Each non-faulty tap changing operation involving oil-immersed contacts, depending on the LTC type and
operating conditions, generates characteristic amounts of acetylene, hydrogen, and other combustible gases,
which dissolve in the oil and persist for some time, depending on the LTC breathing configuration. Higher
load and/or increased tap changing operations can result in higher dissolved combustible gas
concentrations. Similarly, the fact that in non-faulty LTCs the relative rates of production of the various
combustible gases tend to be fairly stable means that the ratios of those gases tend to fall within a certain
range of values, depending on the LTC type.