Factors for investment decision GIL vs. cables for ac transmission

This technical brochure was initiated to provide information to support a transmission line project when it is not clear if the best solution would be extruded cables or gas insulated transmission line (GIL). To evaluate options for a transmission line project is a complex task and this technical brochure gives information to form solid decisions based on the knowledge of experts from Study Committees B1-Cables and B3-Substations. In this brochure, the following issues have been addressed and investigated:  Economic parameters of UG cable and GIL installations have been identified and the relative cost structure has been given;  Typical transmission solutions of GIL and UG cables are compared;  Environmental impact such as health and safety requirements and external electromagnetic fields have been taken into account;  Technical definitions of cost factors and cost drivers have been given in order to make the solutions comparable, e.g. access and width of route, system configuration, right of way, safety aspects, case of fire, transmission losses, reactive power compensation, ageing of equipment, life cycle cost, service experiences, gas tightness, recycling of material at the end of life, CO2 emission impact (production, installation, life time), waste disposal, geographical, construction, O&M, standards and regulations;  Practical applications have been shown;  The impact of restoration cost factors in case of failure and relevant outage duration has also been covered. It is worth remembering that the aim of this brochure has not been to provide absolute costs but comparative and relative ones. It gives guidelines for the necessary case-by-case evaluations. Even if the transmission solutions presented may be typical, they are not necessarily representative. Most of the factors and economic parameters mentioned vary both according to local conditions (e.g. civil works) and time (e.g. price of raw materials). Any relative comparison (as mentioned in the executive summary) is not sufficient to obtain satisfactory general results.