Neutral Reactor Research Articles

Characteristics of the Current Density Induced Inside a Worker Near a Neutral Ground Reactor

To reduce a high fault current, neutral ground reactors (NGR) were installed in the Korean substation. Current with several harmonic components flows in a NGR due to load unbalance in normal steady state and magnetic fields with several harmonic components are also generated around a NGR. As results of study, we found magnetic fields around a NGR in Korean substation included two harmonics, 180Hz and 540Hz. Magnetic fields of 180 Hz increased 3 times more current density inside a worker near a NGR than same magnitude magnetic fields of 60 Hz. We know a worker near a NGR may not meet ICNIRP guideline of 10(mA/) due to several harmonic components.

Redução das correntes de arco secundário em sistemas de transmissão típicos

Neste trabalho otimizamos o valor de reator de neutro para conseguir minimizar a corrente de arco secundário em sistemas de transmissão com compensação reativa em derivação. Através de uma análise de sensibilidade conseguimos identificar valores de reator de neutro para os quais se consegue uma alta probabilidade de auto-extinção da corrente de arco secundário para diferentes sistemas de transmissão visando assegurar uma manobra abertura/religamento monopolar com sucesso. O método para identificar o reator de neutro ótimo e os valores das correntes de arco secundário para linhas típicas do sistema brasileiro é apresentado.

Investigation of Neutral Reactor Performance in Reducing Secondary Arc Current

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> The majority of transmission-line faults are temporary short circuits. The short circuit arc is usually self-extinguishing after opening the transmission-line circuit breakers. High-speed reclosure of transmission-line circuit breakers can improve system stability. As the voltage level increases, arc deionization time increases as well, endangering system stability. Application of automatic single-phase reclosing makes it possible to increase system stability even for extremely high voltage transmission lines. Automatic single-phase reclosing is used to clear single-phase-to–ground faults, which are about 80% of the transient faults. In order to have successful fast reclosing, different methods are used to extinguish the arc. One of the common methods is to use a single-phase reactor in the neutral of shunt reactor, when transmission line is compensated with shunt reactors. As of now, the effect and parameters of this neutral reactor are usually determined based on the steady-state analysis without exact system and arc modeling. In this research work, the investigation of a neutral reactor application is performed for transposed and untransposed transmission lines using transient simulation with appropriate models. Then, guidelines for selecting the appropriate amount for the neutral reactor are proposed. </para>

Reconfiguration of impulse‐voltage generator for conducting standard lightning tests

PurposeLoading the impulse‐voltage generator by test object can affect the generated voltage waveform. It is well known that reconfiguring these generators by changing the high‐voltage resistors and capacitors, and even the connecting leads in the laboratory is too bulky and time consuming, especially for large test objects. The objective of this paper is to introduce a new computerized method to reconfigure the impulse‐voltage generator in order to conduct the standard tests on any type of objects.Design/methodology/approachA modified algorithm is introduced for solving the generalized equivalent circuit of impulse‐voltage generators under any loading condition.FindingsThe high efficiency of this algorithm has been verified by experimental investigations on different reduced‐ and full‐scale loads, namely, resistive, inductive, capacitive or mixed. For reduced‐scale loads up to a few kV, a single‐stage impulse‐voltage generator is used. While for full‐scale loads, a multi‐stage impulse‐voltage generator is reconfigured to test a 33 kV neutral earthing reactor. The experimental responses are compared with the numerical results of the proposed program and checked out by the PSCAD simulation. Good agreement has been found between all of them.Practical implicationsKnowing the exact value of the test object, some of the generator components and the connecting lead inductances is a must to apply this method.Originality/valueReconfiguring of impulse‐voltage generators by changing the high‐voltage resistors and capacitors, and even the connecting leads in the laboratory is too bulky and time consuming, especially for large test objects. This work will certainly save time and efforts if it is applied correctly in high‐voltage laboratories.

Control neuronal predictivo por linealización instantánea

A Generalized Predictive Control scheme (GPC) is developed, based on a neural model of the process, and then applied on a laboratory neutralization reactor. The neural model, which is obtained previously by identification, is linearized at each iteration of the control algorithm. Hence, the learning capacity of the neural networks and the computer efficiency of the GPC are combined, producing a system with the advantages of a predictive controller extended to non-linear systems, that shows good precision and transient response performance.

Adaptive control of a Wiener type system: application of a pH Neutralization reactor

In this paper the problem of on-line identification and adaptive control of a Wiener type non-linear system is studied. First, a Wiener model is defined whose linear and non-linear parts are described using Laguerre and piecewise linear basis functions, respectively. Then, an adaptive identification algorithm for this model is presented. A local convergence analysis for the adaptive identification is performed. The model obtained is used to adapt the parameters of a controller designed for the specific structure of the model. The complete scheme is applied to a simulation of a pH neutralization reactor subject to several perturbations. The results show the improved behaviour of the proposed scheme compared with other approaches found in the literature.

ADAPTIVE CONTROL OF A NEUTRALIZATION REACTOR

In this paper the problem of on-line identification and adaptive control of Neutralization reactor is studied. It is used the fact that this process can be modeled as a Wiener type system. An recursive identification algorithm for Wiener systems is proposed whose linear and nonlinear parts are modeled using a Laguerre and Piecewise Linear basis functions, respectively. The model obtained is used to adapt the parameters of a controller designed for the specific structure of the model. The results show good performance when compared with other similar schemes found in the literature.

Zig-Zag 결선 및 Open-Delta 방식을 이용한 새로운 고조파 저감장치의 개발

지금까지의 고조파 필터는 중성선 리액터와 지그재그결선의 영상 고조파 전류를 제거하였으나, 부하율에 따라 고조파 저감율이 변하여 경부하에서는 고조파 저감율이 낮아지는 특성이 있고, 중성선 리액터 과열로 중성선 단선 위험의 문제가 발생하였다.<br/> 본 Zig-Zag 결선 및 Open Delta 방식을 이용한 새로운 고조파 저감장치(HANOS)는 Zig-Zag 결선의 Core Block내에 추가로 Open Delta 방식을 결선하여 중성선에 연결함으로써 중성선에 흐르는 영상 고조파 전류가 과열없이 안전하게 제거되는 것을 시험 분석한 결과로 증명하였다.

Design Criteria for Limestone Neutralization at a Nickel Mine

Design criteria were developed for the construction of a full-scale limestone neutralization plant to treat leachate from the waste rock of a nickel mine, using data from laboratory studies, pilot-scale studies, and operation of a full-scale limestone handling and dosing facility. We learned that: limestone powder can be slurried to a constant slurry density of 60 g/L; Fe (II) can be oxidised at low pH (2.5) at a rate of 16.1 g/(L/d) using geotextile as a medium; and that the integrated Fe (II)-oxidation and limestone neutralization process allows neutralization, Fe (II)-oxidation, and gypsum crystallization to take place at the same time, provided that the solids concentration is high (greater than 30 g/L). A full-scale plant with a capacity of 50 m3/h was designed and constructed. The plant consists of the following stages: biological Fe (II)-oxidation, a fluidised-bed limestone neutralization reactor, a complete-mix gypsum crystallization reactor, and a clarifier.

Transmission System Parameters Optimization— Sensitivity Analysis of Secondary Arc Current and Recovery Voltage

This paper shows the importance of optimizing the transmission system parameters from its conception, considering the relevant options and possibilities, in order to have a better cost-performance result. The presented results were obtained in the study of a real transmission system expansion, based on a 865-km long line. The single-phase auto-reclosing (SPAR) procedure was one of the aspects carefully studied, in order to assure adequate transmission reliability. The secondary arc current was mitigated through the traditional solution of using the neutral reactor on the existing shunt reactor banks, which permitted the reduction of the secondary arc current to acceptable values, assuring natural arc extinction and successful SPAR. The method of obtaining the optimized value for the neutral reactor and its implications on the system performance are important aspects, and are discussed in this paper.

Real-Time Application of Scheduling Quasi-Min−Max Model Predictive Control to a Bench-Scale Neutralization Reactor

Scheduling quasi-min-max model predictive control is an MPC algorithm to control nonlinear systems. In this paper, real-time application of the scheduling quasi-min-max MPC algorithm to a bench-scale pH neutralization reactor is presented. The control performance is compared with multilinear model-based MPC and a scheduling IMC-PID controller.

Flexible on‐line Modeling and Control of pH in Waste Neutralization Reactors

AbstractThe control of pH in waste neutralization processes presents a challenging highly nonlinear and time‐varying problem in which the reactor also suffers from inaccessible state information. The ability to characterize the changing dynamics of such reactors is essential to the success of advanced control schemes for these applications. In this work, flexible on‐line modeling of a pH reactor simulating nonstationary behavior was studied. This entailed a comparison of the most popular connectionist learning algorithm, the “Widrow‐Hoff delta rule”, with a classical tool in adaptive identification and control, recursive least squares (RLS). The modeling was pursued within the framework of neural networks using the ADALINE neural network. Further, two heuristically defined first‐principles‐based transforms were investigated for providing “general globally linearizing” information to the ADALINE. The comparisons of the learning algorithms for different neural network information vectors has led to a critical understanding of the flexibility of each algorithm for on‐line learning of the diverse process gain characteristics encountered in pH reactors.

Real-Time Application of Scheduling Quasi-Minmax Model Predictive Control to a Bench-Scale Neutralization Reactor

Abstract Scheduling quasi-minmax model predictive control is an MPC algorithm developed by (Lu and Arkun, 2000) initially for linear parameter varying (LPV) system, then developed for nonlinear systemsin (Lu and Arkun, 2002). In this paper, real-time application of the scheduling quasi-minmax MPC algorithm onto a bench-scale pH neutralization reactor is presented. The control performance is compared with multi-linear model based MPC modified from the algorithm in (Kwon and Pearson. 1978) and scheduling IMC-PID controller in which tuning parameters are from IMC design in (Morari and Zafiriou, 1989).

Real-time implementation of multi-linear model-based control strategies––an application to a bench-scale pH neutralization reactor

The real-time implementation of a set of multi-linear model-based control design methodologies is studied using a bench-scale pH neutralization system that exhibits nonlinear dynamics. It is envisaged that advanced model-based control strategy based on the multi-linear models presents a promising paradigm to design controllers for complex nonlinear plants. The multi-linear modeling philosophy is based on the selection of a set of linear models, complemented with an adaptation mechanism to explain the nonlinear plant behavior in the whole operating range. Practical implications of each control strategy are evaluated and discussed.

Gap Metric Concept and Implications for Multilinear Model-Based Controller Design

The gap metric concept is used within the context of multilinear model-based control. The concept of distance between dynamic systems is used as a criterion for selecting a set of models that can explain the nonlinear plant behavior in a given operating range. The case studies presented include a CSTR and a pH neutralization reactor. The gap metric is used to analyze the relationships among candidate models, resulting in a reduced model set that provides enough information to design multilinear controllers. The simulation and experimental results indicate good performance and stability features.

Multi-linear model-based fault detection during process transitions

Process transitions due to startup, shutdown, product slate changes, and feedstock changes are frequent in the process industry. Experienced operators usually execute transitions in the manual mode as transitions may involve unusual conditions and nonlinear process behavior. Processes are therefore more prone to faults as well as inadvertent operator errors during transitions. Fault detection during transition is critical as faults can lead to abnormal situations and even cause accidents. This paper proposes a model-based fault detection scheme that involves decomposition of nonlinear transient systems into multiple linear modeling regimes. Kalman filters and open-loop observers are used for state estimation and residual generation based on the resulting linear models. Analysis of residuals using thresholds, faults tags, and logic charts enables on-line detection and isolation of faults. The multi-linear model-based fault detection technique has been implemented using Matlab and successfully tested to detect process faults and operator errors during the startup transition of highly nonlinear pH neutralization reactor in the laboratory.

Robust H∞ control of nonlinear plants based on multi-linear models: an application to a bench-scale pH neutralization reactor

This work is aimed at developing a methodology to design controllers for nonlinear plants where desirable robustness and performance properties must be maintained across a large range of operating conditions. The approach is based on the multi-linear model representation and the H ∞ control design that allows inclusion of plant nonlinearities by representing the original system as a set of local uncertain linear plants. To assess the merits of the proposed technique, experiments are performed on a bench-scale pH neutralization reactor. The results demonstrate robust performance and robust stability in the presence of disturbances and set-point variations.

Application of an iterative identification for control scheme to a neutralization process

Abstract In this paper an iterative scheme for identification and control is discussed. During the identification step a plant model which is suitable for the subsequent controller design step is obtained by estimation of the (dual) Youla-parameter from measurements of the input and output of the plant. Using the identified plant model, the frequency response of the ideal controller which perfectly realizes the desired closed-loop response for set-point changes is computed. This controller, in general, may not be realizable or is of high-order. A realizable, low-order controller is then calculated using frequency-weighted approximation. These steps are repeated until the performance of the closed-loop system is satisfactory or cannot be improved further. The proposed scheme is applied successfully to the identification and control of a continuous neutralization reactor.

New Apparatus for the Study of Ion−Molecule Reactions at Very High Pressure (25−700 Torr): A Turbulent Ion Flow Tube (TIFT) Study of the Reaction of SF6- + SO2

A new instrument, the turbulent ion flow tube (TIFT), has been developed for studying ion−molecule reactions up to atmospheric pressure. The instrument is based on the turbulent flow neutral reactor developed by Seeley et al.,8 and it operates under turbulent rather than laminar flow conditions. The TIFT is currently designed to operate at room temperature over a pressure range from approximately 20−750 Torr, although higher pressures are possible with minor modifications. In this initial report, 300 K rate constants and product distributions, measured from 25 to 700 Torr, are presented for the reaction of SF6- with SO2. Both the rate constants and product distributions for this reaction are independent of pressure, and the present results are consistent with previous measurements made at <1 Torr.

Reducing dead time for single-phase auto-reclosing on a series-capacitor compensated transmission line

This paper presents a single-phase auto-reclosing study of a 500 kV Vietnamese transmission line. The success of the single-phase auto-reclosing depends on the extinction of the secondary arc. Therefore, the influences of several factors such as shunt and neutral reactors, faulted phase and location, capacitive and inductive coupling and series capacitor discharge on the extinction of secondary arc are investigated. This paper presents the influence of single-phase auto-reclosing on the transient stability of the Vietnam system. A new method in order to reduce the dead time for single-phase auto-reclosing is proposed.