Howard HI-104 Single-Phase Pad Transformer - Manual (Page 12)

Document 2.4.96, Revision 0
March, 2013
12
Single-Phase Pad-Mounted Compartmental-Type Distribution Transformers
Pre-Energization Inspection and Tests
After the transformer has been installed, but before
it is energized, the following tests and checks should
be performed at a minimum to ensure that the
transformer is ready to be energized. Do not energize
the transformer without performing these tests and
checks.
▲
! DANGER
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW WILL RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND COULD ALSO RESULT
IN DAMAGE TO THE EQUIPMENT .
Be aware of dangerous voltages within the ter-
minal compartment and avoid personal contact
with live terminals.
▲
! WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW COULD RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND COULD ALSO RESULT
IN DAMAGE TO THE EQUIPMENT.
• Only qualified personnel with appropriate
equipment should measure transformer volt-
ages.
• Wear personal protective equipment (PPE)
to prevent injury from potential arc-flash or
contact with dangerous voltages.
• Make sure the transformer is securely and
effectively grounded at all times.
• Insulated dead-end caps or plugs must be
installed on all unused dead-front high-volt-
age bushings. Dust caps must not be used in
place of insulated dead-end caps or plugs.
• Current transformer (CT) leads must be con-
nected to a metering load or shorted together
and grounded to prevent dangerous voltage
at the CT terminals.
• After successful completion of the recom-
mended tests and checks, energize the trans-
former from a remote location.
1. Ratio Test—Using a transformer turns ratio tester
(TTR), perform a ratio test to verify the primary-
to-secondary winding ratio. The measured value
should be within 0.5% of the voltage ratio in-
dicated on the transformer nameplate. If the
transformer is provided with high-voltage taps,
measure the ratio at each tap position to en-
sure that each of the ratios is correct. Follow the
instructions and safety precautions provided by
the TTR equipment manufacturer. For additional
information about ratio testing, refer to IEEE
Standard C57.12.90.
2. Insulation Resistance Test—Perform a 1,000-Volt
insulation test (Megger test) to measure the re-
sistance of the insulation between windings and
from each winding to ground. Follow the instruc-
tions and safety precautions provided by the test
equipment manufacturer. Prior to the test, bush-
ings must be thoroughly cleaned with denatured
alcohol to remove any moisture or contaminants
that could influence the test results. Measured
resistance should be at least 1.0 GΩ.
3. Tap Changer Setting—On transformers pro-
vided with taps, check the tap changer setting
to ensure it is set to the proper position for the
required voltage.
4. Multiple-Voltage Switch Setting—On transform-
ers provided with a multiple-voltage switch,
check the switch setting to make sure it is set to
the correct position.
5. Grounding—Check to ensure that the transformer
tank is securely and effectively grounded. The
transformer tank ground pad is located inside
the terminal compartment near the bottom of the
tank.
6. Bolted Connections—Check all bolted connec-
tions for tightness, referring to nominal torque
guidelines contained in Tables 1 through 4.
7. Fluid Level—Check to make sure the fluid level
is correct as indicated by the fluid level gauge or
sight plug. If the transformer does not have a flu-
id level gauge or sight plug, the fluid level can be
checked by temporarily removing the liquid-level
plug located at the 20°C mark. Prior to removing
the plug, relieve tank pressure by operating the
SECTION 4: INSPECTION AND TESTING BEFORE AND
AFTER INITIAL ENERGIZATION