Summary

Icing of technical constructions is a phenomenon observed every year in Bulgaria. The geographical location of the country with respect to the ways of the Mediterranean cyclones is exceptionally favourable for intensive icing process leading frequently to heavy accidents of various technical constructions (power electric lines, antennae, mast etc.). The last case of such a heavy damage was in 20-30 November 1998. The heaviest icing conditions are in the mountain regions and in Northeast Bulgaria.

The icing investigations in Bulgaria began in 1949 of the mountain meteorological station Cherni vrach (2286m). Later a special ice measurement device was mounted and some field investigations in the region of this peak were carried out. The greatest rime-ice load ever measured in Bulgaria was registered here—55 kg/m.

Systematic observations of the icing process and the ice depositions have been launched in some meteorological stations later in the years.

These investigations were directed to the physical describing of the icing process and estimation of the meteorological conditions in cases of icing.

Modeling of the process

A physical-statistical model for assessment of the radius and the mass of the ice depositions on the basis of the available weather information has been developed. The model uses also three experimental found correlations between the weather data and some required input data, which are not routinely measured.

Icing conditions in Bulgaria

Data from 6 mountain weather stations and about 30 meteorological stations in the low parts of the country have been used for investigation of the meteorological conditions in cases of icing. Information for damages on the power distribution lines has been added also