Comparison of different thermal models for optimized dimensioning of HV cable cluster grids as means of efficient integration of large scale renewable DER

Abstract

As part of the ongoing grid extension planning to be performed in the distribution grid of E.DIS Netz GmbH, three (n-0) feed-in cable cluster grids shall be built galvanically separated from existing overhead lines on 110‑kV-level. Per definition these grid topologies shall exclusively serve for grid integration of large scale renewable distributed energy resources (DER). With these rather unique conditions in mind, several studies by E.DIS Netz GmbH and Technical University Berlin were performed, focusing on transient behaviour of cable and soil through thermal modelling, with the aim of enhanced current rating and CAPEX-optimized cable configuration. The main purpose of this paper is to give a summary of the conducted studies through a comparison of the applied time-sensitive thermal model approaches and their results for cable dimensioning. It was found that simplified and adjusted methods based on IEC standards lead to applicable results with remarkable potential for improved current ratings when referred to classical methods concerning steady-state conditions, while more sophisticated models including hydrology and heat transfer in soil will enhance simulation accuracy and furthermore enable optimized configuration for the herein specified conditions of separate feed-in cable cluster grids.