kV Gas Insulated Switchgear Research Articles

Mitigating 161 kV electromagnetic potential transformers' ferroresonance with damping reactors in a gas-insulated switchgear

This study presents a successful mitigation experience of ferroresonance (FR) with damping reactors (DR) involving electromagnetic potential transformers (PT) of a 161 kV gas-insulated switchgear (GIS) in Taiwan. PTs have a typically low thermal capacity and high accuracy because of their measuring functions. Low core losses are necessary to obtain high accuracy, but they also reduce its damping ability and therefore increase the possibility of FR. FR happened twice and destroyed PTs for half a year in the study case. Complete FR waveforms of 161 kV PT were obtained via field tests never conducted before in Taiwan. The first field test had a reappearing FR which sustained up to 22.9 s in 11 random operations and the second one confirmed the validity of DR which shortened FR <3.9 s in 12 random operations. A reliable prediction by EMTP/ATPDraw simulation and a useful mitigation method with a proper DR were proved by both field tests and the following 23 months satisfactory operations for 82 times since November 2008. It would prove valuable for further research in higher grade voltage GIS.

362 kV GIB 내에서 건조공기의 절연파괴 특성

In this paper, we studied the dielectric breakdown voltage characteristics by the AC withstand voltage test on using green insulation dry air instead of <TEX>$SF_6$</TEX> insulation gas used in the GIB (gas insulated bus) of 362 kV GIS (gas insulated switchgear). The AC withstand voltage test applied to the standard KEPCO's 362 kV GIB with dry air insulation, and the equivalence of dielectric breakdown voltage for dry air and <TEX>$SF_6$</TEX> gas were examined, and the empirical formulas of dielectric breakdown voltage for dry air were calculated, and the criterion of AC withstand voltage test for dry air insulation was derived. Using the criterion, dry air can be used instead of <TEX>$SF_6$</TEX> gas for 362 kV GIB in the factory acceptance test was confirmed.

Development of SF$_{6}$-Free 72.5 kV GIS

This paper describes the fundamental insulation characteristics of environmentally friendly gases; dry air, N2 and N2 O2 mixed gas. Conventional gas insulated switchgear (GIS) generally uses SF6 as against over 72.5 kV class. We have proposed GIS with a vacuum circuit breaker against from 72.5 kV class to 170 kV class as SF6-free GIS. Because the insulation gas of this type of SF6 -free GIS has the hardly unnecessary current interception performance, the optimal insulation gas can be selected based on fundamental insulation performance. From the standpoints of insulation performance and economical efficiency, we selected compressed dry air as the optimal insulation gas for this type of SF6-free GIS. However, the dielectric strength of dry air is approximately one-third that of SF6 gas. Therefore, to achieve roughly the same size as conventional GIS, some strategies must be employed to enhance insulation performance. This paper investigates the influence of gas pressure and a gas/solid hybrid insulation structure. The insulation performance of the gas/solid hybrid insulation structure using an insulation coating was found to be better than that of a barrier. Moreover, the dielectric strength of particles adhering to a spacer under the compressed dry air was about 1.5 times higher than that under N2. Thus, the high insulation reliability of the gas/solid hybrid structure was high against particles was confirmed. In view of these investigative findings, this type of SF6-free 72.5 kV GIS which was designed and manufactured, was confirmed to comply with the IEC standard.

Recognition of partial discharge waveshape patterns for gas insulated switchgear

Early warning system based on the detection of UHF SF6 partial discharge (PD) signals is a necessary means for the protection of Gas-Insulated Switchgear (GIS) in service as well as the power system to which it is connected. In order to ensure the safe and reliable operation of GIS, it is important to adopt an effective diagnosing method, which is able to identify signals of harmful defects promptly. Unlike approaches such as Fast Fourier Transform (FFT) and Discrete Wavelet Transform (DWT) based techniques, a novel approach to extract discriminative features directly from time-domain UHF signals is introduced in this paper. With the proposed approach, UHF signal waveforms of different sources are partitioned and quantified so that the harmful (SF6 PD) and not-so-harmful (air corona) UHF signals are classified promptly. The investigation is based on the experiment data measured from a 300 KV GIS with encouraging results, which proves the usefulness of this proposed approach.

Electric Field Optimization in 170 kV Gas-Insulated Switchgear Spacer based on Non-Uniform Rational B-spline Curve

In this paper, the electric field at the spacer in a 170 kV gas-insulated switchgear (GIS) is optimized. Initially, the tangential and total electric fields around the original shape of the 170 kV GIS produced by a Korean company are calculated using a combination of the charge simulation method (CSM) and surface charge method (SCM). The contour of the spacer in the 170 kV GIS is found using a non-uniform rational B-spline (NURB) curve the effectiveness of which has been proved. By moving some control points in the NURB curve, the initial shape of the 170 kV GIS can be determined so that we may begin to optimize the electric field. Owing to the proposed algorithm, the overall process has a stable convergence. The objects that we want to design are the upper and lower parts of the spacer. Finally, we can find the shapes in which the tangential and total electric fields are optimized.

Analysis of transient surge transmission characteristics of electronic circuits due to arc discharge generated with disconnector on/off in GIS

AbstractIn gas‐insulated switchgear (GIS), the arc discharge due to a disconnector on/off generates fast transient surges, which can be the cause of malfunction and damage to electronic devices such as microprocessors and AD converters, if the fast transient surge exceeds a specified level. In this paper, it is shown that the comparison and evaluation are realized between the measured results and the calculated ones of fast transient surges generated due to a disconnector on/off in 300 kV GIS by adopting the evaluation index. The calculation is carried out by applying the authors' proposed equivalent circuits using distributed constant lines in consideration of the structure of GIS and a newly developed divided‐type voltage sensor. Also, it is found by using the evaluation index that the measured results and the calculated results are in good agreement with each other. Furthermore, the cause of the occurrence of the peak of the evaluation index is clarified by analyzing the equivalent circuit. And the signal conditioning using a low‐pass filter for electronics circuits connecting the divided‐type voltage sensor is designed. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(2): 34–42, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10360

신경회로망을 이용한 부분방전 신호의 패턴분석

Recently, GIS(Gas Insulated Switchgear) has been recognizing of importance on development of diagnosis technique which is happened problem on confidence for a long time use. Therefore, the measurement and analysis of PD with prior phenomenon of insulation breakdown is used many method of diagnosis for GIS. In this paper, we simulate trouble condition in DS and analysis trouble signal to use electrical and mechanical methods, interpretation of detected signal has analysed with to use ø-q-n pattern and neural network. For this analysis, we have used the induction and AE(acoustic emission) sensors. For the simulation experiment, we make DS for 170 KV GIS and analyze the classification and characteristics of detected signals with the application of neural network algorithm.

Suppression of VFT in 1100 kV GIS by adopting resistor-fitted disconnector

With 1000 kV transmission lines planned in Japan, very fast transient (VFT) phenomena will be suppressed by installing a resistor in a disconnector of gas insulated switchgear (GIS). In this paper the VFT overvoltage suppressing effect of the resistor and the duty required of the resistor are clarified. A 1100 kV resistor-fitted disconnector was tested by constructing a charging current interruption test circuit. It has been clarified that the disconnector accepts the required duty. The disconnector tested is used for the field test.

Investigation on phenomena caused by insulation abnormalities in actual GIS

This paper deals with the results of various insulation fault simulation tests with a 300 kV gas-insulated switchgear (GIS) installed in the field. It covers the levels and patterns of partial discharges generated by various faults and levels to be detected in the field. >

Development of 800 kV gas-insulated switchgear

An 800 kV gas-insulated switchgear, with a capacity level recognized as the largest in the world, was developed as the first development of UHV gas-insulated switchgear, and good results were obtained in the type tests for this switchgear. With the gas circuit breaker and the disconnector used in this gas-insulated switchgear, tests on a scale innovative from a global viewpoint were carried out. Taking recent research into account, test methods were renovated. The long-term reliability of all insulators was demonstrated by submitting them to long-term voltage and current tests. Finally, measuring surges due to the switching of a disconnector and a shunt reactor on the equipment installed at the site, it was verified that measured and calculated values agreed. >

Development of optical instrument transformers

The authors describe the design(, assembly(, and testing results for prototypes of an optical current transformer (CT) and a voltage-dividing-type voltage transformer (PD). The optical CT and PD were developed to be applicable to three-phase enclosed-type 300 kV gas-insulated switchgear (GIS) and air-insulated 168 kV substation systems. Test results for the newly developed optical CT and PD showed that their basic properties conform with JEC 1201, the Japanese standard for electric-power instrument transformers.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Investigation on abnormal phenomena of contacts using disconnecting switch and detachable bus in 300 kV GIS

Using the disconnecting switch and the detachable bus of a gas-insulated switchgear (GIS), rated voltage 300 kV and rated current 2000 A, current and voltage-current tests were conducted in simulation of abnormal contact likely to occur in actual operations, yielding the following results: under the abnormal condition of the arcing contact of the disconnecting switch, continuous arcing occurs with a current above a certain level, resulting in a ground fault. Under the abnormal condition of the main contacts of the disconnecting switch, continuous arcing occurs, resulting in a ground fault if products decomposed by arcing are deposited on the contacts. In conductors of the detachable bus, arcing occurs with current above a certain level if there is a gap between the current-carrying surfaces even when bolts are used. The progress thereafter can be roughly divided into two categories. With narrow gaps between the current-carrying surfaces, the current-carrying surfaces are welded together with the molten metal produced by arcing. With wide gaps between the current-carrying surfaces, continuous arcing occurs. Rapid overheating or arcing at contacts is likely to occur not only when the current is raised by also when sunlight shifts.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Very fast transients in GIS

Different types of very fast transients (VFTs) are classified and their characteristic parameters are summarized based on measurements in a 800 kV SF/sub 6/ gas-insulated pilot installation and 420 kV GIS (gas-insulated switchgear) in service. The electromagnetic field between the enclosure and earth results in a transient enclosure voltage of up to some 10 kV and at the same time in a radiated electromagnetic field from the enclosure with amplitude of some 10 kV/m. The electromagnetic wave guided by the overhead line results in an overvoltage with a multifrequent oscillation of some 10 to 100 kHz, depending on the parameters of the overhead line and the adjacent equipment, e.g. the transformer. The transient enclosure voltage and measures to reduce it are analyzed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Operation of an on-line substation diagnosis system

An online monitoring system applied to a recently built substation is described. It monitors the 204 kV and 72 kV gas-insulated switchgear and the transformer in their normal operating condition. The basic principle used to detect an abnormality is presented together with a record of the system's operation in the first year.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Engineering and Construction of a Gas-Insulated Substation in an Area of Potential Seismic Activity

A large 500/220 kV gas-insulated switchgear (GIS) for bulk power transmission has been installed in the extra high voltage (EHV) network in California. The station is situated outdoors in a region with potential seismic activity, a desert type climate and close to residential areas. These circumstances, together with long and complicated connections to incoming high voltage lines, presented a set of requirements that could best be served by a GIS type of substation. This was the first large EHV GIS to be installed on the Edison system. Experience from design, testing and installation of the GIS equipment is reported, as well as various means to cope with problems and items such as insulation coordination, disconnector transient overvoltages, thermal dimensioning of buses in trenches and seismic dimensioning.