Guide on transformer transportation

673
Guide on transformer transportation
Working Group
A2.42
December 2016

Members
A. Mjelve, Convenor NO
J. Hermans, Secretary BE
W.J. (Bill) Bergman CA
T. Boroomand UK
S. Chen FR
P. Cole AU
J. Huygh BE
K. Melai NL
F.T. Pereira Da Silva BR
K. Ryen NO
A. Schönauer DE
J. Schnieders DE
A. Vintila RO
A. Van der Werff FR
M. Wilfling AT
WG A2.42
Copyright © 2016
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“CIGRE gives no warranty or assurance about the contents of this publication, nor does it accept any responsibility, as to the
GUIDE ON TRANSFORMER
TRANSPORTATION
ISBN : 978-2-85873-376-7

GUIDE ON TRANSFORMER TRANSPORTATION
Page 1
GUIDE ON TRANSFORMER
TRANSPORTATION
Table of Contents
EXECUTIVE SUMMARY.........................................................................................................4
1 Introduction............................................................................................................................5
2 Objectives of the Guide.....................................................................................................6
3 Glossery of Terms................................................................................................................7
4 Transport Incidents – Case Studies.................................................................................10
4.1 Introduction..........................................................................................................................10
4.2 Australian Incidents............................................................................................................10
4.3 Norwegian Incidents..........................................................................................................15
4.4 Swedish Incidents...............................................................................................................17
4.5 North American Incidents..................................................................................................18
4.6 United Kingdom Incidents.................................................................................................24
5 General Design Requirements and Considerations.....................................................26
5.1 Design Requirements for Transport and Good Industrial Practices .........................26
5.2 Design for Vibrations........................................................................................................26
5.3 Design Requirements from Standards............................................................................28
5.4 Design Practices for Optimizing the Transformer for Transport...............................30
6 Specification.......................................................................................................................31
7 Design Review....................................................................................................................32
7.1 Design Review Protocol ....................................................................................................32
7.2 Specifications and Standards..........................................................................................32
7.3 Method of Design Verification........................................................................................32
7.4 Scope of Transportation and Installation......................................................................33
7.5 Design Review Checklists..................................................................................................33
8 Transportation Modes and their Specifics ....................................................................37
8.1 Road.....................................................................................................................................37
8.2 Rail........................................................................................................................................42
8.3 Marine and Inland Waterways......................................................................................60
8.4 Air.........................................................................................................................................70
9 Shock Recorders.................................................................................................................74
9.1 General information..........................................................................................................74
9.2 Use of Shock Recorders....................................................................................................78
10 Shock Recorder Application and Data Interpretation................................................84
10.1 Introduction to Limiting Curves.........................................................................................84
10.2 Limiting Curves ...................................................................................................................87
10.3 Interpretation of Measured Shocks ................................................................................88
10.4 Updating of Design Limits................................................................................................90
10.5 Design Review Guidelines................................................................................................91
11 Indication of Centre of Gravity ......................................................................................92
11.1 Requirements for the Graphical Symbol to indicate the CoG..................................92
11.2 Recommendation for respecting the CoG indication ..................................................93

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11.3 Indication of the Centre Line............................................................................................93
11.4 Indication of the CoG of a Package of Transformer Components ..........................93
11.5 Example of Graphical Symbols to Indicate the Different CoG’s.............................94
12 TRANSPORTATION PROCESS.........................................................................................97
12.1 International regulations on transportation – Incoterms® rules................................97
12.2 Tender Process ................................................................................................................108
12.3 Transportation Assessment ............................................................................................109
12.4 Transport Planning..........................................................................................................112
12.5 Responsibilities ................................................................................................................117
12.6 Measures to secure safe transport..............................................................................117
12.7 Handling at load breaks...............................................................................................118
12.8 Handling at site...............................................................................................................119
13 Transport Drawing and Instructions.............................................................................122
14 Load Securing..................................................................................................................123
14.1 Introduction.......................................................................................................................123
14.2 Load Securement Methods – Indirect and Direct Securement................................123
14.3 Examples - Accidents and Load Securement.............................................................124
14.4 Quick Reference: 11 Significant Directives for Load Securing..............................126
14.5 Legal Requirements........................................................................................................127
14.6 Chain Lashing...................................................................................................................127
14.7 Supporting Equipment - Friction Mats.........................................................................128
15 Transport With and Without Oil..................................................................................129
15.1 Transportation and Storage without Oil ....................................................................129
15.2 Transportation and Storage with Oil..........................................................................130
16 Testing...............................................................................................................................131
16.1 Transformer Testing........................................................................................................131
16.2 Transformer Weighing...................................................................................................131
16.3 Monitoring Management of Transformer Transportation .......................................134
16.4 Transformer Evaluation during and after Transport................................................134
17 Conclusions and Recommendations..............................................................................137
ANNEXES ........................................................................................................................ 139
Annex 1 – Derivation of Shock Limiting Curves..............................................................................139
Annex 2 - Maximum Static Acceleration (Horizontal Line)...........................................................142
Annex 3 - Defining Indicative Energy Curve for a Square Shock, based on Maximal Allowed
Energy Content................................................................................................................143
Annex 4 - Convert Maximal Velocity Change to Maximal Energy Content ............................144
Annex 5 – Transformer Tests and Operations Flowchart after Transportation.......................145
Annex 6 - Catalogue of operations and tests after transformer transportation.....................146
Annex 7 - Measuring Results..............................................................................................................147
Annex 8 - Data Analysis of Real World Incident (Detailed Example of Shock Recorder Data
Analysis)............................................................................................................................152
Annex 9 - Examples - Transport Drawings (-plans) ......................................................................158
Annex 10 - Not recommended Examples to Indicate a CoG .....................................................161
Annex 11 - Not recommended Examples to indicate a Centre Line..........................................163
Annex 12 - Transformer Standards and Guides –(Informative).................................................164
REFERENCES, PHOTOS, FIGURES AND TABLES............................................................... 165
References ...........................................................................................................................................165
Table of Photos.....................................................................................................................................167

Page 3
Table of Figures ...................................................................................................................................168
Table of Tables ....................................................................................................................................170

Page 4
EXECUTIVE SUMMARY
This Technical Brochure (TB) reviews all the significant aspects related to transport of power transformers. In general
TB consists of three parts: transport incidents, design guidelines and related issues and transport process.
This TB presents a large number of transport incidents - case studies collated from the countries around the world.
Each case study is explained with a summary of the events, the consequences of the incident, and a discussion of
the “Lessons learned”.
In the design section, the TB addresses the precautions applicable to mechanical design of transformers for
withstanding the anticipated transport forces and shocks applicable to different transport modes - road, rail, marine,
inland waterways, and air. The chapter for general design include requirement, provide background for industry
best practices and design guideline recommendations.
International Standards design requirements are reviewed and general remarks and proposals for improvements are
included. New proposals for indicating the transformer tank centre of gravity and centre line are included, which may
be considered for standardisation.
Recommendations for preparing transformer transport: -specification; -design review; -important discussions on
transformers design; and safeguarding are included in dedicated chapters of the guide.
The recording and evaluation of shocks and vibration occurring during transport are important for the transformer
manufacturer and the customer. All features of shock recorders (SR) are explained including general information for
SR function, physics, and operation. Guidelines for positioning of SR and the set-up values for the journey are given,
in general these are important factors which are used for analysis of the reordered data. In addition, discussion of
“real world” example is included. TB also includes recommendations for weighing transformers prior to transport.
Large power transformers transport weight in transport configuration in many cases can be at the lawful authorities’
permissible limit fixed for the transport infrastructure.
The transport process section of the guide offers a complementary overview and explanation of different Incoterms®
rules and their applicability to transformer transportation. A thorough review of the transport planning process is
given: the detailed steps to be considered and the responsibility for each step are also included.
A section in the TB describes transformer load securing methods, handling at load breaks and at site, measures to
achieve safe transformer transport, and storage with or without oil.

Page 5
1 Introduction
During the CIGRE SC A2 meeting in Paris in 2008, a WG on transformer transportation damage was proposed. The
discussions in the SC revealed this topic was too narrow and should be extended to include a guide on the broader
aspects on transformer transportation. Several examples of severe transformer damage were mentioned, including
recent events involving scrapping of transformers after derailment during rail transportation, crane and bridge
collapses. SC members especially from South Africa and Australia had experienced many mishaps and strongly
supported this new WG proposal.
Guidance on how to perform impact measurement during transportation and the interpretation of the measurements
is not mentioned in the IEC 60076 series. Guidance for mechanical designs and on what to do in the event of a
transportation event seemed necessary. Guidance on the magnitude of g-forces at which the transformer should be
internally inspected at site, moved to the factory for a more thorough inspection, and which failure modes may be
expected should be addressed by the WG.
This Working Group liaised with the WG A2.36 Guide for Transformer Procurement Process where the CIGRE
brochure on Design Review was revised. Requirements on transportation issues are included in the mechanical
design review process.
As relevant examples, it may be mentioned that increased new EU rules for the height of railway station platforms
have made problems for transformer transportation. Lack of maintenance of utility owned wharfs designed for special
transformer transportation vessels have also caused concern. Other transportation infrastructure changes continue
to make the transportation of transformers increasingly difficult.
Bulk substations supplying the metropolitan areas are historically located outside the city centres, but are often
“fenced in” by urbanisation with increasing transportation problems. Road and police authorities are increasingly
reluctant to close highways and temporarily strengthen bridges. New tunnels may not be made to previously agreed
cross sections or capacities due to budget limitations. Level crossings of railroads and motorways are changed to
underpasses causing change of transportation routes and conditions. These changes compel constant transportation
planning and review as part of the asset management of the transformer fleet. Some guidance is needed for this
process of continuous review of transportation routing.
Transformers have been transported ever since they have been manufactured. The degree of sophistication and
complexity of this transportation has increased with time.

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2 Objectives of the Guide
The objectives of the guide include providing:
1) A framework for the design review of the transportation related features of the transformer for the
expected transportation modes and resulting forces.
2) General design requirements and elements as guidelines for transformer mechanical designers and
purchasers.
3) Information and data that can assist a transformer manufacturer in developing the transfer function
between accelerations applied to the base of a transformer (or other location of attaching the transformer
to the transporter) and the active parts of the transformer, particularly the top of the core and clamps.
4) Guidance on the information to be incorporated into a transportation and handling drawing.
5) Guidance to transformer designers on the features required for movement of the transformer during all
of the various stages of transportation from the factory to the substation foundation including:
a) Ship
b) Barge
c) Railway
d) Highway road transport
e) Off road transport
f) Jack and slide (jack & roll) on and off loading
g) Mobile crane handling
h) Gantry crane handling
6) Guidance on features for securing the transformer to the transportation carrier:
a) Shock (impact) recorder theory and how to interpret readings from shock recorders
b) When to perform specialised receiving tests on the transformer
c) When to perform an internal inspection on the transformer and what indications of damage to
look for during internal inspection.

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3 Glossery of Terms
AAR: Association of American Railways
Ballast: The means of maintaining the balance, stability, and height above the water level of a barge
while the load mass is being redistributed due to loading, unloading or movement of the
load. Ballasting is usually accomplished by adjusting the water levels in various tanks or
chambers within the vessel itself or the extra mass added to one side of a rail car shipment
to bring the centre of gravity to the centre of the rail car.
Bill of Lading: Documents describing the items, quantities, and destination of goods to be carried by the
transportation company. The Bill of Lading accompanies the goods during transportation
and usually acts as a receipt when the goods are delivered.
Cribbing: Temporary support materials, such as timbers or steel beams that are used to support a
load at a particular elevation during lifting, lowering, sliding or rolling operations. Cribbing
may also be used for support of the equipment during temporary storage, also called
blocking.
CoG: Centre of Gravity – The mass centre of a given component or assembly.
DB: Deutsche Bahn
Depressed-centre A heavy-duty rail car that has an open centre deck between the trucks
Rail car: that is lower than the height of the decks above the trucks/wheels.
Dimensional load: A large piece of equipment loaded for shipment on a rail car or truck with over dimension
and/or over-weight classification.
Dunnage: Loose packing material used to protect a ship’s cargo from damage during transport. Loose
material laid beneath or wedged between objects carried by ship or rail to prevent injury from
chafing or moisture, or to provide ventilation.
Forwarder: A firm specializing in arranging transportation and storage on behalf of other companies
Frequency A test performed on a transformer or reactor to help determine if any internal damage has
Response Analysis been caused during transportation. This test is also used as an analysis tool to determine
Test (FRA): if damage has occurred from system short circuits. Test results before and after transport
are compared.
g (static): A continuous acceleration in a certain direction
IMO: International Maritime Organisation
Impact recorder: A device which records accelerations, g’ forces usually in the longitudinal (X-axis), lateral
(Y-axis) and vertical (Z-axis) directions. Impact recorders (or shock recorder) may have
pre-set or user-settable threshold magnitude of impact registered, may measure magnitude
of impact only, may measure magnitude and duration of the impact (energy).
Incoterms®: (International Commercial Terms) are a series of international sales terms, published by the
International Chamber of Commerce (ICC) and widely used in international commercial
transactions.
Interchange: A designated point where railcars are exchanged between railroad companies,
normally a designated inspection point. This is only a Rail shipment term included
in AAR definitions.

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“Jack and slide”: A procedure using hydraulic jacks, slides and cribbing materials to raise or lower a load onto
a set of beams or rails. The load is then pulled via the pulling eyes facilities or pulled/pushed
by hydraulic rams to slide or roll the load along the beams in order to locate the load in its
final position. Also known as “jack and roll” or “jack and glide”.
Lifting lugs: Special connection points on equipment tanks that are designed to support the weight of the
equipment (or other load) while being lifted from these points using a crane.
Load Break: Load break (or Trans loading) is the process of transferring a shipment normally from one
mode of transportation to another.
Multiwheel units: Trailers or self-propelled units for in-plant transportation in seaports, industry, logistics and
distribution centres.
Metacentre: The point of intersection of the vertical through the centre of buoyancy of a floating body (as
of a vessel) with the vertical through the new centre of buoyancy when the body is displaced.
Metacentric height: The distance between the centre of gravity and the metacentre of a floating body, as of a
vessel.
Originating carrier: The carrier on which the shipment originates.
Railway Industrial An association of those involved in providing rail clearance data for over-dimension and
Clearance over-weight rail cargo loads.
Association (RICA):
Receiving carrier: The carrier that accepts the shipment from another (delivering) carrier, usually at a
designated point of interchange.
Rigging: Equipment and materials such as lifting beams, slings, steel cables, shackles, etc. that are
used for lifting and lowering. The process of lifting and moving vertically or horizontally any
load using mechanical load-shifting equipment to move, place or secure a load.
RO/RO (Ro-Ro): Roll-on/roll-off ships are vessels designed to carry wheeled cargo, such as trucks, trailers,
and railroad cars that are driven on and off the ship on their own wheels or using a platform
vehicle, such as a self-propelled modular transporters.
Securement: The devices used to secure a load to the ship, carrier, or rail carriage.
Securing: To make firm or tight; to fasten; to capture or confine (Synonyms: fasten, anchor, secure.
These verbs mean to cause to remain firmly in position or place.). Sometimes referred to
as “lashing and bracing” or “tie-down.”
Schnabel rail car: A special rail car designed to support a load from connection points on each end, making
the load a structural part of the rail car. These rail cars are used to move very large and
heavy loads, and may require a dedicated train service.
Transport drawing: A drawing which profiles the height, width, length, weights, and centre of gravity of the
transported equipment. This drawing is used by transporters and permitting agencies to
determine type of equipment required for transport and the route. (Sometimes referred to
as “Transportation drawing”, Transport plan” or “Shipping drawing”).
Transport marks: Notation stencilled onto the equipment main tank and accessory crates that identifies the
destination of the equipment and parts, and provides identifying numbers in order to ensure
that the equipment is delivered to the proper destination. Also referred to shipping marks.
Shock load: A dynamic load - in this guide on the transformer.
Shock recorder: See Impact recorder

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Trans loading: See Load Break
UIC: Union Internationale des Chemins de Fer (International Union of Railways).
Note: In this brochure, the term “shipping” is reserved for transportation by ship.

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4 Transport Incidents – Case Studies
4.1 Introduction
A transport incident is a sudden, unintentional or intentional, externally initiated event resulting in damage to a
transformer. Such an accident is triggered by external shock (impact), technical failure or human error.
Transformer incident is said to have occurred, when non-permissible force of shock(s) takes place at levels exceeding
the limits of the design. Such force of impact can take the form of collisions, inclination, acceleration or vibrations.
Force of impact is both vectorial and temporal (length of exposure) by nature.
In the case of acceleration or deceleration, both magnitude and duration must be considered. In case of vibrations,
both the frequency and the incidence must be considered. Often, even though the acceleration levels accompanying
low magnitude vibration do not exceed the design levels, they can cause significant damage if they excite natural
frequencies of transformer components.
In the case of inclination, e.g., the rolling of the ship in heavy seas, the frequency and angle of inclination are decisive
factors with regard to potential damage. Again, the acceleration levels often remain below the design values.
Visual inspection of the interior and exterior is recommended in case of intensive vibrations or extreme inclination.
The effects of force of impact can be documented in the form of data from a shock (impact) recorder and/or the
existence of internal and/or external damage.
A number of different modes of transportation are available. Likewise, various different carriers may be involved.
It is always expedient to examine the shock (impact) recording, perform a visual inspection of the exterior for damage
and record the findings at the time of handover to the next carrier (interchange).
If any recorded data shows non-permissible levels and/or if the transformer exhibits external damage, then further
action must be discussed and agreed with the responsible parties (customer / manufacturer / insurer / carrier).
If the transformer has more than one shock recorder, they must be synchronized such that all data are recorded
simultaneously. Ensure that the shock recordings occurred during the transportation duration, although the
transformer may have been stationary at the time of shock damage.
In addition, the transformer should have been in-transit at the time of the recordings. The transformer might not be
moving although it is “in transit”. The transformer could be stationary at the time of damage.
The working group has collected several transport incidents as case studies. Some of the information about these
incidents originates from the public domain (internet, private parties sending information and Study Committee /
Working Group members). Not all information has been verified by the involved parties and hence must be
interpreted in this context.
The incidents are chosen to give background for the understanding and interpretation of the content of the different
chapters in the Guide. It is not the intention to criticize any particular manufacturer, forwarder or purchaser, but to
learn from the incidents. Hence, all reference to manufacturers, forwarders or purchasers names are excluded from
the text. However, some pictures may show manufacturers or forwarders names. The need to mask these names
seems unnecessary as the lessons learned are universal.
4.2 Australian Incidents
The Working Group (WG) member from Australia has collected transportations mishaps and incidents experienced.
The incidents describe interesting aspects of transportation on the background of reregulation of the industry. The
responses are slightly edited, and where mentioned, the WG has inserted some additional information.
Australia Incident # 1
In the 1990’s and earlier, the State owned generation and Transmission Company had several rail wagons for
transporting large items. There were special rail wagons for transformers and another for generators (complete with

Page 11
sideways jacking of the beams to enable the transporter to travel through the rail tunnels). Some generating stations
still have heavy lift rail siding where the loads can be transferred; still on the beams onto road transport.
In the 2000’s, one generating station (who do not have any written documents or standards) had a strong preference
for rail transport for a 500kV transformer (245t) and started investigating using the rail. The rail track people said a
firm NO. They did not know how to do it, the rail was too busy and the platforms had all been modified. They were
not interested. They asked the Roads and Traffic Authority (RTA) and they said that we could not transport such a
load on the road in New South Wales and suggested we talk to the railways.
This situation was resolved with a high level conference in the Premier’s department, where the RTA were ordered
to develop routes for heavy items such as generator transformers and generators. The new transformers came into
a local harbour and up the highway, causing major disruption on the way. The cost of these disruptions to the
community is obviously very high. The risk of a traffic incident from impatient drivers is also a major concern.
Note that in this case planning was done by the contractor with the responsibility for transport clearly and wholly with
the contractor.
Lessons learned:
Route planning also involves regular contact with the road and rail authorities to make sure a good relation exists.
For some routes, the road authorities should safeguard a minimum profile and axle-/maximum load.
Our contracts are written so that we take responsibility for the transformer once it has been successfully erected at
the specified site. However, we do specify particular requirements which help us assess if we should have a concern
due to what may have happened during the transportation of the transformer to site.
Included in one of our technical schedules, we ask the manufacturer to specify the maximum 3 dimensional g force
rating of the main tank design. We specify that the 3 dimensional g-forces must be recorded for the main tank starting
prior to loading the transformer for transport at the manufacturer's factory and up until the main tank is successfully
positioned on the customer's plinth on site. The device used for this purpose shall be of an approved type. We
specify that a copy of the 'g' force recording must be supplied to us as soon as practical after the transformer has
been positioned on the plinth.
If g-force peaks which exceed the manufacturer's specified maximum withstand capability are noted in any direction,
we consult with the manufacturer but ultimately the specification allows us to demand an internal inspection. During
the internal inspection, clearance dimensions of the active part with respect to the side wall and end wall are recorded
and then compared with design dimensions from the factory. Other electrical testing may follow depending on what
is seen and ultimately a decision is made to either accept the transformer or reject it.
There have been a number of incidents caused by incomplete route survey being performed by the transport
company. The survey must be completed from the factory right up to the transformer concrete plinth in the substation,
not just for the highway. Some examples are;
1) SVC transformer had to be stored for more than 1 month while the route was confirmed.
2) 375MVA transformer was delayed on route due to the transport company having no knowledge of a
bridge on route which was already being rebuilt. The site access road into the substation was also later
found to be an issue and an extra bull dozer was required to pull he load up a hill on a dirt road.
3) 375MVA transformer control cubicle was damaged due to side swiping a rock face during access to the
substation.
4) 150MVA SVC transformer vertical plate lid stiffener hit the underside of a bridge during highway transport
due to main roads resurfacing the road and not amending the height clearance signage.
5) 75MVA transformer was driven under a bridge and the 11kV tertiary bushings were impacted and broken
off.
Other issues have involved loads that were not secured correctly, or poorly maintained equipment.
6) Many years ago, one transformer dropped into the river while being unloaded from a transport ship.
7) 100MVA transformer rolled over during transit due to a chain breakage and subsequent load shift on the
flatbed trailer.

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8) Transformer rolled over while negotiating a round-about on a flatbed trailer.
9) Chain snapped whilst a new 250MVA transformer was being skated into place. Transformer was almost
written off.
10) 15MVA Transformer being sent for refurbishment (1998-99) fell off the truck.
11) Transport of 200MVA Transformer to site almost resulted in the transformer and truck slipping down an
embankment.
More general issues are;
12) Parallel beam transport can be more expensive and flatbed transport is sometimes used instead. The
flatbed trailer may then lead to height constraints which directly impact the route selection.
13) 375MVA Transformers were delivered to the wrong site.
Lessons learned:
Transport planning should not be left to the forwarder alone and the plan should be reviewed by future owner. A
factual check of the planned route's profile during planning is necessary.
A 330kV, 100 MVAr shunt reactor was being delivered from a port in Sydney. The transport company was chosen
by the overseas supplier with limited knowledge of the company's experience, which had been with the delivery of
bulldozers etc. and probably some smaller transformers.
This company had not previously transported
transformers for the utility, and was not experienced with
this type of load.
The semi-trailer tipped over on the approach to a major
bridge near the Sydney CBD, blocking the morning peak
hour traffic. The reactor core was damaged and the
reactor subsequently scrapped.
Indications are that as the semi-trailer entered the bend,
there may have been a problem with a bogie at the front
of the trailer. This dropped the front and caused it to dig
into the road for about 50m until the trailer finally flipped
onto its side. It seems possible that the trailer could have
been under rated for the load. The reactor remained
attached to the trailer.
It is understood that two cranes were needed to lift the reactor to distribute the weight on the bridge to avoid damage.
Lessons learned:
Experienced forwarders should be selected with proven records and references.
A 144MVA newly rewound transformer had a shock recorder installed to the transformer. However when the
transformer arrived at site, the shock recorder was switched off. It appears that it was not switched on when the
transformer left the factory. FRA and other tests were conducted to verify that no movement of the core and coils
had occurred.
Lessons learned:
Procedures should safeguard the impact recorders are switched on before departure, or the impact recorders, if
possible, may be set with a future start during installation of the impact recorders.
One utility is in the process of planning to transport seven single phase 90 MVA 330kV single phase transformers
via road transport (approximately 1 500km) to an underground power station.
PHOTO 1 - TILTED REACTOR AT THE ANZAC BRIDGE IN SYDNEY

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Some of the issues confronted so far are:
1) The transformers will be transported with the 200kV RIP oil – oil bushing installed (this has been approved
by the bushing manufacturer)
2) Transformers will be transported on parallel beams because of height constraints (in the power station
access tunnel)
3) The transformers will be unloaded in the power station using the station crane
4) Within the power station, from the loading bay to the transformer cells is a system of rail tracks. The new
transformers have been designed with bogey wheels so that these tracks can be used to move the
transformer from the transport into position.
5) The final section of the power station access road is owned and maintained by Snowy Hydro. Civil works
have been required to repair the road in preparation for the transformer transportation.
6) Because of the steepness of the access road and tunnel, two tractor units will be used to control the load.
7) Some of the local roads and bridge load ratings have been de-rated by local authorities to reduce
maintenance requirements.
Lessons learned:
Some of the control measures used to ensure the transformer is not damaged in transit include:
a) Full route survey, do not trust previous experience.
b) Shock-recorders installed on the transformer at the factory, with pictures of installation and showing the
recorders are turned ON.
c) SFRA tests done at the factory and repeated after installation.
Another utility reported several problems in recent years due to lack of maintenance. A number of sites required a
fixed crane to unload the transformer from the truck – and in one case onto a purpose built trolley which run along a
rail system. The subs had the cranes installed. However, after 40 years of not being used – and in recent years not
being maintained (cost saving initiative), major refurbishment of the cranes was required to allow the transformer to
be replaced. Of course the purpose built trolley also needed to be rebuilt.
Another case involved a hydraulic ramp which was required to get the truck into the substation. The ramp had not
been maintained. Fortunately none of these transformers failed and required urgent replacement!
An incident occurred when it was necessary for a 120MVA transformer to travel down a steep hill near the substation
where it had to be installed. The grade of the road was checked by surveyors, and the transporters confirmed that
the transformer could be transported safely, even if the road was wet. However, as the trailer proceeded slowly down
the road it began to slip on the wet road. A major incident was averted when the tailgate of the trailer was quickly
lowered. This scraped onto the road and acted as a brake. Investigation revealed that the wheels of the trailer were
travelling along a painted road marking, which was much more slippery than the roadway. This had not been
considered in planning the job.
A number of recent incidents involved getting trucks into difficult sites. An experienced supervisor met with the
transport company prior to the transformer move to plan the job and determine the correct equipment for the job.
Problems occurred when the transport company then provided different equipment (e.g. trailers).

Page 14
An example is shown in the photo to the side. The wrong trailer
was provided. The weight of the transformer was such that it
could not be carried entirely on the low section of the trailer, as
more weight was required at rear of the trailer. Initially the
transporter placed a steel beam under one end of the
transformer, but the beam was too high; so blocks of wood were
then placed under the other end. This situation shown in the
photo was considered unsafe. The experienced utility staff
intervened and provided some of their own resources so that
the transformer could be located safely on the trailer and
transported the short distance to the scrap yard.
Other known incidents:
1) A car driver changing lanes caused the transport vehicle to stop suddenly – resulting in a broken chain and
the transformer moving on the truck resulting in damage to the transformer.
2) A transporter was struggling to get a very large transformer up a very steep hill. When the transformer was
delivered they found that someone had forgotten to drain the oil prior to despatch. If the excess weight had
resulted in an incident, a major environmental disaster could have occurred.
Lessons learned:
Transport preparedness includes substation area and local roads.
Some time ago after delivery to site of a 255 MVA generator step-up transformer, the core and windings were found
to be seriously damaged. The tank was the only part of the transformer that was re-used. The transformer was of 5
limb construction and the top of the core was supported only at the ends. The transformer had been shipped from
Europe and similar designs had been shipped to other countries without incident.
It was clear that the transformer tank had not moved during the sea journey, however, rough seas were encountered
between New Zealand and Australia and it is believed that the angle of rolling of the ship was greater than normal,
possibly exacerbated by a reduced amount of cargo over this section of the route. Impact recorders were not used
at that time.
A replacement was provided with additional transport supports provided along the core.
Lessons learned:
It was clear that the transformer tank had not moved during the sea journey, however, rough seas were encountered
between New Zealand and Australia and it is believed that the angle of rolling of the ship was greater than normal,
possibly exacerbated by a reduced amount of cargo over this section of the route. Impact recorders such are
currently fitted to all large transformers were not used at that time.
A rail boom gate came down on top of a transport vehicle while travelling over the rail crossing. The departure of
vehicle had been delayed and instead of arriving at the crossing with a clear two hours to cross before the first train,
it was at the time of the first train. The only item damaged was the boom gate. Following this all rail crossing have
been manned for the crossing of such vehicles to avoid any chance of a collision.
Lessons learned:
Following this all rail crossings have been manned for the crossing of such vehicles to avoid any chance of a collision.
Transport plan must also include clear instruction what must be done if the transport is delayed. See UK incidents
for more information about risk at railway crossings.
PHOTO 2 – UNSAFE EXAMPLE OF ATTEMPT TO TRANSPORT

Page 15
Transport vehicle sank into the ground running off the roadway inside the station, due to the wrong size turning circles
and road widths at the station.
Lessons learned:
Review of civil engineering drawings performed by experienced transport planners or substation engineers before
drawings are issued for inquiry. The same applies for “As Built” drawings (drawings corrected for construction
changes).
There are several cases where the transport brackets were not properly located or sized for the local transport
vehicle. In the first case the brackets did not project out a sufficient distance from the transformer tank to properly
engage the transport beams. The bracket had to be modified after the transformer was completed. The transport
company had been sent transformer transport drawings but did not pick this up.
In the second case the transport support brackets were placed too close together for the proposed transport beams
(for 200t). The solution was to use beams for 350 t but these were longer and much more expensive to use. In this
case there was no problem with transport and since it was the transport contractor’s oversight there was no extra
cost to the utility.
Lessons learned:
A general transformer dimensional drawing with location of transport brackets, lashing- and pulling lugs, jacking pads
location and turntable size should be part of the inquiry.
370 MVA 3 phase low impedance 500 kV transformers could not be transported by road from the preferred port.
However such units (200 t transport mass) could be transported from an alternate port at some extra cost. This
alternative arrangement would also have to be use in the case of a failure. The extra cost of using single phase
transformers could not be justified.
Prior to delivery of these transformers, a number of beams had to be designed and manufactured to allow one of
the transformers to be stored on the wharf, as it was necessary to spread the load over the piled area. Storage of a
transformer at the wharf avoided the high demurrage cost of having the heavy lift vessel wait at the wharf until delivery
of the first transformer was completed.
Lessons learned:
Contingency storage should be evaluated as part of the transport plan.
4.3 Norwegian Incidents
Norway Incident # 1
A 20 MVA transformer in a substation in the southern part of Norway was handed over to the scrapping contractor,
who emptied the transformer for oil, removed the bushings, and secured the transformer in the cell with lashings to
the fixed pulling lugs in the walls, due to the rail inclining towards the public street outside of the cell.
The lashings unfortunately broke/opened and the transformer rolled out of the cell, over the flatbed trailer and crushed
a parked car.
Lessons learned:
A Safe Job Analysis should have included this possibility necessitating cordon off the public parking area outside of
the transformer bay.

Page 16
Norway Incident # 2
A 250 MVA 300/132 kV three phase transformer was brought to
the a bulk substation in the city of Bergen on a girder transporter.
Unfortunately, the transport master from the manufacturer
decided to turn the transformer transport around soon after
bringing it ashore from the specialised heavy transport vessel
Elektron II.
Hence, the transformer arrived the wrong way in to the
substation. An engineer from the utility discovered this and the
next day the transformer transport was driven out of the
substation to be turned in the Y-crossing where the access road
to the substation left the local road.
However, this crossing is in a hillside with the Y-crossing having
a double curvature, the girder hanger tilted 40 degrees, and
after approximately half an hour hit the road.
Two mobile cranes could be located at either side of the
transformer and nearly overextended their loading capacity
keeping the transformer from tilting totally. Bigger mobile
cranes erected the transformer and after inspection of the
transformer, it was moved to the substation, this time the right
way.
The transformer had sustained approximately 1.5 g vertically according to the (now) obsolete mechanical impact
"recorder".
Lessons learned:
The root cause of this incident is the unnecessary turning of the girder hanger before entering the substation. A
temporary text label on e.g. the HV side of the tank with the text: "HV-side" would probably avoid such incidents.
PHOTO 4 - TRANSFORMER TILTING 40 DEGREES IN NORWAY
PHOTO 3 - TRANSFORMER CRUSHING CAR IN NORWAY (PHOTO COURTESY HAFSLUND NETT)

Page 17
4.4 Swedish Incidents
Sweden Incident #1
This rail transport consisted of a diesel engine, one heavy
weight rail cars, auxiliary wagons and passenger cars.
In the actual incident the 182 tonnes heavy transformer
(transportation weight), was transported by a heavy load rail
car weighing 260 tonnes.
One Sunday in February 2008 the heavy transport derailed
and the rail car transporting the transformer tilted to the right
in the moving direction. Both tracks were blocked. This
location is part of a double track line where maximum
allowed speed is 180 km/h and around 10 minutes before
the incident, a high-speed train had passed in the opposite
direction.
It was discovered the salvage work would be extensive,
difficult and lengthy. On this location only narrow dirt access
roads exists, but on both sides of the tracks. A base radio
station nearby had its own access road. These small private
roads could not take the load of the massive mobile cranes
necessary to lift the rail car and the transformer.
Hence, in the period from the next Monday to Friday, 2 500
lorry loads totalling 32 000 tonness of crushed stone were
moved into the area, partly to reinforce the local and dirt
roads and partly to build two “platforms” on both sides of the
tracks. One platform was for the mobile cranes and the other
platform were for stabilising the tracks and the surrounding
area.
The heavy girder hanger rail car was lifted the morning of
Saturday with the aid of two mobile cranes and lifting jacks.
Then the transformer was lifted out of the rail car. The rail
car was later moved on its own wheels to a nearby station
10 km further south for a thorough inspection.
During the Sunday, the tracks were repaired and the rail
traffic commenced Monday morning after almost eight days.
According to the following investigations, the transformer
load was not centred and some of the transformer rail car
wheels lost contact with the rail due to a smaller rail defect.
However, the root cause was the transformer was loaded the
wrong way in the rail car changing the location of the centre.
The moving parts on the rail car were also not oiled and
greased in the correct manner. This later hampered the free
movements of the eight bogies of each four axels on the
heavy loader and contributed somewhat to the derailment.
The transformer could not be moved from the location and was scrapped at site.
The cost for the salvage work and repair of the tracks was in the excess of 1.1 million EUR. Not included here is the
indirect cost of the keeping this double track main railway line closed for more than a week. Also not included is the
cost of a replacement bus service for most of the trains. The high-speed trains between Stockholm and Malmö, were
diverted to another single track railway line with delays of 20 to 45 minutes.
PHOTO 2 - RAIL CAR DERAILING IN SWEDEN
PHOTO 3 - LIFTING OF DERAILED CAR IN SWEDEN

Page 18
Lessons learned:
After this incident, the train operator procedures are changed. When transformers are transportet on double track
railway lines, the other track not used for the transformer transport is always closed for other train traffic. Girder
hanger vehicles for both rail and for road should measure the hydraulic pressure in the lifting cylinders. The wrong
off-set of the transformer would then have been discovered, also if the off-set CoG at the short side is wrongly located.
Written procedures for rail girder hanger waggons preparations for transport should be reviewed as part of
prequalification of forwarder.
4.5 North American Incidents
North America Incident # 1
Transformer was moved from the factory location in one continent to the site on another continent. Transport involved
ocean ship, rail, and hydraulic multi-wheel road transporter. The generator unit transformer was rated 150 MVA.
The mechanical type shock recorder indicated a longitudinal impact of 4.6 g, and 6.3 g transversal and 5.2 g vertical
during the rail portion of the transport. Significant core damage occurred, and damage included longitudinal
movement of the top core yoke and crushed laminated wood blocking that supported the core during transport. The
core was misaligned and wavy within the clamping structure. The blocking at the top of the coils had loosened and
required replacement. Bolts bent in the threaded rod in the coil clamping structure. The step-lap core tips were
short-circuited. The two halves of the split core were misaligned.
The current transformers moved in the bushing turrets. The transformer was received with no gas in the gas cylinder
after the one-month transport. The transformer was stored for about a year prior to internal inspection.
The delayed inspection and acceptance receipt of the transformer without inspection did cause considerable dispute.
The repair cost at a repair facility was significant, use mobile cranes to un-tank and re-tank the transformer due to
limited crane capacity at the repair facility, and the hindrance at site due to construction activities.
Lessons learned:
a) The manufacturer was unfamiliar with the magnitude of rail transport impacts encountered in North America.
The core and coil restraining systems and the current transformer mounting system were unable to sustain
acceleration forces encountered during the rail portion of the journey. Vibration likely contributed to the
transportation damage to the transformer.
b) An early and detailed inspection is essential, especially when there are indications of possible transport
damage.
A 150 MVA, 345 kV transformer was transported to a remote windfarm site after intercontinental and multi-mode
transportation involving rail transportation. The transformer started to produce combustible gases during a one-
month energizing period at no load. Internal inspection revealed sparking at the tips of the step-lap core joints as
well as loose blocking. The transformer had to be transported to a repair shop, but due to bridge collapse all bridges
of this design on the original transport route were immediately de-rated, requiring a completely different route where
bridges had to be temporarily strengthened and other temporary water crossings had to be constructed, all at great
cost.
Lessons learned:
Blocking and core support must be capable of withstanding the forces imposed. The presumptions for a planned
route used may change abruptly causing severe cost to establish another route or blocking the transformer from
being moved at all.

Page 19
A 50 MVA, 138 kV transformer was delivered between countries
within North America. The last small portion of the
transportation was by truck. The trailer hit the rails as it passed
over a railway crossing.
Lessons learned:
a) Blocking and supports were not capable of
withstanding the forces imposed by North American rail
shock and vibration.
b) It is important to investigate every portion of the
proposed route including the railway crossings which
may be used near by the substation.
A smaller power transformer was transported complete with its
radiators and oil-filled to just above the core. There was no
transport gas pressure when the transformer was received and
there were small oil leaks under the transformer radiators. The
radiators had been damaged during transportation and required
repair.
Transporting transformers with the removable radiators
installed exposes the transformer to possible transportation
damage, which can negate the costs of site assembly and oil
filling. A thorough receiving inspection may have detected the
damage somewhat earlier however, in this case all parties
agreed on the cause and timing of the damage.
A 50 MVA, 138 kV transformer was being transported during
the winter by an experienced heavy haul company and driver.
The truck encountered black ice and went into a slide. The
transformer securement chains did not hold the transformer
onto the trailer and the transformer slid and rotated several
“turns” down the highway, coming to rest at the side of the road.
The transformer was secured to the trailer by means of four
cross chains at the bottom of the transformer only.
PHOTO 6 – THE TRANSFORMER LOADED BEFORE TRANSPORT.
ONLY LOW CHAINS SECURING TRANSFORMER ON DEPRESSED
CENTRE TRAILER
PHOTO 5 - OIL LEAKAGE FROM TRANSPORT DAMAGE
(PHOTO COURTESY W. BERGMAN)
PHOTO 4 - DAMAGE TO TRANSFORMER BLOCKING
(PHOTO COURTESY W. BERGMAN)

Page 20
The driver was extremely fortunate and was not injured. The transformer damage was too severe to repair.
Lessons learned:
a) Stop when road conditions are poor or unsafe for transport, regardless of schedule. If transport cannot wait,
road friction must be secured by removing all snow and ice, brushing and sanding.
b) Reduce travel speed during poor weather conditions. This may necessitate use of an escort vehicle to warn
other traffic on the highway, or blocking highway sections temporarily for other traffic.
Several transformers in the range of 50 MVA, 138 kV were transported by truck using inter-state and inter-provincial
highways. Two of the transformers had GPS equipped shock recorders that revealed the transformers had travelled
down a long hill reaching speeds of between 115 km/h and 125 km/h. The highway had a bridge at the bottom of
the hill with an approach that caused a “bump” in the highway (vertical transition between the bridge and highway).
The different drivers from the same transportation company likely were trying to use a high speed of downhill travel
to assist with the long hill after the bridge.
There was vibration damage and other indeterminate cause of damage to various parts including bushings, radiators
and some other parts. Many gaskets were found to have small leaks.
Lessons learned:
Parts and components received in good condition is paramount to secure the transformer can be placed in service
without delays. Experienced forwarders and transporters with proven records and references should be selected for
transformer transportation.
A 125 MVA, 138 kV transformer produced by one manufacturer had some
additional testing performed by another manufacturer’s service shops. Neither
the service shop, nor the transportation company had transformer outline or
dimensional documentation from the original manufacturer.
The transportation company and the driver were not familiar with transporting
transformers. The driver and the service company had trouble in loading the
transformer and securing it to the trailer for safe travel. There were no markings
for centre of gravity although there were markings for the transformer
centreline.
Several lengths of distribution line wires were found on top of the transformer
when it arrived at site. Some minor damage occurred to items on the top of the
transformer.
PHOTO 8 - OFFSET COG TRANSFORMER
LOADED ON TRAILER (PHOTO COURTESY W.
BERGMAN)
PHOTO 7 - TRANSFORMER AND TRUCK AFTER BLACK ICE ACCIDENT IN NORTH AMERICA (PHOTO COURTESY ENMAX)

Page 21
Lessons learned:
a) The identification of the centre of gravity in the transport condition is fundamentally important.
b) Measurement of the loaded height of the transformer is very important.
c) Experienced forwarders and transport companies with proven records and references should be selected.
A transformer was unloaded from a barge on an inland waterway (river) with a relatively strong current. The tug
pushed the barge into the shore at the unloading location. Ramps were placed to drive the hydraulic trailer from the
barge onto shore.
As the transformer was on the ramps, the barge shifted position, causing the ramps to move. The transformer and
trailer upset into the river.
Barge alignment moved relative to shore causing SPMT and transformer to roll off ramps.
Lessons learned:
Barge unloading on fast moving river current requires special skills including the securement of the barge to the shore
or other fixed anchors so that it cannot move during the unloading process. A Safe Job Analysis including all possible
events must be made as part of transport planning.
A transformer was being transported along an unpaved road.
During movement around a curve in the road, the rear of the
trailer became bogged down in the soft road shoulder.
The self-steering booster on the trailer “steered” into the ditch.
The transformer did not fall off of the trailer. The trailer did not
tip. The transformer was recovered, without need for repair.
Lessons learned:
Adequate securing and caution on unimproved roads are
necessary to mitigate the risks or the transformer tipping under
potentially soft road conditions. Some conditions call for
steerable rear of the trailer. Attentive signal persons must
watch the load at all times and especially when moving along
potentially soft road conditions.
Transformers rebuild program, involved transport of a series of transformers to a factory for rebuild after many years
of smelter service. A rebuilt transformer was being returned to the customer with a planned route, a pilot car and
appropriate permits in place for the transport. The route involved bypassing travel under a specific overpass and
travel only in the centre of the two lanes under another underpass.
PHOTO 10 - TRAILER WENT INTO THE DITCH (PHOTO COURTESY
SOUTHERN CO.)
PHOTO 9 - TRANSFORMER FALLING OFF BARGE (PHOTO COURTESY SOUTHERN COMPANY)

Page 22
The driver ignored the bypass route over and around the underpass and hit the underside of the bridge breaking off
all of the LV bushings. A month later with a different driver, the pilot car provided insufficient warning for the driver
to straddle the lanes to allow passage under an arched bridge. The transformer hit the underside of the bridge
breaking off all of the LV bushings.
Lessons learned:
Despite using a pilot car and an earlier similar incident, the transport company still broke bushings and caused
extensive internal damage to the rebuilt transformers. Driver inattention is difficult to control despite extensive route
detail. Some planning for human error would benefit most transportation situations.
A large transformer was moved from one continent to North America. The final transport of relative short length was
by hydraulic trailer. A hydraulic system failure in the trailer caused the left side of the hydraulic trailer to suddenly
lower relative to the right side. The transformer slid off the trailer causing irreparable damage.
Transformer transported on hydraulic trailer. No wood was used between transformer and steel beams on trailer.
The transformer slid off the steel beams that were between the trailer and the bottom of the transformer. Steel-on-
steel coefficient of friction is much lower than wood or rubber (or other materials) and steel.
Lessons learned:
The condition of transport equipment is very important. It may not have made a difference in this case; however, the
securement of the transformer to the transporter is very important. The transformer is to be adequately secured to
the transporter even if the transporter/trailer is leaning. Similarly, the use of wood, rubber or other non-slippery (not
steel-on-steel) surface significantly assists in reducing movement of the transformer on a steel deck of a transporter.
PHOTO 12 - TRANSFORMER SLIDING OFF MULTI-WHEEL (PHOTO COURTESY SOUTHERN CO.)
PHOTO 11 - TRANSFORMER BUSHING HIT BRIDGE
(PHOTO COURTESY VTCU)

Page 23
A transformer was manufactured at a factory for export. Road, barge (river) and ship transport was required for the
166 MVA transformers. One transformer was successfully
transferred from the trailer to a barge using a gantry system.
The gantry was repositioned to transfer the second
transformer. When the second transformer was
approximately over the barge, the barge broke in half. One
transformer was mostly submerged and the second
transformer was only partially submerged.
The transformers were returned to the factory. No internal
damage was evident from settling into the soft mud of the river
bottom. All external wiring, conduits and control cabinet were
replaced. The transformers is now in service.
Lessons learned:
Experienced contractors with equipment in good condition for
the task are fundamentally important. The exact reason for
the barge failure is unknown but includes defects in the barge
as well as inadequate load bearing under the gantry supports
that were positioned in the barge.
A very large transformer was transported from Europe to North America using ocean, barge, rail and road transport.
Jack and slide transfer was used from the rail car to a trailer. One side of the transformer was angled inward from
the jacking step to the base of the transformer (to gain additional clearance). The active part of the transformer was
sensitive to any movement or deflection in the tank in the vicinity of the jacking step. When the transformer was
being lowered, the body of a jack contacted the inclined area of the transformer, slightly bending the inclined portion
of the transformer tank. A core ground was measured while the transformer was supported on cribbing. The
transformer was returned to the factory for modification and was returned in a somewhat heavier condition.
Lessons learned:
The transformer was well marked as to where jacking was allowed and where lashing was to be applied. The
transport markings and drawing was one of the best in the industry at the time of this event. The internal design was
somewhat unusual in the area around the base of the transformer. The contractor did not realize that this transformer
was more sensitive in the area around the jacking pads. There was no information on the drawing indicating the
need for additional caution. Be absolutely clear to provide specific instructions if there is anything unusual in required
handling.
A series of transformers were transported from one continent where they were manufactured and to North America.
The first three single-phase transformers were received in a single rail convoy in good condition. Three additional
transformers were received, again in a single rail convoy. Two shock recorders had been installed at the factory.
High shock magnitudes were recorded during loading and trans-loading operations as well as during rail transport.
All shocks above 3 g were in the vertical direction, except for one event during the loading operation where the shock
was in both horizontal directions. In addition, many low magnitude shocks were recorded with a strong vibration
component in the vertical and longitudinal direction. There were 50 events over 0.6 g recorded by the upper recorder
and over 100 events recorded by the lower recorder, with frequencies below 10 Hz.
The shocks were deemed to be from rail imperfections. Significant observed internal damage included:
1) Wood spacers above wood pressure rings that had moved or fallen out of position.
2) Leads with damaged outer insulation.
3) Pressboard spacers that had moved.
The transformers were repaired on site.
PHOTO 13 - TRANSFORMER SUBMERGED AFTER BARGE BROKE
DURING LOADING (PHOTO COURTESY OF TRANSALTA)

Page 24
Lessons learned:
The difference in damage between various transformer deliveries has been deemed to be due to different rail routes
used by the railways. The earliest delivery was on good track while at least one of the later deliveries was on a rail
route with poor track conditions. The transformer design needs to consider the effects of multiple shocks and low
frequency vibration during rail transportation. Knowledge of transport conditions in all conditions and countries where
transport occurs is vital to a transformer mechanical design.
4.6 United Kingdom Incidents
UK Incident # 1
On 6 January 1968, a 120-ton English Electric Co. Ltd (EE) transformer was to be moved from the former EE Works
in Stafford to an EE storage depot on the disused airfield at Hixon. The airfield was near to the railway line.
To carry out this move a huge transporter vehicle, 45 m (148
feet) long and with a 32-wheeled trailer, was chartered. It had a
gross weight of 162 tons, was impelled by a tractor unit at each
end, and had a crew of five. The figure to the right shows a
similar transport for EE.
The journey was not an unusual procedure as six other abnormal
loads had passed over the automatic crossing in the preceding
months.
The transporter and its police escort started the journey at
approximately 09:30 on the morning of Saturday 6 January.
Although the transformer storage depot was only six miles from
starting location, the nature of the load meant that it needed to
travel out of the town and then along a somewhat laborious route
via the motorway, country roads and finally to storage depot.
Confer the map to the right, which gives an example of the
diversions necessary for heavy oversized transports. The route
was approved, but the map of the route made no mention of the
railway level crossing location, which was adjacent to the depot.
At around 12:20 the transporter turned off the main road to the
final road where it slowed to walking pace as it approached the
level crossing. It stopped for a moment while the police car went
over the crossing to check where the entrance to the airfield was;
on its return, one of the police officers told driver that "this is the
place" and proceeded back over the level crossing. The trailer
needed to be raised by the crew in order to negotiate the track,
but, in addition, it needed to be low enough to clear the overhead
lines. While this was taking place, the transporter slowed to
around 2 mph (3.2 km/h). At this speed, it would take
approximately one minute to traverse the crossing.
The leading tractor traversed the two railway tracks and the main
bulk of the transporter was astride them when 11:26 the express
train 1A41 Manchester Picadilly to Euston activated the crossing sequence by operating a treadle 910 m
(1,000 yards) away. The Public Inquiry investigations showed a train at 85 mph would reach the half barrier secured
level crossing 24 seconds after the red flashing lights and bells commences. The warning lights began to flash and
the bells began to ring, with the barrier descending onto the forward part of the transformer.
PHOTO 14 - TRAILER USED AT HIXON DISASTER (©
CROWN COPYRIGHT)

Page 25
At about the same time leading tractor driver who had not heard
the bells and could not see the lights, saw the train approaching
from his left and realising that it would not stop, shouted a warning
to his crew. He then accelerated and so did the driver of the tractor
at the rear, although this meant that he was deliberately bringing
himself into the direct path of the train.
As a result of these actions, the train hit only the rear seven or eight
feet of the transformer at approximately 75 mph (121 km/h),
sheared through the trailer and threw the transformer forward and
to the left of the line.
The train consisted of electric locomotive and 12 coaches. The
locomotive and the first five coaches of the train were demolished,
and the following three coaches were derailed. Both railway lines
were destroyed for a length of 110 m (120 yards) and the overhead
lines were brought down.
Eleven people (8 passengers and 3 railwaymen) were killed, with
45 being injured; six of them seriously.
Lessons learned:
All rail crossing may be manned for the crossing of such vehicles
to avoid any chance of a collision. Anyhow, the transport plan
should include clear instruction what must be done if the transport
is delayed, and the responsibility should be clear who is doing
what.
Source:
Report of the Public Inquiry into the accident at Hixon Level Crossing on January 6th 1968 (© Crown Copyright)
PHOTO 15 - HIXON SITE AFTER THE COLLISION
(© CROWN COPYRIGHT)

Page 26
5 General Design Requirements and Considerations
5.1 Design Requirements for Transport and Good Industrial Practices
A transformer should be designed to withstand transport related forces. During the design stage, the following points
should be taken into account for transformer transport:
1) Static 1 g could be a starting point as a design limit, except for railway transport where 2 g or higher could
be required.
2) Design limits are based on static calculations.
3) Design limits for various transport modes are different. If no distinction is made for the transport mode, the
design should be for the worst case transport mode expected.
4) Good fixation of the active parts to the tank is required to prevent any movement.
5) Permanent active part supporting structures are preferred. A temporary supporting structure could also be
a solution in certain applications. Proper care needs to be taken that these parts are preserved and remain
available together with installation instructions for the transformer.
6) Fixtures attached to the clamping system should prevent and block all possibilities of movement of all core
sheet packages and individual core sheets
7) The clamping pressure applied to the core sheets should be sufficient to prevent the beginning of movement
of the core sheets.
8) The design of the lifting, jacking, haulage, blocking and lashing points on the tank should meet the
requirements for all the transport modes of the transformer. For more details, please refer to chapter 13
Transport drawings and instructions and chapter 14 Load securing.
9) The transport of a transformer with accessories should have more attention. The accessories should be well
protected.
10) Attention should be paid to the transport of accessories separately from the transformer. Some of the
handling requirements for transformer transport may be applicable to transport of accessories.
Different manufacturers have different design limit for their static calculations and it is difficult to reach a common
value higher than 1 g. If more specific information is available, this design limit could be increased or reduced. For
example, better static design limits can be derived from dynamic shock loads based on experience and design
knowledge.
There is a difference between the dynamic shock loads encountered during transport and the static design limits
used for static calculations. Static calculations are much more feasible than dynamic calculations since the latter
requires realistic input of dynamic conditions (e.g. dynamic accelerations and damping) and they are generally not
known well enough. Experience and design knowledge allows the construction of the transformer, which is based
on static calculations, to resist these dynamic shock loads. When the ability of the transformer to resist the dynamic
shock loads is found to be insufficient, it is usually the design that is changed and not the design limits.
Where the design limits for static calculations uses accelerations values, the evaluation of the shock recorder data
generally uses velocity change (energy of the shock). No relation can be made between what is measured by the
shock recorder and the static design limits for the same reason that dynamic calculations are less feasible. Therefore,
shock recorder limits are generally set to find events that are not commonly encountered during transport rather than
to limits which predict the existence of damage after transport. See Chapter 9 and 10 on shock recorder use and
interpretation of its measurements.
The limiting values for static design calculations and measured dynamic shock loads (including velocity change
criteria) should be agreed upon during the mechanical design review. See also Chapter 7 Design review requirements
on transport issues.
5.2 Design for Vibrations
If the transformer is transported over a significant distance or is subjected to large in-service vibrations, special design
considerations are necessary. Small vibrations and slow rocking motions, during short time spans, could easily be
sustained by the transformer; however they can become dangerous if they act long enough.

Page 27
At present, detailed design for vibration is not possible because the expected vibration magnitudes, frequencies and
durations are not yet well enough understood. More research (measurements) is needed to know the different
vibration levels, which can be expected in different transport modes. Secondly, the link between a given vibration
level and possible damage must also be examined to be able to create design limits for vibrations.
Slow repeated movements such as rocking and tilting can be as devastating as the better known vibrations. Again,
more research is needed to understand the different kinds of slow movements that can be expected in different
transport modes and what could be their damage potential.
Even though specific design for vibrations and slow repeated movements is not possible, some general precautions
can be taken. The most common problem that is caused by long-lasting vibrations is dislocation of components that
are only held in place by a limited amount of friction. At present there is no reliable method to estimate damage
probability of a given level and duration of vibrations. Therefore, it is preferred to take a safe approach. This means
that all components of the active part of the transformer need to be properly secured. Some issues to consider are:
1) Core laminations of the top yoke can delaminate and creep upwards due to vibrations during long railway
voyages. These laminations should be mechanically held in place in some way
2) Small insulation pieces and spacers can slowly creep out their initial location if the friction force holding them
is insufficient and if necessary these pieces should therefore be secured by mechanical way. Forces acting
are quite small. Therefore simple means like strap bands, small wooden pegs, glue or fixing by geometry
are more than sufficient. However, care must be taken that the chosen solution is compatible with hot
transformer oil.
3) Insulating blocks and spacers that form a part of the winding are clamped by the pre-clamping force. This
force is typically more than large enough to keep these parts in place, even during long railway transports.
However, it is considered prudent to lock these parts as well in the horizontal direction.
4) Small gaps that are left in the support structure of the active part against the tank will increase the (shock)
loads that are acting on the active part. Such gaps must therefore be avoided at all cost. The support
structure must provide a certain amount of adaptability to sustain mechanical tolerances on the clamping
system without leaving small gaps between tank and active part. Deforming materials like rubber or liquid
materials that harden in place are common methods to provide this kind of functionality.
5) Dampening material can be added in the support structure of the active part to reduce the vibrations that are
acting onto the active part. However, care must be taken while designing a support structure with such a
dampening component. A correctly designed dampening component will decrease the vibrations and shocks
acting on the active part, where a wrongly designed one can even increase the loads on the active part.
Also, the dampening properties of the selected material should preferably not change significantly over the
lifetime of the transformer.
6) Laminated material should be used with vibrational loads acting perpendicular to the laminations. Vibrational
loads acting in parallel to the laminations bring a significant risk on delamination of the different layers in the
material.
7) Bolted connections need to be protected against loosening. Special care needs to be taken for electrically
insulated bolted connections. Experience shows these insulated connections loosen much easier than
normal non-insulated bolted connections.
8) Brittle components should not be used to carry mechanical transport shocks and vibrations. For example,
fiberglass tubes used typically as electrical insulation for bolts should not be used to carry mechanical shear
loads.

Page 28
PHOTO 16 – EXAMPLE OF DISPLACED CORE LAMINATIONS FIGURE 1 – ILLUSTRATION OF CORE SHEET CREEPING UPWARDS
DUE TO LONG LASTING VIBRATIONS
5.3 Design Requirements from Standards
Some existing standards, at the time of issue of this Technical Brochure, give values or guidelines to design
components for transport. It is; however, of extreme importance to assess whether these values are applicable to
transport of large power transformers before these are used in design stage!
Clause 5.3.1 to clause 5.3.4 will give a short description of the best-known standards giving values for all the transport
modes of electrical components. General conclusions about these standards are given in clause 5.3.5.
5.3.1 IEC 60076-1:2011, Power Transformers - Part 1: General
The latest version of IEC 60076-1:2011 [1] standard on power transformers, stipulates with respect to transport
accelerations that the transformer must be designed and manufactured to withstand at least a 1 g static load in all
directions in addition to normal gravity.
Oddly enough, this standard also specifies that the transformer must comply with class 4M4 as per IEC 60721-3-4
[2] for mechanical stationary conditions outside the tank. The basis of this mechanical class is a continuous
sinusoidal vibration with amplitude of 1 g and frequency between 9 Hz and 200 Hz and a shock with maximal g-value
of 10 g and duration of 11 ms. These values practically mean that vibrations and forces during stationary use in
normal conditions are expected to be much worse than during transport. This 4M4 specification cannot be regarded
as a realistic working condition for a normal large power transformer and is not followed by the industry.
For normal transformers, 4M1 can be regarded as a severe but realistic working condition. Therefore the value
stipulated in IEC 60076-1 [1] should at least be changed to 4M1.
It should be noted however, that the 4M4 specification is a realistic working condition for some special class
transformers like wind turbine generator transformers installed next to the generator in the nacelle and ship board
transformers close to the engine room.
Classifications for mechanically stationary conditions in weather protected areas can be found in the related standard
IEC 60721-3-3 [3]. The mechanical classes are very similar to the classes from IEC 60721-3-4 [2]. Class 3M1 can
be regarded as a severe but realistic working condition. Class 3M4 is the same very high mechanical load and is
only realistic for special class transformers.
5.3.2 IEC 60721-3-2
IEC 60721-3-2 [4] standard describes transport conditions for (electrical) equipment. This standard provides an
excellent example of how the mechanical loads applied on a transformer should be described; both the maximal g-
value and the duration of the different possible loads are specified! The following loads are covered:
1) Stationary sinusoidal vibration: Indicated with amplitude and frequency range
2) Stationary random vibration: Indication with acceleration spectral density and frequency range
3) Shock load: Indicated with shape of the shock in the time domain
4) Free fall: Indicated with maximal drop height

Page 29
5) Possible toppling over: Indicated as yes or no
6) Rolling and pitching: Indicated with maximal angle and minimal time period.
7) Stationary acceleration: Indicated with expected maximal acceleration
8) Pressure load: Indicated with expected maximal pressure
This standard is unfortunately only applicable for components, which are significantly smaller than a power
transformer. However, the values described in this guide can provide a detailed upper limit of what can be expected
and give an excellent example of the kind of information that should be given by a standard related to transport.
Some of the loads, for example, free fall and toppling are different depending on the mass of the transported object.
An obvious recommendation is to expand this guide with appropriate values for heavier electrical components like
power transformers.
5.3.3 CTU (Cargo Transport Unit) Packing Guidelines
CTU (Cargo Transport Unit) packing guidelines [5] describe the loads, which could be expected in case the
transformer would be transported using a CTU, typically a shipping container. For the smallest power transformers
this could be a realistic transport condition. For larger power transformers, the limits in these guidelines can only
provide a broad upper limit of the forces to expect during transport.
These guidelines only give g-values. Due to lack of further information, these values should be considered as static
design values, not as actual measured peak values.
The different values mentioned in these guidelines are:
1) Road Transport:
a) 0.8g-1.2g forwards
b) 0.5 g backwards
c) 0.5 g sideways
d) No value given in vertical direction!
2) Rail Transport (Not shunted):
a) 1.0 g forwards and backwards
b) 0.5 g sideways with a dynamic variation of ±0.3 g
c) Vertical static gravity of 1.0 g
3) Rail Transport (Shunted):
a) In addition to the loads given for not shunted rail transport, loads up to 4 g in forward and backward
direction can be expected
4) Sea Transport
a) 0.4 g ±0.5 g in forwards and backwards directions
b) 0.8 g ±0.8 g in sideways directions
c) Vertical static gravity of 1.0 g
5.3.4 IEEE Std C57.150-2012
IEEE Std C57.150-2012 [6], a recent guide from IEEE, gives sound advice with respect to transport of power
transformers. However, no specific limits are mentioned. All transport loads are explained with words only.
The only remarkable part in this standard is that longitudinal impacts with a peak above 5 g are considered as rough
handling. In reality, this guideline for rough handling should be adjusted depending on the design criteria used for
the transformer and should be based on the energy content of the impact.
5.3.5 General Remarks about Standards
Most of these different standards do not give sufficient information. Giving a maximal g-value is simply not enough
to allow detailed design for transport or to interpret measurement results of a shock recorder. It is therefore, strongly
recommended that future revisions of these standards define occurring mechanical conditions with the required
detail. The different standards should give limits for maximal energy content or maximal velocity change of an event.

Page 30
This can be given, for example, by defining both the maximal g-value and the shape of the shock in the time domain.
Only IEC 60721-3-2 [4] presently provides this kind of information for transport of electrical components.
A second improvement should be to add the distinction between different sizes of loads. The heaviest masses for
objects considered in most of these standards are only applicable to the smallest distribution transformers. Most
transporters will be much more careful with heavy transports, resulting in smaller mechanical loads. The different
mechanical loads, depending on transported weights above 300 tonnes, should therefore also be shown in this kind
of standards.
5.4 Design Practices for Optimizing the Transformer for Transport
During the journey of a transformer to its final destination, the transformer active part (core windings and lead
connections) and the tank will likely become subjected to loads related to different mode of transport. Transport
loads may be a combination of shocks as results of railway shunting operation and the vibration loads during railway
side-to-side movement. Sea voyages tend to introduce a combination of forces resulting from ship movement in
pitching, rolling, heaving, surging, yawing or swaying or a combination of any two or more. The forces set up during
motorway/highway transport are very much at the control of the driver as well as the selection of transport equipment.
The forces set up during the land transport are generally well controlled by using hydraulic controlled suspension of
the multi-axial trailer. The overall design of the transformers should be withstand transportation related forces that
are expected on the journey.
5.4.1 Examples of Design Practice
The transformer active part assembly is most vulnerable to damage when the cargo is subjected to heavy transport
forces. Therefore, the active part must be designed to withstand the anticipated transport forces. The following
points list some of the guidelines and design practices applied for transport.
1) Review the transport modes and evaluate the anticipated transport accelerations for the journey and
subsequent evaluate the design intent acceleration for the journey.
2) Apply the intended design accelerations such that the complete transformer including the active part and
internal fixing points are capable of withstanding the transport loads.
3) The transformer tank should include adequate number of haulage points of adequate design suitable for the
transformer weight ensuring the complete transformer tank withstands the intended design transport loads
when the tank is safely secured.
4) The mechanical and electrical construction of the transformer implies that for the normal operation of the
transformer the core laminations are normally clamped by mean of the core clamping structure. The core
frame structure should design with the transport load in mind.
5) Clamping the transformer core laminations limbs and yokes would support the core lamination thus
preventing laminations movement during heavy transport loads.
6) Including a solid support to strengthen the core legs from bottom to the top yoke would improve mechanical
strength of the limbs against sideways deformation and lamination movement.
7) Clamping the upper and lower yoke laminations increase the stability of the main joints linking the limbs to
the upper and lower yoke improving the lamination mechanical strength.
8) The core lamination main limbs are normally clamped which improve the stability of the core during transport.
The lamination pressure design intent is specific to manufacturer design methodology and experience.
9) Notwithstanding the manufacturer’s design intent of core to earth insulation principle, bracing the core to the
core clamping structure improves the mechanical stability of the lamination during the journey.
10) Considering rough transport conditions and included with the manufacturer’s design experience, end plates
might be built-in to improve the mechanical strength of the upper and lower yokes frame structure.
11) The windings should be axially tight to prevent sideways movements during journey.
12) The active part should be fixed to the tank permanently; the fixing point design intent should comply with
transport loads.
13) To provide additional mechanical support for uncertain rough transport, temporary transport bracing might
be an option for the manufacturers to consider in such circumstances.
14) Extra protection should be applied to all externally mounted devices, such as cabinets, valves, bushings, etc.
to reduce the potential damage during rigging or transportation.

Page 31
6 Specification
The following are proposed as minimum specification requirements for transportation of transformers. The
specification should address these items:
1) Responsibility for the transport (i.e. Incoterms®).
2) Any specific forwarder required (if applicable).
3) Final delivery site and specific place at site.
4) Site of assembly and operation; specific dimensions and conditions for receiving, storage, and assembly of
the transformer.
5) Any local restrictions related to transportation and rigging (if applicable). For instance landing axel loads,
area for transport, bridges, tunnels, loading gauges / -profiles, time restrictions, need for police-escort,
planned events or activities, etc.
6) Any local restriction of maximum allowed dimensions (i.e. height, length, width)
7) Any local restriction of maximum allowed weight of transformer.
8) Transport documentation required.
9) Testing and monitoring prior to, during and after transportation
10) Packaging conditions, especially for accessories and oil (adequate to protect and secure equipment and all
its components from breakage or damage during transit, handling and exposure to climatic conditions)
11) All openings and tube ends are to be transported with watertight seals. The transformer and accessories
should be suitable for outdoor storage.
12) Where components such as bushings and removable radiators are shipped separately, the packaging for
each component should be clearly marked with the purchase order and serial number of the transformer. All
special handling and storage instructions should be clearly marked on each package.
13) Devices to be provided for suitably securement of the transformer (i.e. lashing points etc.).

Page 32
7 Design Review
7.1 Design Review Protocol
The transformer design review should include all aspects of the transformer transportation. The transformer design
review should be conducted in accordance with CIGRE Technical Brochure 529 “Guidelines for Conducting Design
Reviews for Transformers. In addition, the following comprehensive items related to transformer transportation from
this subsequent guide should be used in the design review. A significant contributor to successful transformer
transportation is a review of the (special) design considerations that will allow the transformer to survive a successful
transport between the factory and the location where it will be placed in service.
This chapter in this Guide on Transformer Transportation includes issues to be discussed and analysed during the
Design Review. The items and issues in this Guide on Transformer Transportation are supplementary to CIGRE
Publication 529 “Guidelines for Conducting Design Reviews for Transformers. The design review described in this
chapter contains more detail related to the transportation of a transformer.
7.2 Specifications and Standards
7.2.1 Standards
Transformer specifications include requirements to design, manufacture and supply the transformer in accordance
with IEC 60076 series of standards and/or other national and international standards.
In addition, there are other mandatory or industry recognized practices that must be followed including standards and
regulations mandated by rail, marine or road authorities. These requirements will likely vary widely between various
countries and even sometimes between various jurisdictions and locations within a country.
7.2.2 Specifications
Discuss the use of non-transformer specifications in the design review process, for example, mechanical welding
processes for lifting and jacking related items on the transformer, lifting standards, standards for rigging,
transportation standards in various jurisdictions and locations through which the transformer will travel, etc.
7.2.3 National Requirements
Some countries or continents have regulatory requirements or industry mandated requirements for transporting large
loads including transformers. The specification and design review should consider the national, regional or local
requirements in these various jurisdictions.
7.3 Method of Design Verification
The transformer transport design will only be “tested” during the actual transport of the transformer so the design
must be verified by other means to avoid damage during transport. Generally, transport shock withstands designs
only consider static forces. However, the design reviews should also consider dynamic forces associated with
transportation shocks. Similarly, the issue of vibration must be discussed, especially since much of the damage
observed can be attributed to vibration.
The use of simulation programs should include a discussion of their basis of development and limitations in modelling
both the transformer and the transporter.
Transformer manufacturers develop experience related to the transportation of their specific transformers using
various modes of transport. This experience leads to internal design rules for the transportation related features on
their transformers, i.e. transportation resistant designs. Discuss how company experience is being used to develop
and apply design rules for transportation related design.
Transformer design programs produce dimensional and weight information for the completed transformer in the
transport state. Manufacturing and design tolerances can result in a transformer that may not be exactly as intended.
Discuss the transport dimensional profile and the mass of the transformer will be verified after manufactured. Refer
to chapter 16.2.

Guide on transformer transportation

Guide on transformer transportation

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