RURAL ELECTRIFICATION AGENCY
DISTRIBUTION TRANSFORMER MANUFACTURING PROCESS MANUAL
Drafted by:
Approved By:
PE –Fred Asiimwe
Eng. Turyagyenda John
PE- Onzia Joseph
Manager Project Development & Management
SPE-Anthony Wamabuya PPE-Deborah Nantume Date: September 2015
Date: November 2015
Table of Contents PART 1: PROCESS MANUAL............................................................................................... 5 1.0 Scope .................................................................................................................................... 5 2.0 Application ......................................................................................................................... 5 3.0 Certification ....................................................................................................................... 5 4.0 Documentation ................................................................................................................... 5 5.0 Management Commitment ............................................................................................. 6 6.0 Resource Management..................................................................................................... 6 7.0 Operations Control ........................................................................................................... 7 8.0 Product Realization .......................................................................................................... 7 8.1 8.2 8.3 8.3.1 8.3.2 8.3.3 8.3.4 8.3.5 8.3.6 8.3.7 8.4 8.5
Transformer Design ................................................................................................................... 7 Material Acquisition .................................................................................................................. 7 Production .................................................................................................................................... 8 Core Construction ................................................................................................................... 9 Primary & Secondary Winding Assembly ........................................................................ 9 Core & Winding Assembly ................................................................................................ 10 Core & Winding Assembly Drying .................................................................................. 10 Core & Winding Assembly Tanking ............................................................................... 10 Oil Filling................................................................................................................................ 11 Tank Fabrication .................................................................................................................. 11 Testing ........................................................................................................................................ 11 Product Handling & Packing ............................................................................................... 12
PART 2: MATERIAL MANUAL ........................................................................................ 13 1.0 Transformer Core .......................................................................................................... 13 2.0 Transformer Winding ................................................................................................... 15 2.1 2.2 2.3 2.4
Enameled copper winding wire ............................................................................................ 15 Enameled aluminum winding wire ..................................................................................... 18 Copper strip or foil.................................................................................................................. 20 Aluminum strip or foil ........................................................................................................... 21
3.0 Transformer Oil ............................................................................................................. 22 4.0 Insulating Paper ............................................................................................................. 23 4.1 4.2 4.3
Corrugated Boards.................................................................................................................. 23 Transformer Board ................................................................................................................. 24 Diamond Dotted Paper ........................................................................................................... 24
5.0 Offload Tap Changer .................................................................................................... 25 6.0 Pressure Relief Valve .................................................................................................... 26 7.0 Transformer Tank ......................................................................................................... 26 8.0 Radiator ........................................................................................................................... 27 PART 3: TESTING PROTOCOLS..................................................................................... 28
1.0 Introduction .................................................................................................................... 28 2.0 Transformer Tests ......................................................................................................... 28 2.1 2.2
Transformer Routine Tests ................................................................................................... 28 Transformer Type Tests ........................................................................................................ 28
3.0 TRANSFORMER TEST PROTOCOLS ................................................................. 29 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15
Transformer Insulation Resistance Test ............................................................................ 29 Transformer Vector Group Test ......................................................................................... 29 Transformer Voltage Ratio Test .......................................................................................... 31 Transformer DC Winding Resistance Test ....................................................................... 33 Transformer Oil Dielectric Test ........................................................................................... 35 Transformer Separate Source Voltage Withstand Test ................................................. 35 Transformer Induced Over Voltage Test At High Frequency ................................... 38 Transformer No Load Test (Core Loss- Hysteresis Loss and Eddy current loss .... 40 Transformer Full Load Loss Test (Copper Losses) ........................................................ 42 Zero Sequence Impedance Test ......................................................................................... 44 Sound Level Test (Type Test). ............................................................................................ 44 Temperature Rise Test (Type Test) .................................................................................. 46 Measurement Of Electrical Break Through Voltage Of Copper Wire .................... 48 Dry Power Frequency Voltage Withstand Test ............................................................. 50 Transformer Pressure Testing ........................................................................................... 50
4.0 Post Shipping Inspection .............................................................................................. 53 APPENDICES .......................................................................................................................... 54 Appendix A: Plant & Process Checklist ....................................................................................... 54 Appendix B: FAT Checklist ............................................................................................................ 61
PART 1: PROCESS MANUAL
1.0
Scope
This process manual describes the minimal requirement for any transformer manufacturing plant intending to supply transformers to REA. The manual is designed to assist REA deal with manufacturing plants that have established and certified management systems addressing all aspects of Health, Safety, Environment and Quality (HSEQ) either independently or jointly through an Integrated Management System (IMS). The manual defines the minimal processes required to ensure that the transformer manufacturing plant adequately meets the customer requirements and applicable statutory and regulatory requirements and aims to enhance customer satisfaction through effective application of the system, including processes for continual improvement and assurance of conformity to customer and regulatory requirements. It is prepared based on the criteria governing ISO 9001:2008, ISO 14001:2004 and OHSAS 18001:2007 International Standards.
2.0
Application
The process and system describe in this manual shall be applicable to all functional area of the transformer manufacturing plant
3.0
Certification
The transformer manufacturing plant systems and processes shall be certified in accordance with ISO 9001:2008, ISO 14001:2004 and OHSAS 18001:2007 international standards as a minimum requirement. Relevant certification certificates shall be submitted at tender stage. Audit: (Valid Certification Certificates)
4.0
Documentation
The transformer manufacturing plant shall have all the systems and processes documented for effective planning, operation and control. Every step involved in the
process of manufacturing transformers for REA shall be document and this documentation shall be kept for the specified period as required by the standard and should be presented to REA when called upon. These shall include but not limited to; HSEQ Policies and Manuals, Process Manual, System Procedures, Quality Plans, Manufacturing Procedures, Inspection Instructions, Test Methods, Process Checklists and Forms. A document control system shall be maintained, detailing procedures for changes, authorization, revisions, approvals, indexing and achieve amongst other. Audit: (Availability of above documents & a Document Control System)
5.0
Management Commitment
Management of the transformer manufacturing plant shall demonstrate their commitment of promoting all aspects of HSEQ in the manufacturing processes of REA transformer. This shall be done through a written and signed off HSEQ Policy indicating SMART objectives, actions, responsible persons and support for ensuing adherence to health, safety, environment, quality, statutory and regulatory requirements. Audit: (Availability of HSEQ Policy Statement, Procedure for Environmental Aspect Evaluation, Hazard Identification, Risk Assessment, Legal requirement identification)
6.0
Resource Management
The quality of the product not only depends on the materials but also on skills, workmanship and infrastructure involved in the product realization process. Management shall establish a resource management system with the aim of planning and controlling resources and determine the required resources to implement and maintain the management systems put in place to ensure HSEQ objectives are achieved. The following shall be in place: Staff Competency Analysis Records, Job Descriptions, Training Records, Sufficient Physical Infrastructure and Machinery. Audit: (Staff Competency Analysis Records, Job Descriptions, Training Records, Sufficient physical Infrastructure and Machinery)
7.0
Operations Control
The manufacturing operations shall be standardized by activities that are performed by qualified resources under defined conditions. The process conditions shall be specified in standards, Instructions, Work Orders, Manuals, Procedures, Protocols and contractual relations with suppliers and customers. The plant shall have systems in place for safe guarding the environmental, promoting quality and health and safety. (HSEQ) Audit: (Availability of Hazards Register, Environmental Aspect Register, Process Manuals, Work Instructions, Inspection Checklists, Test Certificates, Calibration Certificates, Safety manuals and Risk Register amongst others)
8.0
Product Realization
8.1
Transformer Design
The Transformer manufacturing plant shall have processes in place to aid transformer designing. Client’s specifications and the relevant IEC standards shall be the main input to the design process, any necessary requirement not specified but necessary for fitness purpose shall be identified and communicated in writing to the client for clarification at design stage. A system should be in place at design stage to establish and record clients’ technical requirements, statutory and regulatory requirements, clarifications, delivery, quality and maintenance requirements. Product information, outline drawing, design report and fully filled and signed Guaranteed technical parameters shall be submitted Audit: (Availability of REA Specification, Procedure for identification & review of customer requirements, Design Action Plan, Design review checklist) 8.2
Material Acquisition
The transformer manufacturing plant shall have an established purchasing process, which guides suppliers.
Based on the design output, materials specification customized for REA transformers shall be development for the supplier. This shall address technical requirements for; copper winding wires, core materials, bushings, tank, insulating oil, Surge arrestors, arcing horns and Insulating paper. The specifications shall also address the appropriate quality, safety and environmental management requirement. All purchased and outsourced service shall be inspected, verified and tested at receipt according to a documented procedure. Both parties shall sign acceptance test reports and copies shall be submitted to the client for verification. All materials purchased for REA transformers shall be used and where production is not yet started, such materials shall be quarantined. Audit (Availability of materials specifications and Material acceptance test reports) 8.3
Production
The production process shall be carried out under controlled conditions, the information that describes the characteristics of the product shall be provided to the responsible staff in form of detailed drawings, charts, instructions, etc. These shall be made available at point of use. A production quality plan shall be established and this shall highlight process specific quality checks, equipment required, resources requirement, suitable monitoring and measuring devices. At every stage in the transformer manufacturing, quality & technical compliance checks shall be performed by a qualified engineer before part is progressed to the next stage in the production line There shall be adequate equipment required for each production activity and these shall be properly maintained Traceability shall be established and maintained in the production process right from materials acquisition, part assembly and product testing. Information regarding; material supplier, staff name responsible for each activity, approvals at each stage, test done and testing personnel among other shall be recorded using a transformer assembly form/card. In the production process, items shall be identified by either labels, rating plates, stickers, hang-on cards, hard stamping or marking with ink to indicate rating, drawing number,
etc. wherever standards are available for identification purposes such standards shall be followed. 8.3.1
Core Construction
The core shall be of high grade cold rolled grain oriented silicon sheet steel and securely clamped. The core material shall be as per REA material specification and the materials test report shall be submitted upon request. The transformer core shall be of three limbs, step lap stacked at joints to minimize losses and sound levels Core sheets should be cut using a semi –auto or automated cutter. In a semi-auto arrangements, the controls shall be the one manually operated but the cutting shall be of automated. Samples of core sheet shall be measured for correct dimensions and recorded on the transformer inspection board. The core flux density shall be as per the specifications and required loss values
8.3.2 Primary & Secondary Winding Assembly The primary and secondary windings shall be constructed from high conductivity E.C grade copper. All turns of the windings shall be adequately supported to prevent movement The High voltage winding shall be of layered winding and the Low voltage winding shall be of either layered or foil winding using copper sheets The Primary and secondary winding shall be wound using appropriate winding machines with turns counter. The name of the staff winding a particular transformer shall be noted on the transformer inspection board together with the personnel who checked and approved. An appropriate insulating barrier shall separate the primary and secondary windings; Inter winding insulation shall be of Diamond Dotted Paper with cooling ducts
8.3.3 Core & Winding Assembly The windings shall be inserted on the core leg using appropriate tools (Crane, lifting bracket with a belt), Insulation strips shall be carefully inserted between core and windings Insulation resistance between core and LV coil shall be checked using an insulation resistance meter and result recorded on the transformer assembly inspection cards. Insulation boards shall be placed between the top of the coil and the yoke and no gap shall be left between strips of the core leg to complete the core. The yoke shall be clamped with wooden frame and earthing strips shall be inserted into the core closer to the LV side-lifting traverse Stay rods shall be inserted and earthing strip inserted on the stay rod, the upper wooden frame must be tightened & the frame foot shall be fixed to stay rods. Correct lifting traverses shall be fixed to stay rods and tightened properly, LV copper bus bars shall be fixed using appropriate tool & LV flexible leads shall be fixed properly using correct bolts with spring washers. Insulating paper tubes shall be inserted to tapping leads & the timber used must we properly impregnated for 24hrs 8.3.4 Core & Winding Assembly Drying The core and winding assembly shall be dried in an oven to drive away all moisture in optimum time (minimum of 24hrs) Minimum time shall be taken between drying, tanking and filling with oil (maximum 30 minutes) to avoid re-absorption of moisture in the active parts. After drying, tank, cover plate with accessories and oil should be ready. 8.3.5 Core & Winding Assembly Tanking Cover plate, Rating, surge arrestors, bushing and bushing accessories shall be prepared and appropriate tools shall be used. Transformer tank shall be kept clean all the time & all required components to the cover shall be fixed using appropriate tools. Appropriate clearances and seal shall be insured using wooden blocks and silicon sealant & cork gaskets. The transformers shall be hermetically sealed.
The cover plate with all accessories shall be first mounted to the core & winding assembly before tanking, all connections must be checked for strength. 8.3.6 Oil Filling Transformer oil shall be filled in a vacuum chamber to prevent air bubbles 8.3.7 Tank Fabrication The tank fabrication process shall be parallel to active part assembly. The tanks for REA transformers shall be of fin type with a base, radiator, flange and cover plate. The transformer tank and tank cover shall be made of mild steel, hot dip galvanized and then powder coated as per the specification The welding shall be done using an appropriate method suitable not to damage the materials. Preferably Arc & Metal Inactive Gas (MIG) welding shall be used accordingly Appropriate machines preferably semi-auto or automated shall perform all the machining processes of shearing, bending, punching & drilling The materials thickness for the base, cover plate, flange and radiator shall be as per REA specification The finished tank and cover plate shall be properly cleaned before dipping and painting processes. Audit (Availability of product information at point of use, production quality plan, adequate equipment, traceability system in-place, Approved method and procedures, Transformer assembly inspection record, tank fabrication inspection record) 8.4
Testing
Test protocols according to IEC standards shall be established and the required equipment put in place in a testing laboratory. All transformers shall be inspected and tested as per IEC standards & REA specifications New design shall be type tested by an internationally recognized testing laboratory and type test reports shall be submitted to the client Audit: (Availability of test protocols, Type test and routine test reports, Calibration Reports)
8.5
Product Handling & Packing
All products shall be handled properly to prevent damage or deterioration throughout the production process. Special handling tool should be in place for example cranes and forklifts, and these should be inspected regularly. Secure storage areas shall be provided to prevent transformers from getting damaged or deteriorated before dispatch and all finished transformers shall be suitably marked for clear identification. Inspection, packing and delivery of finished transformers shall be done according to REA’s specification Audit: (Availability of proper handling tools, secure storage space, Procedure for handling, Packaging, Storage & Dispatch)
PART 2: MATERIAL MANUAL
1.0
Transformer Core
The material for production of the transformer core shall be cold rolled grain orientated silicon steel sheet (CRGO) with high permeability, low core loss, low magnetostriction, high inter-laminar resistance and high lamination factor manufactured in accordance with BS EN 10107:2005, JIS C 2553:2000 standards or any other national and international standard that can offer equal or higher but not less quality the standards mentioned above. The core shall be of three limbs stacked core type and shall be securely clamped. The material shall be free from holes, inclusions, cracks and other imperfections that would make it useless for manufacture of transformer cores. The material shall also be free of flakes, particles, or other forms of separable electrically conductive materials. The maximum thickness of CRGO laminations shall be 0.23mm. Thickness tolerance shall not be more than 3% and edge burr height when cut shall be within permissible limits (for production 90% below 0.010mm and 100% below 0.02mm). The flatness (waviness) must not exceed 15mm/1000mm. the edge deviation (Camber) must not exceed 0.3mm over measuring length of 1.5m. The maximum flux density shall not exceed 1.6 Testa. An inorganic coating shall be applied to both sides of the steel sheets and it shall have the following properties: 1. Shall offer high inter-laminar properties 2. Shall be thin and bonded to the steel surface so that it never peels off even when subjected to shearing or bending. 3. Shall not be affected by mineral transformer oil, machine oil owing to its anti-rust property The minimum physical, mechanical and magnetic properties shall be as listed in table below.
Physical, mechanical and magnetic properties of CRGO Properties
Unit
Value
Physical Properties Si content
Approximately 3%
Density
Kg/dm3
7.65
Lamination thickness
mm
0.23
Edge Burr height
mm
0.01 – 0.02
Flatness (Waviness)
mm
Shall not exceed 15mm over 1000mm length
Edge deviation (Camber)
mm
Shall not exceed 0.3mm over 1.5mm length
Mechanical Properties Yield strength Rp 0.2 MPa
350
RD (Rolling Direction) 90 degrees to RD Ultimate tensile strength
360 MPa
350
MPa
400
RD 90 degrees to RD Elongation RD
10%
90 degree to RD
30%
Hardness, HV5
180
Equivalent Rockwell B
76
Modulus of elasticity RD
MPa
120×103
55 degrees to RD
MPa
260×103
90 degrees to RD
MPa
140×103
Curie temperature
0
C
746
Electrical Properties Resistivity
µ Ωm
0.48
W/kg
0.69 – 1.11
W/kg
1.17 – 1.57
Magnetic Properties Specific core loss at 50Hz for 1.5T Specific core loss at 50Hz
for 1.7T Saturation induction
2.0
T
2.03
Transformer Winding
Shall be made of Enameled copper winding wire and copper strips. However, aluminum may be used if expressly asked for in REA specifications. 2.1
Enameled copper winding wire
The enameled copper wire used shall conform to the following standards and or the latest editions thereof:
IEC 60317-0-1:2013
IEC 60317-8:2010 Class 180 (Grade 2)
IEC 60264-3:1999
IEC 60851:1996
Items conforming to other national or international standards, which give equal or higher, but not less quality requirements can be accepted. Enameled round copper winding wire shall be of class 180, with a sole coating based on polyesterimide resin. The film coating shall be essentially smooth and continuous, free from streaks, blister and foreign material when examined with normal vision as wound on the original spool. The copper for electrical purposes E-Cu 57 according to DIN 40500 teil 4 with minimum copper content of 99.90% shall be used. The overall diameter, electrical characteristics and insulating properties of the enamel covering shall be in accordance with the standards specified. In addition, copper wire shall withstand electrical break through voltage of at least 450V in a salt solution (Water + 5% NaCl, weight to weight). The maximum resistance value shall not be greater than the calculated with resistivity of 1/58 Ωmm2/m. the value shall be calculated for the minimum tolerated cross-sectional area of the conductor. The maximum current density shall not exceed 2.5 – 3.0 A/mm2. The nominal diameter of copper, its tolerances and the minimum values for elongation at fracture shall be as indicated in table below.
Nominal diameter and minimum elongation at fracture of enameled for primary winding Nominal
Minimum
Conductor
Minimum
Maximum
diamete
elongation (% of
tolerance (-,+)
increase due to
overall diameter
r (mm)
nominal diameter)
µm
the insulation
(mm)
(µm) Grade
Grade 2
1
Grade
Grade 2
1
0.250
22
4
17
32
0.281
0.297
0.280
22
4
18
33
0.312
0.329
0.315
23
4
19
35
0.349
0.367
0.355
23
4
20
38
0.392
0.411
0.400
24
5
21
40
0.439
0.459
0.450
25
5
22
42
0.491
0.513
0.500
25
5
24
45
0.544
0.566
0.560
26
6
25
47
0.606
0.630
0.630
27
6
27
50
0.679
0.704
0.710
28
7
28
53
0.762
0.789
0.800
28
8
30
56
0.855
0.884
0.900
29
9
32
60
0.959
0.989
1.000
30
10
34
63
1.062
1.094
1.120
30
11
34
65
1.184
1.217
1.250
31
13
35
67
1.316
1.349
1.400
32
14
36
69
1.468
1.502
1.600
32
16
38
71
1.670
1.706
1.800
32
18
39
73
1.872
1.909
2.000
33
20
40
75
2.074
2.112
2.240
33
22
41
77
2.316
2.355
2.500
33
25
42
79
2.578
2.618
2.800
34
28
43
81
2.880
2.922
3.150
34
32
45
84
3.233
3.276
3.550
35
36
46
86
3.635
3.679
4.000
35
40
47
89
4.088
4.133
4.500
36
45
49
92
4.591
4.637
5.000
36
50
50
94
5.093
5.141
Springiness of enameled copper wire Nominal diameter
Mandrel
(mm)
Diameter (mm)
Tension (N)
Minimum springback degrees Grade 1
Grade 2
0.250
12.5
2
49
56
0.280
12.5
2
47
53
0.315
19
4
50
55
0.355
19
4
48
53
0.400
19
4
45
50
0.450
25
8
44
48
0.500
25
8
43
47
0.560
25
8
41
44
0.630
37.5
12
46
50
0.710
37.5
12
44
47
0.800
37.5
12
41
43
0.900
50
15
45
48
1.000
50
15
42
45
1.120
50
15
39
41
1.250
50
15
35
37
1.400
50
15
32
34
1.600
50
15
28
30
For nominal conductor diameter above 1.600mm, the wire shall not exceed the maximum spring back of 5 degrees. Breakdown Voltage of enameled copper wire
Nominal
Minimum breakdown voltage (r.m.s value) V
diameter (mm) Grade 1
Grade 2
Room
Elevated
Room
Elevated temperature
temperature
temperature
temperature
0.250
2100
1600
3900
2900
0.280
2200
1700
4000
3000
0.315
2200
1700
4100
3100
0.355
2300
1700
4300
3200
0.400
2300
1700
4400
3300
0.450
2300
1700
4400
3300
0.500
2400
1800
4600
3500
0.560
2500
1900
4600
3500
0.630
2600
2000
4800
3600
0.710
2600
2000
4800
3600
0.800
2600
2000
4900
3700
0.900
2700
2000
5000
3800
1.000 up to and
2700
2000
5000
3800
1300
1000
2500
1900
including 2.500 0ver 2.500
2.2
Enameled aluminum winding wire
The enameled aluminum wire used shall conform to the following standards and or the latest editions thereof:
IEC 60317-0-3: 2008 Grade 1 Class 180
DIN 40501
IEC 60851
IEC 60264-3: 1999
BS 1489: 1972
Items conforming to any other international or national standards, which are equal to higher but not less, rigid than the specifications stipulated may be offered. Aluminum for electrical purposes E-Al F7 according to DIN 40501 with a minimum aluminum content of 99.5% shall be used. Nominal Diameter and minimum breakdown voltage Nominal
Conductor
Minimum
Maximum
Minimum
diameter
tolerance (-
increase due to
overall diameter
breakdown
(mm)
,+)
the insulation
(mm)
voltage at room
µm
(µm) Grade 1
temperature (V)
Grade 2
Grade 1
Grade 2 Grade 1
Grade 2
0.250
4
17
32
0.281
0.297
2100
3900
0.280
4
18
33
0.312
0.329
2200
4000
0.315
4
19
35
0.349
0.367
2200
4100
0.355
4
20
38
0.392
0.411
2300
4300
0.400
5
21
40
0.439
0.459
2300
4400
0.450
5
22
42
0.491
0.513
2300
4400
0.500
5
24
45
0.544
0.566
2400
4600
0.560
6
25
47
0.606
0.630
2500
4600
0.630
6
27
50
0.679
0.704
2600
4800
0.710
7
28
53
0.762
0.789
2600
4800
0.800
8
30
56
0.855
0.884
2600
4900
0.900
9
32
60
0.959
0.989
2700
5000
1.000
10
34
63
1.062
1.094
2700
5000
1.120
11
34
65
1.184
1.217
2700
5000
1.250
13
35
67
1.316
1.349
2700
5000
1.400
14
36
69
1.468
1.502
2700
5000
1.600
16
38
71
1.670
1.706
2700
5000
1.800
18
39
73
1.872
1.909
2700
5000
2.000
20
40
75
2.074
2.112
2700
5000
2.240
22
41
77
2.316
2.355
2700
5000
2.500
25
42
79
2.578
2.618
2700
5000
2.800
28
43
81
2.880
2.922
1300
2500
3.150
32
45
84
3.233
3.276
1300
2500
3.550
36
46
86
3.635
3.679
1300
2500
4.000
40
47
89
4.088
4.133
1300
2500
4.500
45
49
92
4.591
4.637
1300
2500
5.000
50
50
94
5.093
5.141
1300
2500
2.3
Copper strip or foil
Copper strip (rectangular) and copper foil shall be used for low voltage winding. The copper strip used shall comply with or latest editions of EN 1652 or any other standard that offers a higher performance. The foil or strip shall be free of short, sharp deformations and edge wrappings. The foil or strip shall also be free of holes, bubbles, dragon’s teeth, bumps, edge cracks, notches and other deformations which may be defined as manufacturing defects. The foil or strip surface shall be shiny and free of grease and other impurities. Grease test according to DIN 53364: Testing of plastic films, which can also be applied for copper foils or strips can be conducted if required. The edges shall be without any blurr. In accordance with DIN 40500 Teil 1, material E-Cu57 F20. The minimum copper content shall be 99.90%. Current density shall not exceed 3.5A/mm2. Thickness and width of the copper strip shall be within the range of 0.1 – 2.5mm and 350 – 1250mm respectively. Thickness and width tolerances shall be kept within reasonable limits. Physical and mechanical properties Property
Unit
Type
Density
Kg/dm3
8.90
Tensile strength, Rm
N/mm2
Minimum 200
Proof stress, RP0,2
N/mm2
Minimum 120
Elongation, A5 Thickness (T) = 0.1 … 1mm
Minimum 38%
T = (1) … 10mm
Minimum 40%
Hardness HV
40 … 65
HB
45 … 70
For cold pressure welding 50 … 56
hardness, HV Thermal conductivity
W/(K.m)
398
Resistivity
µΩm
Maximum 0.01754
2.4
Aluminum strip or foil
The items used shall be in accordance with standards specified below or latest editions and amendments thereof;
DIN 1783
DIN 1784
DIN 40501
DIN 53364
BS EN 13599: 2002
Items conforming to any other international or national standards, which are equal to or higher but not less rigid, the standards and specifications stipulated may be offered. The foil or strip shall be free of short, sharp deformations and edge wrappings. The foil or strip shall also be free of holes, bubbles, dragon’s teeth, bumps, edge cracks, notches and other deformations, which may be defined as manufacturing defects. The foil or strip surface shall be shiny and free of grease and other impurities. Grease test according to DIN 53364: Testing of plastic films, which can also be applied for copper foils or strips can be conducted if required. The edges shall be without any blurr. Aluminum for electrical purposes E-Al F7 according to DIN 40501 teil 4 with a minimum aluminum content of 99.5% shall be used.
Physical and mechanical properties Property
Unit
Type
Density
Kg/dm3
2.70
Tensile strength, Rm
N/mm2
65 … 95
Proof stress, RP0,2
N/mm2
Max. 55
Elongation, A5
Minimum 40%
Hardness HV
Approximately 25
HB
Approximately 20
Thermal conductivity
W/(K.m)
203
Resistivity
µΩm
Maximum 0.0282
3.0
Transformer Oil
Transformer oil shall be used dissipate heat generated in the windings and to also provide electrical insulation. The raw material for production of transformer oil shall be low viscosity transformer oil base stock (TOBS) obtained by fractional distillation and subsequent treatment of crude petroleum which is further refined by acid treatment process to yield transformer oil. Any other transformer oil shall be accepted as long as it’s demonstrated that such oil offers superior performance. The oil shall be produced in accordance with standards specified below or later editions and or amendments thereof;
BS 148: 2009 Class 1
IEC 60296: 2003
Any other national or international standard that offers higher but not less quality requirements can be used with prior approval from REA. The transformer oil shall have the minimum characteristics of given in table below Minimum characteristics of transformer oil Test
Test Method
Value
Relative density
ISO 3675:1998
0.871
Viscosity 40 deg. C.Cs
ISO 3014:1993
12.0 (max)
Viscosity 20 deg. C.Cs
ISO 3014:1993
31.0
Viscosity 0 deg. C.Cs
ISO 3014:1993
Viscosity -15 deg. C.Cs
ISO 3014:1993
350
Viscosity -30 deg. C.Cs
ISO 3014:1993
1800 (max)
Flash point deg. C
ISO 2719: 2002
154
Pour point deg. C
ISO 3016: 1994
-40
Neutralization value mg.KOH/g
IEC 60296: 2003
< 0.03
Corrosive sulphur
BS 2000-315:1998
Non corrosive
Water content mg/kg
IEC 60814: 1997
1.5
Breakdown Voltage kV
IEC 60156: 1995
70
Resistively Ωm 20 deg. C
IEC 60247: 2004
20
Dielectric dissipation factor 90
IEC 60247: 2004
0.001
Gassing tendency mm/min
IEC 60628: 1985
-1
Antioxidant additive
IEC 60666: 1979
None
Acidity mg.KOH/g
IEC 61125: 1992
0.4
Sludge value %
IEC 61125: 1992
0.1
PCB
IEC 61619: 1997
None
deg. C
Oxidation Test:
4.0
Insulating Paper
Insulating paper shall be used to offer inter turn winding insulation as well as insulation between MV and LV windings. 4.1
Corrugated Boards
Corrugated boards shall be used provide insulation between MV and LV windings. The corrugated board shall be manufactured in accordance with;
IEC 60641-1: 2007
DIN EN 60641-3-1: 2009
The board shall be of Class A insulation in transformer oil, shall not affect the properties of the transformer oil and shall have a minimum dielectric strength of 60 kV/mm in oil. Cutting edge of the corrugated board must be free from burrs, any deformations and thickness shall not be increased. The designed thickness and curvature of the corrugation shall ensure adequate insulation and circulation of transformer oil. 4.2
Transformer Board
The transformer board shall be used to provide insulation between core and LV windings, between MV phase to phase winding and between the end of windings of every phase and the core. The board shall be manufactured in accordance with standards specified below or latest editions and or amendments thereof; IEC 60641-1: 2007 The transformer board shall be of class A insulation in transformer oil, shall not affect the properties of the transformer oil and shall have a minimum dielectric strength of 60kV/mm in oil. 4.3
Diamond Dotted Paper
Diamond dotted paper shall be used to provide inter-turn winding insulation for both primary and secondary winding. It will be manufactured according to the following standards;
IEC 60641-1:2007
DIN EN 60641-3-1:2009
The diamond dotted paper shall be diamond patterned epoxy papers and have shall the following minimum properties;
Paper shall contain both sulphate wood pulp and cotton in a 50/50 mixture to impart a combination of both favorable stiff and tensile properties.
The resin shall be on both sides of the paper and shall result in partial adhesion of the electrical conductors to the layer insulation at a temperature between 100 0C – 130 0C.
Approximately 36% of the total area on each side should be printed with epoxy resin of 9.5×9.5mm2
The thickness of the partial coating of resin shall be 0.01mm on each side.
The epoxy resin must not affect the properties of mineral oil used in the transformer.
Single layer diamond dotted paper shall generally have a nominal thickness of 0.13mm and 0.25mm.
When the insulation is specified as double layer diamond dotted paper (DDP), it shall have two layers of DDP glued under dry conditions. Double layer DDP shall generally have a nominal thickness of 0.15mm, comprising of two 0.075mm thick insulation paper.
5.0
Offload Tap Changer
Offload tap changer shall be manufactured in accordance with the following standards;
IEC 60893-1: 2004
EN 12420: 1999
EN 13599: 2002
The tap selector shall be suitable for off load operation and immersing in transformer oil and to be used in hermetically sealed transformers. These shall be operated generally at nominal voltages of 36kV and 12kV with different current ratings. The number of tap positions shall be as per REA specifications. The materials to be used in different parts of the tap selector are shown in table below Materials for different parts of tap selector Part
Material
Steel Parts
Stainless steel
Polyamide Parts
Nylon 66, Strong against UV light
Aluminum Parts
GAlSi12Cu,
Protected
from
anodic
oxidation Brass Parts
CuZn40Pb2 Ms60F34
Copper Parts
E-Cu F25
Insulator Parts
Paper phenol plastic resin based laminates
Any changes to material shall be given prior approval.
6.0
Pressure Relief Valve
Pressure relief valve shall be manufactured in accordance with IEEE Std C57.12.22-1993 or any other national and international standard that offers equal or higher but not less quality requirements. The pressure valve shall operate at 0.35 bars and shall reseal at the same pressure.
7.0
Transformer Tank
Mild steel shall be used to manufacture transformer lifting traverse, lifting hook, lifting lug, and tank, base, top cover and the flange. This shall be in the form of;
Mild steel sheets
Mild steel angles
Mild steel channels
Mild steel flat bars
Mild steel rods
Items supplied shall be in accordance with the standards specified below or later editions and or amendments thereof
BS EN 10029: 1991
BS 7668: 2004
BS EN 10025-1:2004
BS EN 10025-3:2004
BS EN 10025-4:2004
BS EN 10210-1:2006
Items conforming to any other international or national standards, which are equal to or higher but not less, rigid than the standards and specifications stipulated may be offered. The mild steel components shall be free from corrosion, oil/grease and burrs. The minimum thickness of the mild steel for up to 400kVA transformer shall be between 4mm to 6mm and for 500 – 600kVA shall be 6mm to 10mm.
8.0
Radiator
The radiator shall be used convectional cooling of the transformer so that designed temperature rise in the inside transformer is with desired limits. The items used shall be formed out of steel in compliance with standards specified below or later editions and or amendments thereof;
DIN EN 10131: 1992
DIN 1623: 2009
The (items formed out of) steel conforming to any other international or national standards which are equal to or higher but not less rigid than the standards and specification stipulated may be offered. All radiator surfaces should be free from oil and the minimum thickness shall be 0.2mm.
PART 3: TESTING PROTOCOLS
1.0
Introduction
The Client in accordance with the relevant IEC and ISO standards shall inspect the manufacturing plant, its process and products. The tests on the products shall include:
2.0
Transformer Tests
2.1
Transformer Routine Tests 1. Transformer insulation resistance test 2. Vector group test 3. Voltage ratio test 4. DC resistance test/winding resistance test 5. Oil dielectric strength test 6. Separate source voltage withstand test 7. Induced overvoltage withstand test at high frequency. 8. No load test 9. Full load test/ short circuit test
2.2
Transformer Type Tests 1. Impulse voltage withstand test (Dry power frequency voltage withstand test) 2. Electrical break through voltage of copper wire 3. Transformer pressure testing 4. Sound level test
The following information about the transformer test equipment shall be provided by all transformer manufacturers as it may be required from time to time to ensure acquisition of result with minimal errors; Equipment name, Manufacturer, Date of purchase and Last date of calibration
3.0
TRANSFORMER TEST PROTOCOLS
3.1
Transformer Insulation Resistance Test
Purpose: This test is intended to assess the condition of insulation of all insulated parts of a transformer. Apparatus: Megger Insulation Tester Preparation of Sample Isolate the transformer. Clean all bushings with a clean piece of cloth. Procedure
Set a scale indicator to the discharge position before each test.
Connect the probes of the tester (P1 & P2) to the points between which insulation is measured (e.g. In the case of H/E, connect probes to the winding terminal and Earth).
Select the proper scale:
Select 1000V scale for winding voltages below 1.0KV.
Select 5000V scale for winding voltages above 2.5kV.
Acceptance Criteria Measurements taken between
Minimum acceptable value
HV & LV
600 Mega Ohms
HV & E
600 Mega Ohms
LV & E
600 Mega Ohms
Safety
3.2
Make sure the test leads are not damaged
Do not touch the leads while the meter is switched ON
Always follow general safety instruction of the area Transformer Vector Group Test
Purpose
To confirm the vector group is provided. Test should be performed as per IEC – 60076 test standards. Apparatus
Transformer Ratio meter (PWR 3A)
Manual of Transformer Ratio Meter.
Preparation of samples
Keep the transformer open circuited
Make sure that the insulation resistance (Megger) values are sufficient.
Procedure
Before the test, the following information about the transformer must be obtained and checked
Primary and secondary voltage
Voltage ratio values.
Connect the HV and LV leads of the meter to the HV and LV terminals of the transformer.
Switch ON the meter
Press “Group” button on Measurement column.
Acceptance criteria On the top of the display screen, the vector group of the transformer will be displayed. Work instructions for safety.
Do not touch the leads while the meter is switched ON.
Switch OFF the meter before remove of the leads.
Always follow general safety instructions of the area.
3.3
Transformer Voltage Ratio Test
Purpose: To ensure that the turns ratio of the windings is correct and that the tapping on any of the windings have been made at correct position. Tests should be performed as per IEC – 60076 test standards. Apparatus
Transformer turns ratio meter
Manual for transformer ratio meter
Preparation of sample
Keep the transformer open circuited.
Make sure the insulation resistances (Megger values) are sufficient.
Procedure
Before testing, the following information about the transformer must be obtained and checked.
Primary and secondary voltage.
Voltage ratio values.
Select the tapping. Connect HV & LV leads of the meter to the HV and LV bushing terminals of the transformer respectively.
Switch on the meter.
Press “Ratio” button on Measurement column.
Enter the vector group of the transformer.
Enter the required phase or A/N (To get ratio of all phases at selected position)
Record the readings.
Perform the test for all tap positions.
Note: The Transformer turns ratio meter has an inbuilt power supply with voltage used being low such as 8 -10 Volts, 50HZ. Acceptable criteria In the event that the voltage ratio does not match the ±0.5% tolerance is allowed from specified values. (As per IEC 60076).
Measured values should be in the following range.
11kV/415V (2.5% to -7.5% of 33kV/415V (2.5% to -7.5% of Rated Voltage)
Rated Voltage)
Tap 1: 46.82 ≤Measured Value ≤ Tap 1: 140.46 ≤Measured Value ≤ 47.29
141.88
Tap 2: 45.68 ≤Measured Value ≤ Tap 2: 137.04 ≤Measured Value ≤ 46.14
138.42
Tap 3: 44.54 ≤Measured Value ≤ Tap 3: 133.61 ≤Measured Value ≤ 44.99
134.96
Tap 4: 43.39 ≤Measured Value ≤ Tap 4: 130.18 ≤Measured Value ≤ 43.83
131.50
Tap 5: 42.25 ≤Measured Value ≤ Tap 5: 126.76 ≤Measured Value ≤ 42.68
128.04
Work instructions for safety:
Do not touch the leads while the meter is switched ON.
Switch OFF the meter before removal of leads.
Always follow general safety instructions on the area
3.4
Transformer DC Winding Resistance Test
Purpose: To measure the DC resistance between lines of all windings and to detect faulty or poorly made connections. Test should be performed as per IEC – 60076 test standard. Test results are important in full load loss measurement. Apparatus
Transformer winding resistance meter.
Manual for the meter.
Preparation of the sample
Isolate the transformer.
Procedure
Connect the potential 1 output to the HV winding and potential 2 to the LV winding of the transformer to be tested.
Test current output terminals should be connected to the upper point of the HV terminals in which the resistance has to be measured. In the case of Dyn vector connected transformers connection sequence for HV is A&B, B&C, C&A. Connection sequence for LV is a&b, b&c, c&a.
Select appropriate ranges of resistance.
Then switch on the power switch.
Then press the start switch.
The meter will inject current and start measuring.
Do not touch the leads while the danger sign appears.
Record the resistance values when safe sign appears.
Winding temperature at the time of measuring the transformer winding has to be recorded.
Work Instructions for safety
Always make sure the instrument body is earthed before switch ON.
Do not disconnect the leads until the RED warning light disappears
Always follow general safety instructions of the area.
NB: The winding resistance test results obtained above are used in calculating the Full load loss
3.5 Transformer Oil Dielectric Test Purpose To confirm the electrical strength of the transformer oil. Apparatus Oil Dielectric Strength test se Preparation of sample
The sample should be collected from the bottom of the container or transformer.
Sample should be collected to a clean, dry container.
Before collecting the sample, allow slug to drain off.
Procedure
Fill the oil sample to the test vessel up to a level about 10mm above the electrodes level. Put the magnetic stir in to the test vessel.
The electrodes are set at 2.5mm/±0.1mm gap. If there is any suspicion, check the gap.
Select the mode of operation as Automatic or Manual. In manual operation, the rate of rise of applied voltage should be 2kV/second ± 0.2kV/second.
In the case of automatic operation, machine allows a pause of 2 minutes after each breakdown before re-application of the voltage. The machine conducts the test for six times on the same cell filling and the mean value of the tests will be automatically printed on the attached printer.
Acceptance criteria
Average breakdown voltage of the oil must be > 50kV for transformers.
Work instructions
Always make sure that the instrument body is earthed before the meter is switched ON.
3.6
Do not try to open the instrument while testing oil.
Always follow general safety instructions of the area Transformer Separate Source Voltage Withstand Test
Purpose: To determine the integrity of the insulation between windings and earth. Tests should be performed as per IEC – 60076 test standards. Apparatus
AC Dielectric test set. (6T CD 100-10)
Manual of the AC Dielectric Test Set
Preparation of sample
Transformer should be isolated
Clean the bushings thoroughly with a clean piece of cloth.
Make sure the oil level of the transformer is at the top level.
Procedure
Bushing terminals of the windings under test are connected together using a conducting wire. The rest of the windings of the transformer are also connected together as above and connected to the tank and then tank is earthed. Then the appropriate test voltage is applied as per given under acceptance criteria below. Select the rate of voltage rise and apply the voltage.
This is performed on both HV and LV sides at power frequency.
The voltage is gradually increased up to the value below. Holding at the above voltage up to recommended duration. Reduce the voltage gradually before switching off.
Note: Insulation failure during the test is indicated by sudden increase of leakage current indicated on the test set. This would trip-off the test supply voltage. Acceptance Criteria
For 33kV – When the HV side is subjected to 70kV, it should withstand for 1 minute.
For 33kV/415V – when the LV side is subjected to 3kV, it should withstand for 1 minute.
For 11kV – when the HV side is subjected to 28kV, it should withstand for 1 minute.
For 11kV/415V – When the LV side is subjected to 3kV, is should withstand for 1 minute.
Work instructions for safety
Never switch ON the HV Tester when someone is inside the testing area.
Switch off the output voltage before change the HV connections.
Do not operate other electrical instruments while HV Tester is switched ON.
Always follow general safety instructions of the area
3.7
Transformer Induced Over Voltage Test At High Frequency
Purpose To verify voltage withstand strength between the windings and Earth, the withstand strength between the phases, and between turns of a phase under test. The test should be performed as per IEC – 60076 test standards. Apparatus
High frequency tester
Manual of the High frequency tester.
Preparation of sample
Transformer should be isolated
Clean the bushings thoroughly with a clean piece of cloth.
Make sure that the oil level of the transformer is at top level.
Make sure that the transformer tap selector is at rated tap position.
Procedure
Connect the high frequency generator output to the low voltage winding of the transformer while high voltage windings are open circuited. Make sure that the same output terminal sequence of the generator is connected.
Increase the voltage slowly by rotating the control switch on the control panel until double the rated voltage of low voltage winding is applied. A gradual increase of the brightness of the set of bulbs could be observed.
Note: If the transformer is faulty, the circuit is tripped off in the test set.
Since the frequency of the test supply is 120 HZ (This value is fixed for newest High Frequency Generator), the test duration is 50seconds.
Acceptance Criteria Sustaining the brightness at peak level for 50 seconds indicates the successful voltage withstanding strength. Work instructions for safety
Switch ON the HF panel only after connecting the test leads to the transformer.
Switch OFF the output voltage before remove the leads from the transformer.
Always follow general safety instruction of the area.
3.8 Transformer No Load Test (Core Loss- Hysteresis Loss and Eddy current loss Purpose To determine the No Load losses of a transformer. It also checks whether any damages have been caused to windings and insulation from prior tests. The test should be performed as per IEC – 60076 test standards. Apparatus AC Analyser. Preparation
Transformer should be isolated.
Clean the bushings thoroughly with a clean piece of cloth.
Make sure that the oil level of the transformer is at top level.
Make sure that the transformer tap selector is at rated tap position.
Procedure
Connect n,a,b,c bushing leads to the respective test leads.
Maintain HV side open circuited.
Adjust current transformer tappings to get an appropriate current according to the transformer to be tested. Generally, 5% of the rated current could be considered as a guide.
Apply the desired CT, PT ratio values and guaranteed loss value.
Apply the rated voltage by use of Air Circuit Breaker.
Measure the parameters by pressing the start/stop button of instrument.
By pressing the start/stop button again the measured values will be stored.
Switch off the air circuit breaker.
Acceptance Criteria
No load current shall be less than 5% of the rated current.
The deviation of the No load loss value should be less than 15% of the specified value.
Work instructions
Make sure the meter body is connected to the Earth before switch ON the meter.
Always short circuit the secondary terminals of the current transformers before switch off the voltage to the transformer.
Always follow general safety instructions of the area
3.9
Transformer Full Load Loss Test (Copper Losses)
Purpose To assess the Full Load Loss (copper loss) and the impedance voltage of a transformer. Tests should be performed as per IEC – 60076 test standards. Apparatus
AC Analyser
Manual for the AC analyser.
Preparation of sample
Transformer should be isolated
Clean the bushings thoroughly with a clean piece of cloth
Make sure the oil level of the transformer is at the top level.
Make sure that the transformer tap selector is at the rated tap position.
Procedure
Short circuit the low voltage winding bushing terminals using a thick flat copper bar which is sufficient to carry rated low voltage current.
Connect A.B.C bushing leads to the respective test leads.
Calculate the rated current of the high voltage winding and select the CT tap position according to it.
Apply the CT & PT ratio values to the meter.
Switch on the air circuit breaker.
Measure the parameters after injecting the desired rated current by pressing the start/stop button of the instrument. Pressing the start/stop button again, the measured values can be stored on the display of the meter.
Switch off the air circuit breaker.
Care should be taken to avoid supplying current for longer durations during the test in order to prevent heating of the windings, which eventually introduce additional losses.
Record the room temperature
Acceptance criteria
Deviation of full load losses corrected to 750 C shall be within 15% of the specified value.
Total losses – deviation of the component losses should be within 15% while maintaining the deviation of the total losses within10% of the specified value.
Work instructions for safety
Make sure that the meter body is switched to earth before switch ON the meter.
Always short circuit the secondary terminals of the current transformers before switch off the voltage to the transformer.
Always follow general safety instruction of the area.
3.10
Zero Sequence Impedance Test
Purpose To determine the zero sequence impedance of the transformer. Test should be done as per IEC – 76 test standards. Apparatus
AC Analyzer
Votmeter
Preparation of sample
Transformer should be isolated
Clean the bushings thoroughly with a clean piece of cloth.
Make sure that the oil level of the transformer is at the top level.
Make sure that the transformer tap selector is at rated tap position.
Procedure
Short-circuit High Voltage bushing terminals of the three phases.
Connect the circuit as shown in the circuit arrangement.
Apply a single phase voltage of about 200V with the same frequency as the operating frequency of the transformer across the neutral and the short circuited point.
Measure the voltage (V) and current (I).
Calculate the zero sequence impedance (Z0) using the formula Z0 = 3V/I
Acceptance Criteria.
The zero sequence impedance should be within a 10% deviation from the designed value.
Work instructions for safety
After completion of the circuit wiring, apply a lower voltage and gradually increase the voltage up to the required value.
Switch off the circuit before disconnection.
Always follow general safety instruction of the area
3.11
Sound Level Test (Type Test).
Purpose
To determine the sound level of the transformer. Test should be performed as per IEC – 60076 test standards. Apparatus Integrating sound level meter (NL-05) Procedure
Transformer should be placed and mark points (at least 6 points) 0.3 meters away from its boundary. Energize the transformer under rated condition. Measure the noise level at the marked points holding the meter at the mid-point of the height of the transformer.
Measure the noise level after shutdown the transformer on the same points, to get the surrounding noise level.
Average value of difference of these two sets of readings give the noise level of the transformer.
Expression of results Noise level should be ≤ 52dB. Work instructions for safety
Always stay away from the energized transformer.
For any reason, do not get closer or touch the transformer before switch it OFF.
Always follow general safety instruction of the area.
3.12
Temperature Rise Test (Type Test)
Purpose To determine the temperature rise of the transformer. Test should be performed as per IEC – 60076 test standards. Apparatus
AC Analyser
Manual of AC Analyser
Thermometer
Preparation of sample
Transformer should be isolated
Clean the bushings thoroughly with a clean piece of cloth
Make sure the oil level of the transformer is at the top level.
Make sure that the transformer tap selector is at rated tap position.
Procedure
Connect the A,B,C terminals to the respective test leads.
Insert a thermometer into the thermometer pocket.
Sum of the guaranteed of the transformer to be injected during the test. When the steady state condition is achieved, the difference between the top oil temperature and then room temperature is recorded at three consecutive readings. Reduce the current to full load rated current and maintain it for another one hour. Again record the top oil temperature and room temperature.
Maintain the lose figure by varying the current until steady temperature rise is obtained. Record the thermometer for every thirty minutes. If constant temperature appears at three consecutive readings, it will be considered as the steady condition
Top oil temperature rise can be obtained from the difference between top oil temperature reading and the room temperature.
Stop the supplying of the current and get the resistance values of both HV and LV windings. This should be performed until at least six different readings at regular intervals are recorded.
Plot a graph using the above data and obtain the resistance value at the time of switching off the current by extrapolating the graph. Using this value, temperature rise of the winding can be calculated using the following formula. Θ2 = (235+θ1)xR2/R1 – 235 Θ1= Room temperature 0C R1 = Resistance at room temperature (Ohms) Temperature rise = θ2 – Room temperature R2 = Resistance at the time of switching off (Ohms)
Plot the graph for both HV and LV windings.
Acceptance Criteria
Top oil temperature rise should be less than 550 C
Winding temperature rise should be less that 600 C
Work instructions for safety
Make sure the meter body is connected to the earth, before switching ON the meter.
Always short the secondary terminals of the current transformers before switching off the voltage to the transformer.
Use hand gloves to remove the leads from heated terminals of the transformer.
Always follow general safety instruction of the area.
3.13
Measurement Of Electrical Break Through Voltage Of Copper Wire
Purpose This test is carried out to assess the insulation of copper wire. Apparatus
Voltage regulator (Variable between 0 – 440V)
Salt solution (Water +5% NaCl, weight to weight)
Plastic rod (for forming the copper thread according to the table below)
Safety All safety procedures outlined in test method for dielectric voltage withstand test shall be followed during this test Procedure
Get a copper sampling with a length of at least 6m.
Wind the copper sample or the rod in spiral.
Prepare salt solution (water + salt in 1:5% weight ratio). Note: 1 g of water = 1ml of water.
Place the prepared copper spiral in the salt solution with terminals at least 20mm over the surface of the liquid.
Touch one set probe of voltage regulator to the salt solution and one end of copper wire should be isolated and kept 20mm over the liquid level.
Start with 0V and then increase the voltage up to 440V and maintain it for 30secs and check the break through voltage.
Acceptance Criteria There should not be any flash over point throughout the selected length Diameter of thread
Diameter of rod
0.100mm – 0.315mm
3.0mm
0.315mm – 1.000mm
18.0mm
1.000mm – 2.240mm
18.0mm
Work Instructions for safety
Connect the copper wire to the terminals and immerse in salt water prior to switch ON.
Do not touch the test leads, sample or salt solution while switch ON.
Always follow general safety instruction of the area.
3.14
Dry Power Frequency Voltage Withstand Test
Purpose To identify any flashover or punch of the bushings Apparatus High voltage test set Procedure Clamp the bushing as its intended use and apply the power frequency voltage as in given table Acceptance Criteria The bushing should be considered to have passed the test if no flashover or puncture occurs. If there is a puncture, the bushing shall be considered to have failed the test. If a flashover occurs the test shall be repeated once only. If during the repetition of the test no flashover or puncture occurs the bushing shall be considered to have passed the test. Nominal Voltage kV (rms)
Dry
lightning
withstand
impulse Power frequency withstand voltage voltage dry & wet kV (rms)
1.2/50micro sec kV (peak) 3.6
40
10
7.2
60
20
12
75
28
17.5
95
38
24
125
50
36
170
70
Work instructions for safety
Never switch ON the HV tester when someone is inside the testing area.
Switch OFF the output voltage before change the HV connections.
Do not operate other electrical instruments while HV tester is switched ON.
Always follow general safety instruction of the area.
3.15
Transformer Pressure Testing
Purpose
To ensure that the finished transformer withstand high pressure and to detect any leak points Apparatus
Pressure testing device
Preparation of sample
Isolate the transformer
Clean all the surfaces of the transformer
Procedure
Pump No. 1 for pumping oil to the transformer under test.
Pump No. 2 for evacuating oil from the tested transformer
Fix the T-socket for transformers that have drain valve.
Connect the pressure socket to the pressure relief valve socket, for the transformers not having drain valve.
Fully open the valve at pump No. 2
Fully close the valve at pump No. 1
Switch on the control panel
All sealed transformers (standard/special) 100 – 1000KVA (Having drain valve), Transformers that are not having drain valve 100 – 1000 KVA pressure up to 0.27 bar. (Pressure at cover plate).
For the seal transformers above 1000 KVA pressure testing is done by pumping the maximum temperature rise oil volume. (Design data output sheet for the oil volume at maximum temperature rise)
For conservator type transformers, the conservator is isolated and pressure up to 0.20 bar. (Pressure at cover plate level).
Switch on pump 1 and pump the oil to the transformer.
Keep the tank at that pump for 12 Hours’ time. Check for any leaks.
Switch on pump No. 2 and open the respective valves.
Zero the meter readings. Retrieve the same oil from the tank.
Remove the T-socket after fixing the oil nut.
Check the pressurized transformer for leaks.
To evacuate oil from pressurized transformer (tested), fully open the valve at pump No. 1 and fully close the valve at pump No. 2
Get the reading of the flow meter. Then press the reset button for zero reading.
Switch on pump No. 2. Open the valve at pump No. 2 to control the flow and evacuate oil from the transformer with reference to preceding flow meter reading.
Expression of results
The tested transformer should be free from leaks.
Work instructions for safety
Make sure all terminal ends, accessories, pressure relief valve, drain valve cover plate bolts are tightened properly.
Fix the oil inlet hose and inject oil until the required internal pressure is reached.
Examine quickly whether there is any abnormal oil leakage and if so, remove the injected oil as soon as possible.
Follow all the area safety rules
4.0
Post Shipping Inspection
It is important that inspection be made upon arrival of the transformer for any signs of damage incurred during shipment. This inspection should be made after removal of the transformer from the truck. The following items should be inspected closely for damage:
High voltage and low voltage bushings should be checked for cracks, chips, and leaks.
All external accessories should be checked for breakage, loss, and leaks.
Tank and radiators should be inspected for leaks, dents, scratches, and other signs of rough handling.
Paint should be inspected for damage.
Oil level gauge should be noted, along with the ambient temperature measurement
The factory shall be notified of any defects noted. External damage, or evidence of rough handling, may be an indication of internal damage. If any parts of the transformer have been removed for shipping, these will be noted on the Bill of Lading as separate items. These items should be checked for shipping damage as well. Post shipping testing: All transformers shall be subjected to routine tests according to IEC – 60076, by REA after delivery at REA Test Laboratory or any other approved testing facility recommended by REA. Test certificates shall be issued before delivery to site. Transformers that fail at this stage shall be rejected and the supplier shall replace them at his cost.
APPENDICES Appendix A: Plant & Process Checklist ✓/X No Aspect of inspection
Acceptance criteria
Remarks
. 1
Check for Valid Certification 1. Quality Management Certificate
ISO 9001:2008
2. Environmental
ISO 14001:2004
Management
Certificate 3. OHSAS Certificate 2
3
OHSAS 18001:2007
Check Availability of Documentation
HSEQ Policies and Manuals
Process Manual
Quality Plans
Manufacturing Procedures
Inspection Instructions
Test Protocols
Test reports
Process Checklists
Type test certificates
Calibration Records
Check
Availability
for
HSEQ
Procedures
4
and
Should have procedures in and
Procedure for Environmental
documents
Aspect
Environment,
Evaluation
(Environmental aspect register)
occupational
Hazard Identification (hazard
hazard
Risk Assessment (risk register)
Check for Availability of adequate
processes
should be documented
place
register)
Systems
updated on
risk
&
structure of the production team 5
Adequacy of the structure of the production facility
Availability of adequate
Qualification of the staff
structures and skills mix
Check
availability
of
physical
infrastructure
6
Production space
Sufficient
Storage space for raw materials
production, raw materials
& finished products
and finished products
space
Check availability of key production
Availability
line equipment
equipment
Crane
Fork lifts
Loading bay
Core cutting machines with step
of
for
key
lap technology
7
Oven
Testing lab
Vacuum chamber
Winding machines
Review Transformer Design Process for compliance to specifications & standards
Design
Procedure for identification & review
of
customer
requirements
8
Design Action Plan
Design review checklist
Design report
Confirm the technical specifications of
conformity
Client specifications
to
the major inputs/ raw materials Core Material
Core thickness (mm)
0.23 +-3%
Core Material
Cold rolled grain oriented
silicon
steel
Core Type
Three limb stacked
Core electrical resistivity (um)
0.48
Specific core loss at 50HZ for
0.69-1.11
Specific core loss at 50HZ for
1.17-1.57
1.7T
Coated
1.5T
Core sheet insulation
inorganic layer
Windings
Winding material
Copper wire class
Winding
Enameled Copper wire or foil
minimum
180
99.99%
450V
copper
content
with
Minimum copper wire electrical
in
solution
breakthrough withstand voltage
Winding
maximum
current
3.0 A/sqmm
Mineral oil
70kV
density Transformer Oil
Transformer Oil type
Transformer voltage
oil
breakdown
salt
PCB
Dielectric
dissipation
factor
None
0.001
900C
Water content
1.5mg/kg
Resistivity ohm at 200C
20
Insulation Boards
Insulation class
A
Minimum dielectric strength in
60kV/mm
oil
50:50
Yes
Sulphate : Wood mixture for diamond dotted paper (DDP)
Resin on both side of DDP Off-Load Tap Changer
Rated voltage
12kV or 36kV
Tap positions
5
Lockable
Yes
0,2.5,5
0.35
Hermetically
in
tap
position
selected
Tapping range (+-%)
Pressure Relief Valve
Operating pressure (bars)
Tank
Type
sealed
Material
Mild steel
Coating
Hot dip galvanized & powder coated
Coating thickness
100um
(50
galvanized + 50 powder coating)
Lifting hooks
Yes
Tank comprises of:
Base, tank, flange & top cover
Top cover fitting
Bolted, fitted with gaskets
9
Ability to trace a transformer back up to raw materials
10
Review transformer assembly
Availability
of
job card and drawings
signed job cards
fully
Core construction process
Check where core is securely
Securely clamped
Availability
clamped
11
Primary & Secondary winding Process
Check availability of winding instruction at place of work
of
work instruction at place of work
12
Drying Process
Check
availability of
Oven
which can accommodate biggest
Presence
of
appropriate Oven
size of transformer
Minimum drying time of 24
Work method for drying
hours
should
take
into
consideration:
24
hour
drying
time
30
minutes
from tanking
drying
lag to
13
Oil Filling process
Check weather oil filling is done
in oven 14
Oil
should
be
filled in oven
Tank Fabrication Check
conformity
to
minimum
dimensions
Minimum Tank Thickness
3mm for less than 400KVA & 6mm for
400KVA
&
above
Minimum base thickness
3mm for less than 400KVA & 6mm for
Minimum Cover plate thickness
400KVA
&
above
4 for less than 400KVA & 6 for
Minimum Flange thickness
Minimum Radiator thickness
400KVA & above
6mm
1.2mm
for
1-
1000KVA, 1.5mm for 1000KVA and above 15
Testing
Availability
Check availability of the following key
equipment necessary to
test equipment
carry out all the routine
High
frequency
voltage
Insulation resistance tester
Separate source voltage set
DC winding resistance meter
Transformer ratio &
vector
test
tests Presence of Test Laboratory
generator
of
group meter
16
AC analyzer
Oil Dielectric strength tester
Product handling & Packing
Ensure proper handling
Presence of proper handling equipment – forklifts, cranes, etc.
Presence
of
appropriate
&
sufficient storage space
Transformers to be securely packaged in wooden palates
Palates to be labeled
Appendix B: FAT Checklist
No.
Aspect of inspection
Acceptance criteria
Equipment
Physical Inspection 1
Visual
for 100% Compliance
Checks
completeness
of
a
fully assembled unit. Check
for
the
following
key
components
Tank
Pressure relief valve
Oil gauge
Bushing
Surge Arrestor mounting brackets
Rating plate
REA
Name
plate
Earthing terminal
Marked terminals
Mounting terminal on the base
Visual Checks
Remarks
1
Check
whether Hot dip zinc Galvanized, Elcometer surface powder coated, ≥ 100µm (
External
coating of tank is Hot dip zinc Galvanized and powder coated 2
Confirm
dimension Conformity to
and construction 3
Approved
drawing
Check: (a) Outdoor
a) 300mm for 11kV &
bushing
900mm for 33kV
Creepage distance (b) Phase to phase
b) Min 294mm
clearance (c) Phase to Earth clearance 4
c) Min 294mm
Check Oil level inside Should be above active part tank
when the Oil gauge is at minimum.
5
Check Packing in line Packing done with wooden with REA requirement
palates and clearly marked
Routine Test 1
Insulation
resistance ≥ 1000 MΩ when 5000V is 5000V
measurement
Insulation
applied for 60 seconds for resistance meter HV & E, HV & LV and 1000V
applied
for
60
seconds for LV&E 2
Separate
source Test set should not trip AC Dielectric Test
voltage withstands.
when 70kV is applied for 60 set seconds
for
33kV
transformer, 28kV for 11kV
transformer, and 3kV for LV windings. 3
Transformer ratio
Transformer ratio with ±5% Transformer
turns
tolerance for the respective ratio meter tap positions 4
Vector Group Test
Vector
group
displayed Transformer Ratio
should Dyn11 5
Meter
Winding resistance at All phase resistance values DC rated tap
should be similar.
Transformer
winding resistance meter
6
No load loss
The deviation of no load AC analyzer loss value should be ≤15% of specified value
No load current shall be less than 5% of rated
7
Load Loss
Deviation of full load AC analyzer losses corrected to 750 C shall be within 15% of the specified value.
Total losses – deviation of the component losses should be within 15% while maintaining the deviation of the total losses within10% of the specified value
8
Induced over voltage Should withstand double the High frequency test at High frequency
rated voltage at 120 HZ set applied to LV windings for 50 seconds.
9
Testing the electrical Measure
the
electrical Oil
dielectric
strength of transformer strength of Transformer oil strength test set oil
when a layer of oil is placed between
two
electrodes,
which are placed at 2.5mm apart. Average breakdown voltage of the oil must be > 50kV. 10
Sound level test
Noise level should be less Sound level meter than specified
11
Zero
sequence The
impedance
zero
sequence AC Analyzer
impedance should be within And Voltmeter a 10% deviation from the designed value.
12
Dry lightning impulse No flashover or puncture HV test set withstand
voltage occurs to the bushing at
1.2/50micro sec kV 75kV for 11kV transformer,
13
(peak):
170kV
Voltage withstand
transformer and 6kV for LV
Power
for
33kV
frequency No flashover or puncture HV test set
withstand voltage dry occurs to the bushing at & wet kV (rms):
28kV for 11kV transformer, 70kV for 33kV transformer and 3kV for LV.
14
Pressure testing
Transformer should be free Pressure from leaks
device
testing
