Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Electrical and Computer Engineering

First Advisor

Ian Dobson


When power grids are heavily stressed with a bulk power transfer, it is useful to have a fast indication of the increased stress when multiple line outages occur. Reducing the bulk power transfer when the

outages are severe could forestall further cascading of the outages.

Phasor measurement units (PMUs) are vital elements for monitoring and control of these heavily stressed power system. This work presents a new approach to implement and utilize PMU information to monitor operational transfer capability and limits based on voltage phasor angles with respect to thermal limits of transmission lines. This work demonstrates an algorithm to obtain thresholds based on the angle and then quickly deploy PMU data to monitor stress changes due to single and multiple outages in real time to send fast notification of emergency situations. Area angle uses the topology and the synchronized measurements of angles across an area of power system to measure stress caused by outages within the area. The proposed algorithm is easy, quick and computationally suitable for real systems to capture bulk stress caused by outages and also identify local stress. This work first illustrates the idea of area angle in a Japanese test system and then explores the choice of the border buses. It further investigates the relation between area angle to area susceptance and supports the findings in two areas of the Western North American power system.

Finally, this work develops a procedure to define thresholds for the area angle that relate to the maximum power that can be transferred through the area until a line limit is reached. The algorithm finding the area angle thresholds offline and then in real time monitoring the area angle and comparing it to the thresholds after multiple outages determines the urgency (or not) of actions to reduce the bulk transfer of power through the area.

The procedure also identifies exceptional cases in which separate actions to resolve local power distribution problems are needed.

The findings are supported by testing on a 1553 bus reduced model of the Western interconnection power system.


Copyright Owner

Atena Darvishi



File Format


File Size

107 pages