© ABB Group July 10, 2009 | Slide 1

Danijela Palmgren, SLOKO Cigre, Kranjska Gora, May 2009

The Experience of using Distributed Temperature Sensing (DTS) in XLPE Power Cables

© ABB Group July 10, 2009 | Slide 2

Content

System description

Measurements

Calculations

Summary

© ABB Group July 10, 2009 | Slide 3

System description

Al-conductor

Conductor screen

XLPE Insulation

Insulation screen

Copper wire screen with 2 integrated FIMT’s

Al-laminate

PE-Oversheath

Two 132 kV cable circuits in parallel

Approx. 2.6 km cable route

Fibre in Metallic Tube (FIMT) integrated into the copper wire screen

Each FIMT contains multimode fibres

External fibre optic cable (FOC) attached to the power cable for additional temperature control

DTS system (DTS 800 M8)

Temperature measurements on two independent loops

© ABB Group July 10, 2009 | Slide 4

System description

© ABB Group July 10, 2009 | Slide 5

Content

System description

Measurements

Calculations

Summary

© ABB Group July 10, 2009 | Slide 6

Soil temperature

0

2

4

6

8

10

12

2008

-11-01

2008

-11-03

2008

-11-05

2008

-11-07

2008

-11-09

2008

-11-11

2008

-11-13

2008

-11-15

2008

-11-17

2008

-11-19

2008

-11-21

2008

-11-23

2008

-11-25

2008

-11-27

2008

-11-29

2008

-12-01

2008

-12-03

2008

-12-05

2008

-12-07

2008

-12-09

2008

-12-11

2008

-12-13

Soil

Tem

pera

ture

['C

]

1m depth 2m depth 3m depth

© ABB Group July 10, 2009 | Slide 7

Load current

0

200

400

600

800

1000

1200

1 4963

Cur

rent

[A]

w. 46w. 45 w. 47 w. 48 w. 49 w. 50

© ABB Group July 10, 2009 | Slide 8

Channel 1 (FIMT) versus Channel 2 (FOC)

Both the FIMT and the external optical cable give a good reflection of the cyclic loading and the general temperature trend

But with the external optical cable the response to load variations is somewhat delayed and the accuracy of the temperature measurent is somewhat lower

0

10

20

30

40

50

60

1 25 49 73 97 121 145 169 193 217 241 265 289 313 337 361 385 409 433

Scre

en T

empe

ratu

re ['

C]

0

200

400

600

800

1000

1200

Cur

rent

[A]

FIMT External FO Current2008-11-17 2008-11-20 2008-11-23 2008-11-26 2008-11-29 2008-12-02 2008-12-05

© ABB Group July 10, 2009 | Slide 9

Channel 1 (FIMT) versus Channel 2 (FOC) (con’t)

Temperature differences between Channel 1 and Channel 2 are:

Few degrees for sections with direct buried cables

Up to 15 ’C for cables in PVC ducts

Up to 20 ’C for cables in steel pipes

0

10

20

30

40

50

60

70

1 115 229 343 457 571 685 799 913 1027 1141 1255 1369 1483 1597 1711 1825 1939 2053 2167 2281 2395 2509 2623 2737 2851 2965

Fibre length [m]

Scre

en T

empe

ratu

re ['

C]

Ch 1 2008-12-12 00:10:32 Ch2 2008-12-11 23:56:20

Duct

Duct

Duct

Steel Pipe

© ABB Group July 10, 2009 | Slide 10

Content

System description

Measurements

Calculations

Summary

© ABB Group July 10, 2009 | Slide 11

Input data for the calculations

Detailed calculations were performed for the period between 01-12-2008 and 11-12-2008

Calculations were performed according to Electra 87

Calculations performed for the sections without other heat sources in the vicinity

Soil temperature and load current based on the performed measurements

Soil thermal resistivity initially assumed to be 1 Km/W, but the calculations indicated a much lower value, i.e. 0.55 Km/W

The calculations were performed for:

Direct buried cables (49 % of the route)

Cables installed in PVC ducts (47 % of the route)

© ABB Group July 10, 2009 | Slide 12

Calculation results – Direct buried cables

0

5

10

15

20

25

30

35

40

1 49 97 145 193 241 289 337 385 433 481 529

Scre

en T

empe

ratu

re ['

C]

DTS Calculation

2008-12-01 2008-12-02 2008-12-03 2008-12-04 2008-12-05 2008-12-06 2008-12-07 2008-12-08 2008-12-09 2008-12-10 2008-12-11

© ABB Group July 10, 2009 | Slide 13

Calculation results – Cables in air filled PVC ducts

0

10

20

30

40

50

60

1 49 97 145 193 241 289 337 385 433 481 529

Scre

en T

empe

ratu

re ['

C]

DTS Calculation

2008-12-01 2008-12-02 2008-12-03 2008-12-04 2008-12-05 2008-12-06 2008-12-07 2008-12-08 2008-12-09 2008-12-10 2008-12-11

© ABB Group July 10, 2009 | Slide 14

Calculation results – Cables in water filled PVC ducts

0

5

10

15

20

25

30

35

40

45

1 49 97 145 193 241 289 337 385 433 481 529

Scre

en T

empe

ratu

re ['

C]

DTS Calculation

2008-12-01 2008-12-02 2008-12-03 2008-12-04 2008-12-05 2008-12-06 2008-12-07 2008-12-08 2008-12-09 2008-12-10 2008-12-11

© ABB Group July 10, 2009 | Slide 15

Content

System description

Measurements

Calculations

Summary

© ABB Group July 10, 2009 | Slide 16

Summary

FIMT

Quick response

Satisfactory reflection of the load changes and the cyclic load behavior

Risk for damage or increased attenuation during power cable manufacturing

Increased manufacturing cost

The maximum length limited by the power cable drum length (might mean additional joints)

Once installed not influenced by the cable surrounding / installation conditions

Reparation / replacement of fibres not possible (without disrupting the power cable)

External fibre optic cable

Delayed response

The load changes and the cyclic load behavior are smoothened but the general temperature trend is

satisfactory. Better attenuation since not affected by the power cable

manufacturing process

Low cost/risk approach

Lower losses due to jointing since longer lengths (fewer joint) can be used

Greatly influenced by the cable surrounding (for example not a good solution for cables in air) and installation conditions (such as duct and steel pipes)

Reparation / replacement of the fibre optic cable does not disrupt the power cable

© ABB Group July 10, 2009 | Slide 17