Power Transformer Manufacturer’s Experience with Transportation

Mishandling

Weidmann Diagnostic Solutions 7th Annual Conference

Enrique Betancourt

Carlos Hernández

New Orleans, LA, Sep.15-17.2008

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Manage the total cost of a piece of equipment, considering its entire service life.

Ideal balance:

• Low purchase cost

• Low cost of operating losses

• High reliability

• Easy installation

• Low maintenance effort

• Easy troubleshooting

• Environmental friendly• Biodegradable

• Low CO2

• Low Noise

Life Cycle Management

SPECIFICATION

ENQUIRIES

CONTRACT REVIEW

DESIGN REVIEW

SHIPPING & INSTALLATION

MANUFACTURING

OPERATION AND MAINTENANCE

RECYCLING

SPECIFICATION

ENQUIRIES

CONTRACT REVIEW

DESIGN REVIEW

SHIPPING & INSTALLATION

MANUFACTURING

OPERATION AND MAINTENANCE

RECYCLING

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Selection of transportation method has big influence on power transformers:

• Initial cost (materials, packaging and carrier)

• Delivery cycle

• Maintenance cost

• Reliability

• Insurance cost

Importance of Transportation Process

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Transformer Transportation Map

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Truck or Lowboy:• Lowest mechanical loads• Limited scope, depending on road availability• Higher cost• Slow, but easy follow up• Special trucks required for certain routes• Limited on load weight and size• Frequently exposed to vandalism

Railroad:• High dynamic loads, impact and continuous vibration• Widespread, heavy duty tracks• Cost in the medium range (except when dedicated train)• Open air transport: easy follow up

Transportation Method

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Sea Carrier:• Low impact, though continuous, quasi-static and rotational

loads• Load must be designed for and properly fitted within container• Indirect monitoring of impacts• Highly dependent on schedule control • Must be complemented with other method

Air Carrier:• Moderately heavy accelerations• Limited on size and weight• Very expensive, but fast• Normally approached as emergency measure

Transportation Method

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Railroad Transportation Loads … 40 ton shipment example

Transversal

0

1

2

3

4

5

6

A B C D E

Technology

G´s

Longitudinal

0

2

4

6

8

10

12

A B C D E

Technology

G´s

Vertical

00.5

11.5

22.5

33.5

4

A B C D E

Technology

G´s

Every manufacturer has its own technology framework:

Load Stress Strength Field Exp.

RELIABLE PRODUCT

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Experience with Longitudinal Loads

Example of a Specific Design Solution*

L on g

it ud i

nal I

mp a

c t ( G

)

Shipping weight (t)

3 G

Normaly safe

Damage

Damage probable

Std. Design

DesigndependentNo damage

20 60 2401801200

10

* See Unit’s particular Instruction Book

80

ServiceRecords

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Mechanical design

Design according to spec requirements or manufacturer standards

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Shipment preparation ... Profile Measuring System

Procedure:• Measure dimensions of loaded railcar

• Compare transformer shipping outline to carrier’s clearance file

• Create transformer’s dimensions file

• Forward dimension’s file to carrier’s approval department

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Load Dimensions Measuring System

Objectives:• Minimize the risk of damage• Reduce transit time• Reduce dimensions verification cycle at shipping bay

Spec for the L-kopia System:• Fast (9,600 to 43,200 points/sec per laser unit)• Accurate (down to +/- 4 mm or 1/8 inch)• High resolution (one point every 0.125 – 0.375 degrees)• Measuring range from 0 – 70 meter (0 – 230’)• Scans 360 degrees• 100% eye safe (Laser Class 1)• Operates under most environmental conditions• Lightweight, compact operational full daylight or darkness

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Shipping Profile

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Compare measured dimensions vs. route clearance

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Preparation for shipment

• Perform FRA test

• Disassemble transformer

• Pressurize with Dry Air (3 to 5 PSI)

• Install impact recorders (digital and analog)

• Ship Transformer to destination

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Delivery process

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Transformer receipt, assembly, operation & maintenance

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Transformer reception

• Verify registers of impacr recorder

• Perform Dew Point test

• Inspection for physical damage

• Measure core insulation

• Perform FRA

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Impact recorder reading

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Impact limits

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Railroad Transportation issuesEvents

Cost from shipping issues Days impact on delivery cycle

8 8

65

Humps Bridge Vandalism Trees

85%

15%0% 0%

Humps Bridge Vandalism Trees

103

34

0 2

Humps Bridge Vandalism Trees

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Examples

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• Small bushings added for monitoring of transportation

• Unit arrived with no issues

• Perfect match between traces before and after shipping

• Demonstrated feasibility and reproducibility, for GSU’s and no bumps

Test unit - 160 MVA GSU, 230 kV

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• Multi-unit package• Unit “E” suffered 8g bump, resulting slight change in tertiary FRA

tracesFig 1

E1. Railroad impact - 200 MVA Auto, 230 kV

Y1-Y2

-80

-70

-60

-50

-40

-30

-20

-10

0100,000 1,000,000

01 F02 F04 F06 F05 P05 F

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E1. Railroad impact - 200 MVA Auto, 230 kV

Y2-Y3

-80

-70

-60

-50

-40

-30

-20

-10

0100,000 1,000,000

01 F02 F04 F06 F05 P05 F

• Multi-unit package• Unit “E” suffered 8g bump, resulting slight change in tertiary FRA

tracesFig 2

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E1. Railroad impact - 200 MVA Auto, 230 kV

Y3-Y1

-80

-70

-60

-50

-40

-30

-20

-10

0100,000 1,000,000

01 F02 F04 F06 F05 P05 F

• Multi-unit package• Unit “E” suffered 8g bump, resulting slight change in tertiary FRA

tracesFig 3

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• Unit shipped back to factory, inspected, reassembled and tested• Factory inspection disclosed slight shift on core support and one phase

winding package; no other displacement or damage

• This case showed that FRA could detect minor changes, but yet hard to interpret

FRA seems sensitive and meaningful ... But practical interpretation rules must be developed.

E1. Railroad impact - 200 MVA Auto, 230 kV

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• Multi-unit package• Unit suffered 7g bump, resulting in tie down damage

Fig 1 Fig 2

E2. Railroad impact - 700 MVA Auto, 345 kV

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• Unit shipped back for inspection and repair

• On transportation back unit suffered 17.5g bump

• Factory inspection disclosed slight gap in top and bottom step blocks close to phase C; no other displacement or damage

• Reassembled and tested

• This case showed that the windings are not sensitive to heavy vertical humps, but C&C clamps to tank might fail under high vertical acceleration

Correction of displaced components re-establishes the integrity of the unit

E2. Railroad impact - 700 MVA Auto, 345 kV

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• On transportation suffered 6g bump• Insulation resistance tests presented no deviations• Internal inspection without any deviations

•·No paper, blocks or insulation damaged or out of position•·No leads out of position or loose•·No core lamination sheets bent or out of position•·No loose hardware and no broken nylon bolts•·No foreign material on the bottom of the tank•·No spacers block out of position or loose

No correction required ... field tests and inspection could not be avoided

E3. Truck impact - 45 MVA SUB, 115 kV

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• On transportation suffered 17.5g bump• Insulation resistance tests presented no deviations• Internal inspection without any deviations

•·No paper, blocks or insulation damaged or out of position•·No leads out of position or loose•·No core lamination sheets bent or out of position•·No loose hardware and no broken nylon bolts•·No foreign material on the bottom of the tank•·No spacers block out of position or loose

No correction required ... field tests and inspection could not be avoided

E4. Railroad impact - 72 MVA SUB, 345 kV

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Who is paying?

Examples SummaryPotential($K USD)

Activities

$30 to $50Field testsField inspection

Example 4

Example 1 Field testsInspectionTransportation Factory work

$700

Example 2 Field testsField inspectionTransportationFactory work

$1,100

Example 3 Field testsField inspection

$25 to $40

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Conclusions

• Power transformer transportation is a process that requires highest attention, as it bears impact on reliability, cost and delivery cycle.

• FRA is a powerful tool, that must be paired with good engineering judgement and supplemented with basic tests.

• Transformer specifications should reflect users experience with their own geographic conditions, as a resource to spare costly issues and project delays.

• Research work is desirable to develop more tools for detection and analysis of effects from transportation loads (Dynamic Response models?).

• In our experience, the mechanical design of power transformers should consider pessimistic impact loads for railroad transportation, mainly dependent on transformers shipping weight, as effective control still seems a challenge for many carriers.

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Further Readings

• T.Lundquist, E.Schweiger, M.Silvestre, W.Hoffman, “Transportation Issues of Power Transformers” , IEEE TC Meeting, San Diego, CA, 2004

• Minutes from DOBLE Engineering Conferences (SFRA methodology andexperiences)

• Minutes from WGs “Transportation Issues Guide” and “Frequency Response Analysis Guide”, from IEEE Transformers Committee

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