Ultra-long distance transmission conductor state monitoring system and state monitoring method using same

Abstract

An ultra-long distance transmission conductor state monitoring system comprises a demodulator, an optical fiber type stress sensor, an optical fiber type wind speed sensor, an optical fiber type meteorological sensor and a sensing conductor. Wherein various sensors and sensing wires are connected with a demodulator through sensing optical fibers in the sensing wires, so that data acquisition, signal transmission and analysis, anti-interference guarantee and remote monitoring support are realized; the demodulator comprises a broadband light source, a first erbium-doped fiber amplifier, an acousto-optic modulator, a circulator, a low-noise random laser emission module, an ultra-weak reflection fiber grating, a long-distance transmission fiber and an EDF which are connected in sequence; the acousto-optic modulator is connected with the acousto-optic modulator driver; the circulator, the second erbium-doped fiber amplifier, the attenuator, the fiber bragg grating demodulation module and the upper computer are sequentially connected in series. According to the invention, the technical blank is filled, the signal transmission distance is long, the environmental adaptability is good, maintenance is avoided, and the comprehensive technical effect is excellent.

Description

Technical Field

[0001] The present invention relates to the technical field of power system monitoring equipment and detection application, and in particular to an ultra-long distance transmission line state monitoring system and a state monitoring method using the same. Background Art

[0002] The power system is one of the important infrastructures of the national economy, especially the high-voltage transmission lines can be called the lifeblood of the power system. Whether it can operate safely and stably directly determines the safety and efficiency of the power system and has a significant impact on the national economy.

[0003] Since power transmission lines are exposed to the wild for a long time, with the change of seasonal environment, natural disasters such as strong winds, heavy rains, ice cover, mountain fires, mudslides, lightning, floods, etc. have great harm to power transmission lines. It is necessary for people to carry out necessary monitoring of the power system in order to find problems in time and ensure the operation quality of the power system.

[0004] At present, the main means of safety monitoring of power transmission lines include video surveillance, personnel inspections, and installation of various power sensors. However, the power grid often operates in a harsh environment, subject to strong electromagnetic interference, long monitoring distance, high humidity, strong electrical corrosion, etc. The existing monitoring methods have the disadvantages of small information capacity, low efficiency, high cost, and sensors needing local power supply. Most of the existing monitoring devices for the status of transmission lines are electronic sensor equipment that is easily affected by electromagnetic interference and has high maintenance costs. It is difficult to transmit monitoring signals back, and confidentiality is difficult to ensure. The grating reflectivity of traditional fiber grating sensors commonly used in existing power systems is generally 90%. After multi-point multiplexing, the optical signal is prone to multiple reflections during the propagation process. There are problems such as small number of multiplexing, short monitoring distance, and large signal interference. It is difficult to meet the actual needs of long-distance monitoring of transmission lines in complex field environments.

[0005] People are eager to obtain an ultra-long distance transmission line condition monitoring system based on optical fiber random laser technology with excellent technical effects and a condition monitoring method using it. Summary of the invention

[0006] The present invention provides an ultra-long distance transmission line state monitoring system mainly based on optical fiber random laser technology and a state monitoring method using the same.

[0007] The technical solution of the present invention is:

[0008] A super-long distance transmission line condition monitoring system, the key technology of which is: it includes a demodulator, an optical fiber stress sensor, an optical fiber wind speed sensor, an optical fiber meteorological sensor and a sensing wire; wherein: the optical fiber stress sensor, the optical fiber wind speed sensor, the optical fiber meteorological sensor and the sensing wire are connected to the demodulator through the sensing optical fiber inside the sensing wire, so as to realize data collection, signal transmission and analysis, anti-interference guarantee and remote monitoring support;

[0009] The demodulator is installed in the substation, and its optical path diagram is as follows Figure 1 As shown, it includes a broadband light source 1, a first erbium-doped fiber amplifier 2, an acousto-optic modulator 4, a circulator 5, a low-noise random laser emission module 6, an ultra-weak reflection fiber Bragg grating 7, a long-distance transmission fiber 8, and an EDF 9 which are connected in sequence; the acousto-optic modulator 4 is also connected to the acousto-optic modulator driver 3; the following structures are also connected in series in sequence: the circulator 5, the second erbium-doped fiber amplifier 10, the attenuator 11, the fiber Bragg grating demodulation module 12, and the host computer 13;

[0010] The central wavelength of the broadband light source 1 is 1550 nm and is insensitive to temperature changes. The continuous light generated by the broadband light source 1 first passes through the first erbium-doped fiber amplifier 2 for a first amplification process.

[0011] The ultra-long distance transmission line condition monitoring system of the present invention preferably requires the following technical contents to be protected:

[0012] Low noise random laser emission module 6 Figure 2 As shown, the inside includes a wavelength division multiplexer 6-1, a low-noise random laser pump light source module 6-2 and a strong feedback module 6-3; wherein: the input end of the low-noise random laser emission module 6 is simultaneously connected to the wavelength division multiplexer 6-1, the low-noise random laser pump light source module 6-2 and the strong feedback module 6-3; the wavelength division multiplexer 6-1 is connected to the output end of the low-noise random laser emission module 6;

[0013] The continuous light generated by the broadband light source 1 is first amplified by the first erbium-doped fiber amplifier 2; the acousto-optic modulator driver 3 controls the acousto-optic modulator 4 to modulate the amplified continuous light of the first erbium-doped fiber amplifier 2 into a detection pulse light, which is connected to the port 1 of the circulator 5; the port 2 of the circulator 5 is connected to the input end of the low-noise random laser emission module 6; the detection light and the pump light generated by the low-noise random laser emission module 6 enter the monitoring circuit composed of the weak reflection grating sensor 7, the long-distance transmission optical fiber 8, and the EDF 9; the weak reflection grating sensor 7 reflects the detection light, and makes the reflected signal light carry external information; the reflected signal light enters the second erbium-doped fiber amplifier 10 through the port 3 of the circulator 5 for secondary amplification; the amplified signal light then enters the fiber grating demodulation module 12 through the attenuator 11; the data obtained by the demodulation module is then processed and analyzed by the host computer 13 and visualized;

[0014] The pump light is transmitted in the transmission optical fiber and generates random laser. The structure consists of a low-noise random laser emission module 6, a long-distance transmission optical fiber 8, and an EDF 9. Its working principle is: the detection pulse light with a wavelength of 1550nm enters the input end of the low-noise random laser emission module 6, that is, the 1550nm corresponding port of the wavelength division multiplexer 6-1, through the port 1 of the circulator 5, the low-noise random laser pump light source module 6-2 is connected to the 1365nm port of the wavelength division multiplexer 6-1, and the strong feedback module 6-3 is connected to the 1450nm port of the wavelength division multiplexer 6-1. The detection pulse light and the pump light come out from the output end of the low-noise random laser emission module 6, that is, the common end of the wavelength division multiplexer 6-1, and enter the weak reflection grating sensor 7, the long-distance transmission optical fiber 8, and the EDF 9; the Rayleigh scattering and Raman gain generated by the pump light in the long-distance transmission optical fiber 8 form a random laser; and the strong feedback module 6-3 provides a strong reflection to the random laser, reducing the pump light threshold for generating random lasers, forming a semi-open cavity random laser; the random laser is distributed along the long-distance transmission optical fiber 8, and the detection pulse light is amplified in a low-noise distributed manner; because at a farther end, random laser amplification cannot efficiently compensate for the loss of the optical fiber and the weak reflection grating sensor 7 to the detection pulse light, a 5-meter-long EDF9 is placed at 65km. Due to the distribution characteristics of the erbium ion energy band, the pump light at the position of EDF9 will produce a high-efficiency amplification of the pulse light, and the hybrid amplification method can successfully extend the sensing distance to 150km.

[0015] The weak reflection grating sensor 7 is the sensing element of the system. Due to its structural sensitivity, the central wavelength of its reflection spectrum changes with the change of the physical quantity of the external environment. The weak reflection grating sensor 7 reflects the signal light and makes the reflected signal light contain external information. The reflected signal light is then randomly laser amplified along the long-distance transmission optical fiber 8 and EDF9. Since the reflection spectrum of the strong feedback module 6-3 does not contain the wavelength of the signal light, the reflected signal light enters the fiber grating demodulation module 12 through the port 3 of the circulator 5, and the external physical quantity is restored by demodulating the reflected signal light spectrum information.

[0016] The ultra-long distance transmission line state monitoring system uses weak reflection gratings as sensing units and groups them according to reflectivity values, and also combines wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies in the system; gratings with the same reflectivity but different central wavelengths are grouped together, 7 groups of weak reflection gratings are used, each group has 44 gratings, wavelength division multiplexing WDM is used within each group, and time division multiplexing TDM is used between groups to solve the problem of crosstalk between main pulse sensing units of ordinary fiber grating sensing equipment after multi-point multiplexing, efficiently utilize the various bands of signal light sources, and improve the scale of system multiplexing.

[0017] The sensing wire has a built-in stainless steel tube optical unit, which is composited with multiple ultra-weak reflection fiber gratings for real-time sensing of the operating temperature and stress state of the sensing wire.

[0018] The optical fiber wind speed sensor and the optical fiber meteorological sensor are respectively installed on the first platform of the iron tower connected to the sensing wire, and are used to sense the environmental status of the sensing wire. The optical fiber micro-meteorological sensor is specifically used to monitor the temperature, humidity and rainfall status;

[0019] The optical fiber stress sensor is installed between the tower cross arm and the sensing wire to sense the operating tension of the sensing wire in real time;

[0020] The ultra-weak reflection fiber Bragg gratings in the sensing wires, fiber optic stress sensors, fiber optic wind speed sensors, and fiber optic meteorological sensors are fused in the lines through an electrically separated joint box, and are finally connected to the demodulator through a guide optical cable to achieve data collection, transmission, and analysis.

[0021] Ultra-long distance transmission line condition monitoring method using the aforementioned ultra-long distance transmission line condition monitoring device:

[0022] The continuous light generated by the broadband light source 1 is firstly amplified by the first erbium-doped fiber amplifier 2;

[0023] The acousto-optic modulator driver 3 controls the acousto-optic modulator 4 to modulate the amplified continuous light of the first erbium-doped fiber amplifier 2 into a detection pulse light, which is connected to the port 1 of the circulator 5. The port 2 of the circulator 5 is connected to the input end of the low-noise random laser emission module 6. The detection light and the pump light generated by the low-noise random laser emission module 6 enter the monitoring circuit composed of the weak reflection grating sensor 7, the long-distance transmission optical fiber 8, and the EDF 9. The weak reflection grating sensor 7 reflects the detection light and makes the reflected signal light carry external information. The reflected signal light enters the second erbium-doped fiber amplifier 10 through the port 3 of the circulator 5 for secondary amplification. The amplified signal light then enters the fiber Bragg grating demodulation module 12 through the attenuator 11. The data obtained by the demodulation module is then processed and analyzed by the host computer 13 and visualized.

[0024] The pump light is transmitted in the transmission optical fiber and generates random laser. The structure consists of a low-noise random laser emission module 6, a long-distance transmission optical fiber 8, and an EDF 9. Its working principle is: the detection pulse light with a wavelength of 1550nm enters the input end of the low-noise random laser emission module 6, that is, the 1550nm corresponding port of the wavelength division multiplexer 6-1, through the port 1 of the circulator 5, the low-noise random laser pump light source module 6-2 is connected to the 1365nm port of the wavelength division multiplexer 6-1, and the strong feedback module 6-3 is connected to the 1450nm port of the wavelength division multiplexer 6-1. The detection pulse light and the pump light come out from the output end of the low-noise random laser emission module 6, that is, the common end of the wavelength division multiplexer 6-1, and enter the weak reflection grating sensor 7, the long-distance transmission optical fiber 8, and the EDF 9; the Rayleigh scattering and Raman gain generated by the pump light in the long-distance transmission optical fiber 8 form a random laser; and the strong feedback module 6-3 provides a strong reflection to the random laser, reducing the pump light threshold for generating random lasers, forming a semi-open cavity random laser; the random laser is distributed along the long-distance transmission optical fiber 8, and the detection pulse light is amplified in a low-noise distributed manner; because at a farther end, random laser amplification cannot efficiently compensate for the loss of the optical fiber and the weak reflection grating sensor 7 to the detection pulse light, a 5-meter-long EDF9 is placed at 65km. Due to the distribution characteristics of the erbium ion energy band, the pump light at the position of EDF9 will produce a high-efficiency amplification of the pulse light, and the hybrid amplification method can successfully extend the sensing distance to 150km.

[0025] The weak reflection grating sensor 7 is the sensing element of the system. Due to its structural sensitivity, the central wavelength of its reflection spectrum changes with the change of the physical quantity of the external environment. The weak reflection grating sensor 7 reflects the signal light and makes the reflected signal light contain external information. The reflected signal light is then randomly laser amplified along the long-distance transmission optical fiber 8 and EDF9. Since the reflection spectrum of the strong feedback module 6-3 does not contain the wavelength of the signal light, the reflected signal light enters the fiber grating demodulation module 12 through the port 3 of the circulator 5, and the external physical quantity is restored by demodulating the reflected signal light spectrum information.

[0026] The ultra-long distance transmission line state monitoring system uses weak reflection gratings as sensing units and groups them according to reflectivity values, and also combines wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies in the system; gratings with the same reflectivity but different central wavelengths are grouped together, 7 groups of weak reflection gratings are used, and the number of gratings in each group can reach 44. Wavelength division multiplexing WDM is used within each group, and time division multiplexing TDM is used between groups to solve the problem of crosstalk between main pulse sensing units of ordinary fiber grating sensing equipment after multi-point multiplexing, efficiently utilize the various bands of signal light sources, and improve the scale of system multiplexing.

[0027] Typical preferred embodiment: The method for monitoring the state of ultra-long distance transmission wires meets the following requirements when monitoring the ice thickness of ultra-long distance transmission wires:

[0028] The ultra-long distance transmission line is an overhead line LGJ-400 / 35, and its typical characteristics are: the number of splits is single split, and the conductor cross-sectional area is A=425.24mm 2 , diameter d = 26.8 mm; conductor weight: W = 1.349 kg / m; conductor elastic coefficient: E = 65.9 × 10 3 kgf / mm 2 , wire linear expansion coefficient: α = 20.3 × 10 -6 1 / deg.C;

[0029] Line information: Transmission line representative span: L = 400m,

[0030] System acquisition parameters: The conductor operation acquisition temperature is -3℃, the operating tension is T2=35559N when the operating temperature is -3℃, and the wind speed is V2=10m / s. When the installation temperature is 10℃, the working tension is T1=24018N, the conductor operation acquisition temperature is t1=10℃, and the wind speed is V1=15m / s.

[0031] The algorithm process meets the following requirements:

[0032] First calculate the initial installation operating stress f1:

[0033]

[0034] Substituting f1 into formula (2) yields the constant variable Q:

[0035]

[0036] Where: q1 is the load factor under initial conditions;

[0037] Wire gravity load δ = W * 9.80665 / A = 1.349 * 9.80665 / 425.24 = 0.0311 N / m.mm 2 ;

[0038] Spacing L = 400m;

[0039] Further obtain the intermediate variable M:

[0040] M=f2 2 ×[f2-(Q-α·t·E)] (3)

[0041] Where f2 represents the working stress of ice collection, α represents the expansion coefficient of the wire; the difference between the temperature during ice accumulation and the initial installation temperature t = (t2-t1); E represents the elastic modulus of the wire;

[0042] According to the relationship between load factor, comprehensive load and weight, formula (4) is obtained:

[0043]

[0044] Where: q1 is the load factor under installation conditions;

[0045] g1 is the self-weight load, N / m; g1 = W × 9.80665 = 1.349 * 9.80665 = 13.229 N / m, (5)

[0046] Ice gravity load g 2＝ 9.80665×0.9π×k×(k+d)×10 -3 N / m(6)

[0047] Self-weight plus ice gravity load: g3 = g1 + g2 N / m (7)

[0048] Wind load g5 = 0.625v2 × (d + 2K) × α × μ × 10 -3 N / m; (8)

[0049] Comprehensive load g7:

[0050] The value of the conductor wind pressure unevenness coefficient α meets the following requirements: α=1 when 10≤v<20m / s, α=0.85 when 20≤v<30m / s, α=0.75 when 30≤v<35m / s, α=0.70 when v≥35m / s;

[0051] The conductor body coefficient μ meets the following requirements: μ = 1.2 when the conductor outer diameter d < 17 mm, μ = 1.1 when the conductor outer diameter d ≥ 17 mm, and μ is uniformly set to 1.2 when covered with ice;

[0052] π=3.1415926, load factor q1 under installation condition:

[0053] q1=g7 / g1 (10)

[0054] Substitute the above f1, q1, δ, L, and E into formula (2) to obtain Q;

[0055] Then substitute Q, f2, α, t, and E into formula (3) to obtain the variable M;

[0056] And because M=(q 2 ·δ)·L 2 ·E / 24 (11)

[0057] Given the load coefficient q2 at temperature t2, weight specific load δ = W × 9.80665 / AN / mm 2 , span L, conductor elastic modulus E; Formula (12) is derived from Formula (11):

[0058] The formula is derived based on the relationship between the load factor, comprehensive load and weight:

[0059] So g7=q2×g1 (13)

[0060] By combining formula (5), (7), (8), (9), (12) and (11), we can get formula (14):

[0061]

[0062] Assumptions:

[0063] A=(π×0.9×10 -3 ) 2

[0064] B = 2 × (π × 0.9 × 10 -3 ) 2 ×d

[0065] C = 2(π×0.9×10 -3 )·W+(π×0.9×10 -3 )2 ·d 2 +4×(0.063732·v 2 ×μ×α×10 -3 ) 2

[0066] D=2(π×0.9×10 -3 )·W·d+4·(0.063732·v 2 ×μ×α×10 -3 ) 2 ·d

[0067]

[0068] So we get: A×K 4 +B×K 3 +C×K 2 +D×K+E=0 (15)

[0069] Calculate the K value according to formula (17);

[0070] A=0.000008, B=0.000428499, C=0.013604256, D=0.210711599, E=-2.8085;

[0071] Substitute the constant term and find K = 8 mm.

[0072] Furthermore, the acousto-optic modulator driver 3 and the acousto-optic modulator 4 in the system components can be replaced by an electro-optic modulator to directly modulate a pulse signal, thereby improving the response time of the system.

[0073] The broadband light source 1, the first erbium-doped fiber amplifier 2, the acousto-optic modulator driver 3, and the acousto-optic modulator 4 in the system components can be replaced by a pulse light source, which can reduce the cost and size.

[0074] The beneficial effects of the present invention are:

[0075] The present invention adopts a method based on optical fiber random laser technology and ultra-weak reflection optical fiber grating technology to realize transmission line status monitoring, which well solves the problems of high maintenance cost, large signal interference and short monitoring distance of monitoring sensors in current transmission lines.

[0076] The present invention adopts passive ultra-weak fiber Bragg grating sensing and fiber random laser technology to realize real-time monitoring of the running status of the conductor. It has the characteristics of long monitoring link, passive operation, reliable system and maintenance-free, etc. It can completely solve the technical problems existing in the prior art and is very suitable for this application; it fills the technical gap in the field of industrial conductor monitoring.

[0077] In addition, fiber Bragg gratings have been increasingly used in monitoring strain, temperature, displacement, etc. in civil structures and industrial production fields. The development and application of the relevant technologies of the present invention are of great significance to the improvement of fiber optic monitoring systems, making fiber optic monitoring a more integrated solution.

[0078] Compared with the existing video monitoring and power sensor solutions, the present invention has the following beneficial effects:

[0079] (1) No power supply is required at the monitoring site, solving the problem of power supply difficulty for field monitoring devices;

[0080] (2) The device uses optical fiber sensing technology, which has a long signal transmission distance and can achieve 150km range monitoring without relay;

[0081] (3) There are no electronic components at the monitoring site, and it has good adaptability to harsh environments such as high temperature, low temperature and humidity, and there is no hidden danger of lightning strike;

[0082] (4) It can be integrated with other fiber optic monitoring systems and is maintenance-free after the project is implemented. BRIEF DESCRIPTION OF THE DRAWINGS

[0083] Figure 1 This is a block diagram of the composition principle of the present invention;

[0084] Figure 2 This is a schematic diagram showing the construction principle of the low-noise random laser emission module 6. DETAILED DESCRIPTION

[0085] The present invention will be further described below in conjunction with the embodiments and the accompanying drawings, but is not limited thereto.

[0086] Example 1

[0087] A super-long distance transmission line condition monitoring system, the key technology of which is: it includes a demodulator, an optical fiber stress sensor, an optical fiber wind speed sensor, an optical fiber meteorological sensor and a sensing wire; wherein: the optical fiber stress sensor, the optical fiber wind speed sensor, the optical fiber meteorological sensor and the sensing wire are connected to the demodulator through the sensing optical fiber inside the sensing wire, so as to realize data collection, signal transmission and analysis, anti-interference guarantee and remote monitoring support;

[0088] The demodulator is installed in the substation, and its optical path diagram is as follows Figure 1 As shown, it includes a broadband light source 1, a first erbium-doped fiber amplifier 2, an acousto-optic modulator 4, a circulator 5, a low-noise random laser emission module 6, an ultra-weak reflection fiber Bragg grating 7, a long-distance transmission fiber 8, and an EDF 9 which are connected in sequence; the acousto-optic modulator 4 is also connected to the acousto-optic modulator driver 3; the following structures are also connected in series in sequence: the circulator 5, the second erbium-doped fiber amplifier 10, the attenuator 11, the fiber Bragg grating demodulation module 12, and the host computer 13;

[0089] The central wavelength of the broadband light source 1 is 1550 nm and is insensitive to temperature changes. The continuous light generated by the broadband light source 1 first passes through the first erbium-doped fiber amplifier 2 for a first amplification process.

[0090] In the ultra-long distance transmission line state monitoring system, the low noise random laser emission module 6 is as follows Figure 2 As shown, the inside includes a wavelength division multiplexer 6-1, a low-noise random laser pump light source module 6-2 and a strong feedback module 6-3; wherein: the input end of the low-noise random laser emission module 6 is simultaneously connected to the wavelength division multiplexer 6-1, the low-noise random laser pump light source module 6-2 and the strong feedback module 6-3; the wavelength division multiplexer 6-1 is connected to the output end of the low-noise random laser emission module 6;

[0091] The continuous light generated by the broadband light source 1 is first amplified by the first erbium-doped fiber amplifier 2; the acousto-optic modulator driver 3 controls the acousto-optic modulator 4 to modulate the amplified continuous light of the first erbium-doped fiber amplifier 2 into a detection pulse light, which is connected to the port 1 of the circulator 5; the port 2 of the circulator 5 is connected to the input end of the low-noise random laser emission module 6; the detection light and the pump light generated by the low-noise random laser emission module 6 enter the monitoring circuit composed of the weak reflection grating sensor 7, the long-distance transmission optical fiber 8, and the EDF 9; the weak reflection grating sensor 7 reflects the detection light, and makes the reflected signal light carry external information; the reflected signal light enters the second erbium-doped fiber amplifier 10 through the port 3 of the circulator 5 for secondary amplification; the amplified signal light then enters the fiber grating demodulation module 12 through the attenuator 11; the data obtained by the demodulation module is then processed and analyzed by the host computer 13 and visualized;

[0092] The pump light is transmitted in the transmission optical fiber and generates random laser. The structure consists of a low-noise random laser emission module 6, a long-distance transmission optical fiber 8, and an EDF 9. Its working principle is: the detection pulse light with a wavelength of 1550nm enters the input end of the low-noise random laser emission module 6, that is, the 1550nm corresponding port of the wavelength division multiplexer 6-1, through the port 1 of the circulator 5, the low-noise random laser pump light source module 6-2 is connected to the 1365nm port of the wavelength division multiplexer 6-1, and the strong feedback module 6-3 is connected to the 1450nm port of the wavelength division multiplexer 6-1. The detection pulse light and the pump light come out from the output end of the low-noise random laser emission module 6, that is, the common end of the wavelength division multiplexer 6-1, and enter the weak reflection grating sensor 7, the long-distance transmission optical fiber 8, and the EDF 9; the Rayleigh scattering and Raman gain generated by the pump light in the long-distance transmission optical fiber 8 form a random laser; and the strong feedback module 6-3 provides a strong reflection to the random laser, reducing the pump light threshold for generating random lasers, forming a semi-open cavity random laser; the random laser is distributed along the long-distance transmission optical fiber 8, and the detection pulse light is amplified in a low-noise distributed manner; because at a farther end, random laser amplification cannot efficiently compensate for the loss of the optical fiber and the weak reflection grating sensor 7 to the detection pulse light, a 5-meter-long EDF9 is placed at 65km. Due to the distribution characteristics of the erbium ion energy band, the pump light at the position of EDF9 will produce a high-efficiency amplification of the pulse light, and the hybrid amplification method can successfully extend the sensing distance to 150km.

[0093] The weak reflection grating sensor 7 is the sensing element of the system. Due to its structural sensitivity, the central wavelength of its reflection spectrum changes with the change of the physical quantity of the external environment. The weak reflection grating sensor 7 reflects the signal light and makes the reflected signal light contain external information. The reflected signal light is then randomly laser amplified along the long-distance transmission optical fiber 8 and EDF9. Since the reflection spectrum of the strong feedback module 6-3 does not contain the wavelength of the signal light, the reflected signal light enters the fiber grating demodulation module 12 through the port 3 of the circulator 5, and the external physical quantity is restored by demodulating the reflected signal light spectrum information.

[0094] The ultra-long distance transmission line state monitoring system uses weak reflection gratings as sensing units and groups them according to reflectivity values, and also combines wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies in the system; gratings with the same reflectivity but different central wavelengths are grouped together, 7 groups of weak reflection gratings are used, each group has 44 gratings, wavelength division multiplexing WDM is used within each group, and time division multiplexing TDM is used between groups to solve the problem of crosstalk between main pulse sensing units of ordinary fiber grating sensing equipment after multi-point multiplexing, efficiently utilize the various bands of signal light sources, and improve the scale of system multiplexing.

[0095] The sensing wire has a built-in stainless steel tube optical unit, which is composited with multiple ultra-weak reflection fiber gratings for real-time sensing of the operating temperature and stress state of the sensing wire.

[0096] The optical fiber wind speed sensor and the optical fiber meteorological sensor are respectively installed on the first platform of the iron tower connected to the sensing wire, and are used to sense the environmental status of the sensing wire. The optical fiber micro-meteorological sensor is specifically used to monitor the temperature, humidity and rainfall status;

[0097] The optical fiber stress sensor is installed between the tower cross arm and the sensing wire to sense the operating tension of the sensing wire in real time;

[0098] The ultra-weak reflection fiber Bragg gratings in the sensing wires, fiber optic stress sensors, fiber optic wind speed sensors, and fiber optic meteorological sensors are fused in the lines through an electrically separated joint box, and are finally connected to the demodulator through a guide optical cable to achieve data collection, transmission, and analysis.

[0099] Example 2

[0100] A method for monitoring the state of an ultra-long distance transmission line using the ultra-long distance transmission line state monitoring device described in Example 1:

[0101] The continuous light generated by the broadband light source 1 is firstly amplified by the first erbium-doped fiber amplifier 2;

[0102] The acousto-optic modulator driver 3 controls the acousto-optic modulator 4 to modulate the amplified continuous light of the first erbium-doped fiber amplifier 2 into a detection pulse light, which is connected to the port 1 of the circulator 5. The port 2 of the circulator 5 is connected to the input end of the low-noise random laser emission module 6. The detection light and the pump light generated by the low-noise random laser emission module 6 enter the monitoring circuit composed of the weak reflection grating sensor 7, the long-distance transmission optical fiber 8, and the EDF 9. The weak reflection grating sensor 7 reflects the detection light and makes the reflected signal light carry external information. The reflected signal light enters the second erbium-doped fiber amplifier 10 through the port 3 of the circulator 5 for secondary amplification. The amplified signal light then enters the fiber Bragg grating demodulation module 12 through the attenuator 11. The data obtained by the demodulation module is then processed and analyzed by the host computer 13 and visualized.

[0103] The pump light is transmitted in the transmission optical fiber and generates random laser. The structure consists of a low-noise random laser emission module 6, a long-distance transmission optical fiber 8, and an EDF 9. Its working principle is: the detection pulse light with a wavelength of 1550nm enters the input end of the low-noise random laser emission module 6, that is, the 1550nm corresponding port of the wavelength division multiplexer 6-1, through the port 1 of the circulator 5, the low-noise random laser pump light source module 6-2 is connected to the 1365nm port of the wavelength division multiplexer 6-1, and the strong feedback module 6-3 is connected to the 1450nm port of the wavelength division multiplexer 6-1. The detection pulse light and the pump light come out from the output end of the low-noise random laser emission module 6, that is, the common end of the wavelength division multiplexer 6-1, and enter the weak reflection grating sensor 7, the long-distance transmission optical fiber 8, and the EDF 9; the Rayleigh scattering and Raman gain generated by the pump light in the long-distance transmission optical fiber 8 form a random laser; and the strong feedback module 6-3 provides a strong reflection to the random laser, reducing the pump light threshold for generating random lasers, forming a semi-open cavity random laser; the random laser is distributed along the long-distance transmission optical fiber 8, and the detection pulse light is amplified in a low-noise distributed manner; because at a farther end, random laser amplification cannot efficiently compensate for the loss of the optical fiber and the weak reflection grating sensor 7 to the detection pulse light, a 5-meter-long EDF9 is placed at 65km. Due to the distribution characteristics of the erbium ion energy band, the pump light at the position of EDF9 will produce a high-efficiency amplification of the pulse light, and the hybrid amplification method can successfully extend the sensing distance to 150km.

[0104] The weak reflection grating sensor 7 is the sensing element of the system. Due to its structural sensitivity, the central wavelength of its reflection spectrum changes with the change of the physical quantity of the external environment. The weak reflection grating sensor 7 reflects the signal light and makes the reflected signal light contain external information. The reflected signal light is then randomly laser amplified along the long-distance transmission optical fiber 8 and EDF9. Since the reflection spectrum of the strong feedback module 6-3 does not contain the wavelength of the signal light, the reflected signal light enters the fiber grating demodulation module 12 through the port 3 of the circulator 5, and the external physical quantity is restored by demodulating the reflected signal light spectrum information.

[0105] The ultra-long distance transmission line state monitoring system uses weak reflection gratings as sensing units and groups them according to reflectivity values, and also combines wavelength division multiplexing (WDM) and time division multiplexing (TDM) technologies in the system; gratings with the same reflectivity but different central wavelengths are grouped together, 7 groups of weak reflection gratings are used, and the number of gratings in each group can reach 44. Wavelength division multiplexing WDM is used within each group, and time division multiplexing TDM is used between groups to solve the problem of crosstalk between main pulse sensing units of ordinary fiber grating sensing equipment after multi-point multiplexing, efficiently utilize the various bands of signal light sources, and improve the scale of system multiplexing.

[0106] Furthermore, the acousto-optic modulator driver 3 and the acousto-optic modulator 4 in the system components can be replaced by an electro-optic modulator to directly modulate a pulse signal, thereby improving the response time of the system.

[0107] The broadband light source 1, the first erbium-doped fiber amplifier 2, the acousto-optic modulator driver 3, and the acousto-optic modulator 4 in the system components can be replaced by a pulse light source, which can reduce the cost and size.

[0108] The beneficial effects of this embodiment are:

[0109] This embodiment uses a method based on optical fiber random laser technology and ultra-weak reflection optical fiber Bragg grating technology to realize transmission line status monitoring, which effectively solves the problems of high maintenance cost, large signal interference and short monitoring distance of monitoring sensors in current transmission lines.

[0110] This embodiment adopts passive ultra-weak fiber Bragg grating sensing and fiber random laser technology to realize real-time monitoring of the conductor operation status, and has the characteristics of long monitoring link, passive operation, reliable system and maintenance-free, etc. It can completely solve the technical difficulties existing in the prior art and is very suitable for this application scenario; it fills the technical gap in the field of industrial conductor monitoring.

[0111] In addition, fiber Bragg gratings have been increasingly used in monitoring strain, temperature, displacement, etc. in civil structures and industrial production fields. The development and application of the relevant technology of this embodiment is of great significance to the improvement of the fiber optic monitoring system, making fiber optic monitoring a more integrated solution.

[0112] Compared with the existing video monitoring and power sensor solutions, this embodiment has the following beneficial effects:

[0113] (4) No power supply is required at the monitoring site, solving the problem of power supply difficulties for field monitoring devices;

[0114] (5) The device uses optical fiber sensing technology, which has a long signal transmission distance and can achieve 150km range monitoring without relay;

[0115] (6) There are no electronic components at the monitoring site, and it has good adaptability to harsh environments such as high temperature, low temperature and humidity, and there is no hidden danger of lightning strike;

[0116] (4) It can be integrated with other fiber optic monitoring systems and is maintenance-free after the project is implemented.

[0117] Example 3

[0118] The method for monitoring the state of ultra-long distance transmission wires meets the requirements when monitoring the ice thickness of ultra-long distance transmission wires:

[0119] The ultra-long distance transmission line is an overhead line LGJ-400 / 35, and its typical characteristics are: the number of splits is single split, and the conductor cross-sectional area is A=425.24mm 2 , diameter d = 26.8 mm; conductor weight: W = 1.349 kg / m; conductor elastic coefficient: E = 65.9 × 10 3 kgf / mm 2 , wire linear expansion coefficient: α = 20.3 × 10 -6 1 / deg.C;

[0120] Line information: Transmission line representative span: L = 400m,

[0121] System acquisition parameters: The conductor operation acquisition temperature is -3℃, the operating tension is T2=35559N when the operating temperature is -3℃, and the wind speed is V2=10m / s. When the installation temperature is 10℃, the working tension is T1=24018N, the conductor operation acquisition temperature is t1=10℃, and the wind speed is V1=15m / s.

[0122] The algorithm process meets the following requirements:

[0123] First calculate the initial installation operating stress f1:

[0124]

[0125] Substituting f1 into formula (2) yields the constant variable Q:

[0126]

[0127] Where: q1 is the load factor under initial conditions;

[0128] Wire gravity load δ = W * 9.80665 / A = 1.349 * 9.80665 / 425.24 = 0.0311 N / m.mm 2 ;

[0129] Spacing L = 400m;

[0130] Further obtain the intermediate variable M:

[0131] M=f2 2 ×[f2-(Q-α·t·E)] (3)

[0132] Where f2 represents the working stress of ice collection, α represents the expansion coefficient of the wire; the difference between the temperature during ice accumulation and the initial installation temperature t = (t2-t1); E represents the elastic modulus of the wire;

[0133] According to the relationship between load factor, comprehensive load and weight, formula (4) is obtained:

[0134]

[0135] Where: q1 is the load factor under installation conditions;

[0136] g1 is the self-weight load, N / m; g1 = W × 9.80665 = 1.349 * 9.80665 = 13.229 N / m, (5)

[0137] Ice gravity load g 2＝ 9.80665×0.9π×k×(k+d)×10 -3 N / m (6)

[0138] Self-weight plus ice gravity load: g3 = g1 + g2 N / m (7)

[0139] Wind load g5 = 0.625v2 × (d + 2K) × α × μ × 10 -3 N / m; (8)

[0140] Comprehensive load g7:

[0141] The value of the conductor wind pressure unevenness coefficient α meets the following requirements: α=1 when 10≤v<20m / s, α=0.85 when 20≤v<30m / s, α=0.75 when 30≤v<35m / s, α=0.70 when v≥35m / s;

[0142] The conductor body coefficient μ meets the following requirements: μ = 1.2 when the conductor outer diameter d < 17 mm, μ = 1.1 when the conductor outer diameter d ≥ 17 mm, and μ is uniformly set to 1.2 when covered with ice;

[0143] π=3.1415926, load factor q1 under installation condition:

[0144] q 1＝ g7 / g1 (10)

[0145] Substitute the above f1, q1, δ, L, and E into formula (2) to obtain Q;

[0146] Then substitute Q, f2, α, t, and E into formula (3) to obtain the variable M;

[0147] And because M=(q 2 ·δ)·L 2 ·E / 24(11)

[0148] Given the load coefficient q2 at temperature t2, weight specific load δ = W × 9.80665 / AN / mm 2 , span L, conductor elastic modulus E; Formula (12) is derived from Formula (11):

[0149] The formula is derived based on the relationship between the load factor, comprehensive load and weight:

[0150] So g7=q2×g1 (13)

[0151] By combining formula (5), (7), (8), (9), (12) and (11), we can get formula (14):

[0152]

[0153] Assumptions:

[0154] A=(π×0.9×10 -3 ) 2

[0155] B = 2 × (π × 0.9 × 10 -3 ) 2 ×d

[0156] C = 2(π×0.9×10 -3 )·W+(π×0.9×10 -3 ) 2 ·d 2 +4×(0.063732·v 2 ×μ×α×10 -3 ) 2

[0157] D=2(π×0.9×10 -3 )·W·d+4·(0.063732·v 2 ×μ×α×10 -3 ) 2 ·d

[0158]

[0159] So we get: A×K 4 +B×K 3 +C×K 2 +D×K+E=0 (15)

[0160] Calculate the K value according to formula (17);

[0161] A=0.000008, B=0.000428499, C=0.013604256, D=0.210711599, E=-2.8085;

[0162] Substitute the constant term and find K = 8 mm.

Claims

1. Ultra-long distance transmission line condition monitoring system, characterized by: It includes a demodulator, a fiber optic stress sensor, a fiber optic wind speed sensor, a fiber optic meteorological sensor and a sensing wire; wherein: the fiber optic stress sensor, the fiber optic wind speed sensor, the fiber optic meteorological sensor and the sensing wire are connected to the demodulator through the sensing optical fiber inside the sensing wire to realize data collection, signal transmission and analysis, anti-interference guarantee and remote monitoring support; The demodulator comprises a broadband light source (1), a first erbium-doped fiber amplifier (2), an acousto-optic modulator (4), a circulator (5), a low-noise random laser emission module (6), an ultra-weak reflection fiber grating (7), a long-distance transmission fiber (8), and an EDF (9) which are connected in sequence; the acousto-optic modulator (4) is also connected to an acousto-optic modulator driver (3); the following structures are also connected in series in sequence: the circulator (5), a second erbium-doped fiber amplifier (10), an attenuator (11), a fiber grating demodulation module (12), and a host computer (13); The central wavelength of the broadband light source (1) is 1550 nm and is insensitive to temperature changes. The continuous light generated by the broadband light source (1) is firstly amplified by the first erbium-doped optical fiber amplifier (2).

2. The ultra-long distance transmission line condition monitoring system according to claim 1, characterized in that: The low-noise random laser emission module (6) internally includes a wavelength division multiplexer (6-1), a low-noise random laser pump light source module (6-2) and a strong feedback module (6-3); wherein: the input end of the low-noise random laser emission module (6) is simultaneously connected to the wavelength division multiplexer (6-1), the low-noise random laser pump light source module (6-2) and the strong feedback module (6-3); the wavelength division multiplexer (6-1) is connected to the output end of the low-noise random laser emission module (6); The continuous light generated by the broadband light source (1) is first amplified by the first erbium-doped fiber amplifier (2); the acousto-optic modulator driver (3) controls the acousto-optic modulator (4) to modulate the amplified continuous light of the first erbium-doped fiber amplifier (2) into a detection pulse light, which is connected to the port 1 of the circulator (5); the port 2 of the circulator (5) is connected to the input end of the low-noise random laser emission module (6); the detection light and the pump light generated by the low-noise random laser emission module (6) enter a monitoring circuit composed of a weak reflection grating sensor (7), a long-distance transmission optical fiber (8), and an EDF (9); the weak reflection grating sensor (7) reflects the detection light and makes the reflected signal light carry external information; the reflected signal light enters the second erbium-doped fiber amplifier (10) through the port 3 of the circulator (5) for secondary amplification; the amplified signal light then enters the fiber grating demodulation module (12) through the attenuator (11); the data obtained by the demodulation module is then processed and analyzed by the host computer (13) and visualized; The pump light is transmitted in the transmission optical fiber and generates random laser. The structure consists of a low-noise random laser emission module (6), a long-distance transmission optical fiber (8), and an EDF (9). The working principle is as follows: the detection pulse light enters the input end of the low-noise random laser emission module (6), i.e., the corresponding port of the wavelength division multiplexer (6-1), through the port 1 of the circulator (5); the low-noise random laser pump light source module (6-2) is connected to the port of the wavelength division multiplexer (6-1); the strong feedback module (6-3) is connected to the port of the wavelength division multiplexer (6-1); the detection pulse light and the pump light are transmitted from the low-noise random laser emission module (6) together. The output end of the random laser emission module (6), i.e., the common end of the wavelength division multiplexer (6-1), enters a monitoring circuit composed of a weak reflection grating sensor (7), a long-distance transmission optical fiber (8), and an EDF (9); the Rayleigh scattering and Raman gain generated by the pump light in the long-distance transmission optical fiber (8) form a random laser; and the strong feedback module (6-3) provides a strong reflection to the random laser, thereby reducing the pump light threshold for generating the random laser and forming a semi-open cavity random laser; the random laser is distributed along the long-distance transmission optical fiber (8) and performs low-noise distributed amplification on the detection pulse light; The weak reflection grating sensor (7) is a sensing element of the system. The weak reflection grating sensor (7) reflects the signal light and makes the reflected signal light contain external information. The reflected signal light is then randomly laser amplified along the long-distance transmission optical fiber (8) and the EDF (9). Since the reflection spectrum of the strong feedback module (6-3) does not contain the wavelength of the signal light, the reflected signal light enters the fiber grating demodulation module (12) through the port 3 of the circulator (5), and the external physical quantity is restored by demodulating the spectrum information of the reflected signal light.

3. The ultra-long distance transmission line condition monitoring system according to claim 1 or 2, characterized in that: The ultra-long distance transmission line status monitoring system uses weak reflection gratings as sensing units and groups them according to reflectivity values, and also combines wavelength division multiplexing with time division multiplexing technology in the system; gratings with the same reflectivity but different central wavelengths are grouped together, 7 groups of weak reflection gratings are used, and the number of gratings in each group is 44. Wavelength division multiplexing is used within each group, and time division multiplexing is used between groups to solve the problem of crosstalk between main pulse sensing units of ordinary fiber grating sensing equipment after multi-point multiplexing, efficiently utilize the various bands of signal light sources, and improve the scale of system multiplexing.

4. The ultra-long distance transmission line condition monitoring system according to claim 3, characterized in that: The sensing wire has a built-in stainless steel tube optical unit, which is composited with multiple ultra-weak reflection fiber gratings for real-time sensing of the operating temperature and stress state of the sensing wire. The optical fiber wind speed sensor and the optical fiber meteorological sensor are respectively installed on the first platform of the iron tower connected to the sensing wire, and are used to sense the environmental status of the sensing wire. The optical fiber micro-meteorological sensor is specifically used to monitor the temperature, humidity and rainfall status; The optical fiber stress sensor is installed between the tower cross arm and the sensing wire to sense the operating tension of the sensing wire in real time; The ultra-weak reflection fiber Bragg gratings in the sensing wires, fiber optic stress sensors, fiber optic wind speed sensors, and fiber optic meteorological sensors are fused in the lines through an electrically separated joint box, and are finally connected to the demodulator through a guide optical cable to achieve data collection, transmission, and analysis.

5. A method for monitoring the state of an ultra-long distance transmission line using the ultra-long distance transmission line state monitoring system according to claim 1, characterized in that: The low-noise random laser emission module (6) internally includes a wavelength division multiplexer (6-1), a low-noise random laser pump light source module (6-2) and a strong feedback module (6-3); wherein: the input end of the low-noise random laser emission module (6) is simultaneously connected to the wavelength division multiplexer (6-1), the low-noise random laser pump light source module (6-2) and the strong feedback module (6-3); the wavelength division multiplexer (6-1) is connected to the output end of the low-noise random laser emission module (6); The ultra-long distance transmission line condition monitoring method using the ultra-long distance transmission line condition monitoring system is: The continuous light generated by the broadband light source (1) is firstly amplified by the first erbium-doped optical fiber amplifier (2); The acousto-optic modulator driver (3) controls the acousto-optic modulator (4) to modulate the amplified continuous light of the first erbium-doped fiber amplifier (2) into a detection pulse light, which is connected to the port 1 of the circulator (5). The port 2 of the circulator (5) is connected to the input end of the low-noise random laser emission module (6). The detection light and the pump light generated by the low-noise random laser emission module (6) enter the monitoring circuit composed of the weak reflection grating sensor (7), the long-distance transmission optical fiber (8), and the EDF (9). The weak reflection grating sensor (7) reflects the detection light and makes the reflected signal light carry external information. The reflected signal light enters the second erbium-doped fiber amplifier (10) through the port 3 of the circulator (5) for secondary amplification. The amplified signal light then enters the fiber Bragg grating demodulation module (12) through the attenuator (11). The data obtained by the demodulation module is then processed and analyzed by the host computer (13) and visualized. The pump light is transmitted in the transmission optical fiber and generates random laser. The structure consists of a low-noise random laser emission module (6), a long-distance transmission optical fiber (8), and an EDF (9). The working principle is as follows: the detection pulse light enters the input end of the low-noise random laser emission module (6), i.e., the corresponding port of the wavelength division multiplexer (6-1), through the port 1 of the circulator (5); the low-noise random laser pump light source module (6-2) is connected to the port of the wavelength division multiplexer (6-1); the strong feedback module (6-3) is connected to the port of the wavelength division multiplexer (6-1); the detection pulse light and the pump light are transmitted from the low-noise random laser emission module (6) together. The output end of the random laser emission module (6), i.e., the common end of the wavelength division multiplexer (6-1), enters a monitoring circuit composed of a weak reflection grating sensor (7), a long-distance transmission optical fiber (8), and an EDF (9); the Rayleigh scattering and Raman gain generated by the pump light in the long-distance transmission optical fiber (8) form a random laser; and the strong feedback module (6-3) provides a strong reflection to the random laser, thereby reducing the pump light threshold for generating the random laser and forming a semi-open cavity random laser; the random laser is distributed along the long-distance transmission optical fiber (8) and performs low-noise distributed amplification on the detection pulse light; The weak reflection grating sensor (7) is a sensing element of the system. The weak reflection grating sensor (7) reflects the signal light and makes the reflected signal light contain external information. The reflected signal light is then randomly laser amplified along the long-distance transmission optical fiber (8) and the EDF (9). Since the reflection spectrum of the strong feedback module (6-3) does not contain the wavelength of the signal light, the reflected signal light enters the fiber grating demodulation module (12) through the port 3 of the circulator (5), and the external physical quantity is restored by demodulating the spectrum information of the reflected signal light.

6. The method for monitoring the state of an ultra-long distance transmission line according to claim 5, characterized in that: The ultra-long distance transmission line status monitoring system uses weak reflection gratings as sensing units and groups them according to reflectivity values, and also combines wavelength division multiplexing and time division multiplexing technologies in the system; gratings with the same reflectivity but different central wavelengths are grouped together, 7 groups of weak reflection gratings are used, and the number of gratings in each group can reach 44. Wavelength division multiplexing is used within each group, and time division multiplexing is used between groups to solve the problem of crosstalk between main pulse sensing units of ordinary fiber grating sensing equipment after multi-point multiplexing, efficiently utilize the various bands of signal light sources, and improve the scale of system multiplexing.

7. The method for monitoring the state of an ultra-long distance power transmission line according to claim 5, characterized in that: The ultra-long distance transmission line condition monitoring method meets the following requirements when monitoring the ice thickness of the ultra-long distance transmission line: The ultra-long distance transmission line is an overhead line LGJ-400 / 35, and its typical features are: The split number feature is single split, and the conductor cross-sectional area A = 425.24mm 2 , diameter d = 26.8 mm; wire weight W = 1.349 kg / m; wire elastic coefficient E = 65.9 × 10 3 kgf / mm 2 , the linear expansion coefficient of the conductor is α = 20.3 × 10 -6 1 / deg.C; Line information: Transmission line representative span: L = 400m, System acquisition parameters: The conductor operation acquisition temperature is -3℃, the operating tension is T2=35559N when the operating temperature is -3℃, and the wind speed is V2=10m / s. When the installation temperature is 10℃, the working tension is T1=24018N, the conductor operation acquisition temperature is t1=10℃, and the wind speed is V1=15m / s. The algorithm process meets the following requirements: First calculate the initial installation operating stress f1: Substituting f1 into formula (2) yields the constant variable Q: Where: q1 is the load factor under initial conditions; Wire gravity load δ = W * 9.80665 / A = 1.349 * 9.80665 / 425.24 = 0.0311 N / m.mm 2 ; Spacing L = 400m; Further obtain the intermediate variable M: M=f2 2 ×[f2-(Q-α·t·E)] (3) Where f2 represents the working stress of ice collection, α represents the expansion coefficient of the wire; the difference between the temperature during ice accumulation and the initial installation temperature t = (t2-t1); E represents the elastic modulus of the wire; According to the relationship between load factor, comprehensive load and weight, formula (4) is obtained: Where: q1 is the load factor under installation conditions; g1 is the self-weight load, N / m; g1 = W × 9.80665 = 1.349 * 9.80665 = 13.229 N / m, (5) Ice gravity load g2 = 9.80665 × 0.9π × k × (k + d) × 10 -3 N / m (6) Self-weight plus ice gravity load: g3 = g1 + g2 N / m (7) Wind load g5 = 0.625v2 × (d + 2K) × α × μ × 10 -3 N / m; (8) Comprehensive load g7: The value of the conductor wind pressure unevenness coefficient α meets the following requirements: α=1 when 10≤v<20m / s, α=0.85 when 20≤v<30m / s, α=0.75 when 30≤v<35m / s, α=0.70 when v≥35m / s; The conductor body coefficient μ meets the following requirements: μ = 1.2 when the conductor outer diameter d < 17 mm, μ = 1.1 when the conductor outer diameter d ≥ 17 mm, and μ is uniformly set to 1.2 when covered with ice; π=3.1415926, load factor q1 under installation condition: q1=g7 / g1 (10) Substitute the above f1, q1, δ, L, and E into formula (2) to obtain Q; Then substitute Q, f2, α, t, and E into formula (3) to obtain the variable M; And because M=(q 2 ·δ)·L 2 ·E / 24 (11) Given the load coefficient q2 at temperature t2, weight specific load δ = W × 9.80665 / AN / mm 2 , span L, conductor elastic modulus E; Formula (12) is derived from Formula (11): The formula is derived based on the relationship between the load factor, comprehensive load and weight: So g7=q2×g1 (13) By combining formula (5), (7), (8), (9), (12) and (11), we can get formula (14): Assumptions: A＝(π×0.9×10 -3 ) 2 B=2×(π×0.9×10 -3 ) 2 ×d C=2(π×0.9×10 -3 )·W+(π×0.9×10 -3 ) 2 ·d 2 +4×(0.063732·v 2 ×μ×α×10 -3 ) 2 D=2(π×0.9×10 -3 )·W·d+4·(0.063732·v 2 ×μ×α×10 -3 ) 2 ·d So we get: A×K 4 +B×K 3 +C×K 2 +D×K+E=0 (15) Calculate the K value according to formula (17); A=0.000008, B=0.000428499, C=0.013604256, D=0.210711599, E=-2.8085; Substitute the constant term and find K = 8 mm.

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