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Abstract

The content of the abstract

Introduction

Mine Low Voltage complex characterized by the presence of general low-voltage transformer substation, circuit breakers and starters on aggregate number of electrical consumers. As electrical load typically used with phase induction motors and squirrel cage. Combined low-voltage electrical network section of the mine represented by the collection and an extensive system of flexible armored cable runs.

1. Relevance of the topic

Used in mines electrical cables and power supply system must provide electrical mine workers, as well as an explosion–and fire.

In mine local network holds the largest number of injuries compared to other areas of the mine supply.

Limited space in mines in low light conditions significantly complicates installation, preventive maintenance and repair of electrical equipment. Because of delays in troubleshooting the problems in electrical equipment, as well as a result of erroneous actions of service personnel in mine electrical equipment in frequent short-circuit current (Isc).

Mine electrical equipment affected by moist air and coal dust. In operating conditions, Coal dust and moisture are deposited on the surface of the insulating parts of electrical equipment, whereby there are leakage currents, which under certain conditions, evolve into short-circuit currents. For periodic heating and cooling mine electrical dew may form, which will also create the conditions for the occurrence of short-circuit. As a result of observations revealed that the failures of circuit breakers AB because of insulation between the phases is 17.6% of the total number of failures.

Existing tools overcurrent protection are based on monitoring the current in the accession and comparing this current with a predetermined setpoint and subsequently disconnected emergency site when the current exceeds this threshold. However, this principle implies a certain time delay detection of short-circuit the process, due to the need to achieve the current setpoint. In addition, there is the probability of error in the calculation of personnel and configuring settings positives from overcurrent. So is the development of topical remedies against short-circuits improved performance, built on the principle of autonomous alarm detection process without the intervention staff.

2. Analysis process underground development as automation object

Technological process of tunnel works in the complex-mechanized heading bottom groove with a combine includes the following operations:

  1. Destruction massif tunneling machines and chipped load coal onto a conveyor belt;
  2. Advancing mechanized system composition and conveyor mounting goaf;
  3. Airing the tunnel face.

The process is characterized by the destruction of the coal array variability of physical and mechanical properties of coal, as well as changes hypsometry and seam thickness.

Figure 1 –Processwater scheme of the process of penetration combine

Figure 1 shows a diagram of the process of penetration of coal shearer:

  1. Roadheader;
  2. Excavator;
  3. Composition trolleys;
  4. Chain conveyer;
  5. Belt conveyor.

The process of destruction of the coal array includes:

  1. Automatic load control processor. Load regulation of electric motors allows for more efficient use of energy possible occasion, improve performance combine to increase its life by reducing the dynamic overloads, free driver continuous control feed rate.
  2. Motion control harvester profile formation is necessary for maximum mineral extraction and normal working conditions of complex equipment in accordance with the technological requirements [1].

3. Justification direction process automation underground development

The vast majority of the prior art, which can be attributed to the overcurrent protection in mine local elektrotehnochnom complex, fulfill the function of detecting short-circuit current on the supply side (KTP) and high-speed off this source of energy flow from the electrical connection in which there was an interfacial short-circuiting. Respective executive devices and displays fault current Device can be divided into direct and indirect device. Recent actions should be given to the work of the teams from the respective devices automatically detect short-circuit current. The basic principle of detecting short-circuit current, which is fulfilled by means of overcurrent protection mine local networks is to compare the actual current network with a predetermined setpoint and the formation of a team to disable the switching device in case of exceeding this current setting value. A distinctive feature of the devices for indirect actions (YMC, PMZ, etc..) Is that a parameter measuring transformer secondary currents formed tori current protection function is fulfilled comparative circuitry, which can adjust the pickup setting.

Existing tools overcurrent protection are based on monitoring the current in the accession and comparing this current with a predetermined setpoint and subsequently disconnected emergency site when the current exceeds this threshold. However, this principle implies a certain time delay detection of short-circuit the process, due to the need to achieve the current setpoint. In addition, there is the probability of error in the calculation of personnel and configuring settings positives from overcurrent [2].

The main parameters characterizing the performance of electrical complex mine area include:

  1. The secondary winding of the transformer substation mine GSTP-630 (Rtr = 0.018 ohms = 0.078 ohms xmp file);
  2. Cable line length of 250 m (cable brand KGESH 3*70A, Rk = 0,281 Ohm / km, Lk = 0,252*10-3Gn/km, Ck = 0,87*10-6 F/km;
  3. Induction motor (1EKV3, 5-200, Un = 660V, pH = 280kW);
  4. Circuit breaker (tcp = 6ms).

The developed model reproduced the behavior of the object graph.

Fig. 2 shows the corresponding SimPowerSystem–model consists of the following parts:

  1. The secondary winding of the transformer substation mine – GSTP-630–Three-PhaseSeriesRLCBranch;
  2. Cable line of 250 m length – PiSectionLine 1-6;
  3. Asynchronous dvigun – 1EKV3 5-200-AsynchronousMachineSIUnits;
  4. Circuit Breaker – Three-PhaseBreaker;
  5. Block shorting – Three-PhaseFault.

Figure 2 – SimPowerSystem-precinct network model adopted for the study of transients in the event of a short circuit

Were modeled 3-phase short circuit obtained and the corresponding relations of current change at the injury site, periodic and aperiodic components of the fault current.

Figure 3 – Depending on the current change in a 3-phase short circuit

As a result of the research computer model of a mine precinct character set changes electrical short-circuit current transition process is accompanied by the appearance of aperiodic component short-circuit current, characterized by the presence of active-inductances from the supply transformer substation to fault location.

Present model allows us to analyze processes when changing the object of study. Developed protective device is based on monitoring the presence of this DC component, which occurs at the initial moment of the existence of short-circuit [3].

4. Development of device protection system process automation penetration excavation

Figure 4 – Block diagram of short-circuit protection device with the high-speed response

ДТ1-ДТ3 – Current Sensors;

БП – power supply unit;

И – Display;

И – Display;

МК – microcontroller.

On the basis of the structural scheme (Fig. 4) developed a functional diagram of the device, which is shown in Figure 5.

Figure 5 – Functional diagram of the short-circuit protection device with the high-speed response (animation: 5 frames, interval 1000 m/s, 46 kilobytes)

The circuit operates as follows: The voltage supplied to the network. Signals from the current sensors DT through a voltage divider input at RP – digital converter. The resulting signal is fed to the input unit-output information microcontroller (MC). MK is processing and the necessary measurements. The results of measurements compares providing current amplitudes oscillation parameters with the default values ​​of the amplitudes during normal power supply. If all parameters are normal, then nothing happens. If the amplitudes of the oscillations is abnormal, an alarm is given an emergency to the control unit CU, which disables the starter drive the combine. Also out signals from the microcontroller to manage the work world indication I.

In the presence of voltage signals from the current sensors TA1-TA3 through voltage divider RP fed to an analog-to-digital converter. The resulting signal is passed to the block input–output information microcontroller (DD1), which processes the data in accordance with the algorithm works (Fig. 5) and, in the case of a short circuit, sends an emergency signal to the control unit VT, which disables the switching device emergency connection, as well as block light indication HL.

The principle of operation is based on the control interval duration mismatch of output pulses of current sensors U1–U3 and additional pulse sequences U4–U6, formed microprocessor control system. In normal mode, the power and duration of the duty cycle of each of these pulses is π radians, and the phase shift between the pulses of the two adjacent phases – π/3 rad. When a mismatch of the input pulses and additional counts of the respective phases (U1 and U4; U2 and U5; U3 and U6) signals are formed U7–U9. The duration of each of these signals is the difference between the duration of pulses in the normal mode and the actually existing power pulses from current sensors.

At time fault is a short circuit in the power supply cable. Length and duty cycle U1, U2, U3 changes due to the presence of an aperiodic component Isc and accordingly, the asymmetry of the total current. This leads to a signal U7–U9 and the appearance of the output pulse (signal U10), supplied to the actuator, the switching control circuit power switching device that performs high-speed safety shutdown voltage [4].

Figure 6 – Operation algorithm of the automatic short-circuit protection with the high-speed response

Findings

Thus, the proposed computer model and reasonable assumptions it possible to establish the nature of variation of the parameters short-circuit current, which consists of periodic and aperiodic components. Asymmetry full Isc relative to the axis of time (due to the presence of DC component) clearly shows the initial stage of the regime of short circuit in the ETC section of the mine. Justified algorithm and the automatic protection circuit against short circuit currents with the high-speed response, which is based on the specified control.

When writing this abstract masterʼs work is not finished. Final completion: December 2014. The full text of the work and materials on the topic can be obtained from the author or his head after the specified date.

List of references

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