Gas chromatograph techniques for on-line testing of transformer faults

A method for detecting the gas concentration levels of fault gases evolved in a supply of electrical insulating oil contained in an electrical transformer in which the transformer housing contains a fault gas-containing ambient gas blanket in an equilibrium state in a headspace above the insulating oil supply, the method comprising:

• transferring a sample of the ambient gas contained in the headspace to a gas chromatograph instrument;
• operating the instrument to measure the concentration levels of the fault gases contained in the gas sample;
• informing a programmed computer device of the measured fault gas concentration levels;
• determining the temperature and pressure of the ambient gas contained in the headspace of the transformer;
• informing the programmed computer device of a fault gas temperature and pressure-related partition function between the headspace gas and the oil-dissolved fault gases based on gas solubility and gas/liquid equilibrium constraints according to Henry's Law;
• providing the fault gas temperature and pressure information as inputs to the partition function means of the programmed computer device so that gas temperature and pressure corrections can be made according to the ideal gas law for the ambient gas within the headspace;
• operating the programmed computer device for converting a measured fault gas concentration level in the gas sample taken from the transformer headspace to a related gas concentration level of the same fault gas contained within the transformer oil supply and calculating the concentration levels of the fault gases contained in the transformer oil supply;
• and
• providing said calculated fault gas concentration levels as an output representing a specific fault condition of the transformer.

A system for monitoring dissolved gases in the electrical insulating oil supply of an electrical transformer in which a blanket of ambient gas containing a plurality of fault gases is present in an equilibrium state in the headspace above the insulating oil supply contained in the transformer, the system comprising:

• an instrument for measuring the concentration levels of particular fault gases present in the gas sample;
• a programmed computing device informed of a gas temperature and pressure dependent gas partition function between the headspace gas and the oil-dissolved fault gases based on gas solubility and gas/liquid equilibrium constraints according to Henry's Law;
• means for determining the temperature and pressure of the ambient gas within the headspace and providing said gas temperature and pressure information as inputs to the partition function so that gas temperature and pressure corrections can be made by the programmed computing device according to the ideal gas law for said ambient gas;
• said computing device programmed for calculating the related gas concentration levels of said fault gases which are present in the transformer oil supply based on said partition function;
• and
• means for producing a computerized interpretation of the fault gas concentrations in the transformer oil supply to provide an indication of a specific transformer fault.

A system for detecting the gas concentration levels of fault gases evolved in a supply of electrical insulating oil contained in an electrical transformer in which the transformer housing contains an ambient fault gas-containing gas blanket in an equilibrium state in a headspace above the insulating oil supply, the system comprising:

• a gas chromatograph instrument for measuring the concentration levels of fault gases contained in the gas sample;
• means for informing a programmed computer device of the measured fault gas concentration levels;
• means for informing the computer device of a fault gas temperature and pressure-related partition function between the headspace gas and the gas-dissolved fault gases based on gas solubility and gas/liquid equilibrium constraints according to Henry's Law to provide means for converting a measured fault gas concentration level in the ambient gas sample taken from the transformer headspace to a related gas concentration level of the same fault gas contained within the transformer oil supply;
• means for determining the temperature and pressure of the ambient gas within the headspace and providing such fault gas temperature and pressure information as inputs to the partition function means of the computer device so that gas temperature and pressure corrections can be made according to the ideal gas law for said ambient gas;
• and
• means for operating the computer device for calculating the concentration levels of the fault gases contained in the transformer oil supply, said calculated fault gas concentration levels comprising an output having a computerized interpretation representing a specific fault condition of the transformer.

A method for monitoring dissolved gases in the electrical insulating oil supply of an electrical transformer in which a blanket of gas containing a fault gas is present in the headspace above the insulating oil supply contained in the transformer, the method comprising:

• producing a sample of the gas contained in the headspace and transferring the gas sample to an instrument for measuring the amount of a particular fault gas present in the gas sample;
• operating said instrument for measuring the gas concentration level of the fault gas contained in the gas sample;
• applying a fault gas measurement value determined by said instrument as an input to a programmed computing device informed of a gas temperature and pressure dependent gas partition function between the headspace gas and the oil-dissolved gas based on gas solubility and gas/liquid equilibrium constraints according to Henry's Law;
• measuring the temperature and pressure of the gas within the headspace of the transformer, informing the computer of the measured gas temperature and pressure information, and using the temperature and pressure information as an input to the gas partition function to calculate the fault gas concentration level in the transformer oil supply;
• calculating the related gas concentration level of said fault gas which is present in the transformer oil supply by operating the computing device in relation to said partition function to convert said fault gas concentration level in the headspace to a related measurement of the concentration level of said fault gas in the transformer oil supply;
• thereafter producing a reading of the fault gas concentration in the transformer oil supply to provide an indication of a specific transformer fault;
• including transmitting gas samples from the headspace of a plurality of transformers in sequence to a common gas chromatograph instrument for producing said calculations;
• and
• calculating the fault gas concentration level in the oil supplies of the plurality of transformers via the common instrument, and transmitting the calculated fault gas concentration levels in said oil supplies to a common display.

A system for monitoring dissolved gases in the electrical insulating oil supply of an electrical transformer in which a blanket of gas containing a fault gas is present in the headspace above the insulating oil supply contained in the transformer, the system comprising:

• an instrument for measuring the amount of a particular fault gas present in a gas sample taken from the headspace;
• a programmed computing device informed of a gas temperature and pressure dependent gas partition function between the headspace gas and the oil-dissolved gas based on gas solubility and gas/liquid equilibrium constraints according to Henry's Law, said computing device programmed for calculating the related gas concentration level of said fault gas which is present in the transformer oil supply based on said partition function to convert an output of said instrument to a measurement of the concentration level of said fault gas in the transformer oil supply;
• and
• means for producing, interpreting and electronically analyzing a reading of the fault gas concentration in the transformer oil supply to provide an indication of a specific transformer fault,
• including means for calculating the fault gas concentration level in the oil supplies of the plurality of transformers via the common instrument, and transmitting the calculated fault gas concentration levels in said oil supplies to a common display.