This dissertation presents a new alternative type of object-oriented load-flow called Segflow. Segment objects are used to support the modeling of individual types of power system equipment. Current and voltage trace techniques are used by Segflow to bind Segment models in support of Kirchoff’s laws. Affiliation objects and the Target Voltage method are used to bring the solution of the Segflow model to the solution of the power system network. An example for modeling a simple transformer is given along with the solution results for a collection of common power system models. ‘ Analysis of the Target Voltage method and simulation results show that Segflow is capable of consistently solving the nonlinear load-flow problem. The object-oriented layout of Segflow provides very distinct modeling advantages. Power system modeling is from the perspective of each equipment’s model. Rather than force all equipment models into large sets of equations to be solved simultaneously by an equation solver, Segflow allows component models to remain intact and independent as Segment objects. Each Segment has a one-to-one correspondence with some piece of equipment in the respective power system which is maintained in the system solution. The behavior of a Segment can be evaluated throughout the load-flow process. An important feature of Segflow is the object-oriented design enabling new equipment models to be added into the Segflow environment as autonomous objects. New models are created from the Segment class and their inputs and outputs are always relative to the same Segment attributes. Because all Segment objects are derived from a Segment modeling class and all Segments are treated the same by Segflow, many types and varieties of power system equipment models can be easily created. A Segflow application is a collection of interacting objects whose interactions lead to a load-flow solution. Segflow is an interesting alternative to classical approaches for solving the load-flow problem with large sets of simultaneous nonlinear equations. It also adds new aspects to the application of object-oriented design in load-flow analysis. / Ph. D.