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Controlled Switching of High Voltage SF 6 Circuit breaker
| Content Provider | Semantic Scholar |
|---|---|
| Author | Vasant, Rade Prashant |
| Copyright Year | 2015 |
| Abstract | In controlled switching technology, an effective way to reduce transients produced by switching action, equipment failure preventions, and to inhance power quality, that is, already defined controlled strategies are to close and/or open each independent circuit breaker pole. Controlled switching of high voltage AC gas circuit breaker (GCB) and explains the controlled switching methods that are existing now a days is presented in this paper. Also the paper discusses the merits of controlled switching technology with an application. The accurate prediction of the operating time, subject to the various affecting parameters at that instant. Consistency of CB open and closing time is decides the success of CSS and reliability of CSW device to operate in high voltage environment system. The work presented in the paper focuses on suitability check of the circuit breaker for controlled switching application from mechanical scatter point of view and finds the mechanical scatter window. The allowed circuit breaker scatter for various controlled switching application is discussed in the paper. Keywords— Gas Circuit Breaker, transients, mechanical scatter, suitability for controlled switching INTRODUCTION Energy is one of the major inputs for the economic development of any country. In the case of the developing countries, the energy sector assumes a critical importance in view of the ever increasing energy needs. This is the reason electrical power system network is expanding day by day to serve the increasing energy demand of the nation. Electrical power system comprises of generation, transmission and distribution of electrical energy. Power system should meet following fundamental requirements, System must be able to meet the continually changing load demand of active and reactive power Quality of power supply should meet certain standards in terms of constant frequency, constant voltage and reliability.Generator, power transformer, circuit breaker, surge arrestors, current transformers and voltage transformers are the vital power system equipments. A circuit breaker is protective switching device and hence, it plays a very important role in the power system at the time of abnormal conditions. Circuit breaker is required for the normal switching operation as well. In the EHV and UHV transmission system SF6 gas circuit breakers are used. To maintain the adequate reactive power for voltage control, frequent switching of capacitors and reactors is required through circuit breaker. These are the two applications where transient conditions can occur frequently, which results into electrical and mechanical stresses and sometimes may lead to equipment failure. High current transients associated with uncontrolled energization of capacitors can cause voltage sags, swells on the primary system, which may create problems with power system equipment and customer processes. Any electrical circuit has got resistance, inductance and capacitance parameters. Under steady state condition the energy stored in inductances and capacitances is being transferred cyclically between the L and C of the circuit. When there is sudden change in circuit conditions i.e. switching, redistribution of the energy takes place to meet new condition. This period of redistribution of energy is nothing but the transient. Transients are associated with the excessive currents or voltages. Though the transient period is very short, the circuit components get overstressed during this period and it can lead to an equipment failure, protection mal operation, plant shut down etc. Following are the alternatives for mitigation of electrical transients [4]. Modification of the primary system to reduce the transients eliminating the transients requires that the source of switching transients be addressed. Conventional solutions include. Closing resistors on EHV circuit breakers to control the voltage transient associated with energizing (particularly re–closing) long lines. Circuit breaker pre-insertion resistors for reactor and capacitor switching. Circuit breaker opening resistors for shunt reactor switching. Selecting a specific type of circuit breaker. Surge arresters for limiting the voltage transients. In principle, all primary side solutions incur significant costs and may reduce the overall primary system reliability. The design and mounting arrangements of these systems is very complicated. With the use of pre insertion resistors and reactors, initial transients and bypass transients has to be faced by the power system. Strengthen the primary system to withstand the transients withstanding the imposed stresses requires that system components susceptible to damage or mal operation be configured for greater strength. The International Journal of Engineering Research and General Science Volume 3, Issue 5, September-October, 2015 ISSN 2091-2730 336 www.ijergs.org conventional approach is to design the system components, such as capacitor banks, transformers, and circuit breakers, to withstand the voltage and current transients associated with frequent occurrence of worst case switching phenomena.This is a new method which is becoming popular day by day for the switching transient mitigation. Controlled switching is nothing but switching the load at the optimum point on voltage or current wave so that the transients will be minimum possible. This method Controlled switching has become an economical substitute for a closing resistor and is commonly used to reduce switching surges. The number of installations using controlled switching has increased rapidly due to satisfactory service performance since the late 1990s. Currently, it is often specified for shunt capacitor and shunt reactor banks because it can provide several economic benefits such as elimination of closing resistors and extension of a maintenance interval for nozzle and contact. It also provides various technical benefits such as improved power quality and suppression of transients in transmission and distribution systems. The aim of point on wave switching is to minimize switching transients, over voltages and current surges, thereby reducing the stress on equipment insulation. Controlled switching is the economical method as compared to other conventional methods discussed above. The installation part of controlled switching system is not so complicated as compared to pre-insertion resistors, pre insertion reactors, surge arrestors etc. Controlled switching system comprises of circuit breaker, controller and other auxiliary components like sensors, cables etc. The circuit breaker is one of the vital equipment responsible for the success of controlled switching success. The circuit breaker behaviour in all respect should be known thoroughly, and then only one can feed the information in the controller. LITERATURE REVIEW A paper on ―Controlled Switching of HVAC Circuit Breakers: Application Examples and Benefits‖ by Dan Goldsworthy and Tom Roseburg have detected and investigated Controlled switching technology that is predefined controlled strategies for closing and/or opening each independent circuit breaker pole, is an effective way to reduce switching transients, prevent equipment failures, and improve power quality. The paper presents a tutorial on controlled switching of high voltage ac (HVAC) circuit breakers and describes the controlled switching theory and technology that is in use today. The paper discusses the benefits of controlled switching and shares one utility's applications and experiences with the controlled switching of shunt capacitors, shunt reactors, transformers using modern protective relays and control devices. The paper also discusses how to select the optimum controlled switching times to reduce switching transients. [1]. A paper on ―Identification of Capacitor Switching Transients With Consideration of Uncertain System and Component Parameters‖ by H. Y. Zhu and Chen, this paper described and improved methods for identifying the capacitor switching transient. Capacitor switching transient is one of the most commonly countered power quality distributions. Measuring and identifying these transient remains challenge as the characteristics depend on the system parameter. systematic approach to design and automated system for identifying capacitor switching transients also capable of identifying transients caused by switching of both isolated and back to back capacitors. The proposed method combines the techniques of wavelet transform, rank correlation and fuzzy logic to account for the uncertainties [2]. John Brunke and Klaus Frohlich, suggested a ―Method for Potentially Eliminate Inrush Current Transient By Effectively Transformer Controlled Switching‖. This paper explored the theoretical consideration of core flux transient Transformer inrush currents are high magnitude, harmonic rich currents generated when transformer cores are driven into saturation during energization. These currents have undesirable effects, including potential damage or loss of life to the transformer, protective relay misoperation, andreduced power quality on the system. Controlled transformer switching can potentially eliminate these transients if residual core and core flux transients are taken into account in the closing algorithm. Based on these studies algorithms were developed which allow controlled energization of most transformers without inrush current and concluded it is possible to use residual flux measurements and controlled closing to eliminate transformer inrush transient [3]. ―Overall Benefits of Controlled Switching‖ by Victor F. Hermosillo, proposed a general overview of the benefits offered by the use controlled switching of switchgear HV and EHV electric power system was presented. The benefits of applying controlled switching are technical and economical. Technical benefits include the reduction of the severity of switching transients and their effect on equipment and system life c |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://pnrsolution.org/Datacenter/Vol3/Issue5/44.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
