The authors aim to explore the effectiveness of two-component polyurea materials applied to transmission line towers(on the ground potential side)in improving the insulation performance of the conductor-tower gap.The ...The authors aim to explore the effectiveness of two-component polyurea materials applied to transmission line towers(on the ground potential side)in improving the insulation performance of the conductor-tower gap.The physicochemical and electrical properties of the polyurea materials were first analysed and a conductor-tower gap testing platform was constructed to investigate the effects of the length and thickness of the polyurea layer on the ground potential side under a 50-Hz AC voltage on the breakdown characteristics.Experimental studies revealed that the characteristic breakdown voltages of polyurea layers of different lengths(40,100,200,and 400 cm)are approximate.Compared with the air-insulated gap before the application of polyurea,thinner polyurea layers(1 and 2 mm)showed no significant improvement in the breakdown voltage,whereas thicker layers(3,4,and 5 mm)significantly improved it.In particular,with a polyurea layer thickness of 4 mm and gap distance of 20 cm,the characteristic breakdown voltage increased from 138.43 to 155.71 kV.In addition,the withstand voltage distance decreased from 4 to 3 cm without any breakdown,even when the high-voltage conductor directly contacted the polyurea layer and the layer was not penetrated.The authors provide theoretical support and experimental data for improving the conductor-tower gap insulation performance by applying a polyurea layer on the ground potential side.展开更多
In this study, several kinds of flexible protective materials sprayed with polyurea elastomers （hereinafter referred to as polyurea elastomer protective material） were adopted to meet the abrasion resistance require...In this study, several kinds of flexible protective materials sprayed with polyurea elastomers （hereinafter referred to as polyurea elastomer protective material） were adopted to meet the abrasion resistance requirement of hydraulic structures, and their abrasion resistances against the water flow with suspended load or bed load were studied systematically through tests. Natural basalt stones were adopted as the abrasive for simulation of the abrasion effect of the water flow with bed load, and test results indicate that the basalt stone is suitable for use in the abrasion resistance test of the flexible protective material. The wear process of the polyurea elastomer protective material is stable, and the wear loss is linear with the time of abrasion. If the wear thickness is regarded as the abrasion resistance evaluation factor, the abrasion resistance of the 351 pure polyurea is about twice those of pure polyurea with a high level of hardness and aliphatic polyurea, and over five times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with suspended load. It is also about 50 times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with bed load. Overall, the abrasion resistance of pure polyurea presented a decreasing trend with increasing hardness. Pure polyurea with a Shore hardness of D30 has the best abrasion resistance, which is 60 to 70 times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with bed load, and has been recommended, among the five kinds of pure polyurea materials with different hardness, in anti-abrasion protection of hydraulic structures.展开更多
基金National Natural Science Foundation of China,Grant/Award Number:52207023。
文摘The authors aim to explore the effectiveness of two-component polyurea materials applied to transmission line towers(on the ground potential side)in improving the insulation performance of the conductor-tower gap.The physicochemical and electrical properties of the polyurea materials were first analysed and a conductor-tower gap testing platform was constructed to investigate the effects of the length and thickness of the polyurea layer on the ground potential side under a 50-Hz AC voltage on the breakdown characteristics.Experimental studies revealed that the characteristic breakdown voltages of polyurea layers of different lengths(40,100,200,and 400 cm)are approximate.Compared with the air-insulated gap before the application of polyurea,thinner polyurea layers(1 and 2 mm)showed no significant improvement in the breakdown voltage,whereas thicker layers(3,4,and 5 mm)significantly improved it.In particular,with a polyurea layer thickness of 4 mm and gap distance of 20 cm,the characteristic breakdown voltage increased from 138.43 to 155.71 kV.In addition,the withstand voltage distance decreased from 4 to 3 cm without any breakdown,even when the high-voltage conductor directly contacted the polyurea layer and the layer was not penetrated.The authors provide theoretical support and experimental data for improving the conductor-tower gap insulation performance by applying a polyurea layer on the ground potential side.
基金supported by the National Natural Science Foundation of China(Grants No.51109143 and 51209144)the Natural Science Foundation of Jiangsu Province(Grant No.BK2011109)the Foundation of Nanjing Hydraulic Research Institute(Grant No.Y113004)
文摘In this study, several kinds of flexible protective materials sprayed with polyurea elastomers （hereinafter referred to as polyurea elastomer protective material） were adopted to meet the abrasion resistance requirement of hydraulic structures, and their abrasion resistances against the water flow with suspended load or bed load were studied systematically through tests. Natural basalt stones were adopted as the abrasive for simulation of the abrasion effect of the water flow with bed load, and test results indicate that the basalt stone is suitable for use in the abrasion resistance test of the flexible protective material. The wear process of the polyurea elastomer protective material is stable, and the wear loss is linear with the time of abrasion. If the wear thickness is regarded as the abrasion resistance evaluation factor, the abrasion resistance of the 351 pure polyurea is about twice those of pure polyurea with a high level of hardness and aliphatic polyurea, and over five times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with suspended load. It is also about 50 times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with bed load. Overall, the abrasion resistance of pure polyurea presented a decreasing trend with increasing hardness. Pure polyurea with a Shore hardness of D30 has the best abrasion resistance, which is 60 to 70 times that of high-performance abrasion-resistant concrete under the abrasion of the water flow with bed load, and has been recommended, among the five kinds of pure polyurea materials with different hardness, in anti-abrasion protection of hydraulic structures.
