Author

Aseem Rambani

Date of Award

8-2012

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Electrical and Computer Engineering

Advisor

Mohamad Musavi

Second Committee Member

Paul Villeneuve

Third Committee Member

Nathan Weise

Abstract

With advancements in the field of power systems, it has become easier to calculate the flow parameters in transmission lines. The temperature of conductors is a crucial parameter in determining the line impedances and percentage loadings. Many researchers and power utilities have adopted power system models which take into consideration variations in temperature to calculate the change in impedances for load flow, but very limited research has been performed to investigate the impact of line loadings on the conductor temperature variations. The effect of transmission line temperature variations, resulting from loading and weather conditions changes, on a power system’s steady state and dynamic performance is studied on a 39 bus system model. The steady-state and dynamic stability simulations results of a 39 bus system for constant line impedance (the traditional simulation practice) are compared to the results with estimated, but realistic, temperature varied line impedances using Positive Sequence Load Flow (PSLF) software. The enhanced line impedances will affect the thermal loading levels and voltage profiles of buses under steady state response, while the dynamic results will show improved damping in electromechanical oscillations at generator buses. The steady state parameters (thermal loading levels, voltage profiles and active power losses) are calculated by performing power load flow analysis and the findings in a simplified system model (that does not link the line resistance to the temperature) can be significantly different (close to 10% in these simulations) from the percent loading obtained from an enhanced system model that synchronizes the line resistance with the line current flow. In dynamic simulations, the impact of tripping a line or a three phase symmetrical fault is studied to analyze damping parameters of generator’s rotor angle and speed. The post fault damping is found to be improved considerably in the enhanced model. Since the loading patterns vary a lot with time and seasons, a well-equipped EMS can predict the varying patterns of transmission line loadings which in turn can become a very useful tool to predict the transient response by calculating the critical clearing angles for relay settings on regular basis.

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