For Ukraine, coal is the most important factor for ensuring its energy security, therefore, its political independence. There is every reason to believe that importance of coal production will grow with time not only in energy sphere. Other areas of management (metallurgy, chemistry, etc.) are also closely related to coal industry. Coal industry gains in strategic importance more often drawing attention of Ukrainian government.

    In November 24, 1992 the Law on labour protection was adopted in Ukraine. It defines the basic principles of state policy in this direction and proclaims as a priority life and human health. Electric shock fatal accidents are amount 4% of the total number of accidents at mining enterprises. Statistic analysis held by institutes of MakNII and DonNTU for the period from 1991 to 1998 shows that during this time at coal mines of Ukraine 98 cases of electric shock fatal accidents were occurred. 73.5% of electric shock cases in installations over 1200 V were taking place of which: at exploitation of cable networks - 25.5%, at start-up and switching equipment - 18.4%, in locomotive haulage networks - 18.6%. According to MakNII statistics from 1990 to 1997 electrical sources were the reason of 30 explosions of methane-air mixture and coal dust in Ukraine mines. On average, every 317 days explosion is occurred at Ukraine mines as a result of short circuits (SC) in cable network. In addition, significant part of endogenous fires is happened because of electrical equipment faults. Researches show that on average 66 fires occur because of short circuits and failures of crash protection systems each year in the mines.

    The data show that security problem of human supporting and operating electrical equipment of coal mines remains unresolved. It is known that in many cases pre-emergence short circuit in the mine electrical network comes from current leakage to ground. Reliable methods development of these preconditions (leakages) eliminating is actual scientific challenge. In this regard, so as relevant is improvement of methods for assessing dynamic factors accompanying emergency of single-phase leakage (instant value of leakage current, its energy characteristics, etc.) as well as the factors associated with emergency network switching-off (EMF influence for motors rotation, for example). Thus, issues of reliability improving and security of electrical supply systems at exploitation of coal-mining regions remain valid.  

   Subject of research is factors determining danger threshold at the local network in emergency.

    Task of research is development of mathematical model for system “local network – human”, that allows to obtain integral index of danger threshold at networks taking into account alternating of three emergency stages including transients in its bounds.

   In the basis of assigned problems solution lays mathematical models of supply system of coal-mining region, its grounding network, compensating devices, nonlinear throttles and motors rundown. Methods of symmetrical components, node potentials and equivalent transformation were applied at mathematical model development. Linear systems integration was implemented, as a rule, by classical synthesis method. Non-linear models were investigated by Runge-Kutt numerical integration method.