Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Electrical and Computer Engineering


Electrical Engineering

First Advisor

Ian Dobson


Power systems are frequently exposed to large transfers of power between areas, which can increase the risk of voltage stability problems and blackout. In addition, multiple outages are more likely to occur during severe weather and cyber physical attacks, which can weaken the power system and also increase the risk of voltage stability problems and blackout. To address these problems, it is desirable to be able to quickly monitor voltage stability online for corridors vulnerable to voltage stability problems. It is useful to do this monitoring without running simulation or estimate the state because power systems are very complex and there is not enough time for running simulation for all the possible multiple outages, and the state estimator may not converge for some severe outages.

This thesis proposes two new methodologies for a fast online evaluation of voltage stability margin across several transmission lines and under multiple contingencies. The first methodology is based on the voltage across area reduction, and the second is based on the preservation of the complex power of the transmission corridor. Those methods are based on synchrophasor measurements, giving the operators a fast indication of voltage stability problems that is independent of state estimation. In addition, this thesis proposes a new voltage stability index that is tracking the maximum power that the corridor with multiple lines can transfer.

Current methods of voltage stability monitoring with syncrhophasor measurements work for a load supplied by a corridor with a radial single line. However, many practical situations involve load supplied by more complicated corridors with multiple transmission lines. Thus, this thesis shows how to reduce multiple corridors to a closely equivalent radial corridor, including the variation of all loads that are connected to the corridor. The monitoring method can easily accommodate changes in the generator reactive limits. Furthermore, we tested these methods with satisfactory results in several systems, including a real power system, and compared it with commercial software, obtaining excellent results.


Copyright Owner

Lina Marcela Ramirez Arbelaez



File Format


File Size

103 pages