The 973-SF6 is an advanced SF6 gas analyzer for the measurement of humidity, SF6 purity and SO2 concentration in SF6 gas insulated switchgears (GIS) and other high voltage equipment. With its internal gas containment and recovery system, the 973-SF6 provides a high quality and environmentally safe measurement solution within a single self-contained unit.
Pure SF6 is the standard filling within GIS, but over time gas compartments become contaminated with water vapor (H2O) through permeation and by desorption from internal materials. Whilst water vapor and SF6 do not normally react with each other, in the presence of a high-energy discharge, hydrogen and oxygen disassociated from water vapor will react with the sulfur and fluorine from SF6 to form decomposition by-products. These include sulfur dioxide (SO2) and hydrofluoric acid (HF) that are corrosive to the internal components of gas compartments.
SF6 with low water vapor content (low humidity) significantly reduces the potential for formation of these corrosive compounds, which is why accurate and repeatable measurement data is an invaluable part of any GIS preventative maintenance program.
Since 2012, all 973-SF6 instruments have been produced ready to measure SO2 concentration. The option can be added at the factory, or later with the supply of an activation key and a sensor. The So2 range can be either 100 or 500 ppmV. These are electrochemical cell based, so have the inherent weakness of any sensor in that its only as gas as its calibration and long term stability. MBW try harder than most to get this right by calibrating in SF6 rather than the normal SO2 in Nitrogen method that resolves significant errors in use.
973-SF6 is supplied with DN8 and DN20 couplings, but others are available to suit almost every type of gas compartment. The types available are detailed here.