One-line diagrams are an important means of communicating the components, relationships, and connections within a circuit or electrical system. The one-line diagram symbols presented here are commonly accepted symbols.
Ammeter
Battery
Bus Duct
Capacitor
Control Power Transformer
Current Transformer
Current Transformer with Connected Ammeter
Delta Connection
Drawout Circuit Breaker
Drawout or Plug-In Connection
Electrical Interlock
Electrically Operated
Emergency Generator
Fuse
Fuse Disconnect Terminal Block
Fused Disconnect Switch
Future Removable/Drawout Circuit Breaker
Ground
High Voltage Fused Interrupter Switch
High Voltage Unfused Interrupter Switch
High and Medium Voltage Drawout Circuit Breaker
Indicating Lamp
Key Interlock
Lightning/Surge Arrester
Load Center or Panelboard
Mechanical Interlock
Meter Center Enclosure
Molded Case Circuit Breaker
Motor
Motor Circuit Protector
Motor Rated Disconnect Switch
Non-Drawout Circuit Breaker
Normally Closed Contact
Normally Open Contact
Power or Distribution Transformer
Protective Relay w/ Device Number
Protective Relays Connected to Current Transformer w/ Device Number
