1.1 General 1.1 RO.1 General (ncpt) This Part 2-24 gives the requirements for planning, design and construction of overhead electrical lines with nominal voltages exceeding A.C. 1 kV operating at 50 Hz frequency. The present Part 2-24 is not applicable for existing overhead electrical lines unless specifically required by Project Specification. The power installations of overhead lines, that are in different stages of design or construction, can be finalised in conformity with the standards in force at project beginning. For the application of this standard for specific requirements relaring to modernization, increasing safety and transport capacity of existing overhead lines, reference shall be specified in the Project Specification. At the same time, the correlation between relevant regulations and associated standards shall be established in the Project Specifications. The extension of existing electrical lines is considered as new overhead lines, except the junction points that shall be detailed in the Project Specifications. 1.2 Field of application 1.2 RO.1 Overhead electrical lines with insulated conductors (ncpt) This Part 2-24 is applicable for the design and construction of overhead electrical lines with insulated conductors where the internal and external clearances can be smaller than those specified in Part 1 (SR EN 50341-1:2013).