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Running power flow analysis

This guide shows you how to run power flow analysis on your single-line diagram and view the results.

Before you start

Ensure your diagram meets the requirements:

  • At least one power source (utility feed or generator) connected to the system
  • All components have valid electrical parameters (voltages, power ratings, impedances)
  • No isolated components or disconnected islands
  • Cable lengths and types specified
  • Load values entered for all loads and motors

Running the analysis

  1. Open your project in the SLD editor.
  2. Verify all components are connected properly (look for connection validation warnings).
  3. Click Run Power Flow button in the top toolbar.
  4. The analysis runs in the background and takes 2-5 seconds for typical systems.
  5. Results appear automatically on the canvas as annotations.

The engine validates your network before running. If validation fails, an error message explains what needs to be corrected.

Auto-show results feature

After a successful power flow calculation, result annotations automatically display on your diagram. The system:

  • Enables the results visibility toggle
  • Shows voltage annotations on buses
  • Displays current and loading on cables
  • Shows transformer loading and currents
  • Displays load terminal voltages and power draw

You don't need to manually enable results - they appear automatically after the first successful run.

Viewing results on canvas

Power flow results appear as annotations attached to components:

Bus annotations show:

  • Voltage magnitude (0.98 pu or 470 V depending on unit system)
  • Voltage angle in degrees
  • Color-coded severity (green, yellow, or red)

Cable annotations show:

  • Current magnitude in kA or A
  • Loading percentage (current / rated current × 100)
  • Color indicates loading severity

Transformer annotations show:

  • Loading percentage
  • HV side current (primary winding)
  • LV side current (secondary winding)

Load annotations show:

  • Active power consumption (MW or kW)
  • Reactive power consumption (MVAR or kVAR)
  • Terminal voltage (actual voltage at load connection point)

Toggling annotations on and off

To control result visibility:

  1. Look for the eye icon toggle in the top toolbar.
  2. Click to show or hide all power flow annotations.
  3. Annotations persist across sessions until you run a new calculation.

Hiding annotations clears the canvas for easier editing. Showing them again displays the same results until you rerun the analysis.

Switching between unit systems

You can view results in two unit systems:

Per-unit system:

  • Voltages shown as fraction of nominal (0.95 pu to 1.05 pu)
  • Powers in MW and MVAR
  • Best for analyzing voltage deviations

Engineering units:

  • Voltages shown in actual kV or V
  • Powers in kW and kVAR
  • Best for equipment verification

To switch:

  1. Open the power flow settings panel.
  2. Select Per-Unit or Engineering Units.
  3. Annotations update immediately to show the selected system.

Exporting debug files

For troubleshooting or detailed analysis, export the raw calculation data:

  1. Click the debug export button in the power flow results panel.
  2. The system saves a markdown file to debug-exports/pf-debug-[timestamp].md.
  3. The file contains full JSON results from PandaPower including:
  • All bus voltages and angles
  • All line and cable currents
  • Transformer results
  • System losses
  • Convergence information

Debug files help when coordinating with electrical consultants or verifying results against other tools.

Rerunning after changes

When you modify the diagram, results become stale. Stale results show in gray and include a "stale" indicator. To update:

  1. Make your changes (add components, edit properties, change connections).
  2. Click Run Power Flow again.
  3. New results replace the stale ones.
  4. Annotations update with current values and severity colors.

The system automatically reruns power flow after component property edits when results are currently visible on the canvas. Topology changes (adding, deleting, or reconnecting components) require you to manually click Run Power Flow again.

Handling calculation failures

If power flow fails to converge, you see an error message explaining the issue. Common failures:

  • No slack bus: Designate one bus as the slack bus (typically the utility connection).
  • Isolated island: Connect all components to the main network.
  • Missing parameters: Check that all components have required electrical data.
  • Numerical issues: Verify load and generation values are reasonable.

See Troubleshooting convergence for detailed solutions)

Related topics

On this page

Before you startRunning the analysisAuto-show results featureViewing results on canvasToggling annotations on and offSwitching between unit systemsExporting debug filesRerunning after changesHandling calculation failuresRelated topics