Distribution Load Flow
The PRISM dispatcher distribution load flow (DLF) is used as a dispatcher query tool for ad-hoc load flow queries, as a planning tool for in-depth network analysis, and as a basis for many advanced distribution analysis / automation applications such as Short Circuit Analysis, Switch Order Optimization, Fault Detection Isolation and Restoration, etc. The PRISM DLF operates from the same network model as that created by DASmap for all advanced applications.
The DLF is implemented to compute phase voltage magnitudes for each feeder or network node as well as phase and neutral currents for each branch (line, switch and transformer). The active and reactive losses on each branch, as well as accumulated total and per phase losses for each substation and feeder can also be computed. The PRISM DLF model is implemented utilizing Ybus Gauss solution method that uses sparse Ybus matrix and equivalent current injections to solve distribution network equations. This method has been proven to have rapid convergence rate and less memory usage for distribution networks. The DLF model applies three-phase sequence model that converts unbalanced three phases into positive, negative and zero sequence phases. After the power flow solution, sequence phases will convert back to three regular phases.
- Solve the full-sized radial (open-loop) or non-radial (closed-loop) distribution system. The feeder line sections and transformers can be three-phase, two-phase or single-phase ones in either radial or non-radial configuration. In the non-radial configuration, three-phase and non-three phase feeder sections can be allowed to co-exist in a loop.
- Solve selected zones, substations, and feeders without solving the entire distribution system model
- Compute voltages and currents for each phase for every node, feeder section and other devices.
- Compute three-phase or phase-by-phase active and reactive loads and losses for the distribution system as a whole or for individual substations, transformers, capacitors, reactors and feeders.
- Handle feeders with unbalanced loads and line impedance.
- Scale all or selected loads with a dispatcher entered scaling factor.
- Re-scale selected loads with selected power factor.
- Automatically Adjust LTC taps and associated capacitor banks to maintain specified RPDC.
- Set all or selected LTCs, associated capacitor banks and reactors in fixed or automatic control mode.
- Automatically switch line capacitors to maintain CBC objectives (for automatic mode).
- Set all line capacitors in fixed or automatic mode.
- Use real-time system configuration and operation data to set the base case for solving power flow.
- Use previously save cases or data from OSW to set the base case for solving power flow.
- Successfully determine the power flow solution for any operating condition on which the actual distribution system is stable and non-ill conditioned.
A user interface for the DLF is provided both via network one-line diagram and the DAS planning/analysis interface. The network one-line diagram or map interface may be operated in real-time mode or in Study Mode for quick and easy analysis by the dispatcher. The Planning user interface enables the planning engineer to set up different base cases, copy from the real-time configuration and operating condition or copy from a saved case and to run each analysis independently.