Branch

A branch represents any circuit element that connects two buses in a power system network. Common branch types include transmission lines, transformers, series capacitors, and series reactors. Branches form the edges of the power system graph and their parameters are essential inputs for all network analysis.

Key Aspects of a Branch:

• Impedance Parameters: Each branch is characterized by its series impedance, resistance (R) and reactance (X), which governs current flow, power losses, and voltage drop across the element.
• Shunt Parameters: Transmission line branches also possess shunt charging susceptance (B) from line-to-ground capacitance, and small conductance (G) representing corona and insulation leakage losses.
• Transformer Modeling: Transformer branches include complex tap ratios, series impedance, and may incorporate off-nominal turns ratios and phase-shifting angles for special control functions.
• Y-Bus Construction: Branch data is used to build the admittance matrix (Y-bus), the core mathematical structure for power flow, fault analysis, and contingency studies.
• Bus-Branch vs. Node-Breaker: In bus-branch network models, the topology is simplified so each substation is one or more buses and each connection is a single branch. Node-breaker models, by contrast, explicitly represent individual switching devices, enabling more detailed switching and topology analysis.