Thiết kế và kiểm tra của polymer

Từ một vài năm, hãm với polymer-nơi ở đã được có sẵn trên thị trường để phân phối và hệ thống điện trung thế. Trong những năm gần đây, điều này loại hãm đã được đưa ra cũng trên cao hệ thống điện áp lên đến và bao gồm 550 kV. Tuy nhiên, công tác tiêu chuẩn hoá quốc tế xa phía sau này phát triển nhanh và nhiều hiện thiết kế với polymer-nơi ở cho highvoltage hệ thống chỉ được thử nghiệm theo các tiêu chuẩn IEC hiện hành, IEC 99-4 năm 1991, trong đó nói chung chỉ bao gồm hãm với sứ nơi ở. ...
Nội dung trích xuất từ tài liệu:
Thiết kế và kiểm tra của polymer DESIGN AND TESTING OF POLYMER-HOUSED SURGE ARRESTERS by Minoo Mobedjina Bengt Johnnerfelt Lennart Stenström ABB Switchgear AB, Sweden 1. INTRODUCTION Abstract Since some years, arresters with polymer-housings 1.1 SHORT HISTORICAL BACKGROUND have been available on the market for distribution Surge arresters constitute the primary protection for and medium voltage systems. In recent years, this all other equipment in a network against overvoltages type of arresters have been introduced also on higher which may occur due to lightning, system faults or voltage systems up to and including 550 kV. switching operations. However, the international standardisation work is far behind this rapid development and many of The most advanced gapped SiC arresters in the middle existing designs with polymer-housings for high- of 1970s could give a good protection against voltage systems have only been tested according to overvoltages but, the technique had reached its limits. the existing IEC standard, IEC 99-4 of 1991, which It was very difficult, e.g., to design arresters with in general only covers arresters with porcelain several parallel columns to cope with the very high housings. energy requirements needed for HVDC transmissions. The statistical scatter of the sparkover voltage was also The existing IEC standard lacks suitable test a limiting factor with respect to the accuracy of the procedures to ensure an acceptable service protection levels. performance and life time of a polymer-housed surge arrester. In particular, tests to verify the mechanical Metal-oxide (ZnO) surge arresters were introduced in strength, short-circuit performance and life time of the mid of and late 1970s and proved to be a solution the arresters are missing. to the problems which not could be solved with the old technology. The protection level of a surge arrester In this report, different design alternatives are was no longer a statistical parameter but could be discussed and compared and relevant definitions and accurately given. The protective function was no tests procedures regarding mechanical properties of longer dependent on the installation or vicinity to other polymer-housed arresters are presented. Necessary apparatus as compared to SiC arresters which design criteria and tests to verify a sufficiently long sparkover voltage could be affected by the surrounding life-time as well as operating duty tests to prove the electrical fields. The ZnO arresters could be designed arrester performance with respect to possible energy to meet virtually any energy requirements just by and current stresses are given. The advantages of connecting ZnO varistors in parallel even though the silicon insulators under polluted conditions are technique to ensure a sufficiently good current sharing, discussed and thus energy sharing, between the columns was sophisticated. The possibility to design protective Finally, this report presents some new areas of equipment against very high energy stresses also applications which open up due to the introduction of opened up new application areas as, e.g., protection of polymer-housed arrester designs. One such is series capacitors. protection of transmission lines against lightning/switching surges so as to increase the The ZnO technology was developed further during reliability and security of the transmission system. 1980s and in the beginning of 1990s towards higher voltage stresses of the material, higher specific energy absorption capabilities and better current withstand strengths. 1 For presentation at the GCC CIGRÉ 9th Symposium, Abu Dhabi, October 28-29, 1998 New polymeric materials, superseding the traditional and additional, non-frequent, abnormal stresses, e.g.. porcelain housings, started to be used 1986-1987 for • Temporary overvoltages, TOV distribution arresters. At the end of 1980s polymer- • Overvoltages due to transients which affect housed arresters were available up to 145 kV system voltages and today polymer-housed arresters have been -thermal stability & ageing accepted even up to 550 kV system voltages. -energy & current withstand capability -external insulation withstand • Large mechanical forces from, e.g., earthquakes Almost all of the early polymeric designs included • Severe external pollution EPDM rubber ...