Patent ID: 7184895

Claim:
A method of monitoring the proportion X of a component in a gaseous mixture, said gaseous mixture having two components, a first component which is SF 6 and a second component selected from the group consisting of N 2 and CF 4 , and being contained in an electrical switchgear enclosure, said method comprising the steps of: a) measuring the pressure P, the temperature T, and the density ρ of the gas mixture contained in the electrical switchgear enclosure by means of sensors mounted on said enclosure, b) determining said proportion X by processing the measured values of pressure P, temperature T and density ρ in a data-processing unit which delivers as output the proportion X determined by solving the following equations: P (SF 6 ) =A 1.ρ(SF 6 ) +A 2. (ρ(SF 6 )) 2 +A 3.(ρ(SF 6 )) 3 and P (N 2 )= A 4.ρ(N 2 ), P=X.P (N 2 )+(1− X ). P (SF 6 ), ρ=ρ(N 2 )+ρ(SF 6 ), or P (CF 4 )= A 4. ρ(CF 4 ), P=X.P (CF 4 )+(1− X ). P (SF 6 ), ρ=ρ(CF 4 )+ρ(SF 6 ) where A 1 , A 2 , A 3 and A 4 are functions of T, P(SF 6 ) and P(N 2 or CF 4 )are the partial pressures of SF 6 and (N 2 or CF 4 ), ρ(N 2 ), ρ(CF 4 ) and ρ(SF 6 ) are the densities of N 2 , CF 4 and SF 6 , and wherein step a) is carried out without tapping said gas mixture.