Document 2.4.126, Revision 4
October 2017
14
Three-Phase Padmounted Distribution Transformers
Post-Energization Inspection and Tests
After the transformer is energized, the following
tests and inspections should be performed.
1.
Verifying Correct Voltage
—Before supplying
voltage from the transformer to the load,
verify that the secondary voltage is correct.
Using a suitable AC voltmeter, measure the
voltage of the secondary windings and make
sure they agree with the secondary voltages
listed on the transformer nameplate.
2.
Checking for Leaks
—Check the tank to make
sure there are no fluid leaks.
3.
Observing Operation
—After the transformer
is initially energized, visually inspect it
occasionally for a few hours, to make sure
that no abnormal conditions are observed.
4.
Checking Gauges
—Observe the fluid level
and fluid temperature gauges to confirm the
proper fluid level and temperature.
5.
Audible Sound
— It is normal for transformers
to emit an audible humming sound, which
is primarily caused by alternating magnetic
flux in the transformer core. Amplitude and
harmonic content of the sound is influenced
by transformer size, the energizing voltage
level and sinusoidal purity, load conditions
and acoustic conditions at the installation
site. Refer to NEMA Standards Publication
TR-1, Transformers, Regulators and
Reactors, and IEEE Standard C57.12.90,
IEEE Standard Test Code for Liquid-
Immersed Distribution, Power, and
Regulating Transformers, for more
information about design sound levels and
factory sound testing. Unusual sounds
should be investigated, as this might
indicate a potential problem.
6.
Locking the Terminal Compartment
—Before
leaving the installation site, make sure the
terminal compartment is secure using the
following procedure.
− Lower the flip-top cover (if supplied)
and engage the center-mounted cover
security bolt
− Close the primary compartment door
and engage each security bolt.
− Close the secondary compartment
door and turn the handle to the closed
position. Engage the secondary
compartment door security bolt.
− Install a suitable heavy-duty padlock.
DANGER
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW WILL RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND DAMAGE TO THE
EQUIPMENT.
• Energize the transformer from a remote
location.
• Do not energize the transformer using
single-phase switches or fuses. Use only
gang-operated three-phase switches to
energize a three-phase transformer.
• Do not operate the transformer with any
of the primary phases open.
• Only qualified personnel with appropriate
equipment should measure transformer
voltages.
• Be aware of dangerous voltages within
the terminal compartment and avoid
personal contact with live terminals.
• Wear personal protective equipment to
prevent injury from potential arc-flash or
contact with dangerous voltages.
• Make sure the transformer is properly
grounded at all times.
• Insulated dead-end caps or plugs must
be installed on all unused dead-front
high-voltage bushings. Dust caps must
not be used in place of insulated dead-
end caps or plugs.
• Current transformer (CT) leads must
be connected to the metering load or
shorted together and grounded to prevent
dangerous voltages at the CT terminals.
