A1.1 Worldwide experiences and challenges with EHV XLPE ... · A1.1 Worldwide experiences and challenges with EHV XLPE cable projects 330 kV to 500 kV ... circuit positive and zero

• Jicable’15,21‐ 25June 2015‐ Versailles‐ France• Jicable’15,21‐ 25June 2015‐ Versailles‐ France

Cable Systems, Cables and Accessories

A1.1 Worldwide experiences and challenges with EHV XLPE cable projects 330 kV to 500 kV

22th June 2015

Andreas WeinleinUlrich Peters, Uwe Laage, Horst Memmer

Südkabel GmbH, Mannheim (Germany)[email protected], [email protected], [email protected], [email protected]

• Jicable’15,21‐ 25June 2015‐ Versailles‐ France• Jicable’15,21‐ 25June 2015‐ Versailles‐ France © 22.06.2015 - Andreas Weinlein - Slide 2

Topic


Content of Presentation

Introduction

500 kV Moscow project

400 kV London project

Advanced calculations and tests

Conclusion


Introduction


experience of more than 1,300 kmunderground XLPE cables

more than 2,650 accessories (almost 1,700 joints)

operation voltages 330 - 500 kV

period of 20 years

technical solutions & concepts for development, manufacture, assembly, testing & operation are largely confirmed by the manufacturer

special highlight of the EHV cable technology: one of the longest500 kV cable systems installed in Moscow (Russia) - Skolkovo project -completed in May 2012

second highlight: replacement of fluid filled buried 275 kV cable circuits in the city of London (UK) by 400 XLPE systems known as the London Power Tunnel Project - the first stage commissioned in March 2015


Introduction


advanced tests: mechanical load test of buried joints

short-circuit current test on connections of longitudinalwelded aluminium sheath

flexible cleat evaluation under cable sealing ends

heating concept of accessories down to -45 °C

high reliability, reduced repair times & decreasing cable and accessory prices make the EHV XLPE cable system competitive with overhead lines, especially in difficult terrain or environment, urban areas, industrial plants & with high land prices

in addition to the major projects with large system lengths in metropolises, cable projects are found in the most remote regions of the world, very often connections within cavern hydropower plants between main transformer and switchgear

very high wealth of experience in design, grounding concepts, transportation, laying and fixation concepts is required for such projects




infrastructure project to establish the Skolkovo Innovation Center

replacement of 500 kV double system overhead transmission line

customer: FSK-Meszentra (Russian National Grid Company)

70 km 500 kV XLPE cable

system length ca. 11 km (double system)

individual lengths between 400 - 600 m

138 joints, 12 outdoor sealing ends

project time: 17 months

dry plug-in sealing end installed ingas filled outdoor bushing

adapted to temperatureconditions < -30°C




cable arrangement in trefoil formation, buried

buried joints in joint pits

one piece SiR type joint

cross bonded system

conductor size: 2500 mm²

insulation thickness: 27.5 mm

outer diameter: 150 mm

laminated sheath / weight: 39 kg/m




commissioning in May 2012 /17 months after order intake

on-site test set-up with 5 reactors

test voltage: 320 kV AC @ 26.5 Hz

test current: 129 A

test power: approx. 42 MVA

offline PD measurement by inductive sensors at sealing ends

additional online PD measurementby inductivesensors at alljoints / 6 unitssynchronous




currently a number of 275 kV fluid filled buried cable circuits by National Grid (UK) to provide electrical power to the city of London

nearing the end of their service life are to be replaced

new 400 kV cable circuit connections installed in tunnels St Johns Wood - Highbury – Hackney

Willesden - Kensal Green - St Johns Wood

Kensal Green - Wimbledon




four of ten 400 kV cable circuits between St Johns Wood - Kensal Green - Willesden already installed and commissioned in March 2015

double cable system each tunnel

one section 4 m tunnel to accommodate in addition to the two 400 kV circuits another four 132 kV cable circuits

in total about 32 km of cable tunnel is built

depth between30 - 60 m in theunderground of theCity of London

accommodate nearly200 km of 400 kVXLPE cables




round segmental conductor of oxidised copper wires (2500 mm²)

central plastic core

ks-factor confirmed by routinemeasurements < 0.35

insulation thickness: 25 mm

longitudinal welded aluminiumsheath of 1.5 mm

outer PE consisting of two layers:red HDPE and black flameretardant MDPE identify damages

no conductive layer on the outersheath to avoid earth potentialproblems in the tunnel

no earthing system at all inside tunnel




max. installation length: 1100 m

drums picked up in lots of 18 drumsto store on-site

flexible saddle system in verticalflat formation

axial spacing of 500 mm

spacing between brackets of 8.4 m

> 22,000 saddles

rating in forced ventilated tunnel: 2555 A / 1770 MVA (winter)

2310 A / 1600 MVA (summer)

airflows of 3.5 m/s - 8.0 m/s




186 pcs. sectionalising joints: one piece body made of SiR

field control elements & screen separation integrated in the body

open cross bonding / SVL design inside tunnel with 21 kV surge arrester in delta connection at each joint

60 pcs. GIS plug-in compact sealing ends

completely dry & solid insulation

absolutely maintenance free & no need of any fluid or gas monitoring




commissioning test: 260 kV AC / 1h (stage 1 in March 2015)

voltage supplied via test bushing to GIS CSE

inductive PD measurement with HFCT at each accessory synchronously via with optical fiber interconnected acquisition units

further commissioning tests: cable conductor resistances

circuit positive and zero sequence impedance

verification of cross-bonded sheath system

sheath system contact resistances

SVL operating voltage test

SVL visual inspection andinsulation resistance test




side wall pressure test onEHV cable with longitudinal welded aluminium sheath

short circuit test of sheath connections on EHV cable with longitudinal welded aluminium sheath

mechanical load test of buried joint followed by waterimmersion & heat cycling test




mechanical parameters of cables have increasing impact on the design of fixings & support structures for cables & their accessories

cable is fixed & no expansion is possible cable will exert a longitudinal force (cable thrust), e.g. at sealing ends

cables with a 2500 mm² copper conductor thrust potential in the range of 90 kN

sealing ends usually do not allow high axial forces or axial movement measures to reduce them

alternative to rigidly built bend below sealingends flexible bend cable can extend toand from (recommended for EHV cables)


Conclusions


technical solutions & concepts for development, manufacture, assembly, testing & operation are largely confirmed by the manufacturer

in 2 current huge projects - 500 kV Moscow project & 400 kV London project - with laminated sheath and longitudinal welded aluminium sheath - both with oxidised copper wire conductor - the reliability of the EHV XLPE cable system is shown

in contrast to alternative cable designs with e.g. enamelled wires, the oxidised wires allow jointing of the conductor without special treatment of single wires, accelerating overall jointing, while still gaining from the same ks-factor (AC resistance) improvement

laminate sheath design likewise allows for aresilient and easy handling of the screen on sitefor cable layings and accessory installationscompared to lead or (corrugated) aluminiumsheaths

• Jicable’15,21‐ 25June 2015‐ Versailles‐ France• Jicable’15,21‐ 25June 2015‐ Versailles‐ France


Thank you for your attention

© 22.06.2015 - Andreas Weinlein - [email protected]

Documents

A1.1 Worldwide experiences and challenges with EHV XLPE ... · A1.1 Worldwide experiences and challenges with EHV XLPE cable projects 330 kV to 500 kV ... circuit positive and zero