Voltage propagation

Voltage propagation automatically manages voltage consistency across connected components in your single-line diagram. When you set or change a voltage on a bus, utility feed, or generator, connected components in the same voltage zone update to match. This keeps your diagram electrically consistent without requiring you to manually edit every component.

Voltage zones

A voltage zone is a group of connected components that share the same system voltage. Zones are separated by transformers, which create boundaries between voltage levels.

Within a zone, all components operate at the same voltage. For example, a 480 V bus, the protection devices connected to it, and the loads fed from those protection devices are all in the same 480 V zone.

Components that belong to a zone include:

• Buses
• Protection devices (breakers and fuses)
• Cables
• Loads and motors
• Utility feeds and generators

Transformers do not belong to a single zone. Each transformer winding connects to a different zone: the primary side connects to the higher-voltage zone and the secondary side connects to the lower-voltage zone.

How voltage propagates

Voltage propagation follows a priority system. Primary voltage sources (utility feeds and generators) take priority over buses when determining the zone voltage.

When you connect a component to an existing zone:

1. The system identifies the zone's voltage from the highest-priority source.
2. If the zone contains a utility feed or generator, that component's voltage defines the zone.
3. If the zone contains only buses, the bus voltage defines the zone.
4. Loads, motors, and protection devices added to the zone automatically adopt the zone voltage. If you later edit their voltage manually, the system remembers your choice and preserves it on reconnection.

When you edit a voltage:

• Changing a utility feed or generator voltage updates connected transformer windings to match.
• Changing a bus voltage updates connected transformer windings, but only if the zone has no utility feed or generator that would take priority.
• Cables compute system voltage from the zone in real time and do not store an independent voltage value.

What triggers voltage propagation

Voltage propagation runs automatically when you:

• Change a bus voltage in the edit panel
• Change a utility feed voltage
• Change a generator rated voltage
• Connect a transformer to a bus, utility feed, or generator
• Connect any component into an existing voltage zone

You do not need to manually trigger propagation. The system handles it as part of the normal editing workflow.

Transformer voltage boundaries

Transformers create the boundaries between voltage zones. Each transformer has two voltage ratings:

• Primary voltage (top connections) - matches the upstream zone
• Secondary voltage (bottom connections) - matches the downstream zone

When you connect a transformer to a voltage source, the corresponding winding voltage updates automatically. For example:

1. You have a bus set to 13.8 kV.
2. You connect a transformer's primary side to that bus.
3. The transformer's primary voltage updates to 13.8 kV.
4. The secondary side remains at its own voltage (for example, 0.48 kV), defining the downstream zone.

Changing a transformer's primary or secondary voltage does not propagate voltage-source priority to the connected zone. The zone's authoritative source is still utility feeds, generators, or buses.

Voltage conflict detection

The system detects voltage conflicts and displays them in the validation panel. Conflicts occur when:

• A component's rated voltage does not match its zone voltage
• Multiple voltage sources in the same zone have different voltages
• A component has no determinable zone voltage (orphaned from any source)

Conflicts are severity-coded:

Multi-source conflicts (two sources at different voltages in the same zone) are always treated as errors.

Resolving voltage conflicts

When a voltage conflict is detected, you have several options:

If a conflict appears when you create a connection between zones at different voltages, the system prompts you with a resolution. You can choose to update the bus voltage to match the primary source, which corrects the mismatch and allows the connection.

For equipment rating mismatches (a load rated at 480 V connected to a 208 V zone):

1. Open the component in the edit panel.
2. Update the rated voltage to match the zone voltage.
3. The warning clears automatically.

In most cases, voltage auto-adoption handles this for you. Equipment rating mismatches typically appear only when you intentionally rate equipment differently than its zone (for example, a 600 V-rated breaker in a 480 V system).

For multi-source conflicts (two utility feeds at different voltages connected to the same zone):

1. Edit one of the sources to match the other.
2. Or insert a transformer between the zones to create separate voltage levels.

> Important: Voltage errors block power flow and short circuit calculations. You must resolve all voltage errors before running analysis.

Voltage source priority

When a zone has multiple voltage-defining components, the system uses this priority order:

1. Utility feeds and generators (primary sources)
2. Transformer windings connected from an upstream zone
3. Buses (fallback sources)

If a bus voltage conflicts with a connected utility feed, the utility feed voltage takes priority. Editing the bus voltage in this case does not cascade to connected transformers because the utility feed is authoritative for that zone.

Best practices

• Set utility feed or generator voltage first, then build downstream. Voltage propagates from sources through transformers to downstream buses and loads.
• Add transformers to create voltage boundaries between distribution levels (for example, 13.8 kV to 480 V).
• Check the validation panel for voltage conflicts before running power flow or short circuit analysis.
• When building a multi-level system, work from the source toward the loads. Set the utility feed voltage, connect through the main transformer, then set up the secondary distribution.
• If you need to change a zone's voltage, edit the highest-priority source in that zone (the utility feed or generator, not a downstream bus).

Related topics

• Connection rules - Valid connection patterns and voltage compatibility
• Understanding components - Component categories and roles
• Validation warnings - Understanding validation messages
• Transformers - Transformer configuration and connections
• Running power flow - Prerequisites for analysis