7th Sem

Electrical Engineering Department

Batch – B1 (2014 Batch)

Abhishek Choksi

(140120109005)

Inter Connected Power System (2170901)

ALA Presentation

On

“Static Load Flow Equations & Bus Classifications ”

Prepared By: Guided By:

Prof. Grishma Pipaliya

Gandhinagar Institute Of Technology

Introduction

• Load flow studies or Power flow studies is the analysis of a power system in normal steady state condition.

• Load flow studies basically comprises of the determination of

• Voltage

• Current

• Active Power

• Reactive Power

Static method

• The following variables are associated with each bus:

• Magnitude of voltage(V)

• Phase angle of voltage(δ)

• Active power(P)

• Reactive power(Q)

• The load flow problem can solved with the help of load flow equation(Static load flow equation).

• The bus admittance matrix is given by:

• In general the equation for bus-1 can be written as:

I1 = Y11V1+Y12V2+Y13V3

• For bus-2 and bus-3 we can write:

Y21V1+Y22V2+Y 23 V3=I2

Y31V1+Y32V2+Y 33 V3=I3

• So Ii=∑ Yik Vk where i,k=1,2,…,n

So complex power is denoted as

• In polar form we can write

• The equation is written as:

• Real and reactive power expressed as:

Bus Classification

• A bus is a node at which many Transmission lines, Loads Generators are connected.

• It is not necessary that all of them be connected to every bus.

• Bus is indicated by vertical line at which no. of components are connected.

• In load flow study two out of four quantities specified and other two quantities are to be determined by load flow equation.

• Depending upon that bus are classified.

Flow chart

Load bus or PQ Bus

• A buss at which the Active power and reactive power are specified.

• Magnitude(V) and phase angle(δ) of the voltage will be calculated.

• This type of busses are most common, comprising almost 80% of all the busses in given power system.

Generator bus or P-V bus

• A bus at which the magnitude(V) of the voltage and active power(P) is defined.

• Reactive power(Q) and Phase angle(δ) are to be determined through load flow equation.

• It is also known as P-V bus.

• This bus is always connected to generator.

• This type of bus is comprises about 10% of all the buses in power system.

Slack Bus

• Voltage magnitude(V) and voltage phase angle(δ) are specified and real(P) and reactive(Q) power are to be obtained.

• Normally there is only one bus of this type is given in power system.

• One generator bus is selected as the reference bus.

• In slack bus voltage angle and magnitude is normally considered 1+j0 p.u.

References

• Power supply system by nagraj kothari

• Interconnected system by D.M Patel