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TEKNISK RIKTLINJE

Enhet, verksamhetsomrde Datum Version

NT, Teknik 08-08-14 B TR 1-10E

Samrd

NF, NI

Vattenfall EldistributionSvenska Kraftnt 08-08-14 TR 1-10E rev BTekniska Riktlinjer

POWER TRANSFORMERS 2 MVA AND ABOVE

IntroductionThese guidelines are mainly based on Standard SS-EN 60076. The guidelines specifyalternative in the case of more possibilities and also include additions andelucidations to the standard. The guidelines can be made binding by the Purchaserand will then specify the requirements which together with the applicable standardare valid for the design and testing.

This document replace TR010:1.It has been compiled on order of Svenska Kraftnt (Swedish National Grid) and

Vattenfall Eldistribution AB. It has been approved as a suitable support for purchase.

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Index

1 SCOPE 9

2 STANDARDS 9

3 OPERATING CONDITIONS 11

3.1 Mode of operation ................................................................................................. 113.2 Ambient temperature.............................................................................................113.3 Network data .......................................................................................................... 12

4 ELECTRICAL DATA AND OTHER MAIN CHARACTERISTICS 13

4.1 Ratings......................................................................................................................134.2 Connection symbol................................................................................................144.3 Tapping range ......................................................................................................... 14

4.4 Insulation levels, creepage distances and air clearances.................................... 144.4.1 Insulation levels .......................................................................................... 144.4.2 Air clearances .............................................................................................. 144.4.3 Creepage distances......................................................................................154.4.4 Safety distances for inspection platform................................................. 16

4.5 Short circuit impedances (Impedance voltage) .................................................. 164.6 Short circuit withstand capability......................................................................... 164.7 Loading capability .................................................................................................. 17

4.7.1 General.........................................................................................................174.7.2 Loading cases for inter-bus transformers ............................................... 174.7.3 Loading cases for generator step up transformers ................................ 18

4.7.4 Additional loading requirements .............................................................. 20

4.8 Neutral point loading............................................................................................. 214.8.1 Inter bus transformers ............................................................................... 214.8.2 Transformers for HVDC .......................................................................... 214.8.3 Non effectively earthed transformers...................................................... 21

4.9 Type of cooling....................................................................................................... 214.10 Sound levels .......................................................................................................... 214.11 Core design............................................................................................................224.12 Winding design.....................................................................................................224.13 Insulation system..................................................................................................234.14 Other internal design requirements................................................................... 23

4.15 Alternative designs...............................................................................................23

4.15.1 Stabilising winding....................................................................................234.15.2 Auxiliary winding......................................................................................234.15.3 Off-circuit tap changing and change over between system voltages 24

4.16 Other data ............................................................................................................. 244.16.1 Supply voltages for motors, control equipment etc: ........................... 244.16.2 Contact breaking capacity ....................................................................... 254.16.3 Enclosure class and degree of protection ............................................. 254.16.4 Control equipment insulation levels etc................................................ 254.16.5 Disturbance requirements.......................................................................25

5 BUSHINGS 25

5.1 General.....................................................................................................................25


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5.2 Marking....................................................................................................................265.3 Capacitive taps........................................................................................................265.4 Oil level indicator ................................................................................................... 265.5 Special requirements for oil-SF6 connection assemblies.................................. 26

5.6 Special requirements for cable connection assemblies. .................................... 265.7 Special requirements for encapsulated buses. .................................................... 265.8 Terminals.................................................................................................................27

5.8.1 General.........................................................................................................275.8.2 Flat terminals...............................................................................................275.8.3 Cylindrical terminals...................................................................................275.8.4 Material.........................................................................................................275.8.5 Flat terminal dimensions ........................................................................... 285.8.6 Cylindrical terminal dimensions ............................................................... 29

5.9 Spare bushings ........................................................................................................ 29

6 OFF-CIRCUIT TAP-CHANGING AND SYSTEM VOLTAGE RECONNECTION 29

7 ON-LOAD TAP-CHANGERS 30

8 ON-LOAD TAP-CHANGER MOTOR DRIVE 30

8.1 General.....................................................................................................................308.2 Functional requirements........................................................................................31

9 SUPERVISORY EQUIPMENT 32

9.1 Gas and oil actuated relay ..................................................................................... 329.2 Oil level indicator ................................................................................................... 339.3 Temperature gauges (thermometers)................................................................... 339.4 On-load tap-changer overpressure relay ............................................................. 349.5 Cooling equipment gauges and transmitters ...................................................... 349.6 Sudden pressure monitor ...................................................................................... 359.7 On-line dissolved gas monitor ............................................................................. 35

10 COOLING EQUIPMENT 35

10.1 General .................................................................................................................. 3510.2 Cooler control equipment...................................................................................36

11 CONTROL EQUIPMENT DESIGN 39

11.1 General design......................................................................................................39

11.2 Ventilation, heating and lighting ........................................................................ 3911.3 Terminal blocks....................................................................................................40

11.3.1 General.......................................................................................................4011.3.2 Disposition of terminal groups in the control cabinet........................ 4011.3.3 Disposition of terminal groups in the OLTC motor drive ................ 4111.3.4 Disposition of terminal groups in the current transformer cubicle.. 42

12 BUSHING CURRENT TRANSFORMERS 43

12.1 General .................................................................................................................. 4312.2 Electrical data........................................................................................................43

12.2.1 Rated primary currents ............................................................................ 43

12.2.2 Rated secondary currents ........................................................................ 44


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12.2.3 Rated continuous thermal current ......................................................... 4412.2.4 Rated short time currents........................................................................ 4412.2.5 Insulation levels ........................................................................................ 4412.2.6 Cores and windings .................................................................................. 44

12.3 Design....................................................................................................................4512.3.1 General.......................................................................................................4512.3.2 Test terminals............................................................................................4512.3.3 Secondary terminals ................................................................................. 45

13 AUXILIARY WINDING 46

13.1 General .................................................................................................................. 4613.2 Auxiliary winding terminals. Main fuses. .......................................................... 4613.3 Load switch...........................................................................................................4613.4 Auxiliary transformer...........................................................................................4613.5 Fuses for local power supply, impedance protection and cooling

equipment...............................................................................................................47 13.6 Local power supply connection box ................................................................. 4713.7 Neutral conductor................................................................................................4713.8 Protective earth conductor and protective earthing........................................ 4713.9 Auxiliary power circuit connection diagram .................................................... 48

14 POWER AND CONTROL CABLES 48

15 TRANSFORMER TANK 49

15.1 General .................................................................................................................. 4915.2 Vacuum safety ...................................................................................................... 4915.3 Cover......................................................................................................................4915.4 Hand holes ............................................................................................................ 4915.5 Valves.....................................................................................................................49

15.5.1 General.......................................................................................................4915.5.2 Sampling valves.........................................................................................4915.5.3 Valve for on-line oil analysis................................................................... 5015.5.4 Valves for extra heat exchanger ............................................................. 5015.5.5 Sudden pressure monitor valves ............................................................ 50

15.6 Pressure relief valve ............................................................................................. 5015.7 Gaskets .................................................................................................................. 5015.8 Erection, Lifting devices, Transport.................................................................. 5115.9 Gas and oil actuated relay inspection platform................................................5215.10 Track gauges ....................................................................................................... 52

15.10.1 General.....................................................................................................5215.10.2 Longitudinal movement ........................................................................ 5215.10.3 Lateral movement...................................................................................52

16 CORROSION PROTECTION AND SURFACE TREATMENT 54

16.1 Transformer tank, OLTC tank........................................................................... 5416.2 Connection boxes, cubicles and OLTC motor drive...................................... 54

16.2.1 Alt 1: Painting ........................................................................................... 5416.2.2 Alt 2:Hot dip galvanising......................................................................... 54

16.3 Screws etc..............................................................................................................5416.4 Coolers...................................................................................................................54


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17 EARTHING 55

17.1 Principal earthing diagram .................................................................................. 5517.2 Neutral point earthing ......................................................................................... 5517.3 Protective earthing ............................................................................................... 56

17.3.1 Transformer tank......................................................................................5617.3.2 Connection cubicles and control cabinet..............................................5617.3.3 On-load tap-changer ................................................................................ 5617.3.4 Auxiliary power equipment..................................................................... 5617.3.5 Separately erected cooling equipment ................................................... 5617.3.6 Other equipment ...................................................................................... 56

17.4 Core earthing ........................................................................................................ 56

18 OIL AND OIL SYSTEM 57

18.1 Oil quality requirements...................................................................................... 5718.2 Oil system..............................................................................................................58

18.3 Conservator...........................................................................................................5818.4 Dehydrating breather...........................................................................................5818.5 Oil sampling..........................................................................................................5818.6 On-line monitoring..............................................................................................58

19 MARKING 59

19.1 Plates ...................................................................................................................... 5919.1.1 Rating plate................................................................................................5919.1.2 Diagram plate............................................................................................5919.1.3 Accessory plate (for Um 170 kV).......................................................5919.1.4 Oil circuit diagram (for Um 170 kV) ................................................. 59

19.1.5 On-load tap-changer and motor drive plate......................................... 5919.1.6 Bushing current transformer plate and marking.................................. 6019.1.7 System voltage re-connection plate ....................................................... 6019.1.8 Other plates...............................................................................................60

20 INFORMATION IN THE BID 61

20.1 General .................................................................................................................. 6120.2 Bid content............................................................................................................61

21 QUALITY ASSURANCE 62

21.1 Quality and Eco Management Systems............................................................. 62

21.2 Quality manuals....................................................................................................6221.3 Quality inspection. Inspection plans ................................................................. 62

22 DESIGN REVIEW 63

23 FACTORY ACCEPTANCE TESTS. FINAL INSPECTION. 63

23.1 General .................................................................................................................. 6323.2 Standards. Testing specifications. ...................................................................... 6423.3 Testing environment............................................................................................6423.4 Instrumentation....................................................................................................6423.5 Tolerances ............................................................................................................. 6423.6 Test results and test reports................................................................................64

23.6.1 General.......................................................................................................64


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23.6.2 Bushing current transformers................................................................. 6523.7 Routine tests..........................................................................................................65

23.7.1 Measurement of winding resistance (SS-EN 60076-1, Cl 10.2)......... 6523.7.2 Measurement of impedance voltage, short circuit impedance and

load loss (SS-EN 60076-1, Cl 10.4) ........................................................ 6523.7.3 Measurement of no-load loss and current (SS-EN 60076-1, Cl10.5).............................................................................................................66

23.7.4 Measurement of zero sequence impedance (SS-EN 60076-1, Cl10.7).............................................................................................................66

23.7.5 Dielectric tests...........................................................................................6723.7.6 FRA ............................................................................................................ 6723.7.7 Pressure testing.........................................................................................6723.7.8 On-load tap-changer operation test.......................................................6723.7.9 Bushing current transformers................................................................. 6723.7.10 Core insulation resistance measurement............................................. 68

23.7.11 Winding insulation resistance measurement ...................................... 6823.7.12 Tests and inspections on accessories................................................... 6823.7.13 Painting inspection.................................................................................68

23.8 Type tests...............................................................................................................6823.8.1 Zero sequence impedance measurement .............................................. 6823.8.2 Lightning impulse test (SS-EN60076-3, Cl 13).................................... 6823.8.3 Temperature rise test ............................................................................... 6823.8.4 Overload temperature rise test ............................................................... 6923.8.5 Sound level measurement (SS-EN 60076-1, Cl 8.1.3 d) ..................... 7023.8.6 Thermal and dynamic short circuit withstand test. ............................. 7023.8.7 On load tap changer.................................................................................70

23.8.8 Bushings creepage distance verification for polluted conditions ...... 7023.8.9 Bushing current transformers................................................................. 7023.8.10 Inspection and testing of accessories .................................................. 71

24 SITE TESTS 71

24.1 Tests on transformer ready for operation ........................................................ 7124.1.1 Transformers 100 MVA and above and all GSU and HVDC units.7124.1.2 All other transformers ............................................................................. 71

24.2 Tests in service...................................................................................................... 7224.2.1 Transformers 100 MVA and above and all GSU and HVDC units.7224.2.2 All other transformers ............................................................................. 72

24.3 Site test certificates............................................................................................... 7225 TIME SCHEDULES 72

26 DOCUMENTATION 72

26.1 General .................................................................................................................. 7226.2 Tender documents ............................................................................................... 7226.3 Documents for approval..................................................................................... 7226.4 Instruction manual...............................................................................................73

27 Appendix 1 75

27.1 THE DRY SALT LAYER (DSL) POLLUTION TEST METHOD.........7527.1.1 Scope .......................................................................................................... 75


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27.1.2 Definitions.................................................................................................7527.1.3 General description of the DSL test method....................................... 7627.1.4 Test procedure..........................................................................................7827.1.5 Test Conditions ........................................................................................ 79

27.1.6 Acceptance criterion ................................................................................ 8027.1.7 References..................................................................................................80

28 Appendix 2 81

28.1 DATA COMPILATION FOR POWER TRANSFORMERS.................... 81


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1 SCOPE

These guidelines cover three phase 50 Hz oil immersed power transformers rated2 MVA and above.

Four categories are dealt with:

A Distribution system power transformers - rated 2 - 100 MVA andhighest voltage for equipment 12 - 170 kV with recommended ratings

B Inter-bus transformers - interconnecting voltage systems 82,5 kV andabove

C Generator step up (GSU) transformers

D High Voltage DC (HVDC) transformers

2 STANDARDS

If standards referred to have been revised, the ones in force at the ordering date shallbe considered as valid. SS-EN documents are the ruling requirements, thereafterCENELEC (EN, HD or TS documents) and thereafter IEC or ISO.

SS-EN / EN / IEC 60076 Power transformersSS-EN 60076-1 Part 1: GeneralSS-EN 60076-1/A1 Part 1: Amendment No. A1SS-EN 60076-1/A12 Part 1: Amendment No. A12SS-EN 60076-2 Part 2: Temperature riseSS-EN 60076-3 Part 3: Insulation levels and dielectric testsIEC 60076-4 Part 4: Guide to the lightning impulse and switching impulse

testing Power transformers and reactorsIEC 60076-5 Part 5: Ability to withstand short circuitIEC 60076-7 Part 7: Loading guide for oil-immersed power transformersIEC 60076-8 Part 8: Application GuideSS-EN 60076-10 Part 10: Determination of sound levelsIEC 60076-10-1 Part 10-1: Determination of sound levels .- Application

guideSS-EN 60076-11 Part 11: Dry-type transformersIEC 60076-14 Part 14: Design and application of liquid-immersed

power transformers using high-temperature insulationmaterials

IEC 61378-2 Converter transformers Part 2: Transformers forHVDC applications

SS-EN 50216 Power transformer and reactor fittingsSS-EN 50216-1 Part 1: GeneralSS-EN 50216-2 Part 2: Gas and oil actuated relay for liquid immersed

transformers and reactors with conservatorSS-EN 50216-2/A1 Part 2: Amendment No. A1

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SS-EN 50216-3 Part3: Protective relay for hermetically sealed-liquidimmersed transformers and reactors without gaseouscushion

SS-EN 50216-3/A1 Part 3: Amendment No. A1

SS-EN 50216-4 Part 4: Basic accessoriesSS-EN 50216-5 Part 5: Liquid level, pressure devices and flow metersSS-EN 50216-5/A1 Part 5: Amendment No. A1SS-EN 50216-5/A2 Part 5: Amendment No. A2SS-EN 50216-6 Part 6: Cooling equipment Removable radiators for oil- immersed transformersSS-EN 50216-7 Part 7: Electric pumps for transformer oilSS-EN 50216-8 Butterfly valves for insulating liquidsSS-EN 50216-9 Oil-to-water heat exchangers (not published)SS-EN 50216-10 Oil-to air heat exchangers (not published)SS-EN 10088-3 Stainless steel Part 3: Technical delivery conditions for

semi finished products, bars, rods, wire, sections andbright products of corrosion resisting steels for generalpurpose

SS-EN 50180 Bushings above 1 kV up to 36 kV and from 250 A to3,15 kA for liquid filled transformers

SS-EN 50243 Outdoor bushings for 24 kV and 36 kV and for 5 kAand 8 kA for liquid filled transformers

SS-EN 50299 Oil-immersed cable connection assemblies fortransformers and reactors having highest voltage forequipment Um from 72,5 to 550 kV

SS-EN 50386 Bushings up to 1 kV and from 250 A to 5 kA, for liquid

filled transformersCLC TS 50458 Capacitance graded outdoor bushings 52 kV up to 420kV for oil immersed transformers (not published)

IEC 60038 IEC standard voltagesSS-EN 6044-1 Instrument transformers; Part 1: Current transformersSS-EN 60071 Insulation co-ordination; Part 1, 2 and 5SS-EN 60137 Insulating bushings for alternating voltages above 1000 VSS-EN 60214-1 On-load tap-changersIEC 60214-2 Application guide for on-load tap-changersSS-EN 60296 Fluids for electrotechnical applications - Unused mineral

insulating oils for transformers and switchgear

IEC 60416 General principles for the formulation of graphicalsymbolsSS-EN 60417 Graphical symbols for use on equipmentSS-EN 60507 Artificial pollution tests on high-voltage insulators to be

used on a.c. systemsSS-EN 60529 Degrees of protection by enclosures (IP code)IEC TR 60616 Terminal and tapping markings for power transformersSS-EN 60617 Graphical symbols for diagramsSS-EN 60664-1 Insulation co-ordination for equipment within low-

voltage systemsIEC TR 60815 Guide for the selection of insulators in respect of

polluted conditionsVattenfall Eldistribution


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IEC 60905 Loading guide for dry-type power transformersSS-EN 61000 Electromagneitic compatibility; Part 1 - 6 (IEC or EN

shall apply if no SS-EN standards are published)SS-EN 61140 Protection against electric shock Common aspects for

installation and equipmentIEC TR 61462 Composite insulators Hollow insulators for use inoutdoor and indoor electrical equipment Definitions,test methods, acceptance criteria and designrecommendations

IEC 62199 Bushings for d.c. applicationIEC 62155 Hollow pressurized and unpressurized ceramic and glass

insulators for use in electrical equipment with ratedvoltages greater than 1000 V

SS-EN ISO 1461 Hot dip galvanized coatings on fabricated iron and steelarticles Specifications and test methods

SS-EN ISO 9001 Quality systems RequirementsSS-EN ISO 10684 Fasteners Hot dip galvanized coatingsSS-EN ISO 12944 Paints and varnishes Corrosion protection of steel

structures by protective paint systems; Part 1 - 8SS-EN ISO 14001 Environmental systems Requirements with guidance

for useSS-ISO 67087 Pipe work components Definition and selection of

DN (nominal size)SS 14 2324 Stainless steel SS steel 23 24SS 421 01 01 Power installations exceeding 1 kV ACCigr Report 204 Guidelines for conducting design reviews for

transformers 100 MVA and 123 kV and aboveCigr Report 209 The short circuit performance of power transformersELSK-FS 2004:1 Elskerhetsverkets freskrifter (New Swedish Safety

Code)AFS 1993:10 Swedish Work Environment Authority Regulations

3 OPERATING CONDITIONS

3.1 Mode of operation

The transformers shall if not otherwise specified be designed for outdoor erection

and continuous operation.

3.2 Ambient temperature

As a lower limit of ambient air temperature 40C shall apply. (Deviation from SS-EN 60076-1, Cl 1.2.1)

For all equipment due consideration shall be taken to the increased maximumambient temperature caused by the temperature of the transformer tank which isassumed to reach 105C on the cover. The lower limit ambient temperature 40Cshall be accounted for as well.



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For built in bushing current transformers the following shall apply (if not otherwiseverified by the supplier):

- maximum ambient temperature 115C

- maximum daily average temperature 105C

The supplier shall demand detailed information of how the transformer would beinstalled at site. If the purchaser in the Compilation of technical data requires a siteinstallation other then in open air, the supplier shall, dependent on the kind of siteinstallation, give information about minimum distances around the transformer. Adrawing with a proposal of the transformer arrangement shall be enclosed with thetender. The transformer shall be constructed in such a way that the allowedtemperature rises shall not exceed the stated requirements in IEC 60076 on site.Protective walls shall allow the cooling equipment to be located inside. Protective

walls for the purpose of sabotage protection shall, if built by Svenska Kraftnt,

alternatively financed by Svenska Kraftnt funds aimed for emergency management,fulfil the requirements stated in TR09-15.

3.3 Network data

If not otherwise stated the system earthing conditions are given in Table 3.1 and themaximum network short circuit power levels are given in Table 3.2. (Note that allconceivable combinations of lower levels may be at hand). The given values applyalso for multi winding transformers.

Highest voltage

for equipment, Um

System earthing X0/X+

(kV) ( - )1.1 Effectively earthed -3.6 Not effectively earthed -7.2 -"- -

12 -"- -

24 -"- -

36 -"- -

52 -"- -

82,5 -"- -

145 Effectively earthed 1 3 (IEC)170 -"- 1 3 (IEC)

245 -"- 1 3 (IEC)

420 -"- 1 3 (IEC)

Table 3.1: System earthing

Highest voltage

for equipment, Um

Short circuit powerprimary winding

Short circuit powersecondary winding

(kV) (MVA, ref Um)1.13.6 250 2507.2 500 500



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12 500 50024 1000 50036 2000 100052 3000 2000

82.5 4000 3000145 10000 8000170 10000 8000245 17000 12000420 25000

Table 3.2: Network short circuit power

The type of system earthing for the different networks is listed in Table 3.1, Systemearthing. If not otherwise stated the given range of the ratio between the zerosequence impedance and the positive sequence impedance shall be valid.

4 ELECTRICAL DATA AND OTHER MAINCHARACTERISTICS

4.1 Ratings

For transformers category A the ratings shall be chosen from Table 4.1.

Rated power (MVA) 4 6,3 10 16 25 40 63 100

Rated voltage (kV) Approximate impedance voltage

HV side LV side in principal tapping (%)

22.5 81,67% 11,5 7 7 8 9

45 81,67% 23 11,5 7 7 8 955 81,67% 23 11,5 7 7 8 9 10

80 81,67% 23 11,5 8 9 10 10

140 81,67% 46 23 11,5 9 10 10 12 12

145 81,67% 58 46 23 11,5 9 10 10 12 12

150 81,67% 46 23 11,5 9 10 10 12 12Table 4.1: Recommended standard ratings

Rated voltage 140 kV is used in the southern half of Sweden and 150 kV in thenorthern half. In some cases 145 kV is chosen for full flexibility.

For other transformers the ratings will be specified in every single case. In somecases the ratings will be specified indirectly by means of a so called normal loadingcase (Normal case in Clause 4.7) from which the ratings and impedance voltage

will be calculated.

In some cases a "high-load" case will be specified for inter-bus transformers togetherwith maximum allowable winding hotspot temperature for given ambient conditions.From these conditions a "conventional" rated power shall be established.



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4.2 Connection symbol

Transformers of category A shall normally have the connection symbol YNyn0.

For other transformers the connection symbol is specified in every single case.

4.3 Tapping range

The tapping range for transformers of category A shall be selected from Table 4.1.The tapping range for other transformers is specified in every single case.

4.4 Insulation levels, creepage distances and air clearances.

4.4.1 Insulation levels

Insulation levels shall fulfil the requirements in Table 4.2.

Highest voltage forequipment

(kV)

Insulation levelaccording to IEC 60076-3

1.1 AC33.6 LI40 AC107.2 LI60 AC2012 LI75 AC2824 LI125 AC5036 LI170 AC7052 LI250 AC95

82.5 LI325 AC140145 (South Sweden) LI550 AC230 LI250 AC95

170 (North Sweden) LI550 AC230 LI250 AC95245 SI750 LI850 - LI325 AC140420 SI1050 LI1300 - LI125 AC50

Table 4.2: Highest voltage for equipment and insulation levels

Note 1 For phase to phase insulation the following addition shall apply145 kV LI550 AC 275170 kV LI550 AC 275245 kV SI750 LI850420 kV SI1050 LI1300

Note 2 For the neutral point of autotransformers the following shall apply:420/145 kV LI250 AC95420/170 kV LI250 AC95420/245 kV LI250 AC95In some cases LI550 AC230 may be specified

4.4.2 Air clearances

The requirements on minimum air clearances are summarised in Table 4.3.



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Minimum free air clearanceHighest voltagefor equipment

(kV)phase - earth

(mm)phase - phase

(mm)3.6 60 607.2 90 9012 110 11024 220 22036 320 32052 480 480

82.5 750 750145 1100 1100170 1100 1100245 1900 2250420 3100 3500

Table 4.3: Minimum air clearances

Notes to Table 4:3: Air clearances for 170 kV and below are based upon SS 421 01 01 Air clearances for 245 and 420 kV are based upon SS EN 60076-3 The air clearance is assumed to be measured from bushing live parts In some cases the clearances have to be increased to account for the size of

connectors

4.4.3 Creepage distances

The creepage distance requirements for ceramic and polymeric insulators in cleanand polluted environment are summarised in Table 4.4.

Minimum creepage distanceCeramic type Polymeric typeHighest voltage

for equipment(kV)

Clean environmentClass I(mm)

Polluted environmentClass II and III

(mm)

Clean environmentClass I(mm)

3.6 60 90 -7.2 120 185 -12 200 300 15024 400 600 30036 600 900 45052 850 1300 650

82.5 1350 2100 1000145 2350 3700 1750170 2750 4300 2050245 6000 3000420 10000 5100

Table 4.4: Creepage distances

Notes to Table 4.4: Pollution classes according to IEC 60815 For an alternative method of ceramic type insulator performance in polluted

environment refer to Clause 23.8.8.



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For polymeric insulators the creepage distance is not a relevant parameter forthe performance in polluted environment. For the performance verificationrefer to Clause 23.8.8

For transformers having highest voltage for equipment 245 and 420 kV

environment Class II shall apply for all windings. The ratio (creepage distance) / (insulator length) must not exceed 3.5 for

ceramic type insulators. In case of environment Class II or III the insulator shall be designed with

alternating short and long sheds, i.e. of the self cleaning type. Creepage distances are given as minimum length.

4.4.4 Safety distances for inspection platform

For the design of the inspection platform and its ladder minimum safety distancesequal to the earth air clearance above increased by 6 % shall apply.

When applying this the distance from the neck to the finger tip is assumed to be 900mm and the distance from the neck to the sole of the foot to be 1600 mm.

4.5 Short circuit impedances (Impedance voltage)

For standardised (A) transformers the impedances are chosen from Table 4.1 if nototherwise stated (NOTE: Typical values). For other transformers the impedances arespecified in every single case.Limitations on zero sequence impedances could be set depending on size of neutralreactor or for the performance of the network system.

4.6 Short circuit withstand capability

The transformers shall withstand external short circuits on any voltage level. For atransformer set comprising a main unit and a regulating unit the short circuit

withstand requirement also applies to faults at the connections between the twounits.

The following shall be accounted for:

currents at three phase and two phase short circuits and earth faults the transformer operating at 105% of rated voltage the from the network incoming short circuit power to each bus is assumed to

vary linearly with the voltage the system earthing and the most unfavourable ratio between the zerosequence and positive sequence network impedances

the short circuit impedances being 0.95 times the guaranteed values for windings with non effectively earthed neutral point it shall be assumed

that no earth fault can occur between the line and neutral on the transformeritself

generator step-up transformers shall also be capable of withstandingswitching in at 180 phase opposition



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A new transformer shall be able to withstand minimum three consecutive threephase short circuits at the dimensioning short circuit condition.

The dimensioning short circuit current halved a new transformer must be able to

withstand nine consecutive short circuits.

4.7 Loading capability

4.7.1 General

If not otherwise stated all transformers, even multi winding transformers, shall becapable of continuous operation with rated current in all windings without exceedingthe allowable standardised temperature rises.

In addition the transformers shall, if specified, fulfil the loading requirements inClause 4.7.2 Loading cases for inter-bus transformers and Clause 4.7.3 Loading casesfor generator step up transformers.

Further requirements are specified in Clause 4.7.4.

4.7.2 Loading cases for inter-bus transformers

Loading cases for verification and/ or optimising of rated voltages

Case No. OLTCPos

- WindingI

WindingII

WindingIII

WindingIV

Unit

#0No-load

0 U ? U2r U3r kV

U U1 U2 ? kV

P ? P2 P3 MW

#1

Normal case 0

Q ? Q2 Q3 Mvar

U U1 U2 ? kV

P ? P2 P3 MW

#2

Control case?

Q Q1 ? Q3 Mvar

U kV

P MW

#3Control case

Q Mvar

U KV

P MW

#4Control case

Q Mvar

U ? U2 ? kV

P ? P2 P3 MW

#5Control case

X

Q ? Q2 Q3 Mvar

U U1 ? ? KV

P ? P2 P3 MW

#6Peak load, emergencyoperation

Hot-spot temp CAmbient temp C

Y

Q ? Q2 Q3 Mvar

U ? U2 ? kV#7

Temperature rise test

Z

P ? P2 P3 MW



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(conventional)Q ? Q2 Q3 Mvar

Sign conventions:

-Positive power = power into the winding

-Negative power = power out of the winding-A reactor is consuming reactive power

-A capacitor is producing reactive power

Table 4.5: Loading cases for inter-bus transformers

1,2


0,0

0 6 12 1

0,2

0,4

0,6

load

(p.u.

) 0,8

1,0

8 24

time of day

Figure 4.1: Emergency operation for inter-bus transformers

Notes to Table 4.5 and Figure 4.1: The "Normal case" is decisive for the determination of the no load ratio and

Peak lo rge e r atemergency op ion acco ing to F re 4.1 E rgency eration.

es marke with " ll be ca d by idde ufa er.The transformer losses shall be considered.

ombined ain d regul (boo rans th dinglid with the two operating together.

imum allowed te per ure rises ccording o SS-EN 2 shall be

fulfilled in all the loa g e for "Pe load / E cy n" where the m ature re men spec Cl .7.4.

4.7.3 Loading cases for generator step up transformers

for verificatio d optimisi ed s

the impedance voltage. The " ad / Eme ncy operation" is th base for the load p ofile

erat rd igu me op Valu d " ? sha lculate the b r /man ctur In case of c

cases are vam an ating ster) t formers e loa

Max m at a t 60076

din cases exc pt ak mergenoperatio te per quire ts are ified in ause 4

Loading cases n an /or ng of rat voltage

Case No. OLTCPos

- Winding Winding Winding Winding UnitI II III IV

#0No-load

2r 3r- U ? Ug Ug kV

U 100%UN Ug2r Ug3r kV#1Normal case

-

P ? Pg2r Pg3r MW


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U1=normal UNPg=PgrQ1=0

Q 0 ? ? Mvar

U 95%UN ? ? kV

P ? Pg2r 3rPg MW

#2Control case

U1=95%UNPg=Pgr, Q1=-1/3Pgr

-Q Q1 ? ? Mvar

U 100%UN ? ? kV

P ? Pg2r Pg3r MW

#3Control caseU1=100%UN

Q1=-Pg=Pgr,1/3Pgr

-

Q Q1 ? ? Mvar

U 105%UN ? ? kV

P ? Pg2r Pg3r MW

#4Control case

U1=105%UNPg=Pgr, Q1=-1/4Pgr

-

Q Q1 ? ? Mvar

U ? ? ? kV

P ? 0 0 MW

#5Control caseU1=100%UNPr=0, Q1=1/6Pgr

-

Q Q1 ? Mvar?

U ? Ug2r Ug3r kV

P ? Pg2r Pg3r MW

#6Control caseHotspot 98C, ambient

Qg=1/3P

3r Mvar

20C -Ug=100%UgrPg=Pgr

Q ? 1/3Pg2r 1/3Pg

gr

U ? Ug2r-5% Ug3r-5% kV


P ? Pg2r Pg3r MW

#7Temperature rise

test(conventional) -

Ug=95%Ugr Q ? 1/3Pg2r 1/3Pg3r MvarPg=PgrQg=1/3Pgr

Sign conventions: Legend:

- Positive power = power into the winding - N = network

- Negative power = power out of the

winding

- r = rated

- A reactor is consuming reactive power - g = generator

- A capacitor is producing reactive power - 1,2,3 =winding #

Table 4.6: Loading cases for generator step up transformers

Notes to Table 4.6:- The "Normal case" is decisive for the determination of the no load ratio and the

impedance voltage.- Values marked with " ? " shall be calculated by the bidder/manufacturer.- The transformer losses shall be considered.- Maximum allowed temperature rises according to SS-EN 60076-2 shall be

fulfilled in all the loading cases except for Case #6 where other requirements arespecified.


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The transformer neutral and its bushing as well as built in bushing currenttransformers shall have the same loading capability as the corresponding lineterminals (for auto connection the line terminals of the high voltage side).HVDC converter transformer loadings will be derived from the over all plant

requirements.

4.8 Neutral point loading

4.8.1 Inter bus transformers

If not otherwise stated the neutral points of three limbed auto-connected inter bustransformers (400/220 and 400/130 kV shall be capable of continuously carrying aDC current of 200 A for 10 minutes the transformer operating at its worst loadingand at maximum ambient temperature.In case of single phase units or five limbed three phase units the supplier shall statethe maximum allowed continuous neutral point DC current

4.8.2 Transformers for HVDC

If not otherwise stated the AC side neutral of an HVDC transformer shall be capableof continuously carrying a DC current of 10 A the transformer operating at its worstloading at maximum ambient temperature.

4.8.3 Non effectively earthed transformers

If not otherwise stated non effectively earthed neutral points shall be capable of- continuously carrying an AC current amounting to 10% of the rated phase

current and the transformer operating at its worst loading at maximum ambienttemperature

- carrying rated phase current for 30 s and no current for 15 min repeated threetimes every three hours during a 24 h period and the transformer operating at itsworst loading at maximum ambient temperature

4.9 Type of cooling

Cooling type ONAN is the normal case for transformers rated 25 MVA and below.For higher ratings cooling type ONAN, ONAF or OFAF is to be optimisedconsidering the loss evaluation and the available space. Type OFWF is used only ifspecified.For type OD.. cooling the same maximum allowable temperature rise as for typeOF.. shall apply (Deviation from SS-EN 60076-2, Cl 4.2). Furthermore whendisconnecting a fully loaded transformer at max ambient temperature it shall not berequired to pump oil through the windings, i.e. no post tripping cooling.

4.10 Sound levels

If not otherwise specified the soundpowerlevels in Table 4.7 shall apply:

Max allowable sound levelEquivalent two-winding rating

MVASound power level LWA

dB(A)6,3 6510 68



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16 7225 7740 8263 85100 88150 92200 94300 97500 100750 103

Table 4.7: Maximum allowed soundpower levels

A positive tolerance of +0 dB(A) shall be valid.

The sound power level LWAshall be measured in accordance with IEC 60076-10 andshall apply both with and without cooling equipment in operation.

For transformers with variable flux voltage regulation sound level measurement shallbe performed at the tapping giving the highest core flux density.

In case of separately erected cooling equipment maximum allowable sound level willbe specified in every single case.

The transformer size is equivalent to the high voltage winding rated power.

For intermediate sizes linear interpolation shall be used.

Factory measured sound power level shall be rounded off to the closest integer valuebefore comparison with the guarantee level.

4.11 Core design

As the normal case the transformer core shall be of the three limbed core type. Fivelimbed core or shell type may be used in special cases if explicitly stated in theinquiry.

4.12 Winding design

The manufacturer shall state the depolymerisation number (DP) of the insulation

paper used in the windings:

- new paper from the paper sub-supplier (actual value)- processed and tested transformer ready for shipping (expected value)

Thermally upgraded paper may be used only after written approval from thepurchaser. The method of reduction of ageing effects shall be described as well asany negative effects of this upgrading.



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4.13 Insulation system

The tender shall present approximate insulation system dimensions for each windingpair in accordance with the figure below. The insulation is lumped together in abarrier block with radial thickness (X) and spacer block with a tangential width (Y)

indicating the relativeamount of insulation material in the respective direction in themain duct (duct length = 1 and duct width =1) between two windings.

The Barrierthickness X incorporates pressboard cylinders and winding paperdistributed across the main duct.

The Spacerwidth Y incorporates the spacers distributed along the main duct.

------------------------------ WINDING 1 -------------------------------

SPACERS OIL

1-X

BARRIERS

X

Y 1-Y

------------------------------ WINDING 2 -------------------------------

Figure 4.2: Insulation system dimensions

4.14 Other internal design requirements

The transformer shall be designed in such a way that copper sulphide deposition willbe prevented e.g. high temperature varnish on winding wires and bare conductors.

4.15 Alternative designs

4.15.1 Stabilising winding

If not otherwise stated or there are special limits on zero sequence impedances nostabilising winding shall be furnished. If requested its insulation level shall be chosenaccording to its highest voltage for equipment.

If a stabilising winding is provided the delta shall be closed and earthed externally tothe tank cover.

4.15.2 Auxiliary winding

A 400 V auxiliary winding shall be furnished on standardised transformers, for othertransformers only if specified.



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Standardised transformers shall be provided with an auxiliary winding 420/242 Vwith tappings at -5, 0 and +5%. For transformers having voltage regulation of typeVFVV (variable core flux) tappings at -7.5, 0 and +7.5% may be specified.

If an auto connected matching transformer is provided this must be designed for arated supply voltage of maximum 420 V.

For standardised transformers the rated power shall be chosen from the followingtable

Power transformer Auxiliary transformer(MVA) (kVA)

4 256,3 4010 6316 10025 10040 10063 250100 250

Table 4.8: Auxiliary winding rated power

For other transformers the auxiliary power rating is specified in every single case.However, the maximum power will be 400 kVA.

4.15.3 Off-circuit tap changing and change over between system voltages

Off-circuit tap changing and change over between system voltages is not the normalcase but will be specified if required.

4.16 Other data

4.16.1 Supply voltages for motors, control equipment etc:

On-load tap-changer motor operationNormally 110 V dc (in some cases 220 V dc) or400/230 V ac.

On-load tap-changer motor drive control and indication:110 V ac from an interposing transformer or110 V dc (in some cases 220 V dc).

Cooling equipment motors:400/230 V ac

Cooling equipment control:-operation voltage 230 V ac, single phase-signalling voltage 110 V or 220 V dc

Other control equipment:-operation voltage 110 or 220 V dc-signalling voltage 110 or 220 V dc

Lighting and heater:230 V ac, single phase



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Maximum voltage variation -15% to +10% shall apply at the connection point ofapparatuses.

4.16.2 Contact breaking capacity

Contacts for external use shall at least have the following breaking capacity if nototherwise specified in the relevant transformer fitting standard (SS-EN 50216):

0.15 A at 220 V dc and L/R = 40 ms 0.30 A at 110 V dc and L/R = 40 ms

4.16.3 Enclosure class and degree of protection

Apparatuses and connection boxes shall at least fulfil enclosure class IP45 accordingto SS-EN 60529 and degree of protection Class I according to SS-EN 61140.

4.16.4 Control equipment insulation levels etc.

The following insulation categories in accordance with SS-EN 60664-1 shall apply:

Equipment Over voltage

category

Material

group

Pollution

degree

Terminal blocks IV I 2Current transformer circuits IV I 2Motors IV I 2Other parts IV I 2

Table 4.9: Insulation categories

4.16.5 Disturbance requirements

Control equipment, cooling equipment and on-load tap-changer motor driveequipment shall fulfil the requirements set up in SS-EN 61000

5 BUSHINGS

5.1 General

For highest voltage for equipment Um 52 kV condenser type bushings shall beused. Applicable standard is SS-EN 60137.

For highest voltage for equipment Um < 52 kV either condenser type or ceramic

type bushings may be used.

Condenser type bushings may be of either oil impregnated paper (OIP) or resinimpregnated paper (RIP) type. However if specified dry type bushings shall be used.

The insulator for condenser type bushings may be of either ceramic or polymerictype and will specified in every single case. For voltages 245 kV polymeric type ofbushing (housing) shall be used.

Ceramic type bushing shall fulfil SS-EN 50180, SS-EN 50243 or SS-EN 50386.Deviations may be made for the connection details on the oil side but first after

written approval from the purchaser.Vattenfall Eldistribution


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For each combination of highest voltage for equipment and insulation level only onetype of bushing is allowed.

Extended bushing turrets may be specified to facilitate future installation of a sound

level reduction enclosure.

5.2 Marking

Each bushing shall have a rating plate showing the identification, e.g. type andcatalogue No. On smaller bushings this can be stamped into the top bolt or theflange or on a separate plate on the transformer.

5.3 Capacitive taps

Phase bushings for highest voltage for equipment Um 82.5 kV shall be equippedwith capacitive taps for measuring purposes. The measurement taps shall be

connected to a common connection box at service level where they normally shall beshort circuited.

5.4 Oil level indicator

Bushings for highest voltage for equipment Um 245 kV shall be provided with oillevel indication

5.5 Special requirements for oil-SF6 connection assemblies.

The transformer supplier shall provide a detailed description of the oil level andpressure supervision system for the bushings.

It is the transformer suppliers responsibility to make such arrangements that shortcircuit bridges have no harmful impact on the transformer.

The over all responsibility of the interface lies on the transformer supplier.

Other requirements such as pressure supervision, expansion chambers, levelindication etc are specified in every single case.

5.6 Special requirements for cable connection assemblies.

For highest voltage for equipment 82.5 kV and above the requirements given in SS-

EN 50299 and SS-EN 50299C1 shall apply.


Other requirements such as cable box with SF6, oil or air etc are specified in everysingle case.

5.7 Special requirements for encapsulated buses.

It is the transformer suppliers responsibility to make such arrangements that shortcircuit bridges have no harmful impact on the transformer.



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Other requirements such as interface, short circuit bridges etc are specified in everysingle case.

5.8 Terminals

5.8.1 General

Current carrying connections including screws, nuts and washers necessary for theconnection of external conductors are to be provided by the purchaser in case ofcondenser bushings.

The terminals shall primarily be provided with flat terminals (flags)

Cylindrical terminals are accepted in those cases were the terminal is a naturaltermination of the internal conductor arrangement.

5.8.2 Flat terminals

The flat terminal shall fulfil the dimension requirements below. To admit theassembly of the current carrying connection there must be a free space of minimum5 mm between the flat terminal and the apparatus to be connected.

The size of the flat terminal shall be selected from the table below:

Size Highest voltage for equipment52 kV >52 kV

2 - 40 400 A -4 - 75 630 - 1250 A9 - 125 1600 - 3150 A12 - 165 4000 A

Table 5.1: Flat terminals

5.8.3 Cylindrical terminals

The cylindrical terminal shall fulfil the dimension requirements below. The terminalshall be secured against rotation.

The size of the cylindrical terminal shall be selected from the table below:

Size Rated apparatus currentAluminium terminal Copper terminal

30 630 - 1250 A 630 - 1600 A40 1600 A 2000 - 2500 A60 2000 - 2500 A 3150 - 4000 A

Table 5.2: Cylindrical terminals

5.8.4 Material

Terminals of copper or a copper alloy shall be tin coated to layer thickness of at least50 m. Copper alloy sensitive to stress corrosion must not be used.



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Terminals of aluminium or an aluminium alloy must not be surface treated. In caseof an alloy this shall have the same corrosion resistance as pure aluminium.

Aluminium alloy sensitive to stress corrosion, layer corrosion or grain boundaryerosion must not be used.

Flat terminal of aluminium or an aluminium alloy shall have a hardness of at least HBmin 75.

5.8.5 Flat terminal dimensions

75

40

40

Size 2- 40

t10, =14

Figure 5.3: Flat terminal size 2-40

75

40

75

40 Size 4- 75

t15, =14


125

40

40

Size 9-125

t35, =14




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40

40

125

165 Size 12-125

t35, =14

Figure 5.6: Flat terminal size 12-125.8.6 Cylindrical termina5 l dimensions

125

Size 30: = 30Size 40: = 40Size 60: = 60

Figure 5.7: Cylindrical terminal

ply with the preferred ones spare bushings shall becluded in the tender.

D SYSTEM VOLTAGE

ction

shall not be possible to completely loosen connection pieces, screws and nuts.

5.9 Spare bushings

In the inquiry preferred bushings may be stated based upon the available spares. If

quoted bushings do not comin

6 OFF-CIRCUIT TAP-CHANGING ANRECONNECTION

Change of ratio (+x%, 0, -x%) and reconnection between system voltages (series-parallel, Y-D) shall be made with the transformer not in operation. The reconneshall be made by means of bolted connections accessible through hatches in thecover.

ItVattenfall Eldistribution


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7 ON-LOAD TAP-CHANGERS

or

ng technology in

rating the coarse orffect on equipment

forg built together in one unit.)

neral

n.

he drive shall be located for an easy operation in service.

me at motor operation must not exceed 8 s.

at the arrow

r, readable from the

the tap changer. The tap

Change of ratio in operation shall be made by high speed on-load tap-changers f

remote and local operation. The tap-changers shall fulfil the requirements in SS EN60214-1 and IEC 60214-2.

The diverter switch shall whenever suitable use vacuum switchiorder to minimise the maintenance requirements.

Special attention shall be paid to reduce recovery voltage transients on the 0.42 kVuxiliary system emerging from on-load tap-changer operations. Such transients maya

occur in case of free floating regulating windings when opehange-over selectors. These transients may have adverse ec

connected to the 0.42 kV system and consequently the supplier is obliged to take

easures for their reduction to non harmful levels.mIf applicable diverter switch oil compartments shall be provided with pressure or oilflow gauges.

The transformer shall be equipped with a legible mechanically linked indicatingdevice showing the position of the diverter and the tap selector. (Not applicableap-changers with diverter and operatint

8 ON-LOAD TAP-CHANGER MOTOR DRIVE

.1 Ge8

The operating mechanism shall be constructed for local and remote motor operatio

TContacts for raise and lower shall be electrically and mechanically mutually blocked.One complete operation must not take more than 25 turns at hand operation. Therequired number of turns shall be indicated on a plate on the drive. The operationti

As soon as the drive is in progress this must be indicated and labelled "KAR"(raising) and "MINSKAR" (lowering).

The drive shall be provided with legible and weather proof labels with arrows for thehand operation and also labelled "KA" (raise) and "MINSKA" (lower)

oints.pRaising means that a higher tapping number is connected when making a electricalraise operation or a clockwise operation.

The drive shall be provided with a legible position indicato

outside. The indicator shall be mechanically controlled byVattenfall Eldistribution


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positions shall be numbered from one and upwards. The highest ratio shall

he mechanical and electrical limiting devices shall be easily movable to any tapechanicallocking function to prevent harmful operation.

and operation of the other phases shall be prevented.

otor polarity must not imply a reversal of the rotation. When

e drive unit.

h istact will be used for signalling at protective

p.means of external breaking contacts in series with the

s are closed the operation cycle

yc evice isached, so called multi-step operation.

The drive shall be easily re-connectable so that independent of the operation pulsength only a single step operation will be carried out, so called step-by-step

disc

When the drive reaches either end limit the contacts for electrical stop shall open

oth in motor and control circuits for the actual operating direction. The limit

correspond to position No. 1, i.e. in the normal case this will give a higher voltage onthe low voltage side at a higher tap position.

Tposition. In addition each limiting device shall have an electrical and mbFor electrically operated single phase tap-changers a zero-voltage in any motor circuitshall be signalled8.2 Functional requirements

A change of the drive mat stand still all phase conductors shall be disconnected.

otor circuit fuses must not be located in thM

The motors shall be protected against overload by motor protective switches. In caseof single phase tap-changers the motor protective switches shall be of a designallowing for a common fusing of the three drive motors.

It must be possible to operate the motor protective switches by hand.

The motor protective switches shall be provided with an auxiliary contact whicclosed when the switch is open. This conswitch tripping.

Circuits for motor, control, position indication and heating shall be electricallycompletely separated.

A started cycle of operation shall be completed even if the operation pulse length isshorter than the time required for one step.

When an over current is passing through the tap-changer the drive motor shall stoThis shall be accomplished bydrive operating circuit. When these external contactshall be completed.

When the operation pulse length is longer than the time required for one step newles shall immediately follow until the pulse disappear or a limiting dc

re

leoperation. For another step to be performed the operation pulse must be

onnected and a new pulse must be given after completion of the first step.

bVattenfall Eldistribution


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switches shall have forced mechanical operation and also be independent of anyng force for its operation.spri

he following auxiliary contacts shall be provided:

One making contact which closes as soon as the drive is leaving its rest position

itching is immediately at hand or already underway.

before the actual load switching and whichremains closed until the operation cycle is completed. The time during which the

tchingtime.

The contact is to be used together with over current relay contacts to indicatend

Contacts for potentiometer transmitter tap position indication.

stand at least 0.3 A continuously.

cts shall be used for tap position indication and for parallel control.

be provided ifecified. If such contacts are not specified future addition of such contacts shall be

SUPERVISORY EQUIPMENT

oval.

y separate

ontacts:

T

and which remains closed until the operation cycle is completed.

This contact will indicate that a sw

One making contact which closes just

contact is closed shall as close as possible correspond to the critical swi

that the diverter switch has been subjected to over current during switching aconsequently calls for an inspection of the diverter switch contacts.

The potentiometer transmitter shall have as many positions (N) as the number oftappings and N-1 sub resistors. Each resistor shall be of about 10 or 50 with an

dividual spread of maximum 0.5%.in

For plus/minus and for coarse/fine tap-changing so called "run through" contactsust not indicate separate tap positions.m

The potentiometer transmitter shall with

The contaContacts for simultaneous or master follow parallel control shallsppossible.

9

The transformers shall normally be provided with the following gauges. These shallave a prompt making and breaking function.h

In order not to prevent the development of new technologies other configurations

ay be accepted, however, only after written apprm9.1 Gas and oil actuated relay

The gas and oil actuated relay shall be provided with two electricall

cVattenfall Eldistribution


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One closing for slow gas formation to be used for tripping.

One closing for heavy gas formation, heavy oil flow and low oil level to be used

service.

ding to Clause 15.9lause 4.4.4.

losing at too high and too low oil

il level indicators shall be located at service level (not on the conservator).

aving a high voltage side highest voltage for equipment Um 82.5V the oil level indicator shall be provided with remote indication possibility

d atlevel.

ntly adjustable contacts closinghen the temperature reaches the adjusted value.

ges shalle used for signalling/tripping the others will be used optionally e.g. for control of

he temperature gauges shall be provided with a legible maximum pointer resettable

ter-bus transformers 500 MVA and above and generator step up transformers 75

temauge.

Transformers 75 MVA and above and of cooling type OF, shall if specified, be

provided with one bottom oil temperature gauge.

for tripping.

he relay shall be provided with shut off valves as well as a by pass with no shut offTpossibility in order to facilitate relay exchange when the transformer is in service.

Gas sampling and functional testing shall be possible to carry out when theransformer is int

The relay shall be located in such a way that a person executing testing or

placement work standing on a ladder or on the platform accorrecan not reach within the safety distance according to C

9.2 Oil level indicator

he oil level indicator shall have making contacts cTlevel. The contacts will be used for signalling.

For transformers having a high voltage side highest voltage for equipment Um 82.5V the okFor transformers hk

(potentiometer).

A plate showing the oil level as a function of top oil temperature shall be provideservice

9.3 Temperature gauges (thermometers)

The temperature gauges shall have four independew

The contacts shall be electrically separated. One contact of each of the gaub

cooling.

Tfrom the outside.

InMVA and above shall be provided with two temperature gauges for the top oil

perature. Other transformers shall be provided with one top oil temperatureg



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ding temperature gauges (showing winding hot spot temperature) shall beWinprovided as follows (not applicable to stabilizing and auxiliary windings):

eerature gauge in the warmest winding.

edure gauge in each winding.

ivalent two winding power

windingaverage oil.

hall be provided with Pt100 resistors for remotetemperature indication

he diverter switch oil compartment shall be provided with an overpressure relay

reaching a pressure (an oil flow) as specified by the manufacturer. In case of morean one oil space individual relays for each space shall be provided.

I slay

9 5

case of OF.. cooling oil flow gauges having contacts closing at too low oil flow

case of cooling type ..WF the following is required for each cooler:

w

Water flow gauge and meter with one contact closing for a flow above and below

oil out of the coolerng at a minimum pressure specified by the manufacturer

Two winding transformers 16 MVA and above and without OLTC shall bprovided with one temp Two winding transformers 16 MVA and above and with OLTC shall be provid

with one temperat Transformers with three windings or more having equ

16 MVA and above shall be provided one temperature gauge in each winding.

Generator step up transformers 75 MVA and above shall be provided oneadditional winding temperature gauge based upon bottom oil and

All temperature gauges s

In addition to thermometer pockets for the above gauges there shall be one extrathermometer pocket.

9.4 On-load tap-changer overpressure relay

T

(alternatively an oil-flow relay) equipped with an adjustable contact closing when

tht hall be possible to perform a function test of the overpressure relay (oil flow

) without disassembly.re

. Cooling equipment gauges and transmitters

Inshall be provided. Contact closing shall occur also in case of wrong oil flow direction.

In

Oil flow gauge and meter with one contact closing for a flow above and belosettings specified by the manufacturer

settings specified by the manufacturer

Pressure gauge (manometer) for minimum pressure of thewith one contact closi



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ter) for maximum pressure of incoming water with onem pressure specified by the manufacturer

ay be replaced by differential pressure

For each cooler Pt100 transmitters shall be provided for

- water into each cooler

)

ls.

he sensitivity of fast and slow pressure rise shall be settable. There shall also be

ve two fast pressure

se closing contacts and one slow pressure closing contact.

ers) and transformers for HVDC (category D) shall be equipped with an

isture.

eral

pin two

Pressure gauge (manomecontact closing at a maximu

The pressure gauges (manometers) m

gauges (differential manometer) with one contact closing when the pressuredifference between oil and water is falling below a value specified by themanufacturer

The pressure gauge contacts are intended for signalling/tripping

- oil into each cooler- oil out of each cooler

- water out of each cooler

9.6 Sudden pressure monitor

All inter-bus transformers (category B) generator step up transformers (category Cand transformers for HVDC (category D) shall be equipped with two diagonallylocated sudden pressure monitors comprising pressure sensors and control pane

Tprovided 4 20 mA signals for remote pressure indication.

For the control of fire fighting equipment each monitor shall ha

riThe power supply to the monitors shall be 110 V or 220 V dc.

9.7 On-line dissolved gas monitor

Transformers 63 MVA and above, all generator step up transformers (category Ctransformon-line dissolved gas monitor indicating at least a weighted sum of some of thecombustible gases and moisture in the oil.

There shall be at least 4 20 mA signals for remote indication of gases and mo

The power supply to the monitors shall be 110 V or 220 V dc.

10 COOLING EQUIPMENT

10.1 Gen

System (inter bus) transformers 500 MVA and above and generator step uransformers 75 MVA and above shall have the cooling equipment dividedt

groups.



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The two groups shall be electrically separate, have its own protection and control and

or cooling type OF.. all components having circulating oil must withstand an

ut any leakage the oil having a temperature

f

ll as

the normal case the top oil thermometer will control the coolers. Spare terminaler type of cooling control such as a current relay for

urrent control or a breaker auxiliary contact shall be provided.

It shall be possible to control the oil pumps by an auxiliary contact of thetransformer breaker.

If not ot e co uipment p supply shall be taken from theauxiliary pplic

The ac p wer supply shall be n accorFrnkoppling av kraftkllo

he control shall normally h le for operation mode

be labelled:

be supplied through separate cables.

F

internal overpressure of 0.3 MPa(e) withoof 90 C.

Water cooler tubes etc (cooling type ..WF) shall withstand an internal overpressure o.5 MPa(e).0

Water coolers shall be of double wall/tube design with leakage detection.

The manufacturer shall if requested take part in the design of the site as to coolerlocation and thereby also guarantee that the necessary cooling air will be suppliedccording to clause 3.2.a

In case of separately mounted coolers the necessary cabling and piping as wessembly shall be included in the supply.a

10.2 Cooler control equipment

Inblocks for connection of anothc

herwise stated thinding when a

oling eq owerw able.

o arranged i dance AFS 1993:10, Cl 1.6.3ources).r (Disconnection of power s

T ave three switches with a handselection. Two for the fan groups and one for the pumps.

he switches shallT

Fan switches FRN (off)

TILL (on)VAKT t2 (gauge t2)VAKT t3 (gauge t3)

Pump switches FRN (off)TILL (on)VAKT t1 (gauge t1)HK (breaker auxiliary contact)

temperature setting t1

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In case of sub division of the cooling equipment the number of switches will be amultiple of three.

Each motor shall have its own motor protective switch having both manual and

he motor protective switch shall have at least one auxiliary contact which is closedwitch

tion.

by a circuit breaker and be providedith voltage supervision. Provisions for disconnection in case of fire or risk of fire

equipment power consumption higher than 20 kW half theumber of fans must be delayed in order to limit the total starting current.

s with an auxiliary winding feeding the cooling equipment theanufacturer shall dimension main and group circuit breakers as well as feedercables taking into consideration that these can not cause any undesired trippings at a

multaneous start of all pump and fan motors. This might be the case after anoutage when the mo all the

mperature gauges have their contacts closed.

For transformers without an auxiliary winding or in case of coolers fed from thepurchasers local power supply the manufacturer shall state the maximum value andduration of the total starting current at simultaneous start of all motors as above.

Taking the selectivity into account information shall also be given on which size and

type is applicable for the main circuit breaker through which the complete coolingequipment is fed.

The principal cooling equipment circuit is given in the principal cooling circuitdiagram below.

automatic operation.

Twhen the switch is open. This contact will be used for signalling at protective stripping.

The motor protective switches must not be provided with under-voltage protecEach motor protection and each contactor (auxiliary relay) shall be provided with itsown miniature circuit breaker (MCB).

The complete control circuit shall be protectedwshall be provided.

Staggered switching may become necessary if found advantageous from thedimensioning point of view.

In case of coolingn

For transformerm

sitors have stopped and the voltage returns and

te



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Figure 10.2: Principal cooling circuit diagram



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11 CONTROL EQUIPMENT DESIGN

design

ansformer terminals shall always be located in a separate cubicle.

edance

l equipment supervisory equipment may be connected in

r vibrations.

ormally be

1.2 Ventilation, heating and lightingn for insects

ripping into the boxes or the cubicles a dripping protection or ad roo ll be provided.

p-changer drive and for the cooling equipmentll be provid and an earthed 230 urrent

rcuit breaker event condensation s

ich requires extra heating to secure itstion at 4 the heatermostat. A provided to give an alarm before theperature d it of safe equipme

all be provided a possibility to feed the heating and lighting in the on load tapger moto net from the station local power supply.

rmal insulation, if provided, shall be of incombustible material.

Heaters shall be protected against unintentional contact.

11.1 General

The control equipment shall be assembled functionally and be subdivided as follows:

- Supervisory equipment- On-load tap-changer motor drive

Cooling equipment-- Current transformers

urrent trCt shall be possible to arrange separate cubicles for the connection of an impI

protection to the auxiliary winding (matching transformer cubicle) and forconnections to the bushing capacitive taps.

n case of small scale controIthe on load tap changer motor drive.

The control equipment shall be designed and assembled to withstand occurringransformet

oxes and cubicles shall be located for easy access. Cables shall nB

connected from below why the underside shall be at least 600 mm above the erectionplane.

1Boxes and cubicles shall have draining and ventilation. As protectioopenings shall be provided with e.g. nets having a mesh size of about 1 mm.

o prevent water dTprotrude f shaBoxes and cubicles for the on-load tasha ed with lighting V socket with a residual cci . A heater to pr hall also be provided.

Boxes or cubicles contaiunc

ning equipment whf 0C ambient temperature

shall beshall be controlled by a

ther n extra thermostate limtem rops below th nt function.

It shchan r drive and control cabi

The



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11.3 Term

3.1 General

ubicles shrminal blocks.

Terminal blocks shall be suitable for the connection of conductors having a crossction of 1 - 10 mm.

l bloc r internal circuits are to be selec the manufacturer.

cables com outside shall be connected to the one side of the terminale other one. Maximum two conductors may be

nected to o

e terminal blocks shall be located for easy access. For the connection of incomingductors m ong the complete terminal row shall be

vided.

e terminal b ithin each group.

omponents shall be provided with individual markings for easy identification incircuit diag

3.2 Disposition of terminal groups in the control cabinet

main cabi ks should be functio ally grouped like the followingple dispos ion

inalup

otes

inal blocks

11.

All c all have the necessary number of 8 mm wide slide link type disconnectte

se

Terminal blocks for the motor power supply shall have a size governed by itspurpose.

Termina ks fo ted by

All ing from thegroups and all the internal cables to thcon ne terminal.

Thcon inimum 100 mm free space alpro

Th lock labelling shall begin on 1 w

All cthe ram.

11.

The net terminal bloc nsam it

Termgro

Use N

X1|X10

Power supply andAuxiliary supply

ower supply to have lowernumbers than auxiliary powerIncoming feeder to have lower

ing.

P

number than outgoX11|X50

Pumps, fansFlow indicators, manometersCooler circuit faults

Pumps to have lower numbersthan fans. Signalling andindication in group X50

X51|X53

OLTC gauges

X54 Gas and oil actuated relayX55X56

Oil level indicator

X57 Remote cooler control E.g. transformer breaker



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X|X

this shall be connected to this group61 Temperature transmitter If supply from current transformer

70X|

91 Gauges for oil-SF6 bushings

X99Table 11.1: Control cabinet terminal blocks

3.3 Disposition of terminal groups in the OLTC motor drive

OLTC ca l blocks should be functionally grouped like the followingple dispos

inal

11.

The binet terminasam ition

Termgroup

Use Notes

X1 Power supply

X2 Auxiliary power supply Heating, lighting, excluding tapposition indication

X3 perating circuits Including operating voltageOX4 gnalling circuitsSiX5 osition indicator, potentiometerX6

P

X7 Position indicationX8|X11

Position switch of type break beforeMake

X12

5

osition switch of type make beforereak|

X1

PB

X16 Follower switch, for parallel controlX17 Follower contactX20

21End limit switches

XX22 Gauges in main control cabinetX26|X30

Spare

X51|X53

OLTC gauges

Table 11.2: OLTC motor drive terminal blocks



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11.3.4 Disposition of terminal groups in the current transformer cubicle

11.3.4.1 DispositionThe terminal blocks shall be grouped as follows:

Terminalgroup

Us

e

X11 Core No. 1 for all three phases for the highest voltageX No. 2 for all three phases for the highest voltage12 CoreX13 Core No. 3 ...X14 Core No. 4 ...X15 Core No. 5 ...X21 Core No. 1 for all three phases for the next highest voltageX22 Core No. 2 ...X23 Core No. 3 ...X24 Core No. 4 ...

X25 Core No. 5 ...X31 Core No. 1 ............X for the highest voltage101 Core No. 1 in the neutralX102 Core No. 2 "-X201 Core No. 1 in the neutral for the next highest voltageX202 Core N

TR_1_10E

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