Differential Protection Scheme Research Articles

A new differential protection scheme based on Synchro-squeezing transform applied to AC Micro-Grid

In recent years, the protection of a microgrid has been a substantial challenge. This paper performs a differential protection scheme for the micro-grid based on Synchro-Squeezing Transform (SST). The proposed scheme protects the micro-grid in different modes i.e. islanded or grid-connected mode. Also, it is investigated in the ring and radial configuration. In the proposed scheme, currents on two sides of the line are measured by current transformers (CTs), and then differential current (IDiff) is calculated. This current is applied to extract the absolute value of the summation of the square root (ASSR). In this stage, transient and external faults without CT saturation and different switching such as connected or disconnected load/capacitor/distributed generation are detected from different internal faults. In the next stage, the frequency components of SST (FCSST) are extracted. By this feature, external fault and cross-country fault with CT saturation are detected. The proposed scheme is evaluated in noisy conditions, fault in different section of line with high resistance fault (HRF), and high impedance faults (HIF) of line. The micro-grid is simulated in PSCAD/EMTDC by various distributed generation (DG) like wind generation and photovoltaic systems penetrated at different buses. The proposed protection scheme is coded in MATLAB. The simulations represent the proposed protection scheme is correctly discriminate external and internal faults. At the same time, the method is immune to CT saturation and cross-country faults.

Differential protection scheme for distribution network with distributed generation based on improved feature mode decomposition and derivative dynamic time warping

With the progress of communication technology, the cost of optical fiber and 5G continues to decrease, and data transmission becomes more convenient and fast, making it possible to realize differential protection of distribution network by various intelligent algorithms using signal waveforms. Aiming at the problem that the traditional relay protection device can not meet the actual demand when the single-phase ground fault occurs in the distribution network with distributed generation, this paper proposes a new differential protection scheme. The characteristic mode decomposition improved by the whale optimization algorithm is used to decompose the zero-sequence current waveform collected at both ends of the line. Based on the basic principle of current differential protection, the derivative dynamic time warping of the component with the largest fault feature can effectively solve the problem that the grounding current of the distribution network cannot meet the working requirements of the differential protection device, and ensure the safe and stable operation of the system. Finally, based on MATLAB software, the performance of this method is comprehensively evaluated by simulating different fault conditions, so as to ensure the feasibility and accuracy of this method in the case of diversified faults when the distributed generation is used as part of the power supply.

Reference Phasor-Based Data Self-Synchronization Scheme for Line Current Differential Protection in Active Distribution Networks

Reference Phasor-Based Data Self-Synchronization Scheme for Line Current Differential Protection in Active Distribution Networks

Using sampled values in line differential protection – Analyzing the scheme feasibility and protection performance under communication stress scenarios

Line differential protection features great selectivity to isolate equipment under fault conditions. However, this technique has been limited by factors such as transmission line length, communication network delay, use of proprietary protocols, or vulnerability to network failures. The IEC 61850 standard enables the implementation of digital substations, which have proven to be a good option for improving the reliability and efficiency of the electrical system. In this sense, we propose a new scheme for differential protection in transmission lines using SV messages by the IEC 61850 standard. In addition, we carry out a feasibility for differential protection in two 500 kV transmission lines of the Brazilian interconnected system using the Aspen Oneliner software. We evaluate the communication performance of the proposal in a testbed with two SEL 421–7 protection relays capable of sending and receiving SV messages, an Omicron CMC 356 test case, a PTP signal distributor device SEL-2488, an SEL-9524/GNSS antenna, switches for proper formation of communication buses, and hardware to emulate the length of the transmission line communication channel, generate concurrent traffic injection, and also induce package loss scenarios for the SV messages. The results are promising and indicate the viability of the proposal.© 2017 Elsevier Inc. All rights reserved.

Application of Discrete Wavelet Transform and Chebyshev Neural Network for Differential Protection of Indirect Symmetrical Phase Shift Transformer

The Indirect Symmetrical Phase Shift Transformer (ISPST) stands out from a power transformer due to its combination of electrically connected and magnetically coupled circuits. Hence in this work, an intelligent differential protection algorithm, based on Discrete Wavelet Transform (DWT) and Chebyshev Neural Network (ChNN), is proposed as main classifier to discriminate internal fault and inrush. Half cycle thee phase post fault differential current is considered for the proposed algorithm. PSCAD/EMTDC software is utilized to simulate different operating conditions of ISPST, resulting in the simulation of a significant amount of internal faults and inrush cases. The algorithm under consideration has undergone extensive evaluation across numerous cases, resulting in an accuracy rate exceeding 99%. The results indicate that the classifier based on DWT - ChNN yields extremely promising results, even when dealing with a noisy signal, current transformer (CT) saturation, and varying ISPST ratings. Superiority of the proposed algorithm is also compared with Multilayer Perceptron (MLP), Radial Basis Function Neural Network (RBFNN) and Probabilistic Neural Network (PNN) based approaches under the same conditions and it is found that proposed classifier is the most efficient and rapid among all alternative classifiers for the differential protection scheme of an ISPST under the considered conditions.

Interoperability Challenges in Multivendor IEC 61850 Devices for Parallel Power Transformer Differential Protection

Interoperability of GOOSE messages is essential for the proper operation of protection schemes such as the parallel power transformer (PTRF) differential protection scheme, especially when using multivendor IEC 61850 devices. GOOSE messages allow for fast and reliable communication between intelligent electronic devices (IEDs) and are based on Ethernet communication. To ensure the interoperability of GOOSE messages between multivendor devices, adherence to the IEC 61850 standard specifications is crucial. The standard defines the format and content of GOOSE messages, including the data object model, data types, and communication protocols. Third-party testing and certification programs can also ensure compliance with the standard and help guarantee interoperability between different vendors. Device conformance with these standards does not ensure interoperability when devices from various manufacturers are utilized. Interoperability is necessary between the relevant devices from various vendors to provide system power stability and protection. If multivendor device interoperability is achieved, power utilities will be able to utilize multivendor devices in substations. The study investigates and provides comprehensive methods for achieving IEC 61850 standard-based interoperability problems in parallel with PTRF’s current differential protection schemes between IEDs (SEL-487E and MiCOM-P645) produced by different vendors under fault conditions. In a lab-scale environment with RTDS for real-time simulation in Hardware-in-the-Loop (HIL), the designed technique is simulated and tested.

Adaptive Quasi-Power Differential Protection Scheme for Active Distribution Networks

With the massive integration of distributed generations (DGs), distribution networks gradually become more active and flexible. Conventional overcurrent protection is difficult to adapt to such active distribution networks (ADNs). Current differential protection (CDP) is a good choice for solving this issue, but the multi-branch structure of ADNs especially the unmeasured T-connected load branch affects the protection’s sensitivity. Therefore, the paper proposes a quasipower differential protection (QDP) scheme based on Tellegen’s theorem. First, the feasibility of applying Tellegen’s theorem to ADNs was analyzed. On this basis, reasonable protection criteria were designed for different scenarios of ADNs. Then, an adaptive protection scheme was established, which can automatically adjust the criteria depending on the presence of Tconnected branches within the protected section. Finally, extensive simulations were carried out in an ADN model using PSCAD/EMTDC software. The simulation results demonstrate that the proposed protection scheme has excellent adaptability to network topologies, fault types, fault resistances, and network structures of ADNs.

A Current Differential Protection Scheme for Distribution Networks with Inverter-Interfaced Distributed Generators Considering Delay Behaviors of Sequence Component Extractors

The high-level proliferation of inverter-interfaced distributed generators (IIDGs) in modern distribution networks (DNs) has changed system topologies and fault current signatures, which compromises the protective relays in DNs. Investigating IIDG fault behaviors-based protection scheme will benefit the grid’s safety and stability. This paper proposes a novel current differential protection (CDP) scheme that considers the delay behaviors of positive- and negative-sequence component extractors for IIDGs in DNs. A frequency-domain analytical model of the fault current for a grid-connected IIDG with the PQ control strategy and a low-voltage ride-through (LVRT) capability is investigated. The dynamic behavior of the IIDGs considering the sequence-component extractor based on the Pade approximation is presented, where the T/4 delay extractor of the IIDGs causes a two-stage behavior in the fault transient process. It is found that a 5 ms error between the measured and actual values after the fault will affect the transient characteristics of the IIDGs. The transient current generated by the IIDGs during grid faults contains a large number of low-order harmonic components within the range of 0–200 Hz, which is significantly different to the current provided by the power grid. Therefore, the proposed CDP scheme uses protective relays at both terminals to obtain the required transient electric quantity using the Prony method. By constructing the frequency-characteristics ratio (FCR) and the exchanging FCR between two terminal relays, the developed protection criteria are implemented. The accuracy of the fault analysis method, whose maximum computational error is below 0.1%, and the feasibility of the proposed protection scheme are demonstrated by using a 10 kV DN in a PSCAD/EMTDC simulation, which can be applied to various fault conditions and traditional DNs without IIDGs.

An entropy-based scheme for protection of DC microgrids

The design of an appropriate scheme for protection of DC microgrids is still a significant challenge. This paper proposes a new method for protection of DC microgrids when subjected to various types of faults and modes of operation. The proposed method shares some features of the differential protection scheme and adopts the Shannon entropy to evaluate the "informational value" of current waveforms in the presence and absence of a fault. It uses the relative entropy of the current waveforms at the two sides of the faulty line to detect and characterize a fault. In the case of failure in the primary protection system, the entropy variations of the current waveforms are used to detect the faulty line. The main features of the proposed method include a) accuracy in a noisy environment with poor data synchronization (due to the delay in communication links) and varying network topology, b) fast operation regardless of the fault type and location, c) ability to detect high-impedance faults, and d) provision of backup protection. The efficiency of the proposed method is demonstrated by comparing the simulation results of several case studies in a typical ring DC network with those obtained using an advanced differential protection scheme.

Entropy-driven differential privacy protection scheme based on social graphlet attributes

Entropy-driven differential privacy protection scheme based on social graphlet attributes

Novel Differential Protection for a Powerformer Considering Capacitive Current Compensation

A Powerformer is a special type of generator whose peak capacitive current is approximately 30 times larger than that of conventional generators with the same rated apparent power. Powerformer stator fault relays may be misoperated by using conventional differential protection strategies, thus degrading network reliability. Therefore, a novel differential protection scheme for a Powerformer is proposed in this paper. First, the nonlinear distribution laws of the Powerformer stator winding capacitance and induced electromotive force (EMF) are analyzed. Next, an equivalent distributed parameter circuit model of the Powerformer considering cable-windings with graded insulation is established and verified by using FEM-based analysis. Furthermore, to eliminate the influence of the capacitive current on the differential protection, the capacitive current is analyzed, and a novel differential protection scheme considering capacitive current compensation is proposed. A simulation model is established by using MATLAB and PSCAD, and extensive simulation studies verify the effectiveness of the proposed protection approach.

Time domain differential protection scheme applied to power transformers

This paper presents a new differential protection scheme for power transformers based on Intrinsic Time-Scale Decomposition (ITD) and Ensemble of Bagged Tree (EBT) as a classifier. The ITD decomposes the input nonstationary signal into Proper Rotation Components (PRCs) and a monotonic trend signal. In the proposed scheme, statistical time-domain features extracted from the ITD output are fed to the EBT classifier, which classifies different events, including internal fault, internal fault combined with inrush current, different inrush currents (energizing transformer, sympathetic, and recovery inrush current), and external fault. The combination of ITD and EBT tools requires only a limited sample of post-fault data to protect the transformer. The proposed scheme is tested under various operating conditions to confirm its accuracy, and the effect of current transformer (CT) saturation on the scheme's performance is evaluated. The scheme is immune to noisy conditions and does not require transformer parameters. The power systems were simulated using PSCAD/EMTDC and MATLAB software.

Phase-angle adaptive current differential protection for active distribution network

With the distributed generator to be attached to the distribution network, the current differential protection scheme may have some problems, resulting in maloperation or rejection of protection. This paper investigates the current distribution properties of an active distribution network with branches of undetected load and draws the conclusion that undetected load may cause differential protection maloperation. The differences in fault properties of differential protection in transmission network scenarios and distribution networks containing distributed generator are evaluated, leading to the conclusion that differential protection applied to active distribution networks may have reduced resistance to transition resistance and that poor signal synchronization conditions in distribution networks may lead to larger synchronization errors. A phase-angle adaptive current differential protection is proposed. It adaptively adjusts the phase angle constraint using the magnitude of the power frequency full current component proportion at both sides of the line. It can accommodate the protection needs of various operation modes of distribution networks containing distributed generator, and has the characteristics of strong resistance to transition resistance and strong phase shift braking ability. The correctness of the suggested protection scheme was verified using the PSCAD platform.

Power Differential Protection for Transformer Based on Fault Component Network

Current differential protection has been widely used as the primary protection of transformers. However, inrush currents during transformer energization can cause misoperation of the protection when the second harmonic restraint algorithm fails. This paper proposes a power differential protection scheme based on the fault component network (FCN), which is free from inrush detection and computationally cheap. First, the fault component differential power (FCDP), defined as the differential active power of a transformer in the FCN, is analyzed under different conditions. Second, a transformer protection scheme is presented based on the FCDP and the traditional differential power. A removal algorithm of decaying direct current (DDC) offset is developed to accurately estimate the FCDP. The performance of the scheme is tested under various conditions, including internal faults, external faults and transformer energization. The simulations using PSCAD, and Real Time Digital Simulator (RTDS), experiments in the Electrical Power Dynamic Laboratory (EPDL) and real recording data validate that the proposed method can protect the transformer reliably.

A novel differential protection scheme for AC microgrids based on discrete wavelet transform

A novel differential protection scheme for AC microgrids based on discrete wavelet transform

Amplitude Based Pilot Protection for Transmission Line

Abstract: Distance protection and differential protection schemes are the two primary types of protection schemes employed in gearbox line protection today. However, industrial practice has shown that commonly used gap prevention techniques are limited in tripping speed and selectivity. The timing of the samples in each of the two relays located at the gearbox line terminals also affects the differential protection mechanism. On the other hand, pilot safety schemes using only the communication link to exchange local decision-making about fault conditions are not affected. These method include protection of Extra High Voltage (EHV) and Ultra High Voltage (UHV) transmission lines. Synchronization of time. The problem of creating a fast and accurate fault detection system for the safety of EHV/UHV transmission lines, which is crucial in present power systems, is the subject of this master's thesis. The protection method described in this thesis is the foundation for the detection and analysis of waves travelling wave along transmission at fault initiation. This method compares the arrival of the first traveling waves at both ends of the protected line with respect to direction. This will establish whether the fault is located in the safe zone or not. Based on high voltage transmission network safety requirements a suitable phase sequence algorithm is developed to control single phase tripping. Finally, through simulations conducted in the MATLAB environment, practical design concerns for incorporating the newly proposed protection algorithm into a numerical relay unit are investigated.

Injection Harmonic Current Differential Protection Based on Control-Protection Synergy for Distribution Networks with IBDGs

The high penetration of inverter-based distributed generations (IBDGs) leads to traditional distribution networks’ complex and variable fault characteristics. Traditional passive detection protection methods can hardly meet the stability and reliability requirements. To solve this problem, an injection harmonic current differential protection (IHCDP) scheme based on the idea of control-protection synergy is proposed in this paper. By analyzing the circuit structure, control strategy, low-voltage-ride-through characteristics of IBDGs, and short-circuit currents provided by IBDGs, an injection-control strategy of characteristic harmonic currents (CHCs) based on the d-axis and q-axis is proposed. According to the change of short-circuit currents provided by the IBDG, the amplitude of CHCs is adaptively corrected to strengthen the fault characteristics and ensure that the distribution network harmonic injection protocols are always satisfied. An IHCDP criterion based on the distortion rate of the negative-sequence component of CHCs is proposed by analyzing the fault characteristics of the CHCs after injection. To effectively eliminate the dead-zone problem during symmetrical short-circuit faults, the proposed IHCDP utilizes the distortion rate of A-phase CHCs. The feasibility of the proposed protection scheme is demonstrated by the theoretical analysis and simulation results in this paper.

Superimposed current based differential protection scheme for AC microgrid feeders

Legacy protection schemes face numerous challenges with the emergence of microgrids. Due to the complex controls, the fault responses in microgrids differ from conventional behaviour and vary with the operation mode. In this paper, a differential protection scheme based on fundamental frequency superimposed current phasors is proposed for microgrid feeders. The phasors are extracted using dq components instead of conventional Fourier algorithms. The performance of proposed method is tested for different fault scenarios by carrying out simulations in MATLAB/SIMULINK software. The results confirm that internal faults are detected in a few milliseconds. At the same time, the scheme remains insensitive to external faults with CT saturation and other system disturbances. The proposed scheme is unaffected by the microgrid mode of operation, direction of power flow and DG type.

Empirical Wavelet Transform-Based Differential Protection Scheme for Micro-Grid

Empirical Wavelet Transform-Based Differential Protection Scheme for Micro-Grid

Power supply arm protection scheme of high-speed railway based on wide-area current differential

When fault occurs on cross-coupling autotransformer (AT) power supply traction network, the up-line and down-line feeder circuit breakers in the traction substation trip at the same time without selectivity, which leads to an extended power failure. Based on equivalent circuit and Kirchhoff’s current law, the feeder current characteristic in the substation, AT station and sectioning post when T–R fault, F–R fault, and T–F fault occur are analyzed and their expressions are obtained. When the traction power supply system is equipped with wide-area protection measurement and control system, the feeder protection device in each station collects the feeder currents in other two stations through the wide-area protection channel and a wide-area current differential protection scheme based on the feeder current characteristic is proposed. When a short-circuit fault occurs in the power supply arm, all the feeder protection devices in each station receive the feeder currents with time stamp in other two stations. After data synchronous processing and logic judgment, the fault line of the power supply arm can be identified and isolated quickly. The simulation result based on MATLAB/Simulink shows that the power supply arm protection scheme based on wide-area current differential has good fault discrimination ability under different fault positions, transition resistances, and fault types. The verification of measured data shows that the novel protection scheme will not be affected by the special working conditions of the electrical multiple unit (EMU), and reliability, selectivity, and rapidity of relay protection are all improved.