Fault Current Magnitude Research Articles

Enhanced fault classification in inverter-fed transmission lines using deep learning

Abstract The conventional power transmission system with synchronous generators is protected with phase angle-based approach that decides which type of faut is occurred on the transmission line system. However, the phase angle-based fault classification method is no longer applicable for systems that have integrated Inverter Based Resources (IBR). The control technology employed for grid integration of renewable sources controls the fault current magnitude depending upon Grid code requirements which results in mal operation of relay. A new fault classification scheme is proposed in this paper which aims at precise faulty phase selection using deep learning techniques. Deep learning techniques have gained significance in the field of protection because of the big data availability from Phasor Measurement Units (PMU’s). This paper describes a new approach of fault classification for systems connected to renewables with the application of Long Short-Term Memory (LSTM) Deep learning network.

A new fault detection and relay coordination technique for low voltage DC microgrid

Integration of various distributed generation units in the DC distribution network creates an outsized impact on magnitude and direction of fault current. The specific behaviour of fault current during a short circuit fault demands quick and reliable detection and isolation of fault, which poses a significant challenge in developing an effective protection and coordination scheme for DC microgrids. In this regard, a new fault detection and relay coordination algorithm is proposed for a Low voltage DC (LVDC) microgrid, which utilizes inverse time relay characteristics based on variance of fault current. While the relay responds and picks up during both internal and external faults, its operation is automatically limited upon operation of the downstream circuit breaker without the need for any communication channel. The efficacy of the proposed strategy is evaluated by modelling a mesh-connected DC microgrid network using PSCAD/EMTDC software. The protection coordination problem is developed as a constraint non-linear optimization problem to determine optimal relay settings. The proposed approach has been tested by simulating various types of faults at different fault locations and fault resistances along with various microgrid operating modes. The results suggest that the proposed strategy stands out by optimizing relay operating time and providing backup protection while upholding relay coordination. A comparative assessment of the proposed technique with existing ones proves its effectiveness in terms of swift relay tripping time, better immunity against noise, and independency against microgrid operating mode and topology.

An advanced graph algorithm-based protection strategy for detecting kilometric and cross-country faults in DC microgrid

Low voltage DC microgrids (LVDC) are on rise, because of increase in usage of electronics-based utility loads. However, the protection and safety aspects of these grids remain unresolved due to the fault current magnitude, unnecessary tripping, and blinding of protection. In this paper, an adaptive differential protection system incorporated with an advanced graph algorithm is proposed for DC microgrid. This graph algorithm is a combination of Fenwick tree and Bidirectional Dijkstra algorithm. Fenwick tree algorithm is used to determine the network configuration and Bidirectional Dijkstra algorithm is used to determine the least distance from the fault location to the nearest distributed generations. The developed protection scheme is applied to a 7 bus, 400 V DC microgrid setup using Real Time simulator (control hardware in loop) to detect and clear the faults such as kilometric faults, and cross-country faults. In terms of efficiency, the proposed algorithm demonstrates superiority over the conventional algorithm by detecting and rectifying faults in 384 μs.The results depict the robustness of the protection setup in clearing the faults rapidly with minimum network disconnection.

Performance Evaluation of Grounding Systems of Medium-Voltage Concrete Poles: A Comprehensive Analysis

Designing and installing efficient grounding systems in power distribution networks is considered a complex and crucial task to ensure the reliable operation of power-protective schemes while mitigating hazardous potentials arising from faults, thereby safeguarding both personnel and equipment. This paper aims to offer guidance on designing effective grounding systems in distribution networks by assessing the influence of parameters such as soil structure, fault current magnitude, and fault clearing time. This involves proposing a more precise methodology for calculating hazardous potentials, leveraging software tools like PowerFactory, to accurately determine short-circuit (SC) currents and fault clearing times at specific locations where grounding grids are to be installed. Consequently, Distribution System Operators (DSOs) can design tailored grounding systems that optimize techno-economic considerations without unnecessary over-dimensioning, accounting for the unique characteristics of the Medium-Voltage (MV) Line and soil structure.

High Impedance Fault Detection and Localization Using Fully-Connected Convolutional Neural Network: A Deep Learning Approach

The detection and localization of high impedance faults (HIF) in power systems are challenging due to the low fault current magnitude, which often falls below the detection threshold of conventional devices. HIF events introduce harmonics into the network, posing risks to the safety of connected equipment, including the potential for igniting fire which endangers lives and properties. In this study, Emanuel's HIF model was used to generate HIF signatures resembling real HIF events. Model parameters were adjusted to mimic various contact surface impedances. Two datasets were created: 'no-fault' data, simulating the network without HIF, and 'fault' data, incorporating HIF waveforms by simulating single and multiple lines with the HIF model. The faulted line was divided into five segments along the 33 kV line to capture fault signatures at different locations. The generated data, including current waveforms and magnitudes, were processed and divided into an 80:20 ratio for training, validation, and testing using a deep fully connected Convolutional Neural Network for HIF detection and location. The results showed an impressive accuracy rate of 99.44% and 99.78% for detection and location respectively, representing a significant advancement in HIF detection and location, and offering practical applications for enhancing power line safety.

Transient Analysis of 9-Bus System using ETAP

This research paper presents a transient analysis of a 9-bus power system using ETAP software. The simulation results obtained from ETAP are analyzed in terms of voltage and current waveforms, fault current magnitudes. However, the system experiences voltage and current fluctuations during fault conditions, which can lead to instability if not properly addressed.

Communication-less adaptive directional overcurrent protection strategy considering islanded mode detection in active distribution networks

The integration of distributed energy resources (DERs) in electric distribution networks originates the Active Distribution Networks (ADNs). The presence of DERs introduces challenges to conventional protection schemes due to bidirectional power flows and variations in fault current magnitudes; furthermore, the connection and disconnection of DERs result in multiple ADN operating modes (OMs), deteriorating the effective operation of protective relays. Considering the above, this document presents an adaptive protection strategy to address the challenges related to the variable nature of the ADN operation. The main contribution of the proposed approach is accurate islanded mode detection without requiring communication links, enabling fault detection in all ADN operating modes. The protection strategy maintains directional overcurrent relays' coordination using local voltage and current measurements to continuously estimate the Thevenin equivalent, fault currents, and adaptive coefficients.Relay coordination is maintained through tests conducted on a modified IEEE 34-bus feeder, considering several OMs, fault types, and locations. A comparison between the proposed adaptive protection strategy and a conventional overcurrent scheme shows that relay operating time is better in 100% of the analysed cases for the former strategy. On the other hand, the maximum errors in the fault current estimation using the Thevenin equivalent parameters are between 0.05% to 2.6% for all of the analysed operating modes when compared with the true fault current magnitudes. Finally, the adequate results validate the potential of the proposed communication-less protection strategy for modern protective relaying applications.

An Overview of DC Microgrid Protection Schemes and the Factors Involved

The development of a suitable scheme for protection of DC microgrids is still a major challenge. This is due to the shortage of practical experience in appropriate protection guidelines and standards related to the uncertainty in the network topology, absence of a natural current zero-crossing point in DC systems, and dependence of fault current shape and magnitude on various factors. These factors include network topology, type of converters used in the network, type of fault and its location, fault impedance, and type of system grounding. In this paper, these factors and their impacts on the development of a comprehensive protection plan for DC microgrids have been investigated. Various algorithms that have been proposed in previous studies for fault detection and location are reviewed, and the technical challenges associated with the use of communication links in smart protection systems are described. In addition, the advent of new technologies for development of DC circuit breakers are reported, which are different from the conventional AC circuit breakers due to the differences between the faults in DC and AC microgrids and their respective clearance times. This comprehensive review covers all aspects of the DC microgrid protection including topology, converters, configurations, and types of faults.

A faulty feeder selection method for distribution network with unintentional resonance in zero sequence circuit

Faulty feeder selection is a challenging task for distribution system operator due to the low earth fault current magnitudes in compensated networks. However, extensive cable usage, especially in metropolitan cities, causes unintentional resonance in the network earthed through inductance or grounding transformer. The unintentionally resonated networks are not designed like intentionally compensated networks where faulty feeder should be isolated in a predetermined time. There are transient zero sequence current based methods, particularly synthesized for compensated networks to identify faulty feeders. However, zero sequence-based faulty feeder selection methods have drawbacks in the presence of underground cables. Further, transient zero sequence current is prone to many parameters such as capacitive imbalance and fault resistance.In this study, a transient negative sequence current based faulty feeder selection method is proposed. The effectiveness of the proposed method is demonstrated in a simulated 151-node distribution network. EMTP simulations are carried out by considering different fault inception times, fault resistance and capacitive imbalance of the system. Results show that negative sequence current offers selective faulty feeder selection and no false trip is observed in a representative unintentionally resonating distribution network.

An Adaptive Centralized Protection and Relay Coordination Algorithm for Microgrid

To meet the increased customer demands, microgrid evolved. The structure of microgrid changes dynamically due to the intermittent nature of renewable-based generation, status of the distributed generator and opening of breakers for fault/maintenance. Hence, the magnitude of fault current is dynamic in nature. In order to deal with these dynamic changes, this paper addresses an adaptive central microgrid controller-based protection and relay coordination scheme, which revises the relay settings dynamically (both radial and looped configuration) for every change in topology. In the proposed algorithm, the primary relay responds to a fault immediately since the individual relays are given with fault level setting. For any abnormality in the network, the fault location is determined both via local relay and microgrid central controller (MCC). Hence, even though the local relay fails to identify the fault due to high fault impedance, the MCC locates the fault accurately and isolates the minimum faulty part. The coordination between relays is carried out by MCC in a time-graded manner based on microgrid central protection and relay coordination algorithm. The proposed algorithm is tested using Matlab in a microgrid built based on the IEEE 33 bus distribution network.

Impact of Copper Stabilizer Thickness on SFCL Performance with PV-Based DC Systems Using a Multilayer Thermoelectric Model

Utilizing renewable energy sources (RESs) to their full potential provides an opportunity for lowering carbon emissions and reaching a state of carbon neutrality. DC transmission lines have considerable potential for the integration of RESs. However, faults in DC transmission lines are challenging due to the lack of zero-crossing, large fault current magnitudes and a short rise time. This research proposes using a superconducting fault current limiter (SFCL) for effective current limitation in PV-based DC systems. To properly design an SFCL, the present work investigates the effect of copper stabilizer thickness on SFCL performance by using an accurate multilayer thermoelectric model. In the MATLAB/Simulink platform, the SFCL has been modeled and tested using different copper stabilizer thicknesses to demonstrate the effectiveness of the SFCL model in limiting the fault current and the impact of the copper stabilizer thickness on the SFCL’s performance. In total, four different thicknesses of the copper stabilizer were considered, ranging from 10 μm to 80 μm. The current limitation and voltage profile for each thickness were evaluated and compared with that without an SFCL. The developed resistance and temperature profiles were obtained for various thicknesses to clarify the mechanisms behind the stabilizer-thickness impact. An SFCL with an 80 µm copper stabilizer can reduce the fault current to 5.48 kA, representing 71.16% of the prospective current. In contrast, the fault current was reduced to 27.4% of the prospective current (2.11 kA) when using a 10 µm copper stabilizer.

A Communication-less adaptive protection scheme for Self-Healing distribution systems

Network reconfiguration has allowed supply restoration to disrupted areas after fault events. However, changes in network topology can alter the direction and magnitude of fault currents and jeopardize the coordination of overcurrent relays. Adaptive protection schemes using system-wide communications have been developed to solve this issue by performing dynamic relay recalibration. Unfortunately, system-wide communications are also associated with huge economic costs, data integrity issues, and limitations of infrastructures. Moreover, in less developed communities, such schemes are less applicable. Although various communication-less schemes have been proposed, they mainly focused on adapting overcurrent relay protection for different distributed generation penetrations and microgrid islanding statuses. Currently, no communications-less adaptive protection method has been proposed to address the miscoordination of protection relays caused by network reconfiguration for supply restoration. Thus, this paper presents a communication-less adaptive protection scheme to maintain relay coordination in a reconfigurable distribution network that performs supply restoration. The scheme deploys microcontroller units to predict the correct relay settings by monitoring load flows through the relays. The scheme is demonstrated on the IEEE 33-bus and 69-bus test distribution systems using two different relay placement strategies, non-directional and directional relays. The proposed scheme achieved up to 10.8 times lower disruptions than the existing system in N-1–1 contingency scenarios. Overall, the scheme provides a simple and low-cost alternative to improve the effectiveness of power system protection in a reconfigurable network.© 2017 Elsevier Inc. All rights reserved.

Artificial Neural Network Based Algorithm for Fault Detection in a Ring DC Microgrid Under Diverse Fault Conditions

The DC microgrid has become a greater power system in modern power technology due to its wider acceptance as compared to the AC-based traditional power distribution network. Nevertheless, protection of the DC microgrid is a difficult and complicated task due to numerous types of fault scenarios such as pole-to-ground and pole-to-pole faults, variation in fault current magnitude during grid connected and islanded mode, as well as bidirectional behaviour of the converters. In addition to the abovementioned challenges, fault detection during varying fault resistance and intermittency is also a crucial and tricky task because the level of the fault current can vary due to the distinct value of the fault resistance. Therefore, in this manuscript, an ANN-based protection scheme is proposed to detect the fault under varying fault conditions. Furthermore, to investigate the appropriateness of the protection scheme, DT and kNN-based techniques have also been considered for analysis purpose. In the proposed protection scheme, the tasks of mode identification, fault detection/classification, as well as section identification, have been proposed. The results in Section 5 indicate that the protection scheme is capable and accurate for fault detection in any type of faulty condition.

Empirical Wavelet Transform-Based Intelligent Protection Scheme for Microgrids

Recently, the concept of the microgrid (MG) has been developed to assist the penetration of large numbers of distributed energy resources (DERs) into distribution networks. However, the integration of DERs in the form of MGs disturbs the operating codes of traditional distribution networks. Consequently, traditional protection strategies cannot be applied to MG against short-circuit faults. This paper presents a novel intelligent protection strategy (NIPS) for MGs based on empirical wavelet transform (EWT) and long short-term memory (LSTM) networks. In the proposed NIPS, firstly, the three-phase current signals measured by protective relays are decomposed into empirical modes (EMs). Then, various statistical features are extracted from the obtained EMs. Afterwards, the extracted features along with the three-phase current measurement are input to three different LSTM network to obtain exact fault type, phase, and location information. Finally, a trip signal based on the obtained fault information is generated to disconnect the faulty portion from the rest of the MG. The significant feature of the proposed NIPS is that it does not need adaptive relaying and communication networks. Moreover, it is independent of the operating scenario and hence fault current magnitude. To evaluate the efficacy of the proposed NIPS, exhaustive simulations are performed on an international electro-technical commission (IEC) MG. The simulation results confirm the efficiency of the proposed NIPs in terms of accuracy, dependability, and security. Moreover, comparisons with existing intelligent protection schemes validate that the proposed NIPS is highly accurate, secure, and dependable.

Impact of Transformer Topology on Short-Circuit Analysis in Distribution Systems with Inverter-Based Distributed Generations

Distributed energy resources (DERs), recently introduced into distribution systems, are mainly inverter-based distributed generations (IBDGs), which have different short-circuit behaviors from conventional synchronous-based distributed generations (SBDGs). Hence, this study presents a comprehensive analysis of the short-circuit behaviors of distribution systems with IBDGs, based on sequence networks and superposition, from the perspectives of interconnected transformers, and observes the flow of zero-sequence fault currents with different transformer topologies. Moreover, two- and three-winding transformers with various bank connection types and groundings are investigated. It was concluded that the transformer topology and its grounding influence the fault current contribution in zero-sequence networks, and the high penetration of IBDGs alters the fault current magnitude and phase angles.

Numerical calculation and experimental verification of subtransient- and transient reactances of a pumped storage machine

The subtransient reactance Xd′′ and transient reactance Xd′ of large-capacity alternators are crucial parameters to determine the fault current magnitude and design the protection system for the machine. The traditional calculation method of Xd′′ and Xd′ will bring errors in the graphical decomposition process which depends on the subjective judgement of different individuals, and the analytical method is also inherently imprecise. In this paper, the superconductor simulation method (SSM) incorporated with field-circuit coupled finite element model is presented. The SSM has high accuracy and is capable of considering the saturation effect, skin effect and arbitrary structure of the machine. The unsaturated and saturated values of Xd′′ and Xd′ of a pumped storage machine are calculated with the proposed SSM. The method of establishing the field-circuit coupled model, governing equations and the superconductor simulation method are introduced in detail. The short-circuit test is conducted on the real machine and the calculated results of both Xd′′ and Xd′ are verified by the measured values.

Implementing Symmetrical Structure in MOV-RCD Snubber-Based DC Solid-State Circuit Breakers

This article deals with metal-oxide varistor (MOV) and resistor–capacitor–diode (RCD) snubber-based solid-state circuit breakers (SSCBs). There are two main contributions. First, a design methodology of MOV-RCD snubber parameters is proposed by considering thermal dissipation and snubber charging time for the first time. The thermal profile of the main conduction switches determines nominal current under passive cooling. Based on the nominal current, the fault current magnitude is derived, and a design method of key parameters of an MOV-RCD snubber is proposed. Four snubbers are designed with different fault currents and dc voltages. Second, symmetrical layouts with distributed parallel cells are proposed for high current capability, which enables scalability. Q3D simulations facilitate the evenly distributed stray inductances among paralleled branches. Both low- and medium-voltage SSCBs are implemented, ranging from 500 V/300 A to 2 kV/1 kA. The power density achieves 37.8 kW/L at 500 V/1 kA. Experiments demonstrate that the reverse voltage reaches 4.88 kV with an ultrafast interruption speed of 24 μs for 2 kV/1.144 kA fault current including the MOV conduction time interval.

Metal Oxide Varistor Design Optimization and Main Breaker Branch Switch Control of a Progressively Switched Hybrid DC Circuit Breaker

In this article, metal oxide varistor (MOV) design optimization and switching control in the main circuit breaker (MCB) branch of a progressively switched hybrid dc circuit breaker (DCCB) is presented. A progressively switched hybrid DCCB can achieve faster fault isolation with reduced peak fault current magnitude and transient recovery voltage compared with a regular hybrid DCCB due to its modified switching strategy. Consequently, thermal stress on the semiconductor devices in MCB is significantly reduced. Analytical model of the system dynamics during fault isolation with progressive switching is derived to demonstrate the switching scheme’s effect on the energy-absorbing component, MOV, during turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> process. Derived analytical model in conjunction with the displacement curve of the fast mechanical switch of the hybrid DCCB is utilized to optimize the components of the main circuit breaker branch to reduce MOV degradation through asymmetric energy dissipation. A model of the circuit breaker is built in PSCAD to validate the performance of the proposed optimization method in a 10-kV/250-A system with four stage progressive switching. Additionally, a low voltage system model at 380 V is developed in PLECS for two stage progressive switching that works as the basis of experimental validation. This includes both lookup table-based MOV model and device thermal model for junction temperature estimation. Experimental results are provided for a 380-V system to demonstrate reduced fault current peak in a progressive switching and near uniform energy absorption in optimally selected MOVs.

Modified Complete Ensemble Empirical Mode Decomposition based HIF detection approach for microgrid system

Detection of high impedance fault (HIF) in an active distribution system is a challenging task. It is learned from the fault characteristics that detection and discrimination of HIF during different critical conditions is impossible using the fault current magnitude. Under dependable situations such as energization of a transformer, nonlinear load and capacitor bank detection and discrimination of HIF is challenging. In a distribution system with an inverter based distributed generator (IBDG), the current contribution during islanding mode is very low and also for HIF condition. To mitigate these issues, an intelligent approach applying Modified Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (MCEEMDAN) on residual current signal is developed. The second intrinsic mode function (IMF2) is extracted using MCEEMDAN and its Teager Kaiser Energy Operator (TKEO) is computed to detect and discriminate the HIF against other physical events. The novelty of MCEEMDAN approach lies with its noise free output and faster response as compared to other time–frequency approaches. The method is tested for several fault and non-fault cases including, presence of noise, harmonics, and unbalance loadings. The comparison with recently reported techniques for very HIF and ungrounded system proofs the efficacy of the method.

An Enhanced Differential Protection Scheme for LVDC Microgrid

The low-voltage dc (LVDC) microgrid possesses numerous benefits and their penetration in the power system has increased rapidly in recent years. However, the detection of faults in the LVDC microgrid is a challenging issue due to the large magnitude of fault currents and fault-level variation in the microgrid. The performance of the recent current and its derivative-based protection scheme is limited in case of faults in the islanding mode of operation, different microgrid topologies, varying distributed generations (DGs) penetration, and against the measurement noise. This article presents an enhanced differential protection scheme for LVDC microgrid integrated with multiple DGs and storage. The differential current and its first derivative are processed through the decision tree (DT) algorithm for fault detection and the K-nearest neighbor (KNN) technique is utilized for fault classification. The robustness of the proposed protection scheme is tested for different fault types and fault conditions with variation in microgrid topology and operating conditions. The impact of the intermittent and volatile nature of the DGs, the presence of measurement noise, and assessment during external faults and critical no-fault cases have been investigated. The proposed scheme is tested on the MATLAB/ SIMULINK and validated on the Typhoon HIL platform for the assessment of real-time performance. The test results show that the proposed scheme can detect and classify faults with high accuracy and faster response time and, thus, can be a potential candidate for providing dependable protection measures for LVDC microgrids.