Conventional Protection Schemes Research Articles

One-Class Classifier Based Fault Detection in Distribution Systems With Varying Penetration Levels of Distributed Energy Resources

The integration of Distributed Energy Resources (DERs) into distribution systems greatly increases the system complexity and introduces two-way power flow. Conventional protection schemes are based upon local measurements and simple linear system models, and are thus not capable of handling the new complexity and power flow patterns in systems with high DER penetration. In this paper, we propose a data-driven protection framework to address the challenges introduced by DERs. Firstly, considering the limited available data under fault conditions, we adopt the Support Vector Data Description (SVDD) method, a commonly used one-class classifier, for distribution system fault detection, which only requires the normal data for its training process. Secondly, incremental learning is incorporated into the proposed SVDD-based protection framework to accommodate variations of the integration level of DERs in distribution systems over time. In particular, the artificial uniform-hyperspherical data generation model is incorporated into the incremental SVDD to boost the training speed. Finally, we validate the proposed method under the IEEE 123-node test feeder. Simulation results demonstrate that our proposed SVDD-based fault detection framework significantly improves the robustness and resilience against DERs in comparison with conventional protection systems. Meanwhile, the proposed online updating model outperforms the existing incremental SVDD models in terms of successful training speed.

Non-Communication Based Time-Current-Voltage Dual Setting Directional Overcurrent Protection for Radial Distribution Systems With DG

This paper proposes a novel protection scheme equipped with time current voltage dual setting directional overcurrent relays for radial distribution systems with (distributed generation) DG without the need of communication assistance. The proposed protection scheme is formulated as a nonlinear programming problem where the main objective is to determine the optimal relay forward and reverse settings to minimize the relay overall operating times. The proposed scheme, based on the time current voltage dual settings directional overcurrent relay, is applied to the IEEE 33-bus radial distribution system with synchronous-based DG and its performance is compared against the conventional protection schemes that rely on both standard overcurrent relays and time current voltage directional overcurrent relays (proposed in the literature). The results show that, for radial distribution systems, the proposed scheme is capable of mitigating protection coordination failure due to DG reverse fault currents (a limitation in overcurrent relays), does not require communication (a limitation for meshed distribution systems) and does not require additional relays (a limitation in directional overcurrent relays) and thus making such relays more suitable for protecting radial distribution systems with DG.

High Impedance Fault Detection using Advanced Distortion Detection Technique

A High Impedance Fault (HIF) in the power distribution systems remains mostly undetected by conventional protection schemes due to low fault currents. Apart from degrading the reliability of power supply to customers, HIF can impose a high cost on the utilities due to technical damages. The nonlinear and asymmetric nature of HIF makes its detection and identification very challenging. HIF signatures are in the form of minute-level distortions in the observable AC sinusoidal voltage and current waveforms but these signatures do not follow a clear pattern. In this paper, we present Advanced Distortion Detection Technique (ADDT), based on waveform analytics to distinguish and detect HIF. In addition, the ADDT analysis provides a fair assessment about the location and severity of HIF for efficient decision-making at the DSO level. ADDT is computationally lightweight and can be implemented in actual relays, hence it is enabled to provide an easy and cost-effective solution to HIF detection issues. ADDT robustness is tested in several simulation cases of interest using the IEEE-34 and IEEE-13 distribution test feeder systems in RTDS power system simulator. The test results successfully demonstrate the effectiveness and robustness of ADDT.

Trends in the protection of inverter‐based microgrids

The study reviews the current trends in the protection of inverter-based microgrids. This topic is currently given significant attention, as the inverter-interfaced distributed generation is likely to become dominant in microgrids. Since low fault current is a well-known signature of microgrids, the emphasis is on the complicated fault characteristics in inverter-based microgrids, bearing in mind that low-magnitude fault current and complicated fault responses are inter-related. The fault characteristics are rooted in the inverter controllers that can control inverter voltages and currents during the fault period such that they are completely different from the conventional fault characteristics. Given that these differences could impact conventional protection schemes, challenges to different elements of fault identification, i.e. fault detection, fault polarisation, and faulted phase selection in microgrids are separately addressed in detail. The existing preliminary solutions that define the current trends are discussed and gaps are identified accordingly. The review classifies techniques into three categories: modified classical techniques, heuristic techniques, and differential-based techniques. The explanations are supported by simulation case studies to provide clarification. The purpose is to provide the current status of microgrid protection and assist in developing new effective solutions to protect these grids.

Synchrophasor Measurement-Assisted System Integrity Protection Scheme for Smart Power Grid

Rapid penetration of novel cutting-edge technologies into power grids has paved a way for new opportunities besides challenges. Though the conventional system integrity protection schemes (SIPS) are performing well, they may not be adequate for the high-end protection of smart power grid (SPG) due to increasing complexity. This paper proposes a synchrophasor measurement-assisted SIPS method for the high-end protection of SPG. It employs synchronized voltage and current phasor data, acquired at phasor data concentrator (PDC) of wide-area supervisory protection system (WASPS) from all phasor measurement units (PMU), to detect the disturbance, identify disturbed area and locate the sensitive region (SR). Further, the proposed scheme classifies fault and stressed conditions using the estimated peak time (Tp_est) and time of settling (Ts_est) from the voltage phasor oscillations. The functioning of the proposed method has been illustrated through various case studies carried on Kundur’s two-area model. Furthermore, the efficacy of the proposed method has been validated on the New England IEEE-39 bus system in MATLAB/Simulink environment. The results show that the proposed method is efficient in enhancing the system integrity protection (SIPS) and situational awareness (SA) in SPG. In addition, it improves the protection system reliability (PSR).

Initial travelling wavefront‐based bus zone protection scheme

A high-speed busbar protection scheme based on initial travelling wavefronts is presented in this study. The aerial mode current travelling waves (TWs) across all lines connected to the busbar are calculated using Karenbauer transformation. Thereafter, the polarity and magnitude of wavelet transform modulus maximas of line current appearing after fault inception are analysed for fault zone and faulty phase identification. Its performance has been evaluated by modelling an existing 750 kV Indian substation in PSCAD/EMTDC software package. The simulation results reveal that the proposed scheme provides better stability for external faults and higher reliability in case of internal faults in comparison with conventional low-impedance busbar differential protection scheme (87B). Moreover, it remains immune to the current transformer saturation problems. In the end, comparative evaluation of the proposed scheme with the existing busbar protection schemes proves its superiority in terms of stability against external faults, sensitivity for internal faults, computational obligations, and communication requirements.

Effective algorithm for fault discrimination and estimation of fault location in transmission lines

Sensitivity, selectivity, speed of operation and reliability of the conventional current differential protection schemes are affected and limited by the distributed shunt capacitance of high-voltage long transmission lines. In this study, a new pilot protection algorithm has been proposed based on the computation of change in shunt line admittance ‘Y’ during dynamic conditions using synchronised data. Therefore, it does not require a separate compensating technique to nullify the effect of line charging current in the fault detection. This scheme can quickly discriminate the internal faults and also detects the faulty phase. Also, it has an advantage of estimation of an accurate fault location. The performance of the proposed algorithm is evaluated on 400 kV, 50 Hz two-bus system as well as IEEE-39 bus 345 kV system using EMTDC/PSCAD and MATLAB simulation tools. The simulation results confirm the proposed algorithm can effectively discriminate the faults, independent of fault location, fault resistance, type of fault, series compensation lines and source impedance. Finally, a hardware experiment using National Instruments (NI) based LabVIEW platform is carried out to check the practical feasibility of the proposed algorithm.

A New Differential Protection Scheme for Busbar Using d–q–0 Transformation

This paper presents a new differential protection scheme for busbar using d–q–0 transformation. The proposed method is based on derivation of operating and restraining currents by utilizing direct axis (d) component of current transformer (CT) secondary current signals of all bays. The dual slope relay characteristic (derived from the operating and restraining current) of the proposed scheme operates in conjunction with a CT saturation detection algorithm and hence, provides better stability during external faults with CT saturation. The performance of the proposed scheme has been evaluated by modeling a 400 kV sub-station with two different busbar configurations, namely Breaker-and-Half configuration (BHC) and single breaker double-bus configuration (SBDBC) in PSCAD/EMTDC software package. The proposed algorithm has been tested for various fault cases with diversified system and fault parameters. The proposed scheme is highly sensitive against in-zone faults even with a considerable value of fault resistance as the average fault detection time remains within one-and-half cycle. At the end, a comparative evaluation of the proposed scheme with the conventional bus differential protection scheme (87B) clearly indicates its superiority in terms of stability against close-in out-of-zone faults with CT saturation and sensitivity for high impedance internal faults.

Combined DFT and Fuzzy Based Faulty Phase Selection and Classification in a Series Compensated Transmission Line

The conventional distance protection scheme malfunctions sometimes in case of a fixed series capacitor compensated transmission line due to the change in relaying impedance of the protected line during faulty conditions. In order to mitigate this problem, a combined discrete Fourier transform and fuzzy (CDFTF) based algorithm has been proposed in this paper. This method has been tested on a 400 km, 735 kV series compensated transmission line network and WSCC 3-machine 9-bus system for all fault types using MATLAB/Simulink and PSCAD platforms, respectively. A fixed series capacitor is located at the middle of the protected line. The fundamental components of phase currents, phase voltages, and zero-sequence current are fed as inputs to the proposed scheme. The fault detection, faulty phase selection, and fault classification are achieved within 1/2–1 cycle of power frequency. The proposed CDFTF-based scheme is less complex and is better than other data mining techniques which require huge training and testing time. Test results corroborate the proposed scheme reliability with wide variations in fault location, fault resistance, fault inception angle, evolving faults, compensation level, and heavy load interconnection. The results discussed in this work indicate that the proposed technique is resilient to wide variations in fault and system conditions.

Enhancing the reliability of protection scheme for PV integrated microgrid by discriminating between array faults and symmetrical line faults using sparse auto encoder

The ever increasing power demand and stress on reducing carbon footprint have paved the way for widespread use of photovoltaic (PV) integrated microgrid. However, the development of a reliable protection scheme for PV integrated microgrid is challenging because of the similar voltage-current profile of PV array faults and symmetrical line faults. Conventional protection schemes based on pre-defined threshold setting are not able to distinguish between PV array and symmetrical faults, and hence fail to provide separate controlling actions for the two cases. In this regard, a protection scheme based on sparse autoencoder (SAE) and deep neural network has been proposed to discriminate between array faults and symmetrical line faults in addition to perform mode detection, fault detection, classification and section identification. The voltage-current signals retrieved from relaying buses are converted into grey-scale images and further fed as input to the SAE to perform unsupervised feature learning. The performance of the proposed scheme has been evaluated through reliability analysis and compared with artificial neural network, support vector machine and decision tree based techniques under both islanding and grid-connected mode of the microgrid. The scheme has been also validated for field applications by performing real-time simulations on OPAL-RT digital simulator.

A New Hybrid Fault Identification Method Based on Multiterminals Synchronous Measure Information for All Parallel at Traction Power Supply System

The all parallel autotransformer (AT) traction power supply system (TPSS) including several subsections is widely used for high-speed railways. Unfortunately, any fault of catenary and negative feeder will cause all subsections power interruption in the whole system. Moreover, due to the nonlinear relationship between the distance and impedance as well as the symmetry of the system, conventional distance protection schemes fail to identify the fault subsection and the fault types. In this paper, a novel segmental power supply scheme is presented, which can switch the catenary and negative feeder at each AT subsection on and off independently. Based on the theoretical analysis of the electrical characteristics of the traction power network, multiterminals synchronous information is applied and a hybrid fault identification method is proposed, which can accurately identify the fault subsection and fault type. Consequently, only the catenary or negative feeder at the fault subsection will be quickly removed from service without the effect on normal operation of other subsections. Therefore, the reliability of all parallel AT TPSS is improved considerably. This method was verified through simulation and laboratory experiments by the case studies.

Wide area monitoring and protection of microgrid with DGs using modular artificial neural networks

The prominence of incorporating the renewable energy resources in a power system via microgrids has increased in the recent years, which impose a caution on conventional protection schemes. Protection schemes proposed earlier use local measurements, but fault classification for selective phase tripping using wide area measurements for microgrid has not been reported so far. This paper presents a wide area monitoring and protection of microgrid with distributed generations (DGs) using modular artificial neural networks (MANNs) for the fault detection and classification without affecting the relays in non-faulty or healthy sections of the microgrid. The distinct characteristics of the microgrid sort the proposed methodology into two stages. In stage 1, ANN 1 is developed to identify the operating mode of microgrid, whether it is operating in grid-connected mode (GCM) or islanded mode (IM). In stage 2, there are two MANNs corresponding to GCM and IM. Each MANNs consists of three separate ANNs for fault detection, classification, and section identification. A standard IEC 61850-7-420 microgrid with DGs (wind and photovoltaic) penetration is modeled in MATLAB/Simulink. The three-phase voltages and currents are measured with time synchronization considering the microphasor measurement units located at each bus. The extensive study includes different simulation scenarios such as shunt faults, high impedance fault, and dynamic situations like connection/disconnection of DGs/distribution lines. The results confirm the efficacy of the proposed methodology.

Application of distance protection in mixed overhead‐underground distribution feeders with distributed generation

This study applies distance protection to real mixed overhead-underground distribution feeders, as an alternative to conventional overcurrent protection schemes. The efficiency of the proposed distance-based protection scheme is examined both in the radial (normal state) and in the looped operation of the distribution feeders. Moreover, distributed generating units of various types are assumed connected to the feeders to investigate their effect on the efficiency of the protection scheme. The latter proved sufficient to coordinate properly with the other protection means in the system, following a fuse-blowing philosophy, providing reliable protection to the lines.

A Virtual Multi-Terminal Current Differential Protection Scheme for Distribution Networks With Inverter-Interfaced Distributed Generators

The deployments of inverter-interfaced distributed generators (IIDGs) in medium voltage distribution networks may cause undesirable trips or tripping failures of conventional two-terminal current differential protective relays. It is economically and technically unfeasible to reconfigure large numbers of time-synchronized sampling clocks and communication channels for each terminal inside the protected zone. In this paper, a more accurate IIDG mathematical equivalent model is established that considers the control strategies of IIDG, and the profile characteristics of the positive-sequence voltage at each point of common coupling are investigated. Then, a real-time estimation algorithm is introduced for the fault current contribution of grid-connected IIDGs. On this basis, this paper proposes a novel virtual multi-terminal current differential protection scheme. This scheme only necessitates exchanging the electrical quantities between the protective relays at both terminals via an existing two-terminal pilot channel, thus reducing the cost and requirements for communications. The feasibility of the proposed protection is demonstrated in both the PSCAD/EMTDC simulation platform and the RTDS hardware experimental laboratory. A comparison of the proposed protection alongside the conventional protection is also presented. Test results indicate that the proposed protection is widely applicable to various fault conditions, thereby improving the sensitivity and selectivity of conventional protection schemes.

Discrimination of Inrush, Internal, and External Fault in Power Transformer Using Phasor Angle Comparison and Biased Differential Principle

Conventional protection scheme of power transformer maloperation during abnormalities such as inrush condition, current transformer (CT) saturation during external fault and high resistance internal fault conditions. This article presents inrush detection based on an average angle of 2nd order derivative of differential current. The magnitude and phase angle of primary and secondary currents are estimated using a Modified Full Cycle Discrete Fourier Transform (MFCDFT) algorithm. Normally, during an internal fault, the differential current is well above the restraining current; however, the same condition arises during external fault with heavy CT saturation. Hence, a phase angle comparison based scheme is combined with percentage biased differential protection. During an internal fault, the phase angle difference of primary and secondary current is <90°, whereas it differs >90° for any external fault conditions. In the proposed scheme, 315 MVA, 400/220 kV transformer is considered for validation of various fault conditions simulated in PSCAD™ software. Moreover, the proposed scheme is validated on developed laboratory prototype of 2 kVA, 230/115 V single phase transformer using ATmega328 microcontroller. The proposed algorithm is effectively validated on both, simulation and hardware to discriminate inrush, internal and external fault by considering various system and fault parameters.

Classification of Many Abnormal Events in Radial Distribution Feeders Using the Complex Morlet Wavelet and Decision Trees

Monitoring of abnormal events in a distribution feeder by using a single technique is a challenging task. A number of abnormal events can cause unsafe operation, including a high impedance fault (HIF), a partial breakdown to a cable insulation, and a circuit breaker (CB) malfunction due to capacitor bank de-energization. These abnormal events are not detectable by conventional protection schemes. In this paper, a new technique to identify distribution feeder events is proposed based on the complex Morlet wavelet (CMW) and on a decision tree (DT) classifier. First, the event is detected using CMW. Subsequently, a DT using event signatures classifies the event as normal operation, continuous and non-continuous arcing events (C.A.E. and N.C.A.E.). Additional information from the supervisory control and data acquisition (SCADA) can be used to precisely identify the event. The proposed method is meticulously tested on the IEEE 13- and IEEE 34-bus systems and has shown to correctly classify those events. Furthermore, the proposed method is capable of detecting very high impedance incipient faults (IFs) and CB restrikes at the substation level with relatively short detection time. The proposed method uses only current measurements at a low sampling rate of 1440 Hz yielding an improvement of existing methods that require much higher sampling rates.

Impact of Power-Electronic Sources on Transmission Line Ground Fault Protection

Power-electronic sources, such as Type 3 wind turbine generators and static synchronous compensators (STATCOM), interface to the grid through, partial- or full-scale, and power converters that have inherently fast switching capability to control their output current during short circuits. The short-circuit current is a function of the specific converter control algorithm and differs significantly from the conventional rotating machine sources without converter interfaces. Therefore, if a transmission-line protection scheme is designed for conventional sources, (not taking into account these differences in short-circuit current characteristics), reliability can be at risk. Using real-life short-circuit currents on lines supplied by sources having a power converter interface, this paper illustrates the reliability risk to conventional line protection schemes, in particular, to those which use negative-sequence quantities for the detection of unbalanced faults. This paper discusses the protection schemes, adopted by BC Hydro–a large Canadian Electric Utility, for transmission lines interconnecting Type 3 wind turbine and STATCOM sources. Their application for ground faults is independent of the converter control algorithm as long as the source is interconnected to the grid via a transformer which is a source of zero-sequence current.

A Dynamic Resilience Approach for WDM Optical Networks

AbstractOptical fibres have been developed as a transmission medium to carry traffic in order to provide various services in telecommunications platform. Failure of this fibre caused loss of data which can interrupt communication services. This paper has been focused only on survivable schemes in order to guarantee both protection and restoration in WDM optical networks. In this paper, a dynamic resilience approach has been proposed whose objective is to route the flows in a way which minimizes the total amount of bandwidth used for working and protection paths. In the proposed approach, path-based protection is utilized because it yields lower overhead and is also suitable for global optimization where, in case of a single link failure, all the flows utilizing the failed link are re-routed to a pre-computed set of paths. The simulation results demonstrate that proposed approach is much more efficient as it provides better quality of services (QoS) in terms of network resource utilization, blocking probability etc. as compared to conventional protection and restoration schemes. The proposed approach seems to offer an attractive combination of features, with both ring like speed and mesh-like efficiency.

Power transformer differential protection using current and voltage ratios

The main challenge in transformer protection is to find a fast and efficient differential relay algorithm that isolates the transformer from the system causing least damage. Algorithm should also avoid mal-operation while differentiating between the operating conditions. This paper presents an improved differential protection scheme for power transformer. The proposed scheme is based on the ratio of the absolute difference and absolute sum of the primary and secondary currents of each phase, supplemented by the ratio of the absolute difference and absolute sum of the primary and secondary terminal voltages of each phase. The proposed algorithm aims at avoiding mal-operation, possible with the conventional three-phase transformers differential protection scheme due to transient phenomena, including the magnetic inrush current, simultaneous inrush with internal fault, and faults with current transformer saturation. Investigation of the proposed differential protection scheme using both current and voltage ratios shows that it can provide fast, accurate, secure and dependable relay for power transformers.

A fast time-frequency response based differential spectral energy protection of AC microgrids including fault location

This paper proposes a pattern recognition based differential spectral energy protection scheme for ac microgrids using a Fourier kernel based fast sparse time-frequency representation (SST or simply the sparse S-Transform). The average and differential current components are passed through a change detection filter, which senses the instant of fault inception and registers a change detection point (CDP). Subsequently, if CDP is registered for one or more phases, then half cycle data samples of the average and differential currents on either side of the CDP are passed through the proposed SST technique, which generates their respective spectral energies and a simple comparison between them detects the occurrence and type of the fault. The SST technique is also used to provide voltage and current phasors and the frequency during faults which is further utilized to estimate the fault location. The proposed technique as compared to conventional differential current protection scheme is quicker in fault detection and classification, which is least effected from bias setting, has a faster relay trip response (less than one cycle from fault incipient) and a better accuracy in fault location. The significance and accuracy of the proposed scheme have been verified extensively for faults in a standard microgrid system, subjected to a large number of operating conditions and the outputs vindicate it to be a potential candidate for real time applications.