Version
V1.0
Transformer oil conservator
Applications of thermal imager PDM
PDM - Transformer oil conservator -20080425
Transformer oil conservator regulates the oil reserve in transformer cooling
circulation system to ensure normal transformer operating temperature. The oil
level in the transformer oil conservator is detected by an infrared thermal
imager, allowing the cooling oil to be constantly maintained in a proper
quantity, avoiding damage to the transformer caused by high temperature.
What is a transformer oil conservator?
A transformer generates a great deal of heat energy during operation and this can cause it to become very
hot. In order to cool the transformer, transformer oil is employed to circulate in it. However, the temperature
of the transformer oil changes with the variation of load and ambient temperatures. It generally changes in
the range of 10 to 120. Oil is a kind of liquid that can hardly be compressed and the transformer oil, like
many other substances, expands with heat and contracts with cold.
In order to solve the expansion problem of the transformer oil, refill the transformers in a timely manner and
solve the oil level problem of the filling bushing of the transformers, an oil conservator is fitted on the top of
each transformer.
When the transformer oil expands or contracts with its temperature, the oil conservator stores or refills oil
respectively, allowing the oil tank is full of oil. Additionally, the oil reduces the contact area of the transformer
with air, slowing down the speed of oil deterioration. So the oil conservator plays an extremely important
protection role to normal operation of the transformers.
Why detect the oil level in the transformer oil conservator ?
An oil level indicator is fitted on the side of the oil conservator to monitor the oil level. But it is prone to be
blocked by sedimentation of the transformer oil. This can cause false oil level and confuse the electrical
maintenance personnel in their estimation of oil quantity.
If a transformer operates with insufficient oil for a long period, it will, due to temperature rise, overheat or
even set on fire. The worst case scenario is an explosion.
An infrared thermal imager can be employed to detect the oil level of the transformer oil conservator as well
as the oil level indicator, ensuring normal cooling circulation in the transformer.
How does an infrared thermal imager detect the oil level in a transformer oil conservator ?
Generally, the oil level in a transformer oil conservator should be maintained within to 2/3 of its entire
height. Insufficient oil cannot ensure refilling to the transformer and excessive oil may cause expansion
breaking of the oil conservator or pipelines due to heat expansion of the transformer oil.
Besides transformer operating temperature, load, leakage of the oil tank, etc, the oil level in the conservator
is also effected by ambient temperature. For example, the oil level is sometimes lower than the lower limit on
the indicator in the winter due to low outdoor temperature. So it must be detected strictly and refilled in a
timely manner.
Thermal imager is expected and available.
Fluke Corporation The problem point is obtained as soon as an image is made. Please refer to the following website for more
thermal imager information:
http://www .fluke. com. cn/
Version
V1.0
Typical customers:
Electric power industry: transformer operation areas of all levels of power supply bureaus and substations.
Process industry: electric power generation, petrochemical, metallurgy, cement, etc.
Level line of a transformer oil conservator
What problems may happen during imaging (is it possible that the oil level of transformer oil
conservators sometimes cannot be detected)?
If a transformer is not operating, the oil level can only be detected by the temperature difference that occurs
when the ambient temperature changes due to the thermal capacity difference of the transformer oil and the
air. However, as oil conservators have relatively small volume, this temperature can hardly be detected. So
you must confirm that corresponding transformer is operating before performing an oil level detection on a
oil conservator. Otherwise you may be unable to detect it.
How do you ensure high quality oil level detection of transformer oil conservators?
Transformer oil conservators are often installed outdoors, together with transformers (there are still some
which are installed indoor). They are affected by many environmental factors, so we suggest:
1. Avoid imaging when the oil conservators are under direct sunlight, especially in midday, because the oil
conservators can be completely heated by the sunlight and the oil level line is not clear during this period.
2. If the oil level line is not clear in the automatic mode, you can first measure a temperature range in the
automatic mode. Then manually set the level and span to set the temperature range to the minimum, while
covering the temperature range measured previously (instruments of different versions have different
minimum temperature ranges).
3. After the oil level line is imaged, compare it against the oil level indicator on the relevant transformer
whenever possible. In this way, you can find a faulty oil level indicator in time.
4. If there is more than one transformer on the field that operates in similar states, please conduct cross-
comparison of the oil level and housing temperature of these oil conservators. In this way, you can find any
troubles (e.g. blockage, insufficient oil, oil leakage, etc.) that happen during cooling circulation of the
transformer oil in time.
Thermal imager is expected and available.
Fluke Corporation The problem
point is obtained as soon as an image is made. Please refer to the following website for more
thermal imager information:
http://www .fluke. com. cn/
