We present a mixed-integer, linear programming model for determining optimal interconnection locations using a cost minimisation approach. Optimal interconnection and capacity investment decisions are determined under various targets for renewable penetration. The model is applied to a test system for eight countries in Northern Europe. It is found that considerations on the supply side dominate demand side considerations when determining optimal interconnection investment. Interconnection is found to be most valuable when targets for renewable electricity are set for the whole system, rather than for different regions within the system.