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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]

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]

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]