Detecting abnormal heat in porcelain post insulators using infrared thermal imaging （ITI） stands as a principal approach for diagnosing fault in post insulators within substations. A lightweight ...target detection model for infrared images of porcelain post insulators is proposed based on computer vision. First， a dilated convolutional kernel is added to the depthwise separable convolution to effectively increase the receptive field of the output unit and reduce the number of parameters. Then， the obtained D-Mobilenet network structure is used to replace the backbone network ELANCSP in YOLOv7， and the SJS （shear， jitter， scale） method is used to expand the number of samples， and algorithms including transfer learning， Mosaic data augmentation， and cosine annealing are introduced to improve the model's generalization ability. Finally， the performance of the model is compared with YOLOv4， YOLOv5， YOLOv7， and the G-Adaboost target detection algorithm. Experimental findings demonstrate that this model boasts a supe
High-voltage pillar-type porcelain insulators are important components of power plants and substations, and are widely used in power grids. In recent years, various kinds of accidents caused by ...breakage of pillar insulators have occurred frequently during the operation of the power grid, posing a serious threat to the safe operation of the power grid. Aiming at the problem of the deterioration detection of porcelain strut insulators in transmission lines, this paper introduces the detection principle of vibro-acoustic method and the vibro-acoustic detection process of porcelain strut insulators. A set of vibro-acoustic-based porcelain strut insulator detection equipment is studied and designed, and its design principle is expounded. And hardware components, the effectiveness of the detection function is verified through the actual measurement analysis, which provides support for the follow-up research and promotion of this detection technology.
In this article, a 2.5m five-stage inductive power transfer (IPT) system based on domino cylindrical solenoid coupler (CSC) compensated, respectively, in layers is proposed. The system is considered ...to be used as 220 kV post insulators application, transferring power for sensors and measuring instruments of smart grids. The distributed series compensation method is applied to double-layer CSC. Compared with the two types of parallel schemes, this method can significantly reduce the current of the main circuit. Compared with the concentrated series compensation method, this method can effectively reduce the resistance caused by the stray capacitance. The interaction between the post insulator and the magnetic coupling structure is analyzed. The circuit model of the system with constant voltage output characteristics is analyzed. A prototype with a maximum efficiency of 66.7% is built. When the power is transferred to a larger value of 77.8W, the efficiency can still reach 62%. Comparing with previous works, the wireless distance is extended while the efficiency is improved.
Overhead line design utilizing composite line post insulators requires an understanding of the insulator mechanical load carrying capabilities in multiple simultaneous directions. This paper covers ...the development of combined loading curves and offers guidance on the presentation of such curves so that informed decisions regarding the selection of composite line posts can be made.
•A decohesion simulation model of the epoxy-insert interface is proposed.•The fracture of the insulators occurs in the semi-conductive adhesive layer.•A crack starts at the maximum curvature of the ...epoxy-insert interface.•The three-post insulator failure depends on strength of the maximum curvature epoxy.
Mechanical weakness is one of the most important factors causing the fault of a three-post insulator in the GIL, and a common failure location is the epoxy-insert interface of the insulator. In this paper, three-post insulators in a 550 kV GIL with no defect, a debonded defect and an air gap in the epoxy-insert interface are employed as samples, respectively. An adhesion simulation model and a decohesion simulation model of the interface are established. Failure mechanism of the insulators under radial loads is studied by the numerical simulation and the experimental measurement. The experiment results illustrate that the fracture of the insulators under radial loads occurs in the semi-conductive adhesive layer and conforms to the brittle fracture. The adhesion simulation model is suitable for interface simulation before the fracture, and the decohesion simulation model is suitable for interface simulation in fracture process. Compared with the defectless insulator, fracture strength of the insulator with a 1 mm thickness debonded defect decreases sharply by 71.3%, while that of the insulator with an air gap of 1 mm diameter and 5 mm height decreases slightly by 4.9%. Combined with the simulation results, the fracture process of three-post insulators under radial loads could be inferred as follows: a crack appears as soon as the stress of the epoxy around the maximum curvature of the epoxy-insert interface reaches its tensile failure strength, after that the crack quickly extends along the inner of the peripheral epoxy and the bottom of the interface until finally fracture. In other words, the failure of three-post insulators under radial loads depends on the tensile strength of the epoxy around the maximum curvature of the interface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
HVAC GIL bears strong electric field and complex mechanical stresses during operation. As one of the main components of the GIL, tri-post insulators are often subjected to bursting breakdown ...accidents, which threatens the reliability and safety of HVAC GIL. In this study, based on a scaled-down HVAC GIL model, the mechanism of breakdown of tri-post insulators under the action of electromechanical coupling was experimentally studied. And the influences of external force, fixing mode and defect location on the breakdown morphologies were investigated. Results show that partial discharges (PD) caused by the initial defects of the tri-post insulator can develop into bursting breakdown, producing internal cracks inside the post and open cracks on its surface. Tensile stress promotes the defect evolution, while compressive stress does the opposite. The mechanical stress distribution inside the tri-post insulator is influenced by the external force and the fixing mode, resulting in distinct breakdown morphologies. Due to the stronger electric field, defects on the GND electrode are more prone to develop into breakdown than that on the HV electrode. Results of this study can provide a reference for tracing the origin of bursting breakdown faults as well as optimizing the parameters for designing tri-post insulators.
Surface charge and electric field distributions of a tri-post insulator in ±800-kV gas-insulated transmission line (GIL) are calculated under the superimposed dc-impulse voltage and the polarity ...reversal voltage. The theoretical discharge inception voltage of the tri-post insulator under the abovementioned conditions is estimated by the volume-time theory. The accumulated homocharges on the insulator surface significantly relax the electric field at the dc steady state, thus improving the theoretical discharge inception voltage under dc superimposed homopolar impulse voltage but reducing that under dc superimposed heteropolar impulse voltage. When the voltage polarity is reversed in two minutes, the intensified electric field on the insulator surface shifts from the grounded (GND) electrode toward the vicinity of the high voltage (HV) electrode, in which the maximum electric field grows by 21.4% and increases as the reversal time shortens. The micro-discharge around the particle trap may induce the accumulation of heterocharges on the insulator surface between the lower two posts, aggravating the electric field distortion in the surrounding region and degrading its insulation performance.
DC wall bushing is one of the key equipment in high-voltage direct current (HVDC) transmission project. At present, post insulators based on epoxy composites are widely used for supporting insulation ...in SF 6 -insulated apparatus. However, the flashover faults caused by surface charge accumulation can be a severe threat to the long-term operation of the post insulators under dc field. Therefore, the issue of charge accumulation on epoxy post insulators in HVDC wall bushing and its effect on flashover has been widely concerned. Aiming at this problem, the flashover characteristics of epoxy samples in SF 6 gas under polarity reversal conditions with dc voltage prestressed for 10-600 min were measured in this article. The flashover process is analyzed through surface charge distribution measurement and electric field computation. The results show that with the increase of prestressed time, the accumulated negative charge density could reach <inline-formula> <tex-math notation="LaTeX">-14.8\,\,\mu \text{C}/\text{m}^{{2}} </tex-math></inline-formula>, which led to a 12% increase in maximum field strength. As a result, the polarity reversal flashover voltage could decrease by 12% and the flashover time delay could decrease by 84.6%. This article can offer as a reference for the effect of surface charge accumulation on flashover in SF 6 gas-insulated equipment.
One of the most important insulating components for developing a 154 kV superconducting fault current limiter (SFCL) is post insulator, which supports 154-kV SFCL modules in a cryostat. In order to ...design an optimum post insulator, the top priority is to determine the creepage distance of post insulator. In our previous research, surface flashover voltages along smooth glass fiber reinforced polymer (GFRP) rods immersed in liquid nitrogen (LN2) were experimentally investigated. To reduce the cryostat volume, ribbed post insulators with increased creepage path were then considered. However, due to difficulties with producing ribbed GFRP post insulators, ribbed specimens were made of polytetrafluoroethylene instead. Four kinds of test specimens were prepared to determine the position and the number of ribs attached to the surface. From the experimental results, it was found that the ribbed insulator has shown better insulation performance in LN2 and number of ribs could affect the surface flashover voltage of post insulator. Consequently, ribbed model for 154-kV SFCL post insulator was designed and successfully tested. Finally, real 154-kV SFCL system with newly designed ribbed post insulator was installed and Basic Impulse Level (BIL) test and ac required withstand voltage were successfully carried out.
Abstract
This paper makes a statistical analysis of the common faults of GIS equipment, and discusses the causes, hazards and maintenance methods of the four common faults: SF6 gas leakage, SF6 gas ...micro water exceeding standard, partial discharge caused by internal insulation breakdown and component defects.
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