Section I:  Real And Reactive Power Injected in a Bus

For the formulation of the real and reactive power entering a b us, we need to define the following quantities. Let the voltage at the i ^th bus be denoted by

(4.1)

Also let us define the self admittance at bus- i as

(4.2)

Similarly the mutual admittance between the buses i and j can be written as

(4.3)

Let the power system contains a total number of n buses. The current injected at bus- i is given as

(4.4)

It is to be noted we shall assume the current entering a bus to be positive and that leaving the bus to be negative. As a consequence the power and reactive power entering a bus will also be assumed to be positive. The complex power at bus- i is then given by

(4.5)

Note that

Therefore substituting in (4.5) we get the real and reactive power as

	(4.6)
	(4.7)