ELECTRIC STRENGTH OF SOME GASES AND GAS MIXTURES

ABSTRACT Sulphurhexafluoride accounts for a significant fraction of the total cost of compressed gas insulated transmission (CGIT) lines. There is, therefore, a considerable incentive to find alternative gases which may be superior to SF 6 in practical equipment. This paper will report the results of experimental determinations of the 60 Hz electric strength in quasi-uniform fields of approximately thirty gases at 0.15 MPa. In service, the maximum strength achievable with a gas is limited, among other factors, by the maximum tolerable pressure (bursting strength of the equipment) and by low vapor pressure at low temperatures. A method of comparing the maximum usable electric strengths of various gases over specified operating temperature and pressure ranges taking into account the above limitation will be discussed using the experimental data. This paper will also report the results of experimental determinations of the 60 Hz electric strength of binary mixtures of these gases with SF 6 , in most cases over the range of zero to 100% SF 6 . This work is sponsored by the Electric Power Research Institute under Contract 847-1 with the Westinghouse Research and Development Center.