Q423 : Modelling a transmission line with no shield wires
Question In FCDIST, how can transmission lines that have no shield wires be modeled?
Answer Transmission lines having no shield wires can be modeled in the following way in FCDIST:
Designate a special Terminal in FCDIST to model only transmission lines having no sky wires. Specify the following data for this Terminal:
1. Specify the Energization Current for this terminal as the sum of the contributions from all transmission lines having no shield wires; 2. In the Neutral Connection frame, specify a large value for the Self Impedance, for example 999999 W, to ensure that no current returns back to the source through the shield wires; 3. Set any value for Ground Impedance, for example 0.1 W; 4. Set the Number of Sections equal to 2; 5. The Section Length field can be set to any value (for example, set 1000 ft); 6. Set the Tower Impedance field to some large value, for example 999999 W, to prevent a discharge of current there. 7. Define one phase (select an average height) wire and one shield wire using some typical conductors. This data will not have any influence on the computation; however they are required by the FCDIST program.