WeTransform energy

Power transformersUp to 160 MVA | Up to 245 kV

Interior view of IMEFY’S facility in Spain

Some of Our Customers:

POWER TRANSFORMERS02

Since IMEFY was founded in 1973 as a company dedicated to the manufacture of liquid-inmersed distribution transformers, it has followed a path of continuous development, in terms of technology as well as expansion, becoming one of the world’s leading manufacturers of a wide range of transformers, including:

•Medium-sized liquid-immersed power transformers, with power ratings from 10kVA to 40MVA and insulation levels from 1.1kV to 36kV.

•Large liquid-immersed power transformers, with power ratings up to 160MVA and an insulation level of 245kV.•Epoxy-resin encapsulated transformers (dry-type), with power ratings from 50kVA to 6MVA and insulation levels from

1.1kV to 36kV.

All transformers are designed and manufactured according to all applicable legal requirements, such as European Regulation Nº 548/2014 of the EC 21/05/2014 (ECODESIGN), standards, such as IEC 60076, applicable ANSI standards, etc., and client specifications.

One of IMEFY’s hallmarks is the high standard of quality and reliability of its entire product line, which is achieved thanks to the company’s qualified staff, cutting-edge technology for the design, manufacture, and control of the processes and finished products in its test laboratories, and its post-sale service to track customer satisfaction.

All of this, in combination with an internal Environmental and Sustainability policy, and the prioritization of the well-being and occupational health of our workers, has helped the IMEFY GROUP to gain the recognition and trust of its customers, allowing it to expand its operations over 5 continents.

The IMEFY GROUP is made up of the following companies:

•IMEFY SPAIN, located in Los Yébenes, as the central office, with a factory that produces the entire line of transformers.•IMEFY ITALY, with offices in Arezzo, manufactures epoxy-resin encapsulated transformers.•IMEFY POLSKA, located in Świebodzice, distributes and represents the IMEFY transformer brand to provide service

to Eastern Europe.•EUROMATEL, with offices in Oporto, is the distributor and representative of IMEFY transformers that provides service

to Portugal and Portuguese-speaking African countries.

In terms of the different types of power transformers, IMEFY has the capacity, resources, and experience to manufacture a wide variety of transformers and autotransformers, including single-phase to two and three columns, as well as three-phase to three and five columns, intended for applications such as:

•Distribution.•Generation.•Traction.•Rectifiers.•Furnaces.•Voltage dips•etc.

All of these types of transformers or autotransformers can be equipped with:•No-load tap changer (linear or rotating).•On-load tap changer, using vacuum or oil switching technologies and positive configuration (fine regulation or coarse

fine regulation) or inversion configuration.

Lastly, IMEFY, in keeping with the Strategic Plan of its organization, MAINTAINS its quality and management system based on ONGOING IMPROVEMENT, supported on the pillars of the CUSTOMER’S VOICE, ANALYSIS AND IMPROVEMENT OF PROCESSES, and DEVELOPMENT OF NEW PRODUCTS (R&D&I).

Introduction

Our Certificates:

POWER TRANSFORMERS 03

Design is the first and most critical milestone in the construction of a power transformer.

It requires a detailed study of the requirements to properly determine the fundamental parameters of the transformer that will be built.

The design consists of several different parts that are clearly distinct but interrelated: These are:• Electromagnetic design.• Thermal design.• Mechanical design.• Noise level.

Design

04

The first step is to identify the fundamental parameters, such as:• Power.• Transformation ratio.• Short-circuit impedance.• No-load losses.• Load losses, etc.

Once these parameters have been identified and specified, the dielectric behaviour is analysed through a study of the following phenomena:• Behaviour of the active part in the different tests that are carried out, analysing the distribution of the electric field and dielectric phenomena in

the materials used.• Study of overvoltage transferred between windings and the effects of those overvoltages.• Study of the voltage distribution among the different parts of the windings in the cases of atmospheric discharge impulses, etc.

Electromagnetic design

Die

lect

ric a

naly

sis

usin

g th

e fin

ite e

lem

ent m

odel

ling

(FE

M)

POWER TRANSFORMERS

Shaded PlotRMS |B|

12.025391.620311.215230.8101550.4050780

Shaded PlotRMS |B| smoothed

1

0.550.4583330.3666670.2750.1833330.091666700

Based on all of this, we can then define the transformer’s geometry, winding type, materials, and ideal arrangements.

The analysis of the electro-magnetic behaviour is carried out simultaneously. This includes:• Study of the behaviour of the magnetic circuit and distribution of magnetic flux in the transformer.• Study of eddy losses on the windings and distribution on them (linked to thermal design).• Study of supplementary losses on metal parts and the need to make changes in material types and their arrangements (linked to thermal design).• Study of hot spots on windings (linked to thermal design).• Verification of thermal suitability of the tank (lined to thermal design).• Study of the stresses on windings and internal structural components due to short-circuit (single-phase, two-phase, three-phase) in the

transformer, ensuring that it can handle them adequately (linked to mechanical design).

05

3D e

lect

ro-m

agne

tic a

naly

sis

(FE

M)

2D e

lect

ro-m

agne

tic a

naly

sis

(FE

M)

POWER TRANSFORMERS

This is done once the electro-magnetic design has been studied and defined.

The thermal design analysis takes the following aspects into account:

• Calculation of temperature rise of conductors above the temperature of the cooling liquid.

• Calculation of the thermal distribution of the cooling liquid in the tank and determination of the average gradient above ambient temperature.

• Calculation and dimensioning of the cooling system in the following possible configurations:

* CAPTIONS: O - Oil / K - Ester synthetic / A - Air / W - Water / N - Natural / F - Forced / D - Directed

Description Means type Cooling type Means type Cooling type

ONAN (ON) Natural oil cooling (AN) Natural air cooling (radiators)

ONAF (ON) Natural oil cooling (AF) Forced air cooling (fan coolers, radiators, fans)

KNAN (KN) Cooling with natural or natural synthetic esters (AN) Natural air cooling (radiators)

KNAF (KN) Cooling with natural or natural synthetic esters (AF) Forced air cooling (fan coolers, radiators,

fans)

OFAN (OF) Forced oil cooling (oil pumps) (AN) Natural air cooling (radiators)

OFAF (OF) Forced oil cooling (oil pumps) (AF) Forced air cooling (fan coolers, radiators, fans)

ODAF (OD) Directed oil cooling (oil pumps) (AF) Forced air cooling (fan coolers, radiators, fans)

OFWN (OF) Forced oil cooling (oil pumps) (WN) Natural water cooling (water exchanger)

OFWF (OF) Forced oil cooling (oil pumps) (WF) Forced water cooling(exchangers, water pumps)

1st letter 2nd letter 3rd letter 4th letter

Cooling means in contact with windings. Cooling means with the external cooling system.

Thermal design

06

Ther

mal

ana

lysi

s

POWER TRANSFORMERS

This is done once the electro-mechanical and thermal designs have been studied and defined, allowing the following aspects to be analysed and developed:

• Design and verification using finite-element tools (hereinafter FEM) of clamps, considering minimal supplementary losses and ensuring suitability in the case of a transformer short-circuit.

• FEM design and verification of the tank and its structural elements in response to vacuum and overpressure, as well as the radiators and hoisting elements.

• Checking for interference: assemblies, electrical distance in air, etc.

DeformaciónTipo: DeformaciónUnidad: mm28/01/2014 10:19

0,13639 Máx

0.12124

0,10608

0,090927

0,075772

0,060618

0,0454630,045463

0,030309

0,015154

0 Mín

DeformaciónTipo: DeformaciónUnidad: mm28/01/2014 8:59

5,7393 Máx

5,1016

4,4639

3,8262

3,1885

2,5508

1,91311,9131

1,2754

0,6377

0 Mín

Mechanical design

07

Verifi

catio

n of

min

imum

insu

latio

n di

stan

ces

in a

irS

truct

ural

ana

lysi

s of

cla

mps

(FE

M)

Stru

ctur

al a

naly

sis

of th

e ta

nk (F

EM

)

POWER TRANSFORMERS

08

Power Laboratory (IMEFY Spain)

POWER TRANSFORMERS

Once the mechanical design has been completed, and taking into account the cooling system that will be used, compliance with the requested noise-level requirements is then verified, based on the following factors:

• Geometry, fabrication method, and quality of the magnetic circuit.• Operating induction of the transformer.• Noise level of exterior elements related to the cooling system, such as fans, pumps, etc.• Height and perimeter of the transformer.

Noise level

09POWER TRANSFORMERS

The magnetic core is built with two, three, or five columns, with a circular cross-section and flat yokes.

It is made of cold-rolled, low-loss grain-oriented silicon steel sheet metal.

The system chosen for the core assembly is known as step-lap, in order to minimize losses as well as no-load current, and to help reduce the noise level during transformer operation.

To do this, it is equipped with high-precision machines for cutting magnetic sheet metal with automatic control systems.

The magnetic cores are installed in metal frames designed to withstand the mechanical stresses due to possible short-circuits, and also to maintain the correct positioning of the magnetic circuit, in order to reduce the noise level and at the same time mitigate the effect of the dispersion flow from the active part on them.

Core

10

Cut

ting

mag

netic

she

et m

achi

ne

Once the overall design has been completed and the proper specifications have been defined for each component, manufacturing begins. The process includes the following milestones:

• Core.• Windings.• Assembly.• Treatment of the active part.• Filled, treated, and impregnated with dielectric fluid.• Final operations.

Manufacturing

POWER TRANSFORMERS

The primary, secondary, and possibly tertiary transformer windings may each be made up of one or more windings, each of which may be constructed using one of the following methods:

• Continuous coil• Interleaved coil• Coil with radial spacers• Layers• Layer with radial spacers• Continuous disc• Interleaved disc• Disc with axial spacers.

The raw material that is used to manufacture the windings is copper, as well as top-quality insulation that are stored in a climate-controlled room at the proper temperature and humidity. The raw material may be used in the following arrangements:

• Single flat wire• Twin conductor• Triple conductor• Continuously-transposed conductor (CTC)

To construct these windings, IMEFY has winding machines with extending mandrels that can flip windings up to 2000mm in diameter and 3000mm long. Each of these is equipped with racks for securing spools of raw materials, with up to 32 shafts, with their respective brakes and correct conductor tensioning, which is very useful to produce interleaved coil regulation windings.

Windings

11

Power winding machine

Continuous disc LV winding

POWER TRANSFORMERS

Once the operations to assemble the magnetic circuit have been completed (with the exception of the top yoke), and all of the windings have been prepared, the following sequence of operations is carried out:

• Assembly of the windings following the operational guidelines in the technical specifications, always ensuring that the insulation is maintained in the proper temperature and humidity at the time of installation, removing the material from the climate chamber.

Assembly

12C

limat

e C

ham

ber

POWER TRANSFORMERS

• Simultaneous thermal and mechanical treatment of the winding and phases, to achieve the calculated nominal dimensions and ensure correct response in the case of a short-circuit.

• Preparation of the magnetic circuit to receive the complete phases on the columns.

• Once the windings have been inserted on the columns, the top of the magnetic circuit will be closed and the transformer cover will then be put in place, followed by the internal connections of the transformer according to the complete and precise technical specification, with exhaustive monitoring control of the entire process.

13

Mec

hani

cal t

reat

men

t

Act

ive

part

of th

e tra

nsfo

rmer

POWER TRANSFORMERS

Finally, once the active part has been validated, the moisture must be removed from the insulation system. To do this IMEFY has a drying plant that uses kerosene at high temperature and low pressure (Vapour Phase).

The treatment with the Vapour Phase system consists of alternating phases of heating (up to 125°C) and evaporation (to approximately 20 millibar), which draws out the water from the active part along with the kerosene, with the quantity extracted monitored continuously based on the weight of the insulation and time.

The parameters that affect the Vapour Phase drying system are:• Transformer’s power rating (size).• Insulation level.• Weight of the insulation.• Transformer configuration and geometry.

When the active part has been removed from the drying treatment (Vapour Phase), it is retightened based on the stresses that are predicted for the transformer in the case of a short-circuit. When the active part has been retightened, the following final checks are run:

• Tightening torque values.• Resistance of the insulation of the magnetic-reinforcement circuit.• Visual Inspection.

The active part is then put into the tank that has been previously prepared.

14

Trea

tmen

t in

Vapo

ur P

hase

Treatment of the active part

Vapour Phase

POWER TRANSFORMERS

15

Die

lect

ric fl

uid

treat

men

t

Filled, treated, and impregnated with dielectric fluid

Final operationsThe final step to finish the transformer is the completion of the assembly of accessories and guards, and properly connecting them to the signal centralization cabinet.

When this work has been completed, the transformer is ready for the test bench.

After the active part has been put into the tank and sealed, the tank is subjected to a total vacuum. Once the vacuum has stabilized, the transformer is filled with the dielectric fluid that applies in these conditions.

The dielectric fluid is filtered until the necessary parameters, defined in the specification, have been achieved.

When the dielectric fluid treatment phase has been completed, the transformer is subjected to an accelerated impregnation process that consists of subjecting it to a pressure twice its height for a specified time.

POWER TRANSFORMERS

IMEFY has developed the necessary methodology to manage the acceptance of raw materials, in order to guarantee compliance with the previously established technical specifications.

Power transformers may incorporate the following types of connection terminals:• Conventional (open bushing).• Pluggable (pluggable bushing).

The following materials are used in their manufacture:• Dry (resin-encapsulated): pluggable.• Porcelain.• Composite.

16

Ana

lysi

s fo

r det

erm

inin

g di

elec

tric

fluid

moi

stur

e

DG

A an

d m

oist

ure

in o

il

Ana

lysi

s fo

r det

erm

inin

g di

elec

tric

stre

ngth

of t

he d

iele

ctric

flui

dC

ompo

site

bus

hing

Por

cela

in b

ushi

ng

Dou

ble

or q

uadr

uple

con

tact

elb

ow b

ushi

ng

Terminals

Raw materials controls

POWER TRANSFORMERS

Most of the accessories installed on power transformers are aimed at protecting them against risk situations related to:• Excessive increase in oil or winding temperature: to protect the transformer, devices such as the following are frequently used:

• Thermostat. • Thermometer.• Thermal imaging.• Systems for directly measuring winding temperature with fibre optic sensors.

• Pressure increase inside the main tank or body of the on-load tap changer: the protection elements normally used are:• Overpressure valve main tank.• Possibility of installing an overpressure valve for the on-load tap changer body (always protected by a mechanical membrane).

• Oil level in the holding tank too high or too low: to protect against this, the following are normally used:• Indicator of the magnetic level of the dielectric fluids.

• Conservation of large quantities of gas inside the main tank or the tap changer body: the normal protection elements are:• Buchholz relay for the main tank.• RS-2001 relay for the on-load tap changer.

• Increase in moisture and/or generation gas level: the normal protection elements are:• Dryers or dehydrators, both conventional and automatic regeneration.• Devices for the continuous monitoring of gas concentrations (methane, acetylene, ethane, hydrogen, etc.) and the quantity of water.• Flexible separators to completely isolate the dielectric fluid from the environment.

Other devices that are normally used in power transformers to increase their performance in terms of adaptation of conditions to the installations as well as the centralization of signalling and monitoring are:

• Centralization devices for alarms and voltage and current measurements (instrument transformers) for remote readings or online communication.• Equipment for automatic voltage regulation (AVR) of devices connected to the on-load tap changer.• Supports for installation of surge arresters, as well as the supply of them when necessary.• Lastly, all power transformers are equipped with a safety system (lifeline) in accordance with the company’s internal requirements or the customer’s

specifications.

17

Win

ding

tem

pera

ture

On-

load

tap

chan

ger

Principal accessories

POWER TRANSFORMERS

Individual tests, as specified in IEC 60076Tests carried out on each transformer individually.

• Measurement of resistance of windings.• Measurement of the transformation ratio and

verification of the connection set.• Measurement of short-circuit impedance and load

loss.• Measurement of loss and no-load current.• Applied voltage test at industrial frequency.• Test of induced voltage with measurement of partial

discharges, when required.• Lightning impulse test Um>72.5kV.• Test of the on-load tap changer, when required.• Test to verify polarity and ratio of CT s.• Test of the insulation of the core, tank, and clamps.• Functional testing of accessories.• No-load test.• Oil test (dielectric). • Verification of dimensions (with plans).

Type tests as specified in IEC 60076Tests carried out on a single transformer that is representative of the other transformers to demonstrate that they comply with the specified conditions that are not verified by the individual tests.

• Heating test with thermographic measurement.• Standard model dielectric test:

• impulse test Um≤ 72.5kV.• impulse chopped on the tail test.• chopped lightning impulse test.

• Test of chopped or long-duration induced voltage, depending on the transformer characteristics, with measurement of partial discharges.

• Tests to determine noise levels.• Paint tests.• Pressure test.

18

Applied voltage system Platform for power tests Lightning impulse system

Tests

POWER TRANSFORMERS

Special TestsTests that are not type tests or individual tests, defined in agreement with the manufacturer and purchaser.

• Determination of the winding capacity to ground and between windings.

• Measurement of the system’s power factor and capacity (tg δ).

• Measurement of zero sequence impedance.• Measurement of insulation resistance of windings.• Measurement of FRA.• Measurement of no-load current harmonics.• Dew point test.• Measurement of power absorbed by pumps and

fans, if applicable.• Thermographic measurement during the heating

test.• Measurement of dielectric strength at 2,000V at the

connection box.• Measurement of time constant in reabsorption

voltage.• Measurement of vibration in fans.

19

FRA analyser Analyser for capacity and tg δ Insulation resistance analyser

Test equipmentIMEFY’s HV laboratory has the following equipment that is used to carry out the tests described above:

• System for generating impulses of up to 1400kV.• Applied voltage system up to 500kV.• Generator-transformer system for power tests, no-

load tests, short-circuit, heating, 36 MVA active power plus capacitor bank, up to 33MVA reactive power.

• Class 0´1 voltmeter for power measurements.• Resistance meter with measurement of harmonics

and transformation ratio.• FRA analyser-meter.• Analyser-meter for capacity and tg δ.• Analyser-meter for insulation resistance.• Analyser-meter for CTs.

POWER TRANSFORMERS

Hasta 120 MVA | Hasta 245 kVIMEFY CAT_ING_PT 02/2017Design: Marketing and Communication Department of IMEFY S.L.

IMEFY follows a continuous improvement policy, and reserves the right to modify this catalogue without prior notice, not acquiring any responsibilities for it. The content of this catalogue is to provide information, it does not imply any commitment. Please, contact IMEFY for information.

Industrias Mecano Eléctricas Fontecha Yébenes S.L. (IMEFY S.L.)Polígono Industrial “La Cañada”, Avenida Siglo XXI s/n, E-45470 Los Yébenes, Toledo (Spain)

T.: +(34) 925 32 03 00 | F.: +(34) 925 32 10 00 | imefy@imefy.com | www.imefy.com