The on-line
monitoring data are transmitted to the MIS through the
local enterprise network, real-timely. The data are
processed by the system first, and then other
information is integrated to make the diagnosis
judgment for power apparatus as accurate as possible.
Some utilities have gotten encouraging economical and
social profits due to the introduction of on-line
monitoring techniques. Following is an example of the
successful application of the on-line monitoring of
dissolved gas in oil. In Henan province once a phase-to-phase short circuit occurred as an overhead
transmission line swung in furious wind and snowstorm.
Auto-reclose was successful. Nevertheless, as the result
of the large current shock, the reading of the on-line
monitor for dissolved gas in oil obviously increased
after 1.5 hours of the incident, which was installed on a
main transformer rated 220kV. About 10 hours later, the
monitor issued an alarm. See Fig. 1 for the trend
evolution of gases dissolved in oil. An oil sample was
taken from the transformer the next day after the
incident. Results of dissolved gases in oil analysis
(DGA) made a confirmation as acetylene was found.
After the core was lifted out of the tank, break and
serious thaw of windings conductor was discovered.
Apparently, on-line monitoring showed its advantages
in revealing faults very timely and appropriate steps
could be taken as countermeasures.