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WG C4.306 Insulation Coordination of UHV AC systems

 

Different countries in the world are planning and realizing UHV AC systems with operating voltages of 1000 kV and above. When planning a new power system, in particular at a new voltage level, insulation coordination (IC) is one of the most important subjects. The main task is the determination of stresses and the assessment of the strength of the system and the equipment installed.

The general procedure of IC is described in IEC 60071-1 (2006). This standard does not give precise advice regarding new voltage levels although CDV 28/195/CDV under vote provides insulation levels for Um values of both 1100 kV and 1200 kV. These insulation levels are based on both past experience available from former CIGRE work that also considered the 1000kV voltage level, and recent works inJapan,China andIndia. The research activities within previous Study Committee 33 in the topic of UHV transmission provided a good basis on overvoltages and air insulation performance to make possible the design of air insulation for both 1100kV and 1200kV highest voltage of a system.

Since 1990’s, metal oxide surge arresters have been applied to UHV substation design. IC for UHV has changed to the one based on these arresters throughout substation and transmission line. Also, gas insulated switchgears  (GIS, MTS) have been generally applied to UHV substation design.

Considering the above issues the WG will review and discuss insulation co-ordination practice in the UHV AC range taking into account the state-of-the-art technology, with special reference to surge arresters. Such a review will take into account the accumulated knowledge of various CIGRE working bodies, and will be accomplished in cooperation with SCA3 and B3. Recommendation, for application guide IEC 60071-2 (1996) and IEC apparatus standards will be proposed.

Convener: E. Zaima (Japan)

Publication: TB542: Insulation Coordination for UHV AC Systems (Published: 2013-06)