Changes of electric traction network with regulated and not-regulated reactive power compensation units (CU) are required due to switching on the reactive power static generators at the AC electric traction network sectioning points the specifying calculations of the reactive power. The method of calculation of power losses in the traction network with regulated and not-regulated cross capacity compensation units at the sectioning point was developed. The main positive effect of CU at the sectioning point is increasing of the carrying capacity of the railroad sections. However, calculation of CU effectiveness for reduction of electric power losses, as well as calculation of continuously controlled CU requires appropriate calculations. It is demonstrated that CU effectiveness at the sectioning points of reactive power compensation is reduced in connection with distribution of the draft load; CU regulation effectiveness is also reduced as a response to increase of the carrying capacity of the railroad section, which allows assessing the proposed calculation formulae. Presented examples of calculation for the actual baseline data demonstrate that full losses in the traction network (assumed as 100%) can be reduced by using of CU of the sectioning point up to 21% maximum with continuously controlled units and up to 13.4% with uncontrolled CU. As automatics of the reactive power static generator is designed for increasing the carrying capacity of the railroad, its operation frequently complies with the reactive power overcompensation regime when losses in the traction network are increased.