11 Potential transformer_Storage and transportation

© 2021 HitachiEnergy. All rightsreserved.
Power Transformer- Transportation Receiving Inspection &
Storage
2021-11-10
1

© 2021 Hitachi Energy. All rightsreserved.
After test, oil is drained & external fittings & accessories (bushings, coolers,
conservators etc) are disassembled
TRANSPORT MODES
 Oil Filled
 Nitrogen Gas filled
 When oil filling would exceed the permissible or economical maximum transport weight or
if specifically demanded by the customer
 Filled with dry nitrogen at a positive pressure of 0.175 kg/sq cm( 2.5 psi) before dispatch.
CHECKS FOR TRANSPORTATION
 Prevent the transformer from sliding during transport.
 The positions of lifters, hauling to be used as anchoring points
Dismantling & Transport
2

HANDLING DURING LOADING, AND ON SITE LIFTING TRANSFORMERS
 Hydraulic hoists to be used at the jacking pads provided (see outline drawing).
 Lifting to be carried out simultaneously and uniformly for at least two adjoining
jacking pads.
Note: Never use Pipe flanges and valves as lifting or support points.
3

SUSPENDING TRANSFORMERS
The transformer must be suspended from points shown in the outline drawing.
The ropes must never form smaller angle than 60 degrees to the horizontal.
Thus, dimension “L” must be equal to or larger than dimension “M”
4

SHIPPING
 Large Power Transformers are normally shipped on special low bed trailors.
 Accessories dispatched separately by road, oil drums by road.
 Regular check of tank pressure during shipping and storage times necessary to ensure that there is
no leakage.
5

Transformer shipping showing tie-rods and blocking
6

ARRESTING TRANSFORMER MOVEMENT ON TRAILOR BED
7

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Transformers
Receiving Inspection &
Arrival at Site
8

Inspection to be carried out:
 Measurement of core insulation resistance to ground.
(Min. Acceptable value : 500K when measured at 1000V DC, corrected
to 20oC.)
 All tie rods must be undamaged and nuts and cables must be tight
 Is all blocking tight and in good condition?
 Any evidence of load shifting in transit
 Does the impact recorder indicate any impacts beyond the acceptance zones?
 Indications of external damage : broken glass on gauges, broken welds etc.
 Paint finish damage
 Whether attached fittings are still in place and undamaged (see the outline drgs)
Receiving Inspection & Arrival On Site
9

 Evidence of oil leakage around valves, fittings, flanges and tank seams
 Damages to Bushings : Porcelain chipping
 Bushing Oil level
 Delivery of all major components and accessory boxes as per packing list
 Do crates or boxes show evidence of damage or moisture ingress?
 Temporary shipping silica gel breather desiccant color
 Detached radiators, coolers and pumps must have openings closed with blind
flanges and plugs.
 Any pressure loss in gas filled transformer tanks must be included in the
acceptance report.
 Excess pressure of 0.05 bar should be maintained as minimum.
10

-20 -10 0 10 20 30
Temperature O
C
30
20
Pressure kPa
10
0
Pressure variation w.r.t. temperature
11

12

INTERNAL INSPECTION
 Necessary if transport damage is suspected.
 Avoid internal inspections to the extent possible. If necessary carry out inspection only in the presence of
transformer manufacturer.
 Before removing the tank cover or any other cover, ensure there is no overpressure in the tank.
 Do not leave tools or other objects inside the tank, they can cause short-circuits and failure of transformer.
13

Unloading, Moving & Storing
14

UNLOADING
 Use suitable overhead crane.
 Raise transformer from the car bed with jacks and then skid or roll in to the desired
position. Jacking should be done at designated jacking pads only.
15

MOVING TRANSFORMERS
 Special Moving devices
 Skids
 Sliding surfaces (with the aid of lubricants) can be used.
 Armored rollers can be placed under the transformer
List of tools & Equipment needed for moving, available in the instruction Manual
16

STORAGE
STORING INDOORS IN A DRY ROOM
 Insulating material such as paper, pressboard, Bakelite, wood, cottons tape etc.
 Insulated items as paper insulated conductors, pressboard insulated shielding body etc.
 Chemicals as solvents, glues, varnishes, hardners etc.
 Breathers and drying agents
 Terminal boxes, connection boxes, control cabinets
 Turrets with built in current transformers.
17

 Gas relays, oil-level indicators, thermometers, pressure valves etc.
 Pipes to oil conservator, pipes to radiators, pipes to turrets etc.
 Bushings
 Marshalling box, OLTC motor drive, fans, pumps, instruments and fittings
 Control cabinets
( If Heating elements provided, they shall be connected to supply)
18

STORING OUTDOORS
 Main transformer with mounted accessories.
 Oil conservator with blanking plates for all openings.
 Radiators and coolers with blanking plates for all openings.
 Structures, A frames, pipe supports, oil conservator supports, radiators, control cabinets etc.
19

LONG DURATION STORAGE
TRANSFORMER DISASSEMBLED : WITH LOWERED OIL LEVEL
A transformer with lowered oil level (i.e. the entire insulation of the core and coil
assembly has to be completely covered with oil) must be provided with a
dehydrating breather during storage, in order to avoid the ingress of humid air in
the transformer tank.
In case heating elements are installed in the motor drive cabinet, and control
cabinet, they must be connected to a power supply system to prevent the
formation of condensation water. The heating elements shall be checked at
regular intervals.
20

The silica-gel content of the dehydrating breathers is to be checked every
2 weeks. When more than 2/3 of the blue silica gel filling have turned light,
the filling has to be exchanged. However, it can be reused after having
been dried at 120 °C (24 hrs.).
At the same time the tank has to be examined for oil traces. Should any
leakage be detected, they have to be sealed immediately. Before
commissioning and after a long storage the oil is to be checked for
moisture content. Motor drive cabinet and control cabinet have be checked
for Condensation of water.
21

TRANSFORMER WITH DRY-GAS FILLING
In case it is not possible to store the transformer completely mounted or with oil filling, the transformer is to be filled
with dry gas in order to prevent the ingress of moisture during storage.
After the transformer has been filled with dry gas/ air, one or several gas cylinder attached to the tank has to be
connected. In order to provide a constant positive pressure in the transformer tank, the gas cylinders are connected
via pressure reducing and pressure relief valve. The valves have been adjusted to maintain a positive pressure in
the tank i.e. approx. 0.25 bar. The pressure is to be checked every two weeks.
pressure must not fall below 0.05 bar.
22

The condition of the silica gel content in the dehydrating breathers has to be
checked every 2 weeks. Should more than 2/3 of the blue silica gel filling have
turned light, the filling must be exchanged. However, it can be reused after drying
at 120 °C (24 hrs.). At the same time it is necessary to check the oil level in the
conservator, and to examine the tank for oil traces. Should any leakage be
detected, they have to be taken care of immediately. Before commissioning and
after long storage the oil is to be checked for humidity.
23

ACCESSORIES
The accessories shall be stored in compliance with the printed-on storage instructions and the hints
given in the brochures for the individual accessory parts. In principle the accessories should be stored
in their respective transport packing in dry rooms. Possibly, desiccant bags have to be enclosed in the
crates.
All accessories shall be protected against damages.
24

CHECKLIST FOR PACKAGE
Time periods
SUBJECT CHECK YEAR MONTH REMARKS
Insulating oil Dielectric
Moisture content
strength 1
Oil level Conservator 1
Oil tightness Tank 1 1
Conservator, piping, 1
Buchholz relay, Bushings 1
Earthing Tank 6
Fans Test run 3 1 Hr.
Control cabinet Heating 1
Oil circulation pumps Trial run 3 1 Hr.
Silica gel breathers Silica gel 1
25

11 Potential transformer_Storage and transportation

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