Omicron CP TD1, Справочное руководство

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Power Transformers
65
6 Power Transformers
6.1 Introduction
Due to ever-increasing pressure to reduce costs, the power industry is forced to
keep old power facilities in operation as long as possible. In most European
countries, about one third of the transformers are over 30 years old. Even
transformers older than 50 years are still in service. A regular check of the
operating conditions becomes more and more important with the advancing age
of transformers. The Dissolved Gas Analysis is a proven and meaningful method
for finding a fault as soon as possible if increased proportions of hydrogen and
hydrocarbon gases are found in the oil. This way, important preventative
maintenance can be performed in time to avoid an unexpected total failure.
DGA analysis and interpretation of results [3.1]
On the left are gases the oil specialist looks for in the gas-in-oil-analysis. On the
right are possible origins of these gases. When these gases exceed the levels
shown in the middle columns, the analyst uses the transformer history, the type
of gases present, as well as the relative amounts, to determine any indication of
transformer problems.
Gas Normal
ppm
1)
Abnormal
ppm
Hydrogen H
2
200 500
Acetylene C
2
H
2
5 15
Methane CH
4
50 120
Ethylene C
2
H
4
80 170
Ethane C
2
H
6
35 75
Carbon
monoxide
2)
CO 200
1)
500
Carbon
dioxide
3)
CO
2
2000
2)
3500
Cellulose
Ov
er
he
a
ted
O
il
Co
ro
na
Arcing