NG TGN(E) 166 PDF

This Technical Guidance Note gives the computed 50 Hz electrical parameters for double-circuit overhead lines, for use in electrical network studies. It is intended that future issues of this document will also include cables, transformers and other plant.

The factors of line construction which influence the electrical parameters are detailed and an indication of the sensitivity of some of the electrical parameters to changes in these factors is given in Appendix B. Since, in practice, National Grid overhead lines are normally untransposed (except where one line is teed into another, where phasing changes sometimes occur), and may not have a 'Standard' phasing of the six phases on the tower, examples of the sequence parameters (both sequence self- and mutual-parameters) are given in Appendix C, for an L6 standard tower construction, as a comparison with the fully-transposed parameters . It should be noted that, for most electrical network studies (which assume no interaction between the phase sequence networks), the use of fully-transposed line parameters is perfectly acceptable, introducing errors of less than 0.2% in the magnitudes of the positive-phase-sequence impedances and no errors in the zero-phase sequence impedances for the circuit phasing