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High Voltage Distribution Line,
Substation Infrared Thermographic Surveys
We have found that temperatures alone
cannot be used to determine if equipment is likely to fail. The accurate
evaluation of a distribution line or substation, depends mostly on the
knowledge of the person performing the inspection. This person must have
the knowledge of how the equipment operates, how it is constructed, and
what its function is in the operation of the substation.
SEE
EXAMPLE IMAGERY
Transformers
There are at least four different types of transformers in a substation,
which operate at different temperatures, depending on their functions
and load requirements.
- Current transformers are
solid and are designed to reduce currents by a percentage.
- Potential transformers may be
solid or oil-filled. They reduce voltage and are used to measure usage
of power. Higher temperature readings on a current transformers are
normal as compared to potential transformers. Even a person that has
worked with this type of equipment for years would not know this
unless he had spent many hours infrared surveying, taking readings and
knowing the equipment.
- Service transformers feed
equipment in the station such as lights, chargers, fans, etc.
Temperatures on these types of transformers depend on the equipment
they service and whether it is operating at the time of the infrared
survey.
- Power transformers are the
reason that the substation exists. Load percentages, fluid levels, and
the characteristics of oil circulation in power transformers all have
an effect on their temperatures. The infrared thermographer must know
what to look for and how to report findings. An increase of three
degrees C in one area of the transformer may be more important than a
thirty-degree increase in another.
Regulators
These devices switch from one contact point to another several times in
a day. This is the most likely piece of equipment to explode in a
substation when personnel are in the station, switching loads. Because
the contact point is inside of the tank of the regulator, it is very
important to carefully inspect this piece of equipment and record the
readings. The heat could be coming from several inches inside the tank
and since it is surrounded by gallons of oil, a slight rise in
temperature could be a serious problem. An accurate record must been
kept of the findings during maintenance of regulators, especially ones
that have been found to have high temperatures. Some manufacturers of
regulators have placed copper and aluminum wire in the same connector.
These regulators have a high rate of failure and have caused millions of
dollars in damage. When sub-stations are inspected, this equipment
should be compared to the model of equipment known to have this condition
and reported.
Switches
Switching devices allow the operator to control the functions of the
substation. They protect some of the components, i.e., the ACI is
present to protect the power transformer. Bypass and transfer switches
are mechanically operated types of switches that need adjustment for
several reasons. The temperature pattern and measurements on these
switches will indicate what kind of adjustments are needed and when.
Many times simply operating the switch will remove the problem by
realigning itself and or cleaning surface corrosion. This type of
maintenance is very effective on hook stick switches.
Distribution Lines
Because they are smaller, lower to the ground, and often run through
populated areas, high voltage electrical distribution lines are much
more difficult to see against all the thermal clutter on the ground such
as trees, street lights, people, animals, etc., than transmission lines.
Detecting electrical faults on high voltage electrical distribution
lines can be accomplished rapidly from a moving scanning vehicle. ElectriSCAN™ thermographers can help your utility by scanning the lines
and substations quickly from one of our fully-equipped scanning
vehicles. Therefore, they are best scanned from ground-based vehicles.
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