Regional Technical Seminar

Transcription

1 Regional Technical Seminar TRANSFORMER 101

2 Transformer 101 Dharam Vir Vice President of Engineering

3 Agenda 1.Review transformers: How they work (textbook vs reality) 2.How do we build a reliable transformer Virtual Tour 3.Specification requirements and Accessories 4.Types of Core Winding and material 5.Insulating Materials 6.Testing requirements 7.IEEE Activities Update 3

4 Textbook Transformer (step by step) Ø1(t) Ø2(t) 5 1 N 1 N 2 7 leakage field 4 4

5 Cutaway View How one is really built 5

6 Virtual Factory Tour

7 Requirements by Specification 7

8 Specification Requirements Phase Relations 8

9 Specification Requirements Top Oil Rise Over Ambient = 65C Winding Hot Spot Rise Over Ambient = 80C Per IEEE: Max Ambient = 40C Max 24 hour Avg. Ambient = 30C Min Ambient = -20C Top Oil Temperature = 95C Avg. Winding Temperature = 95C Winding Hot Spot Temperature = 110C High Ambient: Max Ambient = 50C Max 24 hour Avg. Ambient = 40C Must calculate rises not to exceed above absolute temperatures Increase cooling equipment Increase conductor Derate transformer rating Effect of Ambient Temperature Avg. Winding Rise Over Ambient = 65C 9

10 Specification Requirements State the service conditions of your site Ambient (min, max, average) Altitude Supply Voltage and harmonic content Over-excitation requirements Overloading Capability October 29,

11 Specification Requirements Unusual Service Conditions (C Section 4.3) Unusual Ambient (Examples: -40C, 35C Average, 50C Max) Altitude greater than 3300 feet - Greater External Clearances - High Creep Bushings and Arresters Environment: Salt, dust, fumes Abnormal Vibration, tilt or shock, Seismic Retrofit requirements Motor Starting Capability or unusual duty Unbalanced loading conditions (open phase loading) Harmonic content in excess of 0.05 per unit Unusual switching conditions Geomagnetically Induced Current (GIC) Requirements Paralleling Requirements Series Multiple Application October 29,

12 Specification Requirements Physical Limitations Matching Existing Unit Paralleling with Existing Transformers Special Impedance Tolerance Requirements 12

13 Specification Requirements Location of Job Site Shipping limitations 13

14 Specification Requirements FOB Job Site / Rail Side FOB Pad Unloaded by Supplier or Purchaser? FOB Pad Assembled and Tested 14

15 Accessories Bushings Filter Valve Radiators Pressure Relief Devices Temperature Gauges Rapid Pressure Rise Relay DGA Monitor Control Box Jack Pad Fans Accessories C

16 Accessories Liquid Level Gauge Oil Preservation (COPS Tank) Auto- Recharging Dehydrating Breather (ARDB) LTC LTC Motor Drive Accessories C Drain Valve DETC Operating Handle 16

17 Accessories DGA Monitoring Outlet Temperature Monitoring and Data Collection Fiber Optic Temperature Controller Inlet Winding and Oil Gauges and Probes Monitoring Equipment 17

18 Accessories Inert Gas Conservator Gas Space Bladder / Air Space Oil Space Oil Space Oil Space Gas Bottle ARDB Oil Preservation Systems 18

19 Accessories Air Terminal Chambers 19

20 Accessories Cable Entry Location Anti-condensation Heaters Half-Height/Full-Height Hinged Doors Access Covers for Cable Termination Arresters Bushings Fuses Air Terminal Chambers 20

21 Different types of Core Construction Single Phase, 2-Limb Core form Single Phase, 3-Limb Core form Three Phase, 3-Limb Core form Single Phase, 4-Limb Core form Three Phase, 5-Limb Core Form Core Types 41

22 Core Design Grade of Core Steel H1 Laser Scribed, 11 mil Limb Pitch / Leg Center Distance Core Diameter Core Design Considerations: Flux Density No Load Loss Sound Excitation Current Temperature Rise Internal Outer Packet Tie Plate Clamps Tie Plate Lifting + Clamping Stress Short Circuit Stress Core Types Max Width Min Width Core Steps Number of Legs Limb / Window Height 42

23 Type of conductors Copper Strip or Foil Bus bar Rectangular wire (MW) Continuously Transposed Cable (CTC) CTC Conductor Selection 43

24 Type of Conductors ARRANGEMENT APPLICATION PICTURE CORDEX only with protection paper LV or TV winding CORDEX1 with 2 layers papers at the bottom in radial dimension CORDEX2 with 2 layers papers in axial dimension LV winding when its better to split CTC in two due to the big radial dimension Layer winding CORDEX3 with aramid paper at the bottom in radial dimension HV disk winding Conductor Selection 44

25 Types of Windings Winding Types Layer/Barrel Regulating (RV) and Tertiary windings (TV) Screw (Helical) LV, Series (Booster) transformer Continuous Disc HV, LV, Series (Booster) Above winding types may use magnet wire or CTC Winding Selection 45

26 Layer Type Winding SLL / Layer / Barrel SLL / Layer / Barrel Winding Selection 46

27 SLL / Layer SLL / Layer / Barrel Winding Selection 47

28 Helical / Screw Winding Selection 48

29 Helical Winding with two CTC s Winding Selection 49

30 Continuous Disk Winding Inner cross-over Outer cross-over Winding Selection 50

31 Disc Winding with Magnet Wires Winding Selection 51

32 Set of Windings Set of Windings for a given Transformer 52

33 WA FRM CYL CYL GAP CYL CYL CYL FRM CYL CYL CYL GAP CYL CYL CYL FRM CYL CYL CYL CYL GAP GAP GAP GAP GAP GAP GAP GAP GAP GAP GAP GAP GAP GAP GAP COLLAR Insulation Materials Major Insulation Insulation of windings to ground, core, other windings within the phase and to other phases Materials Pressboard (cellulose) High density (TIV) cylinders Medium density (Hi-Val) collars Layered TIV (TX2) rings, washers Nomex for higher temperatures WA WA SR WDG TV HELIX WA SR WDG LV DISK PB RING PB BLOCKS WA WA SR WDG HV DISK Laminated Wood rings Kraft Paper (cellulose) leads Copaco (cotton based paper) leads Resin/epoxy materials on metal parts SR WA WA PB BLOCKS PB RING SR WA WA WA 53

34 Insulation Materials Minor Insulation Insulation between different parts of one winding between turns, strands of conductors, discs or layers Materials Kraft Paper conductor insulation/spinning Nomex spinning, spacers Formvar conductor insulation Epoxy (CTC) conductor insulation Copaco (cotton based paper) leads Pressboard High density (TIV) spacers Medium density (Hi-Val) collars, etc. Layered TIV (TX2) structural parts Inner Xover Spinning Fill Conductor Lead Spacer Outer Xover 54

35 Insulation Materials Insulating Fluids Mineral Oil Natural Ester Advantages of Natural Ester Slows aging of cellulose (equiv. to roughly 10 C lower winding rise) Higher Flashpoint (330 C vs 140 C) Environmental advantage/containment Drawbacks: Cost Higher viscosity Solidifies below -20 C Other Materials Lead Insulation Kraft Paper Copaco Nomex Pressboard Lead Supports Maple Laminated Wood TX2 Bushings, Insulators Resin/epoxy materials Porcelain 55

36 Internal Details Component Layout Shipping Profile Most wiring/connections not complete Tank Sizing 60

37 Internal Details Verify Clearances: Between Leads, Between Leads and Ground, etc. Complete Wiring/Connections Finalize Design 61

38 External Details Component Layout Model to Generate Outline Drawing Typically Conduit and Wiring Not Complete 62

39 External Details Identify Items to be Removed for Shipping Stainless Steel Where Required Finalize Design Finalize Hand Holes/Man Holes, Conduit, Stiffening, etc. Verify Components Fit in Shipping Profile 64

40 Transformer Tests Dielectric Tests Performance Characteristics Thermal Tests Other Tests Transients Lightning Impulse 1. Full Wave 2. Chopped Wave 3. Front of Wave 4. Switching Surge Low Frequency (Power) Tests 1. Applied Potential 2. Induced Potential 3. RIV/Partial Discharge 1. No-Load Losses 2. %Exciting Current 3. Load Losses 4. % Impedance 5. Zero Sequence Impedances 6. Ratio Test Phase Rotation 1. Winding resistance 2. Heat Run Oil Rise Average Winding Rise Winding Hot Spot Rise 3. Over Load Heat Run 4. Time Constant Heat Run m&n exponents 5. DGA 6. Thermal Scans 1. Insulation Power Factor (Doble?) 2. Sound Level 3. Megger 4. Core ground 5. Core Loss before & After Impulse 6. Auxiliary Losses 7. Low Voltage Dielectric Test Controls CT Wiring 8. Operational Test 1. LTC 2. Controls 3. Accessories 9. CTs 10.Dew Point kv Single phase excitation (Doble?) 12.Leakage reactance (Doble?) 13.SFRA (Doble?) 14.Framit 65

41 Questions?

42 IEEE Update

43 IEEE Update Development of PC Tertiary / Stabilizing Windings C General requirement for Liquid filled Transformers Class I and II Definition C Section 5. Routine, Design, Other tests C Table 17 Dielectric Test Table C Table 3 & 4 Operation above rated voltage C Thermal Rating of Tertiary C Section adder related to additional error in measurement for transformers with reactance type tap changer C Core Hot spot temp shall be 130C for highest over excitation, rated load and Max average daily ambient temp C Short-circuit apparent power of the system C Table 14 revised based on Maximum circuit breaker capacity and faults levels from user survey Zero Sequence C Neutral to be grounded, if permanently grounded. C Temperature rise Test C C Test code for Liquid immersed Transformers Dielectric Test Sequence C Section ;C Section :10.3 Transformer Tap during Impulse C Sound Test C :Section 13.0 Sound Correction C sec 13.5 C Geomagnetic Disturbances Published Application of High-Temp Insulation Materials, IEEE C

44 IEEE Update Factors Influencing the Degree of Risk to the Grid and Equipment: Geomagnetic Latitude Local Earth Resistivity Coastal Effect Network Topology Design and Specification of Key Equipment Storm Duration Loading C GIC Guide 70

45 IEEE Update C GIC Guide 71

46 IEEE Update C GIC Guide 72

47 IEEE Update C GIC Guide 73

48 Questions? Thank you!

49 Appendix

50 IEEE Transformer Committee 76

51 IEEE Standards Web Site 77

52 IEEE Standards Archives Web Site =7 78

53 NEMA Standards Web Site 79

54 RUS Guides Web Site 80

55 RUS Guides Web Site 81

56 ASTM Standards Web Site 82

57 ASME Standards Website 83

58 Wild Life Outages 84

59 Wild Life Outages 85

60 Wild Life Outages 86

61 Relevant Current Industry Standards IEEE Std IEEE Standard Techniques for High-Voltage Testing. IEEE Std C IEEE Standard General Requirements for Liquid-Immersed Distribution, Power, and Regulating Transformers NOTE: This standards applies to all liquid-immersed distribution, power, and regulating transformers that do not belong to the following types of apparatus: a) Instrument transformers b) Step voltage and induction voltage regulators c) Arc furnace transformers d) Rectifier transformers e) Specialty transformers f) Grounding transformers g) Mobile transformers h) Mine transformers 87

62 Relevant Current Industry Standards IEEE Std C IEEE Standard Requirements for Liquid-Immersed Power Transformers ANSI Std C American National Standard for Overhead-Type Distribution Transformers, 500 kva and Smaller: High Voltage, Volts and Below; Low Voltage, 7970/13 800Y Volts and Below Requirements. ANSI Std C American National Standard Terminal Markings and Connections for Distribution and Power Transformers. IEEE Std C IEEE Standard Test Code for Liquid-Immersed Distribution, Power, and Regulating Transformers 88

63 Relevant Current Industry Standards IEEE Std C (Reaff 1999) IEEE Guide for Transformer Impulse Tests IEEE Std C IEEE Standard Requirements for Instrument Transformers IEEE Std C , IEEE Standard Performance Characteristics and Dimensions for Outdoor Apparatus Bushings IEEE Std C , IEEE Guide for Loading Mineral Oil-Immersed Transformers IEEE Std C , IEEE Guide for Transformers Directly Connected to Generators 89

64 Relevant Current Industry Standards IEEE Std C Recommended Practice for Performing Temperature Rise Tests on Oil Immersed Power Transformers at Loads Beyond Nameplate Ratings IEEE Std C IEEE Loss Evaluation Guide for Power Transformers and Reactors IEEE Std C IEEE Standard Requirements for Load Tap Changers IEEE Std. C IEEE Guide to Describe the Occurrence and Mitigation of Switching Transients Induced by Transformers, Switching Device, and System Interaction IEEE Std C IEEE Guide for the Application of Metal-Oxide Surge Arresters for Alternating-Current Systems NEMA Standards PublicationTR1-2013, Transformers, Regulators and Reactors ANSI/CGA V Compressed Gas Cylinder Valve Outlet and Inlet Connections. 90

65 Relevant Current Industry Standards ASME Boiler and Pressure Vessel Code (BPV), 2001 Edition. ASME B American National Standard for Unified Inch Screw Threads (UN and UNR Thread Form). 91

66 Relevant Current Industry Standards ASTM D92-05A Standard Test Methods for Flash and Fire Points by Cleveland Open Cup. ASTM D Standard Guide for Sampling, Test Methods, Specifications, and Guide for Electrical Insulating Oils of Petroleum Origin. ASTM D Standard Test Method for Corrosive Sulfur in Electrical Insulating Oils ASTM D Standard Specification for Nitrogen Gas as an Electrical Insulating Material. ASTM D (1997) Standard Test Methods for Silicone Fluids Used for Electrical Insulation. ASTM D (2006) Standard Specification for Mineral Insulating Oil Used in Electrical Apparatus. ASTM D Standard Guide for High Fire-Point Mineral Electrical Insulating Oils. 92

67 Oil Preservation Systems Factors (Design or Specification) Load Variations Temperature Variations Leaks Maintenance Testing 93

68 Oil Preservation Systems Sealed Tank Simplest Shipped from the factory with a blanket of Nitrogen As the transformers operates, nitrogen is expelled during overpressure(high load and/or high ambient) and air is introduced during vacuum conditions(light load and cold ambient). 94

69 Oil Preservation Systems Sealed Tank system design Requires a gas space for expansion of the mineral oil. Expansion space is usually achieved by increasing the tank height. Increases the tank height/ shipping height Designed for a max operating pressure of 8 psi (regulator) with a 125% safety factor(10 PSI) Supplied with a pressure relief device as overpressure protection. Always Nitrogen - Not Air 95

70 Oil Preservation Systems Sealed Tank with Inert Gas Oil Preservation System (Nitrogen) Requires a gas space for expansion of the mineral oil. Transformer is supplied with a cylinder of nitrogen and a pressure regulator to automatically maintain a positive pressure of nitrogen in the gas space. Normally regulates to +5, -0.5 psi Cylinders are supplied with a low pressure alarm to indicate imminent loss of N 2 supply. 96

71 Oil Preservation Systems Conservator Oil Preservation System (COPS) Expansion space is provided by the conservator Requires a bladder to preclude entrance of Oxygen Supplied with a Dehydrating Breather to eliminate Moisture Requires bleeding off all trapped gas Usually supplied with a relay to accumulate gasses (Bucholz or a Gas Accumulation Relay) for fault detection Can be used to reduce shipping height, conservator is removed. EHV transformers ( 345 kv) 97

72 IEEE Standard Impedance IEEE Std C The percent impedance voltage at the self-cooled rating as measured on the rated voltage connection shall be as listed in Table 3 if the user does not specify another value. For cases not covered in Table 3, the percent impedance voltage value shall be agreed between user and manufacturer, and the user should perform a system study to determine the proper value of impedance. Table 3 Percent impedance at self-cooled (ONAN) rating High Voltage BIL Without LTC With LTC

73 IEEE Std C IEEE Standard Impedance Autotransformers For autotransformers, the percent impedance voltage shall be as specified by the user, or it should be the lower of the value from Table 3 and the value obtained according to the following equation: Autotransformer impedance voltage = (Value from Table 3) (Autotransformer co-ratio) 1.5 where Autotransformer co-ratio = (High- Voltage Low-Voltage)/(High-Voltage) This impedance voltage is the autotransformer impedance and not the equivalent autotransformer impedance. 99

74 IEEE Std. C Abstract: The performance of transformers in the presence of oscillatory transients is addressed in this guide. Oscillatory transients are typically produced by the interaction of the switching device, transformer, load, and system. This guide describes operating conditions that may produce oscillatory switching transient voltages damaging to the transformer insulation system. It discusses the electrical characteristics of the source, switching device, transformer, load and the nature of their transient interaction. It discusses several mitigation methods. Two generic examples are included. This guide focuses on mechanical switching devices and does not address semiconductor switching devices. IEEE Guide to Describe the Occurrence and Mitigation of Switching Transients Induced by Transformers, Switching Device, and System Interaction 100

75 Electrical Design Process Hot-spot temperature calculation C , a) Direct measurement during a thermal test in accordance with IEEE Std C A sufficient number of direct reading sensors should be used at expected locations of the maximum temperature rise as indicated by prior testing or loss and heat transfer calculations. b) Direct measurement on an exact duplicate transformer design per a). c) Calculations of the temperatures throughout each active winding and all leads. The calculation method shall be based on fundamental loss and heat transfer principles and substantiated by tests on production or prototype transformers or windings. The maximum (hottest-spot) winding temperature rise above ambient temperature shall be included in the test report with the other temperature rise data. A note shall indicate which of the above methods was used to determine the value. 101

76 Electrical Design Process Hot-spot temperature calculation an example 28 kv, kv 28 kv, kv 28 kv, kv 28 kv, kv 102

77 Electrical Design Process Hot-spot temperature calculation results Hot-Spot Temperature ( C Rise over kv Hottest Inner Winding Winding Winding Winding Outer Winding The inner winding and the Winding 3 had to be redesigned to lower the hot-spot temperature rise below 80 C 103