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Abstract

Contents

Introduction

Exploitation of coal mining Electrical equipment characterized by rather extreme conditions and main influencing factors which are: limited size openings, high humidity, a significant content of coal dust in the atmosphere; unsteadiness of technological equipment.

Seeing this, the operation may frequent mechanical damage to the flexible power cord that leads to such emergency conditions such as short circuit – one of the most dangerous disrepair in mine.

Thus we can conclude this issue requires further study.

1. Theme urgency

Short-circuit current due to a voltage source is limited to active and inductive resistance sources and areas of electricity to the point of short circuit. Given that these towers have very small values, the value of short-circuit current can reach several thousand amperes. Selected with the heat can not only damage electrical equipment, but also take a fire or explosion methane.

Means overcurrent protection, which is equipped with all the switching equipment of mine, take defence off at any time, in accordance with the regulations. However, an emergency condition while still maintained reverse EMF induction motor rotation previously enabled consumers to switch to freewheel.

Thus we can conclude that this issue requires further study and creation of technical means to protect the electrical network complex mine site from exposure to reverse energy flow induction motor in the event of an emergency situation.

2. Goal and tasks of the research

Purpose – expand the functions of the automation subsystem of safe mining activities implemented by increasing the effectiveness overcurrent protection and protection against current leakage to earth in electrical engineering complex mine site by reverse power flow separation asynchronous consumer mine site.

The main objectives of the study:

– Development of mathematical and computer models of electrical complex section of the mine in the state of damage to the electric cord and set asynchronous nature of the influence of consumers in freewheel mode on the place of injury;

– Study and development of structural, functional and schematic diagram means protection against reverse power flow in place of AD damage the cable's power.

3. Results of studies

In MATLAB system were modeled 3 types of short-circuit and received appropriate depending on the current change in the place of injury:

1. Three-phase short circuit – short circuit current in phase A measured by ammeter A1 (Figure 1);

2. Two-phase short circuit between phases A and B – short-circuit currents measured: in phase A – ammeter A1 in phase B – ammeter A3 and phase C – A5 ammeter (Figure 2);

3. Single-phase short circuit (phase A) on the ground – short-circuit current measured in the circle circuit – A7 ammeter (Figure 3) [11].

Short-circuit current in phase A at three-phase short circuit (ammeter A1)

Figure 1 – Short-circuit current in phase A at three-phase short circuit (ammeter A1)

Short-circuit current in phases A, B, C in the two-phase short circuit between phases A and B (ammeters A1, A3, A5)

Figure 2 – Short-circuit current in phases A, B, C in the two-phase short circuit between phases A and B (ammeters A1, A3, A5)

Short-circuit current in critical terms in single-phase short-circuit phase A to ground (ammeter A7)

Figure 3 – Short-circuit current in critical terms in single-phase short-circuit phase A to ground (ammeter A7)

As a result of the research a computer models of mine polling station network was established component of the change in short-circuit current. Due to the influence of rotation of induction motor, which was included in the emergency joining. The transition process is accompanied by an intense increase in the current site of injury, followed by a decrease in amplitude and frequency.

So is the actual development of the system of bilateral blackout fault cord blood pressure.

These requirements are met by the technical solution (PZK), the effect of which is based on the separation of the three-phase stator circuit current in the presence of an artificial definition of the operational parameter circuit between the motor stator and a grounded metal enclosure [12].

PZK functions can be implemented the scheme shown in Figure 4 [13]:

Schematic circuit diagram of the device PZK

Figure 4 – Schematic circuit diagram of the device PZK

When voltage is applied to the induction motor stator circuit, the lamp HL1 is on, which indicates the device is switched PZK

The main part of the PZK-scheme formed by the series connection of the link capacitors C3-C4 and diode VD1. It provides: maintenance of the isolated neutral networks in the absence of a single-phase earth leakage, eliminate a DC current, including the operating PZK current. At the time of single-phase ground fault generated voltage pulse duration limited by the resistor R1, is sufficient to actuate the severing means responsive organ reverse energy flow induction motor, where by the voltage in the capacitor C3 is converted into a proportional voltage across the resistor R2 and compared with a minimum setpoint level, which is removed from the resistor R4. If there is current in the capacitor C3, DA1 comparator generates a logical "one", which is stored trigger link D1.1-D1.2 and through optocoupler VD4 includes a force-pole relay KM1. Capacitor C2 is involved for the off delay of the relay in a small period of time sufficient to absorb reverse energy flow induction motor.

While the VD5 is led, indicating the device is triggered

Conclusion

Results of work:

– The urgency analysis of the complex processes in the electrical safety of the mine after the power was cut off because of the need to improve the means of automatic protection;

– Based framework, the parameters of mathematical and computer models of complex electrical shaft with the influence of reverse energy flow induction motors consumers;

– Set parameters behavior of the short-circuit current with the energy flows of the system to coast engines consumers;

– Based system of bilateral blackout space of a short circuit in the power cord blood pressure, which allows you to extend the functionality of existing protective equipment;

– A variant of technical implementation and proved system of bilateral blackout space of a short-circuit in the supply cable induction motor, which improves the efficiency of automated subsystems of safe operations at the mining sites.

Reference

  1. Пучков Л.А. Электрификация горного производства: учебник в 2-х томах [для студентов высших учебных заведений] / Л.А. Пучков, Г.Г. Пивняк – М.: Горная книга, Т.1. – 2007. – 511 с., Т.2. – 2007. – 595 с.
  2. Щуцкий В.И. Электрификация подземных горных работ: учебник [для студентов высших учебных заведений] / В.И. Щуцкий, Н.И. Волощенко, Л.А. Плащанский – М.: Недра, 1986. – 364с.
  3. Дехтярева В.И. Руководство по ревизии, наладке и испытанию подземных электроустановок шахт / В.И. Дехтярев, В.А.Чумаков, М.С. Глухов, Э.Р. Осипов – М.: Недра, 1989. – 614с.
  4. Ванеев Б.Н. Справочник энергетика угольной шахты / Б.Н. Ванеев, В.С. Дзюбан, И.Г. Ширнин, Б.Н. Ванеев, В.М. Гостищев – 2-е изд. – Донецк, ООО «Юго-Восток Ltd.», 2001. – 447с.
  5. Правила безпеки у вугільних шахтах – К.: ДНАОП, 1996. – 150с.
  6. Правила технічної експлуатації електроустановок споживачів. Затв. 25.07.2006 № 258/ Міністерство палива та енергетики України. Х. Індустрія. 2007. – 272 с.
  7. Цапенко Е.Ф. Электробезопасность на горных предприятиях: учебн. пособ. [для студентов высших учебных заведений] / Е.Ф. Цапенко, С.З. Шкундин – 2-е изд. – М.: Горная книга, 2008. – 103 с.
  8. Вареник Є.О. Забезпечення безпеки та ефективності шахтних електроустановок / Є.О. Вареник, С.І. Випанасенко, В.С. Дзюбан, Н.А. Шидловська, Ф.П. Шкрабець – Дніпропетровськ: НГУ, 2004. – 334 с.
  9. Озерной М.И. Шахтные гибкие кабели / М.И. Озерной, В.Г. Соболев – М.: Недра, 1966. – 300 с.
  10. Півняк Г.Г. Перехідні процеси в системах електропостачання: Підручник для вузів / Г.Г. Півняк, В.М. Винославський, А.Я. Рибалко, Л.І. Несен – вид. 2-ге, виправ. та доп. – Дніпропетровськ: Національний гірничий університет, 2002. – 579 с.
  11. Дулін І.А. Моделювання к.з. в мережі асинхронного двигуна / І.А. Дулін, І.В. Ковальова // Автоматизація технологічних об’єктів та процесів. Пошук молодих: ХIІ міжнар. наук.-техн. конф., 17-20 квітня 2012р.: зб. наук. праць. – Донецьк: ДонНТУ, 2012. – С. 328-330.
  12. Маренич К.М. Дослідження процесів у дільничній електромережі шахти при застосуванні засобу синхронного двобічного знеструмлення місця пошкодження кабелю / К.М. Маренич, І.В. Ковальова // Гірнича електромеханіка та автоматика: наук.-техніч. зб. Випуск 85. – Дніпропетровськ, 2010. – С. 3-11.
  13. Ковальова І.В. Технічн1а реалізація способу синхронного двобічного знеструмлення місця пошкодження кабеля електроживлення асинхронного двигуна в мережі шахтної дільниці / І.В. Ковальова // Автоматизація технологічних об’єктів та процесів. Пошук молодих: ХI міжнар. наук.-техн. конф., 17-20 травня 2011р.: зб. наук. пр. – Донецьк: ДонНТУ, 2011. – С. 62-64.