Elis Sutlović

Statistical analysis of particles of conductor clashing

Fire ignition as a consequence of conductor clashing has happened in many countries all over the world. These fires can cause severe environmental (forest fires) and financial damage, and even be potential life-threatening. The goal of the article is to describe the processes which occur when two live conductor clash together. The most dangerous product of conductor clashing are particles (sparks), which fall to the ground, while being hot enough to potentially start a fire. Primary, by defining of those sparks we can do the first step which would lead to the answer: “Is conductor clashing the cause of fires?” Conductor clashing was simulated in two environmental conditions. The first one was in a live low voltage electricity distribution network as line-to-line short circuit and the second one was in laboratory conditions. Al/Fe conductors of the same characteristics were used in both simulations. Simulations were recorded with high speed camera. Statistical analysis of particles and their probability density function (PDF) are presented in this paper. PDF calculation may be a part of additional criteria on power system protection adjustment.

Influence of earthing conductors on current reduction factor of a distribution cable laid in high resistivity soil

Various types of system circuit faults are possible. The most common is the phase-earth fault. During this fault, currents flow through earthing grids as well as through the earth. These currents are the consequence of electromagnetic coupling of conductors and earthing grid potentials and can be presented by current reduction factor. When earthing conductors are laid together with cables, the current reduction factor is very difficult to define. In this paper a mathematical determination model of current reduction factor is presented for the cable and earthing conductors laid in the same trench. Influence of both electromagnetic characteristics and earthing conductor geometrical characteristics as well as influence of geophysical features on the current reduction factor is analyzed in this paper.

Comparison of Aluminum and Copper Particle Critical Diameter Produced in Overhead Line Conductor Clashing

The issues of hot metal particle eruption due to overhead line conductor clashing and potentially ignition of cellulosic fuel beds under the transmission line have not been sufficiently explored although conductor clashing is often considered as fire cause. At the point where contact or electric arc between two conductors on different potentials is established, electric energy is converted into heat energy so the large amount of generated heat can cause melting and vaporization of conductor material. Some of ejected sparks will ignite and burn, while others will simply fall to the ground, cooling off on the way by convection and radiation. The critical diameter is the least diameter of the particle caused by conductor clashing that will be sufficient to ignite the biomass on the ground. The results show that the copper particles in the same conditions bring a greater ignition risk due to their higher heat capacity.

The impact of flywheel torque of refurbished generator units on the limit switching time in Croatian power system

In a refurbishment project, possible solutions for old generators in Zakucac and Peruca hydroelectric power plants (HPP), Croatia, are suggested. In the first step, transient processes caused by 3-phase and phase-earth short circuits on all connected transmission lines to Zakucac and Peruca HPPs were analysed on the different power system models. Many computer calculations of transient stability in Zakucac and Peruca HPP and dependent environment of the power system with refurbished generators in these plants were made. Since transient stability in the power system with recommended characteristics of refurbished generator units were satisfied, the impacts of smaller flywheel torque on limit switching time values were considered in a second step.