ELECTRICAL CONDUCTIVITY OF PRESSBOARD AND THE INFLUENCE OF MOISTURE CONTENT

The electrical conductivity σ is an important parameter for material condition evaluation at AC applications and is responsible for electrical field distribution in DC equipment. With a focus on HVDC equipment design, the influence of moisture content in oil-impregnated pressboard is determined in this preliminary investigation. The electrical conductivity of pressboard samples, which have been wetted artificially in the laboratory, is investigated within this work. Moisture contents between <0,3% and 5,5% could be achieved artificially through increasing pressboard moisture content levels in a climate chamber. The electrical conductivity was determined by voltage-current measurements at 20°C in the style of IEC 60093 with measurement times up to and longer than 24 hours. For these investigations, the pressboard samples with a thickness of 1 mm have been placed in an (mineral) oil-filled test vessel and stressed by a DC field with E = 3 kV/mm. It could be demonstrated that the moisture content of pressboard has a strong influence onto the electrical conductivity: An increase of electrical conductivity by a factor of around 10 for each percentage point of moisture increase up to moisture levels of around 3,5% was observed. At higher moisture contents (>5%), other mechanisms seem to govern the electrical current and the conductivity respectively, which is also discussed within the work

Integrative phylogenetic, phylogeographic and morphological characterisation of the Unio crassus species complex reveals cryptic diversity with important conservation implications

The global decline of freshwater mussels and their crucial ecological services highlight the need to understand their phylogeny, phylogeography and patterns of genetic diversity to guide conservation efforts. Such knowledge is urgently needed for Unio crassus, a highly imperilled species originally widespread throughout Europe and southwest Asia. Recent studies have resurrected several species from synonymy based on mitochondrial data, revealing U. crassus to be a complex of cryptic species. To address long-standing taxonomic uncertainties hindering effective conservation, we integrate morphometric, phylogenetic, and phylogeographic analyses to examine species diversity within the U. crassus complex across its entire range. Phylogenetic analyses were performed using cytochrome c oxidase subunit I (815 specimens from 182 populations) and, for selected specimens, whole mitogenome sequences and Anchored Hybrid Enrichment (AHE) data on ∼600 nuclear loci. Mito-nuclear discordance was detected, consistent with mitochondrial DNA gene flow between some species during the Pliocene and Pleistocene. Fossil-calibrated phylogenies based on AHE data support a Mediterranean origin for the U. crassus complex in the Early Miocene. The results of our integrative approach support 12 species in the group: the previously recognised Unio bruguierianus, Unio carneus, Unio crassus, Unio damascensis, Unio ionicus, Unio sesirmensis, and Unio tumidiformis, and the reinstatement of five nominal taxa: Unio desectus stat. rev., Unio gontierii stat. rev., Unio mardinensis stat. rev., Unio nanus stat. rev., and Unio vicarius stat. rev. Morphometric analyses of shell contours reveal important morphospace overlaps among these species, highlighting cryptic, but geographically structured, diversity. The distribution, taxonomy, phylogeography, and conservation of each species are succinctly described

ELECTRICAL CONDUCTIVITY OF PRESSBOARD AND THE INFLUENCE OF MOISTURE CONTENT

The electrical conductivity σ is an important parameter for material condition evaluation at AC applications and is responsible for electrical field distribution in DC equipment. With a focus on HVDC equipment design, the influence of moisture content in oil-impregnated pressboard is determined in this preliminary investigation. The electrical conductivity of pressboard samples, which have been wetted artificially in the laboratory, is investigated within this work. Moisture contents between <0,3% and 5,5% could be achieved artificially through increasing pressboard moisture content levels in a climate chamber. The electrical conductivity was determined by voltage-current measurements at 20°C in the style of IEC 60093 with measurement times up to and longer than 24 hours. For these investigations, the pressboard samples with a thickness of 1 mm have been placed in an (mineral) oil-filled test vessel and stressed by a DC field with E = 3 kV/mm. It could be demonstrated that the moisture content of pressboard has a strong influence onto the electrical conductivity: An increase of electrical conductivity by a factor of around 10 for each percentage point of moisture increase up to moisture levels of around 3,5% was observed. At higher moisture contents (>5%), other mechanisms seem to govern the electrical current and the conductivity respectively, which is also discussed within the work

Cable systems in multi purpose or shared structures

With the increase in demand and the challenges posed by the design and installation of high voltage (HV) and extra high voltage (EHV) cables in congested right of ways, structures such as tunnels and bridges for multipurpose use are becoming an attractive option. Cigre\u2019s working group B1.08 met in various parts of the world and developed engineering guidelines on Cable Systems in Multi Purpose or Shared Structures during 2006-9. This working group had electrical cable engineers from Australia, Austria, Canada, France, Italy, Japan, Korea, Netherlands, Singapore, Spain, Sweden, and the United Kingdom, and a civil engineer from the United States. With the increase in demand and the challenges posed by the design and installation of high voltage (HV) and extra high voltage (EHV) cables in dense urban and other congested right of ways, structures such as tunnels and bridges for multipurpose use are becoming an attractive option. They offer reduced overall costs, environmental advantages and less disruption to the community during installation, maintenance and replacement of cables and other services. In the Cigre\u2019 WG B1-08.9.3, the reader can follow Sections 1 to 5 and review the examples described in Section 8 to decide if a shared structure is appropriate. If the decision is to use a shared structure, Sections 6 and 7 offer expert guidance on various technical and administrative issues, forming a wonderful reference document on the design and implementation of such a system. Section 8 indeed is a review of the international experience of HV cables in multipurpose or shared structures, offering prior established experienced in this field. Future trends are summarized in Section 9. Section 10 offers a list of 60 references. A comprehensive appendix presents the results of TF B1-14, which surveyed through comprehensive questionnaires on the global use of cables and structures. The same issue for Gas Insulated Lines (GIL) has been reviewed by JWG B3/B1.09 in the TB 351 "Application of Long High Capacity Gas Insulated Lines in Structures." Scope of Work Due to the complexity of cabling in general, this study group elected to mainly deal with cable systems of 50 kV and above in multipurpose and shared structures where it felt that future investments are most likely to be made. There is no limitation to applying these principles, however, to cables of lower voltages

Italy-Austria GIL in the new planned railway galleries Fortezza-Innsbruck under Brenner Pass

The paper deals with the possibility of installing a double-circuit Gas Insulated transmission Line (GIL) in the pilot tunnel of the new planned railway galleries Fortezza-Innsbruck. The high GIL power ratings with very low power losses would allow a strong and highly efficient energy exchange particularly useful for the future European Market and could represent a new fundamental step in reconstructing the European interconnection network. Two separate railway tunnels (\u3a6 48 9,6 m) will run under the Brenner Pass from Fortezza (Italy) to Innsbruck (Austria) but will be preceded by the construction of a continuous pilot tunnel (\u3a6 48 4,3 m) useful for work logistics and chiefly for detection of the rock stratigraphy. Once the whole work will be over, the pilot tunnel will be used as a service gallery (drainage of water) where a double-circuit GIL can be efficiently installed. The paper gives the main characteristics of planned galleries, several details on the transmission line and its performance, the electro-magnetic field impact considering the proximity effects and the earthing arrangement in order to zero the touch-voltages in case of phase-to-enclosure short-circuit. The chief features of GIL solution are the lowest transmission power losses and the absence of shunt reactive compensation for this line length (appr. 65 km) but mostly the safety of personnel in case of short-circuit and the possibility of usual re-closure cycles for operation continuity. This paper gives an overview of other analysis: GIL no-load regime, electromagnetic interferences between railway and GIL system, pilot tunnel ventilation and GIL thermal regime. In order to achieve satisfying power flows, the new link requires both Italian/Austrian regional grids (380 kV\uf7110 kV) to be restructured and rationalised. This research is supported by European Community in the framework of TEN-ENERGY programme for analysing both, technical and environmental issues of integrating 380 kV Gas Insulated transmission Line and Rail Transport in tunnel between Italy and Austria entitled "Studies for a new 380 kV transmission line between Italy and Austria through the Brenner pass: Integration of Electricity and Rail Transport in Tunnel". The project leader is TERNA (Italian TSO) whereas the associated beneficiaries are the University of Padova and TIWAG-Netz AG (Tyrol TSO) with support of Graz University of Technology