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Highlights • A protection analysis tool for distribution networks with a high embedded generation is presented. • The tool determines the fault response of embedded generators with high convergence success. • The tool automatically simulates and assesses the pertinent faults for protection adequacy. Abstract The protection design philosophy of distribution networks is predicated on the inherent radiality that exists in such networks. However, the increased presence of inverter-interfaced embedded generation is compromising the radial nature of distribution networks. Hence, the increasing importance of accurately modelling the fault response of inverter-interfaced embedded generation is becoming apparent. Presently, the impacts of large penetrations of inverter-interfaced embedded generators on protection adequacy are determined through time-domain modelling. This paper proposes a tool for determining a snapshot of the expected protection response of distribution networks with inverter-interfaced embedded generation. The tool automatically simulates all fault types at the extremities of each protection zone and compiles the data to generate a report that showcases important information from a protection adequacy perspective. The tool can simulate fault responses in orders of magnitude faster than time-domain analysis using a load-flow like algorithm. This algorithm is designed to have a high convergence in fault scenarios and also approximate the fault behaviour of inverter-interfaced embedded generators. Finally, the tool investigates whether a new embedded generator installation may require an upgrade of network infrastructure or an amendment of protection settings. The tool is implemented using MATLAB and compared with time-domain simulations for verification purposes. [ABSTRACT FROM AUTHOR]

Highlights • A protection which isolates the SLG fault in neutral non-effectively grounded distribution with DG. • The time setting based on the grading coordination is added to the traveling-wave-protection. • Based on the coordination of relays the fault can be removed from both sides without communication. Abstract Electricity networks are in the era of major transition from stable passive distribution networks with unidirectional electricity transportation to active distribution, and the fault on the distribution lines should be cleared from both sides accordingly. This paper proposes a traveling-wave-based line protection scheme which can isolate the Single-Line-to-Ground (SLG) fault from both sides of the faulted line in neutral non-effectively grounded distribution network including Distributed Generation (DG) sources. In the proposed scheme, when a SLG fault occurs, first, relays distinguish the fault direction by comparing the polarities of the initial voltage and current traveling waves; and then the relays that detect the fault on the downstream and upstream sides operate based on the conventional time grading coordination, and the electrical changes of three-phase in a specified time window, respectively; finally, after operation of the relay upstream of the fault on the faulted line with the fastest time setting, the relay downstream of the fault operates by detecting the tripping of the opposite circuit breaker. In order to validate the efficiency of the proposed scheme, extensive simulations have been performed on a typical active distribution system using ATP-EMTP software. The simulation results indicate that the proposed line protection scheme can accurately and quickly isolate the SLG fault from both sides. [ABSTRACT FROM AUTHOR]

Highlights • Robust System model of a mechanical DC circuit breaker with current injection circuit in RTDS environment. • Comparison with PSCAD model. • Refined modelling of energy absorber in RTDS. Abstract The main goal of the paper is the modeling of the mechanical circuit breaker (MCB) that can replicate the breaker characteristics in real time environment. The proposed MCB with active current injection is modelled for a system level, which provides adequate representation of the circuit breakers for system analysis studies. External current-voltage characteristics of the proposed MCB models replicate the ones of the devices in the real world. It is well known that the DC circuit breaker (DCCB) needs to interrupt DC faults very quickly in order to avoid converter damages. The total current interruption time consists of fault detection time, time needed for the DC protection to provide command to the DCCB, and DCCB arc clearing time. Thus, it is necessary to demonstrate the system performance of associated protective devices through real time simulation, before these devices can be implemented and commissioned in practice. This paper presents a detailed modeling of the mechanical DCCB in real time simulation environment based on RTDS. The performance of the model is verified by the simulations based on PSCAD and meaningful conclusions are drawn. [ABSTRACT FROM AUTHOR]

Highlights: • Fault transient voltage is analyzed under condition of distributed-parameter dc line. • Fault transient voltage is used to discriminate between internal and external faults. • Faulty pole selection is based on the change rate of positive- and negative-pole currents. Abstract Multi-terminal flexible HVDC grids are required due to the high penetration of renewable energy. However, they are vulnerable to dc faults. To ensure their high reliability and continuous operation, fast and selective protection schemes are indispensable. This paper analyses the transient voltages in the case of dc line faults in modular multilevel converter (MMC)-based HVDC grid. Then, making use of the boundary effect of current-limiting reactors, a fast non-unit dc line protection scheme based on fault transient voltage is proposed. In addition, the faulty pole identification criterion is constructed based on fault currents. A MMC-based four-terminal HVDC grid is modelled using PSCAD/EMTDC, and extensive simulations are conducted to validate the effectiveness of the proposed scheme. Simulation results show that the proposed protection method not only can detect faults rapidly and accurately, but is also effective in detecting large-resistance faults. [ABSTRACT FROM AUTHOR]

Despite the fast, reliable and multi-purpose operation of MAS-based protection schemes, the inherent delay or failure of communication system must not affect the vital role of fault clearing, i.e., the ever-increasing renewables in distribution networks as well as network size increase has resulted in a heavy communication burden yielding to delay or even failure in communication. This fact will necessitate having an auxiliary algorithm to save protection system against any load curtailment. To affordably achieve this goal, this paper proposes a self-healing approach having the ability to temporarily replace the common MAS algorithms during emergency conditions. Accordingly, this paper, first, classifies the protection tasks into two hierarchical control levels; the first is responsible for clearing the fault while the second pursues some technical or economical goals. Next, using some less-considered capabilities of the common relays, a penetration-free algorithm is proposed to perform the first-control-level duties without MAS aid. Finally, the effectiveness of the proposed is proved on a practical distribution network. In general, this method can be a complement for the common MAS-based protection schemes to avoid any electricity interruption due to protection failure. [ABSTRACT FROM AUTHOR]

Expansion of the distribution network and close distance of distribution transformers lead to allocation of excessive surge arresters, while the number of arresters failures in the traditional routine may cause unwanted power outages. Therefore, this paper aims to propose a method to decrease the number of surge arresters as well as keep overvoltage protection of the network in the event of direct lightning strokes. According to different bus structures of the distribution network, elimination of allocated arresters is carried out by investigation of their protective distances at different stroke conditions. A guideline is presented for the IEEE 34-bus distribution system and the outcome is compared with the standard. The analysis is also carried out for a practical distribution network at West Mazandaran Power Distribution Company, Mazandaran, Iran. Possibilities for the elimination of surge arresters at the transformer station and installation of new transformers without allocation of new arresters are investigated in the analysis. Simulations are carried out based on the standard 8/20 lightning current wave at a transient analysis of DIgSILENT. [ABSTRACT FROM PUBLISHER]

Peak fault current and energy dissipation in high-voltage direct current (HVdc) circuit breakers (CBs) are very important parameters that impact dc grid protection development. This paper analyzes a hybrid DCCB (HCB) control that reduces peak current and energy dissipation by regulating the voltage across contacts of the ultrafast disconnector (UFD). This is achieved by manipulating the number of inserted surge arresters while contacts of the UFD are moving apart. The controller is seamlessly integrated with the current controller of HCBs. An analytical model for current and energy calculation is presented, verified, and employed for parametric studies. A PSCAD simulation with 320-kV, 16-kA test circuit confirms that the proposed voltage control reduces the peak current and energy dissipation by around 20%–30%. A 900-V, 500-A HCB laboratory hardware is described and the experimental results are shown to corroborate simulation conclusions. [ABSTRACT FROM PUBLISHER]

This paper proposes a method to analyze and improve the performance of interconnection protection based on distance relaying for wind power distributed generation (DG) in distribution systems. Of particular importance is distance protection that uses the concept of prefault voltages as reference quantities found to have issues with intermittent behavior of wind power DG. This concept is normally used in different distance protective relaying applications in order to increase the fault resistance coverage capability of the distance relays as well as to ensure selectivity, dependability, and security under extreme undervoltages. The main contributions of this paper are to analyze this issue and propose a method to enhance the performance of distance protection to mitigate this issue. In this methodology, several case studies are investigated with different penetration levels, weather patterns, and configuration topology of DGs under both normal operating conditions as well as fault conditions. Results for a case study are given. [ABSTRACT FROM PUBLISHER]

This paper presents a new method based on the relay agent for single-phase earth fault protection in radial distribution systems with distributed generators. In order to get the most informative fault features to discriminate fault for this system, traditional protection schemes based on different fault features are analyzed. The selection of fault features is discussed. Moreover, the cluster center of historical fault data is calculated to analyze the space distribution of fault data for each feeder by applying a fuzzy clustering algorithm. The space relative distance between the online sample data and the cluster center and the minimum value of the space relative distance among all of the relays at the relay agent are obtained. Finally, the coordination strategy of the relay agent is proposed to discriminate the faulty feeder. The proposed protection scheme is evaluated in a radial distribution network with distributed generations using PSCAD simulation. [ABSTRACT FROM PUBLISHER]

Significant financial losses due to voltage sags, short duration interruptions (SDIs), and long duration interruptions (LDIs) have been reported over the past years. The methods proposed in the literature allow us to estimate the annual indices related to process trips, though, as they are confined to voltage sags and LDIs, they do not take into account SDIs. This paper proposes to estimate annual financial losses related to process trip (FLPT) for each customer in the distribution system. The methodology correlates the attempts of reclosers to clear nonpermanent faults along with the concept of process immunity time in order to separately estimate the annual FLPT due to voltage sags, SDIs, and LDIs. This division allows the utility to quantify the severity of each of them and identify geographic areas where mitigation solutions should be deployed to avoid customer complaints and penalties by regulatory agencies. [ABSTRACT FROM PUBLISHER]

Nowadays, modern industrial processes are controlled by equipment highly sensitive to voltage sags and interruptions. Although the proposed methods in the literature allow utilities to estimate annual equipment trips due to voltage sags and permanent interruptions, they do not assess explicitly momentary interruptions. This paper proposes a probabilistic methodology that includes the attempts of reclosers to clear nonpermanent faults during the estimation of annual voltage sags and momentary interruptions at each busbar. Furthermore, voltage-tolerance ranges for each type of equipment are taken into account to quantify annual equipment trips due to voltage sags and momentary interruptions for each customer in the distribution network. The results allow the utility to identify a geographic area where sets of customers face high equipment trips during the year. The proposed methodology can be used by utilities to prioritize corrective measures to improve the quality of service to those customers most affected by annual equipment trips. [ABSTRACT FROM PUBLISHER]

Aging or prolonged subjection to stressed conditions cause changes in the parameters of fault current limiter (FCL). These changes must be noticed to take remedial actions if necessary and to make sure whether the system fault current level is within the rated capacities of existing equipment or not. This paper presents a method for estimating parameters of a series resonant type FCL (RFCL) by using synchronized time-domain data from both ends of a transmission line. Estimated parameters during normal operation are used for protection and stability analysis of the system and fault data are used to analyze the performance of RFCL during fault. Electromagnetic transient line model is used to calculate the current and voltage across the device which are used to estimate the parameters of RFCL. PSCAD/EMTDC simulations are used to test the method. Applications of the parameter estimation method are also presented and as a demonstration, effect of variation in current limiting reactor on system transient stability is analyzed. [ABSTRACT FROM AUTHOR]

This paper proposes a new fault ride-through (FRT) configuration for a fixed-speed induction generator-based–wind turbine (FSIG–WT). It utilizes a nine-switch converter (NSC) to enable shunt and series compensation in response to the system dynamics and grid faults. The steady-state control strategy and transient-management scheme are developed to ensure proper performance in steady-state, dynamic operation as well as enhanced FRT capability of the FSIG–WT. In addition to that, the developed control strategy tackles the balanced and unbalanced operation of the electric grid with an enhanced positive- and negative-sequence compensation control scheme. The recently reported grid synchronization scheme, namely, the frequency-locked loop (FLL) is implemented to achieve fast phase detection and transient response. Consequently, the performance of the FLL has been compared with the multiple reference–frame–phase-locked loop (MRF–PLL) to demonstrate its superior performance for enhancing transient response. The proposed topology, FLL, and control strategies are verified through a comprehensive simulation study to demonstrate the enhancement of the transient response and FRT capability of FSIG-WT in adherence to grid-code requirements. [ABSTRACT FROM PUBLISHER]

DC faults in HVDC grids lead to quickly increasing currents which should be interrupted sufficiently fast to prevent damage to power-electronics components. Although several primary relaying algorithms for HVDC grids have been proposed, fast backup relaying algorithms are needed to ensure system reliability when primary protection fails. This paper proposes a local backup relaying algorithm for HVDC grids, which leads to a short delay between primary and backup protective actions. The proposed algorithm, consisting of breaker and relay failure subsystems, uses classifiers which detect primary protection malfunctions based on the voltage and current waveforms associated with dc breaker operation. The algorithm initiates the detection of uncleared faults during primary protection operation, which results in accelerated actions by the backup protection after primary protection failure. The proposed algorithm is applied to a four-terminal HVDC grid. Study results show that the proposed algorithm accurately detects uncleared faults, identifies the source of primary protection malfunction, and expedites backup protective actions by operating during the fault current interruption interval of the primary protection. [ABSTRACT FROM PUBLISHER]

This paper investigates the latency of system integrity protection schemes (SIPSs) and proposes a bounded model of the communication delay. To be specific, SIPSs can be divided into wide-area protection and substation-area protection. For the former, the data buffering of phasor data concentrators and the automatic protection switching of synchronous optical network/synchronous digital hierarchy are utilized to limit the latency of regional and backbone networks, respectively; then, the communication delay is modeled as bounded, instead of average or stochastic in the literature. For the latter, the network calculus theory is used to restrict the latency in switched Ethernet networks, and the communication delay is modeled as bounded. In practice, SIPSs need to preprogram the time delay of protective relays and expect the communication delay as predictable or predetermined. Hence, the proposed bounded model is more realistic than the average or stochastic model. Further, the bounded model suggests the network dynamics and worst-case performances. It can be a useful tool in the relay setting as well as in the planning, design, and assessment of SIPS networks. [ABSTRACT FROM PUBLISHER]

Smart-grid development focusing on renewable energy sources is changing power system characteristics at a time when utilities are also focusing on improving customer service and resiliency of the grid. All of these activities require renewed attention to safety, protection, and control strategies that take advantage of available technologies while promoting newer ones. To explore better utilization of present technologies and chart the development of next generation protection and control technologies, the IEEE Power System Relaying Committee formed a working group to prepare a report describing and analyzing state-of-the-art and emerging technologies for centralized protection and control within a substation. When appropriately applied, these novel practical technologies may significantly improve the reliability of protection and control systems and the power grid. This paper reviews the key advancements in centralized protection and control systems. [ABSTRACT FROM PUBLISHER]

High-voltage direct-current (HVDC) systems are being widely employed in various applications owing to their advantages, such as bulk power transmission, long-distance transmission, and power-flow control. However, HVDC systems suffer from commutation failure, a major drawback that leads to increased device stress, interruptions in transmitted power, and problems related to protection relay setting, in turn, resulting in system instability during operation. Therefore, many studies have investigated the mitigation of commutation failure by considering its underlying factors, that is, ac voltage reduction, dc current increment, and crossing point shifts of phase voltage. However, these approaches are limited in that they are unable to mitigate intermittent commutation failure in a transient state. This study proposes an improved algorithm that mitigates commutation failure by considering the results of previous studies as well as the control characteristics of HVDC systems. The proposed algorithm is tested in various scenarios, and the test results verify its feasibility. [ABSTRACT FROM PUBLISHER]

In distribution and transmission electric power companies, many losses and risks are associated with corrosive processes that occur in buried structures, such as tower leg foundations of overhead transmission lines. Tower leg corrosion control at the foundation involves the collection and analysis of data generated by different inspection methods and practices for routine maintenance and repair. The aim of this paper is to demonstrate a methodology developed to identify locations and towers most susceptible to high rates of metal corrosion at the foundation of tower legs in order to facilitate better maintenance planning and evaluate the failure risks of these assets. To this end, using the Delphi methodology, variables that affect the corrosion phenomenon are correlated with geographic information and generate algebraic maps for advanced analysis. Despite the difficulty of searching and correlating georeferenced data, the results are interesting and promise possibilities for future applications. [ABSTRACT FROM PUBLISHER]

This paper presents a general framework to determine the location and capacity limits of distributed generation (DG) in the distribution system (DS) in order to maintain the traditional protection scheme. The impacts of DG penetration on overcurrent protection coordination are analyzed including fuse-recloser and recloser-relay. The minimum boundary of DG penetration in distribution system and the effects of modifying the setting of overcurrent protective devices have been investigated. Applying this framework in the developing countries could save money and time during integration of DGs to the network on a large scale based on country regulation. The proposed framework is implemented on a typical 11 kV overhead distribution feeder using Matlab/Simulink® and Etap® simulation packages. Protective device coordination under different fault locations and types with and without the DG is investigated. The results show the possibility of minimizing network power losses and improving voltage profile without replacing the existing protection system. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The security and reliability of a power system rely on establishing and maintaining proper coordination among protective relays. In addition to interrupting unnecessary loads, the probability of exposing hidden failures in protection system components such as Circuit Breakers (CBs) may increase as a consequence of miscoordination among relays. In order to evaluate how malfunction of a protection system can degrade the reliability of the system, this paper proposes a new Markov Chain Monte Carlo (MCMC) algorithm. Furthermore, to consider the impact of relay miscoordination on the hidden failure of protection systems, the paper proposes a failure index which is contingent on the magnitude and duration of fault currents. Then, for a sample test system, the reliability indices of SAIDI, EENS, and ECOST are obtained for three scenarios with different relay settings and coordination. The results are then compared to show that how protection miscoordination in medium-voltage networks degrades the reliability level of the system. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The correct and reliable operation of distance protections is significant to the safety and stability of power systems. Considering that the current failure probability models of distance protection, usually needing complicated calculation, could not accurately reflect the protection principle and the impact of protection coordination on relay failure probability, a new method of calculating the failure probability of distance protections based on the definitions of the starting intercept, the measuring intercept, etc. is proposed first, according to the operation characteristic of impedance relays. A detailed risk assessment flow of distance protection is formulated afterwards, taking into account the consequence of protection failures and risk indices. The distance protection risk assessment of the IEEE 9-bus system was given finally, and the results show that this approach could be used for evaluating the operating risk, as well as the potential risk of protection systems. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper presents a new approach for single phase-earth fault protection in distribution systems. Traditional protection schemes are analyzed and compared with one another for effective fault feature extraction. The maximum-likelihood method is also carried out on several copula functions to find the optimal copula to fit the fault feature data. Then, copula rank correlation is calculated by the optimal copula, and the principal component analysis technique is improved to preprocess and reduce the dimension of the fault data by decomposing the copula rank correlation matrix instead of computing the eigenvalues and their eigenvectors of the covariance matrix. Finally, the distance discriminant function is defined and operation criterion is proposed, and distance discriminant analysis is used to discriminate the faulty feeder. Simulation results of a practical 10-kV distribution system show that the proposed approach of fault protection is able to achieve better identification accuracy than the hierarchical clustering algorithm and Fuzzy c-means algorithms-based approaches. [ABSTRACT FROM AUTHOR]

Currently, self-healing is one of the most important functions in the smart grid. Meanwhile, fault detection, isolation, and restoration of feeder automation systems dominate the self-healing function in power distribution systems. The steps of the aforementioned function depend on the fault flag status of the feeder terminal unit. The conditions for setting this flag are judged by the feeder terminal unit overcurrent detecting curve. This paper found an efficient approach to calculate this curve via a half-interval method. Versatile application software with the curve plotting capability was also developed and deployed on the web server of the information-management department of Taiwan Power Company and is running successfully. [ABSTRACT FROM AUTHOR]

We report on recent developments in hybrid optical protection schemes that make use of passive fiber Bragg grating-based transducers for the distributed measurement of voltage and current. In addition to the details of the hybrid optical sensor technology, and its full integration with a commercial busbar protection relay, we report on the first-time laboratory demonstration of a centralized three-ended unit protection scheme featuring hybrid optical sensors capable of passive and wide-area coverage. Furthermore, we discuss the impact of this technology on present and future protection applications that may be improved or enabled by the proposed scheme. [ABSTRACT FROM PUBLISHER]

In large and interconnected networks, the coordination between all protective devices, without any violation, is very complicated and sometimes impossible. For obtaining reasonable and optimal coordination with suitable operating time (OT) for relays, some constraints are obliged to violation. In order to reduce the related violation and also the relays OTs, some objective functions (OFs) are proposed in literatures in which the discrimination times of the primary and backup relays is added to the OF. In this paper, for obtaining the optimal coordination of directional overcurrent relays, the OF is improved to overcome the drawbacks of the existing OF. In other words, as the main contribution, a new problem formulation is proposed so that not only the optimal settings of relays are obtained but also the OTs of the primary and specially backup relays are reduced considerably. In order to solve the proposed problem formulation, the effects of both near and far-end faults are considered. Also, regarding the protection system flexibility, the program is capable of choosing the best characteristic for each overcurrent relay. The genetic algorithm is used as an optimization tool, and the effectiveness of the proposed method is demonstrated by comparing the coordination results for the two sample networks with those obtained by using the recent developed OFs. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Purpose. Development of measures to limit the internal overvoltages in electric networks of power stations auxiliaries during single-phase ground faults in order to ensure the reliability of their operation. Methodology. Mathematical model of the electrical network, control and protection devices in mesh-node coordinates was proposed. The asynchronous motor processes to analyze the electromagnetic processes in electric networks of power stations auxiliaries were taken into account. The internal overvoltages in electric networks of power stations auxiliaries during single-phase ground faults were analyzed using the methods of mathematical modeling based on digital models. The special measures to limit the internal overvoltage were proposed. In order to simulate the transverse asymmetry, including single-phase ground faults the capacitive elements were proposed for usage considering the second law of commutation. Findings. The internal overvoltage in electric networks of power stations auxiliaries were investigated during single- phase ground faults using different limitation measures, in particular by installing of nonlinear surge protection devices and capacitor banks. Originality. In the paper in order to restrict the internal overvoltage and improve the start-up conditions of synchronous and asynchronous motors it was proposed to install the capacitor banks on buses of power station auxiliaries. Proposed measures also allow solving the problem of the voltage regulation. Practical value. The reliability of electrical networks of power station auxiliaries, as well as providing the technological process of electrical energy production by electrical stations depends on coordination of their insulation during single-phase ground faults. Currently such studies can be performed using mathematical experiments on digital models. [ABSTRACT FROM AUTHOR]

The implementation of a fault-location methodology in an electrical utility is dependent on the accuracy and ability of the method in locating all fault types. However, meeting these requirements is not an easy task. This paper presents a novel fault-location algorithm based on a new formulation for faults in overhead distribution systems. A single fault-location equation has been derived to provide a unified solution for any fault type. This is in contrast with other methods that use one equation for each fault type. The proposed method does not require the identification of the fault type; only the fundamental values of the voltages and currents that are measured at the substation terminal are required to solve the proposed fault-location equation. An overhead 11-kV, 21-bus, real-life radial distribution feeder is simulated to evaluate and test the viability of the proposed method using the PSCAD/EMTDC software. The results indicate that the proposed method gives high accuracy and can be implemented with the available technology. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In dc distribution grids, residual ground current protection is more feasible than in ac distribution grids, where stray capacitance leads to significant ac ground currents. However, when meshing dc distribution grids, circulating net currents can appear that resemble residual ground currents and would trip traditional protection schemes. This letter introduces this phenomenon in both unipolar and bipolar dc distribution grids. Furthermore, worst case net current magnitudes are derived and examples are shown. Implications for measurement and protection devices are discussed. [ABSTRACT FROM PUBLISHER]

Summary: Closed‐loop operation of distribution network has attracted more attention recently to improve supply reliability and adopt distributed energy resources friendly. But its protection is usually independent of distribution automation system (DAS). This article presents a pilot protection method for closed‐loop distribution network with underground cable by comparing current phase, which can be accomplished by remote terminal units (RTUs) in DAS. Firstly, operation value of RTUs is designed on the current variation after fault and the RTUs are synchronized automatically based on fault signal. Secondly, the current phase characteristic of positive‐sequence fault component is analyzed when various short circuit fault occurs at different locations. Based on the current phase difference, the state of ring network cabinet is classified into four types, and uniform fault location rule by adjacent RTUs is designed. The fault can be located and isolated directly by cooperation of adjacent RTUs. The setting principle and the operation logic for the pilot protection are given, and its performance is analyzed. Finally, simulation model based on PSCAD is constructed. The simulation results prove that this protection can locate and isolate faults timely on the premise of high sensitivity. It has strong ability of enduring fault resistance, and it can fit closed and open operation mode. [ABSTRACT FROM AUTHOR]