FORMATION OF YBUS MATRIX
YBUS can be formed using two methods namely.
- Direct inspection method
- Singular transformation method
1. Direct Inspection Method
Let us consider a two node system connected with the reference node-0 having respective impedances between them as shown here.
The admittances corresponding to the impedances as marked in figure will be –j10 (between node-0 and 2) and –j2 (between node-0 and 1) respectively.
Using direct inspection method, we conclude that the order of YBUS will be 2 × 2 matrix and given by
The eqn. (i) and (ii) relating bus voltage variable to injected current into the transmission system variable are linear algebraic simultaneous equation with complex coefficient.
This linear equations of algebraic can be solved analytically with the help of Cramer’s rules to find unknown bus voltage V1 and V2 if the injected current variable I1 and I2 are known.
In load flow study the bus data contains information about power not about current and hence eqn. (i) and (ii) are not useful in present state format in load flow study.