Load Flow Studies Important Points

1. Load Flow Studies need to maintain the smooth operation of network system by resolve the given problems:
   
   
   • Load Flow Problems
   • Optimal Load Scheduling Problem
   • System Control Problem


2. In Load Flow Studies, we study about :
   • Comprise the magnitude & phase angle of Load bus voltage
   • Reactive powers at Generator buses
   • Real & Reactive power flow in Transmission lines.


3. Three types of Bus used in Load Flow Studies
   • Swing Bus or Reference Bus or Slack Bus
   • Generator Bus or Voltage Controlled Bus or PV Bus
   • Load Bus or PQ Bus


4. Slack Bus
   • A bus which supplies the additional Real and Reactive power to recover the transmission losses.
   • Generator bus must be selected as a Slack bus.
   • Slack Bus usually numbered as a BUS 1 and assigned to 1 p.u.
   • Specified variable -  V, δ
   • Without Slack bus, Load flow will not possible.


5. Generator Bus
   • Maintain the Voltage level to achieve the desired Reactive power injection.
   • Almost 10% of all the buses are Generator Buses
   • Specified variable - V, P


6. Load Bus
   •  Almost 80% of all the buses are Load Buses.
   • Specified variable - P, Q


7. If two buses ith Bus and kth Bus are connected then
   • Active power flow always from leading angle bus to lagging angle bus.
   • Reactive power always flow from high potential bus to low potential bus.
   • If there is no potential difference between them, no Reactive power will flow.
   • If there is zero phase difference between both buses, Active power will not flow.


8. Network load will be specified as Load Bus Matrix or Bus Admittance Matrix or Y-BUS Matrix


9. Y-Bus Matrix
   • Y-Bus always a square matrix (n x n).
   • Y-Bus is preferred for load flow studies because it is a sparsity matrix (more number of Zero elements are present )
   • Sparsity matrix are required less memory due to present of Zero element.
   • If the sum of all elements in each row of Y-Bus matrix is zero than corresponding Y-Bus is not having shunt elements.
   • In a given (n x n) Y-Bus matrix:
     • Total number of nodes = (n+1)
     • Including ground or reference node.
   • Total Number of Transmission Lines = No. of Non-zero element present either in upper triangle or lower triangle.
   • If degree of sparsity is inversely to  No. of transmission lines, then it decreases and No. of transmission line will increases.
   • If shunt capacitance/inductance are added in network, its only effects on diagonal elements of Y-Bus, off-diagonal elements remain same.


10. Z-Bus Matrix
    • As opposite of Y-Bus, Z-Bus is a Full matrix.
    • Z-Bus is use in short circuit analysis because it will give more information about non zero elements.