Mal-operation Of Distance Relay Research Articles

A fast, simple and local protection scheme for fault detection and classification during power swings based on differential current component

Among the various challenges of transmission line distance protection, it has become increasingly difficult to deal with the symmetrical phenomenon of power swing (PS) and it can lead to maloperation of distance relays and power system blackout. Distance relays have challenges in distinguishing the symmetrical fault during power swing and would send a wrong trip command to the circuit breakers, leading to major blackouts. To solve this issue, the main objective of this study is to provide a fast, simple, and local protection scheme based on differential current component (DCC), which is extracted by the difference in predicted and actual samples of local current component. Autoregression technique is used to predict the future cycle current samples using available samples. Based on the DCC, a novel index named differential current component ratio (DCCR) is introduced to effectively detect the internal symmetrical faults from fast/slow power swing conditions. Several tests are run for different fault types, different power swing frequencies, different fault locations, different fault resistances and different fault inception instants. Finally, the results are compared with the available methods. Results demonstrate the high accuracy of the proposed method in fast and accurate detection of internal symmetrical faults during power swing in different frequency rates in less than one cycle.

Harmonic Injection Based Distance Protection for Line With Converter-Interfaced Sources

Converter-interfaced renewable energy sour- ces are directly integrated into the power system using power electronics, so unique fault characteristics may lead to the maloperation of traditional distance relays. In this article, to deal with this issue, a harmonic injection- based distance protection method is proposed. The controllable harmonic current is injected without revising the controller structure, and the harmonic frequency and magnitude are determined according to the grid feature. Since the proportional integral cannot track the sine component without the static error, the actual frequency response will be deduced using the transfer function. On this basis, the harmonic impedance measured at the relay point can accurately reflect the fault distance due to the disappearance of the remote infeed, so the proposed method has a strong ability to withstand the fault resistance. Meanwhile, it only needs a few modifications to the phasor extraction method in original protection devices, so it is easy for engineering applications. Furthermore, typical fault ride through requirements can be still satisfied. Simulation results in PSCAD and real-time digital simulator verify the proposed method in different fault scenarios.

Fault Classification in a TCSC Compensated Transmission Line During Power Swing Using Wigner Ville Transform

During power supply swings, current and voltage waveforms are modulated with additional frequency elements which lead to maloperation of relays. This maloperation may cause cascade tripping of transmission lines, which results in the failure of electrical grid networks. Power Swing Blockers (PSBs) are employed to block and prevent maloperation of distance relays during power swing. Along with power swing, the presence of TCSC compensation in transmission line deteriorates the input signals to relays which make fault classification a complex task. During the PSB blocking period, modulated signals distorted with non-linearities of MOV operation complicate the fault diagnosis functioning. This challenge motivates to develop an algorithm for fault classification during power swings. To address aforementioned challenges, a Wigner Ville energy-based fault classification technique is proposed in this work. A modified 9 bus WSCC system with TCSC compensation is used for testing and validation of the proposed scheme. The scheme is tested for different cases like symmetrical, close-in fault, asymmetrical high resistance fault, and CT saturation, etc. The scheme is also validated against transient conditions like load and capacitor switching. The performance of proposed scheme is compared with existing schemes in literature. The above scheme is also implemented and validated on an Intel Cyclone V SOC FPGA. The results show that the proposed scheme classifies faults accurately during the simulation as well as on hardware platform.

Power Swing Blocking Algorithm based on Real and Reactive Power Transient Stability

Power swing due to the disturbance in the power system is a cause of the untrue operation of protective elements. Previously, many blackouts have been perceived and recorded due to reactive power mismatch problems, active power mismatch problems, and system venerability. The power system stability is usually disturbed due to the sudden loss of transmission lines, generators, and transformers. The present work proposes the concept of apparent power transient stability due to the transient disturbance. By considering that concept, we propose a power swing blocking algorithm to prevent mal-operation of distance relay. The proposed algorithm uses the relative frequency between the sending end bus and system standard frequency with simultaneous measurement of voltage decay of the transmission line. We have implemented the proposed algorithm on a single machine infinite system (SMIB) and the IEEE-9 bus system to compare the power swing detection and blocking performance with mho type out of step relay in different power swing conditions. In the end, results show the accurate performance, simplicity, reliability, and correct co-ordination of the proposed relay with distance relay, which ultimately solved the issue of mal-operation of zone-3 distance relay during complex power swing conditions.

An accurate technique for supervising distance relays during power swing

Power swing is a power system transient phenomenon that arises due to several reasons including line switching, line outage, sudden increment or decrement in load, faults, etc. Unnecessary tripping during power swing and unnecessary blocking for faults occur during power swing result in distance relay maloperation. Several cascaded outages and major worldwide blackouts have occurred due to maloperation of distance relays. This paper proposes a technique for supervising distance relays during power swing. The proposed online technique discriminates real faults and power swing accurately. It relies on constructing a locus diagram for the current and voltage differences (∆I-∆V) between the two ends of the protected line. The locus is estimated at every power frequency cycle to continuously monitor the state of the line by utilizing the synchrophasor measurements at the sending and receiving ends of the line. The proposed technique is tested for two-area, four-machine power system under faults at different locations of zone-1 and zone-2 regions of distance relays, fault resistances, fault inception angles and slip frequencies using MATLAB software. The simulation results proved the superior improvement of distance relay performance for handling power swing blocking and unblocking actions.

An Effective Zone-3 Supervision of Distance Relay for Enhancing Wide Area Back-Up Protection of Transmission System

Distance relays are quite vulnerable to maloperation during dynamic stressed situations. The apparent impedance seen by the relay encroaches the zone-3 resulting in distance relay maloperation that can initiate cascading failures. This paper presents an enhanced scheme for wide area backup protection which implements improved protection algorithms to decide final relaying status. A machine learning tool namely Deep Neural Network is utilized to build those protective relaying decision logics: RDL-1 and RDL-2. Wide area information retrieved from phasor measurement units (PMU) is used to take real time decisions. RDL-1 is designed to detect if the system is operating in normal or stressed condition. During normal state, traditional zone-3 relay undertakes the relaying decision. However, under stressed situations, RDL-1 switches the decision-taking to RDL-2. RDL-1 also predicts whether the system is progressing towards an out-of-step situation so that appropriate remedial action can be undertaken. Proposed scheme was studied on IEEE-39 bus New England system using MATLAB/SIMULINK and validated on Real Time Digital Simulator platform and third zone mal-tripping are avoided. Performance of the proposed algorithm was compared with the conventional blinder and other data-mining techniques which show considerably high classification accuracy.

Grey wolf optimization-tuned convolutional neural network for transmission line protection with immunity against symmetrical and asymmetrical power swing

The similar current–voltage profile during power swing and fault quite often leads to maloperation of distance relays. As compared to symmetrical power swings, discriminating a swing scenario from a fault becomes more challenging during asymmetrical swings arising due to single-pole tripping. Unlike symmetrical power swings, the presence of zero-sequence and negative-sequence current during asymmetrical swing scenarios hinders the application of classical power swing blocking schemes. In this regard, a convolutional neural network (CNN)-based protection scheme has been proposed in this paper, which, in addition to detecting, classifying, and locating faults, is also able to discriminate between power swing (both symmetrical and asymmetrical) and faults. The discrimination avoids possible maloperation during the non-faulty stressed conditions, thereby overcoming the limitation of the existing protection scheme. With the convolutional neural network, the raw signals are directly fed to the classifier, thus avoiding the computational cost associated with feature extraction in time and frequency domains. With the aim of achieving improved input–output mapping capability of CNN for larger datasets, an evolutionary optimization technique, i.e., grey wolf optimization, has been utilized for determining the optimal values of CNN tuning parameters. The performance of the proposed scheme has been extensively validated for a wide range of fault and power swing conditions in terms of standard indices, i.e., dependability, security, and accuracy. The effectiveness of the proposed scheme has also been evaluated for practical setting by performing real-time simulation on OPAL-RT digital simulator.

Prevention of maloperation of distance relay under severe stressed conditions for series compensated transmission line considering optimal placement of phasor measurement units

This study presents a new protection scheme for a series compensated transmission line, which prevents maloperation of distance relay during severe stressed conditions. The proposed method depends on the calculation of the net angular difference of positive sequence phasors of voltage and current signals acquired from phasor measurement units (PMUs). For fully observable power system network, the minimum number of PMUs required with a maximum number of system observability redundancy index has been identified by the suggested method using binary chemical reaction optimisation technique. The validity of the suggested technique has been confirmed by generating different severe stressed conditions along with faulty situations by modelling IEEE-39 bus system using RTDS/RSCAD software. The proposed technique offers effective discrimination between severe stressed conditions (symmetrical/asymmetrical power swing, load encroachment, voltage instability) and faulty situation even against wide variation in fault type, fault resistance, fault inception angle, degree of compensation and location of the series capacitor (middle or both ends). The accomplished results disclose higher discriminating capability between severe stressed conditions and faulty situation of the proposed technique in comparison with those of the several existing techniques.

Adaptive Protection of Partially Coupled Transmission Lines

The mutual coupling effect in parallel transmission lines renders the maloperation of conventional distance relays and makes it more difficult for power system operators to establish a reliable operation of transmission systems. This paper presents an adaptive protection system approach to improve the performance of conventional distance relays in partially coupled transmission lines. The conducted study deals with single-line-to-ground faults and the proposed algorithm is designed for ground distance units. The mutually coupled transmission lines, which are not terminated in same substations, are studied and the impedance estimated by associated distance relays is corrected through revising the level of zero sequence compensation. The compensation term is calculated based on the system equivalent sequential networks and it is substituted in an iterative process for enhancing its accuracy. The proposed approach can offset the fault resistance effect to calculate an accurate fault impedance. The proposed approach lies in the local protection category and utilizes local and very limited remote data for decision making. Simulation results present the adaptive features of the proposed protection scheme. Besides, practical applications of the proposed approach are demonstrated and analyzed through experimental studies by developing a prototype on a MCU (LPC2368_ARM7TDMI) processor.

A New Phase Angle of Superimposed Positive Sequence Current-Based Discrimination Scheme for Prevention of Maloperation of Distance Relay During Severe Stressed Conditions

This article presents a new scheme for accurate discrimination between symmetrical faults and severe stressed conditions (such as power swing, load encroachment, and voltage instability) under third zone coverage of distance relay. The proposed scheme is based on comparison of phase angle of superimposed positive sequence component of current, with a preset threshold. The threshold value is decided by performing various simulations on standard test systems along with appropriate validation through analytical analysis. The performance of the proposed scheme has been evaluated on different faults and severe stressed conditions by modeling IEEE-14 and IEEE-39 bus test systems in real-time digital simulator (RTDS/RSCAD) environment. The simulation results indicate that the presented scheme is able to distinguish symmetrical faults from severe stressed conditions effectively due to substantial change in the value of phase angle of superimposed positive sequence current. The threshold values utilized in the presented technique remains almost same for transposed/untransposed and uncompensated/compensated transmission networks. Comparative evaluation of the presented scheme with the existing scheme clearly indicates its superiority in differentiating symmetrical fault under severe stressed conditions.

DC offset estimation‐based fault detection in transmission line during power swing using ensemble of decision tree

The nuisance tripping of distance relay during power swing has been identified as one of the major causes for power system blackouts. Avoiding the risk of maloperation of distance relay and hence improving resilience during power swing, demands the development of a scheme capable of generating blocking signal during power swing and detecting a fault occurring with power swing from the measurement of current signal. In this regard, a protection scheme based on the hybrid framework of an ensemble of the tree, least square, and Adaline algorithm to perform the task of fault detection/classification, zone identification, location estimation, and power swing detection is proposed. The proposed scheme is based on the online estimation of DC offset information along with the fundamental component of the current signal. The performance of the proposed scheme has been analysed for diverse power swing and fault scenarios for two-machine system and Western System Coordinating Council 9-bus system. The simulation results reflect the effectiveness of the developed scheme in terms of sensitivity and reliability. Furthermore, to authenticate the effectiveness of the proposed scheme for practical scenarios, implementation, and validation of the proposed scheme has been carried out in a real-time environment using the OPAL-RT digital simulator.

Distribution power factor monitoring in presence of high RES integration using a modified load encroachment technique

This study presents a new approach in application of distance relay in distribution system. During the heavy load conditions, the load encroachment of impedance into the distance relay protection zones is a well-known reason for distance relay mal-operation. Therefore, all the modern digital distance relays are equipped with the load encroachment scheme. This study proposes the idea of using the load encroachment scheme of distance relay for monitoring purpose in the presence of renewable energy resources (RES) integration. Furthermore, it will be presented that based on the defined monitoring zones some alarms can be defined. The OpenDSS and Matlab software are used to test the effectiveness of the method with the IEEE 8500 node test feeder. The proposed method is tested with the unbalanced distribution system feeder loading and distributed model of solar generations. The dynamic performance of the proposed method is studied for on-line power factor monitoring of the feeder with the sun irradiation dynamic. The results show the necessity of power factor monitoring in the distribution system with RES integration. In addition, the simplicity of the proposed method allows its easy application in the digital distance relay.

Design and Implementation of an Algorithm for Diagnosis of Load Encroachment in EHV Lines

Zone-3 mal-operation of distance relays was one of the important cause for many of blackouts in worldwide. The one of the root cause for the mal-operation is encroachment of load into the Zone-3 characteristics. Such zone-3 mal-operations can be prevented by improvising the zone-3 characteristics which eventually avoids cascaded line tripping. This paper proposes and validates a new algorithm based on the total DC component and Phase angle of the positive sequence impedance to prevent its operation during the load encroachment conditions. Based on the proposed algorithm, improvement in the operation of Zone-3 element can be achieved. The relay can differentiate between actual system faults and load encroachment and thus ensure the security of the system. The proposed algorithm supplements the Zone-3 operation by introducing the ability to identify a load encroachment condition, and thus can avert the possibility of blackouts.

Simulation of Distance Relay for Load Encroachment Alleviation with Agent Based Supervision of Zone 3

Cascaded tripping of power lines due to mal-operation of zone-3 distance relays has been one of the main causes of many previous blackouts worldwide. Encroachment of load into zone-3 characteristics during stressed system operation conditions is a basic factor for such mal-operation of the relays. By improving the operation of zone-3, it is possible to prevent mal-operations so that cascaded line tripping can be avoided. For proper study of the behavior of distance relay during faults and load encroachment phenomenon, we must build a model of distance relay, so in this paper a modeling study of distance relay is implemented using MATLAB/Simulink program. However, this model is distinguished from previous models that, examines in detail the third zone of distance relay. Many cases are simulated with changing line loading and fault location to ensure the capability of the relay to detect the fault and thus the maximum load ability limit of distance relay is obtained. In order to prevent cascading events caused by hidden failures in zone-3 relays, agent based relay architectures have been suggested in the recent past. In such architectures each zone-3 relay contains agents that require communication with other agents at various relevant relays in order to distinguish a real zone-3 event from a temporary overload. In this paper, a local master agent is consulted by all zone-3 agents before a tripping decision is made. The master agent maintains a rule base which is updated based on the local topology of the network and real time monitoring of the status of other relays and circuit breakers. Cisco Packet Tracer program is used for running communication network simulations. The result of the simulation indicate that the time estimated to send and receive a packet data unit (PDU) message between one relay to anther can satisfy the communication requirement for the proposed scheme with fiber media.

Adaptive algorithm for transmission line protection in the presence of UPFC

The presence of flexible ac transmission system (FACTS) controllers in transmission lines causes mal-operation of distance relays. The series-shunt FACTS devices have larger influence on the performance of the relays compare to the other FACTS controllers. Furthermore, high-resistance fault is another factor that relay become under-reach and cannot correctly identify the fault. In this paper, a method is provided based on synchrophasors to eliminate the effects of unified power-flow controller (UPFC) and fault resistance on the distance relay. In the presented method, the data of voltage and current signals of buses will be sent to system protection center (SPC). In SPC, an algorithm is provided based on active power calculation in buses which is able to eliminate the effects of both mentioned factors. The main advantage of the proposed method, in addition to the simplicity of the algorithm, is the ability to operate in all types of faults and in high-resistance faults. Furthermore, a technique is presented in this paper to calculate UPFC data. A comparison has been performed between this technique and another method where UPFC data is directly transmitted to SPC by communication channel. In modeling of UPFC, detail model is used based on 48-pulses voltage source converters.

Secured zone‐3 protection during power swing and voltage instability: an online approach

Maloperation of distance relay under stressed conditions like power swing and voltage instability has been reason of various power system blackouts. Thus, it has become very important to make the decision making of the distance relay to be intelligent enough so that it is capable of differentiating between fault and other stressed conditions. There is no shortage of computational intelligent techniques suggested in the literature for this purpose. However, with the growing complexity of the power systems, there have been cases when various system parameters, system topology and so on suddenly change. This study suggests an online intelligent technique: online sequential extreme learning machine that gives accurate result on such circumstances owing to its features of being an online tool. The suggested technique based on wide area measurements consists of two levels of classifiers that segregate stressed conditions like power swing and voltage instability from fault. Performance of the online intelligent technique has been compared with other intelligent techniques defined in the literature. Moreover, by using synchronised phasor measurements, shortcomings of the conventional relay technology have been overcome.

Synchrophasor Assisted Adaptive Relaying Methodology to Prevent Zone-3 Mal-operation During Load Encroachment

Phasor measurement unit (PMU) has uniquely blended the contributions of modern information and communication technology in terms of time synchronization and fast data transmission to emerge as the smart sensor for advanced protection methodologies in smart power grids (SPG). The latency issue associated with the functionality of PMUs has made synchrophasors assisted protection algorithms suitable for backup protection, so as to efficiently prevent events, such as mal-operation of relays under load encroachment as well as other stressed situations. This paper proposes a novel methodology to prevent Zone-3 mal-operation of distance relays during load encroachment using the synchrophasor measurements obtained from PMUs installed in a widely-spread power system network. The proposed algorithm is to be implemented in transmission line protection center (TPC), where the synchronized three phase voltage and current phasors acquired from the PMUs are transferred to Phasor data concentrator (PDC) and are used to calculate the impedances seen by the relays in real time. A load encroachment situation and a faulty situation can be distinguished by comparing the impedances seen by primary and backup relays installed at different buses for protecting their respective transmission lines. Numerous case studies have been conducted in WSCC-9 bus system modeled in PSCAD/EMTDC environment to validate the proposed methodology.

Preventing transmission distance relays maloperation under unintended bulk DG tripping using SVM-based approach

With high penetration of distributed generation (DG) into distribution systems, an unintended bulk DG tripping as a consequence of severe disturbances such as 3-phase faults in the transmission system is a concern since it can further cause unintended operation of transmission distance relays. To address this matter, this paper presents a novel protection scheme based on support vector machine (SVM) approach. The proposed scheme detects bulk DG tripping following a fault in the power transmission system, and then makes sure there is no follow on distance relay maloperation. It is also able to detect a fault if it happens during the blocking period and hence unblock the relay operation correspondingly. Wide-area (WA) measurements obtained from phasor measurement units (PMUs) are used, in addition to local measurements, to improve the scheme selectivity. The New-England 39 bus system is used to test the proposed scheme. Simulation results are discussed and illustrated.

A new PMU based power swing detector to prevent mal-operation of distance relay

In conventional transmission line protection, a distance relay is used to provide the primary as well as remote backup protection. The voltage and current phasors measurement needed by the distance relay for determining the impedance may be affected by the power disturbances such as power swing. Consequently, this power swing may cause mal-operation of Zone three distance relays which in turn may affect on the reliability of the whole protective scheme. To mitigate these effects and hence improve the relay reliability, this work proposes a new real-time power swing detector using phasor measurement units for blinding the distance relay only during this transient disturbance. However, this developed detector will not block relay when the power swing accompanied with faults. To validate the present work, the performance of developed enhanced distance relay is tested by signals generated by Simulink/MATLAB simulator under different conditions. The test results show that this proposed scheme provides good discrimination between the transient currents and the fault current which in turn it may contribute in enhancing the reliability of Distance relay.

Distance Relaying with Power Swing Detection based on Voltage and Reactive Power Sensitivity

Abstract Sudden changes in loading or configuration of an electrical network causes power swing which may result in an unwanted tripping of the distance relay. Hence, it becomes utmost necessary to rapidly and reliably discriminate between actual fault and power swing conditions in order to prevent instability in power network due to mal operation of distance relay. This paper proposes a novel method for the discrimination between fault and power swing based on rate of change of voltage and reactive power measured at relay location. The effectiveness of the proposed algorithm is evaluated by simulating series of power swing conditions in PSCAD/EMTDC® software for different disturbances such as change in mechanical power input to synchronous generator, tripping of parallel line due to fault and sudden application of heavy load. It is revealed that the distance relay gives successful tripping in case of different fault conditions and remains inoperative for power swing with the implementation of the proposed algorithm. Moreover, the proposed scheme has ability to distinguish the symmetrical and asymmetrical fault occurrence during power swing condition.