Pomona, CA May 24 25, 2016 Transformer Technology Seminar Siemens AG Transformers siemens.com/answers
Windings: Page 2
Example GSU 274/464MVA H0 H1 H2 H3 U U I I H L H L N = N N = N L H H L HV: 405kV ±8x1.25% LV: 22kV turns Imax 560 735A 4 4 4 5 5 5 6 7 8 9 10 11 6 7 8 9 10 11 6 7 8 9 10 11 I Phase-max = S 3 U max Phase-min 8x7 735A X1 X2 X3 53 12,176A I I HV -Phase max HV -Phase max 464000000VA = 3 (405000V 0,9 / = 735A 3) Page 3
H0 Example Autotransformer 240/320/400 MVA (Tertiary 20/26.6/33 MVA) H1 H2 H3 HV: 360kV ±2x2.5% LV: 240kV ±8x0.625% TV: 36.2kV turns Imax a b c d e f a b c d e f a b c d e f a b c d e f a b c d e f a b c d e f 4x15 450 4x15 675A 11 10 9 8 7 6 5 4 11 10 9 8 7 6 5 4 11 10 9 8 7 6 5 4 4x10 5x10 1070A 780 460A 205 526A X1 X2 X3 Page 4
Layer Windings for Low Voltages: Single Layer Windings Core Commonly used As stabilizing windings Coarse winding in a coarse-fine regulation Low and middle voltage windings If it is located at the core it has low stray field loss, therefore flat conductors can be used in many cases Page 5
Example: Single Layer Winding for a GSU with 4 axial parallel conductors, with radial cooling ducts and Net Covered CTC Axial Strips Radial Spacers Core Page 6
Layer Windings for Low Voltages: Double Layer Windings Commonly used in large GSU s LV winding of large transformers Core Provide more surface for cooling than a single layer The magnetic field of the lead exits is largely compensated due to the opposite current in these leads: less loss in metallic structural parts. Structural Part Page 7
Transpositions in Layer Windings If more than two radial conductors are used, transposition is required to compensate the circulating current in the loop If many axial conductors are used in multi-layer windings, a transposition between layers may be required to compensate currents induced by the radial field of the windings Page 8
Example: Single Layer Helical winding with 6 radial CTCs Transposition in case of 3 radial CTCs Transposition in case of 6 radial CTCs Page 9
Layer Windings for Low Voltages: Multi Layer Windings Provide more surface for axial cooling than a single layer Core In case more than two layers are used, the voltage stress between layers reduces Mainly used in medium voltage and low voltage transformers Page 10
Disc windings Commonly used in HV windings Sometimes in LV windings with low number of turns per disc Sometimes in tap windings Core Page 11
Example: Disc Winding 1 radial CTC Radial cooling ducts 4 axial cooling ducts Conductor Clack band Spacer Page 12
Example: Disc Winding 4 radial flat conductors Radial cooling ducts 2 axial cooling ducts Clack band Page 13
High voltage: Control of Voltage Transients BIL Disk Type a b c U s Impulse Voltage Distribution O Us a b c b U s a Core I a b c Continuous disk Radially interleaved disk Final inductive distribution Page 14
High voltage: Control of Voltage Transients Simple double discs Can be used in LV windings AT Common Windings Interleaved double discs Used at winding ends Combination of simple and interleaved double discs Page 15
High voltage: Control of Voltage Transients Example: Radial shield wire between the turns of a disc An insulated flat wire is used between the CTC conductors of the disc 4 radial flat conductors Radial cooling ducts 2 axial cooling ducts Page 16
High voltage: Control of Voltage Transients Example: Twin CTC with shield wires Page 17
High voltage: Control of Voltage Transients Example: Winding without radial ducts Higher series capacitance with entry in second disc Page 18
Overview of tap windings: Body tap Top entry with Body Tap Middle entry with Body Tap Used for de-energized voltage regulation usually within 10% (e.g. ± 2 x 2.5%). Simple or interleaved discs Bridging tap changer is used. Because of the outgoing leads it s commonly the outermost winding. Tapping discs have to be symmetrically distributed along the winding height to balance mechanical forces. Page 19
Overview of tap windings: Linear or direct-reverse tap winding Top entry with linear or direct-reverse tap winding Middle entry with linear or direct-reverse tap winding Page 20
Overview tap windings: Coarse-fine regulation Top entry with corse fine tap winding Page 21
Types of Layer Tap Windings: Multistart Tap Winding ll 1-Layer design Conductors are interleaved to control the series capacitance Page 22 Mainly used as inner tap windings, e.g. in a Autotransformers ZnO Varistors are used often between taps at higher voltage classes 2-Layer design Connection leads on one side can be avoided
Types of Layer Tap Windings: Continuously Tapped Layer Used as outer tap winding, e.g. in a GSU The series Capacitance is low, therefore ZnO Varistors are used between taps at higher voltage classes Low space requirement, simple to manufacture Page 23
Damping of high frequency oscillations induced by lightning strokes ZnO Varistors is used at higher voltage levels in all types of tap windings if the series capacitance is low Page 24
Damping of high frequency oscillations induced by lightning strokes ZnO varistors are used at higher voltage levels in all types of tap windings if the series capacitance is low Page 25
Siemens AG MPT Transformers Contact Kurt Kaineder Head of Engineering Head of Electrical Design Global Technology Center MPT Siemens AG Oesterreich Transformers Linz Kraussstraße 7 4020 Linz Phone: +43 (5) 1707-71098 Fax: +43 (5) 1707-55391 Mobile: +43 (664) 615 4946 Mobile: +43 (664) 80117 71098 E-mail: kurt.kaineder@siemens.com siemens.com/transformers
Siemens US Transformers Contact James McIver Principal Application Engineer E T TR US 6860 Bermuda Road, STE 100 Las Vegas NV 89119 USA Mobile: (702) 241-0157 E-mail: james.mciver@siemens.com Siemens.com/transformers Page 27