Safety evaluation method for annular metal coupling surge pulse energy

Abstract

The invention discloses a safety evaluation method for annular metal coupling surge pulse energy, and the method comprises the steps: cutting a part of length of a power transmission cable carrying surge pulses, and building a space cylindrical coordinate system with the head end of the part of length of the power transmission cable as an original point; measuring coordinates of the annular metal in the space cylindrical coordinate system, and substituting the coordinates into a calculation formula to calculate the electric field intensity; energy storage element parameters are estimated according to the energy storage type metal structure parameters; the discharge spark energy is calculated according to a calculation formula provided by the invention; measuring physical parameters of the annular metal, and substituting the physical parameters into the calculation formula of the induced voltage of the annular metal and the calculation formula of the equivalent resistance of the annular metal; substituting the solved induced voltage and equivalent resistance into a calculation formula of discharge spark energy W; and judging whether the current working environment is safe or not according to the explosive gas safety criterion.

Description

Technical field:

[0001] The present application relates to the field of prevention and treatment of coal mine gas explosions, in particular to a safety evaluation method for annular metal coupling 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 serious accidents in coal mines, which will cause immeasurable casualties and property losses. Among them, the metal structure in the coal mine that is equivalent to a receiving antenna can couple and absorb the electromagnetic field energy generated by the surrounding radiation source, generate an induced voltage, and form an active circuit inside. Under certain conditions, discharge sparks can be generated, and there is a risk of igniting explosive gases. To this end, my country has formulated 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 transmitting equipment used in explosive environments underground in coal mines cannot exceed 6W.

[0003] Surge is a common transient electromagnetic interference in power equipment. Its main source is direct or indirect lightning strikes on the outside of the power equipment and the start-up and shutdown of the power equipment or power supply system failure. Surge pulses can generate extremely strong electromagnetic fields around transmission cables, which have a certain impact on the electromagnetic environment underground in coal mines and will affect the normal operation of monitoring, communication and control systems underground. If a metal structure is located around a transmission cable carrying a surge pulse, it 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 inside the metal structure. This process is essentially no different from the process of metal structure coupling and absorbing the electromagnetic wave energy emitted by the transmitter of wireless communication equipment. In theory, there is a possibility of igniting explosive gases. However, the current research on the electromagnetic wave energy radiated by metal structure coupling surge pulses is a blank area.

[0004] The present application proposes a safety evaluation method for annular metal coupling surge pulse energy, filling the 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 a gas explosive environment in a coal mine tunnel.

[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] The present application provides a method for safety assessment of annular metal coupling surge pulse energy, comprising:

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

[0009] Step 2: measuring the coordinates of the annular 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 annular metal;

[0010] Step 3: measuring the physical parameters of the annular metal, and calculating the induced voltage U of the annular metal and the equivalent resistance R of the annular metal based on the electric field strength and the physical parameters of the annular 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 safety criterion of explosive gas, 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 annular metal being an annular metal with a multi-turn coil structure.

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

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

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

[0019]

[0020] Where: Z0 is the characteristic impedance of free space, 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 the 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, where the copper conductivity value σ=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 calculation formula is:

[0025]

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

[0027] Optionally, according to the safety assessment 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 aims to address the gap in the field of safety assessment of electromagnetic wave energy of metal structure coupled surge pulse radiation, and proposes a safety assessment method for annular metal coupled surge pulse energy to improve safety in coal mines. This technology is a non-explosive evaluation method, saving the cost of explosive safety testing. This technology is simple to calculate, highly practical, and saves manpower and time costs. Description of the drawings:

[0029] Figure 1 It 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 evaluation of ring metal coupling surge pulse energy provided by an embodiment of the present application. Specific implementation method:

[0031] In order to solve the problems in the above background technology, the present application provides a safety evaluation method for energy storage metal coupling electromagnetic wave energy. The method calculates the electric field strength E generated at the location of the ring metal by establishing a space cylindrical coordinate system of the transmission cable; calculates the induced voltage U and equivalent resistance R of the ring metal by measuring the physical parameters of the transmission cable and the ring metal, and then calculates the discharge spark energy W; finally, according to the safety criterion of explosive gas, it determines whether the current working environment is safe, and if it is dangerous, gives the safe distance of the ring metal.

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

[0033]

[0034] Formula 2: Formula 3: Formula 4: The physical parameters include: the number of turns of the annular metal coil n, the area of ​​the annular metal ring A, the circumference of the annular metal coil l, the radius of the annular metal coil wire a, and the annular metal conductivity σ. Here, the copper conductivity value 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: Where: μ0 is the vacuum magnetic permeability, in air μ0≈4π×10 -7 H / m.

[0035] The applicable scenario of the safety assessment method of the present application is that the metal structure is a multi-turn coil annular metal structure, and the environment in which the annular metal is located is an explosive environment in a coal mine tunnel where gas exists. The minimum ignition energy of the gas is selected to be 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 location of the ring metal as the center point. If the length of the transmission cable is greater than 100m, 100m is cut. If it is less than 100m, a portion of the length is cut in such a way that the cut length is the entire 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, such as Figure 1 shown.

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

[0039] Where: Z0 is the characteristic impedance of free space, 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 annular metal, including: 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 conductivity σ of the annular 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: 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 environment where the ring metal is located is an explosive environment in a coal mine tunnel where the gas exists. The safety evaluation method includes: Step 1: Cut off a portion of the length of the transmission cable carrying the surge pulse, and establish a space cylindrical coordinate system with the head end of the portion of the length of the transmission cable as the origin, and the propagation direction of the surge pulse is the positive direction of the Z axis; Step 2: measuring the coordinates Q (r, φ, z) of the annular 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 annular metal; Step 3: measuring the physical parameters of the annular metal, and calculating the induced voltage U of the annular metal and the equivalent resistance R of the annular metal based on the electric field strength and the physical parameters of the annular 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 safety criterion of explosive gas, 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, characterized in that: The annular metal is an annular metal with a multi-turn coil structure.

3. The safety assessment method according to claim 1, characterized in that: The minimum ignition energy of the gas is 1600 μJ.

4. The safety evaluation method according to claim 1, characterized in that: The method of cutting off a portion of the length of the power transmission cable carrying the surge pulse includes: setting the position of the annular metal as the center point and cutting off on both sides. If the length of the power 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 power transmission cable.

5. The safety assessment method according to claim 1, characterized in that: The frequency f of the surge pulse radiation electromagnetic wave is 1 MHZ.

6. The safety assessment method according to claim 1, characterized in that: The calculation formula of the electric field strength E is: Where: Z0 is the characteristic impedance of free space, 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 the Q(r,φ,z) point; cos(θ)=z / x; x=(z 2 +r 2 ) 1 / 2 。 7. The safety assessment method according to claim 1, characterized in that: 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 conductivity σ of the annular 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 6, 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 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.

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