Dt Catalogue 4j5g44

TRANSFORMERS

DISTRIBUTION

WWW.PAUWELS.COM [email protected]

© PAUWELS DT 03/03

PAUWELS INTERNATIONAL N.V. Antwerpsesteenweg 167 B-2800 Mechelen (Belgium) Tel. + 32 15 283 333 Fax + 32 15 283 300

TRANSFORMING YOUR NEEDS INTO SOLUTIONS

Presentation of the Pauwels Group

5

Construction of a distribution transformer the ferromagnetic core

6 6

the windings

10

the active part

12

the tank

14

finishing operations and testing

18

A comprehensive product range

20

Economic choice of transformers

22

Transformers and the environment

24

low-noise transformers

25

leakproof tanks and environmentally sound coolants

26

recyclable materials

26

radical exclusion of PCBs

27

electromagnetic compatibility

27

optimized use of raw materials

27

lower consumption of primary energy sources, due to the use of transformers with low losses

Design, specifications and standards Logistics Quality assurance Sales and customer service After-sales service Protection equipment

CONTENTS 4

s

27

28 29 30 32 33 34 35

3

The Pauwels Group is one of the world’s leading transformer manufacturers. Group companies operate manufacturing plants and sales offices in three continents, with a worldwide network of sales agents and customers in over 135 countries.

From its base in Mechelen, Belgium, Pauwels International N.V. acts as the overall holding company, defining the Group’s

This brochure provides information

corporate strategy and coordinating the marketing of its entire

about Pauwels’ liquid-filled distribution

product range.

transformers.

The Pauwels Group is a full-line supplier, offering a wide

Our distribution transformers are usually

range of transformers consisting of:

filled with mineral oil. As an alternative,

liquid-filled distribution transformers

silicone liquid or synthetic organic esters

(15 kVA to 10,000 kVA/36 kV)

may be used as insulating medium and

cast resin transformers (up to 10,000 kVA/36 kV)

coolant.

power transformers (up to 575 MVA/500 kV) auto-transformers (up to 400 MVA/500 kV) HVDC station transformers (up to 315 MVA/500 kV DC)

PRESENTATION

of the Pauwels Group

The Pauwels Group’s six manufacturing plants are located in Belgium (Mechelen and Gent) Ireland (Cavan) the United States of America (Washington, Missouri) Canada (Winnipeg, Manitoba) Indonesia (Bogor, Java) In Saudi Arabia, distribution transformers and compact substations are built under license from Pauwels.

Main factory and headquarters of the Pauwels Group in Mechelen, Belgium (49,500 m2)

Pauwels International N.V. and its subsidiary companies employ a total of over 2,300 people, producing some 30,000 transformers each year with a total output of

Pauwels Contracting N.V. (Mechelen, Belgium) special-

more than 35,000 MVA. Pauwels International has a

izes in building conventional, mobile and modular

consolidated annual turnover of some 350 million euros,

substations, and its core activities also include

over half of which represents exports from Europe. More

transmission line projects.

than 500,000 Pauwels transformers have been produced since the company’s formation in 1947.

Distribution transformers are manufactured in Mechelen, Belgium (100 kVA to 10,000 kVA/36 kV)

Winding area in Pauwels Trafo Ireland

Pauwels Trafo Service S.A. (Charleroi, Belgium) provides

Cavan, Ireland (15 kVA to 630 kVA/36 kV)

transformer installation, repair and maintenance services.

Washington, USA (45 kVA to 10,000 kVA/69 kV)

5

The construction of a transformer comprises two active components: the ferromagnetic core and the windings. Within the transformer industry, the core and windings together are normally referred to as the “active part”. The ive part of a transformer is the cooling system, consisting of the tank and the cooling liquid (mineral oil, silicone liquid or synthetic organic esters).

The reactive power dissipation can be lowered by limiting flux disturbances and minimizing air gaps in the ts between the core legs and the yokes. This is achieved by overlapping the core sheets while stacking them (see page 9 under “Cutting and stacking of the core sheets”).

The ferromagnetic core

Evolution of the quality of magnetic steel

CONSTRUCTION

of a distribution transformer

The heart of the matter: the ferromagnetic core The cut of the core sheets and the material of the ferromagnetic core are optimized according to the desired no-load characteristics and the specified noise level. Extensive rationalization of the shape and the

Material

clamping devices enables us to produce a core with minimum losses and dimensions. This methodology optimizes the consumption of both

The core is constructed using thin sheets of cold-rolled grain-oriented

materials and energy, bringing benefits to the , the environment and

magnetic silicon steel insulated on both sides. Conventional grain-

the manufacturer.

oriented steel (CGO steel) is used for transformers with normal no-load loss characteristics, while transformers with reduced no-load

The core has to be constructed in such a way as to limit the energy

losses are built using higher-quality HiB steel (usually laser treated).

losses caused by eddy currents and hysteresis to a minimum. This is

These steel sheets are 0.30 mm, 0.27 mm or 0.23 mm thick.

achieved by the use of silicon steel, a special soft steel with a 3.5% silicon

6

content, which is characterized by low hysteresis losses and high

Extremely low no-load losses can be achieved only by using wound cores

resistivity. The core consists of a series of laminations made from very

made of amorphous metal. This has highly specific properties (very thin

thin sheets of steel insulated on both sides by an oxide layer (see opposite

sheets just 0.025 mm thick are used) and therefore it requires a specially

under “Material”).

adapted design.

7

Cutting and stacking of the core sheets Minimum magnetic flux distortion in the transition areas between yokes and core legs is achieved by optimizing the cut of the core sheets and the stacking pattern. First of all, the core sheets are cut at an angle of 45°, thus allowing maximum flow of magnetic flux in the rolling direction. This is extremely important because losses in grain-

The core: main characteristics:

oriented magnetic steel are smallest in the direction of rolling. Then the sheets are stacked in an overlap pattern of either single or multiple overlaps. The multiple overlap or step-lap method

The 45° cut of the core

offers additional benefits in of lower no-load losses and noise levels. Because they

sheets guarantees optimum

involve a rather more complicated production technology, step-lap cores are preferably made

flow of magnetic flux.

on fully automatic cutting and stacking machines.

The oval shape allows optimization of the core

Once the sheets are stacked, the core is compressed and glued to form a firmly-bonded

section.

whole. This also helps to reduce noise levels.

Low sound levels can be achieved using the step-lap stacking pattern.

The ferromagnetic core

The type of magnetic steel is chosen according to

CONSTRUCTION

the desired loss level. The simple ing structures and clamping devices of the core contribute to the compactness of

of a distribution transformer

the design.

Shape of core section The vast majority of the distribution transformers built by Pauwels have an oval-shaped core section, formed by combining the traditional stepped and fully filled round shape with a square mid-section. This gives great flexibility in the height to which the steel sheets can be stacked, Typical oval-shaped core cross section

thus allowing the ideal core section to be made for any design, while maintaining the use of standard materials and dimensions. Using this method combines the benefits of a rectangular core section (simplicity of production) with those of a round core section (excellent short-circuit withstand capability of the windings).

Clamping devices By using simple profiled-steel yoke clamping systems and a number of metal tensioning bands, Pauwels has eliminated the need for either clamping bolts in the yokes (which would distort the magnetic flux) or tie rods between the upper and lower yokes (which would require the tank to be larger).

Fully automatic cutting and stacking machine

9

Windings

CONSTRUCTION

of a distribution transformer

LOW HIGH RADIAL REPELLENT FORCES ACTING ON HV AND LV WINDINGS

Low voltage windings

HV

Low voltage windings are usually made of copper or aluminium sheet conductor (foil). The benefit of this is that any high voltage ampere-turn asymmetry which might occur is compensated automatically by an appropriate internal current distribution in the low voltage foil.

LV

CORE

High voltage windings RECTANGULAR

ROUND

OVAL

High voltage windings are almost exclusively of layered construction. The copper or aluminium conductors are made of one or more round or

This reduces the axial stresses produced by short-circuits to a minimum

square wires, either with an insulating enamel coating or wrapped in

(down to 10% of those for conventional windings), thus enabling the axial

insulating paper. Each design is drawn up in accordance with the specific

construction to be greatly simplified.

characteristics of the conductor material to be used.

The sheets and connectors welded onto them are made of electrolytically

The insulation between the layers consists of pre-coated kraft paper,

pure copper or aluminium with a rigorously guaranteed conductivity.

applied either in sheet form or wound in a continuous narrow strip,

Designs are adapted to the thermal, electrical and chemical characteristics

a technique which allows optimum adjustment of the insulation thickness

of each type of conductor, thus ensuring that both versions are of

to the electrical gradient at each layer position.

equivalent quality, whether made of copper or aluminium. The special diamond pattern of epoxy adhesive coated onto the kraft The maximum voltage between each turn is only a few tens of volts. This

paper cures during the drying process, bonding the windings into a single

allows the insulation needed between the turns (foils) to be limited to 1 or

structure.

2 sheets of fine kraft paper only a few hundredths of a millimetre thick. The high voltage winding is wound directly onto the low voltage winding, According to the design specification, this insulation may be coated with

over the structures forming the main gap, giving maximum mechanical

a thermo-hardening epoxy adhesive which cures and bonds during

strength, rigidity and compactness.

the drying process.

Supplementary benefits of foil windings are: Greater simplicity in fitting

They form a simple winding, which allows continuous or

This mechanical strength is of the utmost importance since, in the event of

semi-automatic winding.

Foil windings may be wound either on a winding mandrel or, preferably,

short-circuit, the windings have to sustain very high radial repellent forces.

The impulse voltage distribution

directly onto the core leg. This ensures minimum play between core and

The mechanical effect of these forces is minimal in round windings, since

throughout the winding is

winding, for optimum rigidity.

these windings inherently have the ideal form to withstand radial stresses.

predictable and controlled.

The mechanical effect is much greater in rectangular windings. In order to

Axial cooling ducts are simple

cooling ducts.

10

The main benefits of layered windings are:

More even heat distribution

The structures forming the “main gap”, i.e. the insulating space separating

combine the advantages of a rectangular core section (simplicity of

to build and fit.

through the windings.

the low and high voltage windings, are fitted directly onto the low voltage

production) with the benefits of round windings (excellent short-circuit

Any taps required can be

Semi-automatic winding

foil winding, thus forming a part of it. These processes all enhance

withstand capability), Pauwels has developed the unique concept of

brought out anywhere in the

techniques can be used.

the transformer’s short-circuit withstand capability.

oval-shaped cores and windings (see drawing above).

winding through the layers.

11

Assembling cores and windings to build an active part

Bushings are mounted on the cover, which is then fixed onto the assembled active part. The next step consists of connecting the

Assembly of cores and windings

windings

to

the

bushings.

to build an active part may be

The connection methods are durable and selected so as to ensure a solid, low-resistance connection between

carried out in either of the following

the linked conducting materials, including junctions between aluminium and copper components.

two ways: Transformers are often fitted with an off-circuit tap changer. This switch allows the increase or decrease of If the windings have been wound

a certain number of turns while the transformer is disconnected from the circuit. Small variations in the nominal

on a mandrel, the E-shaped cores

supply voltage can be accomodated by adjusting the tap changer to keep the output voltage at the required value.

and the windings are transported from their various construction

The off-circuit tap changer is always fitted on the high voltage side of the transformer, since this is where

locations to the assembly area.

the current is smallest. A second tap change switch is incorporated in transformers with dual high voltages in order

The windings are pushed over the

to change the high voltage. Tap changers and tap switches are controlled either by cable or by a drive shaft.

core legs and wedged up to fill the spaces between the core and

The voltage ratio of the active part is then tested, and the assembly is dried for a specified time in a forced-air

winding as much as possible.

oven to remove the moisture from the insulating materials. This time depends on the quantity of insulating

The magnetic circuit is then

materials, which in turn depends on the transformer’s rating and voltages.

completed by interleaving the laminations of the upper yoke with the laminations of the core legs.

If the windings have been wound directly onto the core legs, the three core legs are positioned on a tilting table. The upper and lower yokes are then fitted highly accurately in the

Active part

CONSTRUCTION

of a distribution transformer

same way as described above.

13

Hermetically sealed transformers offer indisputable advantages compared with transformers fitted with a conservator, including:

Functions of the transformer tank: It forms a container for the cooling liquid.

The insulating liquid cannot come into with the air,

It acts as a heat exchange surface for the

thus guaranteeing preservation of its dielectric integrity.

dissipation of heat losses.

Reduced maintenance, e.g. no checking required of the air dryer,

It is a protective, earthed safety shell.

no need to monitor the liquid for water ingress, etc.

It provides shielding against electromagnetic field

They are cheaper to buy.

leakage caused by current-carrying conductors.

They occupy a smaller space, leaving more room for connections in compact installations. The protection equipment is often simpler than that fitted on transformers with a conservator.

The tank

Corrugated fin wall s

CONSTRUCTION

of a distribution transformer

The reliability of hermetically sealed tanks is illustrated not merely by the tens of thousands of transformers currently operating worldwide, but also by the stringent fatigue and overpressure tests carried out on transformers of this type. Hermetically sealed tanks have been subjected to 11,000 expansion-contraction cycles, which simulate the mechanical load on a tank over a service life of 30 years (at an average of 1 cycle per day). The construction of these tanks is extremely simple. The bottom, top frame, corrugated fin wall s and plain wall s are mounted on specially designed rotating welding tables and welded together. Small

Construction

production batch sizes resulting from the wide range of transformer designs produced do not yet allow this

The vast majority of distribution transformer tanks are

the use of a gas cushion to allow the expansion of

process to be carried out by fully automated welding equipment. The skill and craftsmanship of highly experienced

constructed with cooling fins. There is only a very

the liquid. This gas cushion allows the internal pressure

welders and leak tests during production ensure leak-free finished tanks.

limited demand for radiator types. As with

to be maintained within the acceptable limits permitted

radiators, the purpose of cooling fins is to increase the

by tank flexibility. Occasionally, some customers

available surface for the cooling air. However,

specify that a conservator must be fitted on top of

in hermetically sealed designs the cooling fin design

the transformer tank. This follows older rigid tank

also enables a degree of flexibility which is needed to

design practice.

Cooling

accommodate the expansion and contraction of the

is limited to around 100°C. While a higher operating

liquid as it heats and cools, due to load and ambient

This cylindrical conservator acts as an expansion tank

temperature. This allows the tank to be totally filled

for the cooling liquid when it expands as the windings

Heat is generated inside a transformer by the effects

temperature can reduce the size, weight and cost of a

(and hermetically sealed), with the clear benefit of

heat up. The conservator is often fitted with a gauge

described by Joule’s law, hysteresis losses and

transformer for a given power rating, it shortens its

prolonging the transformer’s service life expectancy

glass, an air vent and an air dryer in an effort to ensure

eddy currents

(see chapter “Economic choice of

service life expectancy by accelerating the ageing of

that only dry air can come into with the

transformers”). This causes a rise in the temperature of

the insulating materials. Cooling is optimized in

cooling liquid, and only at atmospheric pressure. If the

the windings and core. The temperature will reach

accordance

In exceptional cases, e.g. small ratings and severe

air dryer is not properly maintained, it can lose its

equilibrium when the quantity of heat generated per

temperature and the total quantity of heat to be

dimensional limitations, the fins become so small that

effectiveness and allow damp air to come in

second is equal to the quantity of heat removed

dissipated, which depends on the transformer’s

with the cooling liquid.

per second.

loss level.

and reducing maintenance.

they are no longer flexible enough, necessitating

14

The operating temperature of liquid-filled transformers

with

the

maximum

permissible

15

Finishing of powder-coated tanks

Surface treatment and painting After welding, the tank is shot-blasted to remove

Flooding

any surface impurities, leaving a clean prepared surface for maximum adhesion of the paint coating. Air-drying paint is then applied by spraying or flooding.

State-of-the-art painting line

An alternative painting technique is electrostatic powder coating, which is used for tank covers and

A state-of-the-art painting line, incorporating zinc phosphating, electrically

cable boxes and also for complete tanks in some

applied liquid paint and powder coating has been installed in the Irish

factories. Where powder coating is employed, further

factory. This system is one of the most up-to-date developments in the

chemical processes are needed before the powder

field of finishing and the quality obtained is comparable with that required

coating is applied.

by today’s automotive industry for modern car bodies. Tests by independent laboratories have shown that transformer tanks

Several coats of paint are applied, to a total thickness

treated in this way can easily withstand the 2,000 hours hot salt spray

of at least 100 microns, thus guaranteeing adequate

scribed test carried out in accordance with the ASTM B117 and

protection against corrosion for a transformer installed

DIN 50021 standards.

indoors or outdoors. Tanks may be galvanized if requested by the customer. This is often specified for transformers which are constantly exposed to the elements, as with pole-mounted or platform-mounted

Standard tanks are equipped with:

transformers. Galvanizing is also recommended for Powder coating line

transformers used in polluted industrial areas.

securing lugs on the top frame of the tank to secure the transformer during transport lifting lugs on the cover to lift the complete transformer and/or the active part underbase welded to the bottom of the tank with bi-directional rollers (roller base) filling hole on the cover (can also be used to mount an overpressure valve) earthing terminals on tank cover and underbase or tank bottom

The tank

thermometer pocket welded to the tank cover and filled with cooling liquid drain valve at the bottom of the tank (can also be used to take oil samples)

CONSTRUCTION

This standard package can be expanded to include other monitoring and protection instruments (see chapter “Protection equipment”).

of a distribution transformer

1 2 3 4 5 6 7

State-of-the-art painting line in the Irish factory

1

4

3

5

Lifting lugs Drain valve Thermometer pocket Earthing terminals LV neutral bushing LV bushings Filling hole

8 9 10 11 12

Off-circuit tap changer HV bushings Securing lugs Rating plate Underbase with rollers (roller base)

7

6

10 11

2

2

4

12 8

9

17

Finishing operations and testing

CONSTRUCTION

Routine measurements and tests

of a distribution transformer

Measurement of voltage ratios. Vector group test. Measurement of high voltage and low voltage winding resistances. Dielectric test of high voltage and low voltage winding(s) (1 minute at rated withstand voltage and nominal frequency). This test is also known as the “applied overvoltage test” and is intended to check the insulation of one winding from all other transformer components. Double voltage test (1 minute at double voltage and double

Testing

Mounting the active part in the tank

low voltage winding. This is

Once the active part has been dried in the forced air oven, it is given a final

In the test bay, each transformer is subjected to a number of routine

also known as the “induced

measurements and tests.

overvoltage test” and is

comprehensive quality inspection and placed into the tank. The top cover

designed to check the

is then either bolted or welded onto the tank, as specified by the customer.

Fitting of protection equipment

Both sealing methods are equally effective, although welding the cover makes it easier to guarantee the seal is leakproof.

Once routine testing is completed, the protection instruments and other accessories are fitted and the transformer is subjected to a final global

Filling

inspection. Subsequently, the rating plate (stating all the data required by the norm or standard) is fixed to the tank with a bracket. The transformer

18

frequency) induced via the

The transformers are placed in a vacuum chamber and filled with

Some customers specify the brand

pre-treated liquid (filtered, dried and degassed) under deep vacuum. This

and type of liquid to be used for

ensures optimum impregnation of the insulation materials by the cooling

filling the transformer. Pauwels

liquid, giving the insulation structure maximum dielectric strength.

carries stocks of several brands

Most transformers are filled with a high quality mineral oil which complies fully with the requirements of IEC standard 60296.

is now ready for packing and transportation.

insulation within each winding (turn to turn and layer to layer). Measurement of no-load losses and no-load current. Measurement of load losses and impedance voltage with

Packing and transport

the off-circuit tap changer in

and types of oil, which are then

For transport by road, timbers are attached to the two U-shaped profiles

Measurement of the

piped from the storage tanks

forming the roller base, thus enabling the transformer to be secured to

resistances of the insulating

In some cases, transformers are filled with silicone liquid (complying with

through separate circuits to the

the load floor of the truck. A similar procedure is followed for container

system between high voltage,

the requirements of IEC standard 60836) or synthetic organic esters

vacuum chamber. After a specified

transport. When specifically requested by the customer, and mainly

low voltage and tank

(complying with IEC 61099). The liquid acts both as a coolant and as an

stabilization period, the transformer

for transport by sea, the transformers are placed in strong wooden crates

(Megger test).

insulating medium.

is taken to the test bay.

or boxes.

the nominal position.

19

In addition to standard transformer types for distribution applications, Pauwels also builds special transformers for industrial applications. These non-standard types are the result of extensive product development based on constant monitoring and evaluation of changing customer needs in the various market segments. In some cases, special customer requirements have also led to the development of a new product with its own characteristics. Our special distribution transformers have special mechanical and/or electrical characteristics. In the majority of cases, these particular transformer types are designed in such a way that they can be built using standard production techniques, thus requiring only a minimum of modifications in the production process.

A comprehensive

PRODUCT RANGE Special transformer types The Pauwels product range includes the following special distribution transformers, although this list is not exhaustive: single-phase transformers (used mainly in the US,

mono and tri-mono transformers

Ireland and the UK)

transformers with special cable boxes

dual voltage transformers

(filled with air or oil)

amorphous metal distribution transformers (AMDT)

transformers with forced cooling

steep-wave transformers

(by means of fans)

compact substations

transformers with integrated protecting (fuses)

three-winding transformers

and disconnecting equipment (such as

auto-transformers

the intrinsic safe transformer “TPC” for )

converter transformers

SLIM® transformers (very compact high

generator transformers

temperature transformers)

earthing transformers

Big DT (DT design concept up to 12 MVA)

substations with cable boxes and connectors for Ring Main Units (RMUs)

Detailed information about our standard and special

phase shifters

distribution transformers is available upon request.

21

Despite the fact that transformers are highly efficient electrical devices, inevitably some energy is lost during their long service life. This energy loss arises from the combination of no-load losses and load losses. These losses convert to heat which has to be removed during operation.

ECONOMIC

CHOICE of transformers

1. No-load losses (P0 ), also called iron losses (PFe )

The Total Owning Cost (T.O.C.) of a transformer may be expressed by the following formula:

No-load losses occur in the core material due to hysteresis and eddy

T.O.C. = purchase price + (P0*0 ) + (Pk*k )

currents, and are present almost continuously while the transformer is connected to the electricity supply (i.e. 8,760 hours per year).

Installation and maintenance costs may need to be added to this formula. Of course the transformer with

The hysteresis losses are proportional to the product of the frequency

the lowest T.O.C. is the best economic choice in the long term. When a customer’s price inquiry gives

and the amplitude of induction to the power of x, where x varies between

capitalization values, the optimum level of losses is calculated in the design department using specially developed

1.6 and 3.5 when induction is increasing: Ph ~ f.Bx.

software. A further advantage of lower no-load losses is the fact that the level of noise generated is usually significantly lower, due to the lower flux density.

Eddy current losses are proportional to the square of the product of the frequency, the amplitude of induction and the thickness (d) of the mag2

Thus it is often economically justifiable to replace older transformers with high loss levels by the new generation

netic steel: Pf ~ (f.B.d)

of low-loss transformers, since their lower losses ensure a significant return on investment after only a few years.

2. Load losses (PK ), also called copper losses (PCu )

If the no-load energy losses are capitalized at a very high level, then amorphous metal core transformers become an attractive alternative. The no-load losses of this type of transformer are some 75% lower than those

Load losses occur in the windings, the connecting conductors and the

of an equivalent transformer with a conventional magnetic steel core.

tank. They are caused by the effects of Joule’s law (Ohmic losses), eddy currents and flux leakages. Ohmic losses are equal to the product of the 2

square of the current and the resistance of the conductor: Pj = R.I

Total Owning Cost (T.O.C.) = purchase price + (P0*0 ) + (Pk*k ) These losses are proportional to the square of the load, thus a load of 50% of the rated load produces load losses equal to approximately 25% of the rated full-load loss values. Within certain limits, a manufacturer can increase or reduce no-load and/or load losses by varying the current density, the induction level of the

T.O.C.

=

Total Owning Cost

P0

=

guaranteed no-load losses (Watt)

Pk

=

guaranteed load losses (Watt)

0

=

capitalization value for no-load losses stated by the customer (euro/Watt)

k

=

capitalization value for load losses stated by the customer (euro/Watt)

magnetic steel, the choice of material for the conductors and the core, etc. Evaluation of two distribution transformers, each with a nominal rating of 630 kVA but with different loss levels: Lower losses always involve the use of a larger quantity of material and/or higher-cost materials, thus raising the price of the transformer. However, its

Tr. 1

630 kVA

P0 =

Tr. 2

630 kVA

P0 = 1,150 Watt

energy consumption, and therefore running costs, will be lower. In order to

This value, expressed in monetary units per watt, allows financial evaluation (or capitalization) of the losses and is therefore called “capitalization value”. The capitalization values for no-load losses (0 ) are considerably higher than those for load losses (k ), which is logical

Pk = 5,750 Watt Pk = 8,400 Watt

0 = 4.25 euro/Watt k = 1.15 euro/Watt

P0

Pk

price

P0*0

Pk*k

T.O.C.

Watt

Watt

euro

euro

euro

euro

Tr. 1

870

5,750

7,550

3,698

6,613

17,861

Tr. 2

1,150

8,400

7,000

4,888

9,660

21,548

make an economically valid comparison of transformers with different loss levels, a value reflecting the cost of the energy losses has to be introduced.

870 Watt

This table clearly illustrates that the lowest purchase price does not necessarily reflect the best economic alternative.

because no-load losses occur continuously.

22

23

Low-noise transformers

A growing importance is attached to the negative aspects of technology on people and the environment in modern society. The potentially disturbing or hazardous aspects of transformers include:

In many countries, there are strict limits on the noise levels which may be generated by transformers in both urban and rural locations. The primary source of

Noise pollution.

the

noise

produced

is

the

Land pollution, due to escaping oil caused by

alternating magnetization of the

leaks or explosions.

core steel, while the current-

The use of PCBs (polychlorinated biphenyls) -

carrying windings contribute only

very toxic chemicals - in cooling liquids.

a limited amount. Pauwels uses a variety of techniques to limit noise

Electromagnetic fields: the effects of such fields on human beings and instruments are not yet

levels drastically, the most important being to reduce the induction in the

fully understood.

core, producing an appropriate core shape (e.g. the step-lap method), a

Energy losses in transformers. Even though

special clamping construction and the use of low-resonance tanks, etc.

transformers are generally highly efficient, as explained earlier, some energy is lost in the

This enables Pauwels to build transformers with extremely low noise

transforming process. This energy also has to

levels, down to within what we refer to as “whispering level”. Building

be generated somewhere and this generation

transformers with noise levels below 30 dBA (sound pressure at a distance

process has its own consequences, including

of 1 m) is an illustration of this. Pauwels has also carried out pioneering

a rise in emissions of harmful combustion gases.

work in the field of measurement of transformer-generated noise.

Visual pollution to the environment caused by

Engineers from our Research and Development department have refined

the siting of transformers and substations

the noise intensity method (introduced by Brüel and Kjær in the early

without due consideration to the impact

eighties) and applied it to transformer noise measurement. This method

on the landscape.

now has official recognition and is described in the IEC 60551 standard. The noise intensity method allows more accurate measurement by eliminating disturbances due to the near-field effect (*) and other nearby

Transformers and

THE ENVIRONMENT

sources, and also enables the noise generated by the transformer to be measured when the ambient noise level is far in excess of the transformer noise. This clearly makes the noise measurement and evaluation process much simpler, while also allowing frequency analysis. Besides frequency analyses, Pauwels laboratories can also carry out vibration and resonance analyses.

Reference table dB(A) 20

rustling of leaves

70

30

whispering

100 heavy machine shop

40

library

120 rock concert

60

normal conversation

130 pain threshold

traffic noise

(*) Very close to a sound source, the air acts as a mass-spring system which stores the energy. The energy circulates without propagating and the region in which it circulates is called the “near-field”. Only sound intensity measurements for sound power determination can be made here.

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Transformer filled with synthetic organic esters in accordance with the IEC 61099 standard

Land pollution: the importance of leakproof tanks and environmentally sound coolants

Radical exclusion of PCBs Pauwels operates a consistent, stringent PCB (polychlorinated biphenyl) monitoring policy: the test certificate

An escape of coolant from the tank can cause land pollution and possibly

delivered with each Pauwels transformer certifies that its PCB content is less than 1 ppm (part per million).

lead to the danger of fire when a spark or flame is present at the same

Oil deliveries or transformers returned for overhaul or servicing are never accepted before an oil sample analysis

time. The “Wassergefährdungsklasse” or “WGK” (water pollution class) of

has provided conclusive proof that the liquid is PCB-free.

a liquid provides a measure of the threat posed by the liquid to underground and surface water. This classification is based on the

Pauwels’ customer service department acts as an intermediary for the collection and treatment of transformers

biodegradability of the liquid. Most mineral oils and all silicone liquids are in

filled or contaminated with harmful PCBs by introducing the owner to officially accredited specialist waste disposal

category 1, while esters are more biodegradable and classified as

companies.

category 0. A WGK of 0 is normally specified only when the transformer is to be located in the vicinity of a water extraction area. Fire regulations and

Electromagnetic compatibility

fire insurance policy conditions often also lead to the choice of these somewhat more expensive coolants. Their higher flash points and ignition

All current-carrying conductors and machines create an electromagnetic field which can have an interfering effect

temperatures enable the transformer to be operated without excessively

on sensitive (e.g. electronic) equipment. Therefore all products must be made with the highest possible

stringent stipulations in respect of sprinkler installations or drip pans to

electromagnetic compatibility (EMC): they must not produce a disruptive field or be affected by other fields in their

catch leakages, thus yielding significant reductions in installation costs.

vicinity. Pauwels liquid-filled transformers are ideal in this respect: their tank acts as a natural electromagnetic screen, reducing the effect of external fields to negligible values.

The ingenuity of our designers, the craftsmanship of our welders, the robustness of the materials we use and the multiple quality control procedures carried out to check for leaks during the production process all combine to ensure the long-term leak-free quality of our tanks.

Recyclable materials

C

Optimized use of raw materials Extensive optimization has enabled Pauwels to succeed in building very compact transformers. Today’s 1,000 kVA model is the size of the 630 kVA transformer of just a few years ago, for example. This optimization and rationalization have simultaneously yielded significant savings in raw materials (copper, aluminium, magnetic steel, metal, etc.) and coolants.

One of the central themes of the Pauwels corporate policy is the quest to reduce raw material consumption to a minimum. Waste materials from the production process are collected and carefully sorted for sale as scrap for recycling. A similar policy is followed by the specialist companies breaking old transformers for scrap. Today’s Pauwels transformers are designed to facilitate the highest possible degree of recycling. Over 90% of the materials used can be recovered by simple procedures. Special attention is paid to environmental impact even in the choice of the

Lower consumption of primary energy sources, due to the use of transformers with low losses Pauwels also contributes to a cleaner and safer environment by offering low-loss transformers. Electricity utilities using low-loss transformers will clearly need to generate less electricity to satisfy the same energy demand. Generating less electricity involves lower consumption of primary energy sources (coal, gas and oil), thus reducing emissions of the harmful combustion gases which cause phenomena such as acid rain and depletion of the atmospheric ozone layer.

smallest components, as illustrated clearly by the use of asbestos-free gaskets, for example.

Transformers and

THE ENVIRONMENT

✖ Evolution of the weight of a 400 kVA transformer

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DESIGN specifications and standards

Pauwels transformers are designed to meet all the most recent national and international standards such as IEC, ANSI/IEEE, CEN/CENELEC, BS,

LOGISTICS

The complex chain of processes, from initial offer through to final delivery, is managed by the logistics department. In view of the strongly international

character

of

the

DIN/VDE, NEMA and CSA, etc. Within the distribution transformers

Pauwels Group’s business, this

product group, the product development department is responsible for

requires flawless organization and

managing and updating the internal standards database. Engineers from

extensive experience.

this department play an active role in a wide range of engineering standards committees and international working groups, where they are able to keep up-to-date with the latest developments in technical standards.

design drawings stock control purchasing

reservations

planning factory distribution of drawings

delivery of materials drawings & planning

production

test bay final control

customer info order status

Pauwels has designed standard transformer models for a large number of markets, each fully meeting or even exceeding the national standards and requirements of each market. Other transformers are standardized to the specifications of individual major customers such as electricity utilities,

Quality logistics management produces fast delivery times, punctual and complete delivery, and correct and rapid

large contractors and heavy industrial companies. All other transformers

handling of istrative procedures. Careful construction of the Group’s computer network and information

are designed individually to meet the customer’s specific requirements.

systems has built a superbly efficient information flow system connecting all the various departments of the Pauwels organization. The group operates a Just-In-Time material flow system, optimized using specialized

This approach has enabled Pauwels to achieve extensive automation

computer software, automated warehousing systems and firm contracts with accredited suppliers.

in the design and construction areas, leading directly to an ability to

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offer attractive prices and fast delivery. The high degree of customer

Pauwels supplies transformers to customers in over 135 countries around the world. This requires the assistance

satisfaction and the numerous accreditations achieved after stringent

of specialist transporters with wide experience in multi-mode transportation. In addition to the complexities

approval procedures illustrate the success of the Pauwels product

specific to long-distance destinations, complicated logistical problems can arise when transformers have to be

development strategy.

installed in locations where access is difficult.

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The high reputation of Pauwels transformers is a product of the comprehensive attention to quality.

Commitment to quality runs throughout the company: Research and Development, Design, Production, Quality Control, Logistics and istrative Services. The Human Resources department maintains an ongoing programme of quality consciousness and quality enhancement training for all the company’s employees.

Operating a certified quality system to ISO 9001 standards is merely a precondition for achieving consistent quality. Within the Pauwels organization, quality control is carried out at each design and production phase through a self-assessment system. Each workstation has a description of the tasks to be carried out and the accompanying quality control procedures. A component is ed on to the next workstation only after the worker concerned has carried out the specified quality control procedures and approved the component. Any material or component failing a quality test is rejected immediately. Thus each worker checks his (her) own production and regards the next workstation as his (her) customer. The quality department monitors all quality control documents and carries out additional inspections at strategic points in the production process. This allows immediate action to be taken and any modifications to be made as required. Materials purchased from approved suppliers are subject to goods inwards checking which can vary from simple identification to comprehensive testing in the physical chemistry laboratory. All raw material and component suppliers must meet ISO standards. Each transformer is subjected to the full range of specified tests before release to the customer. Testing to IEC or ANSI specifications includes all routine tests and measurements and may be complemented by type and/or special tests. These supplementary tests are carried out either on the customer’s request or as part of an internal sampling procedure to ensure continuous quality monitoring. All testing is performed within the company with the exception of dynamic short-circuit tests, which are contracted out to accredited external laboratories such as KEMA, LABORELEC, EDF, CESI, FGH and other independent testing institutions. Many customers have carried out quality audits and inspections in the various Pauwels facilities and repeat them regularly to assure themselves of a consistently high quality level. In addition to the national and international standards, e.g. IEC, ISO, etc., some customers also use their own measuring and testing schemes which often involve tests in independent laboratories.

QUALITY ASSURANCE certified to ISO 9001 and based on self-assessment

SALES AND

AFTER-SALES

CUSTOMER SERVICE

service

Sales The Pauwels Group sales organization is structured to ensure the shortest possible lines of communication between customers and Group companies. This goal is achieved by working through a network of small, efficient sales offices and specialist representatives with an expert knowledge of local conditions and of the customer’s requirements. Sales offices operate in , Italy, the USA, Colombia, Indonesia, Saudi Arabia, the United Arab Emirates, Nigeria and Zimbabwe.

Customer service

The Pauwels organization offers an extensive range of services to

Inquiries and orders are handled by multidisciplinary customer service teams, where technical, commercial and

customers after delivery of their transformers, including:

istrative skills are blended exactly as needed to deliver what each different customer type demands: the right product at the right time at the right price.

a 24-hour helpline, with teams on permanent standby to carry out all possible urgent

Each customer service team is therefore specialized in processing inquiries and orders with very specific

repairs, etc.

characteristics in of customer requirements and/or transformer types. This results in a high degree of

maintenance and repairs to transformers either

overall customer responsiveness illustrated by timely return of fully detailed quotations, high delivery reliability

on-site or in our well-equipped workshops

with orders and fast information exchange throughout the contract period ensuring well informed customers.

oil sampling

- to assess the insulating condition of the liquid

The customer service teams work closely together with the Logistics Department (Purchasing, Planning, Transport and Invoicing) and the After-Sales Department in order to guarantee the highest possible levels of

- to analyze dissolved gases

customer satisfaction.

- to determine PCB content drying, degassing and filtration of the coolant oil cleansing to remove PCBs supply of spare parts provision of replacement transformers modifications such as: - connections (e.g. bottom entry or top entry cables) - replacement or conversion of accessories such as Buchholz relays, liquid level indicator gauges, pressure relays, etc. overhaul and replacement of the off-circuit tap changer increasing transformer power capacity by converting to forced cooling (installation of fans, etc.) training for customers’ maintenance staff advice to customers on how to operate and Production facilities

maintain their transformers

Subsidiary companies Regional offices Agents & sales s

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