Restoring insulating liquid level
If it is necessary to drain and refill the transformer, special
care should be taken to avoid the entrapment of gas
bubbles in the system. Sufficient time should be allowed
between refilling and energization of the transformer to be
sure that any gas bubbles created during the process have
been dissipated.
1. Pump from bottom of temporary storage tank. Do not
permit intake line to draw in air, since air bubbles will
lower dielectric integrity of insulating system.
2. To prevent aeration at hose output, locate hose output
below liquid surface
3. Pump slowly. If tank cover is not attached to tank, fill
transformer to fill line marked on inside of transformer
faceplate. If the tank cover is attached to tank, liquid
level gauge may be read directly. On transformers that
are not gauge-equipped, liquid level should be filled to
bottom edge of liquid level plug hole (see Figure 3).
Applicable standards
1. ASTM D92, “Standard Test Method for Flash and Fire
Points by Cleveland Open Cup.”
2. ASTM D877, “Standard Test Method for Dielectric
Breakdown Voltage of Insulating Liquids Using Disk
Electrodes.”
3. ASTM D923, “Standard Practices for Sampling
Electrical Insulating Liquids.”
4. IEEE Std C57.106™-2002 standard, “Guide For
Acceptance and Maintenance of Insulating Oil in
Equipment.”
5. IEEE Std C57.121™-1998 standard, “Guide for
Acceptance and Maintenance of Less Flammable
Hydrocarbon Fluids in Transformers.”
Spare parts and service
We suggest that one spare set of gaskets for manhole/
handhole and any gasket-type bushings be kept on hand.
Other renewal parts may be ordered through your Eaton
representative. When ordering parts, describe to your Eaton
representative the maintenance being performed or the
problem experienced. Also, tell the Eaton representative the
complete transformer catalog number and serial number
listed on the transformer nameplate.
CAUTION
It may be necessary to add extra liquid to the storage
container from a reserve supply to replace the small
quantity lost in the pump and lines and to prevent
aeration of replacement liquid.
25Three-phase pad-mounted compartmental type installation and maintenance instructions MN202001EN August 2015
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