Time-Domain Protection and Fault Location of Wye-Connected Shunt Capacitor Banks Using Superimposed Current and Differential Voltage

This paper presents protection and fault location of wye-connected shunt capacitor banks used in medium or high voltage applications. The proposed method is sensitive to single element failure obtained by using voltage adaptive instantaneous superimposed current in each phase. The change in equivalent reactance computed using time-domain signals is used to find the number of failed capacitor element and types of fault. The location of the faulted capacitor is identified using sign of the voltage difference of the lower and upper halves of the shunt capacitor bank. The performance of the proposed method is tested for various cases including identical faults, simultaneous faults, system voltage unbalance in both single and double wye-connected shunt capacitor banks. The method is also validated using field data collected from a 400 kV SCB for an internal fault. The proposed technique is compared with available methods and found accurate

Adaptive zone-1 setting following structural and operational changes in power system

Change in the network structure or operating condition in a power system affects the impedance as calculated by the distance relay during fault. Such changes may lead to malfunction of the distance relay at times. In this paper, an adaptive distance relay setting method using local data is proposed to prevent zone-1 malfunction following structural and operational changes. The performance of the proposed adaptive setting method is tested on a 39-bus New England system and a generic 12-bus power system using PSCAD/EMTDC simulation data, and a comparative assessment is also provided

Adaptive distance protection for lines connecting converter-interfaced renewable plants

Fault ride through compliance as imposed by grid codes prevents undesirable disconnection of renewable plants from the network even during fault. Diversified control schemes adopted in the converters associated with such plants modulate the voltage and current output significantly during a fault. This varies the fault characteristics of the renewable plant at times and thereby affects the performance of the distance relay protecting lines connected to such plants. In this article, a distance protection method using local data is proposed for transmission lines connecting renewable plants. The proposed method calculates the phase angle of faulted loop current by determining the pure-fault impedance of the renewable plant at every instant following fault detection, irrespective of the control scheme associated with the plant. Utilizing the information, it calculates the line impedance up to fault point accurately. Performance of the proposed adaptive protection method is tested on renewable-integrated modified 39-bus New England system using PSCAD/EMTDC simulated data and found to be accurate. Comparative assessment with the conventional distance relaying technique reveals its superiority

Adaptive fault type classification for transmission network connecting converter-interfaced renewable plants

Fault ride through compliance as imposed by the grid codes (GCs) prevents the inadvertent disconnection of the renewable plants from the network even during faults. Control algorithms applied in the converters associated with such plants modulate the fault characteristics significantly and result in malfunction of available fault type classifiers at times. In this article, an adaptive fault type classification technique is proposed for transmission network connecting converter-interfaced renewable plants. The method calculates sequence current angles in the faulted loop by determining pure-fault impedance of the plant at every instant during fault using local voltage and current data for fault type identification. The proposed method is tested for different fault situations on renewable integrated standard systems using PSCAD/EMTDC. The performance of the proposed method is found to be accurate in the presence of different types of renewable plants and complying different GC requirements. Comparative assessment reveals its superior performance

A Cosine Similarity Based Centralized Protection Scheme for DC Microgrids

Unlike the phasor measurement based protection in AC systems, the protection of DC systems deals with complex fault transients which mandates the isolation of the faulted segment within few milliseconds as continued fault current leads to overheating issue in power electronic converters. To this end,several works have been suggested based on unit and nonunit protections for DC microgrids. Threshold selection and protection coordination are the challenges associated with nonunit protection. Similarly, communication delay and link failure limit the application of unit protection. To address these issues, this paper presents a robust centralized protection scheme for DC microgrids, which is resilient to communication delay and link failure. It uses current of each line segment to compute the similarity of current change at both ends of the line segment to derive the protection decision. To overcome the communication failure from one end of the line segment or even from multiple segments, the proposed method uses data from adjacent segments to derive the protection decision correctly. Using PSCAD/EMTDC environment, the performance of the proposed method is evaluated for various cases and compared with available techniques. Finally, the accuracy of the protection algorithm is validated under experimental conditions

Assessment of Premutation in Myotonic Dystrophy Type 1 Affected Family Members by TP-PCR and Genetic Counseling

Myotonic dystrophy type 1 (DM1) is caused by the expansion of an unstable CTG repeat located in the 3′-UTR of (DMPK) the DM protein kinase gene. Patients with DM1 have expansions of greater than 50 repeats and up to many thousands. In the present study we aimed to evaluate the utility of TP-PCR in diagnostics as well as the assessment of premutation carriers in proband families. Twenty-seven DM1 cases were enrolled (from twenty-six families) and the 13 families of these cases came forward for family screening. The patient group constitute 22 males and 5 females and the average age of onset was 32.8 years (range 17 to 52). All clinically diagnosed DM1 cases and their family members DNA samples were analyzed by TP-PCR. All the cases were found to be positive for the CTG repeat expansion. Among those five families, four had at least an asymptomatic carrier. In the remaining one family other than the proband none was found to be neither affected nor asymptomatic. We reconfirmed the utility of PCR based screening for DM1 as being reliable and rapid molecular test and it should be used as an initial screening test for all patients with DM and their family members for initial screening purpose

Non-unit protection of parallel lines connecting solar photovoltaic plants

Fault current control by solar plant converters introduces different fault characteristics compared to conventional synchronous generator-based systems resulting in numerous issues to the available protection methods. In this article, the issues with conventional distance relaying is analyzed while protecting parallel lines connecting solar plant to grid and a new protection method is proposed using local voltage and current data. The proposed nonunit protection method derives positive sequence reactive powers for both lines for different solar plant operating conditions and uses their difference to ensure correct zone-1 protection. For faults during single circuit operation, the method includes an additional scheme comprising of instantaneous zero-sequence overcurrent check and delayed distance relaying to derive correct protection decision. Performance of the proposed nonunit protection method is tested for parallel lines connecting the solar plant in a 39-bus test system for different situations using PSCAD/EMTDC simulated data and found to be accurate. Comparative assessment reveals the high reliability of the proposed method

Adaptive unit protection for lines connecting large solar plants using incremental current ratio

Control schemes in a solar plant complying with different grid codes modulate the output voltage and current significantly during the fault. In this article, the issue with conventional current differential approaches for the line connecting the large solar plant is analyzed and a new protection technique using both end incremental current phasors is proposed. The proposed method uses two criteria to identify the internal faults in such connectivity. The first criterion is based on the ratio of both end incremental phase current phasors, and the second one uses the magnitude ratio of positive sequence incremental currents. Both the criteria are adaptive to line terminal currents and complement each other enriching the method applicable for any system condition. The performance of the proposed method is tested for different internal and external fault cases and found to be accurate. The compatibility of the proposed method is also validated using a real-time simulator. Comparative assessment with conventional current differential techniques reveals the superiority of the proposed approach

Line protection challenges and its mitigation in a new grid scenario

A noticeable transformation in the power network fault characteristics is being observed with the large-scale integration of renewable sources. Control operations associated with renewable plant interfacing converters challenge the available line protection schemes, especially for lines integrating such sources to the grid. Such an issue with available distance protection for lines interconnecting renewable sources is addressed here with a solution, especially for zone-1 operation. Two indices are formulated in the proposed method using local end current and voltage data to ensure correct zone-1 decision. Proposed method is assessed for its performance for different fault situations in a 39-bus New England system with renewable integration and the results are accurate. Comparative analysis with conventional distance protection schemes indicates the strength of the proposed method