Ormazabal transforma.bst-pm Instruction manual

LIB
transforma.bst-pm
Distribution transformers, hermetically
sealed, immersed in dielectric liquid from
16 to 100 kVA (single-phase) / from 25
to 315 kVA (three-phase)
According to IEC 60076 and ENA TS 35-1
General instructions
IG-302-EN, version 01, 18/11/2020

In view of the constant evolution in standards and design, the characteristics of the elements contained in this manual are subject
to change without prior notice. These characteristics, as well as the availability of components, are subject to confirmation by
Ormazabal.
CAUTION!
When medium-voltage equipment is operating, certain components are live, other parts may be in movement and some may
reach high temperatures. Therefore, the use of this equipment poses electrical, mechanical and thermal risks.
In order to ensure an acceptable level of protection for people and property, and in compliance with applicable environmental
recommendations, Ormazabal designs and manufactures its products according to the principle of integrated safety, based on
the following criteria:
• Elimination of hazards wherever possible.
• Where elimination of hazards is neither technically nor economically feasible, appropriate protection functions are
incorporated in the equipment.
• Communication about remaining risks to facilitate the design of operating procedures which prevent such risks,
training for the personnel in charge of the equipment, and the use of suitable personal protective equipment.
• Use of recyclable materials and establishment of procedures for the disposal of equipment and components so
that once the end of their service lives is reached, they are duly processed in accordance, as far as possible, with the
environmental restrictions established by the competent authorities.
Consequently, the equipment to which the present manual refers complies with the requirements of section 11.2 of Standard
IEC 62271-1. It must therefore only be operated by appropriately qualified and supervised personnel, in accordance with the
requirements of standard EN 50110-1 on the safety of electrical installations and standard EN 50110-2 on activities in or near
electrical installations. Personnel must be fully familiar with the instructions and warnings contained in this manual and in other
recommendations of a more general nature which are applicable to the situation according to current legislation[1].
The above must be carefully observed, as the correct and safe operation of this equipment depends not only on its design but also
on general circumstances which are in general beyond the control and responsibility of the manufacturer. More specifically:
• The equipment must be handled and transported appropriately from the factory to the place of installation.
• All intermediate storage should occur in conditions which do not alter or damage the characteristics of the equipment
or its essential components.
• Service conditions must be compatible with the equipment rating.
• The equipment must be operated strictly in accordance with the instructions given in the manual, and the applicable
operating and safety principles must be clearly understood.
• Maintenance should be performed properly, taking into account the actual service and environmental conditions in
the place of installation.
The manufacturer declines all liability for any significant indirect damages resulting from violation of the guarantee, under any
jurisdiction, including loss of income, stoppages and costs resulting from repair or replacement of parts.
Warranty
The manufacturer guarantees this product against any defect in materials and operation during the contractual period. In the
event that defects are detected, the manufacturer may opt either to repair or replace the equipment. Improper handling of this
equipment and its repair by the user shall constitute a violation of the guarantee.
Registered Trademarks and Copyrights
All registered trademarks cited in this document are the property of their respective owners. The intellectual property of this manual
belongs to Ormazabal.
[1] For example, Electricity at work regulations 1989, Local High Voltage safety rules.

IG-302-EN version 01; 18/11/2020 3
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
Table of Contents
In view of the constant evolution in standards and design, the characteristics of the elements contained in this manual are subject
to change without prior notice. These characteristics, as well as the availability of components, are subject to confirmation by
Ormazabal.
CAUTION!
When medium-voltage equipment is operating, certain components are live, other parts may be in movement and some may
reach high temperatures. Therefore, the use of this equipment poses electrical, mechanical and thermal risks.
In order to ensure an acceptable level of protection for people and property, and in compliance with applicable environmental
recommendations, Ormazabal designs and manufactures its products according to the principle of integrated safety, based on
the following criteria:
• Elimination of hazards wherever possible.
• Where elimination of hazards is neither technically nor economically feasible, appropriate protection functions are
incorporated in the equipment.
• Communication about remaining risks to facilitate the design of operating procedures which prevent such risks,
training for the personnel in charge of the equipment, and the use of suitable personal protective equipment.
• Use of recyclable materials and establishment of procedures for the disposal of equipment and components so
that once the end of their service lives is reached, they are duly processed in accordance, as far as possible, with the
environmental restrictions established by the competent authorities.
Consequently, the equipment to which the present manual refers complies with the requirements of section 11.2 of Standard
IEC 62271-1. It must therefore only be operated by appropriately qualified and supervised personnel, in accordance with the
requirements of standard EN 50110-1 on the safety of electrical installations and standard EN 50110-2 on activities in or near
electrical installations. Personnel must be fully familiar with the instructions and warnings contained in this manual and in other
recommendations of a more general nature which are applicable to the situation according to current legislation[1].
The above must be carefully observed, as the correct and safe operation of this equipment depends not only on its design but also
on general circumstances which are in general beyond the control and responsibility of the manufacturer. More specifically:
• The equipment must be handled and transported appropriately from the factory to the place of installation.
• All intermediate storage should occur in conditions which do not alter or damage the characteristics of the equipment
or its essential components.
• Service conditions must be compatible with the equipment rating.
• The equipment must be operated strictly in accordance with the instructions given in the manual, and the applicable
operating and safety principles must be clearly understood.
• Maintenance should be performed properly, taking into account the actual service and environmental conditions in
the place of installation.
The manufacturer declines all liability for any significant indirect damages resulting from violation of the guarantee, under any
jurisdiction, including loss of income, stoppages and costs resulting from repair or replacement of parts.
Warranty
The manufacturer guarantees this product against any defect in materials and operation during the contractual period. In the
event that defects are detected, the manufacturer may opt either to repair or replace the equipment. Improper handling of this
equipment and its repair by the user shall constitute a violation of the guarantee.
Registered Trademarks and Copyrights
All registered trademarks cited in this document are the property of their respective owners. The intellectual property of this manual
belongs to Ormazabal.
[1] For example, Electricity at work regulations 1989, Local High Voltage safety rules.
Table of Contents
1. Description and main characteristics.......................4
1.1. Design, manufacturing and testing ...........4
1.1.1. Individual or routine tests ....................5
1.1.2. Test protocol.................................5
2. Lifting, moving and handling ...................................6
2.1. Lifting and moving with a forklift truck .......6
2.2. Lifting and moving by crane..................7
3. Transport ....................................................................8
3.1. Preparing the load for transport ..............8
3.2. Transport agents............................10
3.3. Selecting the route for road transport .......10
3.4. Checking impact detectors..................11
3.5. Responsibility...............................11
4. Storage......................................................................12
5. Installation ...............................................................13
5.1. Receiving the transformer...................13
5.2. Transformer electrical connections ..........14
5.2.1. Standard procedure.........................14
6. Commissioning ........................................................16
6.1. Checking the transformer before
commissioning .............................16
6.1.1. Mineral oil insulated transformers ...........16
6.1.2. Natural ester transformers...................17
7. Maintenance.............................................................18
7.1. Access for maintenance operations ..........18
7.2. Checking the transformer ...................19
7.2.1. Transformer temperature....................19
7.2.2. Inspecting oil volume .......................19
7.2.3. Noise .......................................19
7.2.4. Tightening bolts and threaded pieces .......19
7.2.5. Oil leaks ....................................19
7.2.6. Paint........................................19
7.3. Regularity of maintenance ..................21
7.4. Repairs .....................................22
8. Additional information............................................23
8.1. Reliability ...................................23
8.2. Company registration certificate.............23
9. Final annex ...............................................................24

IG-302-EN version 01; 18/11/2020
4
Description and main characteristics
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
1. Description and main characteristics
1.1. Design, manufacturing and testing
[2] Medium-voltage electrotechnical regulations applicable when the transformer was manufactured.
Ormazabal's transformers have been designed and
constructed in accordance with mandatory standards, and
meet all testing requirements in current medium-voltage
electrotechnical regulations[2], as well as particular customer
specications.
More specically, apart from the hermetically sealed, mineral
oil-immersed transformers, the “type K” transformer range
is characterised by its use of natural or synthetic esters as a
dielectric liquid, with the following general characteristics:
• Excellent dielectric properties, with a high water
saturation point, which allows it to maintain high
dielectric strength values with a high water content.
• High re resistance: natural or synthetic ester is classied
as a K class liquid (re point above 300°C).
• High biodegradability in ground and water due to its
natural composition.
• It is not ecotoxic.
• Recyclable and reusable in other favourable environ-
mental products at the end of its service life.
1Medium-voltage (MV) bushings
2Low-voltage (LV) bushings
3Ferromagnetic core
4MV and LV windings
5Fixing holes
6Enclosure and dielectric liquid
7Lifting eye bolts
8Name plate
9Purging and sample collector device
10 Filling device
11 Tap changer
12 Overpressure valve
13 Earthing terminal
Figure 1.1. transforma elements detail

IG-302-EN version 01; 18/11/2020 5
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
Description and main characteristics
1.1.1. Individual or routine tests
The transformers are subjected to routine tests, which
guarantee compliance with the following standards:
IEC 60076-1 Winding resistance measurement
IEC 60076-1 Transformation ratio measurement and check up of vector group
IEC 60076-1 Measurement of load losses and short-circuit voltage at main tapping
IEC 60076-1 Losses and no-load current measurement
IEC 60076-1 Leak testing with pressure
IEC 60076-3 Power frequency voltage test
IEC 60076-3 Induced voltage test
Table 1.1. Standards
1.1.2. Test protocol
All the information regarding the transformer tests
is recorded in the "Test Protocol" enclosed with the
transformer documentation.

IG-302-EN version 01; 18/11/2020
6
Lifting, moving and handling
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
2. Lifting, moving and handling
The lifting elements must be selected based on the
transformer's total weight, as shown on the name
plate.
To enable lifting and transport, each transformer is tted
with fastening and lifting elements on the top side of the
tank.
There are attachment points and xing holes in the bottom
of the transformer (mounting feet and back) in order to
secure it during transport.
NEVER force the cooling elements (ns, radiators, etc.)
when lifting, moving or xing the transformer to the
transport base. The xing, moving and lifting elements
(bracing, etc.) must be able to withstand the entire
force of these operations.
Transformers must always be lifted, transported and
handled using suitable, certied equipment.
All lifting, transport and handling equipment must be duly
selected and used by the handler in accordance with the
characteristics of the machine.
Ormazabal shall not be liable for any improper choice or
use.
2.1. Lifting and moving with a forklift truck
In this case, the transformer must only be lifted and moved
when tted and fastened to a pallet adequate to handle
its weight and size, making sure the cooling elements and
insulators are protected against any accidental damage.
Figure 2.1. Transport using a forklift truck

IG-302-EN version 01; 18/11/2020 7
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
Lifting, moving and handling
2.2. Lifting and moving by crane
When lifting and moving the transformer with a crane, it
must be remembered that the lifting elements allow the
transformer to be completely suspended. These elements
are the lifting lugs, which are tted in the cover of the tank
and identied for this purpose. The following indications
must be taken into account when lifting the transformer:
• Use the lifting lugs in the cover of the transformer
tank to lift the transformer with a crane, maintaining a
horizontal position at all times.
• Two or four eye bolts are optionally tted in the cover. In
the case of transformers with four eye bolts, four lifting
hooks must be used at the same time. In the case of
transformers with two eye bolts, the two hooks must be
used with appropriate equipment.
• Use proper hooks to achieve correct vertical elevation.
• The slings on the eye bolts must form a minimum angle
of 60° with the transformer’s horizontal.
• The slings must not rub or damage the bushings or
other accessories.
Risk of death by crushing and damage to the
transformer or to the installation.
• NEVER use transformer cooling elements such as ns
or radiators as lifting elements. RISK of severe injury
and damage to the transformer.
Figure 2.2. Forbidden lifting points
Figure 2.3. Preparing the crane hook in the lifting lugs
Figure 2.4. Lifting a transformer using a crane

IG-302-EN version 01; 18/11/2020
8
Transport
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
3. Transport
Despite the robust design and construction of the
transformers manufactured by Ormazabal, their integrity
depends critically on the safety and protection measures
taken during transport and unloading. The transformer may
be severely damaged in these operations if any impacts,
vibrations or shocks above normal for goods with such
dimensions and weight occur.
3.1. Preparing the load for transport
The transformer must be lifted using slings, chains and
other elements suitable for the weight of the transformer,
as shown on its name plate.
The protection tools and equipment provided or
recommended by Ormazabal (according to the agreement
with the customer), such as anti-vibration brackets and
elements for pulling (bracing) or securing the load, must be
used for transport.
The transformer has specially designed lashing/fastening
elements to secure it during transport/handling operations.
• Fastening elements: the transformer xing holes are
used for bracing or lashing during transport (Figure 3.5).
Figure 3.5. Fastening elements

IG-302-EN version 01; 18/11/2020 9
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
Transport
• When securing the transformer, be sure that the lashing
or fastening chains do not interfere with any of the
transformer's accessories or cooling elements.
• The fastening straps are attached to the container's
fastening elements on both sides of the transformer,
producing a symmetrical tension which is oset on both
sides.
• The connecting rods of the cooling elements must not
be used as lashing points for transport, or for any other
similar function (see Figure 3.6).
Figure 3.6. NEVER use cooling elements as fastenings for transport

IG-302-EN version 01; 18/11/2020
10
Transport
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
3.2. Transport agents
All agents, companies and personnel involved in
transporting and handling the transformer must
demonstrate preparation, training, procedures and
experience in the transport of heavy equipment and
equipment susceptible to damage due to violent transport
conditions, and must count on suitable accreditations and
certicates in order to drive the means of transport used.
3.3. Selecting the route for road transport
The route chosen for road haulage must be the one with
the best conditions for transporting heavy loads which are
sensitive to damage from impacts, bangs, vibrations and
accelerations.
Routes that reduce the eects of accelerations, vibrations,
impacts and bangs caused by winding roads, changes of
gradient and the cant of the road should take precedence
over shortest distance.
As far as possible, priority should be given to the highest
category of motorways with minimum slope, maximum
linearity and best road surface condition.
The transformers are prepared for transport on at, paved
roads without signicant potholes.
As a general rule, a "pothole" is understood as any deciency
in the terrain greater than 200 mm, whenever the terrain
has angles of attack of less than 30° (i.e. no abrupt changes).
On uneven road sections, transport speed should be
reduced in order to ensure the load does not suer sudden
acceleration and deceleration.
Trac and transport rules in the corresponding
country must be respected in all cases.
If transport for the transformer is to include road
surfaces that are not asphalted, the customer must
indicate this circumstance in the order sent to
Ormazabal. Following this communication, the best
solution for transport will be decided between the
customer and Ormazabal.

IG-302-EN version 01; 18/11/2020 11
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
Transport
3.4. Checking impact detectors
Ormazabal reserves the right to t impact detectors (or ask
for them to be tted) in its transformers in order to provide
evidence of events that may cause damage to the machine
during transport.
In accordance with Standard IEC 60076-1, section 5.7.4.2
Acceleration during transport, the transformers referred
to in this manual are designed and built to withstand
accelerations of at least 1 g in all directions (apart from
gravity acceleration in vertical direction) without any
damage.
If transport is not managed by Ormazabal, or is not carried
out under its responsibility, and accelerations in excess
of 1 g are expected during transport, all accelerations
and frequencies must be dened in the order, and the
transformer must be designed in accordance with these
values.
Ormazabal shall not be liable for any damage during
transport whenever there is evidence of transport
conditions that exceed the values dened in the standard
or those specied when requesting the oer and/or order
for the product.
3.5. Responsibility
Whenever the conditions described in this document are
not met, Ormazabal reserves the right to reject liability for
any damage caused to its product while transporting and
handling.

IG-302-EN version 01; 18/11/2020
12
Storage
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
4. Storage
If commissioning is not immediate, transformers must be
stored following the recommendations below:
• Store the transformer in a place that is dry and clean.
• If the transformer is equipped with plug-in terminals,
make sure the conical protector or cap provided for
keeping the connection terminals clean and intact is in
place.
Due to the particular characteristics of natural esters
at low temperatures, it is best to avoid storing these
transformers at temperatures below -5°C. It is therefore
recommended to store indoors.

IG-302-EN version 01; 18/11/2020 13
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
Installation
5. Installation
Ormazabal is not responsible for transformer insta-
llation, which must be carried out in accordance with
applicable legislation.
5.1. Receiving the transformer
The transformer is supplied ready for connection to the grid.
Some elements, such as the rollers and/or the thermometer,
may be supplied unassembled for shipping.
When the transformer is received (at the customer's
warehouse or at the transformer’s nal location), it must
be carefully inspected, paying special attention to the
following aspects:
• The transformer ratings, as indicated on its name plate,
must match those in the "Test Protocol", and these, in
turn, must match those specied in the associated order.
• Check the general state of the transformer and ensure
the absence of any impacts, in particular in the cooling
equipment and in the insulators or terminals. If the
transformer has paint defects, it must be corrected in
accordance with the procedure set out in section “7.2.
Checking the transformer” - “7.2.6. Paint”.
• Verify that the transformer has all of its accessories
(rollers, thermometer, etc.), ensuring they are not
damaged.
Notify the transport agent and Ormazabal imme-
diately if any accessory is missing or damaged.
• The transformer seals must be unbroken and untouched.
• There should be no evidence of dielectric leakage.
Figure 5.1. Transformer seal detail
Tampering with or breaking a seal voids the transformer
warranty as well as Ormazabal's liability.
Notify Ormazabal immediately if any anomaly is
detected upon the receipt of the transformer. If, after
a 15 day period, the manufacturer has not received
a report of anomalies or defects found, it is assumed
that the transformer arrived in a perfect condition
and Ormazabal will not be responsible for any future
anomalies or their consequences.

IG-302-EN version 01; 18/11/2020
14
Installation
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
5.2. Transformer electrical connections
5.2.1. Standard procedure
Risk of death by electric shock and of irreversible
damage to the transformer or to the electrical
installation.
• The transformer's electrical connections can only be
made by qualied personnel while always observing
proper electrical safety measures.
The steps to follow to complete the electrical transformer
connection are as follows:
1. Check that the electrical power supply to the
transformer matches the service values shown on the
transformer’s name plate.
Risk of causing irreversible damage to the
transformer or to the electrical installation.
• Verifythatthe electricpowersupply to the transformer
meets the service values shown on the transformer’s
name plate.
2. Open all the electrical power sources and interlock or
block the necessary breaking devices to prevent any
power supply.
3. Check that electrical voltage is not present.
4. Earth and short-circuit all the electrical power sources.
5. Delimit and mark the work area properly.
6. Check for correct dielectric liquid level.
Contact Ormazabal in the event of dielectric liquid
leaks.
Start the electrical connection by earthing the
transformer tank.
7. Earth the transformer using the earthing lug indicated
in Figure 5.2 using the designated cross section earthing
cable and lug. Secure with an M12 bolt and washers
(stainless steel recommended). Tighten to 40-60 Nm.
Tools:
• Standard cross-section earthing cable.
• Round terminals of suitable diameter.
• One M12 bolt and nuts.
• Two 12 mm washers (one for each side of the
connection terminal).
8. Connect the transformer to the medium-voltage
circuit. To avoid any leaks, use exible connections that
do not place any strain on the transformer bushings,
suciently sized to prevent excessive overheating
and, at the same time, allow heat expansion without
damaging the transformer.
The tightening torques must guarantee the proper
electric contact of the connections.

IG-302-EN version 01; 18/11/2020 15
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
Installation
9. Connect the transformer to the secondary circuit using
exible connections which do not place any strain on
the transformer bushings, suciently sized to prevent
excessive overheating and, at the same time, allow
the expansion caused by heat without damaging the
transformer.
The tightening torques must guarantee the proper
electric contact of the connections.
10. Connect the transformer’s neutral to the electrical
installation’s neutral (where appropriate).
11. Check that the tap changer position is correct; and,
in the case of a multi-voltage transformer, ensure the
medium-voltage or primary circuit is connected to the
electrical voltage that is going to be used as service
voltage.
Figure 5.2. Transformer earth connection detail

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16
Commissioning
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
6. Commissioning
6.1. Checking the transformer before commissioning
6.1.1. Mineral oil insulated transformers
Once the transformer is connected to the power networks,
and before connecting the electrical power source, the
following checks should be performed:
1. Check that the network values and the transformer's
rated voltage match.
2. If the transformer has these instruments, check the
correct oil level in the oil level indicator, if tted.
3. Energise the transformer with no load connected
and check its correct connection and regulation by
measuring the values in the secondary.
Failure to follow these safety precautions may
result in death by electric shock or irreversible
damage to the transformer or to the electrical
installation.
• The tap changers should always be operated without
electrical power, ensuring the handle is well locked
and in its working position.
• Check that the electrical voltage applied matches the
transformer's rated voltage. Contact Ormazabal in
the case of any anomaly.
• If an adjustment is required after commissioning the
transformer, follow the safety instructions specied
in section 7.1 of these general instructions, titled
“Access for maintenance operations”.
4. Regulate the transformer's voltage using the corres-
ponding tap changer, taking into account the safety
precautions.
Figure 6.1. Tap changer in transformer detail
a. If the transformer has a no-load tap changer:
i. The no-load voltage tap changers must always
be operated without electrical power, ensuring
the handle is well locked and in its working
position.
ii. Check that the electrical voltage applied
matches the transformer's rated voltage. Contact
Ormazabal in the case of any anomaly.
iii. If an adjustment is required after commissioning
the transformer, follow the safety instructions
specified in section 7.1 of these general
instructions.
5. Keep the transformer energised with no-load for at
least 12 hours, checking that there are no anomalies in
any of the transformer instruments.
6. Progressively apply the load until operating power is
achieved, while ensuring that transformer temperature
does not go over 105°C. In the case of transformers for
renewable energy sources, connect to the generation
source in low generation conditions and let it increase
naturally.

IG-302-EN version 01; 18/11/2020 17
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
Commissioning
6.1.2. Natural ester transformers
Natural esters have higher freezing points than those
of mineral oil. The liquid could therefore freeze during
prolonged exposure to temperatures below -10°C.
In these cases, Ormazabal recommends the following
actions to ensure correct commissioning:
1. Temp ≥ -10°C, same considerations as mentioned in
point 6.1.1.
2. Temp ≤ -10 °C or recently reached, there are two
options:
a. Maintain without load, for at least 12 hours in order
to heat the ester and decrease its viscosity. Then
carry out the same operations as mentioned in
point 6.1.1.
b. Move the transformer indoors for at least 24 h, to
allow the ester to heat up and decrease its viscosity.
Then carry out the same operations as mentioned
in point 6.1.1.
It may not be possible to determine the exact temperature
reached when storing or transporting the transformer, or
the ester may still be at a temperature below -10 °C while
the outside temperature is higher, due to the thermal
inertia of the ester. In order to guarantee the integrity of the
transformer, Ormazabal therefore recommends following
one of the two previous options before handling the o-
load tap changer when the outside temperature is below
-5°C.
Risk of death caused by electric shock and of
irreversible damage to the transformer or to the
electrical installation.
• Carefully follow the instructions in section “7.1.
Access for maintenance operations” before handling
the facility.
• Do not operate the tap changer with electrical power
applied to the transformer.

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18
Maintenance
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
7. Maintenance
7.1. Access for maintenance operations
Before performing any maintenance operation on the
transformer, follow the measures required by applicable
legislation, including:
1. Disconnect all the electrical power sources for the
circuits until the transformer is turned o, interlocking
or blocking the necessary breaking devices to prevent
any power supply.
2. Check that electrical voltage is not present.
3. Earth and short-circuit all the electrical power sources.
4. Using an insulating stick, earth the transformer bushings
and ensure that any static electricity is discharged.
5. Delimit and mark the work area properly.
6. Check that the transformer does not leak dielectric
liquid.
Risk of causing irreversible damage to the
transformer or to the electrical installation.
• Contact Ormazabal in the event of dielectric liquid
leaks.

IG-302-EN version 01; 18/11/2020 19
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
Maintenance
7.2. Checking the transformer
7.2.1. Transformer temperature
The working temperature of the transformer is directly
related to the service life of the insulating materials. It is
therefore necessary to monitor or control the maximum
temperature values recorded by the instrumentation.
In case the transformer had thermometer with calibrated
protection elements that give out an alarm/trip signal
whenever the appropriate work temperature is exceeded,
they have to be properly set.
7.2.2. Inspecting oil volume
The oil volume must be checked from the point of view of
insulation and cooling. If the oil level uctuates signicantly
relative to the transformer working temperature, the cause
must be determined before proceeding with repair.
7.2.3. Noise
If strange noises are heard to come from the transformer,
contact Ormazabal and report the circumstances, so we
can determine the cause.
7.2.4. Tightening bolts and threaded pieces
Whenever it is detected that the tank's earthing terminals
are loose, de-energise the transformer in line with the
instructions in section 6.1 and tighten them immediately.
7.2.5. Oil leaks
Leakage may occur in dielectric liquid transformers,
although this is not normally the case. If a leak is detected
in the transformer, contact Ormazabal immediately,
providing as much information as possible (including
photographs of the leak) in order to nd a quick solution.
7.2.6. Paint
The transformers may show damage in the surface nish
due to impacts or as a result of handling and transport.
These defects in the paint may also show localised rusting.
Report any damaged paint to Ormazabal, sending photos
and a description of the damage in order to dene the best
actions to solve the problem.
Below are some instructions on how to repair the aected
areas:

IG-302-EN version 01; 18/11/2020
20
Maintenance
General instructions
transforma.bst-pm: Distribution transformers, hermetically
sealed, immersed in dielectric liquid from 16 to 100 kVA
(single-phase) / from 25 to 315 kVA (three-phase)
Instructions for retouching paint
The procedure for repairing damaged paint is as follows:
1. Sanding the aected area
Remove the rust using sandpaper or a suitable scraper,
until the metal is shiny.
2. Applying primer
Spray the aected area with a coat of paint which is rich
in anti-corrosive pigments of aluminium-zinc or similar.
Ensure that this paint covers the whole area. Shake
vigorously before applying the spray.
After applying the primer, allow the area to dry for at
least 15 minutes or for the time and under the conditions
recommended by the spray paint manufacturer
(whichever is longer).
Figure 7.2. Spray primer
3. Applying nish paint
Spray on the dry primer, using the same colour as the
paint nish, covering the area. Excess paint is removed
with a damp cloth.
Please contact Ormazabal to determine the exact
colour of the spray paint.
Figure 7.3. Spray primer