Understanding components

Electrical components perform different functions in your power system. Understanding component categories helps you build correct diagrams.

Component categories overview

Power sources:

Generate or supply electrical power
Utility feeds, generators
Power flows out

Distribution:

Route power to loads
Buses, transformers, cables
Change voltage or connect points

Protection:

Protect conductors and equipment
Breakers, switches, fuses
Interrupt fault current

Loads:

Consume electrical power
Motors, lighting, equipment
Convert electrical to mechanical or other energy

Power sources (utility, generators)

Utility feed:

External grid connection
Infinite bus assumption
Short-circuit capacity specified by utility
Typically one per facility (sometimes two for redundancy)

Generator:

On-site power generation
Emergency backup or primary power
Finite fault contribution
Synchronous or induction type

Sources inject power into the system. At least one source required for analysis.

Distribution (buses, transformers, cables)

Bus:

Common connection point
Multiple components connect
No voltage change
Distributes power to feeders

Transformer:

Changes voltage level
Isolates voltage systems
Impedance limits fault current
Two or three windings

Cable:

Conducts power between points
Voltage drop based on impedance and current
Ampacity limits current capacity
Various types and sizes

Distribution components route power from sources to loads.

Protection (breakers, switches, fuses)

Circuit breaker:

Resettable overcurrent protection
Thermal-magnetic or electronic trip
Rated by voltage, current, interrupting capacity
Can be opened/closed remotely

Fuse:

One-time overcurrent protection
Current-limiting for fault current reduction
Must be replaced after operation
Higher interrupting capacity than breakers typically

Switch:

Isolation and transfer switching
Single-throw (Closed/Open) or double-throw (Throw A/Throw B/Open)
Open/inactive throws block power flow
Includes rated current and short-circuit interrupting rating

Protection devices prevent damage from overload and short-circuit.

Loads (motors, lighting, equipment)

Motor:

Converts electrical to mechanical energy
Induction or synchronous type
High starting current (5-8× FLC)
Special NEC sizing rules

Generic load:

Any other electrical equipment
Lighting, heating, electronics
Steady-state current
Standard NEC sizing

Loads consume power - the reason electrical systems exist.

How components connect

Radial topology (most common):

Utility → Breaker → Transformer → Bus → Breakers → Loads

Power flows one direction from source to loads.

With redundancy:

Utility A ─┐
          ├─ Double-Throw Switch → Distribution
Utility B ─┘

Two sources with automatic switching.

With generation:

Utility ──┬─→ Main Bus ─→ Loads
          │
Generator─┘

Utility and generator feed common bus.

Component lifecycle

Creation:

Drag from toolbar and drop on canvas.
Component appears with default properties.
Edit properties as needed.

Configuration:

Select component.
Edit panel opens.
Set ratings, voltages, and other properties.
Apply changes.

Connection:

Create connections to upstream and downstream components.
Define power flow paths.

Analysis:

Run power flow or short-circuit.
View results on component.

Modification:

Update properties as design evolves.
Rerun analysis to verify changes.

Deletion:

Select and press Delete.
Connections automatically remove.

Component naming

Components auto-generate names on creation:

"Bus 1", "Bus 2", "Bus 3" for buses
"Cable 1", "Cable 2" for cables
"Transformer 1" for transformers

Rename components to meaningful names:

"Main 480V Bus" instead of "Bus 1"
"Chiller Feed Cable" instead of "Cable 5"

Clear names improve diagram readability and communication.

Electrical concepts - Power system fundamentals
Connection rules - Valid connection patterns
Components - Detailed component documentation