A.3.6 8th International Conference on Insulated Power Cables A.3.6

A.3.6 8th International Conference on Insulated Power Cables A.3.6

Jicable’11 – 19 – 23 June 2011, Versailles - France

DEVELOPMENT, QUALIFICATION AND EXPERIENCES WITH 500 KV XLPE CABLE SYSTEMS

Johannes KAUMANNS, Andreas WEINLEIN, Gero SCHRÖDER, Südkabel GmbH, Volker STROOT Südkabel GmbH Mannheim (Germany)

[email protected], [email protected], [email protected], [email protected]

ABSTRACT

10 years after the first installation of a 550kV XLPE cable system in China, an advanced system has been developed and qualified. The XLPE cable system consists of a cable with a conductor cross section of 2500mm², one piece silicone rubber joint, plug-in GIS termination, plug-in dry type outdoor termination and compound filled outdoor termination with composite insulator.

Both, the type test and pre-qualification test have been carried out according the IEC62067 requirements Additionally, tests with increased AC and impulse levels has been carried out.

The new cable system has been installed successfully at projects in Sudan, China, Columbia, Russia and other locations.

These experiences demonstrate that 550kV XLPE cable systems are state-of-the-art technology.

KEYWORDS

500 kV XLPE cable system, one piece silicone rubber joint, PD monitoring system, plug-in compact sealing end, PQ test

INTRODUCTION

10 years after the first installation of a 550 kV XLPE cable system in China in the year 2000 [1], an advanced system has been developed and qualified. The above mentioned first 550kV systems were primarily designed for short cable connections inside power plants, but with increasing need for longer cable systems an advanced system became necessary for higher transmission loads and longer cable length for the 500kV voltage level as described in [2].

The new EHV cable system shows an XLPE isolated cable with a conductor cross section of 2500mm² and prefabricated accessories of the newest generation: One piece silicone rubber joints, compact SF6-plug-in sealing ends, plug-in dry type outdoor sealing ends and compound-filled outdoor sealing ends with composite insulators.

The main parameters of the pre-qualified cable system are:

• voltage level Um: 550 kV • conductor cross section (copper / segmental):

2500 mm2 • XLPE insulation thickness of cable: 27 mm

The type test has been carried out according the IEC 62067 [5] requirements for the Umax = 550 kV level. The one year prequalification (PQ) test covers different

installation conditions of the cable (buried installation, pipe installation and clamped installation). Additional PD tests has been carried out during the full test duration and high-level impulse tests with 1675 kV BIL demonstrate the dielectric performance of the cable. All qualification tests have been carried out at the independent testing institute IPH / CESI in Berlin (Germany).

Further tests with a compact plug-in sealing end installed inside the oil immersed transformer cable connection enclosure of a 500 kV transformer were carried out in 2010 in a factory installation Powertech Transformers (Pty) Ltd Pretoria (South Africa). Additional dielectric tests with increased testing parameters (AC and impulse) have been carried out with GIS-terminations at the IEH testing institute in Karlsruhe (Germany)

The new cable system has been installed successfully and went into operation around the world, in North Africa, China, Colombia, Russia (at voltage level 550 kV) and other locations demonstrating the progress and experiences in this voltage level under different installation conditions. These experiences show that 500 kV XLPE cable systems are state-of-the-art XLPE cable technology.

ADVANCED 550 KV XLPE SYSTEM

The qualified XLPE cable show a six segmental copper conductor with a cross section of 2500 mm². The EHV-grade XLPE insulation material shows a thickness of 27mm and was applied by triplex extrusion process together with both semicon layers in a horizontal extrusion line. Figure 1 shows details of the cable design:

Fig. 1: Cable design for type and PQ test

The copper wire screen design is longitudinally watertight and the laminated aluminium foil design delivers a save radial water protection to the cable under all installation conditions. A strong HDPE outer jacket, which is fix bonded to the aluminium foil, provides the mechanical protection of the cable.

The well known compact sealing end of type EHSVS 550 (type F) was taken as SF6 termination. The outside

1 conductor copper, RMS, 6 segments

2 conductor screen

Conductive XLPE-compound

3 insulation XLPE

4 insulation screen

Conductive XLPE-compound

5 bedding swelling tape, semi-conducting

6 wire screen

copper screen wires

7 bedding semi-conducting swelling tape

8 bedding fabric tape, semi-conducting

9 metallic sheath

Co-polymer-laminated aluminium foil

10 outer sheath

HDPE, two outer layers conductive and flame-retardant

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dimensions are according to the actual IEC 62271-209 standard. This plug-in termination provides an absolute dry solution without any liquid or gaseous contents.

If taking into account the needed space below the GIS switchgear during the installation and lifting of the termination during the installation work the cable installation work can be done separately from GIS work.

Fig. 2: 500 kV compact SF6 sealing end

Two type of outdoor sealing ends have been type tested: The well known SF6 filled type with plug-in connection [3] and a compound filled design with prefabricated stress cone (Fig. 3, left). The gas filled type can be pre-mounted and pre tested in the factory and allows a shortened installation time on-side (Fig. 4).

On the other hand the compound filled type shows an SF6 free solution. The heart piece of this type is the pre-fabricated stress cone made from silicone rubber.

Fig. 3 (left): 500 kV compound filled OSE (stress cone)

Fig. 4 (right): 500 kV compact gas filled OSE

The joint type is a one piece pre-molded joint. The main insulation body is made from silicone rubber (SiR) with integrated field control electrodes. An insulation section is integrated in the outer conductive layer of the joint to provide the screen separation when applied as cross bonding joint.

The outer corrosion protection is given by a coffin box filled with an insulation compound. The coffin box made

from glass fiber reinforced epoxy resin provides a good mechanical protection for the joint main insulation body.

A top cover allows an easy installation of a cross bonding cable if needed.

Fig. 5: 500 kV one piece joint

TYPE AND PQ-TEST

The type test set-up consists of the above mentioned XLPE cable, one–piece silicone-rubber joint, compact OSE and compound filled OSE. (See picture below)

Fig. 6: set-up of 500 kV type test

The compact SF6 sealing end of type EHSVS 550 (type F) has been successfully type tested for the 550kV level with the identical cable type since 2004 [3].

Fig. 7 (left): 500 kV type test – entire set-up Fig. 8 (right): 500 kV type test – one piece joint

The testing parameters were chosen according the IEC 62067 standard (e.g. AC testing voltage 580kV, 20 load cycles 95°C – 100°C, 1550kV BIL, 1175kV SIL). The tests have been successfully carried out at IPH testing institute in Berlin /Germany (CESI group).

The one year pre-qualification (PQ) set-up shows additionally two compact SF6 sealing ends of type EHSVS 550 and 100 m cable length of the above mentioned cable. The cable and joint were installed buried (see pictures below). Additionally, one section of the cable has been installed in a pipe.

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Fig. 9: Set-up of 500 kV PQ test

Fig. 10 (left): 500 kV PQ test - cable laying Fig. 11 (right): Back filling of pipe-laying installation

Fig. 12: Compact SF6 sealing ends of type EHSVS550 Fig. 13: One-piece SiR joint SEHDVCB550, buried

In order to monitor all relevant temperatures a total of 24 temperature sensors has been used (see next figure) at both, the dummy circuit and distributed along the cable circuit under test. The following figure gives the total overview of the PQ test arrangement.

2 x Kunststoff-Rohrdi = 200 mm x 2 m

Dummy l = 15 m

Muff$ VMSVS 550

Muff$ SEHDVCB 550

Endv$rschlussEHFVC 550


TrafoTrafo-St$u$rung

V$rsuchsaufbau Südkab$l 1524.2081038Lag$ d$r T$mp$raturm$ßst$ll$n(nicht maßstäblich)Stand 17.03.2009

N

2 x Kunststoff-Rohrdi = 200 mm x 2 m

Dummy l = 15 m

Muff$ VMSVS 550

Muff$ SEHDVCB 550



TrafoTrafo-St$u$rung

V$rsuchsaufbau Südkab$l 1524.2081038Lag$ d$r T$mp$raturm$ßst$ll$n(nicht maßstäblich)Stand 17.03.2009

N

Z$lt H$iztrafos

M4

M2M8

M7

M5

M3

M1

M6

11621/08

11620/08

11614/08

11615/08

11636/08

11637/08

11617/08

11616/08

11609/08

11606/08

11611/08

11612/08

11160/0611159/06

10402/9911164/05

11618/08

11619/08

11639/0811640/0811638/08

11641/08

11470/08

11630/08

11623/08

11610/08

11469/08

11477/08

11631/08

11625/08

11613/08

11471/08

11624/08

11635/08

11622/08

11634/08

11627/08

11628/08

11642/08 11643/08

11632/08 11644/08

11645/08 11626/08

11633/08 11629/08 TS7:MD5

TS7:MD6

TS7:MD2

TS7:MD1

TS7:MD4

TS7:MT9

TS7:MT10

TS7:MT12

TS7:MT11

TS7:MT13

TS7:MT4

TS7:MT3

TS7:MD3

TS7:LD2

TS7:LD1

TS7:MT5

TS7:MT1

TS7:MT15

TS7:MT14

TS7:MT7

TS7:MT6

TS7:MT2

TS7:MT8

fr$i:

ASARX30

T1 T2

T3 T4

ASARX30

T1 T2

T3 T4

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T1 T2

T3 T4

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T1 T2

T3 T4

ASARX30

T1 T2

T3 T4

ASARX30

T1 T2

T3 T4

15B4 17B0 17B8

15B5 17B4 17BC

MT9 MT10

MT11MD3 MT12MD5 MT3

MT1

MT4

MT2

MT13 MT14

MT15MD4 fr$iMD6 MT7

MT5

MT8

MT6

Empfäng$r an Schrank TS7-A7 -A8-A6

MD1LD1

MD2LD2

Dummy Hauptschl$if$ Hauptschl$if$

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

ASATX30

(4)

(4)

17B5

17BC

17B6

17B8

17B217B9

17B3

17BA

17BB

17B7

17B4

17BE

17BD

17BF

17B0 17B1

15B4

15B5

Rittal-Schrank

Anschlußkast$n Polycarbonat

Anschlußsäul$ BEWAG

T17 T18T09 T10T02T01

T19T03 T20T04 T11 T12

T21 T22T13 T14T06T05

T23T07 fr$iT08 T15 T16

T13

T22

T15

T14T16

T17

T18

T20

T21T23

T19

T08

T06 T07

T12

T11

T01T04

T02 T03

T05

T09 T10

Fig. 14: positions of 24 pcs. temperature sensors

The PQ test were running under all whether conditions down to temperatures at –20°C (see picture 15).

Fig. 15: 500 kV PQ test – entire set-up at –20°C

The following figures show the a typical load cycle and the measured temperatures on cable jacket, dummy conductor, dummy jacket, load current, dummy current, and the applied voltage.

Fig. 16: 156th load cycle T on buried cable

Fig. 17: 156th load cycle T on dummy

All accessories were equipped with inductive type PD sensors. Omicron type pick-up sensors were used for regular PD measurements whereas IPEC type sensors were used for a long term monitoring of the PD activities during the PQ test (see pictures below). During the test no PD from the testing objects could be observed.

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Fig. 18 (left): inductive sensors at back-to-back joint Fig. 19 (right): inductive sensor at OSE

After the PQ test has passed 180 load cycles (90°C - 95°C) and 8570 h AC voltage the final impulse tests has been carried out on cable samples. After successful passing the IEC requirements

- BIL test: 1550 kV - SIL test 1175 kV

an increased impulse test with 1675 kV was passed.

Finally, the investigation of all accessories has been performed in terms if any deteriorations were visible (see pictures below). The inspection was without any findings.

Fig. 20 (left): 500 kV PQ test – investigation joint Fig. 21 (right): 500 kV PQ test – investiagation OSE

ADDITIONAL QUALIFICATION TESTS

Beside the required tests according the IEC 62067 standard additional tests have been carried out:

- TESTS OF THE TRANSFORMER SEALING END

The transformer sealing end of type EHTVS 550 shows the identical design to the compact SF6 sealing end. Only the connection interface to the internal transformer link shows an additional HV electrode to shield the connection area.

The plug-in end sealing end was installed head first in a transformer cable box and dielectrically tested (see picture) in an oil immersed environment.

The AC testing voltage was 493kV accompanied by PD measurements. After AC test transient testing voltages according to the BIL and SWIL were applied. The testing voltage was applied by a compact OSE (see picture below) to the set-up.

Fig. 22 (left): Set-up transfromer 550 kV cable system Fig. 23 (right): 550 kV transformer compact SE

- SHORT CIRCUIT CURRENT TESTS:

The contact system of thew compact sealing end was tested by short time withstand current of 63 kA for 3 sec. with 170 kA peak current.

The tests were passed successfully without any recognized effects on the plug-in contact system (see picture 25).

Fig. 24 (left): Set-up three phase 63 kA / 3 sec. Fig. 25 (right): Common plug-in SE contact after test

- ADVANCED DIELECTRIC TESTS

Sample tests with increased testing levels have been carried out with the compact termination system consisting of SF6 sealing end of type EHSVS and compact OSE of type EHFVCS and a 500 kV cable (Fig. 26).

The passed testing levels were: - Lightning impulse voltage: 1675 kV - Switching impulse voltage: 1240 kV - AC testing voltage: 640 kV / 1h

- DIELECTRIC TESTS WITH PORCELAIN INSULATOR

With the requirement to use porcelain type insulators for special applications the compact OSE was tested accordingly (see picture below Fig. 27).

Fig. 26 (left): Sample test with increased voltages Fig. 27 (right): Tests of 500 kV compact porcelain OSE

- SHORTENED PQ-TEST WITH JOINT IN AIR

Fig. 28: Shortened PQ-test of outdoor installed joint

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In order to verify installation in air of the joint 104 load cycles at 500kV, (approx. 5000 h voltage) were applied to the one-piece silicone-rubber joint (see picture above) of type SEHDV550. The joint passed the test and the final investigation gave no hint for any deteriorations.

ON-SITE INSTALLATIONS (EXAMPLES)

The new cable system has been installed successfully and went into operation around the world, in North Africa, China, Colombia, Russia (all for voltage level 500 kV) and other locations demonstrating the progress and experiences in this voltage level under various installation conditions. The next pictures show some relevant references:

- 500 kV transformer connection to GIB

In this application the cable is installed headfirst to the transformers cable box:

Fig. 29: 15 pcs. 500 kV compact transformer SE

- Connection to GIB:

A typical vertical installation of the compact SF6 sealing end is shown in Fig. 30:

Fig. 30: GIB-compact SF6-plug-in SE

- typical joint installation:

The joint installation requires a concrete bottom for installation the needed cable clamping beside the joint to take the mechanical forces from the cable away from the joint.

Fig. 31: Installed one piece joint SEHDVCB

- porcelain insulators with compact OSE

For special dry climate pollution conditions customers require porcelain insulators.

Fig. 32: EHV compact OSE with plug-in technology and porcelain insulators

For cold climate conditions below –30°C a special heating system has been developed to enable low temperature operation of the compact OSE (Fig. 33).

Fig. 33: 500 kV compact OSE with external heating for lower temperatures

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- typical compact OSE installation

The pre-fabricated insulator part allows an short time installation work on-site [3] as it can be pre- tested and fully pre-assembled shipped to the installation site. The installation work can be widely reduced to the installation of the plug-in part only.

Fig. 34: 500 kV compact OSE with plug in technique in Colombia

A new mobile and compact resonance testing system has been developed to carry out commissioning tests with increased AC voltages even at remote locations (Fig. 35, [4]).

Fig. 35: 500 kV AC on-site test

ACTUAL CHALLENGES

The actual challenge for the new cable system is a huge 500kV project Skolkovo in Moscow/Russia: The delivery consists of 70km XLPE cable with a conductor cross section of 2500mm² showing oxidised wires for reduced skin effect losses. A total of 180 buried joints (cross bonded type SEHDVCB 550) and 38 compact OSE of type EHFVS 550 with plug in technology have to be installed.

Order intake was early 2011 and commissioning is planned for 2011/2012.

CONCLUSIONS

An advanced 500kV XLPE cable system with pre-fabricated accessories and plug-in type terminations for conductor cross sections up to 2500 mm² has been developed and qualified. All qualification tests have been carried out according IEC 62067 standard.

Additional qualification tests give evidence for higher dielectric withstand, short circuit current withstand and application under various installation conditions.

This system has been successfully installed around the world at several projects for the 500kV level and demonstrate the state of the art technology of 500 kV XLPE cable systems.

REFERENCES

[1] staff report “First 525kV XLPE extra high voltage cables destined for Dachaoshan”, Modern Power Systems, December 2000, pp 39-41

[2] S. Sadler, S. Sutton, H. Memmer, J. Kaumanns “1600MVA Electrical Power Transmission with an EHV-XLPE Cable in the Underground of London”, Proceedings CIGRÈ 2004, no. B1-108, International Council on Large Electrical Systems (CIGRÈ), Paris, 2004

[3] J. Kaumanns, G. Schröder, A. Weinlein, V. Stroot, J. Lehnhäuser: 400 KV XLPE-Insulated cable systems with dry plug-in outdoor terminations, Jicable’07, paper A.1.2

[4] A. Weinlein, G. Schröder, H. Geyer, 2011, On-site testing with compact a.c. test-system at the first 500 kV XLPE cable project in South America, Jicable’11, paper C.4.1

[5] IEC 62067 Ed.1.1 2006-03, Power cables with extruded insulation and their accessories for rated voltages above 150 kV (Um = 170 kV) up to 500 kV (Um = 550 kV) - Test methods and requirements

GLOSSARY

AC Alternating Current (E)HV (Extra) High Voltage GIB Gas Insulated Bushing GIS Gas Insulated Switchgear HFCT High Frequency Current Transformer (O)SE (Outdoor) Sealing End PD Partial Discharge(s) PQ Prequalification XLPE Cross-Linked Polyethylene

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A.3.6 8th International Conference on Insulated Power Cables A.3.6