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REPORT On the Research-to-Practice Conference regarding Specifics of operating and designing VL 35-750, using high-strength and high-temperature wires and ground wearers, including OPGC hosted on 6 December 2016 by Russian National Committee of CIGRE, in association with PJSC Rosseti, PJSC Federal Grid Company of Unified Energy System (PJSC FGC UES).

The event was held on the first day of the International Specialized Exhibition Electric Network of Russia-2016 initiated by management of Engineering Company Energoservis LLC with organizational involvement of Operation and Diagnostics Service LEP PJSC FSK MES-Center (headed by A. V. Eliseenko, this Service is a base for RNC CIGRE 2V Subcommittee). More than 70 people attended the Conference. Such attendance of the Conference shows how essential it is to have field-specific events for design engineers and how much interest the new types of wires inspire. At the Conference there were representatives of the following organizations: 1) reasearch establishments and institutions engaged in developing a new generation of main elements for overhead high-voltage line structures (OL); 2) manufacturers of equipment for OL; 3) companies for OL operation and service maintenance. 9 reports were read, with 15 people involved in ensuing debates.

In many countries of the world, developers offer new solutions to enhance OL reliability and transmission capacity, to prolong OL service life and to reduce time for troubleshooting and routine repairs.

Some of these solutions have been tested in real life, others have not. In particular, this applies to a new grade of aluminum-steel non-insulated cables of ASVP and ASVT type, single-lay with linear wire crossing, plastically crimped steel and aluminum parts. Initially, these products were developed and patented by Engineering Company Energoservis LLC.

Research of corona-discharge of plastically deformed ASVP/ASVT wires and comparative tests of operational drawing-down of conductors in accordance with the same technology were presented at the Conference. This research was implemented by JSC NTTs FGC UES. It was conducted in compliance with a decision made at PSJC FGC UES meeting.

V. N. Kurjanov, Senior Lecturer in Power Engineering and Electrical Engineering of MEI Affiliate, PH.D. in Technical Sciences, delivered a report on omparative test results of operational drawing-down and corona-discharge of plastically deformed wires, as well as an overview of design solutions using the above products. He underlined that the conducted tests proved compliance of declared mechanical and electrical properties of plastically crimped ASVP/ASVT wires with STO 71915393-TU 120-2012 requirements, and a number of important specifics:
Experiments show that the operational drawing-down is reduced 45 times as compared to standard designs, regardless of material (steel, aluminum and copper).
Corona-discharge inception voltage in Energoservis ASVP wire is higher than that of AS grade wire with the same diameter, meanwhile ASVP continuous current-carrying capacity is higher.
New wires have higher transmission capacity (especially for a high-temperature design).
In the wire-accessories system, wire tensile strength parameters exceed similar AS parameters virtually twofold.

The Conference participants involved in debates on the delivered report observed that a traditional AS wire showed good results, though it had a number of drawbacks such as a relatively large diameter, rough surface and a rather heavy core. New wire offered by Energoservis solves the problem of enlarging length of span, however, it requires additional costs to increase mechanical strength of supports. But as some projects reveal, ASVP/ASVT wires generally reduce construction costs due to a fewer number of supports and life cycle costs due to combined electromechanical properties.

To obtain required temperature resistance, the new products use zirconium alloys, new multiplex technology, innovative design of the core and the wire itself. As compared to AS wire with the same strength, ASVP/ASVT wire smaller diameter and design allow reducing loads on supports by decreasing aerodynamic and ice load effects. Higher strength helps to lessen sag of conductors. The wires allow to enhance OL transmission capacity up to 1.5 times. This design and technology are protected by the 17 Russian Federation patents (patent priority since 2013-2014), and the production technology of plastically deformed wire is protected by the German Patent DE102014101833.

The product costs depend on many aspects, a primary one being a large-scale production, which in its turn was confirmed by Yu. S. Lyadov, a representative of Rusal, a manufacturer of aluminum alloys.

In his report, PH.D. in Technical Sciences A. K. Vlasov gave an overview of research activities performed by Volgograd State Technical University, including use of computerized simulation to optimize design and features of ASVP/ASVT wires.

A report of A. V. Zvyagintsev, Chief Expert of PSJC FGC UES Innovative Developement Department, covered the issue of bringing PUE-7 standards (Electrical Installation Code) in compliance with the world practice of installing and industrially operating improved-structure (design) tower supports. Up to now, to construct and reconstruct OL, Russia still uses the designs of supports and foundations developed in 19601970, which are morally outdated and fail to provide required reliability, safety and aesthetic appeal. The Conference participants involved in the debates believe that when choosing material and design of tower supports it is still vital to consider fatigue and durability calculation of applied grades of steel and non-metal materials.

Reports of V. I. Mishin (Marketing Vice President Deputy, Forenergo LLC PO) and S. V. Bobello (Head of Overhead-line Accessories Department Development Group, JSC NTTs Elektroseti) were devoted to a special use of compression and spiral accessories with new types of plastically deformed wires, ground wearers and OPGC. A principal feature of this accessory type is that it includes elements directly contacting both with aluminum and steel wire parts, redistributing load among all wire elements. Spiral elements with rather high flexibility combine with wire well, and after being mounted they form a single entity, thus additionally creating a specific protective layer. In their turn, a number of comprehensive test cycles of compression accessories together with ASVP and ASVT prove that this type of clamps ensures a sustainable operation of the wire-accessories system. Bending wire stiffness and endurance strength increase, resulting in wear reduction. One of areas to apply the above design is anchorage of wires in large crossings when required bonding and wire strength are essential.

In S. V. Bobellos view, spiral type accessories are quite suitable for installing plastically deformed ASVP and ASVT wires. For illustration purposes, he demonstrated a spiral tension clamp made of several spirals joined together. Strand inner surface is coated with abrasive. If it is required to additionally protect wire in the anchorage area, the clamp is installed on a pre-coiled spiral protector. The clamp is fixed to a support with a dead-eye and
standard end accessories. Specified wire bonding strength in the clamp is min. 95 % of the wire tensile strength.

The debate participants raised their highest fears for tension clamps which shall meet PUE-7 requirements in terms of wire bonding strength in clamps at low-frequency vibrations (from 3 to 10 Hz). These objections were withdrawn by presented results of independent tests with various accessories types.
Reports of R. Z. Kaverina (Head of JSC Firma OGRES OL Engineering Center) and S. V. Trophimov (Senior Researcher, JSC NTTs FGC UES) addressed the issue of protecting wires and ground wearers against vibration. Wires and ground wearers used in overhead electric lines have inner diameter from 8 to 47 mm, their dangerous frequency range is from 4 to 150 Hz.

R. Z. Kaverina believes that it is difficult, if possible at all, to develop dampers to ensure effective damping of wire vibrations within such a wide frequency range and with a minimum number of standard sizes. Wire vibration is most dangerous in case of riming. Usually rime is deposited when air is very still, preserving a cylindrical form of the wire, but significantly increasing its diameter. Wire diameter is increased without any perceptible damping change so that wind with the same speed will cause vibration at a lower frequency. In such conditions, dampers within their normal operating range cannot handle increased received wind energy. Eventually, this leads to wire fatigue failure, accessories damage and OL emergency disconnection.

According to S. V. Trophimov, vibration dampers will cope with their task much more successfully, if wire vibration do not coincide with dampers own frequency related to vibrations due to a damping element bend. Then he demonstrated a device intended to distribute the dampers own vibration frequency equally along the entire operating frequency range. This device consists of three main elements:
1) an elastic rod,
2) a clamp aimed at fixing the elastic rod parallel to the wire,
3) two weights, each of them is stretched out along its longitudinal axis and secured in its middle across the elastic rod at one of its ends.
So far it is unknown whether this device will be used in our OL. All depend on results of its industrial operation.

R. S. Kaverina considers it necessary to develop a protection framework and a method to calculate vibration parameters for compacted wires, since their design differs significantly from ordinary AS, and standard hinging and designs of vibration dampers may not fit.

Report of S. V.Kolosov, JSC Elektrosetstroyproekt General Director Deputy (Moscow) covered issues of developing protective and functional OL wire coatings with specified physical, chemical and operational properties, in order to ensure necessary electrical and thermal conductivity, shielding against electromagnetic impacts and ultraviolet radiation.

In the report debates it was suggested to develop as soon as possible OL wire which surface is characterized by low adhesion to water, snow and ice, thus protecting electric power lines against ice and snow build-up. Nordic countries already use OL wire adjusted to remove ice from its surface by Joule heat. This wire is coated with material capable to absorb alternate current energy, its coating is thick enough to generate heat and melt ice, meanwhile the coating is located between an electric conductor and an outer conducting shell.

ASVP/ASVT wire development, final adjustment and series of additional research and tests were conducted according to minutes of PJSC Rosseti and PJSC FGC UES workshops. Results presented at the Conference of recent research, out of more than fifteen projects, give a comprehensive reply to all questions raised by operating companies.

The Conference participants generally agree that it is necessary to speed up work in the area of technical regulation and update of a whole range of standards and regulatory documents, taking into account current and long-term growth of the power grid industry.

Complete official report: http://www.cigre.ru/news/rnk/2471/

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