Gas-insulated Switchgear Tank Research Articles

Attenuation Characteristics and Time Delay of PD Electromagnetic Wave Propagation in GIS Systems

Modeling of electromagnetic wave propagation inside a gas-insulated switchgear structure can be helpful for understanding and improving the utilization of partial discharge detection by providing information to help determine more optimal positioning of ultra-high frequency sensors. This paper studies the effect of insulating spacers, L- and T-type structures on electromagnetic wave propagation by simulating the time dependent wave propagation behavior for these arrangements within a gas-insulated switchgear busbar geometry. The attenuation characteristics and time delays produced by spacers, L- and T-type structures for partial discharge electromagnetic wave propagation behavior are presented. Emphasis is placed on comparison of attenuation characteristics and time delay between different observation points along the busbar both before and after the 90° bends formed by L- and T-type structures. Moreover, a comparative analysis of the radial electric field at the gas-insulated switchgear tank and its rate of change with time is also conducted. The paper demonstrates that if the location of the ultra-high frequency sensor is chosen appropriately based on knowledge of the physical structures, the attenuation effects introduced by L- and T-type structures could be reduced.

Partial Discharge yang Merusak Isolasi SF6 pada Gas Insulated Switchgear (GIS) Tiga Fasa Pengaruh Keberadaan Partikel Asing

This paper analyzes the effect of the presence of foreign particles on an equilateral arrangement of 3 phase gas insulated switchgear (GIS) insulation equipment. Gas Insulated Switchgear (GIS) that uses SF6 insulation, partial discharge will occur as the insulation ages and there are several other factors that affect the insulation. Partial Discharge needs to be detected to avoid failures that cause damage to equipment in theGIS. In this calculation, the electric field characteristics will be analyzed in 3-phase equilateral GIS by varying the location of the particles in the GIS tank. Particles are modeled to have a length of 5 mm and a thickness of 0.5 mm located in a 3 phase GIS equilateral arrangement with a tank diameter of 150 mm and a conductor diameter of 25 mm. The electric field calculations are reviewed at several points in the 3-phase equilateral GIS tank. The simulation and calculation of the electric field were calculated with FEM method software. The results of the calculations show that thereare differences in the characteristics of the electric field between normal GIS and GIS where foreign particles are present. The difference in these characteristics can be seen in the magnitude of the electric field, and the ratio of eccentricity from some point of view.

Chromatic processing for feature extraction of PD-induced UHF signals in GIS

Partial discharge (PD) detection is an effective means of discovering insulation faults in gas-insulated switchgear (GIS). One of the most extensively used methods in PD detection has historically been the ultrahigh frequency (UHF) method. This study evaluates the chromatic processing methodology and its key factors for feature extraction of UHF signals in GIS. Three types of artificial defects are installed in the GIS tank at 0°, 90°, and 180°, respectively. The features of the UHF signals are extracted in the chromatic space, and PD discrimination of the defects is achieved. The influences of processors are studied before the feature selections are suggested. The time-stepping method is proposed to determine the rules of UHF signal frequency characteristics that vary with time. Finally, the process and options of the chromatics-inspired methodology are summarized.

Resin injection behavior in process of manufacturing insulation spacer with permittivity gradient using computational fluid dynamics

The advent of new technology for designing insulation materials with desired properties stimulates our interest in development of insulation spacers in gas-insulated switchgear (GIS). Tailoring of two kinds of epoxy-based composite materials (resins) with different relative permittivities enables development of insulation spacers with graded permittivity that decrease the diameter of a GIS tank. Computational fluid dynamics for the resin injection process based on the properties of resin mixtures at various mixing ratios between two resins with high/low relative permittivity enables us to estimate the injection behavior and distribution of resins in the manufacturing of insulation spacers. Simulation results demonstrated the gradient of resins in the insulation spacers by this resin injection method using two resins. In particular, the insulation spacer formed by two or four injection inlets have a more favorable distribution of resins than that achieved by one injection inlet.

Partial Discharge Recognition with a Multi-Resolution Convolutional Neural Network

Partial discharge (PD) is not only an important symptom for monitoring the imperfections in the insulation system of a gas-insulated switchgear (GIS), but also the factor that accelerates the degradation. At present, monitoring ultra-high-frequency (UHF) signals induced by PDs is regarded as one of the most effective approaches for assessing the insulation severity and classifying the PDs. Therefore, in this paper, a deep learning-based PD classification algorithm is proposed and realized with a multi-column convolutional neural network (CNN) that incorporates UHF spectra of multiple resolutions. First, three subnetworks, as characterized by their specified designed temporal filters, frequency filters, and texture filters, are organized and then intergraded by a fully-connected neural network. Then, a long short-term memory (LSTM) network is utilized for fusing the embedded multi-sensor information. Furthermore, to alleviate the risk of overfitting, a transfer learning approach inspired by manifold learning is also present for model training. To demonstrate, 13 modes of defects considering both the defect types and their relative positions were well designed for a simulated GIS tank. A detailed analysis of the performance reveals the clear superiority of the proposed method, compared to18 typical baselines. Several advanced visualization techniques are also implemented to explore the possible qualitative interpretations of the learned features. Finally, a unified framework based on matrix projection is discussed to provide a possible explanation for the effectiveness of the architecture.

UHF Signal Processing and Pattern Recognition of Partial Discharge in Gas-Insulated Switchgear Using Chromatic Methodology.

The ultra-high frequency (UHF) method is widely used in insulation condition assessment. However, UHF signal processing algorithms are complicated and the size of the result is large, which hinders extracting features and recognizing partial discharge (PD) patterns. This article investigated the chromatic methodology that is novel in PD detection. The principle of chromatic methodologies in color science are introduced. The chromatic processing represents UHF signals sparsely. The UHF signals obtained from PD experiments were processed using chromatic methodology and characterized by three parameters in chromatic space (H, L, and S representing dominant wavelength, signal strength, and saturation, respectively). The features of the UHF signals were studied hierarchically. The results showed that the chromatic parameters were consistent with conventional frequency domain parameters. The global chromatic parameters can be used to distinguish UHF signals acquired by different sensors, and they reveal the propagation properties of the UHF signal in the L-shaped gas-insulated switchgear (GIS). Finally, typical PD defect patterns had been recognized by using novel chromatic parameters in an actual GIS tank and good performance of recognition was achieved.

Finite‐difference time‐domain simulation of partial discharges in a gas insulated switchgear

It is important to estimate the current magnitude and charge amount of a partial discharge (PD) in a gas-insulated switchgear (GIS). In this study, electromagnetic fields generated by a PD in an 84 kV-class three-phase GIS for testing have been measured with a voltage probe installed on the outer surface of an insulation spacer of the GIS tank, and the corresponding simulations have been carried out using the three-dimensional finite-difference time-domain (FDTD) method. FDTD-computed time-domain voltages across spacers agree reasonably well with the corresponding measured ones, and the current magnitude of PD and its charge amount have been estimated.

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.

The Influence of L-Shaped Structure on Partial Discharge Radiated Electromagnetic Wave Propagation in GIS

To clarify the propagation process and improve the utilization of ultrahigh frequency (UHF) technique in partial discharge diagnosis, the propagation characteristics of electromagnetic wave in different directions in an L-shaped gas insulated switchgear tank are profoundly investigated in this paper. According to the property of electric field distribution and attenuation curves of the UHF signal, the influence of L-shaped structure is analyzed.

Partial Discharge Pattern of Various Defects Measured by Spiral Antenna as UHF External Sensor on 66 kV GIS Model

This paper deals with partial discharge (PD) measurement in gas insulated switchgear (GIS) using spiral antenna as UHF external sensor. PD detection in UHF band is effective because it detects electromagnetic (EM) wave induced by PD with high S/N ratio. External sensor was used to detect leaked EM wave signals from insulation spacer of GIS tank. The experiment was conducted in 66 kV GIS model with metal type spacer. There is insulation window in the spacer. PD was generated by some artificial defects in GIS and an external PD source. The leaked EM wave propagated through spacer aperture was measured using spiral type sensor without filter and amplifier. The peak to peak value (Vpp) and the transmission rate of electromagnetic wave signals were evaluated. The PD patterns were observed. The results showed that the PD was detected by the spiral antenna. PD pattern was unique for each defect. These results are considered to be useful for enhancement of database PD diagnosis.

Suppression of Metallic Particle Lift‐Off in GIS by a Nonlinear Resistivity Coating

SUMMARYTo suppress metallic particle lift‐off in compact gas‐insulated switchgear (GIS), a coating with nonlinear resistivity characteristics was developed for the inner surface of the GIS tank. An electrical field analysis that measured the current density and electric field (J–E) characteristic indicates that a nonlinear resistivity coating can reduce field intensification at triple junctions between metallic particles and the coating, and can effectively suppress particle lift‐off. The results of experiments using a GIS mock‐up model indicate that a nonlinear resistivity coating increases the lift‐off electric field of metallic particles with less statistical dispersion than a dielectric coating.

Investigation of the Evaluation of the PD Severity and Verification of the Sensitivity of Partial-Discharge Detection Using the UHF Method in GIS

The measurement of partial discharge (PD) using ultra-high frequency (UHF) method is considered an effective approach to monitor the online condition of the equipment, which is used to facilitate the detection of incipient defects in gas-insulated switchgear (GIS). In this paper, in order to assess the severity of PD defects using UHF method, the actual 220-kV GIS were subjected to experimentation. The PD was measured simultaneously by using the UHF method and the IEC60270 measurement technique. The combined measurement has been carried out on different defects in PD test cells, including the floating metal, metallic protrusion, and void in epoxy resin. The inner coupler installed in the GIS tank, and the outer coupler placed outside the spacer, are used to measure the UHF signal. The relationship of the apparent charge and the amplitude of the time-domain signal, and the integral energy from 300 MHz to 1.6 GHz of the signal induced by PD in GIS are analyzed thoroughly. In this way, the severity of PD can be quantified using the UHF signal. In addition, to verify the sensitivity of the UHF detection method, a pulse generator with a rise time of about 500 ps is designed. The GIGRE method for the verification of sensitivity, which is used worldwide, is applied in the experiment. The results of the pulse generator experiment are compared to the results produced by the actual discharge sources, and several possible approaches of improving this method are proposed.

Proposal of evaluation test method for withstand performance under residual DC charge at GIS insulator

AbstractIn recent years, compact gas‐insulated switchgear (GIS) has been developed by rationalization of specifications. All of the GIS have been checked for passage of the AC and lightning impulse (LI) withstand test, but DC stress that occurs on an AC GIS spacer when switching devices are operated has not been sufficiently investigated. Since the electrical field strength inside a GIS tank is stronger in compact GIS, it is increasingly necessary to evaluate the withstand performance of GIS spacers under residual DC voltage. Under DC stress, electrification strengthens the electrical field strength at the creepage surface (Et) and the withstand performance of GIS spacers depends on the maximum value of Et (Etmax). When the volume resistivity at the surface layer of spacer is uneven, Et strengthens at the uneven spots. In this paper, Etmax under DC stress with uneven volume resistivity at the surface layer of the spacer is investigated, and an evaluation test method for withstand performance under residual DC charge is constructed. © 2012 Wiley Periodicals, Inc. Electr Eng Jpn, 179(1): 21–28, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21233

Influence of disconnecting part on propagation properties of PD-induced electromagnetic wave in model gis

Partial discharge (PD) detection using a UHF (ultra high frequency) band signal is a well known advanced insulation diagnosis method in gas insulated switchgear (GIS), and has been actively studied. Detailed investigation of electromagnetic (EM) wave propagation inside the GIS tank is required for significant improvement of detecting PD signal by UHF method. When practically applying the UHF method to GIS insulation diagnostics, it is necessary to examine the effects of GIS components such as circuit breakers, isolators and disconnectors on EM wave propagation properties. In this paper, attention is paid to the effects of a disconnecting part of a high voltage (HV) conductor like a circuit breaker or a disconnector in GIS. To examine the effects of disconnecting part, the gap length of the disconnecting part was set as parameter, and waveforms and frequency spectra of the propagation PD-induced EM wave were measured with UHF sensors. For the purpose of discussing the effects of the disconnecting part theoretically, a finite difference time domain (FD-TD) simulation was also carried out. The experimental results show that the PD-induced wave could propagate through the disconnecting part with higher frequency components over the cutoff frequency components of TE11 mode for disconnecting part, i.e. cylindrical shape formed by GIS tank without HV conductor. The propagation of the lower frequency components below the TE11 mode depended on the gap length of the disconnecting part.

Detecting characteristics of various type antennas on partial discharge electromagnetic wave radiating through insulating spacer in gas insulated switchgear

A widely used, effective method for diagnosing the insulation of a gas-insulated switchgear (GIS) is to detect partial discharges using signals in the ultrahigh frequency (UHF) band. To detect partial discharge signals that propagate inside a GIS, it is necessary to install a sensor inside or set on the outside of a GIS tank. For GISs that have already been constructed, it is effective to use external diagnosis using electromagnetic wave (EM-wave) signals that radiate (leak) from the insulation spacer of the GIS tank, and there is strong demand for such a diagnosis technology. Externally leaking EM-waves are often detected using an antenna, and multiple antennas supporting different frequency bands are commercially available. The accuracy of external diagnosis could be improved by comparing and evaluating the characteristics of various antennas. The insulation spacer of a GIS tank is usually installed on the flange and fastened with metal bolts. GIS tanks are made electrically continuous by these metal bolts and have the same grounding potential. EM-waves leak from the part of the solid insulator surrounded by these metal bolts and the GIS tanks. This leaking part forms a slot antenna and has a resonant frequency that depends on the spacing between the bolts in the circumferential direction of the flange. At this resonant frequency, the output of externally leaking EM-waves is higher and enables more sensitive measurement. In this study, the detection characteristics with different antenna positions and directions were compared in consideration of the number and positions of the bolts on the spacer, and the frequency characteristics of various antennas were obtained. To improve the detection sensitivity, a prototype of an improved dipole antenna was fabricated and its characteristics were evaluated. Based on the experimental results, an ideal diagnostic system based on the externally leaking EM-waves is proposed.

Development of an identification system for location of free metallic particles in GIS based on analysis of Lamb waves

AbstractWe investigated propagation properties of Lamb waves in a gas‐insulated switchgear (GIS) tank to diagnose insulation performance of GIS. The acoustic signals excited by a free metallic particle colliding with the tank sheath were measured using AE sensors. The wavelet transform was applied to decompose the wave data into its time–frequency components. As a result, difference of propagation properties of Lamb waves is clearly seen with different sizes of GIS tank. Based on the characteristics of Lamb waves, algorithms for location identification of a free metallic particle were examined in model GIS using two AE sensors. Herein, we propose a new system for location identification of a free metallic particle in GIS. Moreover, it is verified that the new identification system is suitable as a diagnostic technique for GIS. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 167(3): 28–35, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20676

Electromagnetic wave radiated from an insulating spacer in gas insulated switchgear with partial discharge detection

As a means of diagnosing partial discharge (PD) signals propagate inside a gas insulated switchgear (GIS), a study for the leakage of electromagnetic waves (EM-waves) emitted from the insulating spacer was implemented. The EM-waves leaking out from the solid insulator have the resonance frequencies depend on the spacing between adjacent bolts in the direction of the flange circumference, because the leakage portion is the equivalent of a slot antenna. In this paper, using an electromagnetic analysis model which has a simulated spacer on a concentrically-shaped GIS tank, the output characteristics of the EM-waves that leaked out from the slit were analyzed under various conditions such as the spacing between adjacent bolts, the width of the spacer, the dielectric constant of the spacer and the form of the flange. Also the actual measurement by the experimental equipment used to simulate the model was implemented for comparison with the analytical results. Consequently, the optimal specifications of the sensor and the measurement method used to achieve highly-sensitive detection for practical use were summarized and proposed as well as evaluating the effectiveness of the electromagnetic analysis model adopted in this paper.

ＧＩＳ絶縁スペーサの直流残留電荷に対する耐圧性能評価試験法の提案

In recent years, compact size gas insulated switchgear (GIS) has been developed from rationalization of specifications. All of the GISs have been checked to pass the AC and lightning impulse (LI) withstand test, however, DC stress that occurs on the AC GIS spacer when switching devices are operated has not investigated enough. Since electrical field strength for inside of GIS tank is more strengthen for compact size GIS than ever, it is more necessary to evaluate the withstand performance for GIS spacer under residual DC voltage. Under the DC stress, the electrification of charges strengthen the electrical field strength at creepage surface (Et) and withstand performance for GIS spacer depends on the maximum value of Et (Etmax). When volume resistivities at surface layer of spacer are uneven, Et strengthen at the uneven spot. In this paper, Etmax under DC stress with uneven volume resistivities at surface layer of spacer is investigated, moreover, the evaluation test method for withstand performance under residual DC charge are constructed and proposed.

Partial discharge diagnosis method using electromagnetic wave mode transformation in actual GIS structure

The diagnosis algorithm using ultra high frequency (UHF) method with the higher-order electromagnetic wave (EM-wave) was examined as the advanced partial discharge (PD) diagnosis method in a gas insulated switchgear (GIS) in the former paper. Previous studies evaluated the characteristics of EM-waves propagated in a simple coaxial cylindrical pipe, or through an L-shaped or a T-shaped pipe formed by combining these. In the present study, components (a hand hole, a post-type spacer, etc.) present in an actual GIS structure were identified, and an evaluation done mainly through an analysis on what effects their presence has on the mode transformation of EM-waves propagated inside a GIS tank. The direction in which a GIS tank is bent is horizontal (0deg) in the L-shape structure. If there is either a post-type spacer or a shield ring inside, and the signal source is in the 0deg direction, the distribution of the EM-wave strength varied according to through the L-shape structure. Also in the case of a T-shaped structure, the distribution of the output after signals are transmitted through the T-shaped junction varied depending on each component. Based on these characteristics, the diagnosis algorithm for PD with higher-order mode EM-waves was improved taking into account the effects of various components existing in an actual GIS, and a PD diagnosis method more suitable for an actual structure was established.

Propagation Characteristics of Higher-order Mode Electromagnetic Signals in Coaxial GIS Model with Various Conditions of Arch-shaped UHF Sensor

Partial discharge detection using a UHF band signal is a well known advanced insulation diagnosis method in gas insulated switchgear (GIS), and has been well studied. In contrast to conventional diagnosis with lower frequencies in the kHz range, UHF band signal above the cutoff frequency has been detected with higher-order modes that only appear in electromagnetic signal propagating inside the GIS tank. This is because the wavelength of UHF band signals is comparable to the GIS tank size. The authors had observed the characteristics of such higher-order electromagnetic waves with a focus on the resonance characteristics of the TE11 mode, using a disk-shaped UHF sensor with the sensor extending into the inside of the tank. The purpose of this paper is to investigate the propagation characteristics of higher-order mode waves in a coaxial GIS model. Considering application to actual equipment, it was investigated that the output of a sensor with an arch-shape not extending into the inside of the tank, which has less influence on the propagation mode of the inner electromagnetic wave. In the frequency domain below the cutoff frequency of the TE11 mode, the output characteristics were almost independent of the installation position of the UHF sensor, but in the higher frequency domain the output power displayed discontinuous increases at some frequencies. It was also studied that the circumferential dependence of sensor output. For higher-order modes resonant characteristics appeared that depended on the tank length, and it was recognized that the electric field distribution inside the tank influenced the output of the UHF sensor at resonant frequencies. Further, it was found that installing a spacer inside the tank shifted resonant frequencies and the influence of the spacer consistent with the relationship between the spacer position and the electric field distribution inside the tank.