Wide Area Voltage Regulation & Protection

A very promising wide area voltage protection (V-WAP) solution to face EHV voltage stability and system security problems is presented. Its unique ability is mainly due to an effective co-ordination with a wide area voltage regulation (V-WAR) modern system where the secondary and tertiary voltage regulations (SVR and TVR respectively) operate according with their hierarchy. Evidence is given to the practical feasibility and the simplicity in defining and developing a wide area voltage protecting solution, very effective to eliminate the risk of voltage collapse. The main simplification comes by the already existing and appropriate network subdivision in to areas given by the operating secondary voltage regulation which also fixes the areas of the protection scheme intervention and gives, in real time, their control efforts for voltage support. On this base, a voltage stability index is proposed to operate the area load shedding according with simple and incontrovertible control logic. Dynamic simulation results related to North Italy power system shows the effectiveness of the proposed protection scheme that minimizes the load shedding amount to achieve the continuity and stability of the controlled power system, in front of a ramping load increase. The case the V- WAP has to operate alone, without the presence of any automatic voltage control system on the protected area, is also considered and analysed. In this case alternative protection functionality, less effective with respect to the case with V-WAR, is proposed and the simulation results demonstrate its interesting system security increase.