b1-101 current cable practices in power · pdf filecurrent cable practices in power utilities...
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B1-101
CURRENT CABLE PRACTICES IN POWER UTILITIES
A report on the recent AORC-CIGRE Panel Regional Workshop in Malaysia AORC Panel BI members. Australia, Malaysia, New Zealand, India, Japan, Singapore, Korea,
Hong Kong SAR China, Indonesia and Thailand
Ken Barber* – Convenor AORC panel B1
It is very clear that there have been some very significant developments in the use of power cables in the ‘Asia–Oceania’ region during the last few years. However, CIGRE representation on study committees has been limited to those countries in the region that have National committees. With the recent introduction of regional groups by CIGRE, the opportunity was taken to form a panel of cable experts, to further CIGRE representation in the region. With the encouragement of the AORC and under the sponsorship of the Malaysia National Committee of CIGRE, a workshop was conducted early in 2003 with representatives from 10 countries. Current international panel B1members and observers or their representatives from these regions were present to support this development of a regional B1 panel. Each country that attended made presentations on their practices for design of cables, accessories and systems, installation and jointing, fault location, diagnostics and condition monitoring. Current and future projects were discussed along with major issues for each country and this paper is a consolidation of those presentations. After these individual presentations, each country was asked to nominate their key issues. The overall result was that four topics were considered of almost universal concern by most countries and they were: - • Diagnostics and condition monitoring of HV and MV XLPE cables. • Field testing of cable systems after installation eg. Commissioning. • Solutions for reducing the effect of EMF on underground cables. • Assessment of the true capability of assets eg. Cable ratings. The next six most important issues were: - • Reducing the cost of underground cable installations. • Solutions for condition monitoring of Oil Filled cables. • Problems with mechanical movement of Oil Filled cables. • Improved fault location methods. • Low cost tunnelling solutions and associated cabling systems. • Co-operation between utilities in reference to cable installation. It was agreed that many of these issues were similar to those being addressed by the CIGRE International Committee BI and therefore ways should be considered as to how to better disseminate knowledge in respect to such matters. The purpose of this paper is to provide a report with the objective of sharing the experiences of this region with the broader international community and at the same time, encouraging greater participation in CIGRE by experts in this region. KEYWORDS: Cable - Power - Practices – Projects
EHV XLPE CABLE SYSTEMS UP TO 400 kV - MORE THAN 10 YEARS FIELD EXPERIENCE –
W.G. Weissenberg ∗ U. Rengel R. Scherer Brugg Kabel AG Elektrizitätswerke Nordostschweizerische des Kanton Zürich Kraftwerke (Switzerland) (Switzerland) (Switzerland)
Summary
In Switzerland, the first 400 kV cables with insulation made of cross-linked polyethylene were installed in the power transmission network at the start of the nineties in the last century. The accessories used for this purpose also included pre-fabricated and pre-tested slip-on components made of silicon. These systems are running smoothly up to date. The article describes the many years of experience that have now been accumulated with EHV cable systems using cable insulation made from cross-linked polyethylene and accessories with silicon insulation. All these tests and many years of practical experience have shown that solid XLPE and silicone-polymer insulations as used in EHV cables and accessories are characterised by long electrical lifetimes. For the post-installation electrical test, if the PD measurement is used to prove that the joints and terminations are free of PD, a lower test value can be used for the a.c. voltage test, thus ruling out the possibility of advance damage to the newly-produced cable joint as a result of the commissioning test. The general technical trend for the assessment of accessories in EHV cable networks is moving towards diagnostic assessment of freedom from PD.
B1-102
New generation of GILCharacteristics and applications
P. Coventry M. Bues – Ph. Ponchon- A. Girodet –F. Loray – D. S. Pinches*
National Grid Transco AREVA T&D(United Kingdom) (France & United Kingdom)
Summary:
This paper describes the main features and performance of the second generation of Gas InsulatedLine technology. The qualification process and manufacturing process are presented. This technologycomes out of a domain of application to rather short connections generally internal to metal enclosedsubstations to be applied to cases of short sections of lines with high transmission capacity.
The first generation of GIL has been developed with purely GIS technology. It has beendirectly used inside or in relation with gas insulated substations and is well adapted to connectionlengths up to several hundreds of metres. The total world-wide experience, all manufacturers andvoltage cumulated from 72.5kV to 550kV, is estimated to be more than 300km single phase circuit. Asecond generation of GIL technology is now emerging. Application to transmission networks from145kV to 550kV is now possible with the best economical performances probably for 420kV and550kV networks.
This paper describes a typical 420kV GIL. Different aspects of the technology are presented:� Basic performance and main technical features.� Type testing.� Manufacturing and factory testing.� Erection and testing on site.� Monitoring, maintenance and reparation.
An actual example of an application where a section of GIL is being constructed as part of a 420kV transmission line is also presented.
GIL has an intrinsic very high transmission capability. Typically, in open-air conditions, it allowsup to 5000A (~3500MVA at 400kV) with a short time current of 63kA.
Numerous different arrangements such as above ground arrangement, trenches with or withoutcover, tunnels and directly buried arrangement are possible. The permissible transmission capability isof course depending on arrangement and on conditions such as ambient temperature and ventilation
In addition to evident advantages over overhead lines like insensitivity to weather conditionsand reduced visual impact, GIL has a higher current rating, lower emitted electromagnetic field andlower capacitance than conventional cables.
The proven technology of GIL using bolted flanges is well adapted to connections up toseveral hundreds of metres in length. The second generation of GIL using site welded enclosure jointsextends the range of application to longer length connections with high transmission capacity.
The case of the GIL for the substation located in the West Midlands is an example of this kindof application.
B1-103
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B1-104 Testing of Extruded Cables: experience in Type Testing, PQ Testing and Test After
Installation. What do we learn from it?
E. PULTRUM∗, S.A.M. VERHOEVEN, KEMA High Voltage Laboratory, Netherlands
Summary This paper illustrates our experience in testing extruded cables and accessories. During the period considered here, over 170 components have been type tested and almost 500 km of cable circuit has been commissioned (Test After Installation, TAI). Furthermore, in this period two pre-qualification tests have been performed on 400 kV cable systems. A remarkable difference has been noted between type tests on MV and HV cables. Even though from a constructional point of view they are the same, MV cables are more successful in type testing than HV cables. A plausible explanation is the absence of voltage application during heating cycles in IEC 60502, Part 2. This omission should be rectified. Accessories have to handle the high stresses in the interface and avoid a local increase of field stress. Especially for joints this can be quite demanding. Minor differences between similar cables from various manufacturers might result in slightly different stresses in the interfaces in joints which might affect the long-term behaviour. From this point of view it could be sensible to (type) test a certain intended combination of cable and accessories. Also a decrease through the years in successful type tests on MV accessories is noticed. In this range quite some new developments have been undertaken by the manufacturers. As parts of a learning process these glitches allow the manufacturers to improve their design. This shows the value of type testing. As a pre-qualification test, a cable system is operated for one year at 1,7 U0 with temperature cycles reaching just above the maximum allowable conductor temperature. These tests are definitely demanding, both from a technical point of view and regarding the patience of the manufacturer. A one year test seems to be in conflict with shorter time-to-market, but present experience indicates that a reduction in test time is not advisable. An alternative is to incorporate some redundancy and additional measurements, e.g. partial discharge measurement, that allow certain flaws without discrediting the component. The TAI experience shows that testing at U0 is more or less the same as not testing at all. Higher voltages should be used for testing as recommended by CIGRE, e.g. 1,7U0 during 60 minutes. This is based on the fact that for the almost 10% failures, the 'time-to-breakdown' ranged from only a few seconds to 16 minutes when testing at 2U0, increasing to 23 minutes for 1,7U0. Keywords High Voltage – Cable – Accessory – Test – Type – Pre Qualification – Commissioning
Development of high-stress XLPE cable system
D.H. Cho*, D.S. Ahn, J.S. Yang, S.I. Jeon, J.Y. Koo S.K. Kim, W.K. Park, S.C. Hwang Hanyang University
LG Cable Ltd. (Korea) (Korea)
Summary The design of newly developed high stress cable, techniques of manufacturing process and test results were described. Super clean cross-linked polyethylene (XLPE) compound produced under the strict quality control in overseas facility and super smooth quality semi-conductive compound produced in-house facility were used to produce model and real cables. The miniature type of model cable was used as a specimen, which represented the real cable’s characteristics. From the test results of model cables, EL,AC, and EL,Imp were determined by Weibull distribution. Using these factors, the value of tAC and tImp for 132kV XLPE cable were calculated to be 5.7mm and 11.6mm, respectively. Based on the thickness obtained, the designed insulation thickness for real cable was determined to be 13mm which was 1.4mm thicker than the value of tImp calculated. The reliability of this high stress cable was confirmed by both AC and Impulse voltage test. Along with the high stress cable, the pre-molded joints (PMJ) for applying to high stress 132kV XLPE cables were also developed. The type test of cable and accessories were performed in accordance with IEC60840 at the final stage of development. The test demonstrated that high stress cable and accessories met all requirements of test specifications and they were sufficiently reliable. The developed high stress cable has the similar diameter of conventional OF (Oil-filled) cable and so it enables the construction of transmission line easier.
*LG Cable Ltd., EPRL, 190, Gongdandong, Gumi City, Gyeongbuk, Korea; E-mail: [email protected]
B1-105
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B1-106
ON-SITE PD DETECTION AT CROSS-BONDING LINKS OF HV CABLES
SUMMARY W. WEISSENBERG*
BRUGG KABEL AG
(Switzerland)
F. FARID
GIZA CABLES CO.(Egypt)
R. PLATH
IPH BERLIN (Germany)
K. RETHMEIER, W. KALKNER
TU BERLIN (Germany)
On-site PD measurements on HV cables have to concentrate on the cable accessories because there is a remaining risk for assembling faults on site. PD sensors with an appropriate coupling behavior to accessory-internal PD give sensitivities of a few pC or even better. Unfortunately, two main reasons prevent the general use of PD sensors in cable accessories. First of all, the costs for PD sensors have to be balanced with the costs of the accessories, importance of the cable link, consequential costs for outages etc. This is the reason why PD sensors were mainly used for EHV cable systems. The second reason is limited accessibility: the PD sensor cable at the accessory has to be connected to a PD detection unit. Accessibility is much more difficult for direct buried cable systems than for cable terminations and for tunnel-laid cable systems: the sensor cable must pass the ground and end up in a box on the surface to provide access. This solution causes additional costs and new problems like sealing the sensor cable against humidity, capability to withstand sheath testing etc. By looking for alternative access to PD signals from cable joints of long cable systems, a very simple solution proved suitable: detecting PD at the cross-bonding links. To investigate the high frequency propagation of PD pulses in cross-bonding links, computer simulations and laboratory measurements were done. On-site PD measurements at cross-bonding links of a 220-kV-XLPE cable system showed unexpected high sensitivity. Using HF transformers for PD coupling and appropriate signal processing led to PD sensitivities of a few pC or even better. The use of cross-bonding links for on-site PD measurements is suited for direct buried systems, has no impact on the cable system, needs no PD sensors in the cable joints, offers a low-cost solution and so opens a wider range of applications in cable testing.
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B1-107
550 KV GAS-INSULATED TRANSMISSION LINE FOR HIGH POWER RATING IN THAILAND
V. PIPUTVAT W. ROCHANAPITHYAKORN T. HILLERS EGAT EGAT Siemens H. KOCH* S. POEHLER G. SCHOEFFNER
Siemens Siemens Siemens
Thailand/Germany
SUMMARY The world's first Gas Insulated Transmission Line (GIL) with N2 and SF6 gas mixture at a voltage level of 550 kV has been in operation in Bangkok, Thailand since January, 2002. The high current rating of 4000 A makes this GIL to one of the strongest high power transmission systems worldwide with 3800 MVA power carrying capability. The GIL is operated under severe ambient conditions with high sun radiation and high ambient temperatures, respectively. The high thermal requirements made it necessary to use accurate thermal calculations. This was facilitated with two different thermal calculation tools, using analytical and finite element methods. The results have been verified with measurements on prototypes and existing GILs in service. The Electricity Generating Authority of Thailand (EGAT) has built a gas-insulated 550 kV switchgear in the Sai Noi substation 8 line feeders and 2 connection bays to the existing GIS. The decision was made for GIS technology in spite of AIS because land acquisition was expected to become difficult. The existing and the new GIS equipment are installed in the same building. The new 550 kV GIS, the existing GIS and the overhead lines are connected by GIL and by air insulated buses. The 2nd generation GIL design is optimised for on-site assembly which results in minimum installation times. The experiences gained with the on-site assembly, the gas handling and the high voltage testing were very positive and the works could be carried out in a shorter time frame than planned. In addition to the description of the project this article emphasises also on some physical advantages of GIL. KEYWORDS GIL - On-site Works - On-site Testing - Transmission Losses - Dielectric Layout -
Thermal Layout
1600 MVA ELECTRICAL POWER TRANSMISSION WITH AN EHV XLPE CABLE SYSTEM IN THE UNDERGROUND OF LONDON
SCOTT SADLER SIMON SUTTON HORST MEMMER JOHANNES KAUMANNS* NATIONAL GRID TRANSCO SÜDKABEL GMBH (UNITED KINGDOM) (GERMANY) SUMMARY: For 1600 MVA bulk power transmission in the underground of London a 400 kV XLPE cable system was planned and developed to fulfil the increased power consumption of the mega polis. This project sets a new milestones for the European XLPE cable technology for project engineering, cable system dimensions and transmission rate and testing: A 20 km long tunnel with an inner diameter of 3 m was driven through the London underground in a depth of approximately 30 m which allows a straight route independent from the surface situation. The tunnel will show a cooling system with forced air to increase the transmission capacity of the cables which are installed in a vertical flat formation. Temperature monitoring along the tunnel route and cable screen will optimise the load situation of the cable to ensure a continuous transmission capacity of 1600 MVA for one cable system. The delivered cable lengths up to 1000 m leads to a total drum weight of 47 t which has to be handled during production, shipping, and installation. This extreme long cable length was chosen to reduce the total number of joints. The complete cable system consists of 60 km cable, 60 cross bonding joints, and 6 GIS terminations. The EHV XLPE cable shows an insulation thickness of 27 mm. The cable outer sheath shows an extruded flame retardant layer to prevent the development of fire along the tunnel. In order to qualify the full cable system a type test and a pre-qualification test according IEC 62067 has been successfully carried out at independent testing institutes. The on-site AC testing procedure will set a new mark: At an AC voltage of 280 kV 20 km of 400 kV cable and 20 joints will be simultaneously tested and PD watched.
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B1-108
With the total cable capacity of 4.4 µF the AC charging current will be 230 A. To solve this task a new mobile resonant testing equipment has to be build. An extended PD measuring and transmission technique will be applied. The analysing technique is able to reduce the external noise level to 1 – 2 pC for the joints during PD testing even under on-site testing conditions. This is possible by selection of the frequency range with a low noise level which is used for PD-measurement. The tunnel work started April 2001. Since then both the shaft and the 20 km tunnel have been completed. All cables and accessories has been manufactured in 2002/2003. The head house will be finished in 2004. The cable installation will be started in 2004. On-site test and commissioning is planned for mid 2005. KEYWORDS 400kV EHV XLPE Cable - Tunnel Project - Bulk Power Transmission - On-site Test - PD-measurement
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B1-109
EXTREMITES ENTIEREMENT SYNTHETIQUES POUR CABLES A TRES HAUTE TENSION
M.H LUTON * P. MIREBEAU P. DEJEAN F. LESUR V. CAPGRAS Sagem Nexans Câbles Pirelli EDF R&D RTE - Réseau
de Transport d'Electricité
FRANCE
Abstract
Completely synthetic terminations for 90kV cables were developed and several installations have already been carried out on the French Network and abroad. On the same principles of design, using stress cones of specific geometry and electric characteristics, synthetic terminations were developed for the higher voltage levels 138, 170 and now 225 kV. These terminations of a weight much lighter than the usual equipments will offer many advantages : - simplicity and speed of assembly, - many possible alternatives of installation (poles, stations, with or without slope), - null explosion or fire hazard, - absence of maintenance. The global management of the link is simplified. - respect of the environment by a particularly reduced visual impact related to its
compactness. The absence of fluid also notably reduces pollution likely to be generated. - reduction of the costs of the structures intended to support these equipments. This report initially presents the generic structure of these new equipments, as well as the various families of materials being able to be used. So that these new terminations profit from performances equivalent to those of the outdoor type terminations with insulator, specific tests sequences were elaborated, standardized (NF C 33-064 and C33-065) and used for the validation of these new equipments. The properties of behaviour to the most severe external climatic constraints were very carefully studied and led to the definition of new tests allowing the validation of the termination and that of materials constituting it. For this purpose, a new climatic test chamber has been built. It allows the test of full-sized terminations up to the 225kV range. The climatic long duration test developed and performed in this chamber lasts 5000h and alternate each week under voltage, salt fog, solar radiation, heating and rain sequences. After these recalls relating to the design and proposed procedure of approval, the report describes the first achievements and evokes the future prospects for this kind of equipment.
Keywords Termination, High Voltage, Safety, Environment, Short-circuit, Climatic Ageing.
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B1-110
Trends in Degradation Diagnostic Technique for XLPE Cables in Japan
Atsushi Toya*, Masahiko Nakade, Yukio Okuyama, Katsumi Uchida, Tokyo Electric Power Co. Chubu Electric Power Co., Inc.
Hideo Tanaka, Kazuo Watanabe VISCAS Corp.
(Japan) Summary
XLPE cables in 22-77 kV class with no water barrier sometimes suffer dielectric breakdown due to water-tree degradation. For them, it is necessary to develop water-tree diagnostic method.
Several methods, for example, DC leakage current can only be applied to LV-class XLPE cable. To diagnose water-tree degradation of 22-77 kV class XLPE cables, however, it is necessary to develop a new technique that would enable detection of feeble signals from un-bridged water-tree. The authors have successfully developed 2 different types of nondestructive diagnostic methods and put them to practical use. The first method is the Loss current method. In this method, the 3rd harmonics in the loss current is used to detect water-tree degradation. With the progress of degradation, the amplitude I3 of the third harmonic tended to increase and the phase difference θ 3 of the third harmonic relative to the applied voltage tended to vary in the positive direction. In the actual criterion for cables, both I3 and θ 3 are used.
The authors prepared field measurement system on a truck and made field diagnosis of twenty-two 66-kV class XLPE cable lines. Some of these cables were removed and subject to diagnosis again and AC breakdown tests after removal. The results of judgment and AC breakdown test show good agreement. A commercial-level diagnostic service by this method was inaugurated in 2002.
The second method is the Residual charge method. In this method, charge is once accumulated in water-tree by DC pre-stress and then released by AC voltage after short-circuiting. The degree of degradation is judged the maximum AC voltage at which the residual charge is released. This is suitable to detect the localized water-tree degradation.
The authors prepared field measurement system and conducted field diagnosis of four 22-33 kV class XLPE cables. Some of them were subjected to breakdown tests on site and showed good agreement with the predicted BD values. The relationship between the charges released maximum AC field and AC breakdown field showed a strong correlation. This shows the appropriateness of the field diagnosis.
These 2 nondestructive methods are not capable for the location of degradation. To locate the deteriorated part, the screen test method is also adopted. With this method, the points of degradation can be identified. AC (50/60 Hz) and Very Low Frequency (up to 0.1 Hz) are suitable. The AC test has been conducted on about 70 lines and the VLF test on 9 lines.
In Japan, the nondestructive method is first applied to an XLPE cable lines. If degradation is judged, then the points of degradation are identified using the screening test. This selective use of diagnostic methods makes it possible to achieve diagnostic cost reduction, high accuracy, and high efficiency.
Keywords XLPE Cable- Water-tree Degradation - Diagnosis- Nondestructive test - Screening test
Higher-stress Designed XLPE Insulated Cable in Japan
A. TOYA K.KOBASHI Y. OKUYAMA Tokyo Electric The Kansai Electric Chubu Electric
Power Co. Power Co., Inc. Power Co., Inc.
S. SAKUMA* S. KATAKAI K. KATO VISCAS Corp. J-Power Systems Corp. EXSYM Corp.
(Japan)
In Japan, the realization of high density power transmission in major city areas requires the effective utilization of limited underground space, available, for example, in tunnels and ducts. Thus, for many years, particular efforts have been directed towards reducing the construction period, cutting the cost, and improving the reliability of extra-high voltage lines. This has necessitated a reduction in the number of joints, and thus long cable manufactured in continuous length had to be transported from the factory to the installation site, an undertaking that required the development of technology to installation the cable directly from the unloading point. At the same time, it has become essential to maximize the transportation length of the cable and to reduce its weight.
In response to these needs, cross-linked polyethylene insulated cable with a reduced insulation thickness and the joints suited to it has been developed in Japan. This cable is capable of handling currents of up to 500 kV, and has been successively used in practical applications.
This paper will discuss Japan’s XLPE cable insulation technology for reducing insulation thickness, namely the design technology, the materials technology, the manufacturing quality control technology, and the quality assurance technology that has permitted the conversion to high stress cables, as well as operation records of these high stress cables. It will touch upon the adequacy of the test conditions and concepts involved in the development of the tests for verifying that the products could be applied in actual systems. It will also present the efforts made to ascertain approximately what future design stresses could be achieved by determining through experimentation the ultimate stress that could be tolerated without degradation.
The development of 500 kV XLPE cable has already made the utilization of approximately 12 kV/mm cable with average stress a veritable reality. As a result, we are convinced that it will be possible for cable to be further compacted through the application and expansion of the technology that has been cultivated in manufacturing quality control and that is greatly reducing impurities and protrusions, as well as through the improvement and development of joints.
B1-111
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B1-112
SLIM CABLES, COMPACT CROSS-BONDING AND CORRECTED DISTANCE PROTECTION
N.G.H. Steentjes J. Pellis, J.C.M. van Rossum Nuon Tecno. Eneco Netbeheer b.v. Pirelli Cables and Systems. (The Netherlands) (The Netherlands) (The Netherlands) M.J.M. van Riet * W.F.J. Kersten Nuon Tecno. Eindhoven University of Technology. (The Netherlands) (The Netherlands)
Keywords: Cables, Cross-bonding, Distance Protection.
Abstract In the Netherlands, high voltage connections will increasingly be realized using cables as it is very difficult to get permits for overhead lines. Pirelli and Nuon are continuously improving the design and production of the cables for increased reliability and capacity as well as lower costs. To this end, the present XLPE insulated cable has been optimized using a thinner primary insulation and lead sheath. The layout of production has been improved to lower manufacturing costs. Cable capacity has been improved by the choice for a thinner lead screen as well as increased use of cross-bonding. A cross-bonding box has been developed that allows capacity to be increased significantly at limited additional costs. The distance protection of cables has been revised to correct the calculation error caused by the return current in the screen. It is shown that adequate correction can be achieved using a real value which depends only on cable characteristics. This considerably eases implementation into new and in existing systems. * [email protected]
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B1-201
IMPROVED OPERATION OF CABLES CONNECTING OFFSHORE WIND FARMS TO THE POWER GRID
H. J. JOERGENSEN*, J. HJERRILD, C. JENSEN AND J. HAVSAGER
DEFU, ELTRA AND ELKRAFT SYSTEM
Denmark
Cables connecting large wind farms to the power grid have load variations that differ from what other transmission cables are subjected to. The load is determined by wind speed and temperature, and large fluctuations occur. This makes it difficult to choose the optimal design of a cable system for this purpose, and there will be a tendency to build in too large safety margins in the design. To get a better knowledge of the load variations and the possibilities of operating the cable closer to its limits, distributed temperature measurements and load measurements have been made on cables connecting two Danish offshore wind farms to the power grid. The wind farms are located at Horns Rev in the North Sea (160 MW) and Nysted in the Baltic Sea (165 MW) and in both cases a combination of submarine and underground cables operated at 150 kV and 132 kV, respectively, is used for the grid connection. The wind farm at Horns Rev has been in operation for more than a year while the one at Nysted has only been in commercial operation for about one month. The cables to the two wind farms were designed for the maximal nominal power output from the wind farms using the thermal properties for the soil recommended in the standards. These design principles were known to lead to rather low cable temperatures except during very dry and windy summer periods. The measurements are used in mathematical models to calculate the dynamic rating of the cables, and the results obtained so far have confirmed that the cables have an unused load capacity during most of the year. The fluctuating load reduces the heating of the cable compared to constant load at maximal power output, and the large thermal time constant of the cable and the surrounding soil makes it possible to increase the peak load of the cable. The measurements and calculations will be used to improve the operation of future cables to offshore wind farms. An enlargement of the wind farm at Horns Rev is foreseen, and here the existing cable could become part of a ring net so that the loss of production due to cable maintenance and cable faults could be minimised. For other wind farms the results will be used to design the cable system closer to the limits and to assess the benefits of installing temperature monitoring equipment on such cable systems. Key words: Temperature – Monitoring – Cable – Offshore – Wind farm
14
B1-301 STRATEGIC SHARING OF PIPELINE ASSETS AND RIGHTS OF WAY WITH
UNDERGROUND POWER CABLES AND OPTICAL FIBER CABLES
Dr. Jey K. Jeyapalan*, P.E. Dr. Jeyapalan & Associates, LLC.
United States of America
People from most countries have long had the desire to move their overhead power lines, telephone lines, CATV lines, and optical cables to the underground. It’s ironic that, 21st technologies controlling 21st century economies are still relying on 19th century wooden poles. When we the people pose the question why more of these services are not buried, all the service providers are quick to dismiss the idea, saying it would be too costly. But, as regulated entities, this is not their decision. In fact, it's ours who pay the price dearly because power and other service disruptions affect our economy, cost jobs, and create hardships for our households and businesses. A comprehensive global survey by the author given in this paper indicates that most countries around the world would prefer to move their overhead power lines underground. This is due to numerous reasons including the following: Increasing Pressure From Environmentalists; Increasing Pressure From City Planners; Losses From Frequent Outage; Loss From Bad Weather; High Cost of Maintenance; High Transmission Loss; Electrocution; Bushfire Risks; High Greenhouse Emission; Auto Accidents; Cost of Tree Pruning; Better Aesthetics; Better Real Estate Value. Cost and the underground already being so crowded have been the reasons given by the power companies for not putting cables underground. Then, there are countries like Denmark, Germany, Holland, Hong Kong, Iceland, Israel, Singapore, Sweden, Switzerland, United Arab Emirates that have already moved most of their overhead power lines to the underground despite their GDP/capita being lower than that of America. With cable companies and sewer, gas, and water departments digging up streets all the time, why public officials are not implementing a policy of utility corridors for burying all services together? The end users craving for infinite bandwidth from communication companies in poor financial status already have sanitary sewers, storm drains, waterlines, hot water pipes, and natural gas lines reaching their premises. It makes sense to build the last mile optical fiber and power cables in these existing rights of way on pipelines. This paper provides many creative proposals for various segments of the power cable industry, optical cable industry, private companies, energy companies, and municipalities to work together to solve pressing problems of the 21st century society. Keywords: Power cable-Underground-Utility corridor-Last mile-Optical fiber-Fiber to the Home- Partnership-Sharing
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B1-302
330KV CABLE SYSTEM FOR THE METROGRID PROJECT IN SYDNEY AUSTRALIA
S.L. Jones*, G. Bucea, T. Barnes TransGrid (Australia)
M. Mitani, Y. Matsuda, A. Jinno J-Power Systems Corp. (Japan)
The MetroGrid Project was designed to reinforce the power supply system to the city of Sydney. The 330kV power cable was a major component of this project and was installed between an existing 330/132kV Substation and a new 330/132kV indoor substation in the Sydney central business district. This important circuit presented a range of challenges relating to design, testing, installation and condition monitoring systems. An SCFF-PPLP cable from J-Power Systems was selected from 29 offers to best meet the project requirements. The contracted cable system was extensively tested (type, special, routine and sample tests) and met all specified requirements. Along the 28km cable route the cable was installed in very diverse terrain conditions and required a wide variety of installation methods. A Dynamic Bending Test was designed to test the stability of cable component parts under the most severe dynamic loads encountered during installation. This test was specified and performed for the first time and ensure that the installed cable would meet all performance expectations after installation. The magnetic fields surrounding the cable became an issue for this project during the planning and approval process. An EMF experiment was designed and performed to determine the possible mitigation methods to be applied during installation. Analytical calculation methodologies for the prediction of EMF were verified against the actual test results. The EMF trial installation was also used to verify the thermal parameters of the cable and to study the temperature profile of the cable circuit based on actual installation configurations and environmental conditions. Based on the recorded data, provided by the distributed temperature sensing (DTS) system installed on the trial installation, the accuracy of the cable system thermal model was confirmed. This data is used in the real time cable rating software. A condition monitoring system using optical fibres for monitoring and data transmission provides real-time feedback of the cable condition. The MetroGrid Project has imposed significant demands on the selection, design, testing and installation of a long 330kV power cable circuit as described in this paper and these challenges have been met through innovative features that give greater confidence in the reliability of the cable installation.
16
B1-303
Modern installation techniques of high voltage cable systems in the Netherlands
G.L.P. Aanhaanen, TenneT Zuid-Holland, W.G.M. de Beer, Essent, L.J. Boone,
DELTA N.V., R.F.F. Koning, Pirelli Cables and Systems N.V., J.T.M. van der Wardt and C.G.N. de Jong, NUON, J.A. Wiersma, ENECO/ENBU, J.F. Zantinge*,
TenneT bv
(The Netherlands) Session Summary
For several decades, insulated power cables are a reliable alternative for high voltage overhead lines. Due to expanding of urban areas, and growing concern about spatial planning, undergrounded power for all voltage classes becomes more interesting. In a dense populated country like the Netherlands this demand requires sophisticated installation techniques for high-voltage power cables. A regional grid company realized an underwater crossing of the Westerschelde river, consisting of 6 XLPE cables at 150 kV-level. The cables were tied together in a hexagonal construction, centered by a polyethylene spacer with a steel pulling cable in the center. Unbroken cable lengths up to 2270 m were installed in a river mouth crossing with floating vessels. The water crossing has a total length of 5,5 km and the entire connection has a length of roughly 8 km. Joints have been made on a sandbank, in the middle of the river. The cable sections in the deep water-crossings were laid in a trench, made by a dredger. Several conductor sizes and materials were used in this connection. A regional grid company realized a 18,2 km 150 kV XLPE connection from a substation to the Rotterdam harbour. The connection crosses a polder with a soil of peat, a railway station and a sea dike. A grid company transformed a 150 kV double circuit high-voltage overhead line into an underground connection in a new residential area at the outskirts of the city of Utrecht. Two major parts of the connection have been realized by four directional drillings, down to depths of 33 m. A grid company realized a 150 kV project near Amsterdam with lengths up to 1,4 km where 56% of the connection was installed in horizontal drillings. The installation of 2 XLPE insulated cables in a single steel casing in a borehole over 1,4 km under a lake was part of the project. Another grid company realized a 6,5 km 150 kV XLPE cable connection for the power supply of a new substation close to the city of Breda. The connection consists of two circuits in trefoil formation. A number of directional drillings up to 400 meter was used to cross railway and highway tracks. The national Transmission System Operator for the 220 and 380 networks carried out a feasibility study for an underground 400 kV-cable circuit in an unused 26" oil pipeline up to 27 km length in the province Zuid-Holland. The pipeline would contain six XLPE insulated 400 kV cables and the circuit would be suitable for a transmission capacity of approximately 1900 MVA. Another project to make a river crossing with three XLPE insulated 400 kV cables installed in directional drillings up to 700 meters, is under study.
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17
B1-304
LONG LENGTH EHV UNDERGROUND CABLE SYSTEMS IN THE TRANSMISSION NETWORK
M. DEL BRENNA, F. DONAZZI (*), A. MANSOLDO PIRELLI CAVI E SISTEMI ENERGIA SPA
(Italy)
SUMMARY The power transmission network has developed during the last decades based on the use of overhead lines. EHV underground insulated cable systems have been available since a long time (fluid filled technology initially and solid dielectric technology more recently), but their development has always been limited, mainly due to economic constraints, and they have been adopted for those applications where overhead lines could not be pursued. For long length connections, some technical constraints have been raised against the adoption of underground cable systems. On the other hand, environmental considerations, together with an increasing need for optimization of the transmission network, push to reconsider the real impact of underground cable systems backbones. Among the claimed technical issues, related to underground cable systems, the most sensitive topics are those concerning length limitations, reliability and impact on the transmission grid. Indeed, while at the High Voltage level (i.e. up to 170 kV) those problems have minor influence, some dispute is still alive for EHV applications. However, in light of the evolution of cable systems technology, new installation techniques and new compensation concepts, this theme shall be reconsidered, studied in more depth and brought back to a balanced rationale. In this paper the following topics are analyzed: · State of the art of AC EHV cable systems · Determination of criteria for the definition of the maximum permissible length for EHV
underground cable systems, their rationale and their implications in the network · Considerations on new compensation concepts and their impact on the network at
different load conditions · Cable self-protecting effect in fast transients · Considerations on reliability and availability of underground cable systems, with reference
to diagnostic and monitoring techniques A study case is analysed to demonstrate the feasibility of using EHV underground cable systems in long backbone transmission connections.
DOUBLE 150 kV LINK, 32 km LONG, IN BELGIUM : DESIGN AND CONSTRUCTION
A. Gille *, V. Beghin G. Geerts, J. Hoeffelman D. Liémans, K. Van Gucht BEL ENGINEERING ELIA NEXANS
(Belgium) 1. SUMMARY The double 150 kV link that runs from the Tihange nuclear power plant to the new high-voltage substation in Avernas is the largest underground link ever built in Belgium. Initially planned as an overhead line, the project was modified several times following interventions of the authorities and objections of the public, and resulted finally in a mixed overhead-underground project. The exit from the nuclear power plant and the crossing of the river close to the plant are built overhead (2 km). Further, via a transition compound, the remainder of the link is underground (30 km). Three cables per phase laid in a trefoil configuration, without cross-bonding, were envisaged initially. Some hypotheses led to a solution having only two circuits in flat formation, with cross-bonding. The working permits laid down a number of requirements like consultation meetings with municipalities and magnetic shielding near housings and schools. Computer simulations and measurements made it possible to define a model of aluminium shielding. The report also investigates aluminium corrosion and the problems related to the detection of sheath’s faults that could arise under aluminium sheets overlapping each other over substantial distances. Also, direct cross-bonding is used, in order not to install sheath voltage limiters (SVLs). Accordingly, the cross-bonding joints were sized for a 150 kV surge voltage (1.2/50 µs shape) between screens at the interruptions of the screens. Nevertheless, the transition compound has required the installation of boxes with SVLs at the first two joints starting from the overhead line, in order to avoid having to oversize the direct cross-bonded joints. A special work track could be built parallel to the cable trenches enabling to work simultaneously on many sections of the link and resulting in a substantial progress rate. Hence, cable work was completed in about one year. Finally for commissioning the link, AC testing of the cable and accessories was performed.
Keywords: High Voltage - Power Cable - Thermal Resistivity - Magnetic Shielding - Direct Cross-bonding - Overload Conditions - Fault Detection - Distributed Temperature Measurement - After Laying Test. * [email protected]
B1-305
19
B1-306
POWER TRANSMISSION OVER LONG DISTANCES WITH CABLES
GEORG E. BALOG*
NORBERT CHRISTL*
GUNNAR EVENSET
FRODE RUDOLFSEN
NEXANS SIEMENS NEXANS NORCONSULT (NORWAY) (GERMANY) (NORWAY) (NORWAY)
Abstract
Transporting electrical power over long distances by cable, is the theme of this paper. Today’s there are two main state of the art transmission principles available, AC or DC systems. A description of the main features of the alternatives available today is the first part and the comparison of their costs and effectiveness will be discussed in the second part. To be able to compare the cost-effectiveness, the complete transmission systems, including the cost of losses are compared. In this paper the comparison is based on compensated AC three-phase cable systems with XLPE insulated cables and bipolar DC transmission systems based on Voltage Source Converters and Mass Impregnated or extruded cables, over long distances, up to 200 km.
Summary
The paper is based on the new technologies available for AC and DC transmission systems. The three core or three foil XLPE insulated 245 kV cables offer an optimum AC transfer capacity of approximately 250 MW for distances up to 200 km. The system must be compensated so half of the charging current flows to each end. The compensation my be effected either by passive, mechanically switched shunt reactors or by dynamic power electronic based elements. The new DC converter technology is the VSC converters with either traditional MI cables or especially for land usage cables with extruded insulation systems. VSC, can be used for transmission into remote isolated weak system areas, without installation of additional support by large rotating phase shifters or other generators in the remote AC net In this paper also the cost of capitalised losses included. It is set at 1900 k€/kW. The results show that if no special network requirements are present the break-even length for the two transmission systems is in excess of 200 km both for land and submarine cables. If the AC system requires dynamic compensation the break-even distance decreases to approximately 200 km. The cost of civil works and eventual platforms is not taken into account. e-mail: [email protected] e-mail: [email protected]