Abstract
This paper applies a voltage instability monitoring method based on voltage and current measurements from a transmission bus PMU on the Hellenic Interconnected System using both unstable and marginally stable scenarios, derived from the historical 12 July 2004 blackout of the Athens area. The effectiveness, selectivity and reliability of the proposed monitoring method is clearly demonstrated, allowing its integration into a System Protection Scheme with direct load shedding. It is shown that the proposed instability detection and control scheme could have prevented the voltage collapse if applied at the time of the event.
Highlights
Voltage stability has been a well established area of power system research for several decades, and its theoretical aspects, underlying phenomena as well as mechanisms of instability, have been well described in the literature [1,2]
At the time of the July 2004 incident, the main generating area in the Hellenic Interconnected System was located at the northwest of the country, while the majority of the system load is concentrated at the southern part of the system, which includes the metropolitan area of Athens
The simulation of a historical voltage instability incident in a real power system was used to validate the performance of a novel on-line instability detection approach
Summary
Voltage stability has been a well established area of power system research for several decades, and its theoretical aspects, underlying phenomena as well as mechanisms of instability, have been well described in the literature [1,2]. The transition of power systems due to the market deregulation and renewable integration has resulted in power systems operating under dispatch schemes and power flow patterns, for which the systems had not been initially planned This reality brings voltage stability analysis and system protection schemes against voltage collapse once again to the forefront. A main advantage of the presented WAP system lies in the fact that it is activated based on voltage instability detection conditions and not on any predefined voltage thresholds This is an important factor providing selectivity to the protection scheme considering the constantly changing network conditions. The simulated incident is used to demonstrate the operation of the proposed voltage instability detection method, followed by the activation of the load shedding scheme in the area of Athens available at that time.
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