The main objective of this paper is to build a computational model that would be sufficiently simplified for practical applications and would be able to consider the impact of switching a single compensatory power on the active network losses. This work demonstrates that such a model can be created by a linear transformation of the network scheme. Moreover, this model can be successfully used for the creation of convenient practical criterion at the operation of compensatory devices with the purpose of minimizing active losses. The criterion are necessary for operation of steady state in two cases: in the first place to return the voltage in the admissible range choosing the compensatory device for switching of nodal compensatory power which provides sufficient sensitivity of electrical network operation at the possible minimal increases of looses in consideration of auxiliary losses in the compensatory device; in the second place for the decreasing the electrical network power losses while remaining inside in the admissible voltage range in the case when increase or decrease of the nodal compensatory power does not lead to the voltage leaving the admissible range.