An electrical power distribution monitoring system is provided for a power distribution line (4) having a plurality of sections with a plurality of electrical loads (6a-e, 7, 25, 26) connected to the power distribution line to form a power distribution network. The monitoring system has at least one sensor (8, 10, 27, 28) for at least one present electrical value at at least one point of the network, and calculating means (14, 16, 17) arranged to estimate electrical values for at least one section of the line in dependence on both of present electrical values measured by the sensor and data relating to past power consumption by loads connected to the line. Improved prediction of actual conditions in the distribution line can be obtained.