Voltage uprate studies of the Irish 220 kV network to 400 kV operation

摘要

Rapid changes to the generation portfolio and demand centres in Ireland have resulted in a need forlarge increases in capacity on the transmission network. This has driven significant networkdevelopment programmes and projects in recent years. The scale of this development is unprecedentedin the evolution of the Irish transmission network and consequentially has attracted significant publicattention. Obtaining planning permits for new overhead lines is a task that is becoming increasinglydifficult. The need to continually provide additional infrastructure, whether it be road, rail or electricalfacilities has heightened the awareness amongst both the planning profession and the general public ofresulting environmental issues and impacts [1].In Ireland 220 kV single circuit lines form the backbone of the transmission grid with a relativelysmall amount of 400 kV. Most of these 220 kV lines date from the 1950s and 1960s and are anunshielded design. One innovative solution to increasing the transmission capacity is to uprating this220 kV overhead line network, by redesigning the tower head to accommodate 400 kV electricalclearances; hence maximising the use of the existing assets and rights of way for higher capacity andlower loss circuits.This paper examines two voltage uprate options currently under consideration; the conversion of theexisting 220 kV overhead lines to 400 kV operation using traditional lattice steel tower design withcomposite insulator strings and a more novel design which replaces the existing tower cross arms witha composite rigid insulator. The paper concludes with an evaluation of the merits of both designs inthe Irish context.The project was instigated by EirGrid as the first part of a two part research project. The focus of thestudy to date has been to examine the structural viability of a voltage uprate while the second part willexamine the electrical performance of the uprated line which is necessary in order to develop a fullunderstanding of the feasibility of this approach.