Z bus

Lesson 9 of 10 • 60 upvotes • 12:21mins

Anvesh Sameer

What is Z Bus in power system? Z bus is called the open circuit impedance matrix in circuit theory with the elements of the matrix known as the driving point and transfer impedance. It is also known as bus impedance matrix. The formation of a bus impedance matrix requires either matrix inversion or the use of involved algorithms.The Z bus is however used for short circuit studies Z denotes impedance and its reciprocal is admittance and denoted by Y. Z adds in series but not in parallel. On the other hand, Y is additive is parallel and we know that in power systems mostly loads are connected in parallel, that's why power system calculation are done in admittance matrix form Y rather than Z because it helps to simplify calculations. Once you have calculated Y, take inverse it you will find Z matrix. Z Matrix or bus impedance matrix is an important tool in power system analysis. Though, it is not frequently used in power flow study, unlike Ybus matrix, it is, however, an important tool in other power system studies like short circuit analysis or fault study. The Zbus matrix can be computed by matrix inversion of the Ybus matrix. Since the Ybus matrix is usually sparse, the explicit Zbus matrix would by dense so memory intensive to handle directly Electric power transmission needs optimization. Only Computer simulation allows the complex handling required. The Zbus matrix is a big tool in that box. Because the Zbus is the inverse of the Ybus, it is symmetrical like the Ybus. The diagonal elements of the Zbus are referred to as driving-point impedances of the buses and the off-diagonal elements are called transfer impedances