Energinet has traditionally used overhead line insulators of glass on all 400 kV lines, and a mix of glass and composite insulators on 132/150 kV. In the future the focus will though be on composite insulators and it is foreseen that this will be the preferred technology.
Traditionally Denmark has been divided in relation to the requirements for the creepage distance and thus also length of insulator strings where requirements for creepage distance has increased closer to the western coast of Jutland. In the transition to composite insulators, Energinet has simply converted the requirements from glass insulators to the composite insulators and it is now time to perform an optimisation of the requirements for the insulators.
Related to the future requirements it is of vital importance to investigate, in depth, the phenomena that limits the length of the insulator string. Calculations and assesment of insulator distance for different voltage levels will be needed in order to perform an optimisation, and the project may involve a market screening visiting the different manufacturers.