Abstract
SF6 is widely used in modern transmission and distribution networks because of its outstanding dual qualities: arc quenching and dielectric insulation. As a gas medium, SF6 is chemically inert, non-toxic, and non-flammable, which makes possible the construction of compact SF6 switchgear. One major known disadvantage of the gas is that it has a global warming potential which is 23,900 times higher than CO2. This has led to research into alternative gases with a much lower environmental impact, and one of the emerging candidates is CF3I. The high boiling temperature of CF3I means that it has to be used as part of a mixture inside gas-insulated equipment. To carry out the investigation on CF3I, a scaled-down coaxial system that replicates the maximum electric field of a 400 kV GIL system was designed and fabricated. The insulation performances of CF3I/CO2 and CF3I/N2 gas mixtures were then examined by measuring the 50% breakdown voltage, U50, using a standard lightning impulse waveform (1.2/50) under absolute pressures of 1 to 4 bar. The experimental results show that CF3I gas mixtures have promising potential as an insulation medium for application in gasinsulated lines.
Highlights
THERE is an urgent need worldwide to reduce greenhouse emissions in order to reach the ambitious targets set by governments in response to the Kyoto Protocol on climate change
One major known disadvantage of the gas is that it has a global warming potential which is 23,900 times higher than CO2
This paper describes the investigation carried out on the scaled-down coaxial gas-insulated lines (GIL) system for several CF3I gas mixtures
Summary
THERE is an urgent need worldwide to reduce greenhouse emissions in order to reach the ambitious targets set by governments in response to the Kyoto Protocol on climate change. Another factor that needs to be taken into consideration is the optimisation of the quantity log(Rb/Ra) [18], for which a value of unity is considered the optimal ratio of gap distance and field uniformity in a coaxial geometry. By adopting this approach, a maximum electric field strength similar to that of a 400 kV GIL system was achieved with practical values of a = 1 cm, b = 3 cm at an applied voltage of 90 kV.
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