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Cracking of conductive brass accessories in substations causes overheating or an open circuit, seriously affecting the safe and stable operation of the power grid system. A deep understanding of failure mechanisms could provide more safety, as well as lower down costs and save time for the power grid system, which have been seldomly involved in the literature. This paper presents a cracking analysis of a brass clamp in service for seven years that is mounted on the main transformer. The fracture morphology, chemical composition, and metallographic structure of the brass clamp were systematically analyzed, and the stress conditions were obtained by finite element simulation. The clamp exhibits transgranular brittle fracture with high oxygen content in the fracture, containing a crack propagation along the Pb particle connecting pathways, and the stress concentration was confirmed at the crack position. It is concluded that the failure was a result of the stress corrosion cracking and excessive content of Pb. Suggestions were proposed to avoid malfunction of the main transformer caused by the clamp crack. [ABSTRACT FROM AUTHOR]

The cracking and reasons for aging of silicone rubber current transformer insulation sheath from a 500 kV substation were investigated. Chemical characteristics including attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, mechanical properties, and thermo gravimetric analysis (TGA) have been performed on the external surface and internal parts of the silicone rubber CT insulation sheath. The FTIR results indicated that the external surface of the silicone rubber CT insulation sheath suffered from more serious aging than the inner, fracture of the side chain (Si-C bond) was much more than the backbone (Si-O bond). Mechanical test results revealed that the tensile strengths of the external surface parts of the silicone rubber CT insulation sheath were lower than those of the internal parts. TG analysis data indicated thatTonsetdropped nearly 50°C for the external surface of the silicone rubber CT insulation sheath. All the chemical characteristics have showed that the external surface material of the silicone rubber CT insulation sheath had been serious aging. Our work suggested a facile and effective method for evaluating the aging state of the silicone rubber insulation sheath in the electric power field from the perspective of chemical. [ABSTRACT FROM AUTHOR]

[Display omitted] • All-iron ions mediated biomass pretreatment coupling with direct biomass fuel cell. • Ferric ions as electron carriers under acidic condition. • Ferricyanide ions as electron carriers under alkaline condition. • Ferric nitrate activated by HNO 3 as cathode electron carriers. • Fermentable sugars production with co-generation of electricity from bagasse. A coupled process of biomass pretreatment for increasing cellulose digestibility and direct conversion of biomass to electricity has been developed with ferric or ferricyanide ions as the anode electron carriers, and Fe(NO 3) 3 activated by HNO 3 as the cathode electron carriers. Pretreated substrates are subjected to enzymatic hydrolysis for release of fermentable sugars, while the pretreatment liquor is employed as anolyte for electricity generation in a liquid flow fuel cell (LFFC). Pretreatment of sugarcane bagasse with 2 M FeCl 3 in anode reactor removes ∼ 100% hemicelluloses and obtains 76% enzymatic glucan conversion (EGC), while pretreatment with 0.1 M K 3 [Fe(CN) 6 ] in 0.5 M KOH achieves 78% lignin removal, 95.8% EGC and 85.1% xylan conversion. From 1000 g bagasse, 171.3 g fermentable sugars is produced with co-generation of 101.4 W·h electricity based on FeCl 3 pretreatment, while 519 g fermentable sugars and 28.9 W·h electricity are obtained based on K 3 [Fe(CN) 6 ] pretreatment. [ABSTRACT FROM AUTHOR]

In order to effectively reduce and retard corrosion of the power transmission and transformation equipment in Chengdu power grid and to improve power supply reliability, Q235 carbon steel material which is the most widely used metal material in power grid was selected as the targeted research object in this article. Exposure experiments were performed in urban atmospheric environment of Chengdu city in the southwest region of China. The corrosion behavior of Q235 carbon steel material was investigated at different seasons. The macro- and micromorphologies after corrosion were observed using a digital camera and scanning electron microscopy (SEM), respectively. Element distribution of the rust layer and the corrosion products was characterized by energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR); the corrosion mechanism was also briefly analyzed. [ABSTRACT FROM AUTHOR]