Consideration to use high sil lines versus series compensation in high voltage power transmission lines

Summary

This paper describes the findings of a power transfer analysis and comparison done with the objective of investigating whether High Surge Impedance Loading (HSIL) lines are a workable option in comparison to the installation of series capacitor banks on long transmission lines. Power transfer on long transmission lines is limited by the series inductive reactance that consumes a significant amount of reactive power that could lead to voltage levels that are below the acceptable system voltage limits. A common method used to improve power transfer is series capacitor banks. Series capacitor banks are selfregulating devices that increase power transfer by increasing the production of reactive power as the real power transferred on the line increases. This makes the line electrically shorter by reducing the series impedance of the line. Same concept applies when HSIL techniques are applied: reducing the phase-to-phase separation, increasing the subconductor spacing and increasing the number of sub-conductors per bundle. The HSIL configuration that is analysed is a perfect inverted delta with 12 m as the phase-to-phase separation and 1 500 mm as the sub-conductor spacing on a 4 x Tern conductor bundle. The Motraco network was selected as a case study because the lines are longer than 200 km, supply a constant load, operate at their SIL under system healthy conditions and have series capacitor banks installed. Power System Simulations for Engineers (PSS/E) was used to compare the power transfer of the existing (as-built) lines with series capacitors against HSIL lines. The results show that HSIL lines are only comparable under system healthy conditions. Under contingency conditions their transfer capacity does not meet the load demand thus HSIL lines are not a lower cost option when compared to the installation of series capacitor banks on long transmission lines.

Additional informations

Authors

ROSS, SANTAMARIA

Keywords

High Surge Impedance Loading (HSIL), long transmission lines, voltage collapse, phase compaction, expanded bundle.