Classification of Bus Bars in Load Flow Analysis

A bus is a set of conductors in which electrical power flows and is then distributed to different lines.
In Power Flow Analysis, buses are classified into three main types.

They are
  • The Generator Bus
  • The Load Bus and the 
  • Slack, Swing or Reference bus
The Generator Bus
As the name suggests, the generator bus is the bus producing power.  For the generator bus, the values of P, the active power and the voltage, V are given.  The reactive power, Q and the load angle, delta should be found.

The Load Bus
The load bus consumes active and reactive power.  For this bus, the active power, P and the reactive power, Q are given.  The voltage and the phase angle should be calculated.

The Swing Bus
The swing bus is the bus which has been made to take the additional active and reactive power which are used to supply the transmission losses.  Therefore, the active and reactive powers are unknown for this bus.  Only the voltage,V and the load angle, delta are given.

Bus Type Quantities Specified  Quantities to be found 
 Generator Bus  P,V  Q, load angle
 Load Bus  P,Q  V, load angle
 Swing Bus  V, load angle  P,Q