Group

Overview

AM

EM

BE

R

OF

T H E A L T R

ON

GR

OU

PALTRON

Transformers

Group Overview

Powertech Transformers is the only manufacturer of largehigh voltage transformers in Africa

The company is 80% owned by Power Technologies (Pty)Ltd and 20% by Power Matla. Power Technologies (Pty)Limited is a wholly owned subsidiary of Altron (AlliedElectronics Corporation Limited) and is focused on deliveringadvanced technologies for the creation, management,distribution, storage and use of electricity across industries.The company's core businesses include the reliable deliveryof high quality technical equipment, support and engineeringexpertise to support demanding client requirements acrossa range of specialist applications.

The power transformer business, which originated in theSwedish ASEA stable (now part of ABB), was established inSouth Africa in 1944 and has become dominant in that market.For a period from 1988 to 1992 the company was known asBrown Boveri Technologies (BBT) before the name changedto ABB Powertech Transformers in 1997. In October 2007,Powertech announced its intention to buy the 50 %shareholding that it did not own in its joint venture companyABB Powertech Transformers, from ABB South Africa for aconsideration of R 320 million. The Competition Tribunal gavetheir unconditional approval of the transaction as of 26 March2008, thereby satisfying the only remaining conditionprecedent.

The distribution transformer business, partly originated inthe Swedish ASEA stable (now part of ABB) in 1944 andwithin Desta Transformers, in 1953. Desta Power Matla,commenced operation in July 1999 in the original DestaTransformers premises in Booysens, Johannesburg. Otheroperations were situated in Pretoria West and Cape Town(previously Power Engineers). In 2009 the Distribution Divisionof Powertech Transformers came about when Desta PowerMatla (DPM) joined forces with Powertech Transformers(PTT). At the same time, PTT’s shareholding changedsignificantly. Power Matla, DPM’s BEE partner of many years,increased its investment in the transformer industry by buyinga 20% stake in the newly formed Company.

With capacity in excess of 10000MVA per annum and accessto the most advanced technology available, the company isideally positioned to service the whole sub-Saharan Africatransformer and shunt reactor market.

Power Transformer DivisionDesign

Our design expertise – electrical and mechanical

Power Transformers’ Engineering Department has a vibrantdesign team consisting of an Electrical Design and a MechanicalDesign Section. The collective experience of the designteams is more than 50 years. These designers have experienceranging from Small Power Transformers (SPT – < 60MVA, <132kV) up to Large Power Transformers (LPT – 800MVA,400kV) including all aspects of auxiliary control circuit applicationand layouts. In addition to the Power Transformer designexperience, Powetech Transformers has design experiencefor designing large GSU’s, reactors and SVC transformers.Design records dating back to the 1960’s are available to ourdesigners for cross reference purposes.The design software available to the designers is a state ofthe art integrated design system. This includes windingdesign and optimisation, graphical electromagnetic field lineplots, temperature analysis, short circuit stress calculationsto full 3D CAD modelling of the transformer and itscomponents. This design tool available to our designersallows them to customise each power transformer to a specificcustomer’s requirements.Customer drawings are prepared for tender designs andfinalised once all the customer requirements are clarified onorder placement. All electrical and mechanical designs areput through an internal design review process. Externaldesign reviews by customers are also allowed for in thedesign process.If a detailed customer specification is not available, PowertechTransformers can offer a cost effective design based on therequirements of IEC 60076 family of product standards.Powertech Transformers can also provide completed technicalschedules for tender evaluation purposes based on the IECrequirements, should it be required from the customer.

The design margins for dielectric, thermal and short circuitEach power transformer is uniquely designed based on thespecific customer’s requirements. Where design marginsare not specifically specified by the customer, the designmargins are based on IEC.These design margins are specifically aimed at reducing therisk of transformer failure during short circuits and prolongingthe life of the transformer from a temperature rise and hot-spot point of view. Specific margins are determined andshared with the customer during the external design reviews.

02

Core Construction

Core-type construction is used for all power transformers

Cold rolled grain oriented steel has long been employed intransformer cores because of its superior characteristics,enabling the use of higher flux densities with consequentsaving in material. Over the years steels of continually lowerloss have become available.

Cold-rolled grain oriented silicon steel laminations are usedto ensure low no-load losses and suppression of vibrationsresulting in lower noise levels. Using stepped sheet widthshelps in achieving an almost circular cross section of thecore. Advanced step-lap core construction technique achieveprecise core stacking with step lap joints at the corners. Thistechnique also helps in stacking at precise angles therebypreventing the formation of air gaps in the core joints, whichotherwise could lead to increased losses and noise generation.Core form structure is used without any through bolts in thelimb or yoke portion. The core limb is wound with conductingresin impregnated glass tape to give rigidity to core and toget a minimum uniform circular section for inner winding. Toavoid internal mechanical stresses, the core is set upright inthe stacking device itself.

Super oriented steel commonly called Hi B (grade MOH) canoperate continuously at flux densities close to 2 tesla (absolutemaximum) and provides significant reductions in no-load loss,magnetizing current and in sound levels. The steel is importedin standard width coils and slit to required plate widths in theworks. It has to comply with ABB specification, which includesrequirements for losses, ageing, insulation, space factor,waviness and burrs.

The use of MOH material, coupled with the proven designfeatures of 45°'a1 mitred and interleaved joints, boltlessconstruction, and judicious introduction of cooling ducts asthe size increases, enables cores to be worked at high fluxdensities.

10% overfluxing (if specified) can be accommodated withoutany thermal instability, excessive noise or vibration, or otheradverse effects.

Further improvements in both loss and sound level havebeen achieved using step lap cores, which are part of theTrafoStar design concept

Windings

Conductor material is verified to meet the required tolerancesbefore and after in-house paper insulation covering

Windings are designed to ensure high short circuit withstandcapability, uniform surge voltage distribution and effectiveheat dissipation which are critical to transformer reliability.The disc type design of the high voltage windings ensuresbetter short circuit withstand capability, uniform surge voltagedistribution and effective heat dissipation. These windingscan be used with different designs for both small and largetransformers up to the highest voltage levels. Using thelatest developments in winding technology, we use “voltagestabilised” disc windings for the high voltage side. Theindividual winding turns in each group of discs are interleavedthereby increasing the winding series capacitance to getuniform voltage distribution.

Rectangular electrolytic copper strip covered with paper ismainly used for winding conductors in the power transformersmanufactured in Pretoria, although more usage of continuouslytransposed conductor is now evident.

The strip is purchased from local producers and supplied ondrums ready for paper covering. It has to comply withPowertech Transformers’ specifications as regards purity,dimensional accuracy and surface finish and this is checkedon receipt. A higher standard of finish is specified if thecopper is for use in high voltage windings. The copper issupplied fully annealed or to the required hardness, asspecified.

Paper made from pure sulphate pulp is used for covering theconductors. Supplied by Munksjo of Sweden, it has to meetstrict ABB specification requirements regarding compositionas well as mechanical and electrical properties. The paper isdelivered to Pretoria in large rolls and slit to the standardwidths used in the works.

Windings are designed and manufactured to withstand theelectrical, mechanical and thermal stresses that will occurduring service. In certain high-current applications, continuouslytransposed conductor (CTC) is used to reduce losses, and,when coated with an epoxy coating, to improve mechanicalstrength against short circuit forces.

Assembly & Processing

The core and windings are assembled using insulation materialof the highest quality

Both the medium and large transformer assembly lines atPowertech Transformers are equipped with motoris edpersonnel platforms capable of vertical and horizontal travelwhich allow the work of assembly and connecting up to becompleted with minimum strain on personnel.

The core and windings are assembled using insulation materialof the highest quality. Where required, correctly positionedmagnetic shunts ensure the collection of stray flux preventingunwanted hotspots in the clamping structure and tank walls.Jointing, both in the winding and external, is by high frequencywelding, which is extremely rapid and reliable. These jointsare taped and the leads fixed in position to withstand anystresses during test and service conditions.

Windings are dried under vacuum and, on large units, oilimpregnated before assembly.

The completed windings are dried and large windings are oilimpregnated to reduce moisture absorption during laterassembly processes. The windings are then adjusted to apredetermined height at a controlled axial pressure in ahydraulic press. All windings for each transformer are adjustedto the same height, so that when they are finally assembledon the complete transformer they will be clamped at thesame pressure as before. The complete active part isprocessed in an autoclave to obtain less than 0,5% moisturecontent. This process is extremely efficient and fast as thekerosene vapour is sprayed onto the active part and givesup its latent heat at the same time having a washing effecton the windings. The process consists of holding thecomponent under vacuum and heating it by means of hotkerosene vapour as mentioned above. Any moisture presentin the insulation is converted to water vapour in this lowpressure, heated environment and is then drawn off withuncondensed kerosene vapour at a particular stage of thedrying cycle.

Within the prescribed time following the drying cycle, pressureis applied to the windings and the unit is tanked and filled,under vacuum, with heated, degassed and purified oil.

Cooling

We offer a wide range of cooling methods

A wide range of cooling methods such as ONAN (oil natural,air natural), ODAF (oil directed,air forced), ONAF (oil natural,air forced), OFAF (oil forced, air forced), OFWF (oil forced,water forced) or combinations thereof. Forced cooling canbe activated by temperature or loading pattern.

The cooling equipment collects hot oil at the top of the tankand returns cooled oil lower down on the side. The coolingarrangement can be seen as two oil circuits with an indirectinteraction, one inner and one outer circuit. The inner circuittransfers the loss energy from the heat producingsurfaces to the oil. In the outer circuit the oil transfer theheat to a secondary cooling medium. The ambient air normallycools transformers. It is possible to build air coolers withforced air circulation more compactly than coolers with naturaldraught. However, such a cooler also has fairly high impedanceto the oil circulation in the internal circuit, which necessitatesthat the oil be pumped through the cooler. For built intransformers, e.g., deep underground power caverns or insome industrial application oil to water heat exchangers areused: as in such cases, sufficient air for cooling may not beavailable. The system also permits small physical dimensions.The disadvantage of the compact design is that auxiliarypower must always be available. Present standards give cleardefinitions of the different types of cooling together withspecial designations.

A given transformer can have a combination of cooling typesto permit a change in the type of cooling e.g. ONAN/ONAFetc. Pumps as well as fans sometimes suffer breakdowns.It must be possible to exchange such components withoutemptying the transformer or even taking it out of service. Allcooling circuits should therefore be provided with necessaryvalves for shutting off each separate oil circuit.The letter 0 Is used for mineral oir and insulating liquid withfire point to 300º C. The letter K is used for insulating liquidwith fire point > 300º C. The letter L is used for insulatingliquid with no measurable fire point. They almost consistbasically of number of flat passagesof edge welded plates connecting a top and bottom header.It is possible to make the radiators slightly higher than thetank so that the top header has a swan-necked shape; thishas the added benefit that it also improves the oil circulationby increasing the thermal head developed in theradiator. The radiators have a venting plug in the top headerand a draining plug in the bottom header. Radiators are almostflanged direct to the transformer tank or to the headers infreestanding cooler banks through a butterfly valve permittingindividual radiators to be shut off and even easily removed.

FansIt is also possible to suspend fans below or on the side ofradiators to provide a forced draught, and achieve the ONAFcooling arrangement. This might enable the transformerloading capacity to be increased by some 25%. The radiatorshave to be grouped in such a way to obtain coverage by thefans.

04

Tanks

Computerised tank designs are fabricated from mild steelplate

The tank is primarily the container for the oil and a physicalprotection for the active part. It also serves as a supportstructure for accessories and control equipment.

Production of tanks, etc. can be divided broadly into twoparts, namely surface preparation and cutting to size of theraw material, followed by actual manufacture of the finishedproduct. Standard size plates delivered from various localsuppliers are initially stored in the steelyard. At the start ofmanufacture the plates are shot blasted in an automaticmachine resembling a rolling mill. The plates pass from aroller table through the shot blast chamber and onto a secondroller table on the other side. The aim is to achieve a 70%finish and the degree of finish is determined by the feed ratethrough the machine. On the reverse pass all loose shot iscleaned from the plates which are then automatically fed tothe flame cutting shop by the use of further rollers.

Computerised tank designs are fabricated from mild steelplate. Welds are dye-penetrant tested to ensure that thereare no leaks and specific joints, which may be stressed duringhandling and transport, are ultrasonically tested. Stiffenersare added at calculated intervals to make the tanks vacuumand over-pressure proof. Tank interiors are painted a lightcolour to improve visibility. The tank exterior is treated andpainted to customer requirements. Nitrile O-ring gaskets forpipe joints and inspection covers are a standard feature inorder to avoid oil leaks developing later during service. Tankmain covers are generally welded, but these can be offeredas bolted covers if specifically requested. Where required,non-magnetic shielding is applied to the tank interior toprevent heating. Only accessories from approved suppliersare used on our transformers.

Before oil filling, the tank, with the active part inside, isevacuated in order to remove all air that would reduce thedielectric strength of the transformer insulation. Thereforethe tank for large power transformers for system voltages110 kV and higher is designed to withstand vacuum insidethe tank with a minimum of deformation. The leak rate withboth positive and negative overpressure is verified by suitabletests. Transformers for lower system voltages and with aless complicated insulation system may have tanks whichdo not withstand vacuum inside the tank. Before renovatingsuch transformers, the manufacturer should be contacted toclarify whether the tank is vacuum-proof or not. To keep thetank dimensions within the specified transport profile and,at the same time, enclose the active part in the tank in withnecessary insulation clearances and still obtain a reasonablysimple design often makes the designer's task a considerablechal lenge when designing large transformers.

Painting

Our painting systems

All transformers are painted and coated in accordance withdocumented in-house painting specifications and procedures.All new transformers, irrespective of whether they areoperating in non-corrosive or corrosive environments, arecoated in accordance with Powertech Transformers corrosiveprotection specification. The customer requesting specificpainting systems are also provided for.

In addition to the standard corrosion protection paintingsystem, a zinc-metal spray coating can be applied on customerrequest.

All external surfaces of the transformer and accessories arecolour coded in accordance with the Natural Colour System(NCS codes) to customer’s unique requirements.

10

Material Selection

Our material selection and control

Powertech Transformers prides itself in the ability tomanufacture most of the transformer structural componentsin-house. Powertech applies strict control of incoming rawmaterial from pre-qualified suppliers. All incoming goods arequality controlled and checked before it is released into thesub assembly manufacturing lines. Where certification isrequired, the raw material is send to Powertech Transformerson-site SANAS accredited laboratory for material analysis,verification and certification. Any non-conforming product isrejected and returned to the supplier for rectification.

Components used on the transformers are all sources frompre-qualified suppliers locally and internationally. Before asupplier is used, the capability of the supplier is assessedtaking their technical ability, quality control system, financialviability and other commercial factors into account.Supply level agreements are put in place with the key suppliersto ensure availability of stock and continuity of supply.Where possible local suppliers are preferred and a numberof enterprise development initiatives are considered fordevelopment of small independent business units.

1006

Quality & Testing

Quality is built into our products

An up-to-date quality assurance system is well in place thatcovers all aspects involved in the production and testing ofall transformers. Quality checks are carried out on all materialand processes at various manufacturing stages to ensurehighest quality standards.

Quality is built into all Powertech Transformers’ products andacceptance testing is one of the final steps of the qualitycontrol measures. Powertech Transformers is an SABS ISO9001 listed company and has a proven quality control systemas well as being SABS 9001-2000 certified. Furthermore thePowertech Transformers factory in Pretoria West, has ISO14001-2004 accreditation for its environmental awarenessand the ISO 18001 accreditation for health and safety.

Continuous improvement is stressed at all levels within theorganisation which keeps everyone focused on manufacturingquality transformers.

The test equipment at Powertech Transformers Pretoria isdesigned to handle the largest high voltage transformerscapable of being produced there.

This modern testing facility includes an impulse generator,precision power analyser for transformer loss measurement,PD analyser and temperature data logger to carry out routineand type tests accurately. A special motor-generator set-upis used to test transformers at 50Hz and 60Hz similar to theexact operating frequency which will enable us to obtainaccurate results. In addition to all routine tests, special andtype tests that can be carried out in-house include:Temperature rise test, Lightning & switching impulse test,Induced over-voltage test with PD measurements,Measurement of zero sequence impedance, Noise levelsModern data collecting systems and high-end testinginstruments allow easy access to accurate results obtainedfrom our test measurements. Our transformers are subjectedto all the necessary routine tests in accordance with BIS orIEC, ensuring they withstand conditions beyond normaloperating conditions. The extremes to which the transformersare tested are a measure of the highest standards in qualityand reliability built into every transformer. Three-phasetransformers of 800MVA 400/275/22kV, single phase autotransformers of 333MVA and the same voltage ratio and795MVA 22/420kV double wound generator transformershave been successfully tested. The full 100% of the losseswere supplied during the temperature rise tests. Transformersare tested according to IEC requirements. The testing facilitycan also test transformers according to ANSI specifications.

Transport, Installation & Services

We closely supervise the transport, installation andcommissioning of our product to ensure customer satisfaction

Powertech Transformers closely supervises the transport,installation and commissioning of product to ensure customersatisfaction. Transformers are transported either oil or nitrogenfilled.

After the Factory Acceptance Test (FAT), the transformer isdisassembled and made ready for shipping. Depending onthe size and voltage class of the transformer more or less ofthe equipment on the transformer is dismantled prior totransport. Normally coolers and high voltage bushings aredismantled prior to shipping and transported separately.Usually large power transformers are shipped without oil.When the transformer is shipped without oil, the transformeroil is transported in a tank lorry suited for this purpose and/orin barrels. During transport the transformer is filled with dryair with a certain overpressure in order to avoid moistureabsorption in the insulation. Before leaving the factory atightness test is performed. The weight limit for when thetransformer is transported with or without oil depends onseveral factors like the transport facilities (trucks, boat,cranes),weight limits on roads, bridges, etc.

For transformers with a transport weight above 20 tons,special transport is required. During transport, the transformershould be equipped with an impact recorder. This is to recordif anything should happen to the transformer during transportand handling at site. Some recorders register impacts (G-forces in x, y and z-directions) and exactly when impactsoccur. This is essential in the event that the transformer hasbeen exposed to abnormal impacts and to determine whichparty has the transport responsibility at the time of the impact.The recorder shall not be dismantled and the recording finallyread before the transformer is at its final destination.

Once installed, transformers are filled under vacuum withhighly purified transformer oil. Powertech Transformers alsooffers a wide range of services including specialist technicaladvice and tap changer maintenance tra ining.

Components & Their Suppliers

We apply strict control of incoming raw materials

Powertech Transformers prides itself in the ability tomanufacture most of the transformer structural componentsin-house. Powertech Transformer applies strict control ofincoming raw material from pre-qualified suppliers. Allincoming goods are quality controlled and checked before itis released into the sub assembly manufacturing lines. Wherecertification is required, the raw material is send to PowertechTransformers on-site SANAS accredited laboratory for materialanalysis, verification and certification. Any non-conformingproduct is rejected and returned to the supplier for rectification.

Components used on the transformers are all sources frompre-qualified suppliers locally and internationally. Before asupplier is used, the capability of the supplier is assessedtaking their technical ability, quality control system, financialviability and other commercial factors into account.Supply level agreements are put in place with the key suppliersto ensure availability of stock and continuity of supply.Where possible local suppliers are preferred and a numberof enterprise development initiatives are considered fordevelopment of small independent business units.

1210

Laboratory & Transformer OilTesting

Our laboratory at Pretoria West has been in existence since1973

The laboratory at Pretoria West has been in existence since1973. The main activities of the laboratory are testing ofmaterials for transformers and calibration of instruments.The testing of transformer oil forms a large part of the testingactivities, and this service is also offered to external companies.Calibration work is performed both in-house and for externalcustomers.

Factors affecting the health and life of power transformers

The three main components subject to deterioration andcontamination in a transformer are the paper, which is usedfor conductor insulation; the pressboard, which is used forthe major insulation and winding support; and the insulatingoil.

Water, air or gas bubbles, particles of different origin, oxygenand oil ageing products are agents of degradation; thereforeit is important that the oil in the transformer is testedfrequently.

The testing of transformer oil is part of a preventativemaintenance plan, also known as condition monitoring. Theoil inside a transformer forms an integral part of the insulationsystem, but is unfortunately subject to quick deterioration ifthe preventative maintenance schedule is not adhered to.Adverse load conditions also affect the oil. It is thereforecommon practice to have the oil tested annually under normaloperating conditions and more frequently when faults aresuspected. Certain tests also give an indication of thecondition of the transformer itself and, if interpreted correctly,and acted upon, can prevent failure or unnecessary outages. The laboratory is well equipped to perform the majority ofrequired tests related to condition monitoring, using the bestequipment and techniques available internationally. Thelaboratory personnel have in excess of 30 years experiencein evaluating techniques used in assessing the health oftransformer. This includes but is not limited to transformeroil testing, cellulose testing and various material analysis.

1008

Distribution Transformer Division

The distribution transformer division has factories in Pretoria,Johannesburg and Cape Town

We are able to supply the following range of distributiontransformers:

• Small Pole Mounted Distribution Transformers 16kVA –100kVA up to and including 36kV

• Medium Distribution Transformers 200kVA – 3150kVA upto and including 36kV

• Large Distribution Transformers 4MVA – 20 MVA up to and including 132kV

• Miniature Substations 200kVA – 1600kVA up to and including 33kV

• Neutral Earthing Resistors / Compensators / Auxiliary Transformers up to 960A for 10s and LNER’s up to 2000Afor 30s

Small Distribution Transformers

Characteristics

Range: Pole mounted - 16kVA to 100kVA with open bushingGround mounted 16kVA to 100kVA with cable box bushing

Tank Construction: Sealed welded cover or sealed boltedcover

Cooling: ONAN

Mounting Arrangement: Single pole mounting with bracketor Flat under base for pole platform mounting

Tappings: Off-Circuit Tap Switch (OCTS) up to 36kV

Fittings: Lifting lugs, earth terminal, surge arrestor bracketsor arcing horns, rating and diagram plate, drain valve whenspecified

Standards: BS 171 IEC 76 and SANS 780

Medium Distribution Transformers

Characteristics

Range: 200 – 3150kVA

Primary Voltage: Up to and including 36kV

Tappings: Off-circuit Tap Switch (OCTS)

Terminations: HV outdoor open bushings, LV outdoor openbushings, alternatively HV and LV cable boxes, mineral oil toIEC 296 and SANS 555

Tank Construction: Sealed welded cover (up to and including1000kVA) or sealed bolted cover (up to and including 1000kVA)or free breathing (1250KVA upwards)

Cooling: ONAN

Mounting Arrangement: Flat under base or Skid base withor without rollers

Fittings: Lifting lugs, earth terminal, surge arrestor bracketsor arcing horns, rating and diagram plate, drain valve whenspecified, jacking pads, oil temperature indicator, oil levelindicator, dehydrating breather (free breathing units only),gas actuated relay (free breathing units only), conservator(free breathing units only)

These units are designed and built in accordance with theapplicable BS, IEC and SANS Specifications and have a localcontent in excess of 70%.

Distribution transformers from 1250kVA to 20MVA are builtin our Johannesburg factory, whilst transformers rated 16kVAto 1000kVA as well as miniature substations are built in ourCape Town factory.

Large Distribution Transformers

Characteristics

Range: 4000 - 20000kVA

Primary Voltage: Up to and including 132 kV

Tappings: Off-circuit Tap Switch (OCTS) or On-load Tap-changer (OLTC)

Tapping Range: +-2.5% to +-5% (OCTS) or +5% to -15%(OLTC)

Terminations: HV and LV outdoor open bushings or HV andLV cable boxes. Mineral oil to IEC 296 and SANS 555

Tank Construction: Free breathing with welded lids, flat underbase, skid base (alternatively)

Cooling: ONAN or ONAN / ONAF or ONAF

Fittings: Lifting LugsEarth TerminalSurge Arrestor Brackets when specifiedRating and Diagram PlateDrain and Filter ValveJacking PadsOil Temperature IndicatorWinding Temperature IndicatorOil Level IndicatorDehydrating Breather when specifiedGas actuated RelayConservator

Large Distribution transformers are made in our PretoriaWest and Johannesburg factories for end customers suchas Eskom, Local Authorities, municipalities, mines andindustrial users. These units are custom built to comply withspecific customer requirements.

1010

Miniature Substations

Characteristics

Range: 200-1600kVA

Cooling: ONAN

Vector Group: Dyn11

Enclosure: IP 35 SANS 122

Tapping range: +-2.5% to +- 5% or +-3% to +- 6%

LV Compartment:Mains MCBFeeder MCB or fusesAmmetersVoltmeterStreet lighting control, when specified

HV Compartment Options: Oil ring main unit or SF6 ring mainunit.

Primary Voltage Options: 6.6kV; 11kV, 22kV or 33kV.

Housing options: Mild steel, 3CR12, galvanising

1010

Neutral Earthing Resistors

Characteristics

System voltage up to and including 36kV

Fault current and duration960A for 10s 11kV960A for 10s 22kV960A for 10s 33kV10A Continuous rating

Technical Data

The transformers comply with SANS 780 and/or IEC 76, BS171 and NRS 027.

Liquid Neutral Earthing Resistors (LNER’s) 1000 - 2000 Ampsfor 30s.

Core

Transformer cores are made of grain oriented, low loss magneticcold-rolled silicon steel

All distribution transformers cores are made of grain oriented,low loss magnetic cold-rolled silicon steel. Both sides of steelsheets are laminated with ceramic insulation. The coreconstruction is optimised for cold-rolled steel properties so thatbest parameters for magnetic circuit are obtained, i.e. minimumno-load losses and small magnetising power.

Tanks & Oil Filling

Hermetically sealed tanks

Hermetically sealed transformers incorporate a tank withcorrugated or tube radiator fins.

The transformer tank has a sturdy design that allows fornormal transportation of an oil-filled transformer without anydamage resulting from vibration.

Free breathing transformers have fixed or removable panelradiators and isolat ing valves when specif ied.

Transformers are filled with mineral oil.

Prior to filling, oil is filtered in order to obtain required electricalcharacteristics and insulating properties.

Windings & Winding Assembly

All high voltage windings are made of copper

All distribution transformer high voltage windings are madeof copper. The low voltage windings are made of copperstrip, but in certain ranges copper or aluminium foil is used.

Diamond dot paper is used for interlayer insulation on thefoil windings as it adds mechanical strength to it. Core andwinding assemblies are clamped by means of top and bottomyoke clamps.

10

Testing & Warranty

Tests

Routine tests to SANS 780 are preferred on every transformerprior to despatch:

• Measurement of winding resistance• Measurement of voltage ratio and verification of

polarity and connection symbol• Measurement of impedance voltage and load loss• Measurement of no - load loss and no - load current• Induced overvoltage withstand test• Separate - source voltage withstand test• Measurement of paint thickness• Test for effectiveness of sealing

Type tests to SANS 780 can be undertaken on request:

• Full impulse voltage withstand test• Full and chopped impulse voltage withstand test• Temperature rise test• Tank stiffness test

Special tests to SANS 780 can also be made on request

• Short circuit withstand test (subject to limitations of SABS high current laboratory equipment)

• Measurement of audio sound level

Warranty

All our products are backed by a one (1) year warranty period.

Corrosion Protection, QualityAssurance & Transport

Exterior & interior surfaces are carefully degreased

The exterior and interior surfaces of the transformer tank,cover and conservator (when fitted) are carefully degreased.Rust and millscale are removed by a process of acid picklingor phosphating.

The exterior surfaces of inland units are thereafter given acoat of high build primer, followed by a coat of high buildalkyd base full gloss enamel giving a total dry film thicknessof at least 75 μm. The method employed is either flow coatingor spray painting.

Coastal units are shot blasted and hot zinc metal sprayedprior to painting to a finish of 125μm.

The standard colour is Avocado colour C12 to SANS 1097.

All our transformers as well as our miniature substationscarry the SABS mark of approval. Our factories have receivedthe ISO 9001 version 2008 accreditation listing and as sucha stringent quality assurance programme in accordance withthe very specific requirements is rigidly adhered to. Thisensures a product of the highest quality.

We also have ISO 14001 - 2004 and OHSAS 18001-2007accreditations.

Most transformers are delivered to the customer fullyassembled and ready for operation, except for powertransformers where radiators and consevators are removed.

During transport, transformers are firmely secured to thedeck of the trailer to prevent movement and damage.

1012

Kenya Office

PT Transformers East Africa Limited

PT Transformers East Africa Limited was established in 2008as an engineering, marketing and sales company, specialisingin high voltage transformers and electrical engineeringequipment to customers in the Eastern Africa Region. Salesand marketing support to other divisional companies of thePowertech/Altron Group of companies is also provided.

Location & Markets

As a wholly owned subsidiary of Powertech Transformers(Pty) Ltd, South Africa, a regional office situated in Nairobiis established to serve customers in the Eastern Africa regionincluding Kenya, Tanzania, Uganda, Ethiopia, Rwanda &Burundi.

Services

The Kenyan based company adds value in the supply ofregional sales and marketing expertise, project management,labour and equipment/facilities for construction works,installation, testing and commissioning of projects in thefields of electrical generation, transmission and distribution.Expertise in local transportation, local financing and bankingpractices, local labour laws etc, is also of significant benefitto the group organisations.

Customer Base & Management

The company services customers in the power and waterutilities, large industrial concerns, food processing, mineralsand mining, oil and gas, transportation and telecommunicationssectors.

Head Office

1 Buitenkant Street, Pretoria WestPO Box 691, Pretoria, 0001, South AfricaTel +27 (0)12 318 9911 Fax +27 (0)86 524 4675

Johannesburg

56 Third Street, Booysens Reserve, JohannesburgPO Box 38354, Booysens, 2016Tel +27 11 835 1011 Fax +27 11 835 1717

Cape Town

Elliot Avennue, Epping 2, Cape TownPO Box 44, Eppindust, Cape Town, 7475, South AfricaTel +27 (0) 21 534 2681 Fax +27 21 534 5383

Nairobi

Chequered Flag Building, Ngong Road, LR 2251/188, Karen,Nairobi, KenyaPO Box 15370, 00509, Langata Nairobi, KenyaTel +254 (0)20 884605 Fax +254 (0)20 884604

Email: info@pttransformers.co.zaWeb: www.pttransformers.co.za

Johannesburg

KenyaCape Town

Pretoria

Power MatlaPowertech

Powertech TransformersDivisions:

Power TransformersDistribution Transformers

80 % 20 %