Power Transformers Small, Medium & Large

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1 Power Transformers Small, Medium & Large O F T H E A L T R G R O U P A N M E M B E R O ALTRON

2 10 State of the Art Transformer Manufacturing Facility Experience and Design Capability Powertech Transformers have many years of experience in the design, manufacturing, installation and commissioning of small, medium and large power transformers for various applications. Our design experience range from Small Power Transformers (SPT < 60MVA, < 132kV) up to Large Power Transformers (LPT 800MVA, 400kV) including Generation Step-up Units (GSU s). In addition all aspects of auxiliary control circuit application and layout designs are also provided. The transformers manufactured by Powertech Transformers range from standard designs in accordance with IEC requirements to complex designs specific for a customer s individual requirements in the mining, industrial, municipal and power utility industries across the African continent and overseas. The software available to our designers is a state of the art integrated design system. This includes winding design and optimisation; graphical electromagnetic field line plots; temperature analysis; short circuit stress calculations to full 3D CAD modelling of the transformer and its components. This allows our designers to customise each power transformer to specific customer requirements. Customer drawings are prepared for tender designs and finalised on order placement. All electrical and mechanical designs undergo an internal design review process. External design reviews by customers are also allowed for in the design process. If a detailed customer specification is not available, Powertech Transformers can offer a cost effective design based on the requirements of IEC product standards. Powertech Transformers can also provide template technical 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 class manufacturing facility and boasts a fully certified ISO 9001 quality management system, ISO environmental management system as well as the OHSAS health and safety management system. Powertech Transformers in Pretoria also has a fully SANAS accredited metrology laboratory on the premises. At every stage during manufacturing, materials and processes are inspected by suitably qualified and experienced inspectors to ensure all required standard and manufacturing practices are adhered to. Six Sigma (6 ) systems are built into every manufacturing process in the factory to enhance the quality and its documentation of our products.

3 2 Standard Features of our Power Transformers High Quality Materials Sourced from Best Suppliers Powertech Transformers prides itself in our ability to manufacture most of the transformer structural components in-house. Raw materials and components not manufactured in-house are sourced from world class suppliers. Procurement of material and components is done from a list of pre-qualified suppliers locally and internationally who are certified to conform with the highest standards in terms of Quality (ISO9001), Health and Safety (OHSAS 18000) as well as the Environment (ISO 14000) respectively. Before a supplier is approved, their capability is assessed, taking into consideration their technical ability; quality control system; safety, health & environmental controls; financial viability as well as other commercial factors. Supply level agreements are put in place with key suppliers to ensure availability of stock and continuity of supply. A number of enterprise development initiatives are considered for development of small independent business units. Powertech Transformers applies strict control of incoming raw material from pre-qualified suppliers. All incoming goods are quality controlled and checked before they are released into the sub assembly manufacturing lines. Where certification is required, the raw material is sent to our on-site SANAS accredited laboratory for material analysis, verification and certification. Any non-conforming product is rejected and returned to the supplier for rectification or replacement. Transport restrictions on weight and dimensions determine the most appropriate core type for the transformer that is economical on losses; flux density; overall core weight and sound level. Winding Design and Manufacturing The transformer windings must have the ability to withstand high mechanical and electrical stresses resulting from short circuit conditions, lightning and switching surges as well as normal overloads during peak hours in daily operation throughout the lifetime of the transformer. Our windings are made of high strength copper and guarantee high mechanical, electrical and thermal stability under abnormal conditions. This ensures the safe operation of the transformer over its lifetime. Winding technologies are layer, helical, continuous disk and interleaved disk depending on the operating Core Design and Manufacturing Core design principle is based on achieving the smallest active part possible whilst achieving low noise level, low no-load losses and ensuring high short circuit withstand capability of the overall core structure. The basic core design is either a three-limb or a five-limb type core. The core is composed of a circular cross-section without any bolts through the core. The joints are mitred and step-lap stacked. Selection of core steel material for a particular core ranges from conventional cold rolled grain orientated steel (CRGO); to highly permeability steel; to laser scribed grain orientated steel based on customer specifications for no-load losses and noise levels.

4 Standard Features of our Power Transformers conditions as determined by the rated apparent power; rated voltage; network fault level as well as the climatic conditions of the site of operation and specified temperature rise limits. Disk windings are suitable for higher voltages while layer and helical windings are suitable for lower voltages. The conductor used on windings is oxygen free copper. The shape of the conductors is rectangular with small edge-radii. The conductor is often divided into two or more parallel conductor elements to reduce the eddy current losses within the winding. Insulation Material Material for the insulation structure and barrier boards is manufactured from high quality compressed transformer board, compacted laminated wood and/or fibre sheets depending on the application within the transformer with regard to the electrical and mechanical requirements. Elevated temperatures (hot-spots) in transformers are detrimental to paper insulation s longevity due to the decomposition of the cellulose bonding inside the paper at these elevated temperatures. The result is that the insulation between strands is reduced leading to premature insulation failure of the transformer. For paper insulated conductor used on windings, Powertech Transformers has standardised on thermally upgraded paper for all windings types. This ensures an additional 10Kelvin hot spot temperature margin resulting in an extended life of the transformer. Powertech Transformers has a fully equipped paper lapping facility for paper insulating of strip copper as well as an insulation manufacturing facility. Each strand is insulated either by thermally upgraded paper covering, or by an enamel coating, or both. Two separately insulated and parallel strands may sometimes have a common paper covering. Conductor types can be strip conductor or CTC (Continuously Transposed Conductor). Manufacturing of windings is carried out by suitably qualified and experienced winders on vertical or horizontal winding machines. Our winding machines are precisely controlled to achieve constant contact pressure and winding tension.

5 4 Standard Features of our Power Transformers Insulation Oil The mineral oil inside the transformer tank acts as an insulation medium as well as a coolant for the windings inside the transformer. The mineral oil used in our transformers complies with international standards. Only virgin oil is used (free of PCB contamination) and no re-generated oil is used to fill the transformers. Tank Design and Manufacturing The transformer tank accommodates the core and windings (active part) as well as insulating oil. It serves as a support structure for accessories and control equipment as well as acting as physical protection for the active part. Due to its vital role the tank design must be robust and very reliable implying the use of high quality material. The transformer tank is usually of the rigid type with removable radiators connected by shut-off valves. The tank shape and size are designed to optimise the quantity of material used taking into consideration the electrical clearance requirements, structural strength and required oil volume. The base is flat with a minimum thickness of 20mm and is determined by the lifting capacity required for the core and winding masses. Mild steel plates are the main building material used in our tank, cover and conservator as well as all the pipes and fittings. However, where there is a serious concern with high currents e.g. around high current carrying bushings and, on areas where there is a threat of rust, stainless steel is used instead. Double welding is used where oil tightness is required. Rubber or cork rubber compound is used for the gaskets on flanged connected pipe joints/transport and inspection cover openings and all other valves and fittings. Painting and Surface Treatment Powertech Transformers has a range of proven surface treatments depending on the transformer site climatic conditions and application environment. All paint and coatings are done in accordance with a documented in-house painting system complying with strict safety, health, environmental and quality requirements. All new transformers, irrespective of whether they are operating in non-corrosive or corrosive environments, are coated in accordance with Powertech Transformers corrosive protection specification. Tank external surfaces are painted with a two-component epoxy primer followed by a two component acrylic or polyurethane finishing coat. In addition to the standard corrosion protection painting system, a zinc-metal spray coating can be applied on customer request. Other customer specific painting system requirements are also provided for. All external surfaces of the transformer and accessories are colour coded in accordance with the Natural Colour System (NCS codes) or RAL international colour standards to a customer s unique requirements. Separate radiators are generally hot-dip galvanised.

6 Standard Features of our Power Transformers Main Terminals Customers have a choice of bushings from standard solid porcelain oil impregnated (OIP) type bushings to resin impregnated (RIP) bushings for various applications such as Oil to Air, Oil to Oil, Oil to SF6, Air to Air and Air to SF6. Our bushings are always sourced from world class suppliers of bushings, who comply with international standards and are generally positioned on the cover. For voltages above 52 kv, condenser type bushings which facilitate the electric stress control via the insertion of floating aluminium equaliser screens which are located in the condenser core are used. Enclosures can be provided on the primary and/or on the secondary side and may be constructed for cable or bus duct connection. Transformers may also be provided with plug-in or cable box bushings. Accessories Depending on the type and application of the transformer the accessories will usually include a combination of the following items either as standard or 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 conservator to prevent oil coming into direct contact with air Tap changers (oil type as well as vacuum) 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 to customer specifications. Drying and Vacuum Treatment The moisture content in oil and solid insulation can have adverse effects on the life span of the transformer since it affects the dielectric breakdown strength of solid and liquid insulation. This affects the rate at which the cellulose ages and the propensity for bubble evolution during overloads. In order to counteract these negative effects of moisture adequate drying and vacuum treatment is performed using proven technology such as Vapour Phase Drying and LFH (Low Frequency Heating). Before filling, the oil is always degassed and purified. Testing Every transformer at Powertech Transformers is individually tested according to major international standards as well as, in accordance with any special tests required by the customer, and must pass all these tests before leaving the factory. The test certificate forms part of the transformer operating manual. 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 Temperature Indicators (Analogue or Digital). Fibre optic probes for direct hot spot temperature measurements on active part.

7 6 Standard Features of Powertech s Power Transformers SFRA (Swept Frequency Response Analysis) fingerprinting is also done before the transformer leaves the factory and redone on site. Impact recorders are installed on the core as well as on the tank of the transformer to verify adverse impacts or accelerations in all three dimensions. Results of the SFRA test and impact recorder data are made available to our customers. Standard and Complex Small Power Transformers (SPT) Powertech Transformers designs and manufactures small power transformers (SPT) ranging from 20 MVA to 63 MVA and up to 172 kv. The SPT range covers standard or complex applications from the typical substations to furnaces, tractions, rectifiers and reactors. Powertech Transformers has the skills and resources to deal with specific customer needs in terms of engineering or assembly requirements, special accessories as well as special materials or components. The following transformers are included in the SPT range: 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 3 phase with/without OLTC/OLTS/Link Board 2 windings with/without OLTC/OLTS/Link board and with/without (not loaded) stabilising winding ONAN/ONAF/OFAF/ODAF cooling Standard/High impedances Low sound pressure level Standard and Complex Large Power Transformers (LPT) Powertech Transformers designs and manufactures large power transformers (LPT) with a three phase power rating higher than 200 MVA or with voltage ratings higher than 275 kv. Powertech Transformers supplies three phase units up to 800 MVA and single phase units up to 500 MVA. LPT s are mostly commonly used in customer applications such as generator stepup (GSU), system power transformers and large transmission transformers. The following transformers are included in the LPT range: 3 phase with/without OLTC/OLTS/Link Board 2 windings with/without OLTC/OLTS/Link board and with/without (not loaded) stabilising winding ONAN/ONAF/OFAF/ODAF cooling Standard/High impedances Low sound pressure level Standard/High impedance Low sound pressure level Standard and Complex Medium Power Transformers (MPT) Powertech Transformers designs and manufactures medium power transformers (MPT) ranging up to 200 MVA 275 kv. Other power transformer sizes in the MPT range is rated above 200 MVA up to 72 kv. The MPT range covers mostly customer applications such as GSU and system power transformers. Powertech Transformers has the skills and resources to deal with customer needs, however complex these may be in terms of engineering or assembly requirements; special accessories and special materials or components. The following transformers are included in the MPT range:

8 Transformers Range Definition System Voltage kv LPT > 275 kv 275kV MPT <200 MVA 172 < kv < 275 kv (or BIL >650 kv) LPT > 200 MVA & >72.5 kv 172kV For SP 1-5max BIL 650 kv) SPT 1-2 < 40 MVA 72.5 < kv < 171 Max BIL 650 kv SPT < MVA < 63 > kv Max BIL 650 kv MPT 63 < MVA < < kv < kV LDT < 40 MVA < 72.5 kv LDT 40 < MVA < 63 < 72.5 kv MPT > 63 MVA & < 72.5 kv 40MVA 63MVA 200MVA MVA Standard Internal Insulation Levels System Highest Nominal System Fault Voltage (kv Voltage (kv Level (ka) Lightning Impluse (BIL) - kv peak Switching Impluse (SIL) - kv peak Power Frequency Withstand (PF) - kv rms Line Neutral Phase to Neutral Separate Source Induced /110-95/ /260

9 8 Technical Data Sheet (SPT) Nominal Voltage Overall dimensions Transformer Mass (kv rms) Rating of Imped (m) (Ton) MVA Vector Prim Sec Ter (MVA) Tap(%) Group A B C D E F With Oil Without Oil YNa0d1 min max YNa0d1 min max YNa0d1 min max YNd1 min max YNd1 min max YNd1 min max YNd1 min max YNa0d1 min max YNd1 min max YNd1 min max YNd1 min max YHd1 min max YNd1 min max YNad1 min max YNa0d1 min max YNa0d1 min max YNd1 min max YNd1 min max YNd1 min max YNa0d1 min max YNd1 min max YNd1 min max YNd1 min max YNd1 min max YNd1 min max 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.

10 Technical Data Sheet (MPT) Nominal Voltage Overall dimensions Transformer Mass (kv rms) Rating of Imped (m) (Ton) MVA Vector Prim Sec Ter (MVA) Tap(%) Group A B C D E F With Oil Without Oil Various YNa0d1 min max YNa0d1 min max Various YNa0d1 min max Various YNa0d1 min max to YNa0d1 min max YNa0d1 min max YNd1 min max Various YNa0d1 min max YNd1 min max YNa0d1 min max Various YNa0d1 min max YNa0d1 min v Various YNaod1 min max Various YNaod1 min max to YNa0d1 min max 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.

11 Technical Data Sheet (LPT) Nominal Voltage Overall dimensions Transformer Mass (kv rms) Rating of Imped (m) (Ton) MVA Vector Prim Sec Ter (MVA) Tap(%) Group A B C D E F With Oil Without Oil YNa0d1 min max Various YNa0d1 min max YNa0d1 min max Various YNd1 min max Various YNd1 min max YNa0d1 min max Various YNa0d1 min max Various YNd1 min max YNa0d1 min max Various YNd1 min max YNa0d1 min max Various YNd1 min max Various YNd1 min max YNa0d1 min max YNa0d1 min max Various YNa0d1 min max YNa0d1 min max Various YNa0d1 min max YNa0d1 min max Various YNd1 min max Various YNd1 min max 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.

12 Transformers Range Definition F C D A E B Note: For specific dimensions refer to tables on previous pages Head Office 1 Buitenkant Street, Pretoria West, PO Box 691, Pretoria, 0001, South Africa Tel +27 (0) Fax +27 (0) Johannesburg 56 Third Street, Booysens Reserve, Johannesburg, PO Box 38354, Booysens, 2016 Tel Fax Cape Town Elliot Avennue, Epping PO Box 44, Eppindust, Cape Town, 7475, South Africa Tel +27 (0) Fax [email protected] Web: