Estimation of Voltage Profiles Along Power Transmission Lines

In this paper, a new method which allows quick calculation of voltage profile along transmission lines during system transients, is presented. The main advantage of the proposed method over existing techniques is that line parameters and wave equations are not required in order to execute the calculation once the method is implemented for a given system. This is accomplished by developing a time series model for voltages of intermediate points along the transmission lines in terms of the terminal bus voltages. The approach is simple and very easy to implement using an existing transients simulator such as EMTP. One application of the method may be creation of movies to illustrate the propagation of fault initiated transients in a given system. The paper provides simulation results to illustrate the performance of the proposed method

I. Introduction

Power systems are routinely subjected to transients initiated by faults, switching equipment, device failures, etc. Such events may cause harm to the system due to abnormal voltages and currents created during the transient. Electrical transients programs are developed in order to be able to simulate bus voltage transients in discrete time. These programs typically formulate the solution using the nodal admittance matrix and solve for bus voltages in discrete time. In assessing the transient voltage effects on equipment directly connected to system buses, bus voltage transients will be sufficient. Although the severest overvoltages usually occur at the line terminals during switching operations or faults, there are such situations when the highest overvoltage occurs at an intermediate point along a transmission line rather than a line terminal. Line operation with metal oxide surge arresters can lead such situations during fault transients or line energizations. Determining the location of the overvoltage is important in such cases due to the insulation concerns. Thus, a method for voltage profile calculation which provides the distribution of the voltage along a transmission line during steady state or transient operation, will have to be developed.