BEREZNYAK The development of mathematical model of processes which are proceeded in the protection elements in case of arc short closures in nets 0,22-0,38 kV Abstract

	Bereznyak Yuliya Vladimirovna
Theme of master's work: *"The development of mathematical model of processes which are proceeded in the protection elements in case of arc short closures in nets 0,22-0,38 kV"*

Leader of work: Alexander Kovalyov - professor, leader of department Electrotechnical systems of power- consumption

Abstract

The scientific direction operates within the limits of the state budgetary work “Increase of efficiency of systems of electrosupply and power consumption” at Donetsk national technical university ( Н 27/2000). So, new principles are developed to the estimation of efficiency of the electric protection, considering time its operations and fire-dangerous consequences of the short circuits, accompanied by an electric arc.

In the basis of their usage as one should mathematical modelling process of functioning of system of electric protection in view of its time of action and burning through effect of an electric arc at short circuits, and also using of the analytical expressions providing an opportunity of computer forecasting of fire danger of short circuits. The offered technique allows revealing potentially fire-dangerous sites of a network, as at a stage of its designing, and whiling in service. For these sites should be changed parameters or type of protection against short circuits, either type or section of electroposting and devices of protective switching-off are used also.

For practical realization of results of mathematical modelling process of functioning of electric protection and selection of a fireproof combination of parameters of protection and wirings, in view of a range of disorder of protective characteristics and characteristics burn, it is developed by the relay spark-protection which serves for effective electric and fire protection in systems of electrosupply 0,38/0,22 кВ .

Practice of operation of electric equipment has shown, that there are consumers of the electric power, for whom usual means of protection in emergencies it is not enough . First of all, it is a question of the refrigerating, computer and office equipment located, as a rule, in inhabited and public buildings where there is an opportunity of occurrence of spark categories in the weakened contact connections or through the damaged isolation between a phase and zero wire. Because of contact connections gradual heating to which usual means of protection do not react, occurrence of a fire is possible. It is most dangerously in off-hour a time off, at absence of the working personnel [3].

For struggle against this lack which can become the precondition to an emergency, faculty EPG it is developed spark-protection the relay which should react to high-frequency components of the current which arise at specified spark categories [4]. One of the major elements of such relay is the gauge reacting to occurrence of spark categories.

In the given work to be put the research problem of dynamic properties of the gauge spark-protection which contains:

          - the equivalent generator presented by a source of a voltage u(t) and internal resistance r0, L0;
            - a resonant contour r1, L1, C2 ;
            - low-frequency filter C3, C4 ;
            - resistance of loading R.

The essence of research of properties of dynamic system consists of finding and investigating decisions of system of the differential equations (1) at the set entry conditions.

The last, in turn, can be certain as a result of the analysis of the established mode before switching for what the decision of system (2) is necessary.

Considering that the investigated scheme represents system of the fourth order, the decision is unequivocally certain only at presence of sixteen entry conditions. Four of them are known from the decision of system (2). These are independent entry conditions, that is value of constants of time at t = 0. Others twelve should be found from additional system of the equations which is resulted below (3). Thus all values of functions in the equations are considered during the moment of switching (t=0) .

1. Смелков Г.И. Пожарная опасность электропроводок при аварийных режимах. – М: Энергоатомиздат, 1984. – 184 с.

2. Казанский В.Е. Измерительные преобразователи тока в релейной защите. - М.: Энергоатомиздат, 1988. - 240 с.

3. Васин А. А., Муха В.П., Чурсинов В.И., Шевченко О.А. Повышение пожарной безопасности электрических сетей 0,38-0,22 кВ // Наук. праці ДонНТУ. Серія: “електротехніка і енергетика”, випуск 41.- Донецьк: ДонНТУ, -2002. с.114-117.

4. Чорноус Є.В., Шевченко О.А. Дослідження динамічних властивостей давача струму реле іскрозахисту // Зб. наук. праць ДонНТУ. Серія: “електротехніка і енергетика”, випуск 28.- Донецьк: ДонНТУ, -2001. с.152-160.

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