity principles with a minimum sample (short time) window, overcurrent relays, and AC circuit breakers (ACCBs). A faulty segment of a transmission line is accurately discriminated from the healthy ones by measuring a series of multi-point differential currents on it. A faulty line at a particular DC node is accurately discriminated using the differential protection by measuring the current flowing into or out of each line from each side at every node to obtain the algebraic sum. The current sum of a real-time local transient data and a delayed remote data is compared to a preset threshold level. DC fault current is significantly reduced below the breakable levels by coordinating bidirectional hybrid DC circuit breakers (HDCCBs) with the active and passive fault current limiters (FCLs) and the half bridge-VSC-based modular multilevel converters (MMCs). The proposed concepts are successfully verified by the simulation results under a variety of fault scenarios and are found to be accurate.

Turkey is a country that has been the subject of many migration movements from in the past until today. Turkey aims to continue effectively Turkey's international protection system for asylum seekers with developed the mechanisms of international protection and legislative work. Systematizing legal regulations on international protection is very important in terms of for the development of the Turkish International Protection System. Law on Foreigners and International Protection No. 6458" (LFIP), prepared for persons seeking international protection, is an important turning point in the development of the Turkish International Protection System. Our study will be valuable in terms of examining the LFIP comparatively with the pre-LFIP periods and showing the effects of the arrangements made with LFIP on the Turkish International Protection System.

An application of phase-angle-difference based algorithm with percentage differential relays is presented in this paper. In the situation where the transformer differential relay is under magnetizing inrush current, the algorithm will be utilized to block the process. In this study, the technique is modeled and implemented using Simulink integrated with MATLAB. The real circuit model of power transformer and current transformers are considered in the simulation model. The results confirmed the effectiveness of the technique in different operation modes; such as, magnetizing inrush currents, current transformers saturation and internal transformer faults.

Theoretical Electrical Engineering August / 2001 Page 1 / 7 Abstract--In this paper we present a new method for the control of Petersen coils in resonant grounded networks. The major problem for the tuning at small neutral-to-earth voltages is to distinguish between resonance points simulated by the disturbances and real resonance points. In addition the controller has to recognize network modifications during the tuning operation. The first part of this contribution is a short description of the essential parameters that define the resonance curve. The second part deals with the disturbances at very small neutral-to-earth voltages. In consideration of these disturbances a new algorithm is presented to improve the accuracy of the tuning operation of the Petersen coil.

Statistics show that earth faults constitute a large portion of grid faults. Conventional relays are designed only for low ohmic earth faults under stationary conditions. They cannot handle high ohmic earth faults, which occur especially in rural networks with overhead lines, or intermittent earth faults in compensated cable networks. As a consequence the earth fault is very often not recognized or the wrong feeder is selected to be healthy. This increases tremendously the time for the localization of the earth fault. On the other side the effective protection of the networks became more and more important in the competitive markets. In this paper, a new algorithm for detecting also high ohmic earth faults up to some kOhm and its benefits are explained in detail. Results from field tests to demonstrate the feasibility of this new method are presented.

This paper presents results of earth fault field tests in a medium voltage network using new earth fault detection methods. An interpretation of voltage and current signals measured at the area of influence is provided. The pros and cons of different algorithms in different grid constellations are elaborated. The results show that new detection algorithms can provide stable directional decisions even in combination with unconventional transducers. This information is very important for the grid operator. With reliable information of the earth fault direction, especially in rural areas, the field engineers can be deployed more efficiently. Another focus of the tests was on the earthing system. At special grid components, such as dead end poles with cable link, the earth potential rise (EPR) was measured. With the signals measured throughout the tests, results of previously taken measurements to verify the earthing system could be confirmed.

Overheating is the single biggest cause of failure in switchgear. Modern circuit protection is provided by digital overcurrent relays which are operated by current, not heat so abnormal heating caused by loose connection bolts, ventilation failure or worn contacts is usually left undetected by conventional circuit breakers. This can lead to pre-mature failure of switchgear and also constitutes a potential fire hazard. Thermal imaging can help prevent this but is only valid for that `snapshot' in time. Continuous condition monitoring of the temperature of switchgear can substantially minimise down time of the installation and reduce the risk of fire.

The fault prevention and control of high-voltage transmission line is the key link in the development of the entire circuit system. During the operation of high-voltage transmission lines, due to the influences of connection methods, environmental factors, and climatic factors, there is a high possibility of faults occurring during operation. Line faults directly affect the safe operation of high-voltage transmission lines, and electricity is used by residents. Safety and the economic development of the country have brought adverse effects. Therefore, it is necessary to strengthen research on the prevention and control of failures of high-voltage transmission lines. This paper analyzes the main causes of the failure of high-voltage transmission lines, and proposes corresponding prevention and control measures for the faults, so as to provide help for the development of future fault prevention and control technologies.

Directional over current relays (DOCR) are commonly used in power system protection as a primary protection in distribution and sub-transmission electrical systems and as a secondary protection in transmission systems. Coordination of protective relays is necessary to obtain selective tripping. In this paper, an approach for efficiency reduction of DOCRs nonlinear optimum coordination (OC) is proposed. This was achieved by modifying the objective function and relaxing several constraints depending on the four constraints classification, non-valid, redundant, pre-obtained and valid constraints. According to this classification, the far end fault effect on the objective function and constraints, and in consequently on relay operating time, was studied. The study was carried out, firstly by taking into account the near-end and far-end faults in DOCRs coordination problem formulation; and then faults very close to the primary relays (nearend faults). The optimal coordination (OC) was ac...

Distribution networks were originally designed to operate as passive radial systems supplied from a single upstream source, with protection and equipment ratings selected under the assumption of predictable and unidirectional fault current contribution. The increasing penetration of distributed generation (DG) has fundamentally altered these assumptions by introducing additional fault current sources within the feeder. This paper presents a detailed investigation of the impact of distributed generation penetration on short-circuit levels in the 33/11 kV Enugu Electricity Distribution Network, Nigeria. A comprehensive network model was developed in ETAP and analyzed using the IEC 60909 short-circuit calculation method. DG penetration was defined as the ratio of total DG capacity to feeder peak load and simulated at multiple buses. The results show significant increases in fault current across all locations following DG integration. For three-phase faults, current levels increased from 1.842 kA to 2.508 kA at 9th Mile (36.1% rise), from 2.655 kA to 3.254 kA at Agbani (22.6%), from 4.120 kA to 5.012 kA at Kingsway (21.6%), and from 5.240 kA to 6.120 kA at New Haven (16.8%). Single line-toground fault currents similarly increased by up to 35.8% at weaker buses. The findings indicate that DG penetration significantly reduces network short-circuit margins and may push existing equipment toward their interrupting limits. The study highlights the necessity of mandatory short-circuit assessment and location-sensitive DG evaluation prior to interconnection in active distribution networks.

Combined with actual situation of Fengxian power Supply Company, the neutral grounding modes of Fengxian 35 kV and 10 kV power grid are studied in the paper. The different frequencies injected method is used to measure the capacitive current of Fengxian 28 substations, and the neutral grounding modes of the 28 substations are determined based on the measured values of capacitive current.

Fault current control by solar plant converters introduces different fault characteristics compared to conventional synchronous generator based systems resulting in numerous issues to the available protection methods. In this paper, the issues with conventional distance relaying is analyzed while protecting parallel lines connecting solar plant to grid and a new protection method is proposed using local voltage and current data. The proposed non-unit protection method derives positive sequence reactive powers for both lines for different solar plant operating conditions and uses their difference to ensure correct zone-1 protection. For faults during single circuit operation, the method includes an additional scheme comprising of instantaneous zerosequence overcurrent check and delayed distance relaying to derive correct protection decision. Performance of the proposed non-unit protection method is tested for parallel lines connecting solar plant in a 39-bus test system for different situations using PSCAD/EMTDC simulated data and found to be accurate. Comparative assessment reveals the high reliability of the proposed method.

Unlike the phasor measurement based protection in AC systems, the protection of DC systems deals with complex fault transients which mandates the isolation of the faulted segment within few milliseconds as continued fault current leads to overheating issue in power electronic converters. To this end, several works have been suggested based on unit and nonunit protections for DC microgrids. Threshold selection and protection coordination are the challenges associated with nonunit protection. Similarly, communication delay and link failure limit the application of unit protection. To address these issues, this paper presents a robust centralized protection scheme for DC microgrids, which is resilient to communication delay and link failure. It uses current of each line segment to compute the similarity of current change at both ends of the line segment to derive the protection decision. To overcome the communication failure from one end of the line segment or even from multiple segments, the proposed method uses data from adjacent segments to derive the protection decision correctly. Using PSCAD/EMTDC environment, the performance of the proposed method is evaluated for various cases and compared with available techniques. Finally, the accuracy of the protection algorithm is validated under experimental conditions.

Fault ride through compliance as imposed by the grid codes (GCs) prevents the inadvertent disconnection of the renewable plants from the network even during faults. Control algorithms applied in the converters associated with such plants modulate the fault characteristics significantly and result in malfunction of available fault type classifiers at times. In this article, an adaptive fault type classification technique is proposed for transmission network connecting converter-interfaced renewable plants. The method calculates sequence current angles in the faulted loop by determining pure-fault impedance of the plant at every instant during fault using local voltage and current data for fault type identification. The proposed method is tested for different fault situations on renewable integrated standard systems using PSCAD/EMTDC. The performance of the proposed method is found to be accurate in the presence of different types of renewable plants and complying different GC requirements. Comparative assessment reveals its superior performance.

Cascade tripping of power lines triggered by maloperation of zone-3 relays during stressed system conditions, such as load encroachment, power swing and voltage instability, has led to many catastrophic power failures worldwide, including Indian blackouts in 2012. With the introduction of wide-area measurement systems (WAMS) into the grids, real-time monitoring of transmission network condition is possible. A phasor measurement unit (PMU) sends time-synchronized data to a phasor data concentrator, which can provide a control signal to substation devices. The latency associated with the communication system makes WAMS suitable for a slower form of protection. In this work, a method to identify the faulted line using synchronized data from strategic PMU locations is proposed. Subsequently, a supervisory signal is generated for specific relays in the system for any disturbance or stressed condition. For a given system, an approach to decide the strategic locations for PMU placement is ...

This paper presents a new approach to distance relaying using fuzzy neural network (FNN). The FNN can be viewed either as a fuzzy system, a neural network or fuzzy neural network. The structure is seen as a neural network for training and a fuzzy viewpoint is utilized to gain insight into the system and to simplify the model. The number of rules is determined by the data itself and therefore smaller number of rules is produced. The network is trained with back propagation algorithm. A pruning strategy is applied to eliminate the redundant rules and fuzzification neurons, consequently a compact structure is achieved. The classification and location tasks are accomplished by using different FNN's. Once the fault type is identified by the FNN classifier the selected fault locating FNN estimates the location of the fault accurately. Normalized peaks of fundamental voltage and current waveforms are considered as inputs to all the networks and an additional input derived from dc component is fed to fault locating networks. The peaks and dc component are extracted from sampled signals by the EKF. Test results show that the new approach provides robust and accurate classification/location of faults for a variety of power system operating conditions even with resistance in the fault path.

Modeling a PV power plant using PVsyst software requires careful attention in selecting and adjusting the bifacial factor as it can significantly impact the performance of the modeled system or power plant. In designing solar power plants, we must consider important details. This article explores the design of a 100-kW rooftop solar power plant, addressing challenges and selecting the best design, particularly focusing on the impact of bi-facial coefficients. One of the challenges is accurately assessing the amount of radiation received from the rear of the panels and optimizing the row spacing to prevent shading. Another challenge is determining the effective installation angles and the height of the panels above the ground to enhance bi-facial efficiency. Neglecting to properly configure this factor can lead to incorrect energy yield estimates and negatively affect the economic analysis of the designed project. The main objective is to create an appropriate design for bi-facial PV systems in PVsyst by considering several obstacles. These challenges include field segment shading, solar energy availability in different months, nearby shading, roof configuration and wiring, cable design, grounding system, protection system calculation, risk assessment, lighting, and installation of lightning rods for shadow measurement. Various software, such as AutoCAD, PVsyst, ETAP, PVLPC, Helioscope and Volta, were utilized in this study. Moreover, the economic analysis in this study is conducted using RETScreen, a widely recognized software tool designed for evaluating the financial viability and performance of renewable energy and energy efficiency projects. This paper is based on a real project implemented in Arak, Iran. Furthermore, this paper explores incorporating climatic and environmental impacts into PVsyst software for accurate power plant performance prediction, providing a practical example for designing a 100-kilowatt plant.

This paper proposes the application of modular neural network as a mechanism to discriminate the direction of faults for transmission line protection. The modular neural network approach solves a relatively complex problem by decomposing it into simpler subtasks which are easier to manage and then assembles the solution from the results of the subtasks. In addition to the obvious advantages of neural network as fault classifier, incorporation of modularity to the network structure provides more important positive attributes like model complexity reduction, better learning capability etc. The modular neural network concept has been utilized successfully to develop a directional relay algorithm for a transmission system and subsequently implemented on a DSP TMS320F243 EVM-board.

Through the analysis of the fault of 66kV electromagnetic voltage transformer, it is clarified that the cause of the explosion of electromagnetic voltage transformer is the frequency division resonance of the system. The occurrence conditions and types of ferromagnetic resonance and the hazards to voltage transformers are introduced. In order to avoid the ferromagnetic resonance accident of the same type of voltage transformer again, an effective countermeasure is scientifically proposed.

This paper presents a method for calculating the reference currents needed for the command of an active filter. By using the Discrete Wavelet Transform (DWT) the high-frequency components of the currents are eliminated. Also, a reference is delivered to the control block of the active filter and a comparison is made between the DWT and the classical Fourier transform.

This paper describes a new method for complicated automation systems testing, particularly, power systems protective relays hardware and real-time software. Test platform is based on Monte-Carlo method utilization. A simulator produces voltage and current s amples and protection device settings. A control program performs test case generation, waveform production, event identification, and result comparison. This paper will discuss the advantages of stochastic approach and determination of test case number necessary to achieve the desirable level of confidence.

This paper describes a new method for complicated automation systems testing, particularly, power systems protective relays hardware and real-time software. Test platform is based on Monte-Carlo method utilization. A simulator produces voltage and current samples and protection device settings. A control program performs test case generation, waveform production, event identification, and result comparison. This paper will discuss the advantages of stochastic approach and determination of test case number necessary to achieve the desirable level of confidence.