Electrical Tracking,Erosion and Fire Retardancy Performance of Silicone Rubber Insulation Containing Aluminum Trihydrate,Graphene and Glass Fiber Additives

Silicone rubber composite is a priority electrical insulating material used in high-voltage outdoor insulation applications.Low electrical tracking/erosion and poor flame resistance performance of silicone rubber once ignited,substantially reduce its working life.This paper attempts to investigate tracking/erosion performance of room temperature vulcanized(RTV)silicone rubber along with flame retardant parameters using aluminum trihydrate(ATH),graphene nanosheets(GN)and milled glass fiber(GF)additives.The inclined plane test(IPT)was performed in line with criteria defined in IEC 60587 using step-up tracking voltage method while flame retardancy is evaluated according to ASTM E 1354.0 using a cone calorimeter.Results suggest 30% of ATH assists in improving physical tracking/erosion resistance of pristine silicone elastomer rubber by impeding development of leakage current and a great reduction in maximum average temperatures on the surface of RTV2.Further improvement in performance of RTV2 is achieved through introduction of 1%of GN and 5% of GF as seen in RTV4.Moreover,30% of ATH reduces heat release rate and smoke production rate,and this trend is improved with the introduction of GN/GF.RTV4 has pop up as the most promising silicone rubber composite with excellent electrical tracking,erosion,and flame resistance performance relative to its counterparts in this study.

Surface Charging Phenomena on HVDC Spacers for Compressed SF_(6) Insulation and Charge Tailoring Strategies

Surface flashover of spacers is a key factor limiting the application of HVDC GIS/GIL,while the charge accumula-tion on the surface of the spacer could have a potential adverse effect on the surface flashover voltage.This paper discusses the laws regarding distribution patterns of surface charges and the related mechanisms.The field-dependent property is discussed in detail to comprehensively illustrate the charge transport mecha-nism and explain the research differences regarding different surface charge patterns obtained by previous researchers.In addition,the main surface charge control methods for epoxy resin are summarized and discussed.The potential research directions of charge control methods and key points in manufacturing of spacers used in HVDC GIS/GIL are also explored.

Impact of Accelerated Ultraviolet Weathering on Polymeric Composite Insulators Under High Voltage DC Stress

This study investigates the weatherability of room temperature vulcanized(RTV)silicone rubber(SiR)and epoxybased material specimens with a composition of different nano and micro fillers against the collegial effects of high voltage DC,UV and temperature stresses.Bulk power transmission over long distances via HVDC is considered an economic option these days,so to ensure the system reliability,it is also critical to investigate these insulators under DC stress along with other environmental stresses(especially UV and temperature).For experimentation,composite samples i.e.neat epoxy(NE),epoxy with 15%micro SiO_(2)(EMS),epoxy with 5%nano SiO_(2)(ENS),neat SiR(NS),SiR with 15%micro SiO_(2)(SMS)and SiR with 5%nano SiO_(2)(SNS)are fabricated and subjected to accelerated aging in a weather chamber for 3,360 hours.Results reveal that SMS and SNS offer better hydrophobic behavior followed by EMS.However noticeable surface discoloration in the form of whitish shade with minor blackish spots is found in the case of SMS,while remaining samples also showed considerable color fading.Scanning electron microscopy(SEM)and Fourier Transform Infrared Spectroscopy(FTIR)results showed that SNS and SMS presented quite excellent resistance to the exposure of fillers.Hardness and weight of all specimens are evaluated throughout the experiment and particularly for the water immersion test.Moreover,leakage current analysis indicated that SNS and SMS revealed high leakage current suppression compare to other samples.Findings indicate that SNS and SMS showed enhanced resistance against UV weathering under high voltage direct current stress.

Physical,Thermal and Partial Discharge Evaluation of Nano Alumina Filled Silicone Rubber in an Inclined Plane Test

Silicone rubber(SiR)composite material is a modern-day insulator for high voltage outdoor applications.The imperfection attributed to SiR is its weak resistance to tracking and erosion when exposed to an outdoor polluted environment which reduces its operational lifetime.This paper investigates the performance of SiR with the addition of 0,1,2.5,5,10 and 20%by weight contents of nano alumina(Al_(2)O_(3)).Inclined plane tests are performed according to IEC 60587 using the step up tracking voltage method with an initial voltage of 3.0 kV and the contaminant solution flow rate is maintained at 0.3 ml/min using a peristaltic pump.The applied voltage level is increased at a rate of 0.25 kV/h.Results suggest that physical tracking,erosion,RMS leakage current and surface partial discharge(PD)performance of samples is improved with the addition of nano alumina.The tracking length,eroded mass,RMS leakage current and average PD magnitude are measured 22%,79%,30%and 52%lesser in 20 wt%relative to 0 wt%,respectively.A thermal distribution analysis is undertaken with infrared camera and it is discovered that heat is accumulated in the discharge area of the liquid flow.The maximum temperature on the insulating specimen is decreased with increasing nanofiller contents.The above promising findings can be due to better thermal stability with low chain mobility at the interaction zone of SiR and alumina.Moreover,less liquid evaporation due to better thermal conduction and improved physical bonding between SiR and nano alumina are possible reasons behind the excellent performance of nanocomposites.