RU2342711C2 - Fire prevention method in electrical network or electrical installation and device to this end - Google Patents

Abstract

FIELD: alarm systems.

SUBSTANCE: present invention pertains to fire prevention and electrical energy, and particularly to methods and devices for preventing fire, arising at different facilities due to faults in wiring and other elements of electrical networks or electrical installations, leading to arcing, short circuiting or network overloading, leakage currents or dangerous change in mains voltage. The origin of arcing signals is determined at the same time the arcing signals are being measured. This consequently increases the reliability of the electrical system as a whole. The invention is based on introducing more functions to protection from arcing, aimed at determining the origin of arcing and elimination of false alarms.

EFFECT: increased noise immunity, reliability of electrical systems.

2 cl, 2 dwg

Description

The invention relates to the field of fire safety and electric power, and in particular to methods and devices for preventing fires arising from malfunctions in electrical networks (ES) or electrical installations (EU) in rooms, structures, buildings, aircraft, ships, railway transport and other objects.

The operation of residential, domestic, industrial and other facilities is often accompanied by fires or explosions arising from malfunctions in electrical networks and electrical installations.

These malfunctions are especially dangerous during the operation of high-risk facilities: nuclear power facilities, mining industries, mining, facilities for the exploitation of toxic and explosive substances, storage and transportation of oil products and gas, as well as many other fire and explosive facilities for special, military and civil purposes.

To detect such faults, various methods for detecting sparking have been proposed. However, when implementing the indicated technical solutions in a widely ramified electric network loaded with a wide variety of different types of consumers, it became necessary to develop a method for automatically determining the place of sparking and controlling interference in it.

Known technical solution [1] for protection against spark current in the wiring. In accordance with this technical solution, an electric current of a controlled electrical network or an electrical installation is measured using a sensor D. From the measured current by filtering the first harmonic or the entire low-frequency spectrum, a signal of the second and / or higher harmonics is extracted, which characterizes the process of voltage recovery on a broken circuit when the spark current passes through a zero value, determined by the intensity and magnitude of this current, depending on the transition resistance, amplify it and straighten. The magnitude of the sparking current is calculated based on the measurement of the selected parameter (s) of the cycle "occurrence and suppression of the spark" (cycle) at its generating and / or decaying stages. At the same time, a warning signal is generated at the device’s output about the corresponding level of fire hazard and (or) a command to turn off the monitored section of the faulty network or electrical installation, coming to the information display unit and (or) to turn off the monitored section of the controlled network section or electrical installation.

There is a technical solution [2] for protection against spark current in electrical wiring, in which, in addition to solution [1], the following are introduced: the operation of direct measurement of the amplitude of pulses at the generating and (or) decaying stages of the cycle “occurrence and suppression of a spark”; the operation of measuring the number of pulses in the forming stage of the cycle, the amplitude of which exceeds the set value; the operation of generating the first harmonic signal from the spectrum of the measured current signal, from which the signals of short circuit currents, and (or) overload and (or) leakage, and (or) voltage of the electric network are extracted and measured; the operation of generating a warning signal and (or) disabling the controlled area.

As a drawback of the indicated technical solutions, it is necessary to note the impossibility of an addressable quick disconnection of the electric circuit in which the sparking has reached the upper fire hazard level. Performing this operation leads to the disconnection of the entire controlled electrical network and thereby, in addition to the dangerous circuit, disconnects normally functioning electrical circuits with working consumers. Automatic targeted determination of the specific place of sparking of each of the electrical circuits leads to the need to use devices in an amount equal to the number of possible potentially dangerous electrical circuits and even their potentially dangerous elements. This, firstly, significantly increases the cost of monitoring the power grid as a whole and, secondly, leads to an increase in the likelihood of the device generating a false danger signal in a normally functioning electric network. The above methods do not allow to achieve absolutely reliable identification of the sparking process in a capacious and branched electrical network, in which a wide range of interference is constantly present.

The aim of the invention is to improve the operational characteristics of the spark detection device. This goal is realized by introducing an automatic method for determining the place of sparking, which leads to the improvement of the quality control process of the functioning of the power grid. In addition, the proposed constructive change of the device in practice, the operation of protection systems against sparking of electrical networks provides the suppression of false fire hazard signals.

The goal is achieved by the fact that in the above technical solutions, taking into account the known operations of measuring and calculating the parameters of the cycle “occurrence - extinguishing of the spark”, the device A for measuring sparking is introduced and the existing device B is finalized by introducing an additional unit 12 in its design, designed to determine the place of sparking arising and flowing in the electric network in case of violation of the integrity of the electric circuit as a whole or its individual element. At the same time, by shunting the input of this device A for measuring sparking by a working working conductor (a normally functioning electric circuit), the appearance of any signals (false signals) at the output of device A for measuring sparking is almost completely eliminated. Unlocking this device occurs automatically when the integrity of the controlled circuit is violated, which by the nature of the phenomenon determines the occurrence and occurrence of the sparking process in it.

The proposed method operations are illustrated by the diagrams presented in figure 1 and figure 2.

Figure 1 shows, for example, a branched electrical network connected to a power source, for example, ~ 220 V 50 Hz, having ≥ n sections and controlled by the known device B with a sensor D included in it, which measures the total current of the entire electric network or electrical installation. When analyzing the measured current, device B selects its high-frequency spectrum, on the basis of which signals are generated corresponding to the sparking process occurring in a controlled electrical network or electrical installation. At the same time, a set of set values is formed and stored and the results of the generated signals are compared with them both by sparking and by fire hazard levels corresponding to them. The display can be carried out in the same way as in the sparking process, and (or) according to the fire hazard level corresponding to it. When sparking on the j-th section (see Figure 1) with the device A _ji connected to its i-th electric circuit (load H _ji ), the spark measurement device only disconnects this section by the automatic machine AB _j . In the event of sparking in the area with device A not connected to it, the entire controlled electrical network or electrical installation is turned off by the automatic machine AB (see Figure 1). The command for this shutdown is issued from the control unit 22 of the device B (see Figure 2). The specified command is formed on the basis of the analysis of information received from block 12 (at the output of all modules 13 logic 0, corresponding to the absence of an address) and block 21 of device B (the block generated a signal corresponding to exceeding the maximum permissible sparking) on any of the sections of the electrical network or electrical installation no connection to device A.

In the general case, this network has 1, 2, ... j ... n sections with the A spark measurement devices connected to them. Each of the j-th sections when exceeding the maximum permissible sparking in any of its electrical circuits, controlled by the modified device B together with device A, is turned off by the circuit breaker AB _j .

The refinement of device B consists in introducing into it a block 12 for determining the place of sparking, which, together with devices A for measuring sparking, equal in number to the controlled electrical circuits, form a functionally unified device for determining the place of sparking.

For example, shown is section 1 of the electric network, represented by electrical circuits No. 1, No. 2 ... No. i, loaded with the respective consumers N ₁₁ , H ₁₂ (lamps) and another N _1i load. The load is connected to the network by the corresponding switches B ₁ and (or) B ₂ , etc., and can also be connected directly, for example, through sockets or other mounting connection.

On fragments 1 and 2, described in detail in FIG. 2, structural solutions are considered that are an element of the device A for measuring sparking and suppressing false signals in the absence of sparking in a controlled circuit.

Fragment 1 of the electrical network contains an electrical circuit No. 1 with conductive cores (conductors) 1 and an insulating protective layer 4 or without it; non-conductive switch housing B1 with fixed 9 and movable 10 contacts; metal screws 3 for clamping the conductive conductors 1 to the fixed contacts 9 of the switch housing; movable contact 10 to create a galvanic connection between the fixed contacts 10 (when the switch B1 is on).

Fragment 2 of the electric network contains an electric circuit No. 2 with conductive cores (conductors) 1 and an insulating protective layer 4 or without it; adapter terminal block 2; metal screws 3 for clamping the conductive cores 7 to the metal base of the adapter 2 and thereby providing a galvanic connection between these conductive cores.

The working electric circuit (circuits No. 1, 2, etc.) is a closed, potentially dangerous section of current-carrying conductors 1, the connection quality of which is controlled by device A. This circuit can contain from one to ten or more closed switching elements (contacts of circuit breakers, switches, relays , load disconnectors, etc.), as well as hard mounting connections and the electrical wires themselves (potentially dangerous from the point of view of the possibility of violating their integrity), through which the normal load current flows.

Monitored sections of electrical circuits, each of which includes for simplicity only one element (mounting connection of switch B1 or load H ₁₂ ). The additional inclusion of an unlimited number of elements in a single controlled electric circuit does not change the physical essence of the phenomenon, since a violation of the integrity of one or more of any of these elements always leads to a violation of the integrity of the electric circuit as a whole, which does not change the parameters of the process of occurrence, leakage, or attenuation sparking.

Each device A is pre-connected with its input in parallel to a pre-selected closed section of a workable electrical circuit No. 1 and No. 2 ... No. 1, which does not have an integrity violation at the time the network starts operating, but which may occur in the future. We will call such a network section as potentially dangerous.

This device A contains electrical conductors 6 and elements 5 to ensure reliable electrical contact of these electrical conductors with the beginning and end of the controlled area of the working closed potentially dangerous i-th circuit. The final elements of the device are two conductors 11, designed to transmit a signal from device A to one of the modules 13 (modules 1, 2 ... ni) of block 12 for determining the place of sparking of device B (Figure 2).

So, for example, fragment 2 shows this device, which takes the signal between points 5 and 5, equal to the voltage value of the arc (spark) of the sparking process, and transfers it to the block 12 for determining the place of sparking (Figure 2).

In addition to the above structure, device A may include additional elements necessary for generating another desired signal, corresponding, for example, to the magnitude of the sparking current. On fragment 1, as such additional elements, element 7 is presented, for example, in the form of a capacitor and element 8. for example, in the form of a current transformer, for example, for matching and transmission to the block 12 for determining the place of sparking.

Device A for determining the place of sparking and suppressing false signals works as follows.

The operation of the device will be considered on the example of an electric circuit No. 1 (Figure 1 and fragment 7, Figure 2).

When the electrical network is in good condition, the elements 2, 3, 9 and 10 provide a reliable connection of the live parts 1 of the working electrical circuit No. 1, the resistance value of which is close to zero. The voltage drop in this section between the elements 5 is negligible, which corresponds to almost zero current value in circuit 6 and its high-frequency component. The zero value of the current by the matching element 8 (current transformer) is transmitted through the wire 11 to block 12. At the output of module 1 of this block, the magnitude of the spark signal is zero, which corresponds to the absence of signals at the input of the information display units and the formation of a command to turn off the monitored network section.

When the high-frequency component of the load current (noise) flows through the working conductor 1, the shunt resistance between points 5-5 (the resistance is almost zero) guarantees almost zero current value in the electric circuit 6, which ensures the required quality of suppressing this interference and at the output of element 8 some or a signal, including a false one, will be absent.

For a practically zero value, the value of a specific measurement result or output signal is taken that does not exceed the lower set value and is taken as a logical zero.

In the event of a malfunction associated with the formation of an ionized transition resistance at the place of occurrence of poor-quality contact between, for example, terminal 3 and the stationary contact 9 of the housing 2 of switch B1, a spark current appears in electrical circuit No. 1 (the current of free ions and electrons appears on the gap that appears), which manifests itself in the form of a sequence of cycles "occurrence - quenching of the spark." As a result, a high-frequency component of the electric current arises, superimposed on the total load current. On the secondary winding of the current transformer 8 appears a signal of the high-frequency spectrum, fed to the input of the block 12 determine the place of sparking - additions to the known device B.

The signal level is measured in module 1 (13), the result of which is further converted, for example, into a code value in module 15 for determining the place of sparking. If the value of the measured signal exceeds a predetermined minimum level stored in block 21, it is assigned, for example, a logical unit, otherwise a logical zero.

Moreover, if the assigned value is equal to one, the address of the place of sparking is generated in the same module 15, the current value of which is assigned, for example, one - the number of module 1 of the board 16, in which the signal from the output of the corresponding device A was measured (fragment 1, FIG. 2) .

The received address is transmitted to the module 17 displaying the number of places of sparking, which, along with module 18, is an integral part of the information display unit 19. At the same time, the address received in module 15 is transmitted to block 14 for generating a command to disable the monitored network section.

The zero value assigned in module 15 corresponds to the presence of permissible small sparking in the electric network in section 1 or to the presence of any level of sparking in other parts of the network that are not covered by devices A. Regardless of the latter situation, this sparking with a reduced level of noise immunity is in any case detected by the sensor D together with device B. At the same time, the fire hazard level is fixed on the information display unit, but the sparking address is not displayed on it or is displayed as, for example, zero.

The command to address the electrical network shutdown is generated by the control unit 22 with the simultaneous presence of the address in the block 12 and the sign of the highest level of fire danger of sparking generated by the block 14. In the absence of the address and the simultaneous presence of the highest level of fire hazard of sparking, the same control unit generates a shutdown command the entire electrical network circuit breaker AB (Figure 1).

The proposed technical solution differs from the known ones in that it contains operations and devices forming the address of the place of sparking and suppressing false signals in the absence of this sparking. This extends the functionality of currently existing methods and devices for fire prevention in the event of malfunctions in the electrical network and electrical installation.

In the scientific and technical literature, no technical solutions with the above set of features were found. Therefore, these differences allow us to conclude that the claimed technical solution meets the criterion of NOVELTY.

Moreover, the purpose of the invention is achieved by the entire set of operations, elements and relationships introduced, which was not known until the date of application of the technical solution, which allows us to conclude that the proposed technical solution meets the criterion of SIGNIFICANT DIFFERENCES.

As a result of the implementation of this invention at industrial and domestic facilities, as well as in the quality control structures of their design and operation, the overall safety of the operation of these facilities and their fire safety, in particular, are increased. In addition, the cost of implementing protection to prevent fires and explosions from malfunctions in electrical networks and electrical installations is reduced, and the reliability of electrical systems as a whole is increased. The final statement is as follows:

- determination of the place of sparking by using simple and cheap devices A by the number of potential points of sparking and additionally modified only one device B is more economical both in the cost of the devices and in their operation instead of using an equivalent amount of expensive existing devices B (by the number of the same potential sparking points) ;

- the proposed technical solution in the absence of sparking in the electrical network virtually eliminates the generation of false signals at the output of the device.

The implementation of this invention will reduce the number of cases of fire in residential and industrial premises, structures, buildings, aircraft, ships, railway transport and other objects using electrical networks and electrical installations. In addition, the number of cases of electric shock to a person, as well as the incapacitation of household and other equipment with an unacceptable decrease in voltage in the electric network, will decrease.

The introduction of devices that implement the proposed method involves the use of serial components and components. This does not require the restructuring of industrial enterprises and private firms to produce a new product range.

The economic and moral gain from the implementation of the invention is determined by the number of lives saved, as well as the number and cost of residential, industrial and other objects saved from fires by applying the proposed technical solution.

Thus, the introduction of the proposed method of preventing fire in the event of a malfunction in the electrical network or electrical installation will increase the protection of people, residential, industrial and other objects from the damaging effects of fires, as well as provide significant savings in material and financial resources of each citizen and the state as a whole.

INFORMATION SOURCES

1. Patent No. 2254615, IPC 7 G08B 17/06, G08B 25/10.

2. International patent application No.PCT / RU 2005/000251 for a patent for an invention, published November 16, 2006.

Claims (2)

1. A method of preventing a fire from a malfunction in an electrical network or electrical installation, comprising measuring the electric current of a controlled branched electrical network or electrical installation; signal generation by sparking from the high-frequency spectrum of the measured current; the formation and storage of a set of set values for the generated spark signals and comparing the generated signals with them; the formation of the result of the comparison of the command to display information and / or the formation of the command to turn off the monitored electrical network or electrical installation and its execution, characterized in that a parallel closed electrical circuit of at least one potentially dangerous section of a branched electrical network or electrical installation, connect the input spark measuring devices so that in good condition of said section, the input of said device is shunted, the voltage value is measured The electrical arc (spark) and / or sparking current controlled by breakage of said electrical circuit; form a signal defining the place of sparking - the location of the damaged electric circuit in the electrical network or installation; display the address of the location of this section and / or disconnect this section with a damaged electrical circuit, and the formation of a command to turn off a controlled electrical network or electrical installation and its execution is carried out when the highest fire hazard level is reached. 2. The device for implementing the method according to claim 1, comprising a unit for measuring electric current of a monitored branched electric network or electrical installation, a unit for generating a signal for sparking from the high-frequency spectrum of the measured current, a unit for generating and storing a set of set values for the generated signals for sparking and comparing with them the generated signals, the formation unit for the result of comparing the command to display information and / or the unit for generating the command to turn off the controlled electronic network or electrical installation, and its execution unit, characterized in that it contains an input connected in parallel to a closed electrical circuit of at least one potentially dangerous section of a branched electrical network or electrical installation, a spark measurement device in which voltage is measured at its input an electric arc (spark) and / or spark current, and in good condition of said section, the input of said device is bridged by said circuit, as well as a unit for determining places and the spark, in which the magnitude of the arc voltage (spark) and / or the spark current is measured, determines the address of the place of sparking, i.e. said controlled area, the input of this unit being connected to the output of the sparking measurement device and to the output of the unit for generating and storing the set of set values for the generated sparking signals, and the output of the unit for determining the place of sparking is connected to the information display unit and / or to the shutdown command generation unit controlled section of the electrical network or electrical installation, and the formation of the team to turn off the controlled electrical network or electrical installation and its execution e appropriate blocks are carried out upon reaching the highest level of fire hazard.

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