A Comprehensive Overview on Modified Versions of Stockwell Transform For Power Quality Monitoring

Abstract

The increasing trends toward the accurate identification of power quality disturbances (PQD) via power quality (PQ) monitoring require an appropriate digital signal processing (DSP) technique and a robust classifier. To this end, Stockwell transform (ST), one of the most efficient feature extraction DSP tools, and its several variants play an utmost role in PQ assessment framework. Its time-varying spectral characteristics generally extract the local instantaneous frequency spectrum from the global temporary behavior of PQD signal. However, the Standard ST suffers from thepoor time-frequency resolution because of its frequency-dependent Gaussian window (GW). While the analysis of the statistically time-varying signals requires a suitable balance between time and frequency resolution. To this end, this paper provides a comprehensive literature review on several modified versions of Standard ST for the first time to reduce the computational complexity of the algorithm as well as maximize the energy concentration of the timefrequency plane. A comparative analysis of all the modified STs has been presented in tabular form to provide the key characteristics of each technique. Additionally, a case study has been presented to substantiate the highest accuracy of the proposed algorithm over the other ST variants. Apart from the PQD classification, miscellaneous applications of Standard ST and its modified variants have been indicated. This review paper may provide a valuable resource to the researchers for further improvement of the timefrequency resolution of ST not only in classifying PQD but also for its other wide applications.INDEX TERMSEnergy concentration, power quality monitoring, power quality disturbance, Stockwell transform, time-frequency analysis.

Synthesis of S-(5-aryl-1,3,4-oxadiazol-2-yl) O-alkyl carbonothioate and alkyl 2-((5-aryl-1,3,4-oxadiazol-2-yl)thio) acetate, and their antimicrobial properties

“…All protons chemical shifts of compounds (10)(11)(12)(13)(14)(15) fully correspond to their structure: substances (10-12), 0.92 ppm (3H, t, CH3), 1.65-1.67 (2H, sextet, CH2CH3), 4.10-4.11 (2H, s, S-CH2), 4.13-4.14 (2H, t, -OCH2) and substances (13)(14)(15), 1.25-1.26, 1.26-1.28 ppm (6H, d, -CH(CH3)2), 4.07-4.08 (2H, s, S-CH2), 5.07-5.08 (1H, septet,-CH(CH3)2). At the same time, the signals of protons of aromatic groups in all compounds (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) were observed in the range of 7.32-8.05 ppm, which are familiar for these groups.…”

“…In the IR spectra of compounds (4-15) there are characteristic absorption bands of the C(O)OR (R=alkyl) group at 1725-1788 cm -1 . The absorption maximum (272-286 nm) of all synthesized compounds (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15) in the UV spectra corresponded to the literature data for S-derivatives (16)(17)(18), which shows that the interaction proceeds exclusively in the S-center to obtain S-(5-aryl-1,3,4-oxadiazol-2-yl) O-alkyl carbonothioate (4-9) and alkyl 2-((5-aryl-1,3,4oxadiazol-2-yl)thio)acetate (10)(11)(12)(13)(14)(15). The possible N-products were not detected neither by TLC method, nor by spectral data ( 1 H NMR, UV-spectroscopy).…”

“…A wide interest in the chemistry of derivatives of 5-substituted-1,3,4-oxadiazole-2-thiones is associated with a broad variety of biological and physiological activities exhibited by their derivatives. Recently, numerous works on synthesis and biological activities such as antibacterial, antifungal, antiviral, anticonvulsant, anti-inflammatory, antitumor of 5-substituted-1,3,4-oxadiazole-2-thione derivatives were reported (1)(2)(3)(4)(5)(6)(7)(8)(9)(10). A distinctive structural feature of 5-aryl-1,3,4-oxadiazol-2thiones is the presence of an ambident thioamide group NH-C=S in their molecule, therefore, depending on the nature of the attacking electrophilic agent, derivatives can be obtained at the exocyclic sulfur atom, and on the endocyclic nitrogen atom or simultaneously on both reaction centers (S-or N-).…”

Self-Calibration Sensor for Contactless Voltage Measurement Based on Dynamic Capacitance

“…As shown in Figure 1, on the basis of Part A and Part C, a transformation unit B is added. When the switch is turned to a, the voltage output by the sensor can be expressed as shown in Equation (3). When the switch is turned to b, the voltage output by the sensor can be expressed as shown in Equation (4):…”

“…Technologies such as power metering, power equipment maintenance, power quality monitoring, and substation area optimization and transformation are continuously advancing with the national level of urban and rural power construction. The sensing and detection of electrical quantities play a pivotal role in the above application scenarios [1][2][3]. Recently, in the field of electrical quantity sensing and detection, there are relatively mature noncontact measurement methods for current, such as using a Roche coil or Hall sensor to measure the magnetic field around the wire to obtain wire current [4,5].…”