Borlink Copolymer insulation. ensuring the reliability of medium voltage distribution cable systems

Transcription

1 Borlink Copolymer insulation ensuring the reliability of medium voltage distribution cable systems

2 About Borealis and Borouge Borealis is a leading provider of innovative solutions in the fields of polyolefins, base chemicals and fertilizers. With headquarters in Vienna, Austria, Borealis currently employs around 6,400 and operates in over 120 countries. It generated EUR 8.1 billion in sales revenue in The International Petroleum Investment Company (IPIC) of Abu Dhabi owns 64% of the company, with the remaining 36% owned by OMV, the leading energy group in the European growth belt. Borealis provides services and products to customers around the world in collaboration with Borouge, a joint venture with the Abu Dhabi National Oil Company (ADNOC). Building on its proprietary Borstar and Borlink technologies and 50 years of experience in polyolefins, Borealis and Borouge support key industries including infrastructure, automotive and advanced packaging. The Borouge 3 plant expansion in Abu Dhabi will be fully operational in Borouge 3 will deliver an additional 2.5 million tonnes of capacity when fully ramped up, bringing the total Borouge capacity to 4.5 million tonnes. Borealis and Borouge will then have approximately 8 million tonnes of polyolefin capacity. Borealis offers a wide range of base chemicals, including melamine, phenol, acetone, ethylene, propylene, butadiene and pygas, servicing a wide range of industries. Together with Borouge the two companies will produce approximately 6 million tonnes of Base Chemicals in Borealis also creates real value for the agricultural industry with a large portfolio of fertilizers. The company distributes approximately 2.1 million tonnes per year. This volume will increase to more than 5 million tonnes by the end of Borealis and Borouge aim to proactively benefit society by taking on real societal challenges and offering real solutions. Both companies are committed to the principles of Responsible Care, an initiative to improve safety performance within the chemical industry, and contribute to solve the world s water and sanitation challenges through product innovation and their Water for the World programme. For more information visit: Borstar is a registered trademark of the Borealis Group. Borlink and Water for the World are trademarks of the Borealis Group.

3 Contents 04 An enhanced performance XLPE solution for MV cables 05 Long-term testing confirms problem-free operation 08 Processing improvements lead to better cost control 09 Advanced semicons improve cable insulation interface 10 Better jacket protection lowers total cable cost 11 Overview of market experience 12 Recommended material system for MV cables with bonded insulation screen 12 Sources of further information 3

4 An enhanced performance XLPE solution for MV cables For both power distributors and their customers the long service life of a cable system is essential to a reliable, cost efficient electricity supply. It was found in the 1970s that an important factor limiting the life of Medium Voltage XLPE cables resulted from the breakdown of cable insulation caused by Water Treeing. Since then a substantial body of research has been dedicated to the development of technical solutions to minimise the effect of treeing and significantly extend the operating quality and lifetime of crosslinked polyethylene (XLPE) cables subject to this phenomenon. Produced using the same dedicated high pressure tubular polyethylene (PE) reactors, these acrylate copolymers possess the same inherent properties of cleanliness and good processing characteristics as the LDPE designed for power cable insulation applications. The copolymer modified XLPE is characterised by its morphology. It has a biphasic blend structure with the LDPE as a matrix and the copolymer as a dispersed phase. Borlink Copolymer is the result of further development and marks the second generation of copolymer modified XLPE. In the search for an XLPE insulation material with improved wet ageing characteristics it was found that a mechanically mixed blend of low density polyethylene (LDPE) and an ethylene-acrylate copolymer gave a significant reduction in the propensity of insulation to degrade under electrical stress in the presence of water. This is best thought of as a polymer Water Tree Retardant XLPE (polymer WTR). Extensive research showed that solutions of this type were found to be particularly effective in cables with a bonded insulation shield construction. These developments resulted in the copolymer modified XLPE. Borlink Copolymer benefits to cable makers: Filling Cleantainer High line speed potential Excellent scorch resistance for long production runs to utilities: Enhanced wet ageing electrical performance passing the most stringent market requirements Long service life Proven track record Improved system reliability Three core Medium Voltage cable 4 Borlink Copolymer insulation

5 Long-term testing confirms problem-free operation Accelerated wet ageing tests of MV cables are generally accepted as a basis for the qualification of materials and cable manufacturing processes. The results obtained from tests correlate well with service experience, which is why they provide good indications of expected cable lifetimes for cables manufactured today. Such tests are particularly useful as the foundation for material selection and assuring customers that their requirements for long-term cable performance will be met. The performance of Borlink Copolymer has been proven by testing, according to accepted industry standards in which cables have been exposed to a wide range of accelerated ageing conditions. Parameter Bow-tie tree cable test DIN VDE Cenelec HD620 Model cable test Cable rating 15 kv 20 kv kv 1.5 mm insulation thickness Samples removed each time 1 x 1 m 5 x 10 m 6 x 10 m 5 x 0.5 m Preconditioning None 90 C/7 days 55 C/500 h 80 C/3 days Water Inside conductor Inside and outside conductor Outside conductor Outside and inside conductor Conductor temperature No conductor heating 50 C 40 ± 5 C 85 C Outside temperature 90 C (8 h on, 16 h off) 50 C 40 ± 5 C 70 C Voltage 4 Uo 3 Uo 9 kv Ageing time 3,000 hours 6, 12, 24 months 12, 24 months 1,000 hours Breakdown test None 5 Uo/5 min + Uo/5 min Country specific step test Ramp, 100 kv/min Requirements U 63 % > 12 Uo U > 9 Uo Minimum 6 values 14 kv/mm 4 values 18 kv/mm 2 values 21 kv/mm Elevated (Germany etc.) 6 values 23 kv/mm 4 values 29 kv/mm 2 values 35 kv/mm Engineering information Table 1: Long-term wet electrical ageing tests 5

6 Cenelec HD 620 Two-year wet ageing tests for type approval of Medium Voltage XLPE cables have been required in Germany since Additionally, samples are taken from annual production and are aged under the same test regime as for production monitoring. Like Germany, countries such as Belgium, the Czech Republic, Slovakia and Hungary have also successfully followed this approach in requiring a production monitoring test. Other countries only require a single type test. Cable samples are subjected to AC breakdown tests after 12 and 24 months of ageing. The 24-month samples are also inspected with regard to Water Tree growth. To pass the test, 6 samples are required to have breakdown strength higher than 23 kv/mm, 4 higher than 29 kv/mm and 2 higher than 35 kv/mm. These requirements must be fulfilled for both the type test and cable production monitoring test. Original VDE test procedure was harmonised with the Unipede test regime under a common Cenelec protocol which has been standard since The test requirements are outlined in Table Figure 1 shows the typical behaviour of Borlink Copolymer compared to classic homopolymer (XLPE). The superiority of the copolymer technology is obvious. Typical values of the residual electrical breakdown strength of the copolymer XLPE in the VDE ageing test of 20 kv cables are in the range of kv/mm, significantly better than classic XLPE. Breakdown stress after [kv/mm] 2 years of ageing Borlink TM Copolymer Classic XLPE Figure 1: Characteristic performance level of MV cables in 2 year ageing tests, the bars represent the maximum and minimum values obtained (20 kv cables) 6 Borlink Copolymer insulation

7 These material improvements have been achieved through optimisation of the level, type and consistency of the acrylate copolymer dispersed phase in the LDPE matrix. Figure 1 highlights the performance from breakdown tests after two years of ageing. The test results show a significant spread in performance for the two insulation families. Cables with Borlink Copolymer insulation typically give 10 kv/mm higher breakdown values after ageing than homopolymer strength. Model cable test Small size, 3-layer cables with 1.5 mm insulation were subjected to 1,000 hours of ageing. The AC breakdown strength before and after ageing was tested and the results are shown in Figure 2. The data from this test shows that the cables made with Borlink Copolymer insulation have a breakdown level, after 1,000 hours, of approximately 65 kv/mm; whilst the classic homopolymer XLPE cables drop to 40 kv/mm under the same conditions. The underlying reason for the significantly better results achieved with Borlink Copolymer cable is that it develops much shorter water trees. Model cable testing Breakdown strength [kv/mm] Eb (t=0) Eb (t=1000h) 0 Borlink TM Copolymer Classic XLPE Figure 2: AC breakdown strength of model cables before and after 1,000 hours of wet ageing 7

8 Processing improvements lead to better cost control Controlling the costs of high quality Medium Voltage cable production is an important attribute for cable manufacturers. Experience with many cable experts has shown that processing is critical to ensuring that the total cable costs do not escalate out of control. The two key process attributes are: achieved with copolymer solutions. These insulations have been precisely engineered to give between 10 20% higher extruder output and faster crosslinking speeds than classic homopolymer XLPE solutions (Figure 3 A). Borlink LC8205R even exceeds this performance confirming the excellent production economics it offers cable makers. Length of cable run between extruder cleaning (critical to ensure correct quality) Achieving a stable, high and problem-free throughput of the CCV line Targeted run lengths of up to three weeks place a high demand on the compound processing and scorch retardant performance. The length of a run between stops for cleaning is determined by the consistency of compound viscosity and the fine control of crosslinking agents to minimise scorch and residual by-products. Very considerable improvements in run length have been 100% material inspection for metals Classic XLPE 150 mm Borlink Copolymer 150 mm Borlink Copolymer 200 mm Classic XLPE 150 mm Borlink Copolymer 150 mm Borlink Copolymer 200 mm Figure 3: Output (A) and run length (B) of different material combinations on different insulation extruders 8 Borlink Copolymer insulation

9 Advanced semicons improve cable insulation interface Semiconductive compounds are based on very clean carbon black dispersed within a polymer matrix. Dispersion is optimised to provide a smooth interface between the conducting and insulating components of the cable. This is in order to decrease the occurrence of protrusions that cause regions of high electrical stress. Progressive advances in this field have resulted in semicons showing a 90% reduction of protrusions compared to 30 years ago. The careful selection of carbon black and the base polymers is of key importance. Clean material is vital in order to ensure a low ion content as certain ions promote the growth of vented trees. Through continuous development the ion content of semicons has been reduced from 500 ppm in 1986 to below 30 ppm today. High pressure (tubular) acrylate copolymers have, with more than 20 years experience, been shown to be excellent polymers for advanced cable applications including use as a base polymer for semiconductive compounds. To ensure the highest level of performance, close attention must also be paid to the choice of the base polymer with particular reference to its thermal stability. The poor thermal stability of some polymers results in a higher level of by-products that can lead to contamination of the CV-tube or to voids in the inner part of the cable, and shorten production runs. Good resistance to scorch is therefore mandatory to enable the long production runs required by cable manufacturers. The choice of semiconductor compounds and the processing behaviour of the semiconductor layers have an important influence on wet ageing test results. 9

10 Better jacket protection lowers total cable cost In addition to the meticulous attention to detail with regard to the insulation and semiconductor systems, care also needs to be taken with the polymeric oversheath layer or jacket that protects the cable. To provide this protection, a number of critical properties are demanded of the material. In particular it must offer good abrasion resistance, good processing, good barrier properties and good stress crack resistance. Experience has shown that the material with the best overall composite performance is an oversheath which is based on PE. These compounds give a far higher level of protection against water than PVC, for example. Moreover, by using high density jacketing, such as Borstar HE6062, with a Shore D hardness of above 59, laying costs can be significantly reduced. Cable trenches can be smaller and the risk of damage to cables during installation is lowered. Furthermore, the trenches can be backfilled with the excavated earth as opposed to soft filling with sand, resulting in further cost reduction. The laying costs outlined in Figure 4 are an example from a utility that specified a higher hardness jacketing material. This material upgrade enabled them to improve both their cost control and the performance of their grid. Figure 4: Laying costs for selected jacketing compounds 10 Borlink Copolymer insulation

11 Overview of market experience The long term experience of cable makers with copolymer modified WTR XLPE has confirmed its value for MV cables requiring bonded insulation screens, fulfilling for example CENELEC HD620. Results from tests made by cable manufacturers have been independently collected and reported by VDE. These results show that the performance of the cables exceeds the formal requirement by a wide margin. They also indicate that an improvement of the average performance level has been made within the reported period. These figures are confirmed by market reliability data where the cable failure rates decrease over time. The data correlates with the introduction of copolymer technology and state-of-the-art triple extrusion equipment. Figure 5: Monthly average from Fertigungsbegleitende Prüfung according to VDE 0276 HD620 (Source: Langzeitprüfung an VPE-isolierten Mittel spannungskabeln nach DIN-VDE , Dr. Merschel, 60. Kabelseminar, Hannover) Figure 6: Failure rate of installed cables in Germany, in relation to year of installation (Source: Kabelhandbuch, 6. Auflage, VDEW Verlag, 2001) 11

12 Recommended material system for MV cables with bonded insulation screen Conductor screen Insulation Insulation screen Jacket Borlink LE0592 Borlink LC8205R Borlink LH4201R Borlink LE0592 Borstar HE6062/ ME6052/LE8707 (black) or Borstar HE6063/ ME6053/LE8706 (natural) LE0563 Semiconductive Table 2: MV cables with bonded insulation screen Sources for further information 1) U.H. Nilsson, AD. Campus, Polymer modified XLPE as insulation in power cables. Jicable 1999, p ) M. Kuchel, R. Schroth, P Craatz, Prüfverfahren zur Sicherstellung der Qualität kunstoffisolierter Mittelspannungskabel. Elektrizitätswirtschaft 23/99, p ) K. Morawietz, G. Heidmann, New Interpretation of long term test results of MV Cables-Material ageing or internal defect structure development, Jicable ) AD. Campus, M. Ulrich, 20 years of experience with copolymer power cable insulation, Jicable ) H. Lindemann et al, Alterung von 20-kV-VPE-Kabeln der Heag im Netzbetrieb, Elektrizitätswirtschaft (1995), Heft 26. 6) H.G. Land and H. Schädlich, Model cable test for evaluating the ageing behaviour under water influence of compounds for medium voltage cables, Jicable 1991, p ) D. Meuerer et al, Zum Langzeitverhalten von Isoliersystemen für VPE-isolierte Mittelspannungskabel, Elektrizitätswirtschaft, Jg, 1989 (1990), Heft 26. 8) D. Meurer, M. Stürmer, The Cenelec long term test for XLPE MV cables-everything new and different?, Jicable 2003, p ) J.T. Benjaminson et al, Accelerated long term evaluation of MV-XLPE cables, Jicable 2003, p ) D. Wald, Mischungen für langlebige Wechsel- und Gleichspannungskabel, Kabelextrusion 2003, p ) K.M. Jäger, L. Lindboom, The continuing evolution of semiconductive materials for power cable applications, IEEE Electrical Insulation Magazine. 12) M. Brüggemann et al, Alterungsphänomene in der inneren Leitschicht von polymerisierten Mittelspannungskabeln, VDE/ETG Grenzflächen in elektrischen Isoliersystemen, ) R. Plath, D. Wald, The Contribution of the CENELEC 2 Year Test to the Reliability of the Medium Voltage Cable Grid, Cired Borlink Copolymer insulation

13 Borealis and Borouge Dedicated to Wire & Cable Solutions Borealis and Borouge are the world s leading providers of innovative, value creating plastics solutions for the wire and cable industry. Our solutions are customer-driven and designed to satisfy the industry s continuously evolving demands for higher technical performance. Consequently, they can be found in the most challenging EHV and HV cable applications, as well as MV and LV energy transmission and distribution cables, building wires, and communications cables. In answer to the need for production, installation and cable-system lifetime enhancements, we create the innovation links that secure world-class, step-change solutions and benefit the whole wire and cable value chain. Through the introduction of unique polymer technologies, which include Borlink, Visico /Ambicat, Borstar, and Casico, we continue to pioneer the development of advanced insulation and jacketing systems for both energy and communication cables. Built on more than 50 years experience, Borealis and Borouge have a well-established track record in serving customers needs with the consistently high quality products expected of global leaders. We are committed to extending that leadership position and our role as reliable partners for the long-term a commitment not only supported by our forward thinking in innovative solutions, but also confirmed by ongoing investments for our customers continued success. Putting customers needs at the centre of our planning is reflected in Borealis largest investment in Europe to date, the new 350,000 t/y high-pressure, low-density PE plant in Stenungsund, Sweden, was inaugurated in June 2010, further strengthening Borealis capabilities to meet the needs of the growing wire and cable markets. Furthermore, Borouge s expansion of Borstar and Borlink capacity in Abu Dhabi, UAE, allows us to satisfy growing customer demand for wire and cable products in the Middle East and Asia Pacific markets and other emerging markets. Through ongoing research and development, investment in the future and a dedicated team with solid industry knowledge, we aim to remain fully responsive to our customers needs throughout the world. Disclaimer The information contained herein is to our knowledge accurate and reliable as of the date of publication. Borealis and Borouge extend no warranties and make no representations as to the accuracy or completeness of the information contained herein, and assume no responsibility regarding the consequences of its use or for any errors. It is the customer s responsibility to inspect and test our products in order to satisfy himself as to the suitability of the products for the customer s particular purpose. The customer is also responsible for the appropriate, safe and legal use, processing and handling of our products. Nothing herein shall constitute any warranty (express or implied, of merchantability, fitness for a particular purpose, compliance with performance indicators, conformity to samples or models, non-infringement or otherwise), nor is protection from any law or patent to be inferred. Insofar as products supplied by Borealis and Borouge are used in conjunction with third-party materials, it is the responsibility of the customer to obtain all necessary information relating to the third-party materials and ensure that Borealis and Borouge products, when used together with these materials, are suitable for the customer s particular purpose. No liability can be accepted in respect of the use of Borealis and Borouge products in conjunction with other materials. The information contained herein relates exclusively to our products when not used in conjunction with any third-party materials. Borstar is a registered trademark of the Borealis Group. Borlink, Visico, Ambicat, Casico and Water for the World are trademarks of the Borealis Group. 13

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16 For more information visit: Borealis AG Borouge Pte Ltd WC BROCH 103 GB BB