Author's abstract

One of the basic means of maintenance of an electrosecurity in collieries is protective switching-off with the device of indemnification of currents of capacities which allows to remove a pressure from the person who has appeared energized, and also to reduce a current to normalized GOST to 22929-78 value. 

The urgency of the given research consists that application of the mentioned devices can appear insufficient as a result of occurrence of return CEF rotations of engines which value can appear dangerous from the point of view of defeat of the person by an electric current.

The reason consists in features of the basic electroconsumers of a site is, as a rule, asynchronous engines of an occasion of different machines. [4]After switching-off of a pressure of a nutritious network rotors the AE continue to rotate, that is caused by a stock of kinetic energy, generating in network CEF rotation. This CEF, first, supports in the included conditionactuators, and secondly, feeds an emergency point which negatively influences parameters of an electrosecurity. Thus, the purpose of my research - to develop system by means of which it is possible to lower probability of an electrotraumatism and failures.

Technological process as object of automation.

The purpose of designing and the requirement to the developed device of automation.

To electrification of mines are applied three-phase СEС an alternating current from isolated by a neutral of the transformer. [5]Safety of operation such СEС, unlike networks with the earthed neutral is defined not only probability of a touch of the person to elements of an electric equipment which is under a dangerous pressure, but also by a condition of their isolation, concerning the ground. As currents of outflow understand currents which pass between elements of an electric equipment, электрически connected with phases of a network and the ground. In particular, it is a current through a body of the person which has touched, to an element of an electric equipment which is energized. With increase Rиз of phases of a network concerning the ground currents of a source and, hence, danger of defeat by an electric current, the probability of occurrence of fires and the explosions of a miner atmosphere caused by currents of a source, decrease. This circumstance allows to provide safety of operation mine СЕС by means of equipments of protection against currents of a source which incessantly supervises them Rиз concerning the ground and making protective switching-off of networks in case of occurrence of dangerous currents of a source. Electroreceivers on sites of mines get from RP, that consist of the complete set of starting and protective equipments, on cables of the limited length (it is usual no more than 300...400).[3] Therefore conductivity of isolation of phases of a network concerning the ground (active and capacitor) can be presented as the sum to isolation of separate branches concerning the ground (active and capacitor) can be presented as the sum to isolation of separate branches concerning small length. Considering, however, that the quantity of the electric equipment attached to one KTP, can reach 100, and the general length of a cable network - several kilometers, the total capacity of mine local electric networks НН concerning the ground can be enough significant and, as a rule, fluctuate within the limits of 0,3...3 mkf, that is 0,1...1 mkf on a phase. Therefore, if to not arrange on decrease in capacitor compound currents of a source, these currents will be caused by capacity of a network, instead of active Rиз. The equivalent scheme of a mine local network together with a contour is resulted on fig. 1. It contains equivalent three-phase source Е which models local substation in view of internal resistance of the transformer, longitudinal Zl0 and cross-section Zu0 resistance of a cable which substation with local distributive item (URP). Also are similarly modelled longitudinal (Zl1, Zl2) and cross-section (Zu1, Zu2) support of the cables connecting most powerful.

Animated figure 1 — the Equivalent scheme of a mine local network. (GIF-animation, 20 frames, 1fps. MP Gif Animation)

Animated figure 1 — the Equivalent scheme of a mine local network.
(GIF-animation, 20 frames, 1fps. MP Gif Animation)

On the scheme fig. 1 indexes of currents answer number of a branch of an investigated circuit, number of resistance - to currents of all branches on phases And, In, S. Electric current earth a contour which cannot be carried to any concrete phase, presented with vector Iz with indexation according to the scheme fig. 1. As the basic variant of an emergency is accepted short circuit on the case of the first mechanism of a phase And, and on the case of the second mechanism - phases From the power supply.[2] On fig. 1. It is simulated by currents I5 and I6 which answer currents Ia1 and IС2.[1] The probability of defeat of the person an electric current is defined by value of a current and duration of its course. The current which has been last through the person, depends from active Rиз and capacities of a network concerning the ground. Necessary value active Rиз networks is provided with preventive actions and supervised by devices of protection against sources. The capacity of a network is lowered cannot be, because is defined by the general length of a cable network. Decrease in its influence on currents of a source is reached by indemnification of capacitor currents. Time of course of a dangerous current of a source is equaled to the sum of times of operation protective, switching-off, her of a network and voltage reductions in a network, supported by return CEF turnaround by inertia the AE. Last composed depends on capacity, loading and parameters the AE, and can reach 3...5 with, and the sum of the first and the second composed should not exceed 0,2 with in networks with a linear voltage up to 660 V and 0,12 of with a voltage 1140 V.

Let's consider the reasons of occurrence and kinds of outflow.

For exception of an opportunity of explosion of a miner atmosphere by an electric arch or a spark that arise at normal work or damage of an electric equipment, its elements place in special hardened environments which protect also the attendants from a casual touch to current carrying parts. Therefore at not damaged electric equipment and performance of instructions from its safe service of people can concern only elements which are not energized (indirect contact). These elements appear energized only as a result of damage isolation details. However, at infringement of instructions or damage of an electric equipment can occur and direct contact of the person to current carrying parts of an electric equipment. Thus, principal causes of occurrence sources are decrease active Rиз elements an electric equipment, mechanical damage or electric breakdown details, and direct contact of the person to current carrying elements. Depending on number of phases with lowered Rиз concerning the ground of a source are divided into three kinds: single-phase, biphase and three-phase, when the damaged isolation according to one, two or three phases of a network.[6] Concerning danger of defeat by an electric current distinguish resistance of isolation and resistance of a three-phase source. Under the first understand resistance of phases of a network concerning the ground, made of in parallel included resistance of set serviceable details, and as the second - support damaged details which define the currents of a source concentrated in them. Currents of outflow on their value divide into two kinds:

  1. long weak currents which do not cause operation of protective equipments and consequently proceed during unlimited time;
  2. short-term greater currents which lead to operation of devices of protection against currents of a source and switching-off of networks which protect them;

Time of course of this current is defined from time to time switching-off of a network by the device of protection and from time to time decrease in return ЕРС the engines attached to this network.[7] Time of switching-off of an electric network is time from the moment of occurrence of a dangerous current of a source to full break of a circuit of a feed of a network from the power transformer. It consists of time of operation of the device of protection against currents of a source, that is submission of a command for switching-off of a network, and time of operation of the switching device (the automatic switch) in view of time of clearing of an arch for its contacts.

Algorithm of work of the block of memory and indication 

Figure 1 — Algorithm of work of the block of memory and indication.

Figure 1 — Algorithm of work of the block of memory and indication.

Литература

  1. Риман Я.С. Защита подземных электрических установок угольных шахт. М.: Недра, 1977. — 206с.
  2. Справочник энергетика угольной шахты: В 2 т. / В.С.Дзюбан, И.Г.Ширнин, Б.Н.Ванеев, В.М.Гостищев; Под общ. ред. канд. техн. наук Б.Н. Ванеева. — Изд. 2-е доп. и перераб. — Донецк: ООО "Юго-Восток, Лтд", 2001. 447 с.
  3. Щуцкий В.И., Волощенко Н.И., Плащанский Л.А. Электрификация подземных горных работ: Учебник для вузов — М.: Недра, 1986. — 364 с.
  4. Груба В.И., Калинин В.В., Макаров М.И. Монтаж и эксплуатация электроустановок: Учеб. для вузов. — М.: Недра, 1991. — 239 с.: ил.
  5. Правила безопасности в угольных и сланцевых шахтах. ДНАП1.1.30-01-96: Утв. Гос. Комитетом по наблюдению за охраной труда 18.01.96/ Гос. Комитет по наблюдению за охраной труда. – К, 1996, – 421с.
  6. Дзюбан В.С., Риман Я.С. Об электромагнитной постоянной времени затухания обратной э.д.с. шахтных электродвигате-лей. - В кн. Взрывобезопасное электрооборудование. Вып. 6 М., Энергия, 1969.
  7. Панфилов Д.И. и др. Электротехника и электроника в экспериментах и упражнениях: Практикум на Electronics Workbench. Т1. Электротехника.- М.: ДОДЭКА, 1999.- 304 с.
  8. http://www.gaw.ru/ - рынок микроэлектроники
  9. http://www.elecab.ru/ - справочник электрика и енергетика
  10. http://ukrniive.com.ua/ - офіціальний сайт Український науково-дослідний, проектно-конструкторський і технологічний інститут вибухозахищеного та рудничного електрообладнання з дослідно-експериментальним виробництвом (УкрНДІВЕ)