Gas-in-oil monitoring apparatus and method

Claim 1

An on-line gas-in-oil monitoring apparatus for oil-filled electrical apparatus which indicates substantially simultaneously the amount of at least two predetermined gases in the oil comprising: means for separating said predetermined gases from said oil; a sensor housing; means for periodically introducing a sample of said predetermined gases separated from said oil into said housing; a first gas sensing means disposed in said sensor housing which is predominantly sensitive to a first of said predetermined gases; a second gas sensing means disposed in said sensor housing which is predominantly sensitive to a second of predetermined gases; vent means for venting said sensor housing to the atmosphere for purging said predetermined gases from the sensor housing and to admit oxygen to said sensor housing to resensitize said sensing means to said predetermined gases; control means which are responsive to a change in conductivity of said first and second sensing means in response to the presence of said first and second predetermined gases respectively, and generate an indication of the levels of the first and second predetermined gases; said first sensing means is predominantly sensitive to carbon monoxide; said second sensing means is predominantly sensitive to hydrogen; said sensing means are sintered metal oxide semiconductors with adsorbed oxygen; heating means which provide heat or voltage to said sensing means; said heating means provides a first heating voltage to said first sensing means to heat said second sensing means to a temperature which renders said first sensing means sensitive to the first of said predetermined gases; and a second heating voltage to said second sensing means to heat said second sensing means to a temperature which renders said second sensing means sensitive to the second of said predetermined gases.

Claim 4

A method of providing on-line measurement of a sample of at least two predetermined gases in oil substantially simultaneously comprising: separating said predetermined gases from said oil; providing a sensor housing with at least two sensing means comprised of sintered metal oxide semi-conductors with adsorbed oxygen disposed therein; periodically introducing a sample of said predetermined gases into said sensor housing whereby said sensing means are exposed to said predetermined gases; measuring the conductivity of said sensing means; and regenerating one of said sensing means predominantly sensitive to the presence of hydrogen by heating said sensing means in the presence of oxygen for a recovery period; regenerating the other of said sensing means predominantly sensitive to the presence of carbon monoxide by heating said sensing means at a higher temperature for a first recovery period; heating said sensing means at a lower temperature for a second recovery period; and heating said sensing means at a higher temperature for a third recovery period.

Claim 5

A method of providing on-line measurement of a sample of at least two predetermined gases in oil substantially simultaneously comprising: separating said predetermined gases from said oil; providing a sensor housing with at least two sensing means comprised of sintered metal oxide semi-conductors with adsorbed oxygen disposed therein; periodically introducing a sample of said predetermined gases into said sensor housing whereby said sensing means are exposed to said predetermined gases; measuring the conductivity of said sensing means; and regenerating one of said sensing means predominantly sensitive to the presence of hydrogen by heating said sensing means in the presence of oxygen for a recovery period; regenerating the other of said sensing means predominantly sensitive to the presence of carbon monoxide by heating said sensing means at a higher temperature for a first recovery period; heating said sensing means at a lower temperature for a second recovery period; and heating said sensing means at a higher temperature for a third recovery period.