User Manual

Document 2.4.128, Revision 2
August, 2012
24
Network Transformer Instruction Manual
Other Accessory Devices
Other accessories devices, such as a gauges and
valves typically require no maintenance except for
replacement in the event of malfunction or damage.
Sampling and Testing the Fluid
Before sampling the insulating uid, de-energize
the transformer and make sure all bushings and
terminals are effectively grounded. Samples should
be drawn from the bottom of the tank. Refer to
ASTM D923 Standard Practices for Sampling
Electrical Insulating Liquids for recommended
sampling procedures. Also refer to any sampling
recommendations supplied by the uid test
equipment manufacturer.
It is recommended that a uid sample be drawn
annually and tested for dielectric strength. Dielectric
strength should measure at least 26 kV.
Filtering the Fluid
Insulating uids such as mineral oil, R-Temp or
seed-based uids can be ltered using a lter
press system. A lter press can remove particle
contaminants as well as small amounts of moisture.
Follow the operating instructions provided by the
lter press system manufacturer.
Continue to lter the uid until the dielectric test
result is 26kV or better. When ltering any particular
type of insulating uid, make sure the lter press
system is not contaminated with any other type
of uid. Contamination of the uid may alter its
chemical or physical characteristics and could
reduce its re point.
Removing or Lowering the Fluid
Should it be necessary to remove or lower the
insulating uid, the following procedure should be
used.
1. De-energize the transformer and make
sure the tank, bushings, and terminals are
effectively grounded.
2. If cover removal is required, remove cover
as outlined in the “Opening the Transformer
Tank” section.
3. Use a clean, dry temporary storage container
to contain the uid.
4. Use clean pumps and hoses that have not
been contaminated by different types of
uids. Hoses must be designed for handling
the particular uid in the transformer (As an
example, rubber hoses should not be used
with mineral oil.).
5. Connect the pump intake line to the drain
valve at the bottom of the transformer tank.
6. Place the pump discharge line nozzle at the
bottom of storage container.
7. Pump slowly and do not allow the uid to
splash into the container, as this will introduce
air and moisture into the uid.
8. Do not lower the insulating uid below top
of core/coil clamp pan unless absolutely
necessary. Exposing coils may allow moisture
to contaminate coil insulation.
Filling with Fluid
When relling the transformer with insulating uid, ll
with the same type of uid. Do not mix different types
of uids. Care should be taken to avoid introduction
of air bubbles during the lling process. After relling
is complete, allow 24 hours for dissipation of air
bubbles before energizing the transformer. Trapped
air bubbles can reduce the insulating value of the
uid and cause an internal ash-over.
1. Every storage container or tote of transformer
uid should be visually inspected and tested for
WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW COULD RESULT IN DEATH OR SERIOUS
PERSONAL INJURY AND MAY
ALSO RESULT IN
DAMAGE TO THE EQUIPMENT.
• Release internal pressure before opening the
tank. Personnel should wear eye and skin
protective equipment when using the pressure
relief valve to relieve tank presure. Hot uid
may be expelled.
• Never allow anyone to enter the transformer
tank until an analysis of the air inside the tank
indicates at least 19.5% oxygen.
• Whenever someone is inside the tank, a
person should be stationed outside the tank
to ensure the safety of the person inside the
tank.