# Load Flow Studies Important Points

- 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**

- 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.

- Comprise the
- 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

**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, Î´** - Without Slack bus, Load flow will not possible.

**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**

- Maintain the Voltage level to achieve the desired
**Load Bus**- Almost 80% of all the buses are Load Buses.
- Specified variable - P, Q

- 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.

- Network load will be specified as
**Load Bus Matrix or Bus Admittance Matrix or Y-BUS Matrix** **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 nodes =
- 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.

- Y-Bus always a
**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.**

- As opposite of Y-Bus, Z-Bus is a

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