Power Electronics

Busbar

Switchgear

“One of the basic functions of switchgear is protection, which is interruption of short-circuit and overload fault currents while maintaining service to unaffected circuits. Switchgear also provides isolation of circuits from power supplies”

“Typically, switchgear in substations are located on both the high- and low-voltage sides of large power transformers. The switchgear on the low-voltage side of the transformers may be located in a building, with medium-voltage circuit breakers for distribution circuits, along with metering, control, and protection equipment”

• Power Conducting
  • Switches, circuit breakers, fuses, lightning arrestors
• Control Systems
  • Control panels, transformers, protective relays
• LV
  • < 1kV AC, 1.5kV DC
• MV
  • 3.3kV < $V$ < 33kV
• HV

  • 36kV

Faults

• Any abnormal current
• Short circuit
• Open circuit
• Ground/Earth fault
  • Current flows to earth
• Transient
  • Temporary
    • Disable component and wait to clear
  • Tree contact
  • Animal contact
  • Lightning strike
  • Conductor clashing
• Persistent
• Symmetric
  • Affects all phases equally
  • Rarer than asymmetric
  • Line-to-Line-to-Line or Line-to-Line-to-Line-Ground
• Asymmetric
  • Doesn’t affect all phases
  • Line-to-Line
    • Short circuit
    • Ionisation of air
    • Physical contact
  • Line-to-Ground
    • Physical contact
    • Storm damage
  • Double Line-to-Ground
    • Storm damage
• Bolted Fault
  • Zero impedance
    • Max prospective short-circuit current
• Arcing Faults
  • With high enough voltage
  • Relatively high impedance
    • Harder to detect with overcurrent protection