Positive Sequence Fault Component Research Articles

Pilot protection based on novel comprehensive impedance of positive sequence fault component for distribution network

The integration of distributed power sources into the distribution network has changed the topology of traditional distribution networks, resulting in changes in fault characteristics, and brought severe challenges to conventional current protection of distribution network. This article proposes a protection method based on the comprehensive impedance of a new positive sequence fault component. Analyze the fault characteristics of positive sequence fault voltage and current during faults inside and outside the line area connected to different types of distributed power sources. The positive sequence fault components of voltage and current at both ends of the section are used to calculate the estimated line impedances. A novel comprehensive impedance is obtained by their subtraction. The ratio of comprehensive impedance to line impedance is constructed. The protection criterion for short circuit fault is given. The simulation experiments illustrate the effectiveness of proposed protection algorithm, not affected by the fault types, locations, permeabilities of distributed generations, has strong ability to withstand transition resistance.

MMC‐HVDC AC side line protection based on positive sequence fault component current ratio

AbstractThe high‐voltage direct current (HVDC) transmission based on modular multilevel converter shows the weak feed characteristic of limited fault current amplitude when connected to the traditional AC power grid, which leads to the risk of sensitivity reduction or even failure of the traditional pilot protection. Here, a modular multi‐level converter (MMC)‐HVDC AC side transmission line protection scheme based on positive sequence fault component current ratio is proposed. The positive sequence fault component current of the MMC‐HVDC side is calculated by using the positive sequence fault component current of the power grid side, and the fault is identified through the significant difference between the ratio of the positive sequence fault component current of the MMC‐HVDC side and the actual positive sequence fault component current of the MMC‐HVDC side in the case of internal and external faults. This method has the advantages of simple principle, low requirement for synchronous data, not affected by capacitive current and strong resistance to high resistance. The simulation results show that the algorithm can correctly partition internal and external faults, and is not affected by fault location, fault type and operation mode of converter station, and has high sensitivity and reliability.

Fault detection and location based SVM for three phase transmission lines utilizing positive sequence fault components

Transmission lines are an imperative element of the modern power systems. Any faults in them can cause an undesirable interruption in power supply. Precise analysis of these faults is important in-order to ensure an incessant supply of power. For this purpose, fault detection and classification are needed to clear any such faults and re-establish the system to maintain its normal operation. In this paper, a novel integrated approach of protective relaying with enhanced support vector machine algorithm has been adopted for detecting faults and its location estimation in long transmission line. The proposed scheme is successfully able to detect and classify different symmetrical and unsymmetrical faults along with some peculiar cases related to High Impedance Faults (HIF) and evolving faults, current transformer (CT) saturation/ capacitive voltage transformer (CVT) transient, close-in faults, swing condition, source strength variation, etc. The comparative analysis with recent proposed techniques declared the potentiality and robustness of the scheme

Fault identification method based on unified inverse-time characteristic equation for distribution network

Traditional inverse-time overcurrent (ITOC) relay adapts itself to the severity of the fault and can be used for fault identification in the main/backup relays. A fault identification method based on a unified inverse-time characteristic equation is proposed to aim at the problems of large setting workload and easy misoperation of inverse-time overcurrent relay after distributed generation access. It does not require a step-by-step setting and communication, and can realize adaptive coordination of multilevel relays. Firstly, the distribution law of positive sequence fault component voltage and the influence of distributed generation on its distribution characteristics are analyzed. Secondly, the setting principles and problems in implementing a unified equation for the multilevel coordinated relays are analyzed for the standard ITOC characteristic equation. The functional form of the user-defined inverse-time characteristic equation is derived from the ITOC equation and the setting principles considering the influence of fault conditions are given. The expression of the unified inverse-time characteristic equation is given, and the action sequencing of the adaptive fault position is obtained from the calculated tripping time. Finally, the simulation results validate the effectiveness of the proposed method.

A Precise Fault Location Method Independent of Line Parameters Based on Positive and Negative Sequence Fault Components

A Precise Fault Location Method Independent of Line Parameters Based on Positive and Negative Sequence Fault Components

A two‐stage IIDG fault control scheme considering the fault direction identification in active distribution networks

In traditional power systems, the positive sequence fault component (PSFC) based criteria is often used to identify the fault directions. If the PSFC impedance angle of the inverter‐interfaced distributed generator (IIDG) is between 0 and 90°, the traditional PSFC‐based criteria will remain applicable in active distribution networks (ADNs). However, due to the diversity of the IIDG fault control mode and the uncertainty of the positive sequence voltage variation caused by faults, the PSFC impedance angle of IIDG is difficult to determine. To solve this problem, this paper proposes a two‐stage fault control scheme for IIDG. At different stages, IIDGs select different power references to meet different requirements. In the first stage, the PSFC impedance angle of IIDG is fixed to a given value, thereby maintaining the applicability of the PSFC‐based criteria in ADN. The detailed power reference calculation method of IIDG is given for this stage. In the second stage, IIDGs can select different fault control modes to support the fault voltage flexibly. By using the proposed two‐stage IIDG fault control scheme, the protection devices can accurately identify the fault direction in ADNs, which is verified by the MATLAB simulation results. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

A protection scheme for active distribution network based on the cooperative control of inverter-interfaced distributed generators

Due to the existence of bidirectional fault currents in active distribution networks (ADN), a key issue of its protection is how to identify the fault direction. In traditional power systems, the positive sequence fault component (PSFC) based protection schemes are widely used, since they have good performance under different types of fault. However, due to the diversity of voltage variants and the influence from low-voltage ride-through (LVRT) requirement, the PSFC impedance angle of an inverter-interfaced distributed generator (IIDG) is difficult to determine. To solve this problem, this paper proposed a solution based on the cooperative design of the IIDG fault control strategy. Within a few power cycles after the fault occurs, each IIDG is controlled to output a specific positive sequence current according to the voltage variant. In this way, the PSFC impedance angle of IIDG is fixed to a given value under any fault scenario, thereby ensuring the applicability of PSFC-based protection in ADN. On this basis, the fault direction identification method and trip logic for the protection device are proposed. The effectiveness of the proposed method is verified by Matlab simulation results. The PSFC impedance angle of IIDG stabilizes at the desired value, and the output current of IIDG is always limited within a safe range during the whole process. Based on the sampled signals in the second power cycle after the occurrence of a fault, the protection device can use the PSFC-based criterion to accurately determine the direction of the fault.

Improved Differential Protection of Active Distribution Network Feeders Based on Ddtw of Positive Sequence Fault Components

Improved Differential Protection of Active Distribution Network Feeders Based on Ddtw of Positive Sequence Fault Components

A new protection scheme for transmission lines utilizing positive sequence fault components

In this paper, a novel integrated approach of protective relaying methodology has been adopted for detecting faults and its location estimation in long transmission line. First, the detection algorithm has been formulated using positive sequence admittance. Subsequently, fault location algorithm has been developed using positive sequence voltage and current phasors. The proposed algorithms have been implemented on a 50 Hz, 400 kV single-circuit transmission line in MATLAB environment. A wide range of diversified and challenging cases have been simulated to test the reliability of this scheme. The results confirm the preciseness of the algorithm, as it can produce accurate results under stressed conditions, viz. high impedance fault (HIF), current transformer (CT) saturation/ capacitive voltage transformer (CVT) transient, close-in faults, swing condition, source strength variation, etc. Moreover, this scheme has also been successfully tested in series-compensated and double-circuit transmission line, which brings out the superiority of this scheme. The comparative analysis with recent protective relaying techniques institutes the potentiality and robustness of the scheme.

A new technique based on fundamental frequency positive sequence fault components for fault location

This paper presents a new fault location technique based on the fundamental frequency positive sequence fault components, featuring robustness to the operating state of the prefault system and fault path resistance. Using the fundamental frequency positive sequence fault components, the technique described in this paper does not require the user to know the fault phases and fault type in advance or use a line zero sequence parameter, which is not only difficult to obtain but is also affected by soil resistivity and thus may be variable. In addition, based on the fault components protection principle, the method is inherently unaffected by the operating state of the prefault system. Accurate transmission lines' fault location is important for expediting their repair or reducing outage times, so the proposed technique could improve the quality and security of the electricity supply. This paper describes the characteristics of the proposed technique and assesses its performance by using the PSCAD/EMTDC simulation. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

A Fault Detection Method of Microgrids With Grid-Connected Inverter Interfaced Distributed Generators Based on the PQ Control Strategy

The fault characteristics of an inverter interfaced distributed generator (IIDG) depend on its control strategy and whether it has a low voltage ride-through (LVRT) capability, which cannot be a simple equivalent to a constant power or current source. Thus, it is necessary to consider the specific control strategy of IIDGs and perform specific research on the fault detection method of a microgrid. Based on the fault models of a grid-connected PQ controlled DG with an LVRT capacity, this paper analyzed the fault component characteristics of a microgrid under different operating conditions, such as high-impedance faults and low-impedance faults. The fault point is located using a new fault detection method based on the phase differences between the positive-sequence fault component of the bus voltage and the positive-sequence fault components of the currents in the feeders. Finally, PSCAD/EMTDC is used in the simulation analysis, and the simulation results verified the validity of the fault detection method.

An Improved Directional Relay Adapted to a Distribution Network with IIG Integration

The integration of distributed generation (DG) into a distribution network changes the network’s topology. Three-stage current protection for a radial distribution network cannot meet the requirements of relay protection for a distribution network with DG. A directional relay that is based on the positive sequence fault component (PSFC) can effectively identify faults in the positive and negative directions and can be used to solve the adaptability problem with three-stage current protection in a multi-source distribution network. However, DG and the traditional generators have different fault characteristics and are affected by different control strategies, which may lower the sensitivity of a directional relay based on the PSFC or even cause mal-operation. Focusing on this problem, this paper proposes an improved directional relay that is adapted to a distribution network with inverter-interfaced generation (IIG) integration. The improved scheme divides the operation zone of the directional relay based on the PSFC into sensitive and insensitive areas. If the result of a phase comparison is located in the insensitive area, further identification is needed according to a comparison of the current amplitudes. Simulation experiments are carried out based on PSCAD/EMTDC, and their results verify the correctness of the proposed scheme.

Positive-sequence-fault-component-based blocking pilot protection for closed-loop distribution network with underground cable

Closed-loop operation of distribution network has attracted more attention recently to improve supply reliability and adopt Distributed Energy Resources (DERs) friendly. Its protection is usually independent of distribution automation system (DAS). This article presents a blocking pilot protection method for closed-loop distribution network with underground cable, that can be accomplished by remote terminal units (RTUs) in DAS. First, operation value of RTUs is designed on the current variation after fault and the RTUs are synchronized automatically based on fault signal. Second, the power direction characteristic of positive-sequence fault component is analyzed when various short circuit fault occurs at different locations. Based on that, the state of Ring Network Cabinet (RNC) are classified into five types and uniform blocking signal exchanging rule between 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 is 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.

Real‐time monitoring of zone 3 vulnerable distance relays to prevent maloperation under load encroachment condition

Undesired trip operation of zone 3 units of distance relays in power transmission network, during static and dynamic load encroachment can lead to cascading failures and even catastrophic power system blackouts. Stressed conditions such as power flow redistribution and power swing can cause maloperation of the third zone of distance relays. Fast and dependable detection of the symmetrical faults, occurring during these conditions poses an additional challenge. One of the effective methods to avoid the zone 3 contribution in cascading failure propagation is the detection and monitoring of vulnerable relays which are exposed to maloperation in power system stressed conditions. In this study, a new relay ranking index is proposed for real-time identifying the zone 3 of distance relays, most vulnerable to incorrect operation due to load encroachment. A novel synchrophasor data-based monitoring index is also presented for supervision of critical distance relays operation. This index is extracted based on positive-sequence fault component phasors of the current and voltage signals obtained by modern PMUs or GPS based digital relays which have been reconfigured for this application. The proposed monitoring scheme is able to quickly distinguish the fault from load encroachment condition. The performance of the proposed supervisory scheme is evaluated and approved on a nine-bus WSCC system.

A positive-sequence-fault-component-based improved reverse power protection for spot network with PV

This article presents an improved reverse power protection for spot network with high penetration of photovoltaic (PV) interfaced with inverter. First, the current variation within a short time window is discussed respectively when fault occurs and PV operates with fluctuation. It can be used to determine the cause of reverse power. Second, the positive sequence fault component power is analysed when different types of fault occur at various locations. The fault section can be located mainly by comparing the power direction of positive sequence fault components among feeders, as well as comparing the output current of PV inverter with the current through its connecting switchgear. Finally, the improved reverse power protection for spot network with PV is presented, including the operating value and protection logic. This method can enhance the penetration of PV in spot network. The simulation model based on practical projects is constructed. The protection performance including load and PV fluctuation, and all kinds of fault is simulated with comparison to the present protection method. The simulation results prove the validity of the improved protection.

Principle and Implementation of Current Differential Protection in Distribution Networks With High Penetration of DGs

With the high penetration of distributed generations (DGs), the conventional radial distribution network is becoming an active distribution network (ADN). It has the characteristics of multisource, multibranch, bidirectional power and fault current flow, as well as weak infeed. To provide effective protection for such a network, a novel current differential protection scheme, together with new implementation technology, is proposed in this paper. In this scheme, instead of using phase currents, a positive-sequence fault component (PSFC) is introduced into the differential protection. By building the PSFC equivalent circuit of the ADN, the distribution characteristic of PSFC within the ADN is theoretically analyzed in detail, especially for the case when the ADN contains inverter interfaced DGs. The PSFC-based differential protection criteria for different types of feeder are then established and simulated. To put the scheme into practice, data self-synchronization and peer-to-peer communication techniques are established. Based on this principle and using an advanced hardware platform, a protection prototype is successfully developed and tested. The test results verify the feasibility of the proposed protection scheme.

Fault Identification of Power Grid Based on Wide-Area Differential Current and K-Means Clustering

A new method of fault domain identification is proposed based on K-means clustering analysis theories using the wide-area information of power grid. In the method, the node Intelligent Electronic Device (IED) associated domain is defined, and the relationship of positive sequence current fault component for the association domain boundaries is sought, then the conception of positive sequence fault component differential current for node IED association domains is introduced. The information of the positive sequence fault component differential current gathered by node IEDs is selected as the object of K-means clustering. The node IEDs of fault associated domains can be classified into one category, and the node IEDs of non-fault associated domains are classified into another category. With the fault area minimum principle, the group of node IEDs about fault associated domains can be obtained. The overlap of fault associated domains for different nodes is the fault area. A large number of simulations show that the algorithm proposed can identify fault domains with high accuracy and no influence by the operating mode of the system and topological changes.

A New Fault-Location Algorithm for Extra-High-Voltage Mixed Lines Based on Phase Characteristics of the Hyperbolic Tangent Function

A new fault-location algorithm for extra-high-voltage mixed lines based on phase characteristics of the hyperbolic tangent function is proposed. This paper takes overhead-cable-overhead mixed lines for example. The faulted section identification functions for overhead cable connections described by the hyperbolic tangent are developed separately when faults occur on the first overhead line, the middle cable, and the last overhead line. When a fault occurs on different sections, the faulted section identification functions appear as obviously different phase characteristics according to the phase characteristics of the hyperbolic tangent function. Thus, the faulted section can be identified. The fault location can be therefore accurately determined with the voltage and current positive-sequence fault components on both ends of the faulted section. Simulations and calculations with PSCAD and MATALB show that the fault-location algorithm is correct and accurate.

基于正序故障分量的电流相位差动保护的仿真

本文根据叠加原理给出正序故障分量的概念及特点，详细阐述正序故障分量在电流相位纵联差动保护中的应用原理，对比说明基于正序故障分量的继电保护原理较传统保护所具有的优点。以正序故障分量在电流相位纵联差动保护中的应用为例，利用MATLAB进行仿真验证，证明利用正序故障分量实现电流相位纵联差动保护更为灵敏可靠，还能克服常规保护的许多缺点。 Based on the superposition principle, this paper gives the positive sequence fault component con-cept and its characteristics, elaborates the application principle of positive sequence fault compo-nent in the current phase longitudinal differential protection, and illustrates the advantages of the protection principle based on positive sequence fault component compared with the traditional one. Using the application of positive sequence fault component in the current phase longitudinal differential protection for an example, through MATLAB simulation verification, it is demonstrated that using positive sequence fault component to achieve the current phase longitudinal differential protection is more sensitive and reliable, and also can overcome the disadvantages of the conven-tional protection.

Fault Identification Algorithm Based on Zone - Division Wide Area Protection System

As the power grid becomes more magnified and complicated, wide-area protection system in the practical engineering application is more and more restricted by the communication level. Based on the concept of limitedness of wide-area protection system, the grid with complex structure is divided orderly in this paper, and fault identification and protection action are executed in each divided zone to reduce the pressure of the communication system. In protection zone, a new wide-area protection algorithm based on positive sequence fault components directional comparison principle is proposed. The special associated intelligent electronic devices (IEDs) zones which contain buses and transmission lines are created according to the installation location of the IEDs. When a fault occurs, with the help of the fault information collecting and sharing from associated zones with the fault discrimination principle defined in this paper, the IEDs can identify the fault location and remove the fault according to the predetermined action strategy. The algorithm will not be impacted by the load changes and transition resistance and also has good adaptability in open phase running power system. It can be used as a main protection, and it also can be taken into account for the back-up protection function. The results of cases study show that, the division method of the wide-area protection system and the proposed algorithm are effective.