A safety assessment method for ring-shaped metal-coupled surge pulse energy

Abstract

The present invention discloses a safety evaluation method for annular metal coupled surge pulse energy. The method comprises: cutting a portion of a transmission cable carrying a surge pulse, establishing a space cylindrical coordinate system with the head end of the portion of the transmission cable as the origin; measuring the coordinates of the annular metal in the space cylindrical coordinate system, and substituting the coordinates into a calculation formula to calculate the electric field strength; estimating energy storage element parameters based on energy storage metal structure parameters; calculating discharge spark energy according to a calculation formula provided by the present invention; measuring physical parameters of the annular metal, and substituting the physical parameters into a calculation formula for the induced voltage of the annular metal and a calculation formula for the equivalent resistance of the annular metal; substituting the solved induced voltage and equivalent resistance into a calculation formula for the discharge spark energy W; and judging whether the current working environment is safe according to an explosive gas safety criterion.

Description

Technical field:

[0001] This application relates to the field of prevention and treatment of coal mine gas explosions, especially to a safety evaluation method for annular metal-coupled surge pulse energy in underground coal mines. Background technology:

[0002] Safety accidents caused by gas explosions, gas-coal dust explosions, and coal dust explosions are considered major accidents in coal mines, resulting in immeasurable casualties and property losses. Metal structures in coal mines that act as receiving antennas can couple and absorb electromagnetic field energy generated by surrounding radiation sources, generating induced voltages and forming active internal circuits. Under certain conditions, these structures can produce discharge sparks, posing a risk of igniting explosive gases. To this end, my country has developed the relevant safety document GB / T 3836.1-2021, "Explosive Atmospheres - Part 1: General Requirements for Equipment," which stipulates that the radio frequency power of wireless transmitters used in explosive environments underground in coal mines must not exceed 6W.

[0003] Surges are common transient electromagnetic interference in power equipment. Their primary sources are direct or indirect lightning strikes from external devices, as well as internal startups and shutdowns or power supply system failures. Surge pulses can generate extremely strong electromagnetic fields around transmission cables, impacting the electromagnetic environment underground in coal mines and affecting the normal operation of monitoring, communication, and control systems. If metal structures are located around transmission cables carrying surge pulses, they will also couple and absorb the radiated electromagnetic field energy generated by the surge pulse flowing through the transmission cable, thereby generating an induced voltage within the metal structure. This process is essentially the same as the process by which metal structures couple and absorb the electromagnetic wave energy emitted by the transmitter of wireless communication equipment, and theoretically, there is the potential for igniting explosive gases. However, current research on the coupling of surge pulse radiated electromagnetic wave energy to metal structures is a blank area.

[0004] This application proposes a safety evaluation method for ring-shaped metal-coupled surge pulse energy, filling a gap in this safety field. Summary of the invention:

[0005] In order to solve the problems in the above background technology, the present invention provides a safety evaluation method for annular metal coupling surge pulse energy applicable to coal mine tunnels with a gas explosive environment.

[0006] The safety evaluation method provided by the present invention is intended to evaluate the safety of annular metal when encountering surge pulse energy in a coal mine tunnel, so as to ensure the safety of operation in a gas explosive environment.

[0007] This application provides a safety assessment method for ring-shaped metal-coupled surge pulse energy, including:

[0008] Step 1: Cut a portion of the transmission cable carrying the surge pulse, establish a space cylindrical coordinate system with the beginning of the portion of the transmission cable as the origin, and the surge pulse propagation direction is the positive direction of the Z axis;

[0009] Step 2: measuring the coordinates of the ring-shaped metal in the space cylindrical coordinate system, and calculating the electric field intensity E generated by the partial length transmission cable at the location of the ring-shaped metal;

[0010] Step 3: measuring the physical parameters of the ring-shaped metal, and calculating the induced voltage U of the ring-shaped metal and the equivalent resistance R of the ring-shaped metal based on the electric field strength and the physical parameters of the ring-shaped metal;

[0011] Step 4: Based on the induced voltage U and the equivalent resistance R, calculate the discharge spark energy W:

[0012]

[0013] Where: T is the ignition time of gas, T = 200μS;

[0014] Step 5: According to the explosive gas safety criterion, the discharge spark energy W is compared with the minimum maximum ignition energy of the gas to determine whether the current working environment is safe.

[0015] Optionally, according to the safety evaluation method described in the embodiment of the present application, the safety evaluation method is applicable to the case where the annular metal is an annular metal with a multi-turn coil structure.

[0016] Optionally, according to the safety assessment method described in the embodiment of the present application, the minimum ignition energy of the gas is selected to be 1600 μJ. Optionally, according to the safety assessment method described in the embodiment of the present application, cutting off a portion of the length of the transmission cable carrying the surge pulse includes: setting the position of the annular metal as the center point and cutting off in both directions, if the length of the transmission cable is greater than 100m, cutting off 100m, and if it is less than 100m, then the cut length is the entire length of the transmission cable.

[0017] Optionally, according to the safety assessment method described in the embodiment of the present application, the surge pulse radiation electromagnetic wave frequency f is 1 MHZ.

[0018] Optionally, according to the safety evaluation method described in the embodiment of the present application, the electric field strength E is calculated as follows:

[0019]

[0020] Where: Z0 is the free space characteristic impedance, Z0 = 377Ω; ξ is the surge compensation coefficient, ξ = 3506.6; Ip is the peak value of the surge pulse current; c is the speed of light in free space; t is time; α is the wavefront attenuation coefficient, α = 0.12895; β is the wavetail attenuation coefficient, β = 0.12905; d is the cut length of the transmission cable; x is the distance from the origin to the Q(r, φ, z) point; cos(θ) = z / x; x = (z 2 +r 2 ) 1 / 2 .

[0021] Optionally, according to the safety evaluation method described in the embodiment of the present application, the physical parameters of the annular metal include: the number of turns n of the annular metal coil, the area A of the annular metal ring, the circumference l of the annular metal coil, the radius a of the annular metal coil wire, and the annular metal conductivity σ. Here, the copper conductivity value σ is selected as 5.8×10 7 S / m.

[0022] Optionally, according to the safety assessment method described in the embodiment of the present application, the calculation formula of the induced voltage U is:

[0023]

[0024] Where: λ is the wavelength of the surge pulse radiation electromagnetic wave, Optionally, according to the safety evaluation method described in the embodiment of the present application, the equivalent resistance R is calculated as follows:

[0025]

[0026] Where: μ0 is the vacuum magnetic permeability, in air μ0≈4π×10 -7 H / m.

[0027] Optionally, according to the safety evaluation method described in the embodiment of the present application, the safety criterion is: if the discharge spark energy W is greater than the minimum ignition energy of the gas, it is judged to be dangerous; if the discharge spark energy is less than or equal to the minimum ignition energy of the gas, it is judged to be safe.

[0028] This application addresses the gap in the field of safety assessment of electromagnetic wave energy radiated by coupled surge pulses from metal structures. It proposes a safety assessment method for annular metal-coupled surge pulse energy, improving safety in underground coal mines. This technology is a non-explosive assessment method, reducing the cost of explosive safety testing. The method is computationally simple, highly practical, and saves both labor and time. Description of the drawings:

[0029] Figure 1 This is a schematic diagram of a transmission cable model with a partial length carrying a surge pulse provided by an embodiment of the present application.

[0030] Figure 2 This is a flow chart of the safety assessment of ring metal coupling surge pulse energy provided by one embodiment of the present application. Specific implementation method:

[0031] To address the issues in the aforementioned background technology, this application provides a safety assessment method for energy storage metal-coupled electromagnetic wave energy. This method establishes a spatial cylindrical coordinate system for the transmission cable to calculate the electric field strength E generated at the location of the ring metal. By measuring the physical parameters of the transmission cable and the ring metal, the induced voltage U and equivalent resistance R of the ring metal are calculated, and the discharge spark energy W is then calculated. Finally, based on the explosive gas safety criterion, the safety of the current working environment is determined. If dangerous, the safe distance from the ring metal is determined.

[0032] Figure 2 This is a flow chart of the safety assessment of ring metal coupling surge pulse energy provided by one embodiment of the present application, wherein Formula 1:

[0033]

[0034] Formula 2: Formula 3: Formula 4: The physical parameters include: the number of turns n of the annular metal coil, the area A of the annular metal ring, the circumference l of the annular metal coil, the radius a of the annular metal coil wire, and the annular metal conductivity σ. Here, the copper conductivity value σ is selected as 5.8×10 7 S / m, the induced voltage U of the ring metal is calculated based on the physical parameters of the ring metal and the electric field strength E: The equivalent resistance R of the ring metal is: Where: μ0 is the vacuum magnetic permeability, in air μ0≈4π×10 -7 H / m.

[0035] The applicable scenario of the safety evaluation method of this application is that the metal structure is a multi-turn coil ring metal structure, and the environment in which the ring metal is located is an explosive environment in a coal mine tunnel where gas exists. The minimum ignition energy of the gas is selected as 1600μJ, and the ignition time T is 200μS.

[0036] The specific implementation plan of the safety evaluation method of this application is as follows:

[0037] (1) The transmission cable carrying the surge pulse is cut to both sides with the position of the ring metal as the center point. If the transmission cable length is greater than 100m, 100m is cut. If it is less than 100m, a portion of the length is cut to the full length of the transmission cable. A spatial cylindrical coordinate system is established with the head end of the partial length transmission cable as the origin. The surge pulse propagation direction is the positive direction of the Z axis, as shown in the following example: Figure 1 shown.

[0038] (2) Measure the coordinates Q(r, φ, z) of the ring metal in the spatial cylindrical coordinate system and calculate the electric field strength E generated by a portion of the transmission cable at the location of the ring metal:

[0039] Where: Z0 is the free space characteristic impedance, Z0 = 377Ω; ξ is the surge compensation coefficient, ξ = 3506.6; I p is the peak value of the surge pulse current; c is the speed of light in free space; t is the time; θ is the angle parameter between the ring metal and the partial length of the transmission cable; α is the wavefront attenuation coefficient, α = 0.12895; β is the wavetail attenuation coefficient, β = 0.12905; d is the cut length of the transmission cable; x is the distance from the origin to the Q(r,φ,z) point; cos(θ) = z / x; x = (z 2 +r 2 ) 1 / 2 .

[0040] (3) Measure the physical parameters of the ring metal, including the number of turns n of the ring metal coil, the area A of the ring metal ring, the circumference l of the ring metal coil, the radius a of the ring metal coil wire, and the conductivity σ of the ring metal. Here, the conductivity value of copper is selected as σ = 5.8 × 10 7 S / m, the induced voltage U of the ring metal is calculated based on the physical parameters of the ring metal and the electric field strength E: The equivalent resistance R of the ring metal is: Where: μ0 is the vacuum magnetic permeability, in air μ0≈4π×10 -7 H / m; f is the frequency of the surge pulse radiation electromagnetic wave, f=1MHZ.

[0041] (4) Calculate the discharge spark energy W based on the induced voltage U and the equivalent resistance R:

[0042] (5) Determine whether the current working environment is safe based on the explosive gas safety criteria.

[0043] The safety criterion for explosive gas is: if the discharge spark energy W is greater than the minimum ignition energy of the gas, it is judged to be dangerous; if the discharge spark energy is less than or equal to the minimum ignition energy of the gas, it is judged to be safe.

Claims

1. A safety evaluation method for ring metal coupling surge pulse energy, characterized in that: The safety evaluation method is applicable to the case where the ring metal is located in an explosive environment with gas in a coal mine tunnel. The safety evaluation method includes: Step 1: Cut a portion of the transmission cable carrying the surge pulse, establish a spatial cylindrical coordinate system with the beginning of the portion of the transmission cable as the origin, and the surge pulse propagation direction is the positive direction of the Z axis; Step 2: measuring the coordinates Q(r, φ, z) of the ring metal in the space cylindrical coordinate system, and calculating the electric field strength E generated by the partial length transmission cable at the location of the ring metal; Step 3: measuring the physical parameters of the ring-shaped metal, and calculating the induced voltage U of the ring-shaped metal and the equivalent resistance R of the ring-shaped metal based on the electric field strength and the physical parameters of the ring-shaped metal; Step 4: Based on the induced voltage U and the equivalent resistance R, calculate the discharge spark energy W: Where: T is the ignition time of gas, T = 200μS; Step 5: According to the explosive gas safety criterion, the discharge spark energy W is compared with the minimum maximum ignition energy of the gas to determine whether the current working environment is safe.

2. The safety assessment method according to claim 1, wherein: The annular metal is an annular metal with a multi-turn coil structure.

3. The safety assessment method according to claim 1, wherein: The minimum ignition energy of the gas is selected to be 1600 μJ.

4. The safety assessment method according to claim 1, wherein: The method of cutting off a portion of the length of the transmission cable carrying the surge pulse includes: setting the position of the annular metal as the center point and cutting off to both sides. If the length of the transmission cable is greater than 100m, 100m is cut off; if it is less than 100m, the cut length is the entire length of the transmission cable.

5. The safety assessment method according to claim 1, wherein: The frequency f of the surge pulse radiation electromagnetic wave is 1 MHz.

6. The safety assessment method according to claim 5, characterized in that: The calculation formula of the electric field strength E is: Where: Z0 is the free space characteristic impedance, Z0 = 377Ω; ξ is the surge compensation coefficient, ξ = 3506.6; I p is the peak value of surge pulse current; c is the speed of light in free space; t is time; θ is the angle parameter between the annular metal and the partial length transmission cable; α is the wavefront attenuation coefficient, α=0.12895; β is the wavetail attenuation coefficient, β = 0.12905; d is the cut length of the transmission cable; x is the distance from the origin to point Q (r, φ, z); cos (θ) = z / x; x=(z 2 +r 2 ) 1 / 2 。 7. The safety assessment method according to claim 6, characterized in that: The physical parameters of the ring metal include: the number of turns n of the ring metal coil, the area A of the ring metal ring, the circumference l of the ring metal coil, the radius a of the ring metal coil wire, and the conductivity σ of the ring metal. Here, the conductivity value of copper is selected as σ = 5.8×10 7 S / m.

8. The safety assessment method according to claim 7, characterized in that: The calculation formula of the induced voltage U is: Where: λ is the wavelength of the surge pulse radiation electromagnetic wave, 9. The safety assessment method according to claim 7, characterized in that: The calculation formula of the equivalent resistance R is: Where: μ0 is the vacuum magnetic permeability, in air μ0≈4π×10 -7 H / m.

10. The safety assessment method according to claim 3, characterized in that: The safety criterion is: if the discharge spark energy W is greater than the minimum ignition energy of the gas, it is determined to be dangerous; if the discharge spark energy is less than or equal to the minimum ignition energy of the gas, it is determined to be safe.

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