Switching Surge Research Articles

PROFIL SURJA HUBUNG KARENA PROSES ENERGIZED (PEMBERIAN TENAGA) PADA SALURAN TRANSMISI 500 KV

Yuniarto, in this paper explain that transient over voltage that happened because switching surge have tobe paid attention to don't cause the damage equipments of insulation coordination system. This research aim toperceive the transient over voltage at the end of 500 kv transmission line caused energized process by using EMTP(Electromagnetic Transients Program) as toll to simulate the energized process. Data for this research was takenfrom 500 kv transmission line Ungaran-Pedan. From this research was expected can become a reference for powercompany in planning insulation coordination at transmission line.Result of research show that transient over voltage at the end of 500 kv transmission line caused energizedprocess reach more or less twice its nominal voltageKey word : energized, karateristik, transient over voltage, EMTP

154㎸ 혼합송전선로 재폐로 결정에 관한 연구

This paper describes switching surge analysis on reclosing decision in 154㎸ combined transmission line with power cables. Reclosing should be operated in combined transmission line based on the technical evaluation because of insulation problem of power cable section. If the surge strikes on power cable, the breakdown can occur at week point of cable insulation. Therefore the detailed analysis is required by considering several conditions such as length ratio of power cable, arrester, fault resistance, charging rate and grounding resistance, etc.. In addition, sheath voltage on IJ(Insulated Joint) is analyzed to confirm the protective level. Simulation is performed by EMTP/ATP. Analysis results show that reclosing can be operated without any special problem by the single line-to-ground fault with fault resistance of 1Ω to 50Ω occurred at the overhead transmission section in 154㎸ combined transmission lines and trap charge of 100% and 110%.

Controlled Switching of the T402 Transformer in the Križovany 400kV Substation

Controlled Switching of the T402 Transformer in the Križovany 400kV Substation The paper deals with simulating the circumstances of switching surge and trigger current at switching-in of the T402 autotransformer recently installed in Križovany, with the tests conducted by means of ATP (Alternative Transient Program) simulation software for simulating transient electromagnetic phenomena. The target has been to determine temporal curves for the most critical surge instances against earth and between the phases and the curves for trigger current with and without surge limiters connected, and to determine by means of simulations the size and statistical frequency of switching surges and based on a controlled switching simulation, to describe the elimination of transient phenomena during the process and in reference to the simulations and to operating manual for the PSD02 Siemens control unit, suggest the required configuration settings for the unit.

Effects of Reclosing for Insulation Coordination in 345kV Combined Transmission Lines

This paper describes switching surge analysis for reclosing decision in 345kV combined transmission line with XLPE power cable. Reclosing operation should be decided based on the detailed technical analysis in combined transmission line because this line includes power cable section which is week on insulation. Insulation of power cable can be breakdown at the week point in case of reclosing moment. Therefore the detailed analysis has to be carried out by considering several conditions such as length ratio of power cable section, arrestor, inserting resistance, charging rate, grounding resistance, etc.. On the other hand sheath voltage on IJ(Insulated Joint) is analyzed to check dangerous condition on cable cover. Analysis is performed by EMTP/ATP. Analysis results show that reclosing can be operated as the single line-to-ground fault occurs on overhead line in 345kV combined transmission line, if the inserting resistance is considered before the operation of main circuit breaker.

Probabilistic Evaluation of Optimal Location of Surge Arresters on EHV and UHV Networks Due to Switching and Lightning Surges

Switching surges are of primary importance in insulation coordination of extremely high voltage and ultra-high voltage networks. However, in regions of high lightning activity or high ground resistance insulation design, preferably, should be based on the risk of failure caused by lightning and switching surges and the probability of line outage, a combination of lightning and switching flashover rates (SSFOR). This paper describes an effective installation of transmission line arresters (TLAs) to obtain a better protection scheme (i.e., minimizing global risk to the network). As a consequence, protection costs are reduced in accordance with the costs of elements actually protected and the number of TLAs utilized. In order to accomplish this, a probabilistic method for calculating the lightning related failure and an artificial neural network for estimating the SSFOR are presented. A multicriteria optimization method based on a genetic algorithm is also developed to determine the optimum location of TLAs.

Artificial Neural Networks Used for ZnO Arresters Diagnosis

Lightning arresters provide protection for transmission lines and power equipments. During the occurrence of lightning or switching surges, a voltage level above the equipment insulation level can be reached. An arrester, properly working, is able to limit this voltage level avoiding damages to the protected equipment. A defective arrester may not be able to provide the proper protection level in substations, exposing the equipment and personnel to damage. Monitoring of surge arresters is usually conducted by means of current measurement or thermal images acquisition. But, among power companies, there is no model procedure for the monitoring conduction and analysis of the obtained results. Besides that, when some abnormality is detected, the arrester is replaced by a new one and no further study is conducted to evaluate what kind of problem happened to it. This work proposes a method for analysis of ZnO arresters by the study of failures and usage of artificial neural networks-ANN. The ANN is able to analyze the thermal profile, detect and classify patterns that could be undetected by a visual analysis.

An Efficient Active LC Snubber for Forward Converters

An efficient active LC snubber for forward converters is proposed in this paper. The proposed active LC snubber can be used to reset transformer and suppress switching surge. Further, by storing surge energy in the proposed active LC snubber and then releasing it to the flyback auxiliary output, the converter can achieve high efficiency. For a forward converter with active LC snubber, 91.02%, the maximum output efficiency can be obtained. Because of the high performance on surge suppression and energy recovery, experimental results show that the output efficiency of this proposed converter is higher than that of active-clamped-based converters. Furthermore, for a synchronous rectification forward converter with this active LC snubber, the maximum output efficiency can be further raised to 94.72%.

A Study on the Impact of Low-Amplitude Oscillatory Switching Transients on Grid Connected EHV Transformer Windings in a Longitudinal Power Supply System

Switching events in inter connected power systems have significant effects on EHV transformers. Standard high-voltage lightning and switching impulse tests are performed on EHV transformers during manufacture, to ascertain breakdown strength of insulation used. But, during their service, transformers encounter numerous voltage transients of complex and varying wave shapes which do not necessarily resemble these standard surge type voltages. Transformers are complex assembly of coils around magnetic core having inductances and capacitances and therefore, exhibit unique frequency response characteristics with several natural resonate frequencies. Oscillatory overvoltages originating in power systems due to switching, faults and other phenomena often traverse through transformers and can excite one or more of the winding's natural resonate frequencies resulting severe internal voltage amplification and damage to insulation even when the terminal excitation voltages have relatively low amplitude. Adequate consideration must therefore be given to such low amplitude oscillatory transient voltages while designing insulation for grid connected EHV transformers. In this paper, the authors have analyzed the voltage stresses developed in the windings of a 400/220/33-kV grid connected transformer operating in the Eastern Regional Power Grid of India, when natural frequencies of the transformer winding are triggered by oscillatory switching transients. The developed voltage stresses have been compared with those under standard laboratory dielectric tests including newly incorporated fast front-long tailed switching surges.

Zinc Oxide Surge Arresters and HVDC 125kV-upgrade 500kV Converter Stations -Power Technology of Japan through the Experience of Developments and Applications of Gapless Metal Oxide Surge Arresters-

Gapless Metal (Zinc) Oxide Surge Arresters for a.c. systems contribute to the insulation co-ordination based on the suppression of lightning surges and switching surges. These gapless metal oxide surge arresters using ZnO elements are effective to HVDC systems. This paper describes basic characteristics of ZnO (zinc oxide) elements for d.c. systems and applications of gapless surge arresters to HVDC 125kV frequency converters, HVDC 250kV, upgrade HVDC 500kV converter stations, and HVDC 500kV cables of Japan through the experience of developments and applications of gapless metal oxide surge arresters.

지중배전케이블의 서어지 전파특성 실증연구

가공선로와 지중선로가 혼합된 배전계통에서 뇌서어지와 개폐서어지가 입상주를 통하여 유입될 수 있다. 이러한 서어지는 케이블을 따라서 이동하게 되고 케이블의 종단에서 반사된다. 이때 반사되는 서어지는 그 크기가 2배 정도가 되고 지중배전선로의 절연을 위협할 수 있다.<BR> 한전의 지중배전계통을 모의할 수 있는 모델계통을 만들고 이 계통에 서어지를 인가하여 케이닥의 서어지 전파 특성을 측정하였다. 실제시험으로 측정한 결과를 EMTP 해석 결과와 비교하여 EMTP 파라미터들을 수정하였다.<BR> EMTP해석에서 케이블 절연체의 유전율, 피뢰기의 특성곡선, 서어지의 파형을 조정하면 실증시험 결과와 거의 일치하는 결과를 얻을 수 있었으며, 케이블의 말단에서 2배 정도 전압상승이 되고 분기에 의하여 복잡하게 전파되는 것을 확인하였다.

Quantitative evaluation of lightning surge range voltage–time characteristics in high‐pressure SF6 gas

AbstractGas‐insulated switchgear (GIS) is subjected to very fast transient overvoltages such as lightning surges or disconnector switching surges. Therefore, the sparkover voltage and time (V−t) characteristics of SF6 in a very short time range of less than $1\ \mu \hbox{s}$ are of great interest from the viewpoint of insulation design and coordination for a GIS. This paper describes the V−t characteristics of SF6 at a gas pressure of 0.5 MPa using a steep‐front square impulse voltage under a quasi‐uniform field gap and presents a quantitative evaluation of the V−t characteristics for a nonstandard lightning impulse voltage. In the case of a square impulse, the V−t characteristics of positive polarity were observed to be almost flat over a long time range from 80 ns to $10\ \mu \hbox{s}$, and rose steeply over a short time range from 80 ns down to 20 ns. For negative polarity, the V−t characteristics exhibit a gentle rise from 200 ns down to 40 ns. In the estimation of V−t characteristics, the equal‐area criterion parameters were quantitatively estimated using the square impulse. For a nonstandard lighting impulse, we found that application of the equal‐area criterion with these parameters for the nonoscillating impulse and oscillating impulse of up to 5.3 MHz as a model of lightning surge and disconnector switching surge is possible. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(4): 8– 17, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20309

EMTP를 이용한 멀티레벨 인버터 구동 고압유도전동기에서 발생하는 과도과전압 저감필터의 효과분석

본 논문에서는 인버터 구동 고압유도전동기 운전시 스위칭 서지로 인하여 고압유도 전동기 단자에서 발생하는 과도과전압을 저감하기 위한 필터로 인버터 출력단자에서 dv/dt를 저감하는 LCR 필터와 전동기 입력단자에서 케이블과 유도전동기 특성임피던스를 매칭시키는 RC필터에 대한 과도과전압 저감특성을 분석하였다. 이 필터를 고압에 대용량 유도전동기에 적합하도록 EMTP(ElectroMagnetic Transients Program)를 이용하여 모델링 및 케이블 영향에 의한 필터의 과도과전압 저감효과를 전압파형과 고조파 스펙트럼으로 비교분석하고, 이를 토대로 고압 대용량 유도전동기에 사용될 필터를 제시하였다. 인버터 스위칭 서지에 의한 과도과전압은 유도전동기 고정자 권선에 심각한 전압 스트레스를 발생시켜 절연파괴를 일으키는 주요원인이 된다. 이러한 과도과전압을 저감위한 필터설계는 고압유도전동기 시스템에서 필수적인 요소임을 보였다. 또한 제시된 필터는 과도과전압을 효과적으로 저감시키는 것을 EMTP 시뮬레이션을 통하여 입증하였다.

Experience of Numerical Protective Relays Operating in an Environment With High-Frequency Switching Surge in Japan

This paper intends to provide general information about the experiences of numerical relay operation under many different kinds of surges from switchyards in Japan. The main focus of this paper is to investigate the immunity of numerical relays against a switching surge with relatively high frequency in a gas-insulated substation that is considered to be severe for the relay's correct operation. It is concluded that the reliability of today's numerical relays in Japan against the switching surge is almost sufficient due to the effectiveness of the immunity test standard adopted and countermeasures against the switching surge in Japan.

Unusual overvoltages caused by the generating effect of induction motors

An overvoltage phenomenon that occurred at a nuclear power station in Taiwan is investigated. Simulations of the event reveal that two individual low-frequency overvoltages were caused by the interaction of induction motors (with flywheels) with the power line capacitance after they had lost power. Although these low-frequency overvoltages are insufficient to cause the failure of a circuit breaker they could have caused sufficient damage to the bushing insulation of the breaker that when a subsequent switching surge could cause the failure of the breaker. This failure lead to a blackout event.

Fundamental Characteristics of Y123 Thin Film for Switching Surge Current to Design SCFCL

Superconducting Fault Current Limiters (SC-FCLs) have been expected not only to reduce fault current but also to improve power system stability. For introducing them, various kinds of characteristics, such as trigger current level, must be examined. They should be designed not to be triggered by switching surge that comes from out of the target section. In this paper, fundamental characteristics of SCFCL for surge current have been studied. Y123 thin films with Au protection layer on sapphire substrate have been prepared, and the voltage-current characteristics have been measured. The measurements have been carried out by use of the impulse and sinusoidal currents to evaluate the characteristics of Y123 thin film for switching surge. The relation between operational current levels and their operational times and the relation between operational current levels and the wave front times are shown in the paper. These characteristics are useful for designing the SCFCL which will not to be triggered by switching surge.

高気圧SF&lt;sub&gt;6&lt;/sub&gt;の雷サージ領域V&amp;mdash;t特性の定量的評価

Since gas-insulated switchgear (GIS) is subjected to very fast transient overvoltages such as lightning surges or disconnector switching surges. Therefore the sparkover voltage and time (V-t) characteristics of SF6 in a very short time range of less than 1μs are of great interest from the viewpoint of insulation design and coordination for a GIS. This paper describes the V-t characteristics of SF6 at a gas pressure of 0.5MPa using a steep-front square impulse voltage under a quasi-uniform field gap and presents a quantitative evaluation of the V-t characteristics for a nonstandard lightning impulse voltage. In the case of a square impulse, the V-t characteristics of positive polarity were observed to be almost flat over a long time range from 80ns to 10μs, and rose steeply over a short time range from 80ns down to 20ns. For negative polarity, the V-t characteristics exhibit a gentle rise from 200ns down to 40ns. In the estimation of V-t characteristics, the equal-area criterion parameters were quantitatively estimated using the square impulse. For a nonstandard lightning impulse, we found that the application of equal area criterion with these parameters for the non-oscillating impulse and oscillating impulse of up to 5.3MHz as a model of lightning surge and disconnector switching surge is possible.

Insulation Design of Prefab Insulating Covers in Overhead Distribution Lines Concerning the Protection from Animal Contacts and Surges

In order to prevent the accidents due to the contact of animals, trees and etc., prefab insulating covers are installed in overhead distribution lines. However, sufficient effect is not realized. To make their protection performance at high level, they should to be designed taking the combination with the lightning protection equipments into consideration. With arrestors, they are required to withstand the lightning and switching surges smaller than the operation voltage of the lightning arrestors. With high-speed circuit breakers, as the breakage by the lightning surge is permitted and the following current is intercepted, the covers should withstand the switching surge when the lines are re-closed. In this study, the impulse-withstand voltage of a gap between the conductor and the contact object was examined assuming that the conductor cover and the prefab insulating cover were damaged. And the authors proposed a design method of the prefab insulating cover by comparing the withstand voltage of the air gap with the operation voltage of the arrestor and the magnitude of the switching surge.

A Novel Prototype of Auxiliary Edge Resonant Bridge Leg-Link Snubber-Assisted Soft-Switching Sinewave PWM Inverter

This paper proposes a new circuit topology of the three-phase soft switching PWM inverter and PFC converter using IGBT power modules, which has the improved active auxiliary switch and edge resonant bridge leg-commutation-link soft-switching snubber circuit with pulse current regenerative feedback loop as compared with the typical auxiliary resonant pole snubber discussed previously. This three-phase soft switching PWM double converter is more suitable and acceptable for a large capacity uninterruptible power supply, PFC converter, utility-interactive bi-directional converter and so forth. In this paper, the soft switching operation and optimum circuit design of the novel type active auxiliary edge resonant bridge leg commutation link snubber treated here are described for high power applications. Both the main active power switches and the auxiliary active power switches achieve soft switching under the principles of ZVS or ZCS in this three-phase inverter switching. This three-phase soft switching commutation scheme can effectively minimize the switching surge related electromagnetic noise and the switching power losses of the power semiconductor devices; IGBTs and modules used here. This three-phase inverter and rectifier coupled double converter system does not need any sensing circuit and its peripheral logic control circuits to detect the voltage or the current and does not require any unwanted chemical electrolytic capacitor to make the neutral point of the DC power supply voltage source. The performances of this power conditioner are proved on the basis of the experimental and simulation results. Because the power semiconductor switches (IGBT module packages) have the relation of the trade-off in the switching fall time and tail current interval characteristics as well as the conductive saturation voltage characteristics, this three-phase soft-switching PWM double converter can perform to improve actual efficiency in the output power ranges with a trench gate controlled MOS power semiconductor devices which is much more improved to the low saturation voltage. The effectiveness of this is verified from a practical point of view.

Reignition Surge Effect in a Vacuum Circuit Breaker on Induction Motor Using the PSCAD/EMTDC

When switching off an induction motor by Vacuum Circuit Breaker, it would damage the motor insulation by switching re ignition surges. In order to investigate switching surge effects on motor insulation the simulations as parameters of cable length, motor size, with/without arrester around the Vacuum Circuit Breaker are performed by a Vacuum Circuit Breaker model that was developed by authors using the PSCAD/EMTDC. And the switching reignition surge profiles are obtained. Based on the surge profiles, the proper locations of the surge arrester for the protection of induction motor in distribution system are proposed. The results would be useful to analysis the re ignition surges effects and to select adequately the location of arrester in the distribution system.

High-Efficient High Frequency Linked Zero Voltage Soft Switching PWM DC/DC Power Converter with ON/OFF-Assisted Synchronous Rectifier Scheme

Advanced development of the high frequency pulse modulated DC/DC power converters are indispensable in order to achieve smaller size, higher performances of the power supplies. In resent years the problems of the electromagnetic noise generation caused by the hard-switching pulse width modulation (PWM)—based high frequency operation of the switching power devices have been significant, including switching losses and switching surges. As result a variety of soft-switching power conversion circuit technologies have been attracted special interests for reducing switching power losses and minimizing electromagnetic interference. The soft-switching pulse modulation of DC/DC power circuit topologies can be divided into continuous current mode resonant type and quasi-resonant voltage mode type. The soft-switching DC/DC converters, a continuous current mode zero current soft-switching (ZCS) DC/DC converter with pulse frequency modulation (PFM) has been already put into a practical use. In this sort of power converters soft-switching commutation can be achieved over wide load variation ranges and high stability can be also performed, but high current peak stress through power semiconductor devices arises, however, and it causes relatively large increase of conduction power losses in the power semiconductor devices, high frequency transformers as well as rectifier diodes. As a result, the problem of a high efficiency for DC/DC power converter could not still unsolved.Thereupon, in this paper, quasi-resonant voltage mode based soft-switching PWM DC/DC power converter with a high frequency transformer link is presented, which has on/off assisted synchronous rectifier in its secondary side. The PWM operation of this converter is described in comparison with conventional one. Due to using power MOSFET as on/off assisted synchronous rectifier in the secondary side of the high frequency isolated transformer, it is possible to achieve stable zero voltage soft-switching (ZVS) conditions from no load to the rated load for minimum requirement of a magnetizing current. As result of a high value of the magnetizing inductance design, the power converter actual efficiency of this converter can be designed so as to above 97% in experiment. Moreover, results of a switching losses analysis are discussed from an experimental point of views in this paper. The effectiveness of the power converter treated hare is proved from a practical point of view by using 32kHz-2.5kW breadboard setup.