RU168089U1 - UNDERGROUND HIGH-VOLTAGE ELECTRICITY SYSTEM WITH ISOLATED NEUTRAL - Google Patents

Abstract

The utility model relates to electrical engineering, in particular to an underground high-voltage power supply system with insulated neutral, designed to power various types of mining equipment with electric drives for voltage of 3000, 6000 and 10000 V. It is based on the task of creating an underground high-voltage power supply system, in where the circuit change of the system, taking into account the galvanic separation between the power circuit and the grounding network, eliminates the transition from the power circuit of leakage currents to the ground and, thereby improve the electrical characteristics of the high voltage network. The problem is solved due to the fact that the underground high-voltage power supply system with insulated neutral contains a three-phase power supply, a three-phase distribution cable network equipped with a screen conductor, made in the form of a three-phase cable containing three power cores with an individually applied semiconducting screen and an armored sheath, power receivers and a device insulation resistance control, which is connected to the distribution cable network between the power conductors and the screen, the latter in It is made non-insulated and with the possibility of contact with the screens of power conductors, while it is isolated from the armor shell and the cases of power receivers. 1 n.p. f-ly m., 1 ill.

Description

The proposed technical solution relates to electrical engineering, in particular to an underground high-voltage power supply system with insulated neutral, designed to power various types of mining equipment with electric drives for voltage of 3000, 6000 and 10000 V.

A well-known underground high-voltage power supply system, consisting of a three-phase energy source, high-voltage switchgear, switchgear, distribution network and power receivers for various purposes (see book. "Electric drive and power supply for mining machines", PL Svetlichny, p. 146- 253).

The energy source for powering electrical receivers in a mine, as a rule, is three-phase power transformers installed in the main surface substation (GPP). The distribution cable network is based on power cables containing three power cores, one ground conductor and an armored sheath, which, like the ground conductor, are connected to the electrical housings on both sides of the cable.

The operation of the underground power supply system is as follows. From the GPP, a voltage of 6000 V is supplied via a cable network to the central underground substation (CPP) and then to the distribution underground high voltage points (RPP-6). From RPP-6, voltage is supplied to high-voltage power consumers: drainage and fan installations, mobile transformer substations. The latter converts high voltage to low voltage (660 and / or 1140 V) and low voltage power is supplied to electrical receivers through switching devices.

The inclusion of the underground high-voltage power supply system is carried out by supplying the primary mains voltage to the switchgear and turning it on. After that, the aforementioned high voltage power receivers will be included. By controlling the switching on and off of the switchgear, the inclusion and shutdown of high-voltage power receivers is achieved accordingly. Commands for turning on and off are performed using special handles or remote controls built into the switchgear.

In normal operation, the distribution network is isolated from the ground conductor (earth) and from the enclosures of the electrical receivers. However, in emergency conditions caused by a short circuit (short circuit), a decrease in the insulation resistance of the main conductors laid in the cable, active, capacitive and inductive conductances, current leakage from the power circuit to the ground circuit occurs. The latter is due to the fact that in the structure of power cables, the main conductors and an uninsulated ground conductor are laid in a common twist and are in contact with each other.

In emergency conditions, an electric circuit “three-phase network - ground conductor” occurs, as a result of which leakage currents from the network through the ground conductor flow into the common shaft ground network. The transfer of leakage currents to the ground is the main disadvantage of the underground power supply system operating in the industry, since:

- unprotected sparking occurs in the ground circuit, which can ignite the methane-air mixture;

- leakage currents are sufficient for electric shock;

- the capacity “power core - grounding core” represents the accumulated energy, dangerous both from the point of view of sparking and from the point of view of electric shock to people;

- the distribution high-voltage power supply network is long and continuous, starting from the main surface substation to step-down transformers, which contributes to the creation of capacitive conductivity and can cause negative consequences;

- the continuity of the mine network and its branching does not allow for the selective determination of the damaged section of the network;

- in the applied structure of the power supply system, it is impossible to implement solutions to reduce the capacity of “power core - ground wire”, which negatively affects the network parameters even in the normal mode of its operation;

- leakage currents of increased power flow through the ground circuit, which is unacceptable under the condition of ensuring its intrinsic safety (GOST 22782.5 requirement "Explosion-proof electrical equipment with type of protection" intrinsically safe electrical circuit. Technical requirements and test methods ");

- with a single-phase earth fault, spark leakage currents occur, which under certain conditions are a source of explosion and fire;

- control circuits of leakage currents to the ground, through which special protective devices determine the state of insulation of the network, are spark hazardous and therefore dangerous with respect to ignition of methane.

It should also be noted that leakage currents of increased power of various origins flow through the grounding circuit (leakage currents from the power circuit, stray currents of the contact network of electric locomotive haulage, galvanic-EMF sources, induced EMF in the grounding circuit when current flows in the power circuit, sources of terrestrial origin and etc.) that are capable of violating intrinsically safe circuits. Therefore, according to GOST 22782.5 "Explosion-proof electrical equipment with type of protection" intrinsically safe electrical circuit ". Technical requirements and test methods "grounding of intrinsically safe circuits is prohibited.

These shortcomings show how unacceptable from a safety point of view the passage of leakage currents to the ground. To eliminate the negative effects of leakage currents, it is necessary to develop a new underground power supply system in which the conditions for the transfer of leakage currents to the ground should be eliminated.

The utility model is based on the task of creating an underground high-voltage power supply system, in which a circuit change of the system, taking into account the galvanic separation of the power circuit and the ground network, allows eliminating the transition of leakage currents to the ground from the power circuit and, thereby, improving the electrical characteristics of the high-voltage network .

The problem is solved due to the fact that the underground high-voltage power supply system with insulated neutral, containing a three-phase power supply, a three-phase distribution cable network, power receivers and an insulation resistance control device, which is connected under the distribution cable network, the latter is made in the form of a three-phase cable, consisting of of three power conductors with individually applied semiconducting screen and armored sheath, according to a utility model, distribution the cable network is equipped with a screen conductor, made non-insulated and with the possibility of contact with the screens of the power cores, while it is isolated from the ground conductor, which is used as an armored sheath, and the cases of power receivers, and the insulation resistance control device is connected to the distribution network between the power cores and the screen residential.

The claimed technical solution for the first time provides for a new circuit design of an underground high-voltage power supply system, in which: a screen core is introduced into a distribution cable network and located in a cable so that it reliably contacts the power conductors (network phases); the screen conductor is made non-insulated and galvanically separated from the armor shell and the cases of power receivers; the insulation resistance control device is connected between the phases of the network and the screen conductor.

The proposed underground high-voltage power supply system made it possible: firstly, to galvanically separate the mine network into electrically isolated sections, which made it possible to selectively determine the occurring failures in each section of the network without the use of an expensive isolation transformer; secondly, to exclude the passage of the leakage current into the ground and, thereby, eliminate the conditions for ignition of the methane-air mixture and the defeat of people; thirdly, to reduce the capacity of the distribution network by dividing it into predetermined sections determined by the length of the screen core, and thus reduce the likelihood of explosions and fires in mines and eliminate conditions for electric shock to people; fourthly, it is more accurate to measure the occurring leakage currents due to the elimination of their spreading along the moist host rocks of the mine and conductive devices.

In addition, for the first time, the connection diagram of the device for controlling the insulation resistance to the power circuit has been changed: it is connected between the three-phase power circuit and the screen core. Such a connection made it possible to more accurately measure the occurring leakage currents in the mine network by eliminating their spreading over the host rocks of the mine.

The above provisions allowed to eliminate the disadvantages inherent in the prototype.

The claimed technical solution is illustrated by the diagram shown in the figure, which shows one of the sections of the high-voltage network of the mine.

The underground power supply system contains: a complete switchgear (hereinafter - switchgear) 1 with a switch 2, a node 3 for connection and a device 4 for controlling the insulation resistance, a distribution network consisting of a three-phase power circuit 5, a screen conductor 6 with clamps 7 and 8 and an armored a shell 9 with connection clamps 10 and 11, an electric receiver 12, which is used as a mobile transformer substation with a step-down transformer 13, a high-voltage disconnector 14 and a low-voltage switch 15.

The circuit of the node 3 intended for connecting the device 4 to the three-phase network 5 can be made on the basis of a resistor, diode or throttle filter. Device 4 is commercially available.

A feature of the claimed underground power supply system is that the electrical circuit for the leakage current in emergency conditions (short circuit in the network, a decrease in active, inductive or capacitive resistance in the distribution network) is formed using the screen core 7, and not the ground wire, as it is in a known solution, and the phases of the distribution network. In this case, the clamps 7 and 8 of the screen core 6 are not connected to the switchgear casings 1 and the power receiver 12. In addition, this wire is not electrically connected to the armor shell 9. The latter, in turn, is connected to the switchgear casings 1 and the power receiver 12.

The device 4 for monitoring the insulation resistance and the node 3 for connecting the device 4 to the network can be manufactured as a separate product. A variant is possible when the connection unit 3 is located in the switchgear 1, and the device 4 is made as a separate product. Other options are also possible.

The operation of the underground power supply system is as follows. After switching on the switchgear 1, a voltage of 6000 V is supplied via a distribution network 5 to high-voltage power receivers 12, in particular, to a transformer substation 13. The inclusion of a disconnector on the high-voltage side of the substation 13 and a switch 15 on the low side of the transformer, forms a reduced voltage on the basis of electromagnetic induction ( 660 or 1140 V). This voltage is supplied through the switching devices (not shown in the figure) to low-voltage power consumers.

In the normal state of the power supply system, when there are no emergency modes, the system is operating normally. When one of the types of emergency conditions occurs, in particular, when the insulation resistance Z ₁ decreases, in one of the phases of the three-phase network there is a current leakage along the “damaged phase - screen core” circuit and, then, through the current leakage control device 4, the connection unit 3 and into the intact phase of the network. Depending on the value of the leakage current, the device 4 reacts differently. If the normalized value is exceeded (120 kOhm per phase), the device processes a signal for protective voltage shutdown with the help of switchgear 1. The voltage is disconnected from the damaged section of the network.

It is appropriate to note here that in the known power supply system, leakage currents pass to the ground and then go to device 4. At the same time, part of the leakage currents flows along the natural grounding circuit (metal pipelines, rail track, flooded sections of excavation soil, etc.), which It does not allow accurate measurement of emerging leakage currents.

In the claimed solution, the leakage current does not branch into the ground due to the fact that the screen core, as already noted, is isolated from the cases of electrical devices and is not connected to the armor shell. Therefore, the total amount of current flows only through the control device 4 and, thereby, allows you to accurately measure the value of the leakage current.

Using the proposed solution, it became possible to automatically discharge the capacitance “main core - screen core”, which eliminates the need for a forced discharge in an unprotected working zone by contacting each phase with the metal case of any product, as is done in the power supply system - prototype. The armor shell 9, connected to the cases of switching devices and electrical receivers, provides a continuous grounding circuit for all network objects, which ensures protection against electric shock in case of workers touching the buildings of electrical installations.

Isolation of the screen conductor 6 from the cases of the power receiver 12 and the switchgear KRU 1 creates a closed circuit for the leakage current only in the area "KRU 1 - power receiver 12" and, thereby, provides selective voltage disconnection from the damaged area. In the prototype, such a function can only be performed using a special isolation three-phase transformer, which is expensive in cost and several times higher than the cost of the protection device 4.

The claimed technical solution provides for a new structure of the underground power supply system, providing:

- Introduction to the distribution cable network of the screen conductor isolated from the armor shell and the cases of power receivers;

- connection of an insulation resistance control device between the phases of a three-phase circuit and a screen conductor;

- separation of the high-voltage network into separate sections using a screen core;

- galvanic phase separation of a three-phase circuit and ground conductor.

The proposed solution provides:

- elimination of the conditions for the leakage current in emergency conditions to pass to the ground, which can significantly improve the safe properties of the power supply system, since leakage currents flow back to the power network, and not to the ground circuit, as is implemented in the well-known power supply system;

- selectivity of disconnecting the damaged area due to the separation of the high-voltage network into isolated sections of the screen housing;

- a decrease in the capacity of the high-voltage network due to its division into separate sections and, thereby, a decrease in the value of the dangerous capacitive current entering the ground;

- improving the accuracy of the power circuit current monitoring device by eliminating the occurrence of a controlled leakage current of the natural grounding circuit, which uses enclosing rocks and conductive devices (pipelines, rail track, etc.);

- a sharp decrease in the cost of using an insulation resistance control device and a reduction in labor costs during its installation due to the exclusion of an isolation transformer;

- an increase in the operational reliability of the high-voltage power supply system due to the absence of an isolation transformer in the high-voltage network system;

Thus, for the first time, an underground power supply system with an isolated neutral was developed, which contains a set of new solutions aimed at real ensuring the safety of the use of electric energy in mines.

The considered system of underground high-voltage power supply can similarly be implemented in mine low-voltage networks with a voltage of 660, 1140 V.

This solution is fundamentally new and has no analogues in world practice.

Claims (1)

A three-phase cable with an insulation resistance control device in a three-phase cable line for an underground high-voltage power supply system with an insulated neutral, consisting of three power conductors with an individually superimposed semiconductor screen and an armored sheath, the cable comprising a screen core made uninsulated, with the possibility of contact with the power screens veins, this core is isolated from the grounding core, which is used as an armored sheath, and the insulation monitoring device is connected to do power conductors and a screen of living.

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