Powertech Transformers

Power Transformers

Small, Medium & Large

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State of the Art TransformerManufacturing Facility

Experience and Design Capability

Powertech Transformers have many years of experiencein the design, manufacturing, installation andcommissioning of small, medium and large powertransformers for various applications. Our designexperience range from Small Power Transformers (SPT– < 60MVA, < 132kV) up to Large Power Transformers(LPT – 800MVA, 400kV) including Generation Step-upUnits (GSU’s). In addition all aspects of auxiliary controlcircuit application and layout designs are also provided.

The transformers manufactured by PowertechTransformers range from standard designs in accordancewith IEC requirements to complex designs specific fora customer’s individual requirements in the mining,industrial, municipal and power utility industries acrossthe African continent and overseas.

The software available to our designers is a state ofthe art integrated design system. This includes windingdesign and optimisation; graphical electromagnetic fieldline plots; temperature analysis; short circuit stresscalculations to full 3D CAD modelling of the transformerand its components. This allows our designers tocustomise each power transformer to specific customerrequirements.

Customer drawings are prepared for tender designsand finalised on order placement. All electrical andmechanical designs undergo an internal design reviewprocess. External design reviews by customers arealso allowed for in the design process. If a detailedcustomer specification is not available, PowertechTransformers can offer a cost effective design basedon the requirements of IEC 60076 product standards.Powertech Transformers can also provide templatetechnical schedules based on the IEC requirements,should these not be available from the customer.

Quality, Health and Safety

The plant located in Pretoria (Gauteng) is a world classmanufacturing facility and boasts a fully certified ISO9001 quality management system, ISO 14000environmental management system as well as theOHSAS 18000 health and safety management system.Powertech Transformers in Pretoria also has a fullySANAS accredited metrology laboratory on thepremises.

At every stage during manufacturing, materials andprocesses are inspected by suitably qualified andexperienced inspectors to ensure all required standardand manufacturing practices are adhered to. Six Sigma(6�) systems are built into every manufacturing processin the factory to enhance the quality and itsdocumentation of our products.

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Standard Features of our PowerTransformers

High Quality Materials Sourced from Best Suppliers

Powertech Transformers prides itself in our ability tomanufacture most of the transformer structuralcomponents in-house. Raw materials and componentsnot manufactured in-house are sourced from worldclass suppliers. Procurement of material andcomponents is done from a list of pre-qualified supplierslocally and internationally who are certified to conformwith the highest standards in terms of Quality (ISO9001),Health and Safety (OHSAS 18000) as well as theEnvironment (ISO 14000) respectively.

Before a supplier is approved, their capability isassessed, taking into consideration their technicalability; quality control system; safety, health &environmental controls; financial viability as well asother commercial factors. Supply level agreements areput in place with key suppliers to ensure availability ofstock and continuity of supply. A number of enterprisedevelopment initiatives are considered for developmentof small independent business units.

Powertech Transformers applies strict control ofincoming raw material from pre-qualified suppliers. Allincoming goods are quality controlled and checkedbefore they are released into the sub assemblymanufacturing lines. Where certification is required,the raw material is sent to our on-site SANAS accreditedlaboratory for material analysis, verification andcertification. Any non-conforming product is rejectedand returned to the supplier for rectification orreplacement.

Core Design and Manufacturing

Core design principle is based on achieving the smallestactive part possible whilst achieving low noise level,low no-load losses and ensuring high short circuitwithstand capability of the overall core structure. Thebasic core design is either a three-limb or afive-limb type core. The core is composed of a circularcross-section without any bolts through the core. Thejoints are mitred and step-lap stacked.

Selection of core steel material for a particular coreranges from conventional cold rolled grain orientatedsteel (CRGO); to highly permeability steel; to laserscribed grain orientated steel based on customerspecifications for no-load losses and noise levels.

Transport restrictions on weight and dimensionsdetermine the most appropriate core type for thetransformer that is economical on losses; flux density;overall core weight and sound level.

Winding Design and Manufacturing

The transformer windings must have the ability towithstand high mechanical and electrical stressesresulting from short circuit conditions, lightning andswitching surges as well as normal overloads duringpeak hours in daily operation throughout the lifetimeof the transformer. Our windings are made of highstrength copper and guarantee high mechanical,electrical and thermal stability under abnormal conditions.This ensures the safe operation of the transformer overits lifetime.

Winding technologies are layer, helical, continuous diskand interleaved disk depending on the operating

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conditions as determined by the rated apparent power;rated voltage; network fault level as well as the climaticconditions of the site of operation and specifiedtemperature rise limits. Disk windings are suitable forhigher voltages while layer and helical windings aresuitable for lower voltages.

The conductor used on windings is oxygen free copper.The shape of the conductors is rectangular with smalledge-radii. The conductor is often divided into two ormore parallel conductor elements to reduce the eddycurrent losses within the winding.

Insulation Material

Material for the insulation structure and barrier boardsis manufactured from high quality compressedtransformer board, compacted laminated wood and/orfibre sheets depending on the application within thetransformer with regard to the electrical and mechanicalrequirements.

Elevated temperatures (hot-spots) in transformers aredetrimental to paper insulation’s longevity due to thedecomposition of the cellulose bonding inside the paperat these elevated temperatures. The result is that theinsulation between strands is reduced leading topremature insulation failure of the transformer.

For paper insulated conductor used on windings,Powertech Transformers has standardised on thermallyupgraded paper for all windings types. This ensuresan additional 10Kelvin hot spot temperature marginresulting in an extended life of the transformer.

Powertech Transformers has a fully equipped paperlapping facility for paper insulating of strip copper aswell as an insulation manufacturing facility.

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Each strand is insulated either by thermally upgradedpaper covering, or by an enamel coating, or both. Twoseparately insulated and parallel strands may sometimeshave a common paper covering. Conductor types canbe strip conductor or CTC (Continuously TransposedConductor).

Manufacturing of windings is carried out by suitablyqualified and experienced winders on vertical orhorizontal winding machines. Our winding machinesare precisely controlled to achieve constant contactpressure and winding tension.

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Insulation Oil

The mineral oil inside the transformer tank acts as aninsulation medium as well as a coolant for the windingsinside the transformer. The mineral oil used in ourtransformers complies with international standards.Only virgin oil is used (free of PCB contamination) andno re-generated oil is used to fill the transformers.

Tank Design and Manufacturing

The transformer tank accommodates the core andwindings (active part) as well as insulating oil. It servesas a support structure for accessories and controlequipment as well as acting as physical protection forthe active part. Due to its vital role the tank designmust be robust and very reliable implying the use ofhigh quality material.

The transformer tank is usually of the rigid type withremovable radiators connected by shut-off valves. Thetank shape and size are designed to optimise thequantity of material used taking into consideration theelectrical clearance requirements, structural strengthand required oil volume. The base is flat with a minimumthickness of 20mm and is determined by the liftingcapacity required for the core and winding masses.

Mild steel plates are the main building material usedin our tank, cover and conservator as well as all thepipes and fittings. However, where there is a seriousconcern with high currents e.g. around high currentcarrying bushings and, on areas where there is a threatof rust, stainless steel is used instead. Double weldingis used where oil tightness is required. Rubber or corkrubber compound is used for the gaskets on flangedconnected pipe joints/transport and inspection coveropenings and all other valves and fittings.

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Painting and Surface Treatment

Powertech Transformers has a range of proven surfacetreatments depending on the transformer site climaticconditions and application environment. All paint andcoatings are done in accordance with a documentedin-house painting system complying with strict safety,health, environmental and quality requirements.

All new transformers, irrespective of whether they areoperating in non-corrosive or corrosive environments,are coated in accordance with Powertech Transformerscorrosive protection specification. Tank external surfacesare painted with a two-component epoxy primerfollowed by a two component acrylic or polyurethanefinishing coat.

In addition to the standard corrosion protection paintingsystem, a zinc-metal spray coating can be applied oncustomer request. Other customer specific paintingsystem requirements are also provided for.

All external surfaces of the transformer and accessoriesare colour coded in accordance with the Natural ColourSystem (NCS codes) or RAL international colourstandards to a customer’s unique requirements.Separate radiators are generally hot-dip galvanised.

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Main Terminals

Customers have a choice of bushings from standardsolid porcelain oil impregnated (OIP) type bushings toresin impregnated (RIP) bushings for various applicationssuch as Oil to Air, Oil to Oil, Oil to SF6, Air to Air andAir to SF6. Our bushings are always sourced fromworld class suppliers of bushings, who comply withinternational standards and are generally positioned onthe cover.

For voltages above 52 kV, condenser type bushingswhich facilitate the electric stress control via the insertionof floating aluminium equaliser screens which arelocated in the condenser core are used. Enclosurescan be provided on the primary and/or on the secondaryside and may be constructed for cable or bus ductconnection. Transformers may also be provided withplug-in or cable box bushings.

Accessories

Depending on the type and application of thetransformer the accessories will usually include acombination of the following items either as standardor optional as per customer requirements:

• Bushings (Oil or Resin Impregnated, Oil to Air, Oil to Oil; Oil to SF6)

• Oil conservator with level indicator

• Rubber-bag with bag leak detector in the conservatorto prevent oil coming into direct contact with air

• Tap changers (oil type as well as vacuum)

• Filling and drain valves

• Oil sampling device

• Earthing terminals

• Lifting lugs

• Jacking pads

• Radiator panels

• Silica-gel breather

• Buchholz relay (GOR)

• Winding Temperature Indicators and Oil TemperatureIndicators (Analogue or Digital).

• Fibre optic probes for direct hot spot temperaturemeasurements on active part.

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• Pressure relief devices and provision for pressure purging systems.

• Provision for water cooled systems

• Impact recorders

• Separate core and core clamp earth test positions

Additional accessories can be fitted according tocustomer specifications.

Drying and Vacuum Treatment

The moisture content in oil and solid insulation canhave adverse effects on the life span of the transformersince it affects the dielectric breakdown strength ofsolid and liquid insulation. This affects the rate at whichthe cellulose ages and the propensity for bubbleevolution during overloads. In order to counteract thesenegative effects of moisture adequate drying andvacuum treatment is performed using proven technologysuch as Vapour Phase Drying and LFH (Low FrequencyHeating). Before filling, the oil is always degassed andpurified.

Testing

Every transformer at Powertech Transformers isindividually tested according to major internationalstandards as well as, in accordance with any specialtests required by the customer, and must pass all thesetests before leaving the factory. The test certificateforms part of the transformer operating manual.

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Standard Features of Powertech’sPower Transformers

SFRA (Swept Frequency Response Analysis)fingerprinting is also done before the transformer leavesthe factory and redone on site. Impact recorders areinstalled on the core as well as on the tank of thetransformer to verify adverse impacts or accelerationsin all three dimensions. Results of the SFRA test andimpact recorder data are made available to ourcustomers.

Standard and Complex Small Power Transformers

(SPT)

Powertech Transformers designs and manufacturessmall power transformers (SPT) ranging from 20 MVAto 63 MVA and up to 172 kV. The SPT range coversstandard or complex applications from the typicalsubstations to furnaces, tractions, rectifiers and reactors.Powertech Transformers has the skills and resourcesto deal with specific customer needs in terms ofengineering or assembly requirements, specialaccessories as well as special materials or components.The following transformers are included in the SPTrange:

• Double Wound or Auto-Connected

• Outdoor bushings or cable box applications

• 3 phase with/without OLTC

• 2 windings with/without OLTC and with/without stabilising winding.

• ONAN/ONAF/OFAF/ODAF cooling

• Standard/High impedance

• Low sound pressure level

Standard and Complex Medium Power

Transformers (MPT)

Powertech Transformers designs and manufacturesmedium power transformers (MPT) ranging up to200 MVA 275 kV. Other power transformer sizes inthe MPT range is rated above 200 MVA up to 72 kV.The MPT range covers mostly customer applicationssuch as GSU and system power transformers.Powertech Transformers has the skills and resourcesto deal with customer needs, however complex thesemay be in terms of engineering or assemblyrequirements; special accessories and special materialsor components. The following transformers are includedin the MPT range:

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• 3 phase with/without OLTC/OLTS/Link Board

• 2 windings with/without OLTC/OLTS/Link board andwith/without (not loaded) stabilising winding


• Standard/High impedances


Standard and Complex Large Power Transformers

(LPT)

Powertech Transformers designs and manufactureslarge power transformers (LPT) with a three phasepower rating higher than 200 MVA or with voltageratings higher than 275 kV. Powertech Transformerssupplies three phase units up to 800 MVA and singlephase units up to 500 MVA. LPT’s are mostly commonlyused in customer applications such as generator step-up (GSU), system power transformers and largetransmission transformers. The following transformersare included in the LPT range:

• 3 phase with/without OLTC/OLTS/Link Board

• 2 windings with/without OLTC/OLTS/Link board andwith/without (not loaded) stabilising winding


• Standard/High impedances


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Transformers Range Definition

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LPT> 275 kV

SPT 1-2< 40 MVA

72.5 < kV < 171Max BIL 650 kV

LPT> 200 MVA &

>72.5 kV

MVA200MVA63MVA40MVA

72.5kV

172kV

275kV

SystemVoltage kV

For SP 1-5maxBIL 650 kV)

MPT<200 MVA

172 < kV < 275 kV (or BIL >650 kV)

SPT 3-540 < MVA < 63>72.5 - 171 kV

Max BIL 650 kV

LDT< 40 MVA< 72.5 kV

LDT40 < MVA < 63

< 72.5 kV

MPT> 63 MVA & < 72.5 kV

MPT63 < MVA < 20072.5 < kV < 172

System Highest Nominal System FaultVoltage (kV Voltage (kV Level (kA)

7.2 6.6 25 75 75 - 22 13.2

12 11 25 95 95 - 28 22

17.5 16 20 110 110 - 38 32

24 22 20 150 150 - 50 44

36 36 20 200 200 - 70 66

48 44 20 250 200 - 70 95

72.5 66 20 350 250 - 95 140

100 88 25 380 250 - 95 150

145 132 40 550 250/110 - 95/38 230

245 220 50 850 110 - 38 350

300 275 50 1050 110 850 38 350/260

Lightning Impluse (BIL) -kV peak

Switching Impluse (SIL) -kV peak

Power FrequencyWithstand (PF) - kV rms

Line Neutral Phase to Neutral SeparateSource

Induced

Standard Internal Insulation Levels

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Technical Data Sheet (SPT)

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132 88 22 5 9 YNa0d1 min 9.6 6.8 6.1 6.8 3.0 4.0 41 30max 10.8 7.1 6.3 8.0 3.3 4.2 43 31

132 66 22 5 10 YNa0d1 min 9.2 6.7 5.9 6.4 2.9 3.8 40 27max 10.2 7.0 6.1 7.4 3.2 4.0 42 28

132 44 22 5 11 YNa0d1 min 8.8 6.6 5.8 6.0 2.8 3.7 39 26max 9.6 6.9 6.0 6.8 3.1 3.9 40 27

132 33 11 YNd1 min 8.5 6.5 5.6 5.7 2.7 3.5 37 26max 9.2 6.8 5.8 6.4 3.0 3.7 39 28

132 22 11 YNd1 min 8.3 6.5 5.5 5.5 2.7 3.5 36 26max 9.0 6.8 5.8 6.2 3.0 3.7 37 26

132 11 11 YNd1 min 8.2 6.5 5.4 5.4 2.7 3.4 35 2522 max 8.7 6.8 5.7 5.9 3.0 3.6 36 27

132 6.6 10 YNd1 min 8.1 6.5 5.5 5.3 2.7 3.4 35 2522 max 8.6 6.8 5.7 5.8 3.0 3.6 36 27

88 44 22 5 9 YNa0d1 min 8.6 6.7 5.7 6.2 2.9 4.0 38 28max 9.4 7.0 5.9 7.0 3.2 4.2 40 30

88 44 10 YNd1 min 8.6 6.7 5.7 6.2 2.9 4.0 38 28max 9.4 7.0 5.9 7.0 3.2 4.2 40 30

88 33 11 YNd1 min 7.9 6.5 5.5 5.5 2.7 3.8 34 26max 8.6 6.8 5.7 6.2 3.0 4.0 36 27

88 22 11 YNd1 min 7.8 6.5 5.3 5.4 2.7 3.6 34 25max 8.5 6.8 5.5 6.1 3.0 3.8 36 27

88 11 11 YHd1 min 7.7 6.5 5.1 5.3 2.7 3.4 33 2522 max 8.3 6.8 5.3 5.9 3.0 3.6 36 26

88 6.6 11 YNd1 min 7.6 6.5 5.1 5.2 2.7 3.4 33 2522 max 8.2 6.8 5.3 5.8 3.0 3.6 35 26

132 88 22 10 9 YNad1 min 10.6 6.8 6.1 7.8 3.0 4.0 50 39max 11.2 7.1 6.4 8.4 3.3 4.3 53 42

132 66 22 10 10 YNa0d1 min 10.3 6.7 6.0 7.5 2.9 3.9 49 39max 11.0 7.0 6.3 8.2 3.2 4.2 52 41

132 44 22 10 11 YNa0d1 min 10.0 6.7 5.9 7.2 2.9 3.8 48 37max 10.7 7.0 6.2 7.9 3.2 4.1 51 39

132 33 11 YNd1 min 9.7 6.6 5.7 6.9 2.8 3.6 47 35max 10.5 6.9 6.0 7.7 3.1 3.9 49 37

132 22 11 YNd1 min 9.3 6.5 5.7 6.5 2.7 3.6 47 35max 10.2 6.8 6.0 7.4 3.0 3.9 49 37

132 11 11 YNd1 min 9.1 6.5 5.5 6.3 2.7 3.5 46 3522 max 10.1 6.8 6.0 7.3 3.0 3.9 49 36

88 44 22 10 9 YNa0d1 min 10.2 6.8 5.7 7.8 3.0 4.0 52 38max 10.6 7.1 6.0 8.2 3.3 4.3 55 40

88 44 10 YNd1 min 10.2 6.8 5.7 7.8 3.0 4.0 52 38max 10.6 7.1 6.0 8.2 3.3 4.3 55 40

88 33 11 YNd1 min 8.9 6.6 5.4 6.5 2.8 3.7 46 36max 9.7 6.9 5.6 7.3 3.1 3.9 49 38

88 22 11 YNd1 min 8.4 6.5 5.3 6.0 2.7 3.6 46 35max 9.2 6.8 5.5 6.8 3.0 3.8 48 37

88 11 11 YNd1 min 8.1 6.5 5.1 5.7 2.7 3.4 45 3522 max 9.1 6.8 5.3 6.7 3.0 3.6 48 37

88 6.6 11 YNd1 min 8.0 6.5 5.1 5.6 2.7 3.4 45 3422 max 8.9 6.8 5.3 6.5 3.0 3.6 47 36

Rating of ImpedMVA tertiary @Nom Vector

Prim Sec Ter (MVA) Tap(%) Group A B C D E F With Oil Without Oil

Nominal Voltage(kV rms)

Transformer Mass(Ton)

Overall dimensions(m)

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Notes:• Dimensions and masses in the above table are from typical designs completed in recent years and may vary from these values. Specific

values might change based on specific customer requirements.• Contact Powertech Transformers to verify dimensions for specific applications.• Designs and sizes are not limited to the transformer sizes listed in the table above.

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Technical Data Sheet (MPT)

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220 66 22 10 Various YNa0d1 min 11.5 7.0 7.1 8.0 3.2 4.2 65 48max 13.9 7.4 7.6 10.4 3.6 4.7 70 50

275 88 22 10 12.5 YNa0d1 min 12.3 7.0 7.8 8.3 3.2 4.2 88 63max 13.5 7.4 8.3 9.5 3.6 4.7 93 66



132 66 22 10 9 to YNa0d1 min 10.3 6.7 6.2 7.5 2.9 4.1 68 4611.7 max 11.1 7.0 6.3 8.3 3.2 4.2 71 48

132 44 22 10 11.3 YNa0d1 min 10.0 6.6 6.1 7.2 2.8 4.0 61 43max 10.7 7.0 6.3 7.9 3.2 4.2 63 45

132 33 11 YNd1 min 9.9 6.6 6.1 7.1 2.8 4.0 59 41max 10.4 6.9 6.3 7.6 3.1 4.2 61 44


88 33 11 YNd1 min 9.4 6.5 5.6 7.0 2.7 3.9 53 38max 9.8 6.8 5.8 7.4 3.0 4.1 56 40

275 132 22 5 11.3 YNa0d1 min 12.3 7.7 8.4 8.3 3.9 4.8 108 77max 12.7 8.2 8.5 8.7 4.4 4.9 114 81


275 88 22 20 12.5 YNa0d1 min 12.3 7.6 8.3 8.3 3.8 4.7 119 76v 13.1 7.9 8.5 9.1 4.1 4.9 125 81

220 66 22 20 Various YNaod1 min 11.7 7.5 7.3 8.2 3.7 4.4 105 74max 12.4 7.8 7.4 8.9 4.0 4.5 111 78

132 88 22 20 Various YNaod1 min 10.8 7.5 6.3 8.0 3.7 4.2 103 71max 11.3 7.7 6.4 8.5 3.9 4.3 109 75

132 66 22 20 9 to YNa0d1 min 10.7 7.4 6.1 7.9 3.6 4.0 95 67max 11.0 7.7 6.3 8.2 3.9 4.2 100 70






40

80

125

160



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Technical Data Sheet (LPT)

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125 400 132 22 20 14 YNa0d1 min 13.2 7.3 8.8 8.4 3.5 4.5 141 101

max 13.7 7.8 8.9 8.9 4.0 4.6 151 103400 88 22 20 Various YNa0d1 min 13.3 7.5 9.1 8.5 3.7 4.8 181 130

max 13.8 8.1 9.3 9.0 4.3 5.0 195 140400 132 22 40 14 YNa0d1 min 13.6 7.9 9.5 8.8 4.1 5.2 288 140

max 14.8 8.5 9.7 10.0 4.7 5.4 310 149400 22 Various YNd1 min 13.4 7.7 9.3 8.6 3.9 5.0 279 199

max 14.3 8.3 9.6 9.5 4.5 5.3 300 2.7400 15 Various YNd1 min 13.0 7.5 9.1 8.2 3.7 4.8 233 166

max 14.2 8.2 9.5 9.4 4.4 5.2 250 180275 132 22 40 11.3 YNa0d1 min 12.1 7.4 8.2 8.1 3.6 4.6 214 148


max 12.4 8.1 7.8 8.9 4.3 4.9 170 112400 88 22 40 Various YNd1 min 13.8 7.7 9.3 9.0 3.9 5.0 300 213

max 15.9 8.3 9.4 11.1 4.5 5.1 323 224275 132 22 40 12.5 YNa0d1 min 12.5 7.4 8.4 8.5 3.6 4.8 293 209

max 13.3 8.0 8.6 9.3 4.2 5.0 315 219132 88 22 40 Various YNd1 min 10.8 7.3 6.8 8.0 3.5 4.7 288 206

max 11.5 7.9 7.1 8.7 4.1 5.0 310 216400 132 22 40 14 YNa0d1 min 13.7 7.7 9.4 8.9 3.9 5.1 293 223



max 14.3 8.0 9.5 9.5 4.2 5.2 290 214275 132 22 40 11.3 YNa0d1 min 12.5 7.5 8.5 8.5 3.7 4.9 262 200

max 13.3 7.8 8.7 9.3 4.0 5.1 282 209275 88 22 40 12.5 YNa0d1 min 12.5 7.5 8.5 8.5 3.7 4.9 256 195


max 12.7 7.8 8.0 9.2 4.0 5.1 273 203400 220 22 20 14 YNa0d1 min

max

765 400 33 40 Various YNa0d1 min

max

400 275 22 40 12.5 YNa0d1 min

max

400 22 Various YNd1 min

max

400 11 Various YNd1 minmax






800

630

500

315

250

160

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Transformers Range Definition

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Head Office

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

Johannesburg

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

Cape Town

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

Email: [email protected]: www.pttransformers.co.za

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Note: For specific dimensions refer to tables on previous pages

Powertech Transformers

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