1.85931!Palmgren

ABB AB High Voltage Cables, Danijela Palmgren, Växjö 23 April, 2013

Armour loss in three-core submarine XLPE cables

© ABB GroupApril 24, 2013 | Slide 1

Content

Introduction to ABB and Cable Design Armour losses in three-core cables:

• Measurement method• Test object• Measurement equipment• Measurement accuracy• Measurement results

Summary

© ABB GroupApril 24, 2013 | Slide 2 ABB


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HVAC Cable Design: Land


Metal sheath Outer sheathBeddingBedding Metal screenConductor Conductorscreen

Insulation Insulationscreen

Bedding

HVAC Cable Design: Submarine Single Core


HVAC Cable Design: Submarine Three-Core


Conductor shield

Insulation

Insulation shield

ConductorMetal sheath

Profiles

Optical fiber

Armour

Outer sheath (Polypropylene yarn)

Inner plastic sheath

Armour loss calculations acc. to IEC 60287

Three-core SL type cables – steel wire armour:

Where:RA the ac resistance of armour at maximum armour temperature (ohm/m)R ac resistance of conductor at maximum operting temperature (ohm/m)Rs resistance of sheath or screen per unit length of cable at its maximum operting temperture (ohm/m)X reactance per unit length of sheath or screen per unit length of cable (ohm/m)c the distance between the axis of a conductor and the cable centre (mm)dA mean diameter of armour (mm)


Armour loss calculations acc. to IEC 60287

The equations for armour loss calculations according to IEC 60287 probably originate from measurements performed 1939 by ERA

The equations are semi-empirical The equation has been derived from measurements performed on several

cables All cables were relatively small. The largest test cable was 1in2 (approx. 689

mm2) All test cables had a common metal sheath The accuracy of the measurement equipment has significantly been improved

since 1939 Having in mind the typical cable design for three-core submarine cables of

today, their ever-increasing size and the improved measurement accuracy the correctness of the equations for calculation of armour loss in three-core cables has been questioned


Armour loss measurement: Measurement method

Three-phase transformer with connection group Dyn11 connected to a symmetrical 400 V network

Transformation performed on the primary side Connection leads between the transformer and the test object were

equal in length, bundled and kept as short as possible The cable cores at the ends of the test object were kept as short as

possible The test object was long, i.e. 75 and 59 m The test object was laid on wooden trestles The cable was heated only during the measurements The measurements were performed at four current steps The measured losses are the total cable losses The armour losses are calculated by subtracting the conductor and

sheath losses from the total cable losses


Armour loss measurement: Three-core cable designs

Rated voltage 115 kVMax. system voltage 123 kV

ConductorType/material solid copperCross-section 240 mm²Diameter 17,5 mm

Insulation systemMaterial 1 semi-conductive PEMaterial 2 XLPEMaterial 3 semi-conductive PE

Metallic sheathType/material lead alloyThickness 2 mmDiameter 56 mm

Inner sheathType/material PEDiameter 60 mm

Optical cable

Cable assembly

BeddingType/material polymeric tapes

ArmouringType Double armourMaterial 1 Galvanized steel (72+84

wires)Material 2 BitumenWire diameter 5 mmDiameter 151 mm

Outer coverMaterial Polypropylene yarn

Complete cableDiameter 159 mm

Rated voltage 132 kVMax. system voltage 145 kV

ConductorType/material compacted aluminiumCross-section 815 mm²Diameter 35 mm

Insulation systemMaterial 1 semi-conductive PEMaterial 2 XLPEMaterial 3 semi-conductive PE

Metallic sheathType/material lead alloyThickness 2 mmDiameter 77 mm

Inner sheathType/material PEDiameter 81 mm

Optical cable

Cable assembly

BeddingType/material polymeric tapes

ArmouringType Single armourMaterial 1 Galvanized steel (64 wires)Material 2 PR/Polyester wire (64 wires)Material 3 BitumenWire diameter 4 mmDiameter 183 mm

Outer coverMaterial Polypropylene yarn

Complete cableDiameter 191 mm


Armour loss measurement: Measurement equipment


Armour loss measurement: Armoured cable


Armour loss measurement: Unarmoured cable


Armour loss measurement: Measurement accuracy

The armour loss for the single layer armour design is calculated according to:

The relative error of the armour loss is:

To improve the accuracy a difference method is chosen:

The armour loss can be calculated as : The error is minimized

Where:

Wm1 Measured cable lossesIc1 Measured conductor currentIs1 Measured sheath currentRc1 Measured conductor resistanceRs1 Measured sheath resistanceWm1 The sum of all errors of the

measured values

Index 0 unarmoured cableIndex 1 armoured cable


Armour loss measurement: Results

Double wire armour design:

Double armour – no armour

Single armour – no armourIc1 [A] 304,9 404,3 600,4 799,0c1 [C] 14,1 13,2 14,7 10,71 [p.u.] 0,0966 0,0985 0,1007 0,10432 [p.u.] 0,0597 0,0675 0,0816 0,0859

Correction to 90 C conductor temperaturec1 [C] 90 90 90 902 [p.u.] 0,0457 0,0515 0,0627 0,0649

Ic2 [A] 303,5 402,6 600,1 789,0c2 [C] 13,3 13,3 16,7 10,61 [p.u.] 0,0992 0,1001 0,0998 0,10762 [p.u.] 0,0655 0,0700 0,0779 0,0712



Armour loss measurement: Results

Single wire armour design:

Single armour – no armour

Ic1 [A] 326,1 431,9 640,7 846,7c1 [C] 16,8 17,0 17,9 15,11 [p.u.] 0,1653 0,1680 0,1739 0,17982 [p.u.] 0,1132 0,1355 0,1609 0,1870



Armour loss measurement: Summary

The test object must be sufficiently long. The measurement must be performed at rated current. Measurements need to be performed on cable with and without armour. The measurement accuracy is increased by means of the difference method. The measurement indicates no difference between single and double armoured

cable. The armour loss calculated according to IEC 60287 is much larger than the

armour loss calculated out of the measured data. The quote between the sheath loss factor for an armoured SL type three-core

cable and the sheath loss factor for an unarmourd SL type cable according to IEC 60287 is 1.5. The measurements for the single wire armour design show a factor between 1.3-1.5, while for the double wire armour design the factor is 1.7-1.9.


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