Digital Protection Scheme Research Articles

A novel digital protection scheme for microgrid

A novel digital protection scheme for microgrid

Reverse Blocking Over Current Busbar Protection Scheme Based on IEC 61850 Architecture

Substation Automation System (SAS) is currently in a matured state of technology that shall facilitate transformational changes from conventional protection scheme. IEC 61850 protocol is considered as the crux of digital SAS due to its multifunction features that include seamless communication, ability to integrate various intelligent electronic devices, potential for improved real-time condition monitoring, reliable protection, and control of critical electrical assets. Because the application of IEC 61850 in SAS is relatively new and has not fully implemented in many substations yet, further feasibility studies using multivendor equipment to assess its performance under different operating conditions is imperative. In this article, a practical reliable and efficient reverse blocking over current bus bar protection scheme based on IEC 61850 is implemented and tested. Also, a comparison of digital SAS and conventional protection scheme is presented to highlight the superiority of the former one. Experimental results attest the reliability and effectiveness of the proposed digital protection scheme along with the accuracy and security of transmitting data packets using sampled values and generic objective-oriented substation event communication protocols adopted by IEC 61850.

Short Video Copyright Storage Algorithm Based on Blockchain and Expression Recognition

Blockchain technology is widely used in the field of digital right protection technology. The traditional digital right protection scheme is not only inefficient and highly centralized but also has the risk of being modified. Due to its own characteristics, blockchain cannot completely store all the original files of digital resources. In this paper, a convolutional neural network algorithm based on visual priority rule is proposed (CNNVP). This algorithm can recognize facial expressions in the original files of digital resources (for short video of face class). The algorithm extracts facial expression features accurately and makes these features form log files that can represent the original files of digital resources. Then, the paper proposes a short video copyright storage algorithm based on blockchain and facial expression recognition and stores the log file into the blockchain. The above methods not only improve the efficiency of short video copyright storage, reduce the degree of storage centralization, and eliminate the risk that copyright is easy to be modified. Moreover, the computing operation of deep learning technology on short video not only ensures the privacy of storage certificate information but also ensures the possibility of blockchain storage of video information. Experiments show that the algorithm proposed in this paper is more efficient than the traditional copyright storage method. Moreover, the algorithm proposed in this paper can provide technical support to the media resource management department.

Simple algorithm for fault detection, classification and direction discrimination in power systems based on digital current signals processing

A power system suffers from unexpected various faults, which needs smart devices for accurate estimates of fault detection, classification and direction discrimination to provide inspection, maintenance, and repair of the actual faults. Signal processing-based protection technique can be used to detect the disturbances of the measured signals. This paper presents a digital protection scheme, based on three indices derived from the three-phase input and output current signals of the protected equipment, to detect current disturbances, classify faults, discriminate fault directions, select faulty phase(s), define current unbalances, and identify CT saturation extent. Moreover, it develops a new closed-tripping characteristic with a quadrilateral form for differentiating the fault location (internal/external) with respect to the element protection zone. A power system simulation is carried out using ATP platform, and the technique performance is validated via MATLAB software. Extensive simulation case studies show that the proposed algorithm provides a fast relay response and high accuracy under various operating and fault conditions. It is able to perform successfully the function of fault diagnosis within one periodic cycle. Besides, it responds very well with regard to dependability, security, stability and sensitivity. In addition to that it has the ability to recognize the saturated and unsaturated secondary current signals, measured using the current transformers, in the cases of internal and external faults.

A multipurpose image watermarking scheme for digital image protection

A multipurpose digital image watermarking scheme is proposed based on the multiple LSB bit substitution method. Fragile and robust watermarks are embedded into the host image for tamper and ownership detection respectively. Randomized insertion is used to insert a fragile watermark pattern to get better tamper detection. Secret keys are used in this scheme to secure data from forged/unauthorized access, which must be known to the end user to extract the watermark from the host. Tampering is done at random locations to cover most of the watermarked image’s area during testing of proposed scheme. Due to blind nature and randomized watermark insertion, high security is obtained. Experimental outcomes represent that the proposed method is able to achieve significant tamper detection. Proposed scheme exhibits robust nature towards common signal processing attacks and provides distortion-less robust watermark in case of no attack. This method also exhibits less execution time due to its time domain insertion methodology. A comparative analysis with the existing schemes shows that the proposed scheme has many features simultaneously such as blind extraction, high embedding capacity, low execution time, significant robustness, acceptable imperceptibility, and multipurpose nature. The proposed scheme can be utilized in fields where rapid response, ownership protection, and tamper detection are prime concerns.

Evaluating the Performance of Digital Modular Protection for Grid-Connected Permanent-Magnet-Generator-Based Wind Energy Conversion Systems With Battery Storage Systems

This paper develops and tests a new method for managing the responses of multiple digital relays employed in interconnected permanent-magnet generator (PMG)-based wind energy conversion systems (WECSs) with battery storage. The developed method utilizes digital relays (modules), each of which provides protection for a specific location of the PMG-based WECS and battery storage. The outputs of the developed digital protection scheme are trip signals to operate circuit breakers in PMG-based WECS, battery storage, and point-of-common-coupling. The modular digital protection is implemented for experimental testing on a 5-kW PMG-based WECS that has a 2.3-kW battery storage. Test results show that the developed protection can offer fast, accurate, and reliable responses to faults occurring in different parts of the tested WECS and battery storage. In addition, test results show that the modular digital protection has minor sensitivity to the location of faults, charge/discharge cycles of the battery storage, and/or levels of power delivery to the host grid.

A Random Forest Classifier-based Digital Protection Scheme for Busbar

This paper presents a random forest (RF) classifier-based digital protection scheme which provides an effective discrimination between internal and external faults on a busbar. The measured current signals of all the bays (lines) connected to a busbar have been used as feature vectors. The system and fault parameters have been varied to generate a wide variety of simulation cases (33,600) consisting of both internal and external faults. By giving post-fault data of one cycle duration of all the bay currents as an input to the RF classifier, and taking only 30% of the total data (33,600) for training and remaining 70% of the total data for testing, an accuracy higher than 98% has been obtained. The PSCAD/EMTDC software package is used to model a prevailing 400-kV Indian busbar system for the purpose of authentication of the presented technique. The presented technique successfully differentiates between internal faults and external faults and remains unaffected against the change in system and fault parameters. In addition, the proposed scheme maintains stability under the Current Transformer saturation phenomena particularly during a heavy-through fault. A comparative analysis of the proposed scheme with the recently proposed scheme using support vector machine classifier clearly shows its superiority.

A Comprehensive Digital Protection Scheme for Low-Voltage Microgrids with Inverter-Based and Conventional Distributed Generations

Microgrid (MG) protection is one of the main challenges in proliferation of microgrids. Due to limited fault current feeding of inverter-based distributed generations (DGs), in islanded operation of MG, protection problems become more complicated; and, therefore, conventional protection strategies cannot be applied. Hence, new protection methods that are applicable in islanded and grid-connected modes of operation are necessary. In this paper, a comprehensive digital-relay based protection is introduced for the protection of MGs. The proposed method includes protection of lines, distributed generations, and the point of common coupling. The structure and graphical schematic of the proposed digital relays are also presented. The proposed method is independent of the MG operation mode and benefits from single-phase tripping. In this method, due to fault isolation from both sides of a line, downstream loads and DGs can operate after fault clearance. To demonstrate the effectiveness of the proposed protection method, numerous simulations are carried out on an MG test system in the PSCAD/EMTDC environment.

Digital Content Protection in Cloud Environments using Near Field Communication

In the cloud environment, the digital content accessed by the user is mostly stored in the server. Thus, it needs to prevent malicious persons from modifying information and faking the users identity to obtain the digital content. In addition, in the cloud computing environment, it is required to consider the storage space and computing performance problems for the mobile device. In this paper, a secure and efficient NFC identity authentication and digital content protection scheme is proposed. We use an NFC tag to store the security token and other related parameters, and put the tags in a protected environment in order to prevent it from being damaged or tampered by malicious persons. Through the NFC side-channel, a user needs to near the NFC tag to access the security token. In addition, we use the challenge-response protocol and the message authentication code to achieve mutual authentication, and generate the session key to protect the transmitted digital content.

Smart grid fault detection and classification with multi‐distributed generation based on current signals approach

Smart grid (SG) containing clean distributed generation (DG) has gained intensive research for reliable digital protection against fault conditions. The main objective of this study is to develop and validate a fast and efficient fault detection and classification algorithm taking into account the dynamic behaviour of DG units. The proposed algorithm does not require additional measurements as it based only on the synchronised measured three-phase currents through the communication facilities available in SG. The advanced communication technologies in SG are currently utilised for efficient and real-time data transfer from the protective relays to the monitoring and protection centre. The transferred data are processed for fault diagnosing before taking the necessary trip actions. In the proposed algorithm, the statistical cross-alienation coefficients are calculated for the measured current signals at sending and receiving ends of each feeder. Fault detection and classification process will be achieved taking into account the changes in the synchronised and discretised waveform of current signals within a movable window of (1/4 cycle). The proposed algorithm is tested on real system to detect and classify the different fault condition. The results indicated that the proposed technique is fast and reliable for SG digital protection schemes.

Development and Testing of a New Modified Discrete Fourier Transform-based Algorithm for the Protection of Synchronous Generator

A novel full-cycle modified discrete Fourier transform-based digital protection scheme for generators is presented in this article. A laboratory setup has been developed to cater various abnormal and faulty situations applicable to a scaled generator. It includes utility supply, motor-generator set, synchronizing panel, current transformers/potential transformers (CTs/PTs), digital storage oscilloscope, and 3-phase variable load. A control circuit has also been developed comprised of a proposed algorithm, auxiliary relay, and circuit breaker (contactors). The proposed scheme depends on phasor values of modal voltage (Vmod) and current (Imod) derived by the algorithm in MATLAB® software. The outcome of the proposed modified discrete Fourier transform-based protection scheme is compared with the numerical relay (available in the laboratory), which has an inbuilt fast Fourier transform/discrete Fourier transform (FFT/DFT)-based algorithm. Various conditions, such as overload, over/under voltage, over/under frequency, ground fault, reverse power, and loss of excitation, have been simulated in the laboratory for the validation of the proposed scheme. Due to finer characterization of the fundamental signal derived by the proposed algorithm compared to numerical relay, it successfully detects and sends a trip signal for all types of abnormal/faulty conditions. The experimental results confirm the satisfactory operation of the proposed algorithm in the developed laboratory prototype.

Experimental results and technique evaluation based on alienation coefficients for busbar protection scheme

Abstract In modern digital power protection systems, statistical coefficients technique is recently used for fault analysis. An alienation technique is developed for busbar protection against all ten types of shunt faults, which may locate in busbar protection zone, under different loading levels, fault resistances and fault inception angle. It does not need any extra equipment as it depends only on the three-line currents measurements, of all feeders connected to the protected busbar, which are mostly available at the relay location. It is able to perform fault detection, fault confirmation, faulty phase selection and determine the fault location in about a half-cycle period. Thus, the alienation technique is well suited for implementation in digital protection schemes. The technique is efficient to detect current transformer saturation conditions without needing any additional algorithm. The effects of DC components and harmonics are eliminated with estimation of alienation coefficients. The proposed scheme is applied for an experimental circuit. LABVIEW program and MATLAB package are used to implement the proposed technique.

A Semi-Blind Robust DCT Watermarking Approach for Sensitive Text Images

This paper presents a new approach to address the challenges associated with integrity verification, proof of authenticity, tamper detection and assurance of copyright protection for digital images propagated online. In particular, the problem addressed here primarily relates to the protection of sensitive online textual images that may be targeted for counterfeiting or intentional/unintentional modifications which would result with a fake copy being disseminated. Typically, sensitive text images are characteristic of further challenges and constraints on embedding/extraction techniques compared to their more general digital picture/image counterparts. With many digital protection schemes addressing the problem of less-sensitive content comprising of a rich set of colours and textures, this paper proposes a novel watermarking approach for the case of sensitive text images in order to confirm content originality and integrity verification under some known constraints of the image type. Hence, a new approach based on discrete cosine transform and linear interpolation is proposed and applied on digital Quran text images, which are considered as ideal samples of content with stringent sensitivity requirements. Detailed results had presented the significance of this approach and had demonstrated the high robustness obtained when faced with various attack scenarios that include rotational attacks, JPEG compression attacks, noising attacks and median filtering attacks. Significantly, a major contribution of this paper was found in the novel watermark extraction approach which had enabled perfect watermark extraction under a range of attack scenarios. Finally, a significant advantage of the proposed approach was found in its broad applicability for authentication and protection of other sensitive and less-sensitive digital image content.

Protection Scheme for Transmission Lines Based on Correlation Coefficients

In modern digital power system protection systems, statistical coefficients technique is recently used for fault analysis. A correlation technique is developed for faults detection and discrimination. The proposed technique is able to accurately identify the condition of phase(s) involved in all ten types of shunt faults that may occur in extra high-voltage transmission lines under different fault resistances, inception angle and loading levels. The proposed technique does not need any extra equipment as it depends only on the three line-currents measurements which are mostly available at the relay location. This technique is able to perform the fault detection, type and phase selection in about a half-cycle period. Thus, the proposed technique is well suited for implementation in digital protection schemes. The suggested scheme is applied for a part of 500 Kv Egyptian network. Alternative transient program (ATP) and MATLAB programs are used to implement the proposed technique.

Busbar Protection Scheme Based on Alienation Coefficients for Current Signals

In modern digital power system protection systems, statistical coefficients technique is recently used for fault analysis. An alienation technique is developed for busbar protection against all ten types of shunt faults, which may locate in busbar protection zone, under different loading levels, fault resistances and fault inception angle. It does not need any extra equipment as it depends only on the three-line currents measurements, of all feeders connected to the protected busbar, which are mostly available at the relay location. It is able to perform fault detection, fault confirmation, faulty phase selection and determine the fault location in about a half-cycle period. Thus, the alienation technique is well suited for implementation in digital protection schemes. The technique is efficient to detect current transformer saturation conditions without needing any additional algorithm. The effects of DC components and harmonics are eliminated with estimation of alienation coefficients. The proposed methodology is applied for a part of 500 KV Egyptian network. Alternative transient program (ATP) and MATLAB package are used to implement the proposed technique.

Research of Lossless Digital Watermarking Technology

The digital map is an important and indispensable resource to the national strategic security and social economic development. At the present, needs to focus on resolving the utility question of digital vector map copyright protection technology, furthermore, the information hiding technology is the basic content of the research areas of the digital vector maps copyright protection. It is proposed a digital copyright protection scheme, based on the principle of unauthorized cannot resume, copyright embedding operation selection partly transform for the map content. Processing area determined by the spatial clustering analysis method that is based on grid density.

Location of Faults In Transmission Line Using Fast Fourier Transform And Discrete Wavelet Transform In Power Systems

This paper demonstrates the usage of fast fourier transform and wavelet transform in locating faults using a simple transmission line. Transmission lines connect the generating stations and load centers. Hence, the chances of fault occurring in transmission lines are very high. Signal processing is the most important part of the digital distance protection schemes. The proposed model effectively helps in locating the fault such as L-G,LL,LL-G,LLL using MATLAB/SIMULINK. In doing so it describes the method of analysis of above two transforms in SIMULINK environment using the above two transforms. MATLAB simulation results show the wavelet method of transforms is a good and powerful tool to estimate the disrupts location on the transmission line when fault occurs.

Protection scheme for transmission lines based on alienation coefficients for current signals

In modern digital power system protection systems, statistical coefficients technique is recently used for fault analysis. An alienation technique is developed for faults detection and discrimination. The proposed technique is able to accurately identify the condition of phase(s) involved in all ten types of shunt faults that may occur in extra high-voltage transmission lines under different fault resistances, inception angle and loading levels. The proposed technique does not need any extra equipment as it depends only on the three line-currents measurements which are mostly available at the relay location. This technique is able to perform the fault detection, type and phase selection in about a half-cycle period. Thus, the proposed technique is well suited for implementation in digital protection schemes. The proposed methodology is applied for a part of 500 KV Egyptian network. Alternative transient program and MATLAB programs are used to implement the proposed technique.

Wavelet-based Relaying Scheme for Tapped Transmission Line

A wavelet-based digital protection scheme for a tapped transmission line is presented in this article. As the wavelet packet transform provides more detailed and accurate signal decomposition than the discrete wavelet transform, proper discrimination can be achieved between the forward and reverse faults on extra-high voltage tapped lines. The idea of the proposed scheme depends on deriving an ADD signal using wavelet packet transform coefficients that are proportional to the fault current at each terminal. Due to the finer characterization of current signal, the proposed wavelet-based digital relaying scheme has successfully distinguished high resistance fault. Verification of the proposed technique has been done in the field as well as on simulated data of an existing part of an Indian system (UKAI-KAKRAPAR 400-kV tapped transmission line) using a PSCAD/EMTDC software package. The relay has shown satisfactory performance under various fault conditions, especially for high-resistance faults and also for reverse faults in the case of weak sources. This article concludes with a comparative study in the form of simulation between the existing scheme and the proposed scheme by analyzing different fault and system conditions.

Novel Methods for High-Impedance Ground-Fault Protection in Low-Voltage Supply Systems

Many high-impedance ground faults (HIGFs) that happen in low-voltage (LV) systems often cause customer supply loss, fire, and human safety hazards. Traditional ground-fault protection is provided by the residual current circuit breaker (RCCB). The RCCB is usually employed in an analogue measuring circuit and often causes nuisance tripping due to capacitive leakage current and load-switching operations. It offers only ground fault protection to a certain extent and has difficulty in detecting HIGFs associated with a dielectric material defect. In this paper active power variation–based protection for HIGFs is developed, and a dissipation factor (DF)–based criterion for identifying load-switching operation is proposed. They are implemented by cross-correlation analysis between phase voltage and residual current in single-phase networks. A digital protection scheme is also designed. EMTP simulation results show that the new protection can remove the influences of capacitive leakage current and load-switching operations and is able to detect HIGFs and prevent electric shock with high sensitivity and robustness.