Using modern software tools, such as Matlab / Simulink, can significantly simplify the analysis of various complex systems. Matlab scripts allow you to automatically run Simulink schemes with changing various parameters.
m-file, modeling in Matlab, script for Matlab, relay protection calculations in Matlab.
In addition to the previous article, we will consider an example of compiling a network model with isolated neutral. Consider the simplest power line with one-way power supply (Fig. 1). It is necessary to draw up a power transmission model that will give out currents and voltages at the beginning of the line in short circuit modes and in single-phase earth fault modes.
The phase coordinate method allows you to simulate networks with isolated neutral. In Russia, networks of 6-10-35 kV (sometimes 110 kV) operate with isolated neutral. Such networks are accompanied by small currents and significant overvoltages during single-phase earth faults.
According to the “Electrical Installation Rules”, one full transposition cycle should be performed on overhead power transmission lines with a voltage of 110-500 kV and a length of more than 100 km to limit asymmetry of currents and voltages.
Consider an example of compiling a power transmission model using the phase coordinate method. In fig. 1 shows the power transmission, a mathematical model of which must be compiled. It is necessary to determine the currents in the short circuit mode at the beginning of the line.