The impact of electrode dielectric coating on the insulationintegrity of GIS/GITL with metallic particle contaminants

Coating the inside surface of gas insulated switchgear (GIS) enclosures with a dielectric film reduces the deleterious effect of electrode surface roughness, impedes the development of metallic particle initiated microdischarges, increases the field required to lift particles, and reduces the charge acquired by particles, all of which help alleviate the adverse effect of contaminating metallic particles on insulation withstand. The performance of particle-contaminated compressed gas systems with dielectric coated electrodes is analyzed. Two mechanisms for the transfer of charge from electrodes to contaminating particles are considered, namely, conduction through the coating layer and microdischarges in the surrounding gas. The paper presents an electrostatic study of the particle lifting fields with dielectric covered electrodes. The overall breakdown strength of the system is evaluated and the results are discussed in the light of experimental findings     

Numerical computation of conducting particle trajectories in plate-type electrostatic separators

Development of new applications of plate-type electrostatic separators need increased controllability of particle trajectories. The aim of this paper is to model the particle behavior after lift-off from the plate electrode. A superficial charge simulation program was employed for the computation of the electric field in the active zone of the separator. This enabled the evaluation of the charge acquired by a conducting particle in contact with the plate electrode and the electric force exerted on it before and after detachment. Based on a previously derived mathematical model, the particle trajectories were calculated for various electrode configurations. The data of such numerical simulations can guide the experimental studies needed for the assessment of new industry applications of electrostatic sorting or classifying techniques.     

Laplacian fields of bell-type electrostatic painting systems

A Laplacian model (i.e excluding the space charge effect) for a bell-type electrostatic painting system has been developed using the charge-simulation technique. The study involved the evaluation of the electric field in the space between the bell and the paint target as well as at their surfaces. An investigation was also conducted to determine the variations that occur to the electrical parameters when: (1) the bell-to-target spacing is changed; and (2) the size of the target is varied. Finally, results are reported for incorporating the charge-simulation model in a routine that predicts the paint-droplet trajectories from the bell to the target. The results of the developed model predict that the field-dependent droplet charging mechanisms, which are required to ensure strong electrical forces on the droplets, will be insensitive to the size of the workpiece and the spacing between the bell and the target. However, the magnitude of the fields at the workpiece, which account for the enhanced deposition in electrostatic painting, are shown to be highly dependent on these parameters     

Multiscale compression of BEM equations for electrostatic systems

This paper describes the use of wavelet bases to create a sparse approximation of the fully populated matrix that one obtains using an integral formulation like charge simulation or surface charge simulation for numerically solving Laplace's equation with mixed boundary conditions. The sparse approximation is formed by a similarity transform of the N×N coefficient matrix, and the cost of the one employed here is of optimal order N². We must emphasize that benefits of computing with a sparse matrix typically do not justify the costs of the transformation, unless the problem has multiple right hand sides, i.e. one wants to simulate multiple excitation modes. The special orthogonal matrices we need for the similarity transform are built from wavelet bases. Wavelets are a well studied and mature topic in pure and applied mathematics, however, the fundamental ideas are probably new to many researchers interested in electrostatic field computation. Towards this end an important purpose of this paper is to describe some of the basic concepts of multiresolutional analysis using wavelet bases     

Measurement of particle size and electrostatic charge distributionson toners using E-SPART analyzer

Performance characteristics of a laser-based instrument called the electrical-single particle aerodynamic relaxation time (E-SPART) analyzer for measuring aerodynamic size and electrostatic charge distribution of particles in real time and on a single-particle basis are described. Applications of this analyzer along with experimental data of the characterization of different toners for their size and charge distributions are presented, including operational principles and methods of data acquisition. Size distribution ranged from 2.0 to 20.0 μm in aerodynamic diameter, and the charge-to-mass distribution ranged from 0 to ±20 μC/g. The method is noncontact and provides both magnitude and polarity of electrostatic charge on an individual particle basis. The aerodynamic diameter and charge are measured simultaneously at an average count rate of approximately 100 particles/s     

The effects of plasma on electrostatic powder coating systems

In electrostatic powder coating, using a frictional charger, a serious problem is the poor charging characteristics of powder paint. In order to overcome this problem, the authors have investigated a new system composed of a plasma generator and a frictional charger. The results obtained for two kinds of polyester powder paints showed that the plasma has a strong effect on the characteristics of frictional charging in powder paint; the frictional charge was more than five times as large as that without plasma effects     

Electric field effect on metallic particle contamination in a common enclosure gas insulated busduct

Sulphur hexaflouride (SF₆) is generally found to be very sensitive to field perturbations such as those caused by conductor surface imperfections and by conducting particle contaminants. A study of CIGRE group suggests that 20% of failures in gas insulated substations (GIS) is due to the existence of various metallic contaminations in the form of loose particles. The presence of contamination can therefore be a problem with gas-insulated substations operating at high fields. If the effects of these particles could be eliminated, then this would improve the reliability of compressed gas insulated substation. It would also offer the possibility of operating at higher fields to affect a potential reduction in the GIS size with subsequent savings in the cost of manufacture and installation. The purpose of this paper is to develop techniques, which will formulate the basic equations that will govern the movement of metallic particles like aluminum and copper in a bus duct. The simulation considers the electric field effect on particle movement and the results have been presented and analyzed     

Assessing the risk of failure due to particle contamination of GISusing the UHF technique

The ultra high frequency (UHF) technique has been used to study the partial discharges produced by free conducting particles in gas insulated substations (GIS) with a view to predicting the probability of particle-triggered breakdown. Statistical techniques have been developed to describe the motion of a single particle. It is possible to identify whether the particle is capable of crossing to the busbar, which is a necessary condition for particle-triggered breakdown. In addition, the technique can be used to assess the size of the particle, which is useful for making a qualitative assessment of the breakdown risk. The implications for the continuous discharge monitoring of GIS are discussed     

Power systems operation using particle swarm optimization technique

This paper presents a proposed technique for solving different optimization problems using particle swarm optimization (PSO) technique as a modern optimization technique. The security constrained optimal active power dispatch is solved by a proposed optimal effective localized area (OELA) in large-scale power system at different operating conditions. However, the boundaries of this area can be increased or decreased depending on the amount and type of the operation problems as well as the control action requirements to remove these problems. Hence, minimum control variables are adjusted in a small-localized area to steer the system to secure and reliable operation condition. The optimal operation of ready reserve is introduced using an efficient proposed procedure considering the security constraints of the transmission lines power flows. Different emergency condition problems are solved using the OELA applied to different standard test systems.     

粒子群优化算法在电力系统中的应用综述

粒子群优化(PSO)算法是一种新兴的群体智能优化技术,其思想来源于人工生命和演化计算理论,PSO通过粒子追随自己找到的最优解和整个群的最优解来完成优化.该算法简单易实现,可调参数少,已得到广泛研究和应用.在大量参阅国内外相关文献的基础上,简要介绍了PSO算法的工作原理,较为全面地详述了粒子群优化方法在电力系统中的应用,如电网规划、检修计划、短期发电计划、机组组合、负荷频率控制、最优潮流、无功优化、谐波分析与电容器配置、参数辨识、状态估计、优化设计等方面,并对今后可能的应用指出了研究方向.     

粒子群优化算法在电力系统中的应用综述

粒子群优化(PSO)算法是一种新兴的群体智能优化技术,其思想来源于人工生命和演化计算理论,PSO通过粒子追随自己找到的最优解和整个群的最优解来完成优化。该算法简单易实现,可调参数少,已得到广泛研究和应用。在大量参阅国内外相关文献的基础上,简要介绍了PSO算法的工作原理,较为全面地详述了粒子群优化方法在电力系统中的应用,如电网规划、检修计划、短期发电计划、机组组合、负荷频率控制、最优潮流、无功优化、谐波分析与电容器配置、参数辨识、状态估计、优化设计等方面,并对今后可能的应用指出了研究方向。     

Analysis of the purification processes of exhaust gases in a plate electrostatic precipitator taking into account particle entrainment from electrodes

The purification of smoke emissions from ash in the plate electrostatic precipitators is mainly determined by charging, motion and precipitation of the particles in the corona discharge field (“direct” precipitation) and processes of discharge of the already precipitated particles back to the gap (reentrainment). The final processes are studied in a significantly less degree and this limits the possibility to calculate the operation efficiency of the electrical precipitator. The absence of the clear ideas of the physical processes during the reentrainment became the basis for development of methods of calculation using the test results of the industrial units. The representation of the degree of purification and slippage of the particles in the form of the exponential dependence made it possible to specify the relation between the operation conditions of the electrical precipitators and gas purification parameters. A significant role of the ash layer formation on the collecting electrodes is noted; a physical-mathematical model of the processes related with the particlelayer growth and discharge of particles from the electrodes to the hopper is proposed. Analysis is carried out of the electrical forces, which, along with the forces of gravity, cohesion, and adhesion, being about violation of layer stability. The analysis starts with the simplest case of behavior of the particle layer during a sudden switching-on of the field. The processes in the plate electrical precipitators are then considered.     

Maximum loadability of power systems using hybrid particle swarm optimization

The problem of voltage stability is one of the main concerns in the operation of power systems. There are different approaches to estimate the voltage stability of the system. One of these approaches is to find the margin from the current operating point to the maximum loading point of the system. Finding this maximum loading point can be formulated as an optimization problem. This paper utilizes the newly developed evolutionary particle swarm optimization in solving this optimization problem. Details of the implementation of the proposed method to two test systems (Ward-Hale 6-bus) and (IEEE 14-bus) are presented. The results are compared to those obtained by the widely used continuation power flow technique. Good agreement has been obtained proving the validity and applicability of the proposed method.     

Capacitor placement of distribution systems using particle swarm optimization approaches

Capacitor placement plays an important role in distribution system planning and operation. In distribution systems of electrical energy, banks of capacitors are widely installed to compensate the reactive power, reduce the energy loss in system, voltage profile improvement, and feeder capacity release. The capacitor placement problem is a combinatorial optimization problem having an objective function composed of power losses and capacitor installation costs subject to bus voltage constraints. Recently, many approaches have been proposed to solve the capacitor placement problem as a mixed integer programming problem. This paper presents a new capacitor placement method which employs particle swarm optimization (PSO) approaches with operators based on Gaussian and Cauchy probability distribution functions and also in chaotic sequences for a given load pattern of distribution systems. The proposed approaches are demonstrated by two examples of application. Simulation results show that the proposed method can achieve an optimal solution as the exhaustive search can but with much less computational time.     

On the derivation of stored electrostatic energy from a collectionof discrete point charges

This correspondence presents a different perspective on the energy required to position a collection of arbitrary discrete point charges in a space with no externally provided electric field. By examining all permutations of the charge placements, a clear derivation of the familiar result is given, without relying on knowledge of reciprocity     

基于改进粒子滤波的综合能源系统预测辅助状态估计

高效准确的状态估计是综合能源系统安全稳定的基础。粒子滤波具有精度高、对非线性系统适应性强的优点,已应用于电力系统的状态估计中。为提高综合能源系统的状态估计精度,文中提出一种基于改进粒子滤波的综合能源系统预测辅助状态估计方法。首先,构建包含电-热-气网络的区域综合能源系统模型;然后,将粒子滤波算法拓展到电-热-气网络,在粒子滤波相关理论的基础上,针对传统粒子滤波算法存在的跟踪误差问题对粒子滤波的预测步进行改进;最后,利用经典的综合能源系统算例对文中提出的改进粒子滤波算法进行验证。结果证明该方法能够有效解决传统粒子滤波算法的跟踪误差问题,提高系统的估计精度。     

基于改进粒子群算法的电力系统经济负荷分配

提出了一种应用随机优化理论求解电力系统经济负荷分配的新方法,该方法以电力市场全天购电费用最小为目标函数,将高斯算子和交叉算子引入基本粒子群算法中。针对基本粒子群算法（PSO）的局限性,通过引入新的算子,克服了PSO算法前期精度低、后期收敛速度慢、易于陷入局部最优等缺点,在速度和精度上满足了计算要求。算例结果表明,所提出的方法能有效解决电力市场电力系统经济负荷分配问题。     

Metallic particle movement, corona, and breakdown in compressed gasinsulated transmission line systems

A simplified computational algorithm has been developed to study the behavior of metallic particles in gas insulated transmission line (GITL) systems. The model provides an estimate of the effectiveness of particle trapping for a particular trap design at a given commissioning voltage. Results of measured breakdown probabilities of particle contaminated SF₆ show fair agreement with calculated values. A computational model was developed to calculate the corona inception voltage due to conducting particle motion in GITL systems. The computed results for various parameters were in fair agreement with the measured values. A corona pulse pattern is computed and plotted using the same algorithm. Oscillographic records of the transient corona show that particle discharge is larger for long particles, and its magnitude increases with voltage level. Corona patterns obtained in the laboratory indicate that conducting particles can be detected in GITL systems and that the particle size can be determined through partial discharge measurements with AC voltage at different gas pressures     

On bounded-error identification of feedback systems

This paper studies identification of linear feedback systems from closed loop time series. Unfalsified approximate bounded error identification is shown to result in a control-relevant identification methodology for robustness optimization under BIBO-stable coprime factor uncertainty. Furthermore, well-posedness (continuity) of the robustness optimization method for controller synthesis is established.