A mine cable detection device and method based on a local discharge signal propagation coefficient

Abstract

The application discloses a kind of mine cable detection device and method based on local discharge signal propagation coefficient, including signal generation system, cable model and measurement system;Local discharge calibrator is connected with cable first end, for generating certain electric charge amount of local discharge signal;Coaxial cable is respectively connected at cable two ends, and is connected with oscilloscope in measurement system, respectively collect signal emitted by local discharge calibrator and local discharge signal at cable end;Oscilloscope in measurement system is connected with computer, network analyzer, computer and network analyzer are used to process local discharge signal at cable end, obtain the frequency spectrum characteristics of signal, so that the propagation coefficient of local discharge signal in the cable is obtained.Compared with theoretical value, the uniform distribution coefficient of cable insulation is obtained, so as to evaluate the state of cable.The invention obtains the uniform distribution coefficient of cable insulation based on the propagation coefficient of local discharge signal in one-way propagation in cable, which can effectively evaluate the running state of cable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cable state monitoring, in particular to a mine cable detection device and method based on partial discharge signal propagation coefficient. BACKGROUND

[0002] With the development of coal industry, the mechanical and electrical equipment used in coal mines is constantly being updated and transformed. Since coal mines are generally underground, there are large power loads, explosive gas and coal dust, small space, relatively humid air, large water inflow, and frequent equipment movement. If a cable fault occurs, it will not only affect work efficiency, but also may cause serious damage to electrical equipment, electric shock, electrical fire, and even gas and coal dust explosion.

[0003] Partial discharge phenomenon can reflect the degree of deterioration of cable insulation to some extent, which can be used to judge the running state of mine cable. When the cable line is in normal operation, only power frequency 50Hz signal exists on the line. When partial discharge occurs in the cable, rich high-frequency signals will be generated on the line. If the high-frequency signals can be analyzed, and the characteristics of their propagation in power cables are studied, the running state of the cable can be evaluated based on this, which is of great significance for early warning of cable fault hazards, ensuring the safety of personnel, property and production equipment. SUMMARY

[0004] The present application provides a mine cable detection device and method based on partial discharge signal propagation coefficient, which has a simple structure and can effectively measure the actual propagation coefficient of the one-way propagation of partial discharge signals in the cable. The insulation distribution coefficient of the cable can be obtained from the ratio of the actual propagation coefficient and the theoretical propagation coefficient, which reflects the insulation condition and running state of the cable, and is beneficial to predicting its service life.

[0005] To achieve the above purpose, a mine cable detection device and method based on partial discharge signal propagation coefficient, comprising a single-core cable model, a signal generating system, and a measuring system.

[0006] The single-core cable model, signal generating system and measuring system are connected in sequence.

[0007] The single-core cable model comprises, in sequence from the outside to the inside, a cable sheath, a shielding layer, an outer semiconductor layer, an insulation layer, an inner semiconductor layer and a conductor layer.

[0008] The two ends of the single-core cable model are respectively connected to coaxial cables, the first end is connected to a partial discharge calibrator, and the last end is connected to an oscilloscope in the measuring system.

[0009] The signal generating system is composed of a partial discharge calibrator that can generate partial discharge signals, which is connected to the first end of the single-core cable model.

[0010] The measuring system is composed of an oscilloscope, a computer and a network analyzer. The oscilloscope is connected with the cable at both ends, collects the signal emitted by the partial discharge calibrator and the partial discharge signal at the tail end of the cable, and is connected with the computer and the network analyzer which are also part of the measuring system.

[0011] Further, the partial discharge calibrator at the head end of the cable can generate partial discharge signals with different charge amounts, and the calculation formula is:

[0012]

[0013] Wherein: U is the peak voltage of the partial discharge signal, r1 is the radius of the conductor layer (106), r2 is the radius of the insulating layer (104), ε is the dielectric constant of the insulating material, k is the proportional coefficient, and the value is 2.82.

[0014] A mine cable detection method based on the propagation coefficient of partial discharge signal, specifically comprising the following steps:

[0015] Start the partial discharge calibrator of the system, give a certain charge amount of partial discharge excitation at the head end of the cable, and collect the output signal at the tail end of the cable with an oscilloscope respectively;

[0016] At the same time of collecting the output signal, the output signal is analyzed and processed through the computer and the network analyzer connected with the oscilloscope, and the frequency spectrum distribution is obtained;

[0017] The actual propagation coefficient γ1 of the partial discharge signal in the cable is calculated, and the calculation formula is:

[0018]

[0019] Wherein: L is the length of the cable, U out is the output signal, and U in is the input signal.

[0020] Further, in step a, the charge of the partial discharge calibrator is determined according to the formula

[0021] Further, in step b, the time domain result obtained in the oscilloscope is converted into the frequency domain form by Fourier transform:

[0022] Further, the theoretical propagation coefficient γ0 of the partial discharge signal in the cable is solved, and the first order parameters R, L, C and G of the single core cable model are determined:

[0023] The solution formula of the resistance R is

[0024] ​

[0025] ω = 2πf

[0026] Where: μ0 is the vacuum permeability, μ co is the permeability of the conductor, σ co is the conductivity of the conductor, f is the signal frequency.

[0027] The formula for solving the inductance L is:

[0028]

[0029] When solving the capacitance C, the inner semiconductor layer (105), the insulating layer (104), and the outer semiconductor layer (103) need to be solved respectively, and the formula is:

[0030]

[0031] Where: ε x (ω) is the dielectric constant of each layer, and ε0 is the vacuum dielectric constant.

[0032] From the capacitance value of each layer, the capacitance value of the cable can be obtained, and the formula is:

[0033]

[0034] Where: C sc1 is the capacitance of the inner semiconductor layer (105), C sc2 is the capacitance of the outer semiconductor layer (103), and C ins is the capacitance of the insulating layer (104).

[0035] The formula for calculating the conductance is:

[0036]

[0037] Where: d sc1 is the thickness of the inner semiconductor layer (105), d ins is the thickness of the insulating layer (104), and d sc2 is the thickness of the outer semiconductor layer (103), and σ ins is the conductivity of the insulating layer.

[0038] The theoretical propagation coefficient γ0 of the partial discharge signal when propagating unidirectionally in the cable is:

[0039]

[0040] Further, the insulation uniform distribution coefficient P of the cable is calculated, and the formula is:

[0041]

[0042] The insulation uniformity coefficient P can be used to assess the insulation condition and operating status of a cable. When 0.9 ≤ P ≤ 1.2, the cable insulation condition is good and the operating status is stable; when P > 1.2 or P < 0.9, the cable insulation is severely aged and the operating status is unstable.

[0043] Compared with existing technologies, this paper proposes a detection device and method for mining cables based on the propagation coefficient of partial discharge signals. It sets up a single-core cable model, a signal generation system, and a measurement system. A partial discharge signal is emitted through a partial discharge calibrator to simulate the operation of a power cable when partial discharge occurs. While simplifying the system, it makes it closer to actual working conditions, ensuring measurement accuracy. The signals at both ends of the single-core cable are measured using an oscilloscope, and the measured signals are analyzed in the frequency domain using a PC to determine their propagation coefficient. This coefficient is then compared with theoretical calculations to obtain the uniform distribution coefficient of the cable's insulation. This provides a reference for evaluating the cable's insulation performance and aging condition, and is beneficial for predicting the cable's service life. Attached Figure Description

[0044] Figure 1 This is an overall distribution diagram of the measuring device of the present invention;

[0045] Figure 2 This is a flowchart of the measurement method of the present invention;

[0046] In the picture:

[0047] 1. Power cable model; 2. Signal generation system; 3. Measurement system; 101. Cable sheath; 102. Shielding layer; 103. Outer semiconductor layer; 104. Insulation layer; 105. Inner semiconductor layer; 106. Conductor layer; 201. Partial discharge calibrator; 301. Oscilloscope; 302. Network analyzer; 303. Computer Detailed Implementation

[0048] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the invention.

[0049] like Figure 1 As shown, a detection device and method for mining cables based on the propagation coefficient of partial discharge signals includes a single-core cable model 1, a signal generation system 2, and a measurement system 3.

[0050] The single-core cable model 1, signal generation system 2, and measurement system 3 are connected in sequence.

[0051] The single-core cable model comprises, from the outside to the inside, a cable sheath 101, a shielding layer 102, an outer semiconductor layer 103, an insulation layer 104, an inner semiconductor layer 105, and a conductor layer 106. Both ends of the single-core cable model 1 are connected to coaxial cables, with the first end connected to a partial discharge calibrator 201 and the last end connected to an oscilloscope 301 in the measurement system 3.

[0052] The signal generation system consists of a partial discharge calibrator 201 that can generate partial discharge signals, connected to the beginning of the single-core cable model 1.

[0053] The measurement system 3 consists of an oscilloscope 301, a computer 302, and a network analyzer 303. The oscilloscope 301 is connected to both ends of the cable to collect signals from the partial discharge calibrator 201 and the partial discharge signal from the cable tail end, and is connected to the computer 302 and the network analyzer 303, which are also part of the measurement system 3.

[0054] Furthermore, the partial discharge calibrator 201 at the cable end can generate partial discharge signals with different charge amounts, calculated using the following formula:

[0055]

[0056] Where: U is the peak voltage of the partial discharge signal, r1 is the radius of the conductor layer (106), r2 is the radius of the insulating layer (104), ε is the dielectric constant of the insulating material, and k is the proportionality coefficient, which is taken as 2.82.

[0057] A detection method for mining cables based on the propagation coefficient of partial discharge signals specifically includes the following steps:

[0058] The partial discharge calibrator 201 of the system is activated, and a certain amount of partial discharge excitation with charge is given at the beginning of the cable. The output signal at the end of the cable is collected by the oscilloscope 301.

[0059] While acquiring the output signal, the computer 302 and network analyzer 303 connected to the oscilloscope 301 analyze and process the output signal to obtain its spectrum distribution.

[0060] The formula for calculating the actual propagation coefficient γ1 of the partial discharge signal in the cable is as follows:

[0061]

[0062] Where: L is the cable length, U out For the output signal, U in This is the input signal.

[0063] Furthermore, in step a, according to the formula Determine the charge emitted by the partial discharge detector 201

[0064] Furthermore, in step b, the time-domain result obtained from the oscilloscope 301 is transformed into a frequency-domain result using Fourier transform:

[0065] Furthermore, the theoretical propagation coefficient γ2 of the partial discharge signal in the cable is solved to determine the primary parameters R, L, C, and G of the single-core cable model 1:

[0066] The formula for calculating resistance R is:

[0067]

[0068] ω=2πf

[0069] Where: μ0 is the free permeability, μ co Let σ be the magnetic permeability of the conductor. co Let f be the conductivity of the conductor, and f be the signal frequency.

[0070] The formula for calculating the inductance L is:

[0071]

[0072] When solving for capacitance C, it is necessary to solve for the inner semiconductor layer (105), the insulating layer (104), and the outer semiconductor layer (103) separately. The formula is as follows:

[0073]

[0074] Where: ε x (ω) represents the dielectric constant of each layer of the medium, and ε0 represents the vacuum dielectric constant.

[0075] The capacitance of the cable can be calculated from the capacitance values ​​of each layer using the following formula:

[0076]

[0077] Where: C sc1 For the capacitance of the inner semiconductor layer (105), C sc2 For the capacitance of the outer semiconductor layer (103), C ins The capacitor is an insulating layer (104).

[0078] The formula for calculating conductivity is:

[0079]

[0080] Where: d sc1 d is the thickness of the inner semiconductor layer (105). ins d is the thickness of the insulating layer (104). sc2 The thickness of the outer semiconductor layer (103) is σ. ins The conductivity of the insulating layer.

[0081] The theoretical propagation coefficient γ0 of a partial discharge signal propagating unidirectionally in a cable is:

[0082]

[0083] Furthermore, the insulation uniformity distribution coefficient P of the cable is calculated, and its calculation formula is as follows:

[0084]

[0085] The insulation uniformity coefficient P can be used to assess the insulation condition and operating status of a cable. When 0.9 ≤ P ≤ 1.2, the cable insulation condition is good and the operating status is stable; when P > 1.2 or P < 0.9, the cable insulation is severely aged and the operating status is unstable.

[0086] Example:

[0087] Taking the MYDP-3.6 / 6 1*16MT818.7-1999 cable as an example, the cable length is 10m, and the cable sheath thickness is d. b =2mm, outer semiconductor layer thickness d sc2 =0.6mm, insulation layer thickness d ins = 5.5mm, inner semiconductor layer thickness d sc1 =0.4mm and conductor layer radius r1=7.3mm, the experimental procedure includes the following steps:

[0088] A partial discharge signal with a charge of 100pc and a voltage amplitude of 64mV was generated using a partial discharge calibrator.

[0089] An oscilloscope is used to acquire the output signal at the end of the cable, and a computer and network analyzer perform a Fourier transform on the output signal.

[0090] By analyzing the ratio of the input signal to the output signal, the actual propagation coefficient of the signal in the cable is determined to be γ1 = 0.17 + j7;

[0091] By modeling the cable and determining its primary parameters R, L, C, and G, the theoretical propagation coefficient γ0 of the signal in the cable can be calculated as 0.16 + j6.8.

[0092] According to the formula, the insulation uniformity coefficient of the cable is P = 0.972, indicating that the cable has good insulation.

[0093] As can be seen from the above technical solutions, the present invention provides a mining cable detection device and method based on the propagation coefficient of partial discharge signals. By comparing the theoretical propagation coefficient and the actual propagation coefficient of partial discharge signals in the cable, the insulation uniformity distribution parameters of the cable are calculated, thereby assessing the insulation aging degree of the cable and helping to predict the operating condition of the cable. In the above embodiments, the present invention is only described illustratively; however, those skilled in the art can make various modifications to the present invention without departing from the spirit and scope of the invention after reading this patent application.

Claims

1. A method for detecting mining cables based on the propagation coefficient of partial discharge signals, comprising a single-core cable model (1), a signal generation system (2), and a measurement system (3); The single-core cable model (1), the signal generation system (2), and the measurement system (3) are connected in sequence; The single-core cable model includes, from the outside to the inside, a cable sheath (101), a shielding layer (102), an outer semiconductor layer (103), an insulation layer (104), an inner semiconductor layer (105), and a conductor layer (106). The two ends of the single-core cable model (1) are connected to coaxial cables respectively. The first end is connected to the partial discharge calibrator (201), and the last end is connected to the oscilloscope (301) in the measurement system (3). The signal generation system (2) consists of a partial discharge calibrator (201) that can generate partial discharge signals, connected to the head end of the single-core cable model (1); The measurement system (3) consists of an oscilloscope (301), a computer (302), and a network analyzer (303); The oscilloscope (301) is connected to both ends of the cable to collect the signal emitted by the partial discharge calibrator (201) and the partial discharge signal at the end of the cable, and is connected to the computer (302) and network analyzer (303), which are also part of the measurement system (3); The method specifically includes the following steps: a. Start the partial discharge calibrator (201) of the system, give a certain amount of partial discharge excitation at the beginning of the cable, and use an oscilloscope (301) to collect the output signal at the end of the cable; b. While acquiring the output signal, the output signal is analyzed and processed by the computer (302) and network analyzer (303) connected to the oscilloscope (301) to obtain its spectrum distribution; c. Calculate the actual propagation coefficient of the partial discharge signal in the cable. The calculation formula is: ； Where: L is the cable length For output signal, For input signals; Solve for the theoretical propagation coefficient of the partial discharge signal in the cable. The primary parameters R, L, C, and G of the single-core cable model (1) are determined as follows: The formula for solving the resistance R is: ； ； in: The permeability of free space, Let be the magnetic permeability of the conductor. Let r be the electrical conductivity of the conductor, r1 be the radius of the conductor layer (106), and r2 be the radius of the insulating layer (104). The signal frequency; The formula for calculating the inductance L is: ； When solving for capacitance C, it is necessary to solve for the inner semiconductor layer (105), the insulating layer (104), and the outer semiconductor layer (103) separately. The formula is as follows: ； in: Here are the dielectric constants of each dielectric layer. It is the vacuum permittivity; The capacitance of the cable can be calculated from the capacitance values ​​of each layer using the following formula: ； in: For the capacitance of the inner semiconductor layer (105), The capacitance of the outer semiconductor layer (103) The capacitor is an insulating layer (104); The formula for calculating conductivity is: ； in: The thickness of the inner semiconductor layer (105) is... The thickness of the insulating layer (104) is... The thickness of the outer semiconductor layer (103) is... The conductivity of the insulating layer; Theoretical propagation coefficient of partial discharge signal propagating unidirectionally in a cable for: ； The insulation uniformity distribution coefficient P of the cable is calculated using the following formula: ； The insulation condition and operating status of a cable can be evaluated based on the insulation uniformity distribution coefficient P: when At that time, the cable insulation was good and the operating condition was stable; when or At that time, the cable insulation was severely aged, and its operating condition was unstable.

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