Bay-O-Net fuse replacement
When replacing fuses in Flapper™ style Bay-O-Net
fuse assembles, refer to Bay-O-Net Fuse Re-Fusing
Instructions in this manual. Follow the same procedure as
with conventional oil-filled transformers.
Operation
Eaton designs its transformers to operate at rated load with
a temperature rise equal to or less than the temperature
rise printed on the transformer’s nameplate. Operating
transformers in excess of IEEE Std C57.91™-2011 standard
will result in accelerated loss of insulation system life. The
coil insulation has been carefully made with thermally-
upgraded materials to ensure long life at rated loads. Severe
and prolonged overloads of mineral oil-filled transformers
will result in overheating and accelerated aging of the
insulation, which may lead to premature failure. PEAK™
transformers have extended life and can be operated at
higher temperatures. Refer to IEEE Std C57.154™-2012
standard for details.
Mixtures of Envirotemp™ FR3™ fluid and
conventional transformer oil
Envirotemp™ FR3™ fluid is fully miscible with conventional
transformer oil. There is no known detrimental performance
impact when Envirotemp™ FR3™ fluid is mixed with
conventional transformer oil. Conversely, except for some
reduction in flash and fire points, the same is true for
conventional transformer oil mixed with Envirotemp™
FR3™ fluid. Conventional transformer oil content of >7%
in Envirotemp™ FR3™ fluid lowers the fire point below
300°C. Measure the ASTM flash and fire points if the
presence of conventional transformer oil is suspected. If
flash or fire points fall below the minimum values required,
retrofilling may be required. To maintain its exceptional
environmental classification, mixing of Envirotemp™ FR3™
dielectric coolant with any other fluids should be avoided.
Contact your Eaton representative for additional handling
guidelines for Envirotemp™ FR3™ fluid.
Sampling insulating liquid
Before sampling the insulating liquid, verify that the tank
is grounded. De-energize the transformer from a remote
upstream source. Ground the bushings and terminals.
Refer to ASTM D923 “Standard Practices for Sampling
Electrical Insulating Liquids” for sampling techniques.
A sample of the liquid should be taken when the liquid tem-
perature is equal to or greater than the surrounding air to
avoid condensation of moisture on the liquid.
Containers used for sampling liquid should be clean and dry
large mouth glass bottles. Make sure that the liquid being
sampled is representative of the liquid in the unit. Sufficient
liquid must first be drawn off to ensure that the sample will
be from the bottom of the tank, and not the liquid stored in
the sampling pipe
Testing insulating liquid
For the dielectric strength of the insulating liquids, follow
the technique as specified by ASTM D877, “Standard Test
Method for Dielectric Breakdown Voltage of Insulating
Liquids Using Disk Electrodes”.
If the dielectric strength of the liquid drops below 26 kV, it
should be filtered until it tests at 26 kV or better.
Filtering insulating liquid
Conventional transformer oil, R-Temp, or Envirotemp™
FR3™ fluids can be filtered by means of a filter press.
The filter press is effective for removing all types of
foreign matter, including finely divided carbon and small
amounts of moisture. The purifier equipment consists of a
specifically proportioned filter press, a positive volume gear
pump, driving motor, combined drip pan and mixing tank,
necessary piping, valves, strainer, gauges and drying oven.
Follow manufacturer’s instructions for purifier equipment
operation.
Filtration should be continued until the dielectric test of the
insulating liquid is 26 kV or better.
When filtering R-Temp or Envirotemp™ FR3™ fluid, the
filtering equipment must be free of contaminants and other
liquids. The presence of other liquids may alter the physical
and electrical characteristics of R-Temp or Envirotemp™
FR3™ fluid. This could result in a reduction of fire point.
Lowering insulating liquid level
1. Verify that tank is grounded. De-energize transformer
from a remote upstream source. Ground all bushings
and terminals.
2. If cover removal is required, remove cover as outlined
in Tank Cover Removal and Installation section of
this manual.
3. Prepare a clean, dry storage container to receive liquid.
4. Use pumps and hoses that have not been
contaminated by contact with dissimilar liquids. Use a
metal or non-rubber hose. Oil dissolves the sulfur found
in rubber and will prove harmful to conductor material.
5. Attach pump intake line to drain valve on transformer
tank.
6. Place output line nozzle on bottom of storage container.
Do not permit liquid to splash into receiving container.
Splashing will introduce air and moisture into liquid.
7. Do not lower liquid below top of core clamp unless
absolutely necessary. Exposing coils may allow
moisture to contaminate coil insulation.
24 Three-phase pad-mounted compartmental type installation and maintenance instructions MN202001EN August 2015
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