Disconnect Switch Research Articles

Enhancement of real‐time hybrid simulation on a shaking table configuration with implementation of an advanced control method

SummaryThis paper presents the implementation of Three Variable Control (TVC), an advanced control method, to the existing hybrid simulation (HS) system at the University of California, Berkeley. Motivation, background, and implementation of the TVC are explained together with modifications in the existing HS system. An application, which consists of the real‐time HS of electrical disconnect switches on a shaking table configuration, demonstrates successful implementation of the TVC. The presented application also covers other HS‐related features, namely employment of a three‐dimensional analytical substructure, real‐time HS‐compatible operator‐splitting integration method, and an efficient equation solver for faster computations. Copyright © 2014 John Wiley & Sons, Ltd.

Very Fast Transient Overvoltage Measurement With Dielectric Window

The method of using the electrode inserted into gas-insulated switchgear (GIS) to form a capacitor sensor has the best bandwidth to measure the very fast transient overvoltage. However, the power in the GIS conductor has to be cut off during the repair and replacement of the sensor. In order to overcome the disadvantage, a dielectric window structure is proposed to be installed between the GIS tank and the sensor. The thickness of the dielectric slab is calculated to ensure safety under high SF6 pressure, and the electric characteristics of the dielectric window are carefully investigated to avoid limiting the sensor bandwidth. Moreover, the bandwidth of the measuring system is calibrated under different voltage and frequency. The experimental results demonstrate that the bandwidth of the measuring system with a dielectric window is 6.75 Hz-179.7 MHz, which satisfies the requirement of VFTO recording. Finally, voltage waveforms generated by 252-kV disconnector switch operation are recorded to verify the feasibility of the field application.

New Methods of Damping Very Fast Transient Overvoltages in Gas-Insulated Switchgear

Very fast transient overvoltages (VFTO) are a well-known phenomenon in gas-insulated switchgear. They are mainly generated due to several pre- or restrikes during disconnector switching operations. Since VFTOs may cause complications in substations, a reliable method for damping these transient voltages is of great interest, especially in ultra-high voltage applications. Two new approaches are presented in this paper and compared with a matched radio-frequency resonator, which is an already existing theory. The new methods are an inductive arrangement with surge arrestors and rings of nanocrystalline tape-wound cores. All methods were investigated inside a high-voltage experimental test setup. Therefore, VFTOs with amplitudes of 600 kV and more were generated. The first VFTO amplitude was damped by up to 20%. Even higher damping is possible depending on the damping method and the test conditions. In addition to high-voltage tests and their results, this paper illustrates the theoretical background of all damping methods.

Evaluation of Gas Insulated Disconnector Switch for Bus Charging and Bus Transfer Currents

Abstract Gas insulated disconnector switches (DSs) are employed in a gas insulated substation (GIS) to interrupt and to make capacitive currents, in principle. During switching of capacitive currents very fast transient over-voltages (VFTOs) are common to DS. Intense VFTOs may result in peak voltage close to basic insulation level (BIL) of the connected equipment, leading to progressive deterioration and secondary breakdowns in very high voltage gas-insulated systems. At the same time, arcing during switching of bus transfer currents, by the DS, is considered as a source of substantial amount of decomposed products. This contamination may result in significant reduction in insulation strength of the medium. In order to ensure reliability of the design, it is essential to establish the DS for bus charging and bus transfer current duties under most onerous service conditions through suitable tests. The optimal design of DS to meet these test duties is established with suitable analytical techniques. The tests, which have been discussed and analyzed as part of this study, were performed on an indigenously developed 145 kV gas insulated DS as per IEC 62271-102. A detailed arrangement of the DS (main and auxiliary) and guidelines for conducting the above tests are also explained. Different performance parameters like arcing time, pre-arcing time, secondary discharges, trapped voltages, and level of contamination are analyzed. The behavior of DS during these evaluations is also reported in the present paper. Finally, the effect of different design parameters on performance of the DS has been analyzed.

High‐speed distributed acquisition network for fast transient measurement

In power substations, switching operations of circuit breakers and disconnect switches generate transient electromagnetic emissions, which may interfere with the normal operations of electronic equipments. This study introduces the design of a novel wireless transient measurement system for measuring or monitoring transient electromagnetic emissions in power substations. Unlike traditional transient measurement systems that use several standalone waveform recording equipment, the presented system, adopting novel network measurement concept, works as a truly automatically controlled interactive data acquisition multi-node network, and has the ability to provide time-correlated data from numerous sensors. The accuracy of time correlation is smaller than 1.4 μs. As a result, it provides excellent scalability and is well suited for the measurement of analogue signals spread over a large physical space with time synchronisation. Another major difference is that the new system uses wireless links and programmable devices to replace cables and data acquisition equipment of currently available systems, thus making the new measurement system more compact, flexible and much more powerful. The designed measurement units could do both time-domain measurement and real time spectrum analysis.

Anatomy of a Complex Electrical Failure and its Forensics Analysis

This paper depicts an accident that happened in 2010 in a Brazilian chemical plant. A combination of different events, installations, and commissioning errors coupled with equipment failures involving the primary substation resulted in catastrophic failure. A single-phase failure of a 138-kV disconnect switch, during closing, initiated events and phenomena that resulted in a complete plant shutdown. This paper will walk the reader through the events, forensics analysis, and power system analysis that allowed the authors to identify what happened, how it happened, and what to do to prevent it from happening again. This paper will show how the anatomy of the problem, involving equipment failure, single-phase arcing, switching transients, overvoltage, capacitive coupling, transferred surge voltages, ungrounded system, transient overvoltage due to an arcing ground fault on an ungrounded system, insulation coordination, flashover, and lack of adequate surge protection, all of which resulted in a catastrophic failure of an arc resistant switchgear and a potentially serious arc flash incident. The research followed some steps that will be commented on here as well as the lessons learned.

New Techniques for Disconnector Switching VFT Mitigation in GIS

Switching operations in a Gas Insulated Substations (GIS) generate very fast transient over voltages (VFTO) which are dangerous for the transformer and the system insulation because of their short rise time. Under special circumstances the overvoltages can arise close to the transformer Basic Insulation Level (BIL). The reduction of VFTO amplitudes is considered main challenges. Therefore, VFTO in the 220 kV Wadi-Hoff GIS is analyzed and the worst case for disconnector switching is predicted using EMTP/ATP in this paper. VFTO mitigation techniques are studied in this work. Furthermore, proposed techniques are presented for mitigating the VFTO. The proposed techniques can be used by the maintenance engineers, transformer designers, and GIS insulation manufactures. The results show that the proposed techniques highly reduce the VFTO in a simple manner. DOI: http://dx.doi.org/10.11591/ijece.v4i2.5186

Survey of Induced Voltage and Current Phenomena in GIS Substation

Induced capacitive voltage and current in high voltage GIS substation is one of the most significant phenomena that may have made some problems in this substation operation. At this study the various equipment of 420 KV Karoon4 substations such as powerhouses, input and output lines, bus-bar and bus-duct have simulated by applying EMTP-RV software. Then with the different condition of single-phase and three-phase faults on the lines in critical conditions, capacitive induction voltage and current by parallel capacitor with circuit breaker is surveyed. The results show the value of this induced current and voltage and that this critical conditions the breakers and dis-connector switches must be able to interrupt this value of current.

Analysis of electromagnetic transients in secondary circuits due to disconnector switching in 400 kV air-insulated substation

This paper describes the electromagnetic transients caused by disconnector switching in 400kV air-insulated substation. Transient overvoltages in the secondary circuits of capacitor voltage transformer (CVT) have been calculated using the EMTP-ATP software. The transfer of electromagnetic transients through substation's grounding grid has been analyzed in order to determine the overvoltages at the terminals of protective relays located in the control (relay) room. The overvoltages in secondary circuits have been recorded during on-site test.

Seismic performance evaluation of high‐voltage disconnect switches using real‐time hybrid simulation: II. Parametric study

SUMMARYThis paper presents the results of a parametric study that consists of real‐time hybrid simulation tests of electrical insulator posts on a smart shaking table. A companion paper presents the details of the development and validation of the real‐time hybrid simulation system used for conducting the tests of this parametric study. The purpose of the parametric study presented in this paper is to evaluate the effect of support structure damping and stiffness on the response of disconnect switches with two different insulator materials, namely porcelain and polymer insulator posts. Various global and local response parameters including accelerations, forces, displacements, and strains are considered in this evaluation. The data obtained from the conducted tests show that the maximum insulator response corresponds to the case where the support structure frequency is close to the insulator frequency. An incorporated evaluation of all the response parameters indicates that the stiff support structures constitute the most suitable configuration for both material types of the tested insulator posts. It is also observed that support structure damping has an effect on the response of both insulator types. However, this effect is secondary compared with the effect of support structure stiffness. Copyright © 2013 John Wiley & Sons, Ltd.

Seismic performance evaluation of high voltage disconnect switches using real‐time hybrid simulation: I. System development and validation

SUMMARYThis paper presents the development and validation of a real‐time hybrid simulation (RTHS) system for efficient dynamic testing of high voltage electrical vertical‐break disconnect switches. The RTHS system consists of the computational model of the support structure, the physical model of the insulator post, a small shaking table, a state‐of‐the‐art controller, a data acquisition system and a digital signal processor. Explicit Newmark method is adopted for the numerical integration of the governing equations of motion of the hybrid structure, which consists of an insulator post (experimental substructure) and a spring‐mass‐dashpot system representing the support structure (analytical substructure). Two of the unique features of the developed RTHS system are the application of an efficient feed‐forward error compensation scheme and the ability to use integration time steps as small as 1 ms. After the development stage, proper implementation of the algorithm and robustness of the measurements used in the calculations are verified. The developed RTHS system is further validated by comparing the RTHS test results with those from a conventional shaking table test. A companion paper presents and discusses a parametric study for a variety of geometrical and material configurations of these switches using the developed RTHS system. Copyright © 2013 John Wiley & Sons, Ltd.

Influence of the Switching Speed of the Disconnector on Very Fast Transient Overvoltage

During the switching of disconnectors in gas-insulated switchgear (GIS), repeated strikes occur in the contact gap and lead to very fast transient overvoltage (VFTO). Severe VFTO may bring damage to transformers and other equipment. The switching speed of the disconnector is one of the important factors which influences VFTO. There are still different opinions on this factor. Very little quantitative study was done before this paper. In this paper, the whole repeated strike process associated with the switching operation of the disconnector was simulated and analyzed. The polarity and the probability characteristics of breakdown voltage were analyzed. The impacts of the switching speed of the disconnector on VFTO were studied by statistical methods. Comparisons were made between simulated and measured results. The simulation result shows that within a certain range of speed, disconnectors with a lower switching speed generate lower trapped charge voltage after opening operation and lower VFTO magnitude during the opening and closing operations.

Optimization of Distribution Network

Distribution network is the design of closed loop, open loop operation,which segment equipped with a normally closed and normally open switch contact switch,By changing these disconnect switches and contact switch status, the structure of the distribution network reconfiguration, you can achieve a balanced load, reducing network losses and improve voltage quality role.Distribution Network Reconfiguration in mathematics is a multi-objective high-dimensional nonlinear optimization problem, has a great solution space, using the general optimization method is difficult to obtain a good solution.Existing optimization methods such as optimal flow pattern method, branch exchange method, particle swarm optimization, genetic algorithms, computational efficiency and optimization results in other aspects worthy of improvement.

Measurement of very Fast Transient over Voltages by using MATLAB in a 2-phase various Gas Insulated Substations

Paper deals with MATLAB circuits are develop to purpose for the components of various voltages of Gas Insulated Substations (132KV, 220KV, 400KV) and very fast transient over voltages are calculated by using the MATLAB software for single line to ground fault in a 3-phase system. Very fast transient over-voltage caused by disconnector switching off short bus is investigated in various gas insulated substations. The fast transients over voltages are caused due to switching operations and fault with Fixed resistance and Variable arc resistance. Measurement of very fast transient over voltages due to single line to ground fault in a 3-phase various gas insulated substations (132KV, 220KV, 400KV).

Nanocrystalline to Suppress VFTO and VFTC for 245kV Gas Insulated Substation

Switching of disconnectors (DS) and various faults in Gas Insulated Substation (GIS) causes number of pre-strikes and re-strikes happens. The short duration voltage collapse, traveling surges in busbar causes Very Fast Transient Over voltages (VFTO) and Very fast Transient Currents (VFTC) in the GIS substation. The main challenge is to reduce VFTO and VFTC amplitudes. Several methods have been proposed and examined in the past, such as damping Resistor and Ferrite rings. The VFTO and VFTC damping solutions utilizing damping Resistor, ferrite rings has been analyzed using most popular and widely used software package Electro Magnetic Transient Programming (EMTP). The simulation of mitigation methods like damping resistor and Ferrite rings shows that a damping effect can be achieved. The damping resistor suffers with the difficulty of inserting inside the busduct and the other one is Ferrite magnetic material rings goes easily into saturation, which complicates the design and reduces its general applicability and robustness. This paper investigates the new techniques to suppress the VFTO and VFTC in a 245kV GIS substation by considering the complete substation model for simulation using EMTP. Rings of a Nanocrystalline alloy placed around the GIS conductor were investigated, developed the equivalent model and simulated using EMTP. Prominent results have been achieved with the Nanocrystalline models.

정전비용과 신뢰도 분석을 통한 분할 개폐기의 적정 자동화율 도출 알고리즘에 관한 연구

The addition of disconnect switches to a distribution feeder or the replacement of the manual switches with the automatic switches do, in general, increase reliability by decreasing the duration of the outage of many to the customers on the feeder and reducing the outage section. However, the improvement of reliability in power distribution system causes an increase of the investment cost, for example, replacement costs, labor costs, and so on. For this reason - the balance between investment and reliability improvement - many studies about the appropriate level of investment have been conducted. In this paper, we suggest the algorithm for determining the reasonable switch automation rate in the power distribution system. We evaluate the customer interruption cost and reliability for several cases ? these cases relate with the switch automation rate - in the domestic metropolitan power distribution system, estimate the effectiveness of changing the manual switch to automatic switch quantitatively. These results can help the determining on the disconnect switch’s automation rate.

EMTP Simulation of VFTO’s for 420 kV GIS

Very Fast Transient Over voltages(VFTO) are generated due to switching operations and faults in a Gas Insulated Substation(GIS) needs lot of insight to safe guard the equipment and insulation of various systems. VFTOs can also cause malfunction of protection circuits and control circuits. These transients have traveling wave behavior; they travel to the external systems through enclosures, bushings, cable joints etc., and cause damage to the outside equipment. They can lead to secondary break downs in GIS and may give rise to electromagnetic interference. Thus it is important to develop a suitable simulation models for estimation of these over voltages. In order to estimate the over voltages, equivalent electrical network models are developed. This paper focused on 420 kV GIS system and equivalent model of GIS bus duct have been considered for the simulation of VFTOs. GIS equivalent models have been developed for various lengths of bus duct and simulations to estimate VFTOs are carried out with switching operations of Disconnector switch and fault conditions at various locations. The suppression of VFTOs are also simulated by inserting resistance across the disconnector switch. Comparison has been made in terms of voltage magnitudes with and without suppression methods. Significant reduction of voltage magnitudes are observed in this work. For simulation of equivalent GIS models Electro Magnetic Transient Programming (EMTP) is used.

Analysis of a 66kV Transformer Insulation Breakdown Accident

The total reflection of the wave will occur twice and the lightning over-voltage will be increased by 2 times when the lightning wave along the line reached in the disconnect switch are derived through the analysis of the accident 66kV transformer insulation breakdown. This will lead to the switch breakdown and discharge to be grounded. In this case the breaker is between the arrester and the transformer and the transformer will withstand 2 times arrester residual voltage result in the transformer breakdown. Finally, effective preventive measures combined with the practical experience are proposed.

ANALYSIS OF TRANSIENT ENCLOSURE VOLTAGES IN GIS (EMTP SIMULATION STUDIES)

Abstract Transient Enclosure voltage is special case of very fast transient overvoltages which occurs due to disconnect switch operation or earth ground. Transient Enclosure Voltage appears on external of earthed enclosure of Gas Insulated Systems. Despite of proper grounding, this phenomenon indicates presence of high potentials on Gas Insulted System enclosures so the grounding system impedance is thoroughly examined and designed. In this study EMTP Software is used for analysis. Simulation was done by varying the different parameters. Variations of waveforms of the Transient Enclosure Voltage with various parameters have been studied. Index Terms: Transient Enclosure Voltage (TEV), Gas Insulated System (GIS), Very Fast Transient Overvoltages (VFTO) Transient Ground Potential Rise (TGPR), Disconnector Switch ----------------------------------------------------------------------***------------------------------------------------------------------------ 1. INTRODUCTION

Development Of Unconventional Equipment For Medium Voltage Operations-ENRUTADOR

The four position load break disconnector switch or Enrutador, is the result of a design work, which starts on the actual needs to have simpler, integral, functional and economic technological solutions, for the insertion of transformers in medium voltage networks. In this paper we propose a tentative design for the device and develop the checks that will qualify its suitability and technical feasibility of manufacturing and operation.