Ormazabal velatia transforma.earth Instruction manual

transforma.earth
General instructions
IG-286-EN, version 01; 11/07/2019
Three-Phase earthing transformers
up to 36 kV
LIB

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 protection 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 the IEC standard 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.
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 warranty, 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 the
manufacturer.
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 notification.
These characteristics, as well as the availability of components, are subject to confirmation by Ormazabal.

3
IndexGeneral instructions
transforma.earth
IG-286-EN version 01
INDEX
1 Description and general features. . . . . . . . . . . 4
1.1 Design, manufacture, and testing . . . . . . . . . . . . . . . .4
1.1.1 Standard or routine testing . . . . . . . . . . . . . . . . . . . . . .4
1.1.2 Testing protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4
2 Transport and handling . . . . . . . . . . . . . . . . . . . 5
2.1 Forklift transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
2.2 Crane transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5
2.3 Wheel transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6
2.4 Transport by road and/or shipping by sea . . . . . . . .6
2.5 Preparing the load for transport . . . . . . . . . . . . . . . . .6
2.6 Transporters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
2.7 Route selection for road transport . . . . . . . . . . . . . . .7
2.8 Checking the impact recorders . . . . . . . . . . . . . . . . . .7
2.9 Responsibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7
3 Storage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1 Reception of the earthing transformer . . . . . . . . . . .9
4.2 Installing the earthing transformer . . . . . . . . . . . . . . .9
4.3 Earthing transformer electrical connections . . . . 10
4.3.1 Standard procedures . . . . . . . . . . . . . . . . . . . . . . . . . . 10
5 Setup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1 Check the earthing transformer before
placing it in service . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6 Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1 Access for maintenance operations . . . . . . . . . . . . 14
6.2 Periodic maintenance . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.3 Repairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
7 Additional information . . . . . . . . . . . . . . . . . . . 17
7.1 Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.2 Business registration certificate . . . . . . . . . . . . . . . . 17
8 Attachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4 Description and general features General instructions
transforma.earth
IG-286-EN version 01
1 DESCRIPTION AND GENERAL FEATURES
1.1 Design, manufacture, and testing
The earthing transformers manufactured by Ormazabal have
been designed and manufactured to meet mandatory standards
and testing regulations according to Medium Voltage (MV)
Electrotechnical Regulations in force at the time of its
manufacture, as well as specific customer specifications.
1Expansion tank 9Connection box
2Oil level 10 Silica gel dehydrator
3MV neutral terminal 11 Buchholz relay
4MV phase terminals 12 Thermometer
5Overpressure valve 13 Core and flange terminals
6Upper filtering valve 14 Vacuum and lower filtering valve
7Autovalves 15 Sampling valves
8Current transformers connection boxes
Fig. 1.1: Detail of the transforma.earth components
1.1.1 Standard or routine testing
Earthing transformers are subjected to routine testing that
guarantees compliance with the following standards:
►Measurement of winding resistance:
IEC 60076-1
►Measurement of current vacuum loss:
IEC 60076-1
►Measurement of earthing fault impedance:
IEC 60076-1
►Electrical voltage applied at a power frequency test:
IEC 60076-3
►Induced electrical voltage test:
IEC 60076-3
If the earthing transformer has a secondary function as an
auxiliary services transformer, the following routine tests are
also performed:
►Measurement of the transformation relation and
verification of the connection group.
IEC 60076-1
►Measurement of the short circuit impedance and load
loss IEC 60076-1
►Voltage applied to auxiliary winding test
IEC 60076-3
For other standards, consult Ormazabal.
1.1.2 Testing protocol
All information related to testing to which the earthing
transformer has been submitted to is covered
in the "Testing Protocol", that accompanies the
documentation supplied together with the same.

5
Transport and handlingGeneral instructions
transforma.earth
IG-286-EN version 01
2 TRANSPORT AND HANDLING
To facilitate its transport, each earthing transformer has
bracing elements on the four upper corners of the tank for its
transport, to avoid the refrigeration elements from being
damaged.
Earthing transformer can be transported and handled using a
forklift, crane, or wheels.
2.1 Forklift transport
For transporting the earthing transformer by forklift, it should
be mounted on a special pallet suitable for its mass and
dimensions, as well as appropriately anchored to it, protecting
the refrigeration elements against possible damage caused by
the forklift support.
Fig. 2.1: Detail of forklift transport
2.2 Crane transport
For transporting the earthing transformer by crane, take into
consideration that the tank allows total suspension of the
same, by means of the built-in lifting eye bolts. Complete
suspension of the earthing transformer should be performed
taking the following specifications into consideration:
►Slings on the eye bolts should form an angle greater
than or equal to 60º to the horizon of the earthing
transformer.
►Slings should not rub nor damage the bushings or any
other of the earthing transformer accessories.
Fig. 2.2: Detail of crane lifting
CAUTION
Risk of machine breakage
►In order to determine the appropriate lifting method for the
earthing transformer, the total weight must be taken into
consideration, which is indicated on its rating plate.
DANGER
Risk of death by crushing and from damage to the
earthing transformer or to the installation
►Use the eye bolts on the cover of the earthing transformer to lift it
by crane, keeping it in a horizontal position at all times.
►If the weight of the earthing transformer requires that the lifting
eye hooks be located on the tank, they will be properly identified
with a different color.
►To avoid damage to the elements located on the earthing
transformer’s cover, use suitable hooks to obtain a perfectly
vertical lifting.
►Never use the earthing transformer refrigeration elements, such
as the fins and radiators, as lifting elements for the same. Risk of
severe damage to people and the machine.

6 Transport and handling General instructions
transforma.earth
IG-286-EN version 01
2.3 Wheel transport
To move the earthing transformer by means of the built-in
wheels, use a lever, supporting the earthing transformer
carriage.
2.4 Transport by road and/or shipping by
sea
Despite the robust design and construction of Ormazabal
earthing transformer, their integrity depends critically on the
safety and protection measures used during transport and
unloading. The transformer can be severely damaged during
these operations if greater than normal shaking, vibrations,
impacts, or blows occur for merchandise of such size and
weight.
2.5 Preparing the load for transport
The transformer should be attached by means of slings, chains,
and other elements suitable for the mass stated on the
transformer's name plate.
For transport, tools and other means of protection provided or
recommended by Ormazabal should be used (according to
buyer agreement) such as anti vibration support.
For fastening the transformer during transport/handling
operations, secure tie-down down elements are provided,
devised expressly for this purpose.
►Upper tie-down elements: there are four elements
that are provided as shown in Figure 2.3 or as in Figure
2.4.
Fig. 2.3: Upper transport tie-down (Type 1)
Fig. 2.4: Upper transport tie-down (Type 2)
CAUTION
Risks of damage to the machine
►Do not use the earthing transformer refrigeration fins as support
points.

7
Transport and handlingGeneral instructions
transforma.earth
IG-286-EN version 01
►Lower tie-down elements: there are four and they are
found at the base of the transformer (Figure 2.5)
Fig. 2.5: Lower transport tie-down
►When tying the transformer down, pay attention that
the securing strap does not interfere at any time with
any of the transformer's refrigeration elements or
accessories.
►The tie down straps should be attached to the
containers’ fastening elements on both sides of the
transformer so that they produce symmetrical tension
that is counterbalanced on both sides.
►Do not use the connecting rods on the refrigeration
elements as securing points for transport, or for any
other similar purpose (Figure 2.6).
►Some accessories may be removed and attached as
additional packages for transport.
Fig. 2.6: Do not use the connecting rods on the refrigeration
elements as securing points or for similar purposes
2.6 Transporters
The agents, companies, and personnel involved in the task of
transporting and handling the earthing transformer must
demonstrate preparation, training, procedures, and
experience with transporting heavy equipment and with
equipment that is sensitive to damage from violent transport
events.
2.7 Route selection for road transport
Route selection for road transport must be done so that the
road selected is the one that demonstrates the best conditions
for transporting heavy loads sensitive to damage from impact,
shaking, vibrations, and accelerations.
A route that reduce the effects of accelerations, vibrations,
impacts, and shaking caused by sinuosity, changes in slope, or
the state of the road's cant must take precedence over the
shortest distance.
Routes should be avoided where there is construction or that
have slopes and priority should be given as far as possible for
higher grade interstates that have the least amount of slope,
maximum linearity, and better road conditions.
2.8 Checking the impact recorders
Ormazabal reserves the right to accommodate impact
recorders or detectors in its transformers, which reveal events
during transport that can cause damage to the machine.
Acceleration values greater than those shown in the following
Table 2.1 are unacceptable, as taken from IEEE Standard
C57.93-2007:
Tab. 2.1: Recommended acceleration value limits from
IEEE Standard C57.93-2007
2.9 Responsibility
Ormazabal reserves the right to not be responsible for
damages caused from the transport and handling of its
product when the conditions described in this document are
not met.
Type of Impact Level Limits
Longitudinal 3g
Vertical 2g
Transversal 2g

8 Storage General instructions
transforma.earth
IG-286-EN version 01
3 STORAGE
If storing the earthing transformer (for example, if it will not be
put into service immediately), the following recommendations
should be followed:
►Store the earthing transformer in a clean and dry place.
►If the earthing transformer is equipped with plug-in
terminals, make sure that the conical protector
provided with the earthing transformer is protected, to
keep the connection terminals in good and clean
condition.

9
InstallationGeneral instructions
transforma.earth
IG-286-EN version 01
4 INSTALLATION
4.1 Reception of the earthing transformer
transforma.earth is supplied prepared for connection to medium
voltage (MV) and low voltage (LV) lines.
Upon receiving the earthing transformer (in the customer's
warehouse or in its final location place), it should be carefully
examined, paying special attention to the following aspects:
►The specifications of the earthing transformer
indicated on its «Name Plate» should match those on
the «Test Protocol», and these, in turn, with that
specified in the corresponding request order.
►Verify the general condition of the earthing
transformer and check that there are no dents,
especially on the refrigeration equipment and on the
medium voltage (MV) and low voltage (LV) insulator
bushings, if it has secondary winding.
►Verify that the earthing transformer includes all its
accessories (wheels, thermometer, etc.) checking that
these accessories are not damaged.
►Some accessories, like the silica gel dehydrator, the
wheels and/or the thermometer, can be removed for
transport. Other accessories, like the Buchholz relay or
the overpressure relay relief valve, can be locked to
avoid their activation during transport. In both cases, it
is important to install them and/or unlock them before
they are put into service.
In the event any accessories are lost or missing, as well
as if they are damaged, immediately notify the shipper
or Ormazabal.
►The earthing transformer seals should be intact and
should not have been tampered with.
IG168-005
Fig. 4.1: Detail of the earthing transformer seal
4.2 Installing the earthing transformer
The placement location for the earthing transformer, for
exterior as well as interior installation, should allow for
adequate cooling.
The conditions of the placement location for the earthing
transformer and its design, for both technical reasons as well as
for the protection and safety of people and property, are defined
in legislation regulations in force specific to the installation area,
as well as specific standards related to the installation area.
If the earthing transformer is to be installed inside, a horizontal
base should be prepared that supports it, keeping in mind its
total weight as indicated on its «Name Plate».
The wheels on the earthing transformer must be immobilized
to avoid them from moving during its operation.
Tampering with or breaking a seal voids the warranty
on the earthing transformer and Ormazabal’s
responsibility.
If an anomaly is detected upon receiving the earthing
transformer, contact Ormazabal immediately. If,
within a period of 15 days, Ormazabal has not
received a report of any anomalies or defects found, it
is understood that the earthing transformer has
arrived at its destination in perfect condition, and
Ormazabal shall not be responsible for subsequent
anomalies and their consequences.
Poor ventilation of the earthing transformer may
cause unsuitable overheating of the same.

10 Installation General instructions
transforma.earth
IG-286-EN version 01
4.3 Earthing transformer electrical
connections
4.3.1 Standard procedures
The steps to follow when performing the electrical connection
for the earthing transformer are as follows:
1) Verify that the electrical connection network for the
earthing transformer matches the service values
indicated on the earthing transformer’s name plate.
2) Open all sources of electrical voltage, interlocking or
blocking the necessary cutting devices, to avoid any
possible feedback.
3) Verify there is no electrical voltage.
4) Connect to earth and short-circuit all sources of
electrical voltage.
5) Restrict and properly indicate the working area.
6) Check that there is the correct level of dielectric fluid.
7) Earth the earthing transformer’s tank, earthing its
built-in connections by means of the round
connection terminals using regulatory gauge
grounding cable.
Tools:
►Regulation gauge earthing connection cable.
►Proper diameter round terminals.
►1 M12 screw (M10, on request).
►2 14-mm washers (one for each side of the
connection terminal) (12 mm for M10)
Use a 40-60 Nm tightening torque for M12 (25-35 Nm
for M10).
Fig. 4.2: Detail of the transforma.earth earthing connection
DANGER
Risk of death due to electrocution and irreversible
damage to the machine or the electrical system
►Electrical connection operations for the earthing transformer can
only be performed by certified technical personnel, and always
by those familiar with appropriate electrical safety measures.
CAUTION
Risk of irreversible damage to the machine or the
electrical system.
►The electrical connection network for the earthing transformer
should match the service values indicated on the earthing
transformer’s name plate.
CAUTION
Risk of irreversible damage to the machine or the
electrical system.
►In case of a dielectric fluid leak, contact Ormazabal.
CAUTION
Risk of irreversible damage to the machine or the
electrical system.
►The first electrical connection performed for the earthing
transformer should be to earth the tank.
CAUTION
Risk of irreversible damage to the machine or the
electrical system.
►Tightening toques must be used to warranty the correct
electrical contact with said connections.
CAUTION
Risk of irreversible damage to the machine.
►Tightening torques must be used to warranty the correct
electrical contact with said connections.

11
InstallationGeneral instructions
transforma.earth
IG-286-EN version 01
8) Connect the earthing transformer to the medium
voltage (MV) circuit. Use flexible connections that do
not exert force on the earthing transformer bushings,
with sufficient gauge to avoid excessive heating and, at
the same time, allow for the possibility of expansion
due to heating, so they do not damage the earthing
transformer.
9) If the earthing transformer has secondary winding,
connect the earthing transformer to the low voltage
(LV) circuit, by means of flexible connections that do
not exert force on the earthing transformer bushings,
with sufficient gauge to avoid excessive heating and, at
the same time, allow for the possibility of expansion
due to heating, so the machine is not damaged.
10) The neutral medium voltage for the earthing
transformer must be connected at the earthing point
provided for the equipment, according to that
specified for the particular project.
11) If the earthing transformer has a switch, verify that it is
in the correct position, and, if it is a multi-voltage
earthing transformer, that the medium voltage (MV)
wrapping is connected to electrical voltage that will
conform to the service voltage.
CAUTION
Risk of irreversible damage to the machine.
►Tightening torques must be used to warranty the correct
electrical contact with said connections.

12 Setup General instructions
transforma.earth
IG-286-EN version 01
5 SETUP
5.1 Check the earthing transformer before
placing it in service
Once the earthing transformer is connected to the medium
voltage (MV) and low voltage (LV) networks, if applicable, and
before executing electrical voltage supply, the following
checks must be performed:
1) Check that the medium voltage (MV) electrical voltage
network corresponds to the electrical voltage assigned
to the earthing transformer.
If there is built-in secondary winding:
1) Supply the no-load earthing transformer under no-load
conditions, and measure the low voltage (LV) electrical
voltage that the machine delivers, testing its correct
connection and adjustment.
DANGER
In the event the earthing transformer is supplied with
current transformers, check that they are connected to
the medium voltage circuits or that they are short
circuited. Never put an earthing transformer in service
with the secondary current transformer open.
DANGER
Risk of death due to electrocution and irreversible
damage to the machine or the electrical system
►The tap changers must always be operated without electrical
voltage, ensuring that ultimately, the actuation is firmly fixed
and in its working position.
►Check that the electrical voltage corresponds to the nominal
voltage of the earthing transformer. In the event of an anomaly,
contact Ormazabal.
►If, after placing the earthing transformer in service, an
adjustment must be made, follow the safety instructions
specified in Section 6.1 of these general instructions document,
called «Access for maintenance operations».

13
SetupGeneral instructions
transforma.earth
IG-286-EN version 01
3) Apply the charge gradually, until reaching operational
power, being careful that the earthing transformer’s
temperature does not surpass a value of 105
°C.
2) Adjust the electrical voltage on the earthing
transformer using the corresponding tap changer,
keeping in mind the safety requirements described in
the previous warning:
Fig. 5.1: Tap changer detail
IG168-007

14 Maintenance General instructions
transforma.earth
IG-286-EN version 01
6 MAINTENANCE
6.1 Access for maintenance operations
Before performing any maintenance operations on the
earthing transformer, all measures required by applicable laws
must be followed, among which must be emphasized:
1) Disconnect all sources of medium voltage (MV) and
low voltage (LV) electrical circuits, if applicable, until
the earthing transformer is shut down, interlocking or
locking the required short-circuit devices, to avoid any
possible feedback.
2) Verify that there is no electrical voltage.
3) Connect to earth and short-circuit all sources of
electrical voltage.
4) With an insulating pole, earth the earthing transformer
bushings, ensuring that there is no static charge in
them.
5) Restrict and properly indicate the work area.
6) Check that there are no dielectric fluid leaks
6.2 Periodic maintenance
It is recommended that a periodic visual inspection be
performed of the earthing transformer and the following
aspects:
►Tightness: check that there are no dielectric fluid leaks.
►Cleaning: check for proper cleaning and maintenance.
►Noises: check that there are no anomalous or abnormal
noises.
►Measurement tools: periodically record the installed
instrument readings, such as the thermometer, oil
level, and/or internal pressure. Check that the readings
are within appropriate values and that no variations
appear with respect to the previous measurement.
Table 6.1 Shows the recommended points and minimum
frequency for which maintenance should be performed.
DANGER
Risk of death due to electrocution and irreversible
damage to the machine or the electrical system
►Before handling the fixture, reliably follow the instructions in
Section 6.1 of these general instructions document.
►No not operate the earthing transformer tap changer when it is
connected to electrical voltage.
CAUTION
Risk of irreversible damage to the machine or the
electrical system.
►If there is a dielectric fluid leak, contact Ormazabal.
DANGER
Risk of death
►Comply with all requirements established by current law, to
protect people and the integrity and operation of goods that can
be damaged from the these installations.

15
MaintenanceGeneral instructions
transforma.earth
IG-286-EN version 01
Operation Elements to control Frequency Observations
1 Accessories with alarm and
firing contact 1 time every 2 years
Verify conditions of use, the contacts
and measure the the electrical circuit
insulation
2 Terminal box 1 time every 2 years Check connections and clean dirt off
3 Silica gel 1 time per year Check the condition of the silica gel If
needed, replace it
4 Terminals 1 time every 2 years Check condition and clean
5Thermometer 1 time per year Check the maximum temperature
recorded and record it
6 Insulation resistance 1 time per year
When a change is detected in the
results after years of using
the transformer or from comparing
data from previous tests
7 Measuring the
equipment’s tan δ 1 time every 3 years
8Superficial oil voltage test 1 time per year
9Oil acidic value 1 time every 3 years
10 General oil condition test
Whenever the tests show abnormal
data
6 to 10.
Whenever a maximum temperature
is recorded that is greater than
105 ºC
Take an oil sample and perform tests
according to IEC Standard 60422
11 Oil humidity content test
Whenever the tests show abnormal
data
6 to 10.
Whenever a maximum temperature
is recorded that is greater than
105 ºC
12 Oil insulation filtering
If the results of operations 10 and 11
show values greater than standard
limits
Tab. 6.1: Maintenance frequency

16 Maintenance General instructions
transforma.earth
IG-286-EN version 01
6.3 Repairs
If the earthing transformer shows any anomaly in its operation,
the user should contact Ormazabal, who will advise the
proper measures to take.
If the check of the earthing transformer requires its repair or
modification, said operations must be performed by
Ormazabal.
If the repair or modification is performed by a company other
than Ormazabal, the repairer must incorporate a plate on the
machine with the modification or repair that they have
performed and the new properties of the machine.
In the event that the earthing transformer is not
handled or unsealed by Ormazabal, we cease
responsibility for its operation and reliability.

17
Additional informationGeneral instructions
transforma.earth
IG-286-EN version 01
7 ADDITIONAL INFORMATION
7.1 Reliability
The earthing transformer which, as tests show, leaves the
factory free of defects, is prepared to provide service for its
entire «service life».
However, it is essential that the level of reliability be
maintained during its handling, storage, and transport, and
that it be put into service with the appropriate verifications
and protections established in medium voltage
electrotechnical regulations, and that its maintenance follows
the instructions compiled in these general instructions
document.
Additionally, it is necessary that required measures be taken
during its installation for the protection of those who work
around it, either regularly or incidentally, and that all external
personnel avoid proximity to it during its operation.
7.2 Business registration certificate
Business Registration Certificate Nº ER – 0227 / 1996, granted
by AENOR – EQ – NET, dated May 23,1996, guarantees that our
Quality Assurance System, implemented from the design and
product development phase up through Post-Sale Service,
establishes the management criteria and procedures and
processes that guarantee that earthing transformers are
delivered free of defects, including suppliers in this systematic
process, and applying the knowledge and lessons derived
from investigations and special and type tests, which allow
homogeneity of the product’s components design,
manufacturing procedures and testing, and staff development
and continual improvement of the entire process to be
warranted.

18 Attachment General instructions
transforma.earth
IG-286-EN version 01
8 ATTACHMENT
The recommended tightening torques for the medium voltage
(MV) and low voltage (LV) connections, are as follows.
(*) The medium voltage terminals include three nuts, but only the two upper ones should be handled, of fixed ones on the terminal, since the
task of the lower one is to apply pressure to the insulator joint and if loosened, it could cause loss of dielectric fluid.
Tab. 8.1: Recommended tightening torques [Nm]
Metric Size M10
Low voltage (LV)
• Connection between nuts. 15-20 70-100 250-350
25-35 40-60 85-95
25-35 40-70 100-150
Low voltage through-rod connections
(Steel screw and nut). 45-60 65-85 95-130
10-15 15-20 25-30 65-75
M12 M16 M20 M30
Key Size 17 19 24 30 46
• Attaching the blades to the bolt
(stainless steel screws)
• Screws on the blade surface.
Medium voltage (MV)
Attaching the terminals to the medium voltage bolt
(brass bolt and nuts [*])
CAUTION
The values given by the component’s manufacturer shall
always prevail, in the event of a discrepancy
with those in Table 8.1.

Subject to changes
without prior notice.
For more information,
contact Ormazabal.
Ormazabal Cotradis
Transformadores
LOECHES
(Spain)
www.ormazabal.com