qualification procedure of hpte insulated cable systems

Prof. Ing. Giovanni MazzantiDept. Electrical, Electronic & Information Engineering “Guglielmo Marconi”

Alma Mater Studiorum - University of Bologna, Italy

Qualification procedure

of HPTE insulated cable

systems

Presentation for the GRIDABLE Project,

14.06.2021

May I introduce myself? (1)

Teacher of High Voltage Engineering & HVDC Technology, Electrical Techn. & PQ

Consultant to TERNA, CESI, e-distribuzione

Member of: IEEE Power and Energy Society (PES), IEEE Dielectrics & ElectricalInsulation Society (DEIS), IEEE DEIS TC on “Smart grids”, IEEE PES Transmission& Distribution Committee (HVDC & FACTS Subcommittee), CIGRÉ, CIGRÉ JWGB4/B1/C4.73, CIGRÉ SC-B.1, CIGRÉ TF-1.84

Co-Editor of the international journal IEEE Transactions on Dielectrics and

Electrical Insulation: Part B – Dielectric Applications

Giovanni Mazzanti, HVDC Cable Systems - Qualification procedure of HPTE insulated cable systems Alma Mater Studiorum - University of Bologna, Italy, Jun. 14th 2021

Coauthor of the book: G.Mazzanti, M.Marzinotto, Extruded

Cables for High Voltage Direct

Current Transmission: Advances

in Research and Development,“IEEE Press Series in PowerEngineering”, Wiley, 2013(

)

May I introduce myself? (2)

Chairman of the IEEE DEIS Technical Committee on “HVDC Cable Systems(cables, joints and terminations)”

, which developed:

IEEE Std. 1732:2017, “Recommended Practice for Space Charge

Measurements in HVDC Extruded Cables for Rated Voltages up to 550 kV”, 1st Standard worldwide on space

charge measurements on HVDC cable systems

IEEE Std. 2862-2020, “Recommended Practice for Partial Discharge

Measurements under AC Voltage with VHF/UHF Sensors during Routine

Tests on Factory and Pre-moulded Joints of HVDC Extruded Cable

Systems up to 800 kV” , 1st

Standard worldwide on PD measurement with VHF/UHF sensors in testsfor HVDC cable systems

Since Jan.1st 2021, IEEE Fellow ( ), withthe citation "for contributions to high voltage direct current cable systems“


SUMMARY

1) The booming growth of HVDC extruded cables

2) Why HPTE?

3) Qualification of HPTE HVDC cable systems

4) Conclusions

4


1) The booming growth of HVDC extruded

cables

2) Why HPTE?


4) Conclusions

5


6

HVDC cable worldwide market

Fig. 1 – Left: total length of HVDC cables installed worldwide (after [2]) and inset with core length of DC-XLPE cables installed

and under construction (after [3]). Right: voltage and power rise of extruded HVDC cable systems (after

https://www.nkt.com/news-press-releases/525-kv-xlpe-dc-cable-systems-a-key-contributor-in-the-green-transformation)

HVDC cable market split between:• oil-paper (lapped) insulation cables: ruled market until late 1990s• More established: top lengths, voltage and power ratings

• extruded (= XLPE) cables: booming growth since late 1990s [1],[2]• Less established as design, construction, installation, O&M, but R&D pushes

them up to >600 kV and >1000 MW [3]


7

Top voltage: 640 kV DC-XLPE cable system [3]


Fig. 2 – Left: transmitted power vs. conductor area and metal for a cable pair. Right: copper (3000 mm2) and

aluminum (2000 mm2) 640 kV cables (after [4])

XLPE insulation advantages vs. oil-paper cables:

• lower costs

• easier (faster, cheaper) jointing

• good environmental compatibility (no oil leakage)

• conductor temperature > MIND cables (50-55°C):o HVDC XLPE conductor temperature = 70°C (Hokkaido & Nemo links 90°C)

XLPE insulation disadvantages vs. oil-paper cables:

• weak points (defects)

• suffers space charges (SC) = X-linking by-products

• suffers polarity reversals

• less service experience

Quest for recyclability: XLPE not fully recyclable8

XLPE vs. oil-paper DC cables: pros & cons

Giovanni Mazzanti, HVDC Cable Systems - Seminar for IBES PhD students - Dept. Electrical, Electronic & Information Engineering Alma Mater Studiorum - University of Bologna, Italy, Jun. 11th 2021

9


Recent developments of XLPE for HVDC Cables [5]


2) Why HPTE?


4) Conclusions

10


HPTE = High Performance Thermoplastic Elastomer [5]

11


12

PP based extruded insulation (= P-laserTM by Prysmian) attractive alternative to DC-XLPE since it is thermoplastic [2],[5],[6]:

• no X-linking o much faster manufacturingo no X-linking by-products

no degassing much less SC

no problems with polarity reversals (PR)

• fully recyclable more environmentally friendly

• higher service temperature: 90°C (70°C for DC-XLPE due to the lower X-linking degree of DC-XLPE vs. AC-XLPE)


HPTE advantages

13


HPTE development [7]

After great experience in MV cables, HPTE extended to:• HVAC: 1000 mm2 Cu, 150 kV, HPTE cable in Italian grid since 2013• HVDC: qualifications at U0=320, 350 and 600 kV-DC, T=90°C, for

both VSC and LCC [6], contracts awarded for A-Nord and SuedOstLink German corridors [8]

14

HPTE HVDC cable systems


Fig. 9 - HPTE cable

[9](from the web)[10]

Table 1 - HPTE

manufacturing [7]

Table 2 - HPTE

performance [7]


2) Why HPTE?


4) Conclusions

15


16

Tests prescribed by TB 496 (1)

TB 496 [11] main tests on HVDC extruded cable systems are:

1) Development tests ≡ during R&D of the cable system

2) Qualification tests ≡ before supplying on commercial basis a type of cable system covered by the TB, in order to

a) prequalification test ≡ demonstrate satisfactory long-term

performance of complete cable system

b) type tests ≡ demonstrate satisfactory performance

characteristics to meet the intended application


17

Tests prescribed by TB 496 (2)

3) routine tests ≡ by manufacturer on each manufactured component

(length of cable or accessory) to check the component meets the specified requirements

4) sample tests ≡ by manufacturer on samples of complete cable or components (cables or accessories) - specified frequency - to verify that finished product meets the specified requirements

5) tests after installation ≡ on site to demonstrate the integrity of the cable system as installed

Focus here on development and qualification tests for their significance on final design of HVDC extruded cable systems


18

Prequalification test (PQT): load cycles

LC LC HL HL ZL LC LC S/IMP

Cycles (Days) 40 40 40 40 120 40 40 S/IMP

Polarity + - + - - + -UP2,O = 1.2 x U0

UP1 = 2.1 x U0*Voltage (xUo) 1.45 1.45 1.45 1.45 1.45 1.45 1.45

Total days 40 80 120 160 280 320 360

Table 3. Duration, polarity and applied voltage magnitude (p.u. of U0) during PQ tests for VSC cable systems

according to TB 496 (S/IMP=Superimposed Impulse Test). * If required (after [11])

Table 4. Duration, polarity and applied voltage magnitude (p.u. of U0) during PQ tests for LCC cable

systems according to TB 496 (S/IMP=Superimposed Impulse Test). * If required (after [11])

LC LC LC+PR HL HL ZL LC LC LC+PR S/IMP

Cycles 30 30 20 40 40 120 30 30 20 S/IMP

Polarity + - +/- + - - + - +/-UP2,O = 1.2 x U0

UP1 = 2.1 x U0*Voltage (xUo) 1.45 1.45 1.25 1.45 1.45 1.45 1.45 1.45 1.25

Total days 30 60 80 120 160 280 310 340 360


19

Table 5. Duration, polarity and applied voltage magnitude (p.u. of U0) during load cycle TT for VSC cable

systems according to TB 496 (LC48=“48 hours” load cycles) (after [11])

Table 6. Duration, polarity and applied voltage magnitude (p.u. of U0) during load cycle TT for LCC

cable systems according to TB 496 (LC48=“48 hours” load cycles) (after [11])

LC LC LC+PR LC48

Cycles 8 8 8 3

Polarity - + +/- +

Voltage (xUo) 1.85 1.85 1.45 1.85

Total days 8 16 24 30

LC LC LC48

Cycles 12 12 3

Polarity - + +

Voltage (xUo) 1.85 1.85 1.85

Total days 12 24 30

Type tests (TT): load cycles


20

U0=320 kV - PQT [5]


Results: fully positive [6]

21

U0=320 kV – TT [6]


Type Test 24-h

load cycles at

UT=1.85×U0=

1.85x320=592 kV

TT LCC and VSC at 320-kV, 90°C on 100 m HPTE 320 kV DC cable 1000 mm2 Cu conductor, 1 premolded joint, 2 composite terminations

Results: fully positive achievement of 320 kV class for VSC and 350 kV for LCC [6]

U0=320 kV - Superimposed Impulses [6]



22

UP2,S=2.31×U0=740 kV

UP2,O=1.31×U0=420 kV

UP1=2.43×U0=780 kV

23


U0=600 kV - TT [6]

UT=1110 kV (!)

Type Test 24-h load cycles at UT=1.85×U0=1.85x600=1110 kV

24


U0=600 kV - TT [6]

UT=1110 kV (!)

LC LC LC48

Cycles 12 12 3

Polarity - + +

Voltage (xUo) 1.85 1.85 1.85

Total days 12 24 30



25

UP2,S=1.85×U0=1100 kV

UP2,O=1.05×U0=630 kV

UP1=1.85×U0=1100 kV

U0=600 kV - Superimposed Impulses [6]

26

Qualification of the 640 kV DC-XLPE cable [3]


Qualified 640 kV underground DC-XLPE cable system

Compared to 525 kV system:o same technology platformo same insulation (XLPE upgraded vs. lower voltages) ≡ robust,

low conductivity ( no thermal runaway)o almost same design of prefabricated joints & terminations

27

PQT load cycles for the 640 kV DC-XLPE cable [3]


Good thermal stability notwithstanding the very high test voltage:

UTP1 = 1.45 × U0= 1.45 × 640 = 928 kV

Maximum temperature still 70°C

HPTE very appealing for its breakthrough properties:• no X-linking

o much faster manufacturing

o no X-linking by-products

no degassing

much less SC

no problems with polarity reversals (PR)

• fully recyclable more environmentally friendly

• higher service temperature: 90°C

DC-XLPE still competitive. Main advantage: more service experience, better assessed mechanical properties

Strong competition between the two for the (still) growing HVDC cable market expected…

Conclusions


References

[1] G. Mazzanti, M. Marzinotto, Extruded Cables for High Voltage Direct Current Transmission: Advances in Research and Development, Power Engineering Series - Wiley-IEEE Press, July 2013, ISBN 9710-1-1110-09666-6.[2] G. Mazzanti, “Editorial”, Special Issue on Worshop on HVDC cables and accessories, IEEE Electrical InsulationMagazine, Vol. 33, No. 4, pp. 4-5, Jul./Aug. 2017.[3] M. Jeroense, P Bergelin, T. Quist, A. Abbasi, H. Rapp, L. Wang, “Fully qualified 640 kV underground extruded DC cable system”, Paper B1-309, pp. 1-11, CIGRÉ Session 2018, Paris, France, 26–31 Aug. 2018.[4] https://www.nkt.com/products-solutions/high-voltage-cable-solutions/innovation/640-kv-extruded-hvdc-cable-systems[5] M. Albertini, A. Bareggi, L. Caimi, L. De Rai, A. Dumont, S. Franchi Bononi, G. Pozzati, P. Boffi, “Development and high temperature qualification of innovative 320 kV DC cable with superiorly stable insulation system”, 9th Jicable’15, paper No. A7.3, pp. 1-6, Versailles, France, 21-25 Jun. 2015[6] A. Bareggi, P. Boffi, S. Chinosi, S. Franchi Bononi, L. Guizzo, G. Lavecchia, M. Marzinotto, G. Mazzanti, G. Pozzati, “Current and future applications of HPTE insulated cables systems”, Paper B1-307, Cigrè Science & Engineering, N. 13, pp. 34-44, Feb. 2019.[7]https://d2wmefcb92kfgk.cloudfront.net/sites/www.voltimum.it/files/fields/attachment_file/brochure_plaser_2020.pdf

[8] https://www.prysmiangroup.com/en/insight/projects/prysmian-group-realising-vital-german-corridor-energy-transition-projects[9] https://www.windpowerengineering.com/prysmian-develops-new-p-laser-600-kv-cable-system-hvdc-power-applications/[10] https://www.aeit.it/aeit/riviste/estrattoEE.pdf[11] Brochure CIGRÉ 496, “Recommendations for testing DC extruded cable systems for power transmission at a rated voltage up to 500 kV”, CIGRE Working Group B1.32, Apr. 2012


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qualification procedure of hpte insulated cable systems

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