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Hydrophobic cycloaliphatic epoxy resin (HCEP) insulators are a new generation of outdoor transmission line insulators with good application prospects. However, the HCEP has obvious curing internal stress due to the uneven internal temperature distribution. In this paper, the curing reaction of HCEP mixture is analyzed and a three-dimensional transient temperature field model of HCEP insulator is established. The internal temperature field of HCEP insulator during curing is analyzed for the first time. The results show that the curing reaction of HCEP mixture conforms to autocatalytic reaction. The structure of umbrella skirt causes the uneven temperature distribution inside HCEP insulator. Based on a surrogate model, it is found that thermal conductivity has a great influence on axial temperature distribution, while curing temperature plays a leading role in curing degree and temperature overshoot. The optimal curing temperature is found according to Pareto front. This paper is beneficial for the theoretical analysis and engineering guidance for manufacture of HCEP insulators. [ABSTRACT FROM AUTHOR]

This paper proposes a design optimization method for the insulation structure of a High Voltage Direct Current (HVDC) converter transformer, which is exposed to AC, DC, and DC polarity reversal (DCPR) stresses. Since DC and DCPR stresses provide significantly different electric field distributions, conventional transformer insulations designed for AC systems cannot guarantee safety against electrical breakdown. Focusing on main-winding and end-winding insulation including pressboard barriers and oil between windings, this paper presents a design solution based on genetic algorithm (GA). By exploiting modern computing power, the proposed approach can save a considerable amount of effort and time compared to conventional approaches which depend on experimental data and human experience. From the comparison with example reference insulation structures, we verified that the optimized structures maintain the required insulation performance with the reduction of length by 2.8% for the main-winding insulation and by 13.8% for the end-winding insulation. [ABSTRACT FROM AUTHOR]

In previous studies moisture diffusion coefficients for transformer pressboard insulation impregnated with mineral oil have been proposed. In this paper diffusion coefficients are proposed for transformer pressboard insulation impregnated with different natural esters. The coefficients were validated with experimental data and compared with those of mineral oil. In the determination of the moisture coefficients drying experiments at different temperatures were performed on pressboard samples of several thicknesses. An optimization process based on particle swarm and a finite element model were used to derive the coefficients from experimental data. [ABSTRACT FROM AUTHOR]

The ?1100 kV UHVDC wall bushing is the important power equipment in the ?1100 kV DC power transmission project of China. However, the reported literatures rarely mention its design method and the optimization of its insulation structure. In this paper, two specific designing schemes including the resin impregnated paper (RIP) condenser and the metalshielded core have been both adopted in the design of the wall bushing. Moreover, the actual operating environment and the rated parameters of the ?1100 kV UHVDC wall bushing have been analyzed in detail. Then, the nonlinear finite element method (FEM) analysis has been applied in the three-dimensional electric stress simulation of the UHVDC wall bushing. The electric field and temperature dependencies of the composite insulation used in the wall bushing have been taken into account. The E-field simulation results indicate that with the RIP condenser, the potential and electric field distribution can be much more uniform along the composite insulator of the bushing. Therefore, the compact design of the wall bushing can be obtained by this designing scheme. On the other hand, with the type of the metal-shielded core, the high E-field strength areas are mainly concentrated on the metal shield and the outer grading ring of the wall bushing. Therefore, the nonlinear FEM was applied in the structure optimization of the internal metal-shielded system used in the wall bushing. Finally, the maximum E-field strength of the wall bushing can meet the control requirement. Based on the simulation results and the optimization structure, the ?660 kV scaled prototype of the UHVDC wall bushing has been produced and passed through all the type tests according to the IEC 62199. The feasibility of the design of the ?1100 kV UHVDC wall bushing has been verified. This paper can provide the theoretical guidelines for the design, manufacture and operation of the UHVDC wall bushing. [ABSTRACT FROM AUTHOR]

The indoor DC yard of the ±1100 kV UHVDC transmission project is preferred to the outdoor solution, and the rational design of shielding electrodes for the ±1100 kV apparatus becomes the key to system security. In this paper, the design requirements of indoor DC yards were described and the preliminary designs of the indoor shielding electrodes for the key ±1100 kV DC apparatus were proposed. The whole 3-D FEM model of one ±1100 kV indoor DC yard was established. An empirical formula of the critical E-field strength for the evaluation of relatively large shielding electrodes was proposed based on the corona tests of typical ball and ring electrodes. The electric field distribution of the whole indoor DC yard was calculated and the surface electric field strength of all the shielding electrodes for the key ±1100 kV apparatus was evaluated. The results show that after optimization, the maximum surface field strength on the shielding electrode of ±1100 kV DC filter capacitor decreased from 1507 V/mm to 1335 V/mm, lower than the critical value for evaluation, then the corona free design of all the ±1100 kV indoor shielding electrode could be predicted. The method of electric field evaluation and optimization could provide important references for the development of shielding electrodes in the ±1100 kV or other UHV indoor DC yards. [ABSTRACT FROM AUTHOR]

This paper describes the designing of a new external shape for a medium voltage indoor post insulator, which consists of an optimization polynomial. The new external shape provides lower values of electric field strength inside the insulator and in the air. Another innovation is the use of reliable components, i.e. the voltage divider. The new insulator uses a ceramic capacitor with the required capacitance, unlike previous insulators that had problems reaching the appropriate capacitance using cylindrical metal mesh. The insulator model was built with MATLAB software, followed by the calculations of electric fields in EleFAnT software. The differential evolution (DE) algorithm was used as a successful and global optimization algorithm for the optimal design of an insulator's external shape and the position of internal insulator elements. [ABSTRACT FROM PUBLISHER]

In this paper, a study of the effect of a group of transformer measurements on Health Index (HI) calculation is presented. Different methodologies for selecting the most efficient group of diagnostic measurements used in classifying transformer HI are investigated. A Binary Cat Swarm Optimization (BCSO) technique is undertaken based on Support Vector Machines (SVM). The technique depends on selecting the optimal parameters for SVM. The effect of selecting HI classes as well as class's boundaries is also studied. The measurements of fourteen diagnostic transformer tests, including the furan analysis, dissolved gas analysis, and further oil analysis for 724 distribution transformers are studied, and the corresponding HI is calculated according to industrial standards. The model renders the best-selected group of measurements that assist in the formulation of the health index with minimum error and high confidence. [ABSTRACT FROM AUTHOR]

This paper presents a generic hybrid optimization methodology based on space mapping techniques for the design of various high voltage pulse transformer structures used in klystron modulators. It is using two dimensioning models with different levels of complexity: a coarse model based on 2D FEA less accurate but cheaper to evaluate and a fine 3D FEA model more accurate but time consuming. A specific correction mechanism is applied to align the 2D FEA dimensioning model with the more accurate 3D FEA dimensioning model. With a suitable selection of the correction factors, the convergence of this hybrid optimal design methodology is obtained with a limited number of time consuming 3D FEA simulations. The method is applied to the optimal design of a monolithic high voltage pulse transformer for the CLIC klystron modulator. The influence of the klystron operating voltage on the size of the optimal pulse transformer is evaluated with the proposed design methodology. [ABSTRACT FROM AUTHOR]

This paper analyzes the influences of the factors in a capacitor-driven multi-stage synchronous induction coilgun (SICG) and optimal combination of the design parameters based on orthogonal experiment design (OED). Finite element transient solver is used to calculate the motion characteristics of a multi-stage SICG. The muzzle speed is set to be the target of the optimization. System parameters (factors), levels and orthogonal array (OA) are determined by the order. Three optimization schemes are compared, including stage-by-stage optimization, section optimization and full optimization. Optimal combination of the three-stage SICG is obtained, as well as important order of factors. It shows that a set of comparatively better parameters and relatively higher efficiency could be achieved through orthogonal optimum. Wire diameter and coil diameter are the most important factors that influence the system efficiency of the launcher. Besides them, length of coil, trigger position and number of turns have less influence for the system in the important order. Section optimization could reduce the amount of computations compared to full optimization and a set of comparatively better parameters and relatively higher efficiency could be achieved. It is suggested to optimize a multi-stage SICG. How to choose the factors from lots of parameters is according to the engineering practice. Improper choices of the value in levels may cause unable to reach an optimum. The conclusion will be useful for coilgun design. [ABSTRACT FROM PUBLISHER]

Current issues on localization algorithms based on the time difference of arrival (TDOA) for the partial discharge (PD) source include its sensitivity to time delay error, easy local convergence or divergence, and the large amount of computational load and time. A semi-definite relaxation method for PD source location to solve the time delay positioning equations is proposed in this paper, which using the semi-definite programming problem has the characteristic that can ensure obtained the global optimal solution. The proposed method converts nonlinear time delay equations into an equivalent semi-definite programming (SDP) problem by equivalent transformation and rank-1 relaxation firstly. Then use the interior point algorithm to solve the SDP problem that to obtain a unique global optimum solution, and extract a rank-1 component from the global optimal solution of relaxed SDP. Finally, to serve as a good approximate of the original problem for the PD location. The method was used to localize a measured PD source signal in the laboratory, and the results were compared with those of positioning by the Newton-iterative method. The comparison showed that the method can reduce sensitivity for the time delay error as well as effectively solve TDOA location equations, thereby ensuring that the result is a unique global optimal solution with high positioning efficiency. The localization algorithm problem is solved with the unavoidable and difficult-to-locate time delay error. [ABSTRACT FROM AUTHOR]

Partial discharge (PD) detection and location is of great significance for the power cable insulation condition monitoring, where the high-frequency (HF) model is needed to analyze PD propagation. Considering the influences of conductor skin effects and semi-conducting layers (SCL), this paper presents the equivalent ?-section lumped parameter model for single-core cross-linked polyethylene (XLPE) insulation cables. The longitudinal parameters per-unit-length in the model are obtained using available geometric data by vector fitting method. Unfortunately, the dielectric characteristics of SCL in XLPE cables, especially for an installed one, are usually unknown and hard to measure. To address this issue, based on the simulated annealing algorithm, an optimization approach for estimating the transversal parameters in the ?-circuit model is developed. The proposed technique is then carried out on the XLPE cable with simulated and real SCL, respectively. Furthermore, the estimation results of the real case are validated on a 603 m cable with kinds of HF pulses responses. [ABSTRACT FROM PUBLISHER]

As composite cross-arm will be used in domestic 750 kV AC transmission line for the first time, careful and meticulous preparatory work is highly needed. Using a threedimension (3-D) finite-element method (FEM) software, this paper presents computation results of the potential and electric field distribution for composite crossarms in the process of structure optimization. Several optimization programs for composite cross-arm have been studied and the final design is made to omit the suspension insulator string, to increase the length of post insulators and to configure suitable grading and shielding rings based on preliminary design. A set of grading and shielding rings configuration program has been proposed. The comparison between optimized composite cross-arms and 750 kV line composite insulators indicates that composite cross-arms have better potential distribution. The electric tests demonstrate that optimized composite cross-arms have good electrical performance and can meet operation requirements. [ABSTRACT FROM AUTHOR]

Streamer discharges are an important breakdown mechanism in air-based electrical insulation systems. This paper introduces a method to estimate the spatial distribution of the charge density of positive streamers in air, based on the solution of a Poisson inverse problem by optimization. In contrast to other methods, it does not require tuning parameters and can also be used in configurations including dielectric interfaces or preexisting space charge. Three different experimental datasets reported in the literature are used to validate the method. Good agreement between the measurements and the predictions of the method is found. [ABSTRACT FROM AUTHOR]

Geometric properties of insulation layers in stator slot of HV generator such as semiconductive coatings, groundwall insulation, phase-phase insulation as well as turn and the strand insulation are major design consideration for insulation system of HV generators. In addition, electrical conductivity, thermal conductivity, heat capacity and electrical permittivity of these insulation layers have an important role on decreasing electrical field tensions. Obtaining of optimum value for these parameters leads to achieve less electrical field tensions and more uniform electrical field distribution across them. A very powerful method presented to optimization is SNOPT (generalpurpose system for large-scale nonlinearly constrained optimization) which is coupled with Finite Element Method (FEM). These processes of optimization have been done according the proposed optimization algorithm. In this algorithm the technical constraints have been considered. This paper describes the process used to perform improvement analysis of stator slot's insulation for 24, 36 and 72 slots generators with respect to objective function and constraints. [ABSTRACT FROM AUTHOR]

An application of a functionally graded material (FGM) to the solid spacer in gas insulated switchgears (GISs) can reduce the electric field concentration at the specific region, for example, the anode or the interface between the spacer and the gas. However, the electric field stress near the triple junction of the grounded electrode with a rounded shape, which remarkably affects the insulation capability of the GIS, inversely related. Therefore, in order to prevent this, it is necessary to modify the grounded electrode geometry in the common Cubicle-GIS and apply the elliptical FGM spacer with a reverse-direction variation unlike the permittivity variations of the existing unidirectional or bidirectional distributions. In this paper, we found the proper distribution of dielectric permittivity, dug a groove in the grounded electrode near the triple junction, and performed the optimization of this grounded electrode configuration by using the design of experiments (DOE). Consequently, the electric field stress in the triple junction of the grounded electrode can be effectively reduced by using the optimally designed grounded electrode shape applying the FGM spacer. [ABSTRACT FROM AUTHOR]

In this paper the electrode geometry effects on the impedance spectroScopy of biological cell culture have been studied under low intensity sinusoidal electric field with a view to design improved electrode structures for continuous cell growth monitoring. To achieve this, impedance estimation has been done by modified distributed analysis both in presence and absence of confluent cell layer by taking into account the effect of solution resistance and the separation between the electrodes. The model has been applied on fibroblast cell culture (3T3) in the frequency range of 10 Hz to 10 kHz. It has been observed that for most of the frequencies, the resistance sensitivity (Sr) is less than the capacitance sensitivity (Sc) and does not increase monotonically with radius of working electrode (Re) unlike Sc. Further, the nature of variation of Sr and Sc are fairly contradictory with variation in Re and separation between the electrodes (d-Re). Thus an optimum geometry has been selected based on a figure of merit (FOM) which has been defined as the product of Sr and Sc. The maximum FOM corresponds to Re=90 ?m and d=3Re for a typical frequency of 4 kHz. Observations at 4 kHz show that the optimized geometry yields values of Sr that are almost 5 times higher than those from the conventional geometry (Re=125 μm and d=300Re). This increase permits the small signals resulting from the micromotion of cells to be more easily seen. [ABSTRACT FROM PUBLISHER]

In this paper support vector machine (SVM) has been used for optimization of electric field along the support insulators used in high voltage (HV) systems. To illustrate the effectiveness of SVM in optimizing electric field problems, two axi-symmetric cases have been considered one having an insulator with a contour that is quarter ellipse and the second one having a porcelain core solid insulator. The training and the test data for the SVM have been prepared by electrostatic field computation using indirect boundary element method (BEM). It is observed that once the SVM is trained it is able to give results with mean absolute error of less than 1.5 % when compared with the analytically obtained results. The SVM designed for insulator contour optimization is first trained with the results obtained from electric field computation for some predetermined contours of the arrangements under consideration. Then the trained SVM is used to produce an optimized insulator contour in such a way that the desired stress distribution can be obtained on the insulator surface. The results obtained from the present study show that the trained SVM is adequately efficient to optimize insulator contours in order to have the desired stress distribution along the insulator surface. [ABSTRACT FROM AUTHOR]

Electrostatic air propulsion is a promising technology with such potential applications as energy-efficient ventilation, air sterilization, cooling of electronics, and dehumidification. The challenges of existing designs include the need to increase air speed, backpressure, energy efficiency, and heat exchange capability. The ultimate goal of this direction of research is to create multi-channel energy efficient ionic pumps. In the described project, a single cell analysis is conducted in this study as a building block of future designs. This paper presents the numerical simulation and experimental results of electrostatic fluid accelerators. This study was conducted for the purpose of optimizing device characteristics through the control of the electric field distribution. Simulations were performed for multiple collector electrode voltage distributions. A method to quantify the change in pump performance between different voltage distributions is presented. The influence of space charge on pump performance is also discussed. A significant improvement of air velocity generated by optimized electrostatic fluid accelerators has been achieved using the proposed approach. [ABSTRACT FROM AUTHOR]

Working characteristics of a three-electrode trigatron spark gap is discussed in this paper. Breakdown probability is proven to fit a Weibull distribution. For an engineering application, the lower limit of undervoltage ratio depends on breakdown probability, and the upper limit of undervoltage ratio depends on self-breakdown probability. Some characteristics have been determined experimentally, such as the influence of the air pressure and the influence of the undervoltage ratio on spark gap operation. Curve fitting and quasi-data mining are good methods for research on triggering characteristic in the paper. Therefore, a maximum operation range curve and a boundary line of expected delay time could be determined by application requirements, theory calculation, experimental data and curve fitting. On this basis, optimization operation range could be obtained, which represents a preferable performance of breakdown with expected delay time. It may provide guidance for engineering application. [ABSTRACT FROM AUTHOR]

Research and development results of enhancement techniques of electrical insulation performance for higher electric field application in power transmission/substation equipment, such as transformers, switchgears and cables, are described, especially based on the view point of dielectric materials. Firstly, the electric field analysis, field optimization and field measurement techniques are introduced to discuss higher electric field stress applications in power equipment. Secondly, material types, including gases, liquids, solids, vacuum and their composite systems are discussed to make power equipment with higher insulation performance, lower losses, lower environmental impact and higher reliability. In the process of development, a highly sophisticated new approach to clarify the physical mechanisms of partial discharges was developed and applied. By the introduction and applications of the above mentioned new electrical insulation techniques based on dielectric materials, concepts of future power equipment with higher electric field stress are proposed. This paper is based on the Whitehead Memorial Lecture given at the IEEE Conference on Electrical Insulation and Dielectric Phenomena (CEIDP) 2011 in Cancun, Mexico. [ABSTRACT FROM PUBLISHER]

In this paper athree-stage pulse generator architecture capable of generating high voltage, high current pulses is reported and system issues are presented. Design choices and system dynamics are explained both qualitatively and quantitatively with discussion sections followed by the presentation of closed-form expressions and numerical analysis that provide insight into the system?s operation. Analysis targeted at optimizing performance focuses on diode opening switch pumping, energy efficiency, and compensation of parasitic reactances. A compact system based on these design guidelines has been built to output 8 kV, 5 ns pulses into 50 ?. Output risetimes below 1 ns have been achieved using two different compression techniques. At only 1.5 kg, this light and compact system shows promise for a variety of pulsed power applications requiring the long lifetime, low jitter performance of a solid state pulse generator that can produce fast, high voltage pulses at high repetition rates. [ABSTRACT FROM AUTHOR]

This paper presents corona ring optimization for 380 kV V-insulator string composed of glass insulator units. The influence of the corona ring design parameters are examined not only with regard to 3D simulations but also laboratory tests. The purpose of the simulations is to find reasonable corona ring design parameters such as corona ring diameter, corona tube diameter and installation height on the point of effective field regulation around the critical region of the string. Indoor laboratory tests including radio interference voltage levels, corona inception voltages and ac flashover voltages are conducted on the centre phase of a full scaled tower both for experimental based corona ring design as well as verifications of the simulations. After both simulations and experimental based investigations, appropriate corona ring design parameters for the string are determined for effective field regulation, minimum interference level, ac flashover performance and economic point of view. [ABSTRACT FROM AUTHOR]