BUS ADMITTANCE MATRIX - PART - 01 - FORMATION OF Y-BUS - ADVANTAGES

I-bus = Y-bus x V-bus       ----- 01

The voltages are measured with respect to ground. The equation - 01 is called nodal current equation.

It is a vector equation consisting of n scalar equations.

I-bus is the vector of the injected bus current (i.e. external current sources)

Y-bus is the bus admittance matrix

The diagonal element of each node is the sum of the admittances connected to it.

It is known a self-admittance matrix or driving point admittance.

The off-diagonal element is equal to the negative of the admittance between the nodes.

It is known as the mutual admittance or transfer admittance.

SPARSE MATRIX – Sparse mean not dense

The Y-bus is a sparse matrix. For a large power system, more than 90 % of off-diagonal elements are zero. This is due to the fact that in power system network networks each node (bus) is connected to not more than three nodes.
V-bus is the vector bus voltages measured from the reference node (i.e. node voltages.

ADVANTAGES OF Y-BUS

1. Y-bus is a sparse matrix hence (i.e. most of its elements are zero) computer memory requirements are less.

2. It is very useful in load flow and stability analysis.

3. Its formation and modification are easy.

4. Data preparation is simple.