Transformer Training Reinhausen Middle East PDF

Maschinenfabrik Reinhausen GmbH Transformer Training Reinhausen Middle East © MR 2023 Transformer Training Trainer Hagop Beddourian 30-Oct-24 | 2 Working safety on transformers Equipment Safety equipment list: + Protective helmet with a chin strap + Protective g...

Maschinenfabrik Reinhausen GmbH Transformer Training Reinhausen Middle East © MR 2023 Transformer Training Trainer Hagop Beddourian 30-Oct-24 | 2 Working safety on transformers Equipment Safety equipment list: + Protective helmet with a chin strap + Protective goggles + Work clothes + Safety shoes + Safety belt + Ear protection + Protective gloves for electrical work 30-Oct-24 | 3 Evacuation Map 30-Oct-24 | 4 Working Safety on Transformers Protective Measures Protective measures that must be performed by the user before starting work + Shut down the transformer + Provide a safeguard to grounding switch to prevent unintentional restart + Verify de-energized state + Ground visibly, ensure proper cable cross-section and by-pass, ground star-point terminal + Mark hazard area clearly + Switch off and provide safeguard to deluge sprinkler or CO2 units + Switch off oil and water pumps to prevent electrostatic charging hazards + Use ladders of appropriate size and tie them to a suitable point + Explain and show escape routes 30-Oct-24 | 5 RME Transformer Training Agenda Day 1 Day 2 Day 3 Introduction/Conclusion 09:00-09:30 Introduction Maintenance Strategies Theoretical Training Electrical measurements Practical Training 09:30-10:30 Transformer Basics Routine Services 10:30-10:45 Break Break Break 10:45-11:30 Oil Sampling & Oil analysis Transformer Mechanical Arrangement Testing of electrical equipment Taking oil samples 11:30-12:30 from the transformer 12:30-13:00 Lunch Lunch Lunch Checking the components on the 13:00-14:00 Oil Processing & Oil Reconditioning Thermography​ transformer Testing thermography equipment on 14:00-15:00 Transformer Manufacturing Process Oil Reclaiming & Oil Replacement the transformer​ 15:00-15:15 Break Break Break Testing thermography equipment on 15:15-16:15 Visual Inspection Testing oil reconditioning equipment the transformer​ Taking visual inspection on the on the transformer 16:15-16:45 Conclusion transformer 10/30/2024 | 6 MR at a glance Family business since World market leader 1868 50% in the sixth generation of the world's electricity family owned flows through our products 1/1 1/1 Economically healthy 1/2 2/2 1/1 5/10 Reliability 1 billion 50+ years 1/1 1/1 1/1 2/4 1/2 1/1 2/6 1/1 2/2 1/1 2/1 euros revenue in 2023 1/1 of OLTC lifetime proves the 1/1 Highest rating (AAA) 4/5 unmatched MR product quality 1/1 1/1 1/1 1/1 Employees Present all over the world 4,000 8,000 1/2 1/1 61 nationalities customers at 60 locations in 185 countries Factory Office X/X Subsidiaries/Locations 30-Oct-24 | 7 28 Subsidiaries and 11 Joint Ventures Worldwide Sep Jan 1868 Maschinenfabrik Reinhausen GmbH (MR) 5 12 Jiangsu MR Manufacturing Co., Ltd. (MRM) 1 24 British Transformer Components Ltd. (RGB) 1 2006 2016 Jul Sep Apr 1 MR do Brasil Ind. Mec. Ltda. (MRB) 1 13 Reinhausen Middle East FZE (RME FZE) 0 V Reinhausen (Thailand) Ltd. (RTH) 1 1980 2006 2016 Okt Jan Apr 2 Reinhausen Australia Pty. Ltd. (RA) 1 14 Reinhausen Korea Ltd. (RKR) 2 25 Reinhausen España S.L. (RES) 1 1987 2009 2016 Dez Aug Okt 3 Reinhausen Manufacturing Inc. (RM) 5 15 Reinhausen Power Composites GmbH (RPC) VI Reinhausen Enerji Çözümleri Anonim Şirketi (RTR) 1 1989 2009 1 2016 Nov Sep Jul 4 Reinhausen Italia S.r.l. (RI) 2 16 Reinhausen Luxembourg S.A. (RLU) 1 26 Hans von Mangoldt GmbH (HVMAC) 1 1993 2009 2017 Okt Jan Jul I Easun-MR Tap Changers (P) Ltd. (EMR) 2 17 Reinhausen Canada Inc. (RCA) 2 VII Hans von Mangoldt Taiwan Co. Ltd. (HVMTW) 1 1995 2010 2017 Jul Mrz Jul 5 Reinhausen Asia-Pacific Sdn. Bhd. (RAP) 1 18 PT. Reinhausen Indonesia (RID) 1 VIII Meher Mangoldt Inductors Pvt, Ltd. (MMIPL) 1 1996 2011 2017 Jan Okt Okt 6 Messko GmbH (MS) 1 III Reinhausen 2e d.o.o. (RSI) 1 IX Aditya Birla Power Composites Ltd. (ABPC) 1 1999 2011 2019 Jan 1 Apr Jan 7 MR Japan Corp. (MRJ) 19 Reinhausen Nordic AB (RSE) 1 X Reinh. Middle East Energy Solutions LLC (RME LLC) 1 2002 2012 2020 Feb Okt Aug 8 HIGHVOLT Prüftechnik Dresden GmbH (HV) 2 20 Reinhausen Mexico S. de R.L. de C.V. (RMX) 1 27 Advanced Testing Systems Inc. (HVATS) 1 2002 2014 2022 Jun Jun Sep 9 OOO MR (MRR) 1 21 Amantys Power Electronics Ltd. (APE) 1 28 TOO Reinhausen Kazakhstan (RKA) 1 2003 2015 2023 Nov Jan Sep 10 Reinhausen South Africa (Pty) Ltd. (RZA) 2 22 Cedaspe S.r.L. (CEDASPE) 29 C.B. System-Oil S.L. (CBS) 1 2005 2016 2 2023 Dez Jan 2005 II Iran Transfo After Sales Service Co. (ITASS) 1 2016 IV Reinhausen Singapore Pte. Ltd. (RSG) 1 Mai Jan 2006 11 MR China Ltd. (MRT) 1 2016 23 Sukrut Electric Company Pvt Ltd. (SECPL) 1 Factory Office Note: Exclusively operating companies 30-Oct-24 | 8 Uniquely Inventive – since 1929 1929 1974 1990 2000 2012 2016 2018 2021 2021 1978 1990 2020 High-speed Semi- Reactor-type Vacuum Modular Distribution Transformer DC Strongest Reactor with Largest Most power- resistor-type conductor tap-changer technology active filter tap-changer operating transformer vacuum tap- PolyGap outdoor test ful resonant tap-changer tap-changer system changer technology system test system 30-Oct-24 | 9 History of the Transformer 1831 1871 1885 1891 1909 Electromagnetic induction, the Russian engineer Pavel Yablochkov William Stanley's First Transformer Early three phase transformer Oil Insulation Building Oil principle of the operation of the invented a lighting system based built in 1885. Single phase AC power. (circular core type) Cooled Transformers transformer, was discovered on a set of induction coils where Siemens and Halske company independently by Michael Faraday. the primary windings were 5.7 kVA 1000/100 V connected to a source of AC 30-Oct-24 | 10 THE POWER BEHIND POWER. 30-Oct-24 | 11 Overview: Transformer Main Components Clamping HV Bushings Frame Conservator LV Bushings Oil level indicator Bevel gear unit Buchholz relay Protective relay Pipes Drive shafts Dehydrating breathers On-load tap-changer Nameplate Radiators Tap Leads Tank Tapped Winding Motor-drive unit Measurements Three-limb core LV Winding HV Winding 30-Oct-24 | 12 Transformer Basics Agenda: + Main components + Use and operation + Construction of a transformer + Different construction types + Autotransformer + Loaded and unloaded transformer + Short-circuit voltage and short-circuit current + Real transformer and efficiency + Transformer calculations 30-Oct-24 | 13 Transformer Basics Use and Operation Did you know… + that the transformer was one of the reasons, why the alternating current (AC) won the "current war"? + With a transformer, the voltage can be transformed and thus the energy can be transported? 30-Oct-24 | 14 Transformer Basics Use and Operation Operation: + A transformer only works with alternating current (AC), not with direct current (DC)! + The AC supply is connected to the primary side, the alternating current creates an alternating magnetic field, the voltage induced by the magnetic field in the primary winding keeps balance with the supply voltage (=induction law) + Through the iron core, the magnetic flux is conducted to the secondary side + Now the secondary winding is also permeated with a changing magnetic field --> this induces an AC voltage in the secondary coil + The induced voltage is the same in each turn / the induced voltage of both coils is proportional to the number of their turns = transformer ratio 30-Oct-24 | 15 Transformer Basics Construction of a Transformer Construction of a transformer + Consists of two or more coils on a common iron core + The core is built from a stack of individual sheets, with electrical insulation layers in between -> thus reducing eddy currents + Primary winding = input winding -> voltage connection + Secondary winding = output winding -> here is the electrical load connected 30-Oct-24 | 16 Transformer Basics Different Construction Types Shell type + Both windings are on the middle leg, either one above the other, or side by side. Advantages: + Higher efficiency + More power Disadvantages: + Maintenance work is very hard + Forced cooling indispensable 30-Oct-24 | 17 Transformer Basics Different Construction Types Core type + The middle leg is missing, the core forms the shape of a rectangle inside view. Usually, the windings are located separately on the two outer legs. Advantages: + Cheaper + Easier maintenance Disadvantages: + Higher flux leakage 30-Oct-24 | 18 Transformer Basics Autotransformer Autotransformer + Consists of only one coil which has one or more taps to draw the output voltage. Primary coil and secondary coil are combined -> No galvanic separation Advantages: + Smaller construction with the same power + More efficient compared to two windings + transformer Disadvantages: + If a fault like a short circuit occurs on the primary side, this fault is also on the secondary side, because they are combined Area of application: + Wherever deviating voltages must be provided and galvanic insulation is not required. 30-Oct-24 | 19 Transformer Basics Loaded and unloaded transformer Unloaded transformer Loaded transformer + If no load is connected to the secondary winding, + If a consumer is connected to the secondary there is no load -> the transformer is unloaded winding, it takes electrical energy from the + In no-load operation, the iron losses are much secondary coil bigger due to the small input current than the + A current arises on the secondary side and the copper losses due to the no-load current in the primary current gets bigger primary coil + The currents are directed in opposite directions in + Does not normally exist in practice the windings + If the primary current flows right-handed through the coil, the secondary current flows left-handed and vice versa + Transformers can be heavily overloaded for a short time 30-Oct-24 | 20 Transformer Basics Short-Circuit Voltage and Short-Circuit Current Short-circuit voltage Short-circuit current + The short-circuit voltage depends on the + This is the name given to the current that flows in construction of the core and the position of the the event of a short circuit on the secondary side coils in relation to each other and at nominal voltage supply on the primary + High stray fluxes lead to high short-circuit side. voltages + It is much higher than the rated current and can + Stray fluxes are part of a magnetic flux which are destroy the transformer within a short time coupled with one of the windings only, so lost + The short-circuit current is higher the lower the from the energy transfer. Stray fluxes can be short-circuit voltage is taken into account by the impedance + Short-circuit proof --> Name for transformers, representing their magnetic path. More stray flux, which are designed in such a way that they are larger impedance, higher voltage drop. not destroyed in the event of a short circuit 30-Oct-24 | 21 Transformer Basics Real Transformer and Efficiency + In reality, there is no loss-free transformer + Losses due to resistances in the windings and parasitic capacitances + Losses in the metal structure caused by scattering of the magnetic flux + Eddy currents and magnetic reversal losses in the iron core + This results in energy losses + The efficiency indicates the ratio of the power which leaves the transformer on the secondary side and the power which flows in on Typical efficiency of different transformers: the primary side. That means how much energy gets "lost". + Transformers with high rated power: 99% + The higher the efficiency, the fewer the losses and the more efficient + Small transformers: 80% the transformer works. + Miniature transformers: 50% + The efficiency can, because of the iron and copper losses, never be 1. It is expressed in %. 30-Oct-24 | 22 Transformer Basics Transformer Calculations The voltages, currents and the windings can be calculated with the following formula: V = Voltage in Volt (V) I = Current in Ampere (A) + The ratio of the input and output voltage corresponds to the N = Winding turn number ratio of the winding turn numbers of the input and output sides. 30-Oct-24 | 23 Transformer Mechanical Arrangement Agenda + Transformer Magnetic Core + Windings and Insulation + Tanks and Fittings + Bushings + Tap-Changer + Cooling Equipment + Protection Equipment & Additional Equipment 30-Oct-24 | 25 Transformer Mechanical Arrangement Transformer Magnetic Core + A magnetic core is a piece of magnetic material with a high magnetic permeability used to confine and guide magnetic fields in electrical, electromechanical and magnetic devices such as electromagnets, transformers, electric motors, generators, inductors, loudspeakers, magnetic recording heads, and magnetic assemblies. It is made of ferromagnetic metal such as iron, or ferrimagnetic compounds such as ferrites. + The high permeability, relative to the surrounding air, causes the magnetic field lines to be concentrated in the core material. The magnetic field is often created by a current-carrying coil of wire around the core. + The use of a magnetic core can increase the strength of magnetic field in an electromagnetic coil by several hundred times of what it would be without the core. However, magnetic cores have side effects which must be taken into account. In alternating current (AC) devices, they cause energy losses, called core losses, due to hysteresis and eddy currents in applications such as transformers and inductors. "Soft" magnetic materials with low coercivity and hysteresis, such as silicon steel, or ferrite, are usually used in cores. 30-Oct-24 | 26 Transformer Mechanical Arrangement Winding and Insulation THE ROLE OF TRANSFORMER WINDING INSULATION + Insulation Protection: Winding insulation provides insulation material to insulate the conductors and coils within the winding, preventing electrical currents from short-circuiting or breaking down within the winding. This helps ensure the electrical safety of the transformer, preventing faults and damage to the winding. + Mechanical Support: The insulation material secures and supports the conductors and coils within the winding, preventing them from moving or vibrating during operation. This helps maintain the shape and structural integrity of the winding, reducing the adverse effects of mechanical stress on the transformer. + Heat Conduction: Insulation materials assist in the even distribution and conduction of the heat generated within the winding. This helps prevent localized hotspots and excessively high temperatures, extending the lifespan of insulation materials and improving the efficiency and reliability of the transformer. + Electric Field Distribution: Insulation helps control the distribution of electric fields, reducing uneven electric field intensities. This aids in minimizing electric field concentration, lowering the risk of partial discharge and enhancing the stability of the insulation system. + Noise Reduction: Insulation materials can reduce the vibration and noise within the winding, providing a quieter operating environment. 30-Oct-24 | 27 Transformer Mechanical Arrangement Definitions of Primary, Secondary, Tertiary and Tapping Coils Multiple Winding Transformers + Multiple Winding Transformers can have two or more primary or secondary windings, allowing for different combinations of voltages and currents + Multiple Winding Transformers generally have one single primary winding with two or more secondary windings. But the beauty of transformers is that they allow us to have more than just one winding in either the primary or secondary side. Transformers which have more than one winding are known commonly as Multiple Winding Transformers. + The principal of operation of a multiple winding transformer is similar to that of an ordinary transformer. Primary and secondary voltages, currents and turns ratios are all calculated the same, the difference this time is that we need to pay special attention to the voltage polarities of each coil winding, the dot convention marking the positive (or negative) polarity of the winding, when we connect them together. 30-Oct-24 | 28 Transformer Mechanical Arrangement Windings Solid/Paper Insulation Windings solid/paper Insulation + Insulation Barriers: − Insulating paper is used as barrier or separator between different windings or sections within a transformer. These barriers prevent electrical contact and ensure insulation integrity between primary and secondary windings or different voltage levels within the transformer. + Between Conductors: − Insulating paper is placed between individual conductors within a winding to provide electrical insulation and prevent short circuits. It separates the adjacent conductors and helps maintain the required electrical clearances. + Interlayer Insulation: − Insulating paper is used as interlayer insulation between different layers of conductors within a winding. It helps insulate adjacent conductor layers and ensures proper electrical insulation between them. 30-Oct-24 | 29 Transformer Mechanical Arrangement Different Conductors Used for Transformer Windings + Transposed cable + Individual epoxy & enamel covering + Common paper or netting tape covering + Tripple conductor + Individual and common paper covering + Twin conductor + Flat conductor + Individual and common paper covering + Individual paper covering 30-Oct-24 | 30 Transformer Mechanical Arrangement Different Conductors Used for Transformer Windings Paper insulation Conductor Paper insulation Conductor Conductor – enamel insulation Paper insulation 30-Oct-24 | 31 Insulation strip Transformer Mechanical Arrangement Different Conductors Used for Transformer Windings + Winding made with netting tape covered transposer cable: 30-Oct-24 | 32 Transformer Mechanical Arrangement Different Winding Types Layor Winding: Single Layer Winding: Multi-Layer Winding: + Tertiary Winding + LV Main Winding on Power + Regulating Winding Transformers < 100 MVA − Coarse Winding + Low number of turns, − Fine Winding, with parallel loops relatively high current Disadvantage: + Cooling only on the inner and outer surface 30-Oct-24 | 33 Transformer Mechanical Arrangement Different Winding Types Helical Winding: + Single Layer Winding with axial spacers between the turns + MV and LV Main Winding for Power Transformers + Relatively low turns, high currents Advantages: + Improved electrical strength and cooling due to the spacers between the windings + Further improved cooling through oil guidance + Further improved cooling with transposed cable without paper covering 30-Oct-24 | 34 Transformer Mechanical Arrangement Different Winding Types Disc Winding: + More than one turn radially in one disc Double Disc Single Disc + HV Main Winding for Power Transformers + High number of turns, relatively low currents Advantages: + High electrical strength through interleaving and shielding + Improved cooling through oil guidance + Improved cooling through radial cooling ducts 30-Oct-24 | 35 Transformer Mechanical Arrangement Different Winding Types Disc Winding – Interleaving: 30-Oct-24 | 36 Transformer Mechanical Arrangement Different Winding Types Disc Winding – Shielding: 30-Oct-24 | 37 Transformer Mechanical Arrangement Regulating Winding Conventional diagram: Single Loop Layer (SLL) Winding: Voltage across the regulating winding: 30-Oct-24 | 38 Transformer Mechanical Arrangement Regulating Winding Conventional diagram: Regulating bunch – a, c, d, b: Voltage across the regulating winding: 30-Oct-24 | 39 Transformer Mechanical Arrangement BUSHING Overview Bushing Technology Bushing type Dielectric material Pros Cons 1. High risk of failure Paper OIP (oil impregnated) 1. Cheap 2. Possible moisture Main ingress due to paper Conductor Capacitive Paper 1. Medium risk of failure RBP 1. Not produced anymore 2. Possible moisture Layers (resin bonded) ingress due to paper 1. Medium price Paper 1. Possible moisture Dielectric material between RIP (resin impregnated) 2. Current state of the art 3. Long term experience ingress due to paper capacitive layers* 1. No moisture ingress 1. High price RIS Synthetics due to synthetics 2. No long-term experience 2. Highest reliability 1. No moisture ingress Measuring RIF Fiber Glass due to fiber glass 1. High price 2. No long-term experience 2. Highest reliability Tap | Transformer Mechanical Arrangement BUSHING Overview Bushing Technology Still dominant State-of-the-art- type type Oil Bushing Oil-free Bushing OIP RBP RIP RIS RIF Oil Impregnated Resin Bonded Resin Impregnated Paper Resin Impregnated Synthetics Resin Impregnated Fiber Paper Paper Are still produced Yes No Yes Yes Yes Cost Low Low Medium High High Absorption of Water Yes Yes Yes No No Failure risk High Medium Low Low Low Temperature resistance max 105°C max 120°C max 120°C max 120°C to 130°C Lifetime ~ 25 Years ~ 25 Years ~ 30 Years no Info no Info Partial Discharge Risk High High Low Low Low Mechanical Strength Bad Good Very Good Very Good Very Good Earthquake resistance Bad Good Very Good Very Good Very Good | Transformer Mechanical Arrangement Cooling Methods Winding hotspot: + Beware: the highest winding temperature is not always at the top of the winding: + Losses caused by harmonic components that are in phase opposition in a double tier rectifier transformer. | Transformer Mechanical Arrangement BUSHING PROS & CONS of using porcelain bushings: + Risk of oil leakage and transformer fire + Risk of breakages due to vandalism/terrorist attacks + Risk of explosion and fragments shard due to electrical arcs + Need regular maintenance (cleaning & washing) + Fragility, so difficult handling + Not recommended for horizontal mounting + Good compression strength but weak bending strength 30-Oct-24 | 43 Increasing Transformer Reliability by Proactive Bushing Fleet Management Managing a bushing fleet over its lifetime reduces the risk of failures and avoids extended system downtimes + Aging of transformers = higher hazard rate + Failures originating in the transformer insulation are the largest contributors, followed by the windings and winding exit leads + Anticipate aging trend within an installed transformers fleet 30-Oct-24 | 44 HV Bushings life management importance Role of Bushings in Transformer Failures + Bushings are among the most critical components of a power transformer and there is evidence that they are among the major initiators of failures. For instance, on average, the risk of a large power transformer failure is assumed to be up to 1% per year of service. Furthermore, it is estimated that 10% of transformer failures result in serious fire, meaning that this risk is as high as 0.1% in each year of service. + Transformer failure location analysis in certain European + Almost 50% of all serious transformer fires are countries. (left) Whole population, (right) transmission initiated by failure of OIP bushings and these are, transformers with rated service voltage >100 kV. therefore, properly classified as the single leading cause of transformer fires. 30-Oct-24 | 45 Transformer Mechanical Arrangement BUSHING SILICONE COMPOSITE BUSHING (SBC) + The fragile porcelain insulator can be replaced with a composite insulator created through a high-tech combined materials solution + A fiber glass tube ensures: + Superior mechanical strengths to bushings, such as: cantilever load; horizontal assembly + Alternated shed profile made of silicone molded coating grants: + All electrical features in compliance with IEC 137 + The combination of silicone rubber and fiber glass creates a superior pedigree of bushings for Transformers 30-Oct-24 | 46 Transformer Mechanical Arrangement BUSHING TECHNICAL DATA Maximum rated voltage 12 kV, 24 kV, 36 kV, 52 kV Maximum rated current 630 A, 1,250 A, 2,000 A, 3,150 A, 4,500 A Creepage distance from 505 mm/kV up to 1,690 mm/kV Standard reference IEC 60137 * Clamping interface DIN 42538 and EN 50180 Partial discharges Low acc to IEC 60137 (< 10 pC) Special finishing Tin plating / Silver plating/ Other 30-Oct-24 | 47 Transformer Mechanical Arrangement Main Components of an on-load tap-changer (OLTC) SET OLTC Motor-drive Unit Accessories 30-Oct-24 | 48 Transformer Mechanical Arrangement OLTC Components – Overview OLTC head with cover and pipe connections OLTC oil compartment Tap selector 30-Oct-24 | 49 Transformer Mechanical Arrangement OLTC Components – OLTC Oil Compartment Inside view OLTC oil compartment 30-Oct-24 | 50 Transformer Mechanical Arrangement OLTC Components – Overview OLTC head with cover and pipe connections OLTC oil compartment Tap selector 30-Oct-24 | 51 Transformer Mechanical Arrangement OLTC Head with Cover & Pipe Connections Temperature sensor Position indicator PRD flange with pressure relief device Blind flange OLTC head Pipe connections OLTC head cover Air bleed valve Drive shaft Upper gear unit 30-Oct-24 | 52 Transformer Mechanical Arrangement OLTC Components – Overview OLTC head with cover and pipe connections OLTC oil compartment Tap selector 30-Oct-24 | 53 Transformer Mechanical Arrangement OLTC Components – Overview OLTC head with cover and pipe connections Supporting cylinder OLTC oil compartment Interrupter exchange module Tap selector Resistors 30-Oct-24 | 54 Transformer Mechanical Arrangement OLTC Components – Diverter Switch Insert (DSI) 30-Oct-24 | 55 Transformer Mechanical Arrangement OLTC Components – Tap Selector 30-Oct-24 | 56 Transformer Mechanical Arrangement MR Motor-Drive Unit 30-Oct-24 | 57 Transformer Mechanical Arrangement MR Motor-Drive Unit 30-Oct-24 | 58 Transformer Mechanical Arrangement Conventional Technology vs. VACUTAP® + Conventional Technology + VACUTAP® Technology + All types of MR on-load tap-changers where the arc is + All types of MR on-load tap-changers where the arc is extinguished in oil extinguished in a vacuum interrupter + Contact life: 200,000 - 500,000 tap-change operations + Contact life: 600,000 tap-change operations 30-Oct-24 | 59 Transformer Mechanical Arrangement Conventional Technology + Switching arc under oil + Formation of carbon bodies and switching gases + Heating of transition resistors + Mineral oil − Insulating − Cooling − Arc quenching − Lubrication + Aging of OLTC insulating oil 30-Oct-24 | 60 Transformer Mechanical Arrangement OLTC Operating Principle + + Oil Compartment + Diverter Switch Insert + Moving Contact System + Tap Selector + Transition Resistors 30-Oct-24 | 61 Transformer Mechanical Arrangement Tap Changer What is a tap changer? + An electric switch with several switching positions + Used to set the transmission ratio (winding ratio) in a transformer + If the transmission ratio (winding ratio) changes, the voltage ratio and thus the output voltage changes + Tap changers are built for one, two or three phases + With an on-load tap-changer, uninterrupted switching operation under load is possible 30-Oct-24 | 62 Transformer Mechanical Arrangement Tap Changer Assemblies of a High-Speed Resistor-Type Tap-Changer A high-speed resistor-type tap-changer consists of many assemblies. Here are the most important ones listed: + Oil compartment + Diverter switch insert + Tap selector + Change-over selector / Pre-selector A distinction is made between diverter switch insert with selector and selector switch. 30-Oct-24 | 63 Transformer Mechanical Arrangement Tap Changer The different types of a tap changer 30-Oct-24 | 64 Transformer Mechanical Arrangement Tap Changer De-Energized Tap-Changer (DETC) + A DETC has the same function as the OLTC, but it can only be operated when it is de-energized, meaning the transformer must be switched off + DETCs are usually designed with few steps and are often only operated by hand + DETCs are usually used when there are only a few switching operations + They are largely maintenance-free 30-Oct-24 | 65 Transformer Mechanical Arrangement Tap Changer On-Load Tap-Changer (OLTC) + For the uninterrupted switching operation under load, meaning the transformer is on Semiconductor Tap-Changer Reactor-Type Tap-Changer + Hybrid switch with power electronic tap-changer + Has a universal usability with impressive (current) power + Developed for wear-free switching operations parameter + Due to the temperature sensitive semiconductor + For make-before-break switching operation with a reactor technology, the switch was placed outside the (preventive autotransformer) as a transition impedance transformer + The first tap changer with vacuum switching technology 30-Oct-24 | 66 Transformer Mechanical Arrangement Tap Changer On-Load Tap-Changer (OLTC) + For the uninterrupted switching operation under load, meaning the transformer is on High-Speed Resistor-Type Tap-Changer + According to the patent of Dr. B. Jansen, 1929 + For make-before-break switching operation with ohmic transition resistors and high-speed operation time + Majority of tap changers worldwide 30-Oct-24 | 67 Transformer Mechanical Arrangement Tap Changer Diverter Switch Insert with Tap Selector Selector Switch Advantages: Advantages: + Higher switching power + Compact/space-saving + Cheaper 30-Oct-24 | 68 Transformer Mechanical Arrangement Tap Changer Function of an On-Load Tap-Changer + The operation principle of a tap changer installed in a transformer can best be explained with an example: + A car equipped with automatic transmission and cruise control drives along a hilly route. + The cruise control ensures that the speed once set is maintained. Accordingly, the automatic transmission shifts up or down depending on the gradient. + The tap changer in the transformer (car) works similarly. If the values specified by a voltage regulation (cruise control) are exceeded or undershot in times of high or low electricity consumption (hilly route), the switch changes (automatic transmission) in fractions of a second from one transformer winding to the next suitable level and thus ensures that the voltage remains constant. 30-Oct-24 | 69 Transformer Mechanical Arrangement Tap Changer 30-Oct-24 | 70 Transformer Mechanical Arrangement OILTAP® vs. VACUTAP® OILTAP® + For insulation, lubrication and cooling, the contacts are in transformer oil + In the process, the high temperatures of the arc decompose some of the oil into gas and soot, which settles and can become conductive with moisture + For an OILTAP®, maintenance is required at shorter intervals because the oil must be changed + OILTAP® types: A, B, C, D, E, F, G, H, K, M, R, T, V 30-Oct-24 | 71 Transformer Mechanical Arrangement OILTAP® vs. VACUTAP® VACUTAP® + The arcing contacts are under vacuum in a vacuum cell + A VACUTAP® is generally maintenance-free, the maintenance criteria "time" is omitted + VACUTAP® types: AVT, VT®, VV®, VVS®, VM®, VR®V 30-Oct-24 | 72 Transformer Mechanical Arrangement Energy Accumulator & OILTAP® V Watch live Watch live Watch live Watch live 30-Oct-24 | 73 Transformer Mechanical Arrangement On-Load Tap-Changer for Dry-Type Transformer + A power transformer whose insulation consists of cast resin and in which no transformer oil is used + The insulation of the coils from one another is ensured by sufficiently large air gaps + Fire and groundwater hazard not applicable + For these transformers, an air-insulated OLTC was developed: the VACUTAP® VT® + Operational area: large shopping centers with high spatially concentrated power requirements in connection with high demands on fire load, environment, etc. 30-Oct-24 | 74 Transformer Mechanical Arrangement How do Transformer and Tap Changer interact? + Tap changers for power transformers are used to set the transformer ratio + The change of the voltage at the transformer takes place by changing the transmission ratio, that means by changing the number of turns at one of the two windings + With a tap changer, this can be realized with several taps on one winding + In the automatic mode of the controllable transformer, the voltage is measured and as soon as the control bandwidth is exceeded or undershot over a definable period of time, a switching command is transmitted to the on-load tap-changer 30-Oct-24 | 75 Transformer Mechanical Arrangement Cooling Methods Transformer cooling systems for oil immersed transformers + Cooling systems can increase the transformer capacity by 25% to 50% + Besides natural convection, also forced oil and air flow by pumps and fans are used + Overview of the different cooling arrangements configurations: − ONAN: Oil Natural (convection) Air Natural (convection) − ONAF: Oil Natural (convection) Air Forced (fans) − OFAF: Oil Forced (pumps) Air Forced (fans) − OFWF: Oil Forced (pumps) Water Forced (pumps) − ODAF: Oil Directed (pumps) Air Forced (fans) | Transformer Mechanical Arrangement Cooling Systems – Oil Circulation Pumps TRANSFORMER OIL CIRCULATION PUMPS + Cooling of transformers is the process by which heat generated in the transformer is removed, so that the transformer can perform to the best efficiency. + Heat is generated in the transformer while running and is produced by the excitation of the windings and core. + In transformers, a highly refined mineral oil or silicone oil is used for insulation and cooling. + For smaller transformers, passive cooling is sufficient. For more powerful transformers, the waste heat must be dissipated via a separate heat exchanger. + This is where oil circulation pumps are used. 30-Oct-24 | 77 Transformer Mechanical Arrangement Cooling Systems – Fans Transformer Fans + In fact, 80% of the heating inside a transformer station is caused by the transformer itself. + The remaining heat comes from the power losses of the switchgear, fuses, cables and connections. + The heat loss from transformer stations must be dissipated, so that the station room never heats up to above 45°C, even in unfavorable conditions (e.g. full load, hot weather, direct sunlight). 30-Oct-24 | 78 Transformer Mechanical Arrangement Cooling Systems – Radiators + Transformer radiators are heat exchangers which are used to maximize heat dissipation from the transformer oil to the external cooling medium. + Transformer oil carries the heat generated by electrical losses from within the transformer winding to the radiator. + The transferred heat through the radiator depends on oil flow rate, total surface area of the radiator, external cooling medium, ambient temperature, and mean oil temperature. + The heat transfer coefficient from the radiator surface to the external cooling medium determines the required total radiator surface area. 30-Oct-24 | 79 Transformer Mechanical Arrangement Cooling Systems – Oil-to-Air Heat Exchangers OFAF TRANSFORMER COOLER : OIL FORCED / AIR FORCED + Air-oil heat exchangers are used to maintain the temperature of the hydraulic oil in the temperature range recommended by the mineral oil producer. + These coolers use the ambient air by fans to cool the dielectric oil contained in the transformers. + OFAF transformer oil coolers are often used when the cooling capacities are high. + These heat exchangers are equipped in standard with our famous aluminum extruded finned tubes (POWERFIN) which avoid performance losses over the years. Depending on ambient conditions, other fin materials can be used, such as copper fins for salty environment. 30-Oct-24 | 80 Transformer Mechanical Arrangement Cooling Systems – Oil-to-Water Heat Exchangers Transformer Oil Water Coolers: OFWF + The coolers are required to control the temperature of vital equipment when loads and ambient temperatures are high, and where acoustic performance is important. + Power plants use transformers to convert electricity to a high voltage for efficient transportation. Oil is used to cool the transformer windings and dissipate heat, but this oil must itself be cooled and recirculated. + Transformer water coolers offer an efficient and reliable solution. They also play an essential role in controlling the temperature in electrical generation systems. + However, it‘s vital that the cooling water does not contaminate the oil, as this could destroy the transformer. 30-Oct-24 | 81 Transformer Mechanical Arrangement Cooling Methods ONAN (oil natural – air natural) ONAF (oil natural – air forced) OFAF (oil forced – air forced) ODAF (oil directed – air forced) | Transformer Mechanical Arrangement Cooling Methods Temperature characteristic OFAF: | Transformer Mechanical Arrangement Cooling Methods Temperature characteristic ODAF: | Transformer Mechanical Arrangement Cooling Methods Cooling of the windings – Vertical cooling: + Oil flows from the bottom to the top along the sides of the winding + Helical winding (with spacers): − Oil can enter the space between turns horizontally + Layer winding (without spacers): − Oil cannot penetrate between the turns − Typical for regulating windings (SLL – type) | Transformer Mechanical Arrangement Cooling Methods Cooling of the windings – Guided oil flow: + Oil flows from the bottom to the top “through” the winding + Oil flow is guided by guide collars + Cooling effect is sufficiently higher than with vertical cooling | Transformer Mechanical Arrangement Protective Devices – Buchholz Relay + The Buchholz protection is a mechanical fault detector for electrical faults in oil-immersed transformers. The Buchholz (gas) relay is placed in the piping between the transformer main tank and the oil conservator. The conservator pipe must be inclined slightly for reliable operation. + The Buchholz protection is a fast and sensitive fault detector. It works independent from the number of transformer windings, tap changer positions and instrument transformers. If the tap changer is of the on-tank (container) type, having its own oil enclosure with oil conservator, there is a dedicated Buchholz relay for the tap changer. + A typical Buchholz protection comprises a pivoted float (F) and a pivoted vane (V), as shown on the right. The float carries one mercury switch and the vane also carries another mercury switch. Normally, the casing is filled with oil and the mercury switches are open. 30-Oct-24 | 87 Transformer Mechanical Arrangement Protective Devices – Pressure Relay + Many power transformers with an on-tank-type tap changer have a pressure protection for the separate tap changer oil compartment. This protection detects a sudden rate-of-increase of pressure inside the tap changer oil enclosure. + When the pressure in front of the piston exceeds the counter force of the spring, the piston will move operating the switching contacts. The microswitch inside the switching unit is hermetically sealed and pressurized with nitrogen gas. + The simplest form of pressure relief device is the widely used frangible disk. The surge of oil caused by a heavy internal fault bursts the disk and allows the oil to discharge rapidly. Relieving and limiting the pressure rise prevents explosive ruptures of the tank and consequent fires. + Also, if used, the separate tap changer oil enclosure can be fitted with a pressure relief device. 30-Oct-24 | 88 Transformer Mechanical Arrangement Protective Devices – Oil Level Monitor Device + Transformers with oil conservator(s) (expansion tank) often have an oil level monitor. Usually, the monitor has two contacts for alarm. One contact is for maximum oil level alarm and the other contact is for minimum oil level alarm. + The top-oil thermometer has a liquid thermometer bulb in a pocket at the top of the transformer. The thermometer measures the top-oil temperature of the transformer. The top-oil thermometer can have one to four contacts, which sequentially close at successively higher temperature. + The figure below shows the construction of a capillary-type top-oil thermometer, where the bulb is situated in a “pocket” surrounded by oil on top of the transformer. The bulb is connected to the measuring bellow inside the main unit via a capillary tube. The bellow moves the indicator through mechanical linkages, resulting in the operation of the contacts at set temperatures. 30-Oct-24 | 89 Transformer Mechanical Arrangement Protective Devices – Winding Thermometer + The winding thermometer, shown in the figure below, responds to both the top-oil temperature and the heating effect of the load current. + The winding thermometer creates an image of the hottest part of the winding. The top-oil temperature is measured with a similar method as introduced earlier. The measurement is further expanded with a current signal proportional to the loading current in the winding. + This current signal is taken from a current transformer located inside the bushing of that particular winding. This current is led to a resistor element in the main unit. This resistor heats up, and as a result of the current flowing through it, it will in turn heat up the measurement bellow, resulting in an increased indicator movement. 30-Oct-24 | 90 Transformer Mechanical Arrangement Additional Equipment - Dehydrating Breathers + Transformer dehydrating breathers are used for liquid immersed transformers in order to protect the insulating liquid and prevent the harmful moisture absorption from ambient air, which occurs when the load on the transformer fluctuates. + The transformer dehydrating breather removes practically all moisture from the air that flows through it into the conservator when the transformer is cooling down. + This largely prevents any reduction of the dielectric strength and the formation of condensation in the expansion tank. + Thus, the dehydrating breather increases the operational safety of transformers. 30-Oct-24 | 91 Transformer Mechanical Arrangement Conventional vs. Maintenance-free Breather Benefits of retrofitting: + Maintenance-free dehydrating breathers continuously dehumidify and monitor the breathing cycle of power transformers in all climatic zones. + Reduces operating costs and increases operational reliability. + They regenerate themselves. This ensures maximum operating times and safety and massively reduces costs. + Actively protects the insulation medium against humidity. + Condition-dependent and self-learning algorithm. + Simple to retrofit on existing equipment. 30-Oct-24 | 92 Transformer Mechanical Arrangement Additional Equipment - Oil to Air Separator Bag + The STP rubber bag transformer is used to protect the dielectric oil in power transformers. It is also called a flexible separator or compensation balloon. + The STP inflates and deflates by compensating for the change in volume. It provides separation between air and oil inside the hydraulic conservator. + This avoids: − Oil pollution − Condensation − Oxidation − Hydrolysis + Thus, the system protects the dielectric oil from external contamination. 30-Oct-24 | 93 Transformer Manufacturing Process Agenda: + Core assembling + Winding + Core coil assembly + Ovening and drying + Tank Assembly + Final Assembly + Testing and inspection + Painting & Dispatch Images 30-Oct-24 | 94 Transformer Manufacturing Process Core Assembling + This is the main assembly frame. The assembly consists of the core, clamping structure, feet, and the supporting structure for the framework to support tap and line terminals. + The core plays a vital role in selecting the material. The grade defines the material lost per kilogram while energizing the transformer. The increasing tariff of power has compelled manufacturers to build economical transformers and design them for optimum losses. + The core is mitered and assembled in step lap formation. The mitered joints are provided with minimum gap. + The clamping structure is a fabricated steel frame made from standard IS angle, channels or plate construction. The frame is held vertically and horizontally using tie rods. The vertical tie rods also exert adequate force on the coils during clamping to counter the stresses generated during operation. The transformer rests on its feet. The clamping structure supports the framework to route tap and line terminals 30-Oct-24 | 95 Transformer Manufacturing Process Winding Primary and secondary windings + The main components in a transformer are the primary and secondary windings. The windings are manufactured from electrical grade high conductivity copper and aluminum materials. + The winding conductor is drawn to various sizes in round and rectangular shapes. The choice of conductor and insulation covering depend on the voltage class, current, cooling and insulation clearances. + The cross section of the winding provides the necessary area to handle the current. The conductor is wound into coils. + The coils are transposed during the winding to maintain low eddy current loss. + The windings are supported on insulated cylinders to ensure proper handling during assembly, besides providing insulation. 30-Oct-24 | 96 Transformer Manufacturing Process Core Coil Assembly + The core coil assembly (CCA) is the winding assembly on the core. This is a vital part of the transformer also known as the active part. + The construction of the CCA is significant from the performance point of the transformer. The CCA defines the insulation scheme, cooling, dynamic withstand capability, handling. Insulation scheme is categorized into major and minor insulation. Major insulation addresses the capability to withstand high voltages, insulation of the primary and secondary winding, clearances for voltage withstand. Minor insulation is the turn insulation, joint protection etc. Both the major and minor insulation are equally important for the successful operation of the transformer. + The transformer experiences dynamic forces due to frequent loading and unloading. The sudden loading and withdrawal of load creates a tensile stress on the winding in the form of buckling forces or bursting forces. The construction of the CCA by providing sufficient radial and axial supports prevents the stress from causing any damage to the windings. + The assembly also provides facility to handle for ease of lowering the assembly into the tank and vice-versa. 30-Oct-24 | 97 Transformer Manufacturing Process Ovening and Drying Procedure for the ovening and drying process + This is a very important process in the manufacturing of transformers. The transformer undergoes a drying process at various stages depending on the rating and voltage class. + Drying is essential as a significant part of the insulation used in the transformer is paper and wood-based. + The insulation material has high affinity to moisture which may weaken the insulation properties and reduce the insulation resistance to high voltages. This causes failures in the form of flashing at high voltages. + There are two types of drying: Air drying and vacuum drying. Air drying is used in distribution transformers limited to voltage class below 33 KV, while vacuum drying is predominantly used for all power transformers of voltage class above 33 KV. 30-Oct-24 | 98 Transformer Manufacturing Process Tank Assembly Tank Assembly + The enclosure on a transformer is generally referred to as tank. This is a fabricated structure constructed of mild steel of adequate thickness to form a rectangular shaped tank. + The tank has two main functions: − hold the CCA with proper clearances for voltage and oil flow. − If acilitate cooling, safety and maintenance. The tank must be leak proof and should withstand pressure. 30-Oct-24 | 99 Transformer Manufacturing Process Final Assembly Final Assembly + The CCA is inserted into the tank assembly. All clearances inside are checked. The CCA should stand freely inside the tank. The primary and the secondary terminations are brought out through porcelain or epoxy cast bushing insulation. Tap switch connections for external operation and or OLTC connections to the insulated board are provided on the tank. Handling, jacking facility to lift the tank assembly or jack it for fixing detachable rollers is provided. The transformer tank is fitted with valves for oil filling, filtration, oil sampling, draining. Provision for safety devices such as Buchholz relay, pressure relief valve, temperature recording and control instruments, neutral current transformer, protection and instrument transformer are available as customized features. + To ensure excessive pressure does not cause any damage, a conservator is provided for oil expansion and contraction during the operating cycle. In case of the OLTC, a separate conservator is also provided, in the main conservator. Terminal identifications are done on the bushings. 30-Oct-24 | 100 Transformer Manufacturing Process Testing and Inspection Testing and inspection + Installing a transformer is more than just connecting the wires according to the wiring diagram. + The first part of the installation process includes an initial inspection and testing of the transformer when it is received from the factory or warehouse. + After a successful inspection, the installation can begin. 30-Oct-24 | 101 Transformer Manufacturing Process Inspection + When a transformer arrives at a factory or job site, there are several things that should be inspected before accepting the shipment. For larger power transformers, there are some electrical tests that should be performed to verify that the unit was manufactured correctly and is in satisfactory condition. It is best to inspect and test a transformer before installation and before it is energized for the first time to ensure that it is in good working order. + A complete drawing of the coils and the regulator is found on the transformer nameplate. The nameplate gives the installer all the data relating to the transformer, including the rating, impedance, primary and secondary voltage, the phasing, the permissible temperature rise, oil type (if used), weight, and connection diagrams. Also included are the name of the manufacturer, the model number/type, and the serial number. 30-Oct-24 | 102 Transformer Transportation & Shipping Transformer Rigging TRANSPORT + Dimension depending on transformer power + Transformers with high power + Five-leg design to reduce the transport height + Transformers > 500 MVA often deviate from the optimum iron/copper ratio of 2/1 due to transportability + Limit weights are reached + Design of a 1,000 MVA transformer with 1,000 mm higher active parts would weigh approx. 50 tons less + Future: Will the current boundaries remain in place? 30-Oct-24 | 103 Transformer Transportation & Shipping Transformer Rigging TRANSPORT MEDIUM AND MAX. WEIGHTS Flatbed truck Street / Railroad up to 150 t Schnabel cars Street / Railroad up to 300 t with through- loading beam Schnabel cars Street / Railroad up to 500 t Roll-on / Roll- Street - Water up to 500 t off 30-Oct-24 | 104 Transformer Transportation & Shipping Transformer Rigging + Dismantling of feedthroughs and all interfering components in the transport profile + Enclosure of the cabinets with transport boxes + If necessary, lowering of the oil level / emptying of the vessel + Filling with dry air or nitrogen for transport 30-Oct-24 | 105 Transformer Transportation & Shipping Transformer Rigging Risks to Goods During Transports + There is an increasing trend to transport goods around the globe by land, sea and air on a daily basis. + During the journey to their destination, the goods are exposed to a wide variety of influences and impacts such as different temperatures, vibrations and centrifugal forces. + It is the aim of every transport that the goods reach their destination without being manipulated and without any damage. 30-Oct-24 | 106 Transformer Transportation & Shipping Transformer Rigging 30-Oct-24 | 107 Transformer Transportation & Shipping Transformer Rigging Transport + Existence of any damage on the main tank or inside the active part + Check transformer body and accessories visually 30-Oct-24 | 108 Transformer Transportation & Shipping Transformer Rigging - MLOG MESSKO® MLog - High End Transport Monitor for your Good(s) + The MESSKO® MLog offers the perfect solution for reliable transport tracking and condition monitoring of shipments, goods and valuables of all kinds. + The device stores and visualizes numerous parameters and events. Thanks to the GPS function, the transported goods can be located worldwide, and the transport route can be tracked. + Permanent monitoring of transports leads to significantly reduced transport damage + Seamless documentation of accelerations, shock events, temperature and humidity eliminates the possibility of manipulation + Adjustable alarm limits and recording intervals to adapt to individual requirements 30-Oct-24 | 109 Transformer Transportation & Shipping Transformer Rigging - MLOG Detection & Storage of Parameters, Events and Limit Violations + IM100 Display Sample View: + Acceleration / shocks in 3 orthogonal directions (X-, Y-, Z- axis) + Configurable shock duration time filter + Ambient temperature + Relative humidity + GPS position tracking (optional) + Free parameterizable analog and digital inputs (optional) Features of the MESSKO® MLog + Robust case with protective cover + Display (MLog IM100) with intelligent battery prognosis and alarm counter on the home screen + GSM module for event notification via SMS + Battery change function + Software license for MESSKO® MLog Analyzer included 30-Oct-24 | 110 Transformer Transportation & Shipping MLog Analyzer Software (MLog IM100 / IM50) GPS Route Information in Google Earth + Analyze the transport route in Google Earth* + Available on MLog IM100 & IM50 with GPS function + Just one mouse click in the MLog Analyzer to generate Google Earth route* + Detail Information with Date & Time *: Google Earth installation required 30-Oct-24 | 111 Transformer Services Installation & Commissioning Your benefits at a glance: + We offer you turnkey transformer installation. + We take care of construction supervision and provide technical support. + We offer multi-year service contracts during installation and commissioning. + Commissioning includes extensive electrical testing and oil filling. + When commissioning your transformer, we carry out various electrical measurements on site. + The measurement results are compared with the electrical measurements at the factory and made available as a fingerprint for future measurements. 30-Oct-24 | 112 Transformer Commissioning & Installation Transformer Rigging Montage and Installation Montage and Installation + Transformer 110 kV + Primary and secondary connection + Primary and secondary connection + Bushings + Bushings + Conservator + Dome + Oil work + Cooling system + IBN tests + Piping system + Oil sampling and analysis + Protection and monitoring devices + Conservator + Oil Sampling and analysis 30-Oct-24 | 113 Transformer Commissioning & Installation Transformer Rigging Transport + Small power transformers can be transported full or partially filled with oil + Larger ones are transported empty of oil + In order to preserve the integrity of the active part during transport, the transformer, when shipped empty of oil or partially filled with oil, is put under a positive dry gas (air or nitrogen) pressure before being shipped. + An automatic system supply ensures that the pressure of the gas inside the transformer is continuously positive. 30-Oct-24 | 114 Transformer Commissioning & Installation Transformer Rigging Transformer checks after arrival on site + After arrival at the customer site, transformers are checked in order to see: + Transformers sent to the site along with main tank, accessories and insulation oil + Accessories boxes and oil barrels are controlled according to checklist which is prepared by factory dispatch team 30-Oct-24 | 115 Transformer Services Visual Inspections + Visual inspection Transformer Cooling Tap Auxiliary Control Monitoring Bushings Specifics tank system changer Equipment room Systems 30-Oct-24 | 116 Transformer Services Visual Inspections Rating key: 1 - Well readable 2 - Partially poorly readable 3 - Most parts not readable 4 - Not readable 0 - Not accessible 1 2 3 30-Oct-24 | 117 Transformer Services Visual Inspections Rating key: 1 - Paint is good - No corrosion - No damage 2 - Paint is peeling off - Visible corrosion - Slight damage 3 - Big sections without paint - Big sections with corrosion - Damage 4 - > 20% without paint - > 20% corrosion - Severe damage 2 3 4 30-Oct-24 | 118 Transformer Services Visual Inspections Rating key: 1 - No leaking visible 2 - Sweat, but no oil spill 3 - Visible oil spill 4 - Visible oil spill / visible oil leaks 2 3 3 30-Oct-24 | 119 Transformer Services Visual Inspections Rating key: Please Note: 1 - Silica gel blue or orange / no damage visible / good oil level in the oil cup The change of the color must start at the bottom 2 - Up to 50% discolored / discolored in the middle 3 - Discolored on the top / bad oil level in oil cup / damages Orange: Silica gel is ok; White: Silica gel is used. 4 - > 70% discolored / no silica gel / no oil in the cup / severe damage Blue: Silica gel is ok; Pink: Silica gel is used. 4 2 3 30-Oct-24 | 120 Transformer Services Visual Inspections Rating key: 1 - Blocking device is installed 4 - Blocking device is not installed n.a. - Transformer is without wheels 1 4 30-Oct-24 | 121 Transformer Services Visual Inspections Requirements on the methodology for Visual Inspection + Comparable results throughout the whole fleet + Repeatable results are ensured + Similar rating if condition doesn’t change + Objective results independently from the individual expert + High quality documentation allows + Traceable assessment results (Picture documentation) + Quick access to former assessment results (Organized database) + Trend analysis shows change of condition (Timestamps of measuring) 30-Oct-24 | 122 Practical Training Routine Services & Visual Inspections 30-Oct-24 | 123 Maintenance Strategies Periodical Inspections External Checks Inspection Item Method Action Period Bushing insulators 1 year Check the cleanness periodically. The period has to Refer to the relevant instruction manuals be chosen depending on the pollution conditions on site. Electrical connections 1 year Checking all electrical connections for signs of Clean the contact area (Bushings, etc.) corrosion Grease the contact area Tighten the connection Silica gel breather 3 months Condition of silica gel breather If more than 2/3 of total silica gel pellets are of (for conventional breather) transparent appearance, exchange it. If appearance is transparent beginning at the upper level, trace for air leaks and act accordingly External grounding 1 year Checking proper contact of grounding connections Clean the contact area system at tank, cover, control cubicle, manhole covers, Grease the contact area bushing flanges, protection devices, etc. Tighten the connection Cooling equipment 2 years Dust and other external materials collected on the Clean with compressed air and /or water equipment must be removed for proper cooling operation 30-Oct-24 | 124 Maintenance Strategies Periodical Inspections Inspection Item Method Action Period Oil level indicator 1 year Visual inspection Oil temperature indicator 1 Year Visual inspection Check all values Winding temperature indicator 1 year Visual inspection Check all values Pressure relief device 3 years Function test Press test button - check tripping Buchholz relay 1 year Visual inspection Perform gas analysis in case of gas accumulation Press test button - check alarm/tripping 3 years Function test OLTC protection relay 3 years Function test Press test button - check tripping Cubicles housing electrical 1 year Visual inspection Check that heating switches on and off with signal from equipment Heater check thermostat / hygrostat Gaskets ½ year Visual inspection for leaks Replace gaskets in case of serious oil leaks Leaks 3 months Visual inspection of all joints, pipe connections, etc. Carefully tighten the leaking area checking of oil level in the conservator Replace the gasket Gas accumulation 1 year Checking of air relief plugs on cover, bushings, pipework, Open the relief plugs till bubble-free oil streams out cooling equipment, Buchholz relay Check Buchholz relay Corrosion protection 1 year Visual inspection Damage and rust formations are to be repaired (painting to be of the same type as the original coats) Bolted connections 1 year Manual inspection Tighten the connection 30-Oct-24 | 125 Maintenance Strategies Periodical Inspections Measurements & Electrical Tests Inspection Property Method Action Period Humidity 3 years Measure the water content (titration method Karl If the measured value is too high, the oil needs to be (in case of filling or Fischer, should be 60 50 30 40 100kV) WG A2.37 REPORT 30-Oct-24 | 149 Transformer Bushing Replacement To avoid following: 30-Oct-24 | 150 Transformer Bushing Replacement Micafil Bushing Lifetime Example Maximum lifetime acc. to the design is in the range of 25 years With increasing age, the risk of an incident is increasing 30-Oct-24 | 151 Transformer Bushing Replacement HSP Bushing Lifetime Example Maximum lifetime acc. to the design is in the range of 25 years With increasing age, the risk of an incident is increasing 30-Oct-24 | 152 Transformer Bushing Replacement OIP Bushing Design + Core insulator + Secondary insulation − OIP (Oil Impregnated Paper) − Oil + Transformer end housing + Outdoor end housing − Porcelain − Porcelain insulator − Epoxy Resin − Silicone insulator 30-Oct-24 | 153 Transformer Bushing Replacement RIP & RIS Bushing Design + Core insulator + Secondary insulation − RIP (Resin Impregnated Paper) − Gas − RIS (Resin Impregnated Synthetic) − Dry material filler (SF6-free) + Transformer end housing + Outdoor end housing − Epoxy Resin − Porcelain insulator − No housing − Silicone insulator 30-Oct-24 | 154 Transformer Bushing Replacement OIP to RIP & RIS Design (Example 01) + Draw Lead size − OLD 600 mm² vs. NEW 925 mm² + Distance to Earth − OLD 340 mm vs. NEW 420 mm + NEW Bushing is possible to use with draw lead modification and clarification of distance to ground! 30-Oct-24 | 155 Transformer Bushing Replacement OIP to RIP & RIS Design (Example 02) + Transformer 1.527 A − Load Case 1: 1.847 A − Load Case 2: 1.916 A − Load Case 3: 1.916 A + Bushing OLD 2.000 A + Bushing NEW 1.900 A + NEW Bushing is not possible to use if customer wants to overload transformer with 1.255 p.u.! + Overload with max 1.244 p.u. would be possible! 30-Oct-24 | 156  Transformer Bushing Replacement OIP Bushing - Oil Samples Guide for the Sampling of Oil from Trench COTA Bushings DGA BDV IFT Sulphur Moisture + Evaluation of DGA Results for COTA Bushings 30-Oct-24 | 157 Transformer Bushing Replacement OIP Storage Recommendations Long-term storage, more than 6 months As an alternative: + The bushing can be stored outdoors, if kept in the + Keep the bushing in the transport box and lift it to an transport box inclined position, with the top end upwards and at an + Keep the transport b