Scoping protection modifications for series capacitor projects in New Zealand´s South Island

Addition of series compensation to transmission lines will increase the power transfer capabilities of the lines. However the existing transmission line protection systems on both the compensated lines and nearby uncompensated lines can be significantly affected. The security of the protection on the adjacent lines can be compromised and both the security and the dependability of the protection on the compensated line can also be threatened. When compensation is being considered for existing lines to increase their transfer capacity, the lowest cost solution would be to retain the existing protection systems with minimum modifications. This paper describes two studies that were completed to identify the minimum upgrade work required to ensure reliable protection applications and settings considering the impact of proposed series compensation projects.