CPV code 45315500 designates Medium-voltage installation work in the Common Procurement Vocabulary (CPV 2008), the EU classification used to describe the subject of public contracts.
45315500 is a leaf code — the most specific level of its branch — so it can be used directly as the main CPV code of a contract notice. If it does not quite fit, check the neighbouring codes under 45315000 (Electrical installation work of heating and other electrical building-equipment).