Abstract :
This paper presents two methods for power losses evaluation in electricity distribution systems (substations and feeders). The methods use only two, usually accessible, data: resistance R of particular network´s element, and the annual electrical energy flow W, passed through it. The paper presents results of the research which aim was to find dependance of thermic impulse, A=Σi2(t)·Δt, on annual electrical energy flow, W: A=ƒ(W).