Electric artery guardian Dual defense line of insulation and sealing

Electric artery guardian

Dual defense line of insulation and sealing

TPS

In the "energy castle" of the transformer, the bushing is like a precise passage through the city wall, which not only has to withstand the impact of internal oil pressure, but also isolates the disturbance of the external environment. As a key component connecting the winding and the power grid, the performance of the bushing directly determines the operational safety and service life of the transformer.

Analysis of sleeve structure

Modern transformer bushings adopt a multi-layer composite structure design, with the core conductive rod made of electrolytic copper or aluminum alloy, and the outer layer wrapped with cross-linked polyethylene (XLPE) or capacitive oil immersed paper insulation layer. The metal flange and porcelain sleeve are fixed with special sealant to form a stress cone structure with gradient electric field distribution, effectively controlling the phenomenon of surface discharge. This sandwich structure enables the sleeve to simultaneously meet the triple requirements of conductivity, insulation, and mechanical support.

##Main text: The insulation medium filled inside the casing varies depending on the type: oil immersed casing uses mineral oil combined with multi-layer insulation paper, GIS casing uses sulfur hexafluoride gas, while dry casing relies on epoxy resin casting technology. The dielectric constant and thermal conductivity of different media directly affect the partial discharge level and thermal stability index of the casing

In terms of electrical performance, the bushing needs to withstand a power frequency withstand voltage test of up to 1.5 times the system voltage, and its capacitance distribution needs to match the transformer winding to ensure voltage equalization under high-frequency overvoltage. The specially designed umbrella skirt structure can increase the flashover voltage by more than 30% by increasing the creepage distance. The built-in end screen grounding device can effectively monitor the dielectric loss factor and provide data support for preventive maintenance.

In terms of mechanical strength, the casing needs to withstand bending loads of 30kN or more without deformation. When designing for earthquake resistance, it is necessary to consider the horizontal acceleration condition of 0.4g in areas with an earthquake intensity of level 8. The sealing system must ensure an annual leakage rate of no more than 0.1% under temperature fluctuations of -40 ℃ to 105 ℃, to prevent the insulation medium from deteriorating due to moisture.

Selection and Operation Points

The selection should focus on the matching of BIL (Basic Impulse Insulation Level) and PDIV (Partial Discharge Initial Voltage) parameters. Areas above an altitude of 2000 meters require a 1.2-fold altitude correction factor calculation. It is recommended to use silicone rubber composite casing designed to resist salt spray in coastal areas, and corrosion-resistant polytetrafluoroethylene coating products should be selected in chemical areas.

During the operation and maintenance phase, it is necessary to establish an infrared thermal imaging database, and start the diagnostic program when the temperature difference exceeds 2K. If the acetylene content exceeds 1 μ L/L in oil chromatography analysis, disassembly inspection is required. The new fiber Bragg grating (FBG) monitoring system can achieve real-time sensing of strain and temperature, warn potential faults 3-6 months in advance, and reduce unplanned downtime by more than 65%.