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Power transformer is one of the most important high voltage apparatus in any power system network. The life span of such apparatus commonly relies upon its insulation condition. The primary reason for an insulation breakdown is partial discharge. Partial discharges (PDs) are electrical discharges that happen in the insulation system of the transformers. Occurrence of PDs results in deterioration of the transformer insulation system. Hence, measuring and detecting the PD at an initial stage is necessary to avoid complete breakdown of the transformer. Currently, various PD detection and measurement methods, such as, electrical, chemical, acoustic, UHF and optical methods are being used for PD monitoring in power transformers. The conventional PD monitoring techniques like electrical or chemical have some limitations. The optical Fiber Bragg Grating (FBG) Sensor has been used as a PD sensor for PD monitoring in the power transformer to overcome these issues. This paper presents a review of FBG sensors’ application as a sensor for PD monitoring in an oil-filled power transformer. The challenges and future prospects in this area are also discussed.

Caenorhabditis elegans embarks on a quiescent dauer state upon exposure to unfavourable conditions and can sustain for a very long period without food, but it returns to continuous life cycle upon arrival of suitable conditions. Thus, dauer state plays a critical role in its adaptive fitness and survival. ATP-independent endoribonuclease activity of XRN-2 has been implicated in dauer microRNA metabolism, perturbation of which causes their collapse within a very short span of time. Here, we present a detailed comparative analyses of dauer transcriptomes from a conditional mutant strain for the endoribonuclease activity of XRN-2, maintained under control and experimental conditions. We observed that even a limited disruption of microRNA homeostasis in experimental dauers results in deregulation of a large number of mRNA targets. Our bioinformatic analyses, supported by morphological, physiological, and behavioral evidence further demonstrate critical changes in metabolism leading to a state unsupportive of dauer maintenance, alongside potential defects in multiple neuronal activities, which might have caused an overall disruption of dauer plasticity. We explore a possible role of this endoribonuclease activity towards the maintenance of chromatin architecture and transposon expression that in turn might affect the transcriptional program critically required for the maintenance of non-aging, long-lived dauers. Finally, we also demonstrate that perturbation of the endoribonuclease activity during the dauer state exerts drastic adverse effects on the continuity of life cycle after dauer-exit. They not only fail to recapitulate the wild type events of germline development and embryogenesis, but also present traits of very old worms and formation of ‘tumor-like’ structures in the proximal gonad.

Anthropogenic activities affect the rivers and the entire basin in different dimensions. All the river basins including Ganga and Damodar are polluted from unplanned anthropogenic activities. This ...

The installation of distribution transformers in environmentally sensitive areas is a growing concern of electric utilities, and everywhere it sees a strong local resistance. Special and costly measures must be taken to address this concern, for example, by reducing the risk of transformer oils being inadvertently released into the environment. To solve this problem, promising natural esters based on edible oil-seeds were studied in the last few decades to ascertain their suitability based on industry-recognized standards. Some common natural esters available today in the transformer oil market are mostly produced from seeds of soybean, rapeseed, sunflower, and others [1–5]. However, due to the inherent disadvantage of high pour point, coconut oil has been sidelined for many years. Recent research on the coconut oil indicates that this can be used as a dielectric liquid at a distribution level transformer in a tropical region. Unlike main seed oil, the use of coconut oil in a transformer has not yet started despite its superior dielectric and physicochemical properties. It is a totally biodegradable and edible vegetable oil. Prototype transformers filled with coconut oil are in operation in Sri Lanka since 2001 where it has been studied satisfactorily by the researchers [6]. The superior oxidation stability, non-toxicity, and good dielectric properties of coconut oil are previously well known but no detailed comparison has been published on the electrical, thermal, and physicochemical properties of coconut oil, commercial natural esters, and mineral oil. This paper aims to present a comparison of the relative advantages, limitations, and scope of coconut oil for use in a transformer.

The main cause of insulation degradation is due to partial discharges (PDs) occurring inside the transformer, and its detection and localization are the most effective, non-destructive methods to assess the insulation condition of the transformer. Among the PD detection methods, the acoustic PD detection technique is popular because of its various advantages. The acoustic PD detection method for accurate PD source localization becomes quite challenging when PD occurs inside the transformer core and windings. As the acoustic sound wave can be distorted and vibration with its distribution, so the type of PD sensors with their setting in the transformer should be thoroughly investigated and chosen. In this work, via simulation, the acoustic sound distribution inside the power transformer due to PD occurs is studied. Based on the knowledge of acoustic pressure wave distribution, a Lead Zirconate Titanate (PZT-5H) sensor is designed using Finite element method based COMSOL Multiphysics software and placed it on the outer walls of the transformer for PD detection and localization. The PD induction position has been recognized from the sensor signal using an artificial neural network. The results of PD detection and localization by the proposed piezoelectric sensor and COMSOL probe point are in good agreement.

This paper presents a new fast Intelligent Programmed Genetic Algorithm (IPGA) based evolutionary optimization algorithm which requires lesser number of objective function evaluation for reaching optima. The proposed algorithm, apart from using probabilistic genetic operator, i.e. crossover and mutation, also uses a deterministic diversity creating operator for generating new solution in the current population. This is done by first projecting objective surface from higher dimension to lower dimension for visualization purpose and then deterministically generates new solution using some predefined rules in the region with higher objective function value. As the newly generated solution is in lower-dimensional space, these solutions are again projected back to higher dimensional space and then the objective function is evaluated at that point. The proposed IPGA is tested on three different categories of standard test functions viz. Unimodal function (2 Test Function), Unrotated Multimodal function (6 Test Function) and Rotated Multimodal function (5 Test Function). Simulation results were compared with that obtained using Binary Coded GA, Real Coded GA, recently proposed GA with Differential Evolution crossover operator (GA–DEx) and another success-history-based adaptive GA with aging mechanism (GA–aDExSPS) in terms of mean and standard deviation of the objective function, average number of objective function evaluation required to reach optima and algorithmic complexity. Simulation results clearly demonstrate better performance of the proposed IPGA when compared with other variants of GAs.

Partial discharge (PD) is the main cause of the insulation decay and hence periodical testing of the insulation condition of a distribution transformer is necessary. This paper presents a model of PD acoustic wave propagation, detection, and localization in an oil-filled distribution transformer using finite element method supported by COMSOL Multiphysics software. Using an acoustic module and AC/DC module of COMSOL Multiphysics software, oil filled distribution transformer, and the acoustic piezoelectric sensor are simulated to analyze and detect the PD inside the transformer. PD is numerically simulated in the transformer windings, core, and oil ducts that produce acoustic wave signal. The distribution of the acoustic pressure wave inside the model transformer is analyzed first. Next, the acoustic piezoelectric sensors are modelled at four different locations of the model transformer to detect the pressure acoustic wave signal induced due to PD in the transformer. Finally, using an artificial neural network (ANN), the localization, and identification of PD in various parts of the transformer have been analyzed. The results obtained for location and detection are quite encouraging.

Voltage stability is a relevant part of power system stability analysis ever since many voltage collapse incidences have occurred at different regions of the world. In this paper we take up IEEE 118 bus system as it represents a close approximation of standard Grid system. This IEEE 118-bus system has fixed number of predefined generators, synchronous condensers, transmission lines, transformers and loads. In this work IEEE 118 bus system is simulated and load flow simulation is computed using the software PSS®E. The weak buses of the IEEE standard 118 bus network are predicted with the help of L-Index Algorithm in MATLAB. Further dynamic simulation is also performed in the weak buses obtained from L-Index as it opens up scope of more detail analysis of the system. An initial transient disturbance is then introduced in the weak buses and then the resultant maximum frequency deviation and the recovery time of the voltage is computed which finally helps to detect the weak areas in the transmission network. Further Critical Clearing time of the weakest bus is also computed.

Energy policymakers address rural energy poverty with locally available renewable sources. Further, an acquaintance in the adoption of similar renewable based rural electrification technology (RBRET) would enhance the community acceptance in the neighboring villages. As a result of which, the pace of RBRET dissemination can be heightened in the corresponding geographic cluster. Amongst the varied RBRET projects, Micro Hydro Power (MHP) is relatively economic, efficient, reliable, and ease to operate. However, the sustainability of MHP cluster relies upon the appropriate prioritization process of site selection. In this regard, a novel computational intelligence technique has been proposed through a case study in the eastern Himalayan region of India. The proposed model encompasses four phases. First, refinement of the initial technical feasibility conformations through geographical information system (GIS) and past hydrological data. Second, the establishment of interdependency influencing relationship using interpretive ranking process (IRP). Third, the computation of Pareto based prioritization of entropy weights derived through IRP. Fourth, the prioritization of potential sites for MHP in the sequential manner adopting fuzzy similarity analysis measure, and Ardalan heuristic method. The proposed hybrid model surpasses the existing application of standalone methods such as multi-criterion analysis tools, geographic information system, and econometric analysis method.

Recently, researchers in the field of Evolutionary Multi-Objective Optimization give a systematic approach for exploring innovative design principles in a conflicting multi-objective optimization problem by analyzing pareto optimal solution using either manual or automated approach. They call it “Innovization” and defined as: “innovation through optimization”. This paper applies manual innovization to multi-objective Optimal Reactive Power Dispatch Problem using Non-Dominated Sorting Genetic Algorithm-II (NSGA-II) as multi-objective optimization algorithm and manually searches for all possible innovative design principles by analyzing multiple pareto optimal solutions. Standard IEEE 30 bus test system is considered for the current work. Simulation results reveal number of innovative design principles. Innovative design principles includes function approximation of relationship between conflicting objectives, characteristics of decision variable with respect to different objectives and actual range of decision variables. Simulation results clearly show much faster convergence when decision variables were obtained using innovative design principles for specified desired objectives as compared to normal case. Results also show some decision variables can be eliminated by setting it to a fixed value, which leads to simplification of optimization problem as the values of these variables remains constant with respect to the values of objective function.

Piwi-interacting RNAs (piRNAs) are an animal-specific class of germline-enriched small non-coding RNAs that shape transcriptome, as well as ensure genomic integrity and fertility by regulating transposons and other selfish genetic elements. In Caenorhabditis elegans mature piRNAs are 21-nucleotides long, begin with a monophosphorylated uridine, and they associate with PRG-1 to form piRISCs that scan the transcriptome for ‘non-self’ sequences. However, these piRNAs are born as longer 5’-capped transcripts, where PARN-1, a 3’-5’ exoribonuclease, contributes to the formation of the mature 3’-end. But, till date, the 5’-processing events remain elusive. We demonstrate that the recently identified endoribonuclease activity of XRN-2 is involved in the processing of the 5’-end of precursor piRNAs in worms. Depletion of XRN-2 results in reduced mature piRNA levels, with concomitant increase in levels of the 5’-capped precursors. We also reveal that the piRNAs born as longer precursor molecules (≥60 nt), prior to 5’-end processing, undergo ENDU-1-mediated endoribonucleolytic processing of their 3’-ends. Our in vitro RNA-protein interaction studies unravel the mechanistic interactions between XRN-2 and PRG-1 towards the formation of mature 5’-ends of piRNAs. In vivo experiments employing prg-1 mutant worms indicate that XRN-2 has the potential to perform clearance of precursors that are not bound and protected by PRG-1. Finally, we also demonstrate that XRN-2 is not only important for the generation of mature piRNAs and piRNA-dependent endo-siRNAs, but through yet unknown pathways, it also affects piRNA-independent endo-siRNAs that shape transcriptome, as well as contribute to genomic integrity via regulation of transposable elements.

MicroRNAs (miRNAs) are critical regulators of diverse developmental and physiological processes, and they themselves get regulated both at the level of biogenesis and turnover. We demonstrate that the ribonuclease XRN2 can degrade the mature forms of certain let-7 family members in multiple human cancer cell lines, without affecting their precursors. XRN2 also affects the accumulation of several other tumor suppressor miRNAs known to play important roles in cancer metabolism. XRN2 depletion results in a reduction in the expression of many oncogenes and diminishes the proliferative and metastatic potential of cancer cells in vitro. These experimental cancer cells also show reduced capacity to form tumors in mice and regress over time. The clinical relevance of these observations is further verified in tumour transcriptomics data from public RNA-sequencing datasets, where XRN2 mRNA expression is inversely correlated with the levels of a large number of miRNAs, including let-7 members, and high XRN2 mRNA levels are associated with poor survival in hepatocellular carcinoma, lung adenocarcinoma, and glioblastoma. We demonstrate that the miRNA is released by an as-yet unidentified proteinaceous ‘miRNA release factor’ from the grasp of Argonaute before its degradation, which is more abundant in the nuclear fraction. Our analyses of the patient-derived transcriptomics data also show that XRN2, via its regulation of let-7, affects multiple pathways in a consistent manner across epithelial and glial cell lineages, and thus, is of critical pathophysiological significance.

Most Electric Power Exchange (PX) around the world employs Linear Programming (LP) based method for step-wise market clearing in Day-Ahead Electricity Market (DAM). Market clearing involves calcul...

This work presents a novel stator flux-oriented vector control (SFOVC) of a dual stator induction generator (DSIG) used for a grid connected, variable speed wind energy generation system. The DSIG consists of two stator windings electrically separated by an angle of 30° with dissimilar pole numbers, which are in the ratio of 1:3. In conventional vector control, the rotor flux is oriented along the d-axis of the rotor winding. However, the rotor variables are not easily accessible. So, in the SFOVC, the total flux is made to be oriented along the d-axis of the stator winding. SFOVC is advantageous as compared to conventional vector control because the stator variables are easily accessible and do not require any special arrangement for the measurement of variables which increases the robustness of the system. Here, two separate converters are used for the two stator windings of the machine and the converter switching is being controlled by a novel space vector based 11-zone hybrid pulse-width modulation (PWM). This special PWM results in better harmonic performance, reduced torque pulsation and minimal switching loss. The overall simulation is being performed in MATLAB Simulink environment and the simulated results are also being validated experimentally.

In this paper a novel speed sensor less vector control of Dual Stator Induction machine has been proposed for grid connected wind energy generation system. Dual Stator Induction machine consists of two stator winding separated by an electrical angle of 30°, with dissimilar pole to overcome the effect of harmonic current occurred in the stator windings. In this work the pole ratio of the two stator winding are taken as 3:1 in order to mitigate the magnetic saturation of the core and high losses which occurs at stator winding. The orientation of the machine is made in such a way that by controlling two stator currents in a perfectly decoupled way zero speed operation can be made possible. There by electrical frequency of it gets maintained at low speed, this characteristic of stator makes the Dual Stator Induction machine more suitable for speed sensor less operation. The two stator windings of the machine are fed from two independent Variable Voltage Variable Frequency inverter, which is being controlled by advanced bus clamping Pulse Width Modulation Technique. The Pulse Width Modulation proposed in this paper is a 9 zone hybrid PWM which results into lower line current ripple, reduced torque pulsation and minimized switch loss then the conventional space vector pulse width modulation, basic and advanced bus clamping PWM and the existing 3, 5 and 7 zone hybrid pulse width modulation. The simulation is being performed in MATLAB and the simulated results are being verified by experimental results. dSPACE DS-1104 Data Acquisition Card is being used to implement the overall control topology.

microRNAs (miRNAs) are known to regulate a vast majority of the eukaryotic genes by post-transcriptional means, and multiple nucleases play critical roles in the biogenesis and turnover of these regulators. A number of studies have indicated that turnover is important for determining the abundance of miRNAs, and thus, in turn govern their functionality. Recent research in Caenorhabditis elegans has revealed an ATP-independent endoribonuclease activity of the ‘miRNase’-XRN-2. Here, we report the characterization of this new enzymatic activity of the fundamentally important XRN-2, and show that it is critical for miRNA turnover and survival of quiescent dauer worms. The dual enzymatic activity of XRN-2 capacitates the mechanism of miRNA turnover to be dynamic, which might confer adaptive advantage to the organism. In continuously growing worms, this new enzymatic activity does not act on miRNAs, but it is important for the generation of mature ribosomal RNAs, which in turn is critical for translation, and thus indispensable for the survival of worms.

Eastern Regional (ER) grid of India is one of the five regional grids consisting of voltage level 765 kV, 400 kV, 220 kV and numerous buses at lower voltage range. ER grid is the backbone of the Indian Grid as it is one of the main power generating hubs. Stability of the Indian Grid depends a lot on ER grid as it is the core of the generation and transmission system. For performing stability studies and to determine the weak area of the grid generally L-Index method is used. For detailed analysis like computation of voltage recovery time, maximum frequency deviation and critical clearing time of the buses of the system L-Index method is not suitable. Hence dynamic simulation is performed as it provides options to compute various parameters of ER Grid. The system has been studied using 197 buses of voltage levels 220 kV and above and transmission lines running over a length of 23,693 km. In this paper the power flow modelling, simulation and analysis of the Eastern Grid of India is performed. L-Index algorithm along with dynamic simulation provides the scope of computation of voltage recovery time, maximum frequency deviation and critical clearing time (by introducing an initial transient disturbance) along with the prediction of weak area of the system which gives a complete picture of transient stability of ER Grid.

Partial discharge (PD) detection in power transformer is a useful condition monitoring process. Various sensors like piezoelectric, optical fiber, capacitive and ultra-high frequency (UHF) sensors have been used for the monitoring of the power transformer. FBG sensor can be installed inside the transformer tank and is able to capture even low acoustic signal of PD due to its high sensitivity, small size and immunity to EMI. Hence in this work, an FBG sensor has been modelled for PD detection in transformer using COMSOL Multiphysics. Authors have studied the sensing performance of the model FBG sensor with different coating radii.

The Unified Power Flow Controller (UPFC) is the adjustable flexible ac transmission system (FACTS) controller that can control the three parameters i.e. Impedance, Voltage and Phase angle of transmission line simultaneously or individually in appropriate combination. This paper presents an investigation on the current research and on the application of fuzzy logic controller in Unified Power Flow Controller (UPFC). A comparative study is also carried out which highlight the different aspects of control strategy of UPFC.

The transformer oil in electrical equipment is mainly used for insulation and cooling purpose of the equipment. This paper presents the experimental results of insulation and cooling performance of transformer oil (mineral oil and MIDEL-7131) based nanofluids. The nanofluids were prepared using SiO 2 nanoparticle with a percentage concentration (W/V ratio) of 0.1, 0.3, 0.5 and 0.7. The results were compared with the base oil and it was found that with the increase in concentration of nanoparticle in the base oil, thermal conductivity of the nanofluid increases by 5% for a percentage concentration of 0.7% in mineral oil and 10% in MIDEL-7131. The impulse dielectric strength of the nanofluid sample also increases up to 25% at a percentage concentration of 0.5% in mineral oil based nanofluid and 18% in MIDEL-7131 oil based nanofluid as compared with their base oils. But unfortunately the AC breakdown voltage of the nanofluids decreased, this decrease in AC breakdown voltage may be due to the increase in moisture content.

This study provides an overview of the different techno-commercial aspects of a wind energy conversion system. The review includes the grid codes provided by the transmission system operator of different countries supplemented by various communication protocols, explanation of different types of conventional and advanced wind generators, discussions on different maximum power point algorithms along with various conventional and advanced pitch angle control systems. The study also describes a variable speed system using different types of power electronic converters at the generator and the grid side to maintain power quality, grid synchronisation and unity power factor operation along with various cooling techniques utilised. In a subsequent part, a clear overview of different control topologies such as field-oriented control, direct torque control, voltage-oriented control and direct power control has been provided along with the recent advancement of each and every topology. The study also provides the challenges of the prevailing technology along with the already available and possible ways of minimising these technological gaps. Finally, a techno-commercial comparison of different commercially available wind systems by different companies has been presented along with their market share based on the current scenario.

Voltage stability is a relevant part of power system stability analysis ever since many voltage collapse incidences have occurred at different regions of the world. In this paper we take up IEEE 118 bus system as it represents a close approximation of standard Grid system. This IEEE 118-bus system has fixed number of predefined generators, synchronous condensers, transmission lines, transformers and loads. In this work IEEE 118 bus system is simulated and load flow simulation is computed using the software PSS®E. The weak buses of the IEEE standard 118 bus network are predicted with the help of L-Index Algorithm in MATLAB. Further dynamic simulation is also performed in the weak buses obtained from L-Index as it opens up scope of more detail analysis of the system. An initial transient disturbance is then introduced in the weak buses and then the resultant maximum frequency deviation and the recovery time of the voltage is computed which finally helps to detect the weak areas in the transmission network. Further Critical Clearing time of the weakest bus is also computed.

The presence of void in a cable causes intensification of the electric field stress due to differences in the dielectric constant between air and surrounding cable insulation. The occurrence of the cavity not only affects the electric field inside the cavity but also distort the surrounding field. Evaluation of maximum void stress is essential in order to determine the severity of partial discharges and the probability of breakdown in cable insulation. The cross-section of XLPE cable has been modeled in COMSOL Multiphysics to simulate the effect of void. It is observed that a void nearer to the conductor results in the highest electric stress whose magnitude decreases with an increase in the thickness. Further, the shape of the void influences the maximum stress- for example, spherical void is having higher maximum electric stress than the one produced by elliptical void.

This paper presents an analysis of acoustic pressure wave distribution in a power transformer due to partial discharge (PD) using the finite-element-method (FEM) based software COMSOL Multiphysics. The acoustic PD is simulated at four different locations of the transformer in the core, in the low voltage (LV) winding, in the high voltage (HV) winding and in the oil duct, respectively. The acoustic pressure wave generated by the PD is investigated in the transient state. Results suggest that the acoustic pressure wave propagation inside the transformer depends on the PD induced location. Moreover, a more significant acoustic pressure gradient is perceived in the region with a higher speed of sound.

Close Proximity Operation of HVAC and HVDC transmission line is the recent trend for increase of power transmission capacity. Need for same is becoming vital day by day due to ever increasing power demand. Erection of HVAC lines has a requirement of high right of way (ROW) as compared to the HVDC lines. Also recent past has witnessed constraint in availability of ROW for many projects of Indian Power Grid. Raise in transmission voltage level of HVDC from Power Grid Corporation of India Limited (PGCIL) and its suitability to decentralized non-conventional grids has led to addition of many upcoming HVDC projects with the already existing ones. So the need of analysis for electric field distribution under this type of hybrid transmission corridor is necessary to meet the standards of engineering design, exposure limits to living beings and environmental protection. The present work shows a two dimensional modelling approach for estimation of hybrid electric field at ground surface with impulse excitation. A practical case of hybrid transmission corridor so formed in Northeast Agra HVDC project of PGCIL has been taken for this case. Effects of both standard and non-standard impulse waveform has been modelled and analysis of its effect on hybrid electric field is presented.

This paper presents measurement results of thermal conductivity, AC breakdown voltage, and viscosity of two types of nanofluids, viz. mineral oil based and synthetic ester based, prepared using silica nanoparticles of size less than 50 nm. The enhancement achieved in thermal conductivity was about 14% at 0.05% (w/v) of silica nanoparticles in synthetic ester while those in mineral oil based nanofluid it was 11%. The results agree well with theoretical estimate by Hamilton and Crosser Model. Although there is no change in AC breakdown voltage at initial concentration of nanoparticles up to 0.02 %( w/v), the value thereafter decreases marginally in both types of nanofluid. This may be mainly due to increase in viscosity at higher nanoparticle concentration level. Overall, it has been found that there has been a maximum and positive influence on the thermal conductivity of the dielectric fluids due to nanoparticle dispersion.