Selecting the Setting Values of Backup Protection of Overhead Lines with Branches with Taking into Account the Influence of Motor Load

The article is devoted to the problem with selecting the setting values of remote backup protection for branch substations with low-power transformers having a powerful motor load. Here is given a brief description of the problem. It’s made a description of the influence of starts and self-starts of electric motors in the branch substations and the areas of these regimes are constructed for various parameters of the motor load, its share in the total load of all transformers connected to the radial supply overhead line. The detuning coefficients of the backup protection against symmetrical short circuits are clarified, general analytical expressions are given for determining the modules and arguments of the currents from the supply substation sites, which provide a reasonable choice of backup protection parameters and, in some cases, increase its sensitivity.