Controlled Switching of Reactive Loads and Commisioning Regimes

Switching is a vital task in any power system for ensuring its safe and reliable operation. Switching may be necessary for fault clearance, to ensure wider system stability and to prevent damage to plant. It is essential for isolation, to allow technicians to carry out maintenance tasks safely. Also, switching of reactive loads such as shunt capacitor banks and shunt reactors, is crucial for controlling system voltage. Switching of some loads however, may produce voltage transients and heavy transient inrush currents which can impact on wider system power quality, impact customers and cause damage or deterioration of the insulation of HV equipment. Therefore, it is important to provide some form of measure to control or mitigate transients caused by switching. The main control measures include: metal oxide surge arrestors, pre-insertion resistors, current limiting reactors and synchronised or controlled switching. Controlled switching is the favoured solution for frequently switched loads such as reactive plant, for economic benefits and as it reduces transients in the first instance. Controlled switching is defined as the use of electronic equipment to control the making or breaking of high voltage circuit breakers at pre-determined points on the system voltage and current waveforms. It has been implemented in Ireland for over 30 years for the energisation of shunt capacitor banks. Over the last two years, the benefits of controlled switching for different applications has become ever more apparent, with increased use such as switching of transmission shunt reactors and the energisation of large power transformers, particularly in remote areas of the network such as wind farm interfaces. The aim of this thesis is to provide a complete overview of the stages concerned in implementing controlled switching schemes, from examining the impacts of switching certain loads, to performing systems studies, up to site commissioning stage. The research in this thesis looks at both the theory and practice. It draws together the published work, manufacturers guidelines, international standards and simulation results, to give the total awareness of the issues involved in reactive load switching and commissioning regimes. The various solutions and strategies associated with controlled switching schemes are examined, to ensure that the best and most economical solution has being implemented. Several recent projects where controlled switching has been implemented for switching of transmission reactors and power transformers are also investigated

Development of a Circuit Breaker Health Index Algorithm and Real-time closed-loop Testing

Modelling an electric arc within a circuit breaker, sending it to an IED and outputting it to a COMTRADE file. With the COMTRADE, develop an algorithm to create the Health Index of the circuit breaker. This allows to evaluate the condition of various circuit breakers based on COMTRADE files

Impacto de modelos del arco eléctrico de un interruptor de potencia en un sistema eléctrico

Para la correcta operación y protección de los sistemas eléctricos de potencia se hace necesario el uso de un interruptor de potencia diseñado para operar en condiciones nominales, igualmente soportar grandes corrientes relacionadas con diferentes fallas eléctricas. En el instante en que se realiza la apertura del interruptor se generan unas condiciones severas, de orden transitorio, al momento de operar el interruptor se genera un fenómeno conocido como arco eléctrico. Para realizar el análisis del arco eléctrico en un sistema de potencia se disponen de varios modelos, para el desarrollo de este trabajo se tomó como referencia las propuestas matemáticos de arco eléctrico desarrollados por Habedank (1993), Modelo de Shavemaker (2000), y KEMA (1992). Es importante dejar en claro que los principios de Cassie y Mayr constituyen la base de los demás modelos de arco eléctrico que se han venido desarrollando al través de la historia; en este trabajo se hace una adaptación del modelo de Shavemaker.For the correct protection and operation of the electrical power systems its necessary the use of breaker designed to operate at nominal conditions, also support large currents related to different electrical failures. At the moment that is make breaker opening generated transitional severe conditions, when operating the switch a phenomenon known as electric arc is generated. For do the analysis the electric arc in a power system of various models are provided for the development of this work was taken as reference the proposed mathematical electric arc developed by Habedank (1993) Shavemaker model (2000), and KEMA (1992). It is important to make clear that the principles of Cassie and Mayr form the basis of other electric arc models have been developed to throughout history; in this work a model adaptation Shavemaker is made. Due to advances in the informatic systems also have been developed the information and communication technologies have become indispensable tools for the development of knowledge, in this case, in the field of electrical engineering educational software MatLab, and extension Simulink, used in this work in order to analyze the behavior of a subject to the effect of the electric arc produced by the operation of the circuit breaker, making observations of current and voltage against time, plus network voltage fluctuations. To do analyzes and compares the models developed by Habedank, Shavemaker and KEMA. The results generated in this word suggest the importants of simulation models, given that when the power is higher does not affect much the model with respect to the initial parameters model Habedadnk, is the model comparison, for lower earnings one but not too close to zero, shavemaker improved model, is the best model that throws the simulation. According to the observations made, and in comparison, can be expressed as recommended for the power system model is the model shavemaker

Environmental Compatible Circuit Breaker Technologies

Recent research and development in the field of high-current circuit breaker technology are devoted to meeting two challenges: the environmental compatibility and new demands on electrical grids caused by the increasing use of renewable energies. Electric arcs in gases or a vacuum are the key component in the technology at present and will play a key role also in future concepts, e.g., for hybrid and fast switching required for high-voltage direct-current (HVDC) transmission systems. In addition, the replacement of the environmentally harmful SF6 in gas breakers and gas-insulated switchgear is an actual issue. This Special Issue comprises eight peer-reviewed papers, which address recent studies of switching arcs and electrical insulation at high and medium voltage. Three papers consider issues of the replacement of the environmentally harmful SF6 by CO2 in high-voltage gas circuit breakers. One paper deals with fast switching in air with relevance for hybrid fault current limiters and hybrid HVDC interrupters. The other four papers illustrate actual research on vacuum current breakers as an additional option for environmentally compatible switchgear; fundamental studies of the vacuum arc ignition, as well as concepts for the use of vacuum arcs for DC interruption

A New Cost Effective Approach to Suppress Very Fast Transients on Power Transformers Connected to Gas Insulated Substations

This thesis investigates the feasibility of a new method to prevent internal resonance in transformers connected to gas insulated substation due to very fast transient overvoltage in the GIS. The possibility of utilizing a cost effective RC surge suppressor to prevent internal transformer resonance is analyzed and the optimum suppressor in terms of capability to suppress high risk frequencies of VFTO is proposed. In comparison with other existing methods, the proposed method is a simple and cost effective method

Modelization and analysis of the electric arc in low voltage circuit breakers

246 p.Tesis doctoral que presenta un nuevo modelo de arco eléctrico para interruptores de baja tensión mediante simulación FV y validación experimental

Modelling of High Voltage Circuit Breakers Considering Interaction between the Driving Mechanisms and Switching Arcs

With the increase of voltage and current ratings, design and test of circuit breakers have become more demanding. This is a consequence of the technical difficulties and costs in performing development tests as well as the complexity resulting from the coupling of different physical mechanisms in shaping the interruption performance of a breaker. It is well known that the performance of a circuit breaker is determined by many design and operational parameters among which the motion characteristic of the contact is a key factor. Since the motion characteristic of the contacts has a direct impact on breaker performance, it plays a critical role in the design of a circuit breaker. Difficulties in performing tests or experiments under high voltage and power have rendered the traditional ‘cut and try’ design approach impractical. Computer simulation on the other hand, with its cost-effective and easy-to-implement nature, has become the favored approach to achieve design optimization and attracted a great amount of attention in the field of electrical engineering. An arc simulation model (Liverpool arc model) has been developed in this research group together with a circuit breaker simulation interface, featuring PHEONICS as the differential equation solver. Valuable information can be extracted from arc simulation results and help design better optimized prototypes. However, the absence of a driving mechanism model in the current arc simulation model limits its effectiveness and functionality. The travel of the contact could affect the flow cross section in the arc chamber as well as the length of the arc, and ultimately the performance of the circuit breaker. Additionally, the interaction between the arc chamber and driving mechanism, which has a significant impact on the result (most prominent under high current and long arc duration), has also been overlooked in the existing model. Previously, the absence of a driving mechanism model is dealt with by providing the simulation with a user-defined text file containing the travel profile of the moving contact. However, a user defined file may not reflect the true motion of the moving contact due to the unaccounted interaction between the arc chamber and driving mechanism. Consequently, a truly coupled simulation model, which is capable of calculating the travel of all moving components in real time and eliminating any inaccuracies in the predefined travel curves, is needed. In the current research, an approach to quantify the interaction between the arc and driving mechanism has been proposed. Collectively, the resistive force (known as reaction force) imposed on the moving components in the arc chamber by the high-pressure gas can be calculated by a newly developed integral method. The existing arc model has been expanded to incorporate the calculation of reaction force. In addition, a functional mathematical model for the ZF-11-252 (L)/CYTA hydraulic driving mechanism has also been developed, based on which a number of sensitivity studies have been carried out and the key design parameters that affect the dynamic characteristics of the driving mechanism identified. Considering both the driving mechanism model and the improved arc model (which can now calculate reaction force based on the pressure distribution in the arc chamber) a coupled circuit breaker simulation procedure has been established together with an interface which facilitates the information exchange between the driving mechanism model and the arc model. Based on this coupled model, the interaction between the arc and the driving mechanism is studied under different arcing conditions and nozzle geometries. In particular, two important factors affecting the accuracy of the predicted travel characteristics of the moving components have been identified through the studies. The first one is the need to consider the variable contact surface area between the piston rod in the hydraulic cylinder and the oil as a result of the motion of the piston. The second factor is the prediction accuracy of the pressure field around the moving components in the arcing chamber, especially when there are strong pressure waves propagating in the arcing gas. These aspects have not been studied so far

Suppression of electrical discharges

SF6 (Sulphur HexaFluoride) gas is exclusively used as a dielectric insulator and arc quenching medium in high voltage power networks. The electronegative properties of the gas and its ability to recombine after dissociation make it a gas of choice for high voltage equipment. However, SF 6 is a greenhouse gas and therefore research is needed to find an alternative. This thesis explores the potential of PolyTetraFluoroEthylene (PTFE) powder as a dielectric insulator. This has been deployed in a compacted form and when buoyant in air. This approach opens up new avenues for existing research related to gaseous dielectrics and current interruption through the utilisation of small particulates made from insulating materials. A detailed database, of breakdown voltage signals and high speed camera shots, has been compiled to facilitate comparative analysis of the effect of airborne polymer (e.g. PTFE) powders on breakdown voltage across different gap widths, relative to SF6. The breakdown voltage results which were obtained from experimental tests to demonstrate an effect on the voltage withstand that these airborne materials have comparable to that of SF6. Also, their ability to suppress electrical discharges between dielectric probe contacts is also demonstrated during the course of this thesis. In addition, a combined electrical/optical system has been constructed in order to investigate the relationship between airborne particle concentration and the resultant breakdown voltage between electrodes. The optical system was tested using smoke particles prior to its utilisation for powder particles. For both smoke and powder systems, chromaticity was utilised to assess changes in particle density. A model was used to interpret the optical signal and thereby estimate the concentration of airborne particles. This employs factors such as the refractive index, particle radius and essentially the ratio of the light source intensity as seen through the container with scattering particles to the intensity of the same light source seen through the same container without scattering particles

Fluid Dynamics Calculation in SF6 Circuit Breaker during Breaking as a Prerequisite for the Digital Twin Creation

The requirements to switching the capacities of SF6 circuit breakers submitted by Russian Grid companies are difficult to satisfy. The first limitation is related to material and financial costs in order to create a new requirement-satisfying switching device. The second limitation is dictated by the necessity of calculating complex physical processes in a circuit braker interrupter during fault–current making or breaking before creating a prototype. The latter task is reduced to the problem of simulating the processes of interaction between the switching arc and the SF6 gas flow. This paper deals with the solution of the problem both analytically by a special method and numerically by a numerical software package through the creation of a mathematical model of the interaction process. The switching arc is taken into account as a form of a temperature source, based on experimental data on measuring the temperature of the arc column. The key feature of the research is to use the finite element method based on a moving mesh—the Arbitrary Lagrangian Eulerian (ALE) method. Such a problem statement allows us to take the contact separation curve of the circuit breaker into account as the input data of the model. The calculations were carried out during fault-current breaking by a 110 kV SF6 dead-tank circuit breaker. The calculations of pressure and mass flow in the under-piston volume change, gas flow speed, and temperature depending on the contact separation are given. The proposed model of the switching arc was used to simulate the process of 25 kA symmetrical fault–current breaking and was compared with an experiment. © 2023 by the authors.Ministry of Education and Science of the Russian Federation, Minobrnauka: FEUZ-2022-0030The research was carried out within the state assignment with the financial support of the Ministry of Science and Higher Education of the Russian Federation (subject No. FEUZ-2022-0030 Development of an intelligent multi-agent system for modeling deeply integrated technological systems in the power industry)