There are no Alternatives
There are monitors available that, due to technical limitations, cannot measure O2, and their suppliers propose alternative methodologies. When looking at monitor suppliers, it’s important to consider that insulation aging and sealing failures both involve O2. Detecting O2 will directly measure these two phenomena. Any alternative method will be an indirect estimation. The total gas pressure will be able to detect large leaks but it has no advantage over the direct measurement of O2 which is the main gas of interest when there is a leak. Additionally, total gas pressure will not be sensitive enough to detect small leaks or aging consumption when compared with O2 measurements, because O2 is only a portion of the total gas pressure.
In all cases, if O2 is the key parameter, measuring O2 is the best choice.
Furthermore, insulation aging is typically assessed by measuring O2, CO, CO2 and then comparing this with oil quality data, mainly furans and acidity. It is important to note that gases such as C3Hx propane and propylene are not directly linked with insulation aging and are only occasionally used to confirm low temperature overheating (not a sign of ageing).
CIGRE TB771 states that C3 gases “do not really provide additional information”
IEEE C57.104 states that C3 gases are “not used in this guide”
And IEC60599 states that “diagnostics can be made without taking into account these hydrocarbons”.
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