Howard Industries HI-105 User manual

Document 2.4.126, Revision 4
October 2017
1
Three-Phase Padmounted Distribution Transformers
Howard Industries
Distribution Transformer Division
Instructions (HI-105)
Installation, Operation, and Maintenance
of Three-Phase Padmounted Distribution Transformers
45 kVA through 10,000 kVA

Document 2.4.126, Revision 4
October 2017
2
Three-Phase Padmounted Distribution Transformers
Read these instructions carefully and become familiar with the equipment before
proceeding with installation, operation, or maintenance activities. This equipment
contains extremely hazardous voltages. To prevent death, serious personal
injury, or equipment damage, all information in these instructions should be read
and observed. Safe use of this equipment is dependent on proper installation,
operation, and maintenance procedures.
Certain information in this manual is marked with the words DANGER, WARNING,
or CAUTION, which indicate hazards.
DANGER indicates an imminently hazardous situation which, if not avoided, will
result in death or serious personal injury, and damage to the equipment.
WARNING indicates a potentially hazardous situation which, if not avoided, may
result in death or serious personal injury, and/or damage to the equipment.
CAUTION indicates a potentially hazardous situation which, if not avoided, may
result in minor or moderate personal injury, and/or damage to the equipment.
No one should attempt to service or perform maintenance activities on the
equipment until it has been effectively de-energized, and all high-voltage and low-
voltage bushing terminals have been properly grounded. Only qualied personnel
should install, maintain, and operate this equipment. Qualied personnel are
those who are trained in the installation, maintenance, and operation of high-
voltage equipment, trained in the proper use of personal protective equipment
(such as rubber gloves, safety glasses, protective clothing, hard hats, etc.) and
trained in appropriate rst aid procedures.
The instructions contained herein are intended to be a general guide for the
installation, operation and maintenance of this equipment, when operated in
“Usual Service Conditions” as dened in IEEE Standard C57.12.00. Features
presented herein may not be present in all equipment designs. Standard and
optional features are subject to change without notice.
Although efforts have been made to ensure accuracy and completeness, these
instructions do not address every conceivable application or circumstance that
might be encountered. Howard Industries makes no representation or warranty
with respect to, and assumes no responsibility for the completeness, accuracy,
sufciency, or usefulness of, these instructions.
Questions regarding installation, operation, and maintenance of the equipment,
particularly when encountering unusual or special circumstances that may not
be sufciently covered by these instructions, should be directed to the Howard
Industries Transformer Division.
READ THIS IMPORTANT SAFETY INFORMATION

Document 2.4.126, Revision 4
October 2017
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Three-Phase Padmounted Distribution Transformers
TABLE OF CONTENTS
ImportantSafetyInformation........................................................................................................................2
Section 1: Introduction.................................................................................................................................5
Section 2: Receiving, Handling and Storage..............................................................................................….6
Drawings and Documents.........................................................................................................….....6
Lifting and Handling....................................................................................................................…..6
InitialInspection...........................................................................................................................….6
Fluid Level....................................................................................................................................….7
Internal Inspection.........................................................................................................................….7
Fluid Sampling..................................................................................................................................7
TransformerStorage.....................................................................................................................….8
Section 3: Installation..................................................................................................................................9
Lifting and Handling.........................................................................................................................9
Jacking, Skidding and Rolling............................................................................................................9
Location and Mounting.................................................................................................................….9
Verifying Enclosure Integrity............................................................................................................10
Grounding.......................................................................................................................................10
High-VoltageandLow-VoltageConnections.......................................................................................10
High-Voltage Connections..............................................................................................................10
Low-Voltage Connections...............................................................................................................11
Section 4: Inspection and Testing Before and After Initial Energization.........................................................12
Pre-Energization Inspection and Tests..........................................................................................…12
Ratio Test......................................................................................................................................12
Insulation Resistance Test.............................................................................................................12
Tap Changer Setting…………………………………………………………….........................................................12
Series/Multiple or Delta/Wye Switch Settings…………………………………................................................13
Grounding………………………………………………………………………............................................................….13
Bolted Connections……………………………………………………………...................................................….....13
Fluid Level………………………………………………………………………......................................................….....13
Fluid Temperature………………………………………………………………....................................................…...13
Internal Fault Detector...............................................................................................................…..13
Current Transformers…………………………………………………………....................................................…....13
Accessory Wiring……………………………………………………………….....................................................…....13
Tank Finish……………………………………………………………………...........................…............................….....13
Tools……………………………………………………………………………..........................................................…....13
Internal Inspection………………………………………………………………....................................................…..13
Post-Energization Inspection and Tests……………………………………...............................................….....14
Verifying Correct Voltage...........................................................................................................…...14
Checking for Leaks……………………………………………………………...................................................…......14
Observing Operation..............................................................................................................…......14
Checking Gauges………………………………………………………………..................................................…..14
Audible Sound…………………………………………………………………......................................................…....14
Locking the Terminal Compartment…………………………………………….........................................….......14
Section 5: Operation of Switching and Protective Devices………………................................................................15
Tap Changer……………………………………………………………………...................................................................15
Series/Multiple or Delta/Wye Switch………………………………………….........................................................16
Load-Break Switch…………………………………………………………..................................................................…16
Fuses………………………………………………………………………..................................................................…......16
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Three-Phase Padmounted Distribution Transformers
Internal Weak-Link Cartridge Fuse……………………………………………..........................................................17
Bay-O-Net Fuse………………………………………………………………….................................................................17
Dead-Break Dry-Well Canister Fuse……………………………………………........................................................18
Internal Partial-Range Current-Limiting Fuse………………………………….....................................................19
S&C Arc-Strangler………………………………………………………………................................................................19
S&C Fused Switch………………………………………………………………...............................................................19
Vacuum Fault Interrupter……………………………………………………….............................................................19
Surge Arresters………………………………………………………………....................................................................20
Internal MOV Surge Arresters…………………………………………….........................................................…..….20
Molded-Case Circuit Breakers………………………………………………...........................................................…21
Hot-Stick Operable Devices……………………………………………………........................................................... 21
Other Switching and Fusing Devices…………………………………………..........................................................21
Section 6: Operation of Bushings, Gauges and Accessory Devices......................................................................22
Pressure-Vacuum Gauge……………………………………………………….............................................................22
Fluid Level Gauge and Sight Plug ……………………………….........................................................................22
Fluid Temperature Gauge………………………………………………………............................................................22
Drain Valve and Sampling Device……………………………………………...........................................................22
Automatic Pressure Relief Device………………………………………………........................................................23
Internal Fault Detector…………………………………………………………..............................................................23
High-Voltage Bushings…………………………………………………………..............................................................23
Low-Voltage Bushings……………………………………………………………............................................................24
Current Transformers…………………………………………………………….............................................................24
Accessory Brackets…………………………………………………………….................................................................24
Flip-Top Terminal Compartment Cover…………………………………................................................................24
Door Handle, Padlock and Security Bolt……………………………………..........................................................24
Lift-Off Door Hinges……………………………………………………………................................................................24
Other Accessory Devices………………………………………………………..............................................................24
Section 7: Maintenance...........................................................................................................................................25
Periodic Inspection………………………………………………………………..............................................................25
Inspection Checklist………………………………………………………………............................................................26
Electrical Tests……………………………………………………………………...............................................................27
Exterior Paint Finish……………………………………………………………...............................................................28
Fluid Leaks………………………………………………………………………..................................................................28
Audible Sound Level……………………………………………………………...............................................................28
Molded-Case Circuit Breakers…………………………………………………...........................................................29
Other Accessory Devices………………………………………………………..............................................................29
Sampling and Testing the Fluid………………………………………………….........................................................29
Filtering the Fluid…………………………………………………………………..............................................................29
Removing or Lowering the Fluid………………………………………………...........................................................29
Filling with Fluid………………………………………………………………...................................................................29
Opening the Transformer Tank…………………………………………………..........................................................30
Torque Guidelines………………………………………………………………................................................................31
Table 1—Torque Guidelines for External Cabinet Fasteners………………...................................................31
Table 2—Torque Guidelines for External Bushing Mounting Hardware……..............................................31
Table 3—Torque Guidelines for External Bushing Terminal Connections….............................................32
Table 4—Torque Guidelines for Accessories………………………………..........................................................32
Additional Maintenance Instructions……………………………………...........................................................….33
Repair Parts………………………………………………………….....................................................................……….33
Warranty Claims……………………………………………………....................................................................……….
Transformer Disposal.……………………………………………....................................................................………
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Document 2.4.126, Revision 4
October 2017
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Three-Phase Padmounted Distribution Transformers
This document is intended as a general guide for
the installation, operation and maintenance of
Howard Industries three-phase compartmental
padmounted distribution transformers. Although
efforts have been made to ensure accuracy and
completeness, these instructions do not address
every conceivable application or circumstance that
might be encountered. Features presented herein
may not be present in all transformer designs.
Standard and optional features are subject to
change without notice.
The instructions contained herein are applicable
to transformers operated in normal conditions
as specied in the “Usual Service Conditions”
section of IEEE Standard C57.12.00. Questions
regarding installation, operation, and maintenance
(particularly when encountering unusual or special
circumstances not sufciently covered by these
instructions) should be directed to the Howard
Industries Transformer Division.
IT IS IMPORTANT TO READ AND COMPLY WITH
ALL SAFETY INFORMATION, INSTRUCTIONS
AND WARNINGS DISPLAYED THROUGHOUT
THESE INSTRUCTIONS BEFORE ATTEMPTING
ANY INSTALLATION, OPERATION, OR
MAINTENANCE ACTIVITIES.
SECTION 1: INTRODUCTION

Document 2.4.126, Revision 4
October 2017
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Three-Phase Padmounted Distribution Transformers
Drawings and Documents
Locate all shipping papers, packing lists, outline
drawings, and other pertinent information for
use during inspection. The transformer outline
drawing indicates the location of nameplates and
warning labels, and provides physical dimensions
and weights. The nameplate provides electrical
characteristics, winding connections, and weights.
The wiring diagram provides details of any control,
fan and alarm wiring that may have been supplied.
Lifting and Handling
Lifting hooks are provided near the top of the
transformer tank for lifting. All four lifting hooks
must be used simultaneously. The transformer
must not be lifted from any points other than the
provided lifting hooks. Do not use holes in the
lifting hooks for lifting. These holes are for tie-down
purposes only and are not suitable for lifting.
Transformers should be lifted in an upright position,
allowing the transformer to tilt no more than 15°
from vertical. Lifting cables should be no more
than 20° from vertical. It is recommended that
a spreader bar be used to keep the lifting cables
nearly vertical to enable a safe lift and to reduce
the likelihood of tank deformation or damage to
painted surfaces.
Lifting the transformer with a forklift is not
recommended, since weight and balance can be
problematic and radiator panels can be easily
damaged. Refer to the transformer nameplate
to determine the total weight of the assembled
transformer. Special care must be taken when
handling transformers when the ambient
temperature is below minus 20°C (minus 4°F);
otherwise, permanent damage to the transformer
may result.
Initial Inspection
Although all transformers, components, and
accessories are carefully inspected and tested prior
to shipment, a thorough receiving inspection should
be conducted to detect any damage or loss that
might have occurred during shipment. The receiving
inspection should be completed upon receipt and
before unloading from the truck. Note any damage
or discrepancies on the bill of lading, le a claim
with the carrier, and notify the Howard Industries
Transformer Division prior to unloading the
transformer and before attempting any repair.
Before unloading the transformer, the following
checks should be performed:
1. Read the serial number on the transformer
nameplate and make sure it matches the serial
number listed on the shipping documents. Also,
check the nameplate for kVA rating, high-voltage
rating, low-voltage rating, impedance and other
design characteristics, and make sure they
comply with the specications.
2. Check shipping documents to make sure
the shipment is complete, including all listed
accessories and hardware. Be aware that
additional items may arrive on separate
pallets. Claims for shortages or errors must
be noted on the shipping documents and
reported immediately to the Howard Industries
Transformer Division. Failure to make a timely
claim will constitute unqualied acceptance and
a waiver of all such claims by the purchaser.
3. The tank vacuum/pressure gauge may
indicate a positive or negative reading when
the transformer is received, depending on the
relative temperatures of the uid and ambient
SECTION 2: RECEIVING, HANDLING AND STORAGE
WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW MAY CAUSE DEATH OR SERIOUS
PERSONAL INJURY AND/OR DAMAGE TO
THE EQUIPMENT.
• Use a crane, suitable lifting cables or
straps, and a spreader bar to unload the
transformer.
• Do not unload using a forklift. Keep
unnecessary personnel clear while
unloading and moving the transformer.

Document 2.4.126, Revision 4
October 2017
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Three-Phase Padmounted Distribution Transformers
air. A rising or falling reading that varies over
time with ambient temperature indicates that
the transformer tank is sealed effectively. If the
vacuum/pressure gauge shows a constant zero
reading, this indicates the possibility of a tank leak.
If this occurs, the tank should be checked carefully
for leaks as indicated in the following step.
4. Check the tank for indication of uid leaks,
looking carefully at weld seams, bushings,
gauges, valves and all other tank ttings. If
suspicious indications are found, investigate
thoroughly to determine if a leak does exist
on the transformer. Indications of a leak
can sometimes be residual uid that was not
cleaned during the manufacturing process
and not an actual leak. In many cases a small
pinhole tank leak or leak from a bushing, gauge,
valve or other tting can be easily repaired on
site. Refer to the “Maintenance” section for
information about the repair of uid leaks.
5. Check for external damage including dents
or scratches on the tank walls, radiators and
terminal compartment. Dents and scratches
can often be repaired on site using simple
touch-up procedures. If touch-up painting
is performed, do not remove or obscure
any warning labels, instructional labels or
nameplates.
6. Check for broken, cracked, or damaged
bushings, gauges, valves and other ttings and
accessories.
7. Check for missing or damaged component parts
and packages that shipped separately from the
transformer.
Fluid Level
The transformer is shipped from the factory with
dielectric uid lled to the proper level. Before
energizing the transformer, verify proper uid level
by observing the uid level gauge. The uid level
gauge pointer should be between the “High” and
“Low” marks. For transformers supplied with a uid
sight plug, the uid level can be directly observed
if it is within acceptable range. If the transformer
does not have a uid level gauge or sight plug, the
uid level can be checked by removing the liquid
level plug located at the 25° C mark. Exercise
caution when checking the uid level using the uid
level plug, as the uid may spill out and may be
extremely hot. When checking the uid level, bear
in mind that the level will vary as a function of uid
temperature.
A transformer found to have a low uid level should
be checked for potential leaks and lled to the
proper level with the same type of liquid as that
specied on the transformer nameplate.
Internal Inspection
An internal inspection of the transformer tank is
rarely necessary and is recommended only when
there are obvious indications that the transformer
has received severe impact damage during transit
or when necessary to perform recommended pre-
energization tests or inspections. Do not open the
transformer tank without authorization from the
Howard Industries Transformer Division.
If the transformer tank must be opened, refer to
“Opening the Transformer Tank” for instructions.
Fluid Sampling
Sampling and testing of the uid is not required
unless there is indication that moisture or other
contaminants have accidently entered the tank
during transit. If moisture or contaminates in the
uid is suspected, contact the Howard Industries
Transformer Division immediately for instructions.
If uid sampling is required, refer to “Sampling the
Fluid” for instructions.
WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW MAY CAUSE DEATH OR SERIOUS
PERSONAL INJURY AND/OR DAMAGE TO
THE EQUIPMENT.
• Do not energize the transformer if the
uid level is low.
• Maintain proper uid level at all times
while the transformer is energized.
• Exercise caution when checking the uid
level with the uid level plug, as the uid
may spill and may be extremely hot.

Document 2.4.126, Revision 4
October 2017
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Three-Phase Padmounted Distribution Transformers
Transformer Storage
Transformers may be temporarily stored if properly
prepared. It is recommended that transformers
be stored completely assembled. Prior to storage,
transformers should be thoroughly inspected as
described above in the “Initial Inspection” section.
If the transformer is not completely assembled,
separate components and accessories should be
stored in a clean dry area in their original shipping
containers. Do not store the transformer in a
corrosive environment.
If the transformer is to be stored for an extended
period of time before being placed into service,
it should be stored on a rm level surface. The
gas space above the insulating uid should be
pressurized with dry nitrogen to a pressure of 2-3
PSIG. This will prevent a negative internal pressure
that might draw moisture into the tank.
It is recommended that the transformer be
inspected periodically while it is in extended
storage. Ensure that an effective pressure seal
is maintained, and check for leaks and corrosion.
Any damage or defects should be repaired
immediately.

Document 2.4.126, Revision 4
October 2017
9
Three-Phase Padmounted Distribution Transformers
Lifting and Handling
Lifting hooks are provided near the top of the
transformer tank for lifting. All four lifting hooks
must be used simultaneously. The transformer
must not be lifted from any points other than the
provided lifting hooks. Do not use holes in the
lifting hooks for lifting. These holes are for tie-down
purposes only and are not suitable for lifting.
Transformers should be lifted in an upright position,
allowing the transformer to tilt no more than 15
degrees from vertical. Lifting cables should be no
more than 20° from vertical. It is recommended
that a spreader bar be used to keep the lifting
cables nearly vertical to enable a safe lift and
to reduce the likelihood of tank deformation or
damage to painted surfaces.
Lifting the transformer with a forklift is not
recommended, since weight and balance can be
problematic and radiator panels can be easily
damaged. Refer to the transformer nameplate
to determine the total weight of the assembled
transformer. Special care must be taken when
handling transformers when the ambient
temperature is below minus 20°C (minus 4°F);
otherwise, permanent damage to the transformer
may result.
Jacking, Skidding, and Rolling
The transformer tank base is designed for jacking,
skidding and rolling. Do not use radiator ns,
bushings, valves, pipe ttings, gauges or sheet
metal surfaces for jacking. Jacking must be done
using the proper jacking provisions from two
adjacent corners simultaneously to prevent warping
of the tank bottom. When rolling, use an adequate
number of rollers to distribute the transformer
weight evenly. Refer to the transformer outline
drawing for the total weight of the assembled
transformer.
Location and Mounting
Consult local and national codes to ensure that
the installation meets all applicable requirements.
Location of the transformer must permit it to
operate in conditions that meet the requirements
specied in the “Usual Service Conditions” section
of IEEE Standard C57.12.00. Operation not
meeting these service condition requirements will
compromise transformer capacity and reliability,
unless the transformer is designed specically
for operation in conditions other than usual
service conditions. Contact the Howard Industries
Transformer Division, if additional information is
needed about location and mounting issues not
covered by these instructions.
The transformer should be mounted on a level
concrete foundation of sufcient strength to
support the weight of the completely assembled
transformer. The transformer should sit ush with
the surface of the pad, so that there are no gaps
that might compromise tamper resistance of the
terminal compartment. The installed transformer
should not tilt in any direction more than three
degrees. Greater tilt may compromise insulation
uid coverage of live parts within the tank and may
prevent insulating uid from circulating properly
through the cooling radiators. Improper circulation
of insulating uid may cause overheating and
reduced transformer life.
The transformer should be located at least 24
inches (710 mm) from any obstruction and
have adequate clearance to allow the terminal
compartment doors to open fully. When installing
transformers designed for indoor operation,
adequate air inlets and outlets must be provided at
the mounting location for proper cooling.
WARNING
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW MAY CAUSE DEATH OR SERIOUS
PERSONAL INJURY AND/OR DAMAGE TO THE
EQUIPMENT.
• Use a crane, suitable lifting cables or
straps, and a spreader bar to unload the
transformer.
• Do not unload using a forklift. Keep
unnecessary personnel clear while
unloading and moving the transformer.
SECTION 3: INSTALLATION

Document 2.4.126, Revision 4
October 2017
10
Three-Phase Padmounted Distribution Transformers
Avoid locating the transformer in corrosive areas.
Remove any shipping braces and packing material
that may have been installed at the factory.
Verifying Enclosure Integrity
Three-phase compartmental padmounted
transformers are designed and constructed to be
tamper resistant according to the requirements
of IEEE Standard C57.12.28 or C57.12.29, as
applicable, and therefore need not be located
in a restricted area. Do not modify the tank or
terminal compartment in such a way that it will
compromise tamper resistance. If for any reason
modications must be made to the tank or terminal
compartment that compromise tamper resistance,
the transformer must then be located in a restricted
area. Such modications of may void the warranty.
Consult with the Howard Industries Transformer
Division before making any modications to the
transformer.
Grounding
The transformer must be permanently grounded
according to applicable local and national codes.
Ground the transformer by using ground pads or
nuts located at the base of the front panel in the
terminal compartment. Do not use hold-down
bolts, pipe connections or any other ttings for
ground connections. A proper low-resistance ground
connection is necessary for safe operation.
Transformers with a grounded wye high-voltage
winding and a wye low-voltage winding are
designed for electric distribution systems that
have a grounded neutral. All windings designed for
grounded neutral operation must be permanently
and solidly grounded to the system neutral.
High-Voltage and Low-Voltage Connections
Before making high-voltage and low-voltage line
connections, check to make sure that all mating
connector surfaces are clean and smooth.
Connections must be tightened appropriately to
prevent overheating and possible failure of the
connection. Refer to the nominal torque guidelines
contained in Table 3. Connections should be made
with care to avoid placing undue stress on the
bushings.
High-Voltage Connections
Three-phase padmounted transformers with
live-front construction are usually supplied with
externally-clamped porcelain high-voltage bushings
for connection to the high-voltage source. Bushings
are supplied with tin-plated eye-bolt or spade
terminals that are suitable for connection to both
aluminum and copper conductors.
Three-phase padmounted transformers with dead-
front construction are supplied with universal
bushing wells, one-piece (integral) bushings or
universal bushing wells with factory-installed
inserts. One-piece (integral) bushings and bushing
inserts are designed to interface with insulated
elbow connectors, and can be supplied for either
load-break or non load-break operation.
When transformers are supplied with bushing wells
only, inserts must be installed in the eld before
cable connections can be made. Bushing well
inserts must compatible with the universal bushing
well. Do not use incompatible or improperly
rated inserts, or equipment damage might occur.
When installing inserts, follow the manufacturer’s
instructions accompanying the insert.
On transformers with dead-front construction,
grounding caps must be installed on all unused
high-voltage bushings before energizing.
DANGER
Do not make any modications to the
transformer that might compromise its
tamper resistant construction. FAILURE TO
FOLLOW THIS INSTRUCTION WILL RESULT IN
DEATH OR SERIOUS PERSONAL INJURY, AND
DAMAGE TO THE EQUIPMENT.
DANGER
The transformer must be properly grounded
at all times. FAILURE TO FOLLOW THIS
INSTRUCTION WILL RESULT IN DEATH OR
SERIOUS PERSONAL INJURY, AND DAMAGE
TO THE EQUIPMENT.

Document 2.4.126, Revision 4
October 2017
11
Three-Phase Padmounted Distribution Transformers
Low-Voltage Connections
Three-phase padmounted transformers are
normally supplied with externally-clamped molded
low-voltage bushings, with or without spade
terminals.

Document 2.4.126, Revision 4
October 2017
12
Three-Phase Padmounted 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.
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 indicated on the
transformer nameplate. If the transformer
is supplied with high-voltage taps, measure
the ratio at each tap position to ensure
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 resistance of the insulation
between windings and from each winding
to ground. Follow the instructions and
safety precautions provided by the test
equipment manufacturer. Prior to the test,
bushings must be thoroughly cleaned with
denatured alcohol to remove any moisture
or contaminates that could inuence the
test results. Measured resistance should be
at least 1.0 GΩ.
An insulation resistance test must not
be performed on a wye-wye connected
transformer with an Ho-Xo bushing without
rst disconnecting the internal connection
between the primary and secondary
neutrals. This connection can be found on a
terminal board located below the uid level
in the transformer tank. Refer to “Opening
the Transformer Tank” for instructions.
3. Tap Changer Setting—Check the tap
changer setting to ensure it is set to the
proper position for the required voltage.
SECTION 4: INSPECTION AND TESTING BEFORE AND
AFTER INITIAL ENERGIZATION
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 qualied 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-ash 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.
DANGER

Document 2.4.126, Revision 4
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13
Three-Phase Padmounted Distribution Transformers
4. Series/Multiple or Delta/Wye Switch
Settings—Check series/multiple and delta/
wye switch settings to make sure they are
set to the correct position. If delta/wye
or series/multiple connections are made
using an internal terminal board instead
of a switch, check to ensure that these
connections are made properly according
to the chart on the transformer nameplate.
Refer to “Opening the Transformer Tank” for
instructions.
5. Grounding—Check to ensure that the
transformer tank is permanently 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
connections for tightness, referring to
nominal torque guidelines contained in
Tables 1 through 4.
7. Fluid Level—Check to make sure the uid
level is correct as indicated by the uid level
gauge or sight plug. If the transformer does
not have a uid level gauge or sight plug,
the uid level can be checked by temporarily
removing the liquid-level plug located at the
25° C mark.
8. Fluid Temperature—Observe the uid
temperature gauge and make sure the
temperature is no lower than indicated
below before the unit is energized.
-20°C (-4°F) for conventional
transformer oil
-0°C (32°F) for R-Temp uid
-10°C (14°F) for FR3 uid
9. Internal Fault Detector—If the transformer
is supplied with an Internal Fault Detector
(IFD), remove the red shipping lock
after installation and before placing the
transformer into service.
10. Current Transformers—If current
transformers (CTs) are present, connect CT
leads to the metering load. If CT leads are
not connected to a metering load, they must
be shorted together and grounded before
the transformer is energized.
11. Accessory Wiring—Check wiring of control
and alarm circuits (if supplied) to make
sure there are no loose connections and no
damage to wire insulation.
12. Tank Finish—Check all painted surfaces
to make sure that there is no damage or
corrosion.
13. Tools—Check to make sure that all tools and
equipment are accounted for.
14. Internal Inspection—The transformer tank
is sealed and should not be opened unless
necessary. If the transformer tank must be
opened, refer to “Opening the Transformer
Tank” for instructions.

Document 2.4.126, Revision 4
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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 uid 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 uid level
and uid temperature gauges to conrm the
proper uid level and temperature.
5. Audible Sound— It is normal for transformers
to emit an audible humming sound, which
is primarily caused by alternating magnetic
ux in the transformer core. Amplitude and
harmonic content of the sound is inuenced
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 ip-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 qualied 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-ash 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.

Document 2.4.126, Revision 4
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15
Three-Phase Padmounted Distribution Transformers
The following operating instructions and
descriptions of switching and fusing devices are
intended to be a general guide for operation of
Howard three-phase padmounted transformers in
normal environments. Although efforts have been
made to ensure accuracy and completeness, these
instructions and descriptions do not address every
conceivable application or circumstance that might
be encountered. Personnel should read and comply
with any safety and instructional labels that might
accompany an accessory device.
Many of the accessory devices described below are
optional and may not be present in any particular
transformer design. The inclusion of particular
accessory devices in any transformer design is
governed by industry standards and by individual
customer specications.
Tap Changer
The de-energized (no-load) tap changer may be used
to adjust the voltage ratio of a transformer while it
is de-energized. It is intended to allow adjustment of
the output (secondary) voltage to the rated value. Do
not use the tap changer to raise or lower the output
voltage to any voltage other than that indicated
on the transformer nameplate. If the tap changer
is set to provide an output voltage different from
rated secondary voltage, core saturation may occur,
resulting in a high noise level and high core loss.
SECTION 5: OPERATION OF SWITCHING AND PROTECTIVE DEVICES
DANGER
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW WILL RESULT IN DEATH OR SERIOUS
INJURY, AND DAMAGE TO THE EQUIPMENT.
• Do not operate load-break equipment if a
fault condition is suspected.
• Use a live-line tool (hot stick or shotgun
stick) to operate transformer load-break
equipment.
• After operating transformer loadbreak
equipment, check that voltages at
transformer terminals are the expected
values. Checking voltages veries that
loadbreak equipment operated properly
and that electrical circuit conditions are
as expected.
• Before servicing the transformer,
ALWAYS de-energize the transformer
from a remote upstream source and
then proceed to ground all primary
and secondary transformer terminals
following industry-accepted safe
grounding practices. Grounding secondary
terminals protects against situations
such as a standby generator energizing
transformer from the secondary circuit.
• Follow industry-accepted safety practices.
Utilize personal protective equipment
when working with this equipment.
DANGER
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW WILL RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND DAMAGE TO THE
EQUIPMENT.
• Do not operate a de-energized (no-load)
tap changer unless the transformer is
totally de-energized.
• Do not re-energize the transformer unless
the tap changer handle is locked into
position.
DANGER
FAILURE TO FOLLOW THE INSTRUCTIONS BELOW
WILL RESULT IN DEATH OR SERIOUS INJURY,
AND DAMAGE TO THE EQUIPMENT.
• Do not operate uid-immersed load-break
fusing and switching devices when the
insulating uid temperature is below the
following limits:
-20°C (-4°F) for conventional
transformer oil
-0°C (32°F) for R-Temp uid
-10°C (14°F) for FR3 uid

Document 2.4.126, Revision 4
October 2017
16
Three-Phase Padmounted Distribution Transformers
The tap changer is operated by use of a rotating
handle located inside the terminal compartment.
Never operate a de-energized tap changer while the
transformer is energized. Tap changers normally
have ve or seven tap positions as indicated on
the tap changer dial plate and the transformer
nameplate. A locking mechanism is normally
provided to lock the tap changer into position and
prevent accidental operation. Do not re-energize the
transformer until the tap changer is rmly locked
into a tap position. The transformer is shipped
from the factory with the tap changer in the rated
voltage position, unless otherwise specied by the
customer.
Series/Multiple or Delta/Wye Switch
Transformers designed with series/multiple
windings (dual-voltage or triple-voltage
transformers) are supplied with a de-energized
series/multiple switch. Transformers with re-
connectable delta/wye windings are supplied with
a delta/wye switch. The presence of either of
these switches will be indicated on the transformer
nameplate.
The transformer must be completely de-energized
before operating either of these switches. If the
transformer is not de-energized before operating
the switch, personal injury and permanent
equipment damage will result. Unless otherwise
specied, series/multiple transformers are shipped
from the factory with the series/multiple switch in
the highest voltage position.
Load-Break Switch
One or more rotary under-oil load-break switches
may be supplied on the transformer and located in
the high-voltage compartment. These switches can
be either two-position (ON-OFF) switches or three-
or four-position sectionalizing switches. Switch
positions are marked on the transformer front panel
and shown on the nameplate diagram. Rotary load-
break switches are designed to be operated with a
live-line tool (hot stick or shotgun stick) and should
not be operated by hand.
The two-position switch is operated by inserting
the live-line tool into the operating handle and
rotating the switch to either the ON or OFF position.
The three- or four-position switch is operated by
inserting the live-line tool in the index plate and
moving the plate over the peg between its present
setting and the next setting. The index plate
prevents the switch from switching more than one
position at a time. The live-line tool is then inserted
into the switch operating handle and turned until
the switch snaps into the next position. Repeat this
procedure until the switch is in the desired position.
Do not stop and reverse direction of the switch
before it has changed position, as this will damage
the switch mechanism.
Fuses
A blown fuse may indicate a faulted transformer.
Do not replace a blown fuse unless the cause of the
fuse operation has been identied and corrected.
Fuses should be applied according to the fuse
rating. Replacement fuses should have the proper
rating and operating characteristics. Refer to the
circuit diagram on the transformer nameplate for
the location of fuses.
DANGER
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW WILL RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND DAMAGE TO THE
EQUIPMENT.
• Do not operate a de-energized series/
multiple or delta/wye switch unless the
transformer is totally de-energized.
• Do not re-energize the transformer
unless the series/multiple or delta/wye
switch handle is locked into position.
CAUTION
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW MAY RESULT IN MINOR OR
MODERATE PERSONAL INJURY, AND /OR
DAMAGE TO THE EQUIPMENT.
• Do not operate a load-break switch by
hand. Operate only using a live-line tool
(hot stick or shotgun stick).
• Do not stop and reverse direction of the
load-break switch before it has changed
position.

Document 2.4.126, Revision 4
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17
Three-Phase Padmounted Distribution Transformers
Internal Weak-Link Cartridge Fuse
A weak-link cartridge fuse is an internal, uid-
immersed expulsion fuse. These fuses are installed
under uid inside the transformer tank on mounting
blocks located above the core and coil assembly.
These fuses can be replaced in a de-energized
transformer by removing the tank hand-hole cover.
1. Make sure the transformer tank is properly
grounded.
2. Remove the tank hand-hole cover. Refer
to “Opening the Transformer Tank” for
instructions.
3. Identify the fuse block assembly.
4. Remove leads attached to each end of the
cartridge fuse, being careful not to drop any
nuts or washers into the tank.
5. Replace the fuse and reconnect leads to
their original positions using the washers
and nuts removed in step 4.
6. Re-install the tank hand-hole cover. Refer
to “Opening the Transformer Tank” for
instructions.
Bay-O-Net Fuse
A Bay-O-Net is a uid-immersed, draw-out, dead-
front, single-pole fused disconnect device that is
rated for load-break operation. It is designed to be
operated with a live-line tool (hot stick or shotgun
stick) and should not be operated by hand. Bay-O-
Net devices (one device per phase) are normally
located in the high-voltage compartment near the
high-voltage bushings. The Bay-O-Net is available as
an expulsion fuse device or as a full-range current-
limiting fuse device.
A Bay-O-Net expulsion fuse device is equipped with
a series-connected uid-immersed isolation link,
or if specied by the customer, a series-connected
partial-range current-limiting fuse. Isolation
links and partial-range current-limiting fuses
are designed to blow in the event of an internal
transformer fault. A transformer with a blown
isolation link or partial-range current-limiting fuse
cannot be re-energized and must be removed from
service.
DANGER
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW WILL RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND DAMAGE TO THE
EQUIPMENT.
• De-energize the transformer before
replacing fuses.
• Do not energize or de-energize a
three-phase transformer using single-
phase switches or fuses. Use only
gang-operated three-phase switches to
energize or de-energize a three-phase
transformer.
• Do not operate the transformer with any
phases open.
• Only qualied personnel with appropriate
measurement devices should measure
the voltages on the transformer. DANGER
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW WILL RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND DAMAGE TO THE
EQUIPMENT.
• Bay-O-Net fuse devices are not
recommended for fault closing.
The Bay-O-Net device should not be
used to re-energize a transformer that is
suspected to be faulted.
• Operate the Bay-O-Net device with a
live-line tool (hot stick or shotgun stick).
Never operate the Bay-O-Net device by
hand.
• After replacing a blown fuse, the
transformer should be re-energized from
a remote location.
• Operate the pressure relief device to vent
pressure in the transformer tank before
unlatching a Bay-O-Net device to prevent
hot oil from being expelled during fuse
removal.

Document 2.4.126, Revision 4
October 2017
18
Three-Phase Padmounted Distribution Transformers
The following procedure should be used to operate
a Bay-O-Net fuse device. Open both compartment
doors and engage the prop rods on each door to
latch them in the open position. On transformers
supplied with a hinged terminal compartment cover,
disengage the center security bolt and raise the
cover until the support arm latches in place.
Remove Fuse Holder—The following procedure
should be used to draw the fuse holder out of the
Bay-O-Net housing.
1. Vent the transformer by operating the
pressure relief valve. Keep the valve open
until the sound of air venting can no longer
be heard.
2. Stand to one side of the Bay-O-Net device
being operated.
3. Attach a live-line tool to the holder eye.
4. Twist the live-line tool to unlock the fuse
holder.
5. Rotate the holder 90° clockwise in the
housing to break the seal between the
gasket and the housing.
6. Firmly and quickly pull the fuse holder out
about 8 to 10 inches to open the circuit.
Wait a few seconds while the uid drains
back into the tank, and then completely
withdraw the fuse holder. Wipe the fuse
holder and cartridge to remove excess uid.
7. If uid continues to ow from the Bay-O-Net
device, operate the pressure relief device
again to vent pressure from the tank.
Replace Fuse Link—Replace the fuse according to
the manufacturer’s instructions included with the
replacement fuse.
Re-Insert Fuse Holder—Re-insert the fuse holder
using the following procedure.
1. Using a live-line tool attached to the eye of
the fuse holder, re-insert the holder rmly
into the Bay-O-Net housing.
2. Twist the locking handle, latching it to the
shoulder of the Bay-O-Net housing. Make
sure that the metal washer is positioned
tightly on the end of the Bay-O-Net housing.
3. Inspect the fuse holder carefully to make
sure it is fully seated and latched properly.
Dead-Break Dry-Well Canister Fuse
The dead-break dry-well canister is a uid-tight,
single-pole, current-limiting fuse holder. It is
designed to be operated with a live-line tool (hot
stick or shotgun stick) and should not be operated
by hand. Dry-well canisters (one per phase) are
mounted on the transformer front panel in the high-
voltage section of the terminal compartment.
Dead-break dry-well canisters are not designed to
break load and must only be operated when the
transformer is de-energized. When specied, dry-
well canisters are mechanically interlocked with a
load-break switch to prevent removal of the fuses
while the transformer is energized.
The following describes proper operation of the
dead-break canister device.
Remove Fuse Holder—The following procedures
should be used to remove the fuse holder.
1. Make sure the transformer is de-energized.
2. Attach a live-line tool to the hook eye.
3. Quickly pull the fuse holder assembly
completely from the housing.
Replace Fuse—The fuse should be replaced using
the following procedure.
1. Unscrew the fuse from the fuse holder.
2. Replace with new fuse of equivalent rating
and characteristics.
3. Tightly screw the new fuse onto the fuse
holder.
DANGER
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW WILL RESULT IN DEATH OR SERIOUS
INJURY, AND DAMAGE TO THE EQUIPMENT.
• Do not operate a dead-break canister
fuse device while the transformer is
energized.
• When replacing a blown current-limiting
fuse, the transformer should be re-
energized from a remote location.

Document 2.4.126, Revision 4
October 2017
19
Three-Phase Padmounted Distribution Transformers
Re-Insert Fuse Holder—Re-insert the fuse holder
using the following procedure.
1. Attach a live-line tool to the hook eye.
2. Insert the fuse holder into the housing.
3. Push the fuse holder in rmly until the
dust cap seats against the housing and
grounding clip.
Internal Partial-Range Current Limiting Fuse
Internal partial-range (backup) current-limiting
fuses (one fuse per phase or two parallel fuses per
phase) are connected in series with low current
interrupting devices, such as weak-link cartridge
fuses or Bay-O-Net expulsion fuses. Partial-range
current-limiting fuses are designed to clear low
impedance (high current) faults, while expulsion
fuses are designed to clear a high impedance fault
or overload. When properly applied, partial-range
current-limiting fuses will operate only for internal
transformer faults. When a partial-range current-
limiting fuse has blown, the transformer should be
considered faulted and removed from service.
S&C Arc-Strangler
The S&C Arc-Strangler (one per phase) is a 200
Ampere, air-insulated, load-break, single-pole device
that is designed to be operated with a live-line tool
(hot stick or shotgun stick). The Arc-Strangler device
may include a full-range current-limiting fuse on the
switch blade or a clip-style current-limiting fuse.
To operate the switch, insert the live-line tool in the
operating hook and pull forward, swinging the Arc-
Strangler open. To remove the Arc-Strangler, insert
the live-line tool in the hinge opening and lift up.
S&C Fused Switch
S&C fused switches should be operated according
to instruction provided by S&C. S&C tools should be
used to operate an S&C fused switch.
Vacuum Fault Interrupter
The vacuum fault interrupter (VFI) transformer
is equipped with a three-phase molded vacuum
interrupter mounted in the high-voltage section of
the terminal compartment. This device is capable
of making, carrying and automatically interrupting
currents through 12,500 Amperes (symmetrical) at
distribution system voltages of 5 kV to 38 kV.
The device combines vacuum interrupters,
programmable electronic control, trip-free
mechanism and universal molded elbow connection
interfaces. The control is eld programmable
with a wide range of time-current characteristic
curves and trip settings and is SCADA capable. The
molded vacuum interrupter should be operated and
maintained according to the VFI manufacturer’s
instructions provided with the device.
DANGER
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW WILL RESULT IN DEATH OR SERIOUS
INJURY, AND DAMAGE TO THE EQUIPMENT.
• Arc-Strangler devices are not
recommended for fault closing. Arc-
Strangler devices should not be used
to re-energize a transformer that is
suspected to be faulted.
• Operate Arc-Strangler devices with a
live-line tool (hot stick or shotgun stick).
Never operate by hand.
• After replacing a blown fuse, the
transformer should be re-energized from
a remote location.

Document 2.4.126, Revision 4
October 2017
20
Three-Phase Padmounted Distribution Transformers
Surge Arresters
Surge arresters can be used in three-phase
padmounted transformer installations to protect the
transformer and underground cable from damage
due to voltage surges.
Surge arresters should be installed only on
systems where the power frequency voltage at the
arrester does not exceed the published maximum
continuous operating voltage (MCOV) values.
Disconnect surge arresters before performing
impulse, induced-potential or applied-potential
tests; otherwise, the arresters may be damaged.
Reconnect surge arresters after testing and before
placing the transformer into service.
Internal MOV Arresters
Internal metal-oxide-varister (MOV) surge arresters
are designed to be uid immersed and mounted
inside the transformer tank. It is recommended that
uid-immersed MOV arresters not be exposed to an
average oil temperature exceeding 90°C (194°F)
and a maximum oil temperature exceeding 125°C
(257°F).
Disconnect uid-immersed MOV surge arresters
before performing impulse, induced-potential or
applied-potential tests; otherwise, the arresters
may be damaged. Reconnect surge arresters after
testing and before placing the transformer into
service.
Optional arrester disconnectors provide a means
to disconnect the uid-immersed MOV arrester
grounds for transformer testing without entering
the transformer tank. Individual disconnectors are
provided for each MOV arrester. Two different styles
of disconnectors are available, one manufactured
by ERMCO Components Inc. (ECI) and one
manufactured by Cooper Power Systems (CPS).
These two styles operate differently as indicated
below.
Before testing the transformer, disconnect the
arresters using the following procedure for the
disconnector on each phase.
1. Make sure the transformer tank is properly
grounded.
2. De-energize the transformer from a remote
location.
3. Ground all bushings and terminals.
4. Disconnect the MOV arresters by operating
the disconnectors as described below.
For the CPS disconnector (identied by a
black plastic external cap):
a. Unscrew the black disconnector cap
from the shaft.
b. Re-attach the small diameter end of
the disconnector cap to the shaft.
c. Push the handle and shaft toward
transformer until the shaft ange is
ush to the sealing gland.
For the ECI disconnector (identied by a
7/16” square brass metal head):
a. Unscrew the 7/16” square metal head
until the thread disengages.
b. Pull the shaft out to its full extent
(approximately 2”).
5. It is now safe to perform impulse, induced-
potential or applied-potential tests.
After testing the transformer, reconnect the MOV
arresters using the following procedure.
1. Make sure the tank is properly grounded.
2. De-energize the transformer from a remote
location.
3. Ground all bushings and terminals.
4. Reconnect the MOV arresters by operating
the disconnectors as described below.
For the CPS disconnector:
a. Pull the disconnector handle and shaft
fully away from transformer.
DANGER
FAILURE TO FOLLOW THE INSTRUCTIONS
BELOW WILL RESULT IN DEATH OR SERIOUS
PERSONAL INJURY, AND DAMAGE TO THE
EQUIPMENT.
• De-energize the transformer from a
remote location and make sure all
transformer terminals and bushings
have zero voltage before connecting or
servicing surge arresters.
• Disconnect all surge arresters before
performing impulse, induced potential or
applied potential tests.