Digital protection of advanced series compensators

Fixed series compensators (FSC) are widely used in long transmission lines, as they can increase the power flow and the stability of the network. However, they cannot adapt their characteristics to changed network conditions. Contrary to FSC, controlled advanced series compensators (ASC), as flexible AC transmission system (FACTs) devices, can control the power flow in the line. Additionally, they can damp power oscillations as well as influence network conditions similarly to static VAr compensators (SVC). Due to ASC particular characteristics, the protection must encompass some additional features as compared with FSC. Furthermore, digital ASC controls can quickly adjust the line impedance which offers the possibility that ASC protection influences the ASC control to prolong operation in case of overloads. The world first ASC is installed as a three phase scheme in the substation in Kayenta, Arizona, USA