Nowadays, the Distribution System Operators face challenges with the selection of the most cost-effective network expansion measures that have to be undertaken due to the growing integration of Distributed Energy Resources (DERs). In this paper, the main goal is to develop a comprehensive framework for conducting a cost analysis of grid expansion plans that consider both conventional and innovative smart grid solutions. The planning framework consists of three main stages. At the pre-processing stage, the future scenario is defined, identifying grid contingencies and specifying the available grid upgrade equipment. Next, the core of the framework, is a bi-level optimization process that optimizes both capital and operational costs of the candidate solutions. At the final post-processing stage, the most cost-effective solutions for the predefined scenario are generated. The framework is applied for an IEEE low voltage test grid simulating three different DER future scenarios. From the results, it is evident that the framework can defer the replacement of existing assets and installation of smart grid technologies by leveraging flexibilities of load shifting methods.

Present work deals with accelerated electrical and thermal stress on transformer oil and its characteristic variation on Fuller's earth (FE) reclamation. The influence of carbon particles in the fluid, its role on thermal ageing characteristics can be understood by electrical characterization. Reclamation of insulation fluid extends the lifetime and reliability of the transformer over the year of operation. The average particle size of carbon particles on electrical breakdown are in the range of 644 nm. Dielectric response spectroscopy (DRS) which identifies the conductivity and relative permittivity variation with the effect multi-stress ageing. Conduction mechanism with higher electric field is simulated by current-voltage (IV) characteristics using non-uniform field configuration to derive the ionic mobility of the liquid. Dissolved decayed products and turbidity showed drastic enhancement with multi-stress ageing than the thermally aged specimen. Reclamation with fuller earth treatment removes the carbon traces and ageing by-products in the fluid regaining its relative dielectric performances. Rheological aspects with viscosity indicates the ageing by-products build and also its characteristic variation on the reclamation process.

In recent years, the installation of renewable energy generation systems based on photovoltaic (PV) panels has experienced massive increments and PV parks with thousands of panels are now becoming commonplace. Yet, there are some challenges, like inspection and fault detection. Lately, these operations have been approached using drones. This project adds the use of deep learning, more specifically proposes the convolutional neural network (CNN) algorithm, the YOLOv5 model and Real-Time Messaging Protocol (RTMP) protocol to achieve real-time detection of PV panels failures. The YOLOv5 model was trained by sets sorted into 9 different categories including fault and abnormal objects' coverage. This multi-class classification system was investigated by a variety of evaluation indexes to show effectiveness and accuracy. The system was also examined with its different fault classes. The performance results demonstrate that the mean average precision could reach up to 98% with a good training set, confirming the feasibility of proposed approaches.

This work deals with the effect of oil reclamation on the conduction mechanism and dielectric aspects of accelerated thermally aged transformer mineral oil. The reclamation is a treatment with Fuller's earth (FE) adsorbent to remove corrosive sulfur compounds and other contaminants formed during thermal aging. The properties of the oil are compared between different stages of the treatment. Corona (partial discharge) inception is identified by the optical fluorescent fiber technique. The results show an increased corona inception voltage after treatment. Dielectric response spectroscopy (DRS) showed a lower loss factor and electrical conductivity after treatment. The conduction mechanism is measured under uniform and nonuniform electric fields with variations in applied voltage magnitude. The conduction mechanism at a uniform electric field (low E) is studied using the polarity reversal technique to estimate the respective ionic motilities in the fluid. The apparent mobility of ions, conductivity, ionic radius, and concentration from the oil are found to reduce on reclamation. In addition, the conduction mechanism for a higher electric field is simulated by the current-voltage characteristic in nonuniform conditions and the slope determines the ionic mobility of the fluid.

Insulation in rotating machines is a common cause for failure. Therefore, it is important to further increase the knowledge of the phenomena related to insulation degradation. Today, there are many different methods of detecting Partial Discharge (PD) in stator bar insulation and this study aims to perform a selected variety of commonly used methods for comparison and to further enhance the current knowledge on the matter. 20 stator bars from a hydro generator, that was being taken out of operation due to insulation problems, were obtained for this study. The following measurements were performed on the bars: electrical phase resolved partial discharge analysis, acoustic partial discharge measurements, and breakdown testing. An attempt was made to locate the partial discharge source within the stator bars as well as to identify the different types of partial discharges observed from the measurements. It was found that the stator bars had a significant amount of partial discharge within them and that most of the worst cases could likely be due to the stress grading of the bars. The comparison of electrical partial discharge analysis and acoustic partial discharge analysis showed that in this case the two methods complimented each other, where the electrical method provided more detailed results for deeper analysis. Furthermore, the attempt to perform breakdown tests showed that despite the large amount of partial discharges in the bars, most of the bars were in no danger of breaking down due to electrical stress had they been kept in operation.

The electric power system is continuously growing in size and complexity. Improving the reliability is a necessity and it is possible by means of continuous condition monitoring of power apparatus. Partial Discharge (PD) monitoring is one such technique that is commonly used to detect defects in power apparatus. In general, IEC 60270 based PD measurements are carried out, but in recent times antenna-based UHF measurements are gaining importance due to their advantages like continuous monitoring and non-contact detection methodology. In the current study, the antenna-based PD measurements were studied on defect models of corona discharge, surface discharge and void discharge. The PD testing was also carried out on bushings with defects. An attempt to study a new RF signal conditioning technique was also made using the Schottky diode-based power detector. Using this technique high frequency UHF signals can be shifted to lower frequencies which help reduce the bandwidth requirements for the monitoring systems thereby reducing the cost of hardware when online monitoring is carried out on a large scale.

In recent times, nanoparticles-dispersed ester fluids are reported to exhibit improved thermal and electrical properties for its application in insulation system. In the present study, insulating nanoparticles of silica were dispersed in synthetic ester fluid to improve electrical characteristics of the base fluid. A two-step process involving mechanical shear mixing and ultrasonication was adopted for producing nanofluids. Physical and chemical characterization of nanofluids were carried out to estimate stability of the nanofluid with optimum concentration of nanoparticles and surfactants. To substantiate the influence of nanoparticles and surfactant on the dielectric properties of the nanofluid, conductivity measurements were made at low and high electric field conditions. It was observed that in the presence of electric field, the motion of ions is inhibited due to its trapping by the surface of nanoparticle, leading to lower ionic mobility. To explore the governing mechanisms further, electrical insulating performance of the nanofluid and corona discharge activity were investigated under AC and DC voltages using ultrahigh frequency (UHF) technique. This study has also shown an increase of 30% improvement in the corona inception voltage (CIV) upon addition of nanoparticles. The discharge activity was also mitigated due to incorporation of nanofillers in the fluid. The energy of discharge was found to be lower in nanofluid as compared to base fluid. It was evident from the present studies that silica-based nanofluids have shown superior dielectric performance compared to the base synthetic ester fluid.  

This work reports an experimental and theoretical analysis of the rheological properties of mineral oil-based SiO₂ nanofluid for their potential applications in transformer insulation. The flow electrification mechanism on the nanofluids with different surfactants such as cetyl trimethyl ammonium bromide (CTAB), oleic acid, and Span 80 is studied using a spinning disk technique. The results show a higher streaming current for the nanofluids with CTAB as a surfactant compared to oleic acid and Span 80. The rheological behavior of nanofluids is explored with the double gap concentric cylinder geometry. The variation of shear stress with shear rate follows a power law relationship along with a yield stress observed for all the nanofluids. A transition is seen from storage modulus to dominant loss modulus for the nanofluids during the frequency sweep analysis, whereas no transition is observed in the case of mineral oil. In addition, regression analysis using artificial neural network (ANN) algorithms are performed on the experimentally measured viscosity of the nanofluids in order to estimate theoretical parameters and provide insights into the streaming current formation. The desirable rheological characteristics of nanofluids are identified for achieving enhanced insulation performance in transformers.

This article reports an experimental investigation of the impact of magnetic field on corona discharge activity in mineral oil, using both ultrahigh-frequency (UHF) and fluorescence techniques under ac voltage. The results show that corona inception voltage (CIV) increased under ac voltage with varying harmonic frequencies without considering any phase shift and reduced marginally under magnetic field. In addition, the impact of the magnetic field shifted the dominating frequency of the UHF signal (0.9 GHz) obtained under ac voltage toward lower frequencies (0.3 and 0.6 GHz). Under high magnetic fields, the parameters such as rise time, fall time, and pulsewidth of the fluorescence signal increased in its magnitude compared to its effect without a magnetic field. Also, using both the UHF sensor and the fluorescence sensor, there was no clear difference in the phase-resolved partial discharge (PRPD) pattern caused by corona discharge (with and without magnetic field). Furthermore, the number of discharges is observed to be high under the impact of harmonic ac voltages with third- and seventh-order containing total harmonic distortions (THDs) of 4% and 40%.

This study reports experimental investigations of the effects of different surfactants (CTAB, Oleic acid and Span 80) on silica based synthetic ester nanofluids. The positive and negative potential observed for the ionic (CTAB) and non-ionic surfactant (Span 80) from zeta potential analysis indicates an improved stability. The optimization of nanofillers and surfactants is performed considering the corona inception voltage measured using ultra high frequency (UHF) technique and fluorescent fiber. Rheological analysis shows no significant variation of properties with shear rate, implying Newtonian behavior even with the addition of surfactant. In addition, the permittivity of the nanofluid is not much affected by adding surfactant but a marginal variation is noticed in the loss tangent with the effect of temperature. The fluorescence spectroscopy shows no change in the emission wavelength with the addition of silica nanofiller and surfactants. Flow electrification studies indicate an increase in the streaming current with the rotation speed and temperature, with a higher current magnitude observed in the case of nanofluids.