High and extra high voltage cables with synthetic …

1 H i g h a n d e x t r a h i g h v o l t a g e c a b l e sw i t h s y n t h e t i c i n s u l a t i o nG l o b a l e x p e r t i n c a b l e s a n d c a b l i n g s y s t e m s S u m m a r y The evolution of HV and EHV cables with synthetic insulation 5 An outline history of developments 6 Project engineering for HV cable links 7 Examples of the range of HV and EHV cables with synthetic insulation 8 Production tools 9 420 kV cable technology 10 Checks and tests 11 References 12 Accessories 13 Services 15 Introduction 4H i g h a n d e x t r a h i g h v o l t a g e c a b l e sNexans Switzerland supplies high and very high voltage power cables and accessories, optical fiber cables , optical wave-guide and special cables for the international Switzerland has three production centres: the Breitenbach site the Cortaillod site the Cossonay site.

2 4I n t r o d u c t i o nNexans Switzerland is Switzerland s foremost cable maker and manufactures, distributes, fits and installs a compre- hensive range of products for underground, submarine and aerial installations: high , medium and low voltage power cables copper or optical fiber telecommunications cables special cables for many applications power and telecom accessories connection services range from the supply of cables to the implementation of complex turnkey products, including development, engineering, construction work, system technology, laying, installa-tion and project o s i t i o n o f N e x a n s S w i t z e r l a n d T h e e v o l u t i o n o f H V a n d E H V c a b l e s w i t h s y n t h e t i c i n s u l a t i o nT h e C a b l e saluminium sheathcomposite sheathThe greater demand for energy requires the implementation of installations designed to support increas-ingly higher voltage and power is why Nexans Switzerland Ltd has devel-oped cables with synthetic (or dry)

3 Insulation for voltages up to 420 kV and cross- sections that can be larger than 2000 o n d u c t o r sAt high gradients, synthetic insulation is sensitive to the presence of moisture. It is therefore essential to avoid any contact with water or steam during fabrication processes and also during line cross-linking operation must be carried out in the absence of humidity, either on a catenary line in an inert atmosphere, or on a horizon-tal line (MDCV process).For all cables , the external protection is provided by a polyethylene sheath. Over this insulation, the applica-tion of a waterproof metallic sheath, which also acts as a screen, is generally required. I n s u l a t i o nHigher service gradients require better insulation materials should be perfectly clean this is particularly important, as their long-term perfor-mance can be considerably affected, even by micro- impurities.

4 Pr ecautions to ensure cleanliness should be taken both during the production of raw materials and throughout the entire cable fabrication h e a t h sFor conductor cross-sections larger than 1000 mm2, seg-mented conductors must be produced to reduce consider-ably their resistance to alter-nating current by reducing the skin sheath can be made of unwelded extruded aluminum or lead, or of welded or glued copper or aluminum. Nexans Switzerland Ltd uses all these techniques with complete mastery. A n o u t l i n e h i s t o r y o f d e v e l o p m e n t sD e v e l o p m e n t s f r o m 19 7 3 t o t h e p r e s e n t d a ySince the introduction of cross-linkable synthetic insulation, production and control techniques have gone through a whole series of development steps. 1973 1974 1976 1977 1978 1983 1986 1987 1989 1991 1996 1998 2006 Implementation of a cross-linking catenary line Delivery of the first HV cables with dry insulationIntroduction of the triple- head extrusion process Delivery of the first 150 kV extruded insulation cableModification of the catenary line for nitrogen cross-linking Delivery of the first 220 kV cable with XLPE insulation Construction and start-up of a laboratory for measuring partial discharges up to 480 kV Production of the first XLPE cable 220 kV with a cross-section of 2500 mm2 Production of the first 275 kV cable with XLPE insulation Implementation of a 2nd cross-linking line for large conductor cross-sections and thick layers of insulation Production of the first 400 kV cable with XLPE insulation Delivery of the first 400 kV cable with XLPE

5 Insulation abroadDelivery of the first 400 kV cable with XLPE insulation in Switzerland P r o j e c t e n g i n e e r i n g f o r H V c a b l e l i n k s D e v e l o p m e n t p l a n territorial planning increased demand connection of heavy users network plan network calculation power flow determination customerCause and nature of operationsEffectsIntervening partiesP r e - s t u d y p l a n decision to reinforce network preliminary feasibility study pilot study choice of connection type : underground, overhead or mixed technical solutions customer NexansS t u d y Impact study collaboration with other departments : engineering offices, industrial departments, etc. notice to municipal authorities and landowners choice of connection type : underground, overhead or mixed drawing up of specifications customer NexansP r o j e c t choice of definitive run definition of laying parameters measurement of line length preparation of contractor s file customer NexansO f f e r s definition of possible cable types or variants calculation of the cross-section according to voltage , power and civil engineering parameters distribution of partial lengths grounding system preparation of requests for offers and contract tenders for materials and contractors cost of civil engineering work cost of installation and set-up.

6 Schedule and details customer NexansAuthorizations file for the authorities concerned handling of possible objections building authorization customer inspectors Nexans E x a m p l e s o f t h e r a n g e o f H V a n d E H V c a b l e s w i t h s y n t h e t i c i n s u l a t i o n45 kV EPR insulation 60 kV XLPE insulation 150 kV XLPE insulation 500 mm2220 kV XLPE insulation 2000 mm2400 kV XLPE insulation 800 mm2HV Extrusion line P r o d u c t i o n t o o l sHV laboratory Aluminium press10 extruded cross-linked poly-ethylene (XLPE) insulation cables which, with the progress of the techniques used in the manufacturing of basic materials and above all for installation, have achieved the relia- bility level required for use in extra high voltage (EHV) 2 0 k V c a b l e t e c h n o l o g yFor 420 kV cables , there are currently two alternatives to traditional fluid oil impreg-nated paper insulation : cables with PPLP insulation, consisting of three-layer laminated paper and polypropylene tapes, formed into ribbons and impregnated with H V c a b l e s w i t h P P L P a n d X L P E i n s u l a t i o nPPLP insulation, which was introduced at the end of the 0 s, is still limited to cables to be used at a voltage of 400 kV or higher.

7 This is due on the one hand to its price, which is higher than the price of paper, and on the other to the increasingly general-ized use of XLPE insulation for voltages up to 220 kV and 400 InsulationCross-linked polyethylene (XLPE) was introduced in the 0 s. It was initially used for medium voltage cables , but is now used as insulation for extra high voltage cables (EHV). Its use at voltage levels of 400 kV and higher requires, of course, sophisticat-ed state-of-the-art technology. In particular, we should mention :PPLP InsulationFor extra high voltage (400 kV and higher), new types of tapes made of PPLP (Poly Propylene Laminated Paper) are used. They have the advantage of combin-ing the traditional applica-tion technology used for impregnated paper cables with the excellent electrical and dielectric properties of synthetic insulators. PPLP is a three-layer insulation consist-ing of a polypropylene (PP) sheet laminated between two sheets of paper.

8 PP improves the quality of the insulation, while the sheets of paper ensure the circulation of oil between the layers. Compared with paper insula-tion, PPLP has a higher break-down strength and above all lower dielectric P L P a n d X L P E i n s u l a t i o n the rigorous selection of insulating and semi-con-ducting materials, which must be of a very high purity level, the checking of filtering during application, three-layer extrusion (inter-nal semi-conductor, insula-tion and external semi-con-ductor) using a single tool, the obtention of perfectly smooth insulation semi-con-ductor interfaces, protection of the insulation against the penetration of moisture, stringent electrical tests to detect any connection projects at 420 kV, exhaustive tests have been successfully carried out for both XLPE and PPLP cables . The main features of these two types of cables are compared all these tasks, reli-able and fast measurement equipment is required.

9 Considerable investments have been made to equip our materials test laborato-ries with the most modern equipment, such as thermal analysis instruments, tensile strength apparatus, optical C h e c k s a n d t e s t sThe materials used in the con-struction of EHV cables are subjected to very stringent quality control checks, both before and after production. Plastics, metals and tapes all undergo electrical resistance tests and measurements of their dielectric or mechanical r o m c h e c k s o n m a t e r i a l s ..After-laying teststo check the quality of assembly of accessories after installation and to simulate cable operation and rapidly provide information on cable efficiency after prolonged periods of ageing teststo simulate working life and to provide information within a short time frame on their behavior in long-term teststo highlight any degradation phenomena in the line in ser-vice and to provide informa-tion on the residual cable quality of high voltage cable links is highly depen-dent on the rigorous nature of the tests carried out on the cables and their accessories.

10 The more stringent these tests are, the lower is the risk of failure during operation. The principal tests are as follows :Routine teststo evaluate production teststo validate a type of construction, for either cables or testsundertaken in the case of major design .. t o e l e c t r i c a l t e s t smicroscopes, infra-red spec-trometer, chromatograph, among exacting checks enable us to reduce to a minimum the presence of undesirable matter and to guarantee the quality of our e f e r e n c e sP r e s t i g i o u s p r o j e c t s1990 The first 420 kV cable was installed in Switzerland with XLPE insulation connected to the network at the "Bassecourt" substation of the Bernese Electricity substation was connected to Laufenburg and France by 0 kV overhead lines. The copper conductor cross-section was 1200 Various installations of desalination plants were set up along the coast of cer-tain Arab countries.