CN103499768A - Power cable real-time state monitoring and operation management system and measuring method of temperature of cable - Google Patents

Abstract

The invention provides a power cable real-time state monitoring and operation management system and a measuring method of the temperature of a cable. The power cable real-time state monitoring and operation management system comprises a distributed Raman temperature measurement sensing unit, a data acquisition subunit, an optical magnetic field sensing unit, a current data demodulator, an FPGA core processing subunit, an ARM core processing subunit, a magnetic field sensing head and an operation management server, wherein a temperature demodulator of the distributed Raman temperature measurement sensing unit and the current data demodulator of the optical magnetic field sensing unit are connected with the operation management server through Ethernet interfaces, an optical filter carries out band-pass filtering processing on Stokes light and Anti-Stokes light, light intensity signals of filtered back Raman scattering light are converted into electric signals through a photoelectric detection unit, the electric signals are amplified to obtain voltage signals corresponding to the temperature, the data acquisition subunit carries out A/D conversion on the voltage signals, an actual temperature value is obtained through calculation, the hidden danger of faults, with unobvious surface temperature rise, of the cable is eliminated, real-time fault recording is carried out on important cable taps, rapid contact locating of the hidden danger of the faults and accident analysis are facilitated, and real-time calculation of the current-carrying capacity is achieved.

Description

A kind of power cable real-time state monitoring and operation management system and cable temperature measuring method

Technical field

The present invention relates to a kind of power cable real-time state monitoring and operation management system and cable temperature measuring method,, belong to the power equipment monitoring technical field.

Background technology

Cable is the important component part of electric system, is distributed in cable duct, cable tunnel, cable testing bridge, cable interlayer, and artificial inspection is very inconvenient.The long-term charged work of cable, easily aging, inflammable fault odds is large, and causality loss is serious, is listed in one of 25 accidents of electric system key protection.According to statistics, in the electrical fire accident that China is caused by electrical equipment over the years, have 80% relevant with electric wire.Along with deepening continuously that the city net is built, the use amount of power cable increases considerably, so the operational management of power cable, monitoring and maintenance work are further important.

Existing state-of-the-art power cable state monitoring system is based on distributed optical fiber temperature sensor technology, utilize optical time domain reflection and Raman scattering technology, obtain the cable surface Temperature Distribution along the fiber lengths nearly continuity, realize that temperature anomaly changes the functions such as early warning, temperature overheating point location and the calculating of stable state current-carrying capacity.The weak point of this technology is: can not monitor in time and the instantaneous arcing fault of effective location or other transient fault; Can not realize that real-time current-carrying capacity calculates.The instantaneity of the transient faults such as flashover usually can not cause the significant change of cable surface temperature; During cable generation leakage failure, if leakage current is very little, the cable surface temperature rise changes also not obvious.Prior art, only based on distributed optical fiber temperature sensor technology, can not be monitored and early warning in time.Particularly cable splice the most easily breaks down, and finds that in time transient fault is conducive to the generation of early prevention accident.Fault current is through the cable conduction of long distance, and the fault-signal attenuation and distortion, be not easy to catch at transformer station's end.Therefore be necessary to carry out remote monitoring for important cable splice position, gather the transient fault signal, realize early warning and location.

The current-carrying capacity computing function needs a large amount of Real-time Load current data in real time, and prior art relies on electric substation automation system data are provided, and has increased the real-time Data Transmission flow in the transformer station, has affected the real-time of basic production scheduling operation; On the other hand, load current comes from automation device for transformer substation or distributing automation apparatus, is not easy to keep synchronism with optical fiber temperature monitoring system.

Summary of the invention

The object of the invention is to overcome the deficiencies in the prior art, a kind of power cable real-time state monitoring and operation management system are provided.Adopt the optical magnetic field sensing unit, for important cable splice position, carry out remote monitoring, gather the transient fault current signal, realize early warning and location; Optical magnetic field sensing technology and distributed optical fiber temperature sensor technology are organically combined, the distributed fiber temperature sensing unit provides the measuring point temperature for the optical magnetic field sensing unit, improved the accuracy of current measurement, the optical magnetic field sensing unit, for the distributed optical fiber temperature monitoring units synchronization provides real-time current data, is easy to realize that real-time current-carrying capacity calculates simultaneously.

The alleged problem of the present invention realizes with following technical proposals:

By distributed Raman thermometric sensing unit, data acquisition subelement, optical magnetic field sensing unit, current data (FBG) demodulator, fpga core processing subelement, ARM core processing subelement, magnetic field sensing head, operational management server, formed.The temperature (FBG) demodulator of distributed Raman thermometric sensing unit, the current data (FBG) demodulator of optical magnetic field sensing unit are connected with the operational management server by Ethernet interface respectively; Optical filter carries out bandpass filtering treatment to Stokes light and Anti-Stokes light, filtered Raman backscattering light through photodetector unit the light intensity signal switching electrical signals, obtain the voltage signal corresponding with temperature after amplification, the data acquisition subelement carries out the A/D conversion by voltage signal, through calculating actual temperature value.

Described optical magnetic field sensing unit comprises current data (FBG) demodulator, fl transmission optical fiber, light splitting coupler, backward Transmission Fibers, magnetism gathering rings and magnetic field sensing head.

Described current data (FBG) demodulator processes subelement by fpga core and ARM core processing subelement forms; Fpga core is processed subelement and is comprised light source, photoelectric commutator, amplifying circuit, A/D conversion chip, FPGA cpu chip, FPGA parallel interface and FPGA working power module; ARM core processing subelement comprises ARM working power, LCD interface, mouse and keyboard interface, Ethernet interface, ARM cpu chip, ARM parallel interface, alarm control interface and gsm communication interface; The magnetic field sensing head is comprised of the input collimating apparatus, the polarizer, magneto-optic element, analyzer, the output collimator that distribute successively along optical path direction; The light source that fpga core is processed subelement is connected with fl transmission optical fiber; The light splitting coupler of access 95:5 between the input collimating apparatus of fl transmission optical fiber and each sensing head; The output collimator of each sensing head connects through backward Transmission Fibers separately the photoelectric commutator that fpga core is processed subelement.

Described distributed Raman thermometric sensing unit comprises temperature sensing optical cable and temperature (FBG) demodulator two parts; The temperature (FBG) demodulator is comprised of thermometric working power subelement, optical processing subelement, data acquisition subelement and control subelement; The optical processing subelement comprises pulsed laser, photo-coupler, calibration cell, photoswitch, optical splitter, Stokes light optical filter, Stokes light photoelectric detector, Anti-Stokes light optical filter, Anti-Stokes light photoelectric detector; The data acquisition subelement comprises temperature measuring A/D C, thermometric FPGA CPU and parallel interface module; Control subelement and comprise LCD interface, mouse and keyboard interface, Ethernet interface, ARM cpu chip, ARM parallel interface module, alarm control interface and gsm communication interface.

Optical filter carries out bandpass filtering treatment to Stokes light and Anti-Stokes light, filtered Raman backscattering light through photodetector unit the light intensity signal switching electrical signals, obtain the voltage signal corresponding with temperature after amplification, the data acquisition subelement carries out the A/D conversion by voltage signal, the Raman scattering light intensity is relevant with temperature, and the pass of Stokes light and temperature is

the pass of Anti-Stokes light and temperature is strength ratio between the two is $R\left(T\right)=\frac{I_{\mathrm{as}}}{I_s}={\left(\frac{{\mathrm{\λ}}_s}{{\mathrm{\λ}}_{\mathrm{as}}}\right)}^4{e}^{-\mathrm{hc\Δ\γ}/\mathrm{kT}};$ Therefore, have: $\frac{1}{T}=-\frac{k}{\mathrm{hc\Δ\γ}}-[\ln R\left(T\right)+4\ln \left(\frac{{\mathrm{\λ}}_{\mathrm{as}}}{{\mathrm{\λ}}_s}\right)];$ For fixing temperature T 0 (calibration cell demarcation temperature), have:

?

λ s and λ as are respectively Stokes and Anti-Stokes light wavelength, and h is Planck's constant, and c is the light velocity in vacuum, k is Boltzmann constant, the skew wave number that Δ γ is Raman scattered light, T is absolute temperature, by measuring R (T), just can determine the temperature value along optical fiber measurement point.

Beneficial effect: get rid of the unconspicuous potential faults of cable surface temperature rise; Realize real time fail record ripple for important cable tap, be beneficial to quick potential faults contact location and crash analysis; Realize that real-time current-carrying capacity calculates.

The accompanying drawing explanation

Below in conjunction with accompanying drawing, the present invention is further described.

Fig. 1 is system architecture schematic diagram of the present invention;

The structural representation that Fig. 2 is the optical magnetic field sensing unit;

The structural representation that Fig. 3 is distributed Raman thermometric sensing unit;

The monitoring that Fig. 4 is system of the present invention and operational management process flow diagram;

Embodiment

Referring to Fig. 1, power cable real-time state monitoring and operation management system that the present invention proposes comprise: distributed Raman thermometric sensing unit (1), optical magnetic field sensing unit (2), operational management server (3).The temperature (FBG) demodulator (4) of distributed Raman thermometric sensing unit (1), the current data (FBG) demodulator (5) of optical magnetic field sensing unit (2) are connected with operational management server (3) by Ethernet.Distributed Raman thermometric sensing unit (1) Real-Time Monitoring cable surface temperature, once occur overheatedly, can automatically control audible-visual annunciator action, and corresponding warning message be sent to automatically on managerial personnel's mobile phone; Optical magnetic field sensing unit (2) provides the momentary current information of critical cables joint, once occur extremely, can automatically control the audible-visual annunciator action, and corresponding warning message be sent to automatically on managerial personnel's mobile phone; Operational management server (3) is when completing current-carrying capacity calculating, crash analysis and early warning, data storage and the functions such as demonstration, local man-machine interaction, also temperature, electric current and positional information are transferred to monitoring central station or office dispatching center by LAN (Local Area Network), realize sharing of information.The network of operational management server (3) and remote monitoring client is connected the .NET framework based on Microsoft, adopts the B/S structure, without client is installed, facilitates the use of all types of user in LAN (Local Area Network); The browser access temp measuring system that arbitrary client of networking all can carry by operating system after authentication, running status, running log and the management maintenance information of checking cable.

Referring to Fig. 1, referring to Fig. 2, optical magnetic field sensing unit (2) comprises current data (FBG) demodulator (5), light splitting coupler (6), fl transmission optical fiber (7), backward Transmission Fibers (8), magnetic field sensing head (9) and magnetism gathering rings (10).Described current data (FBG) demodulator (5) processes subelement (51) by fpga core and ARM core processing subelement (52) forms; Described fpga core is processed subelement (51) and is comprised light source, photoelectric commutator, amplifying circuit, A/D conversion chip, FPGA cpu chip, FPGA parallel interface and FPGA working power module; Described ARM core processing subelement (52) comprises that ARM makes power supply, LCD interface, mouse and keyboard interface, Ethernet interface, ARM cpu chip, ARM I/O Parallel interface, alarm control interface and gsm communication interface.Described magnetic field sensing head (9) is comprised of the input collimating apparatus (91) distributed successively along optical path direction, the polarizer (92), magneto-optic element (93), analyzing optical splitter (94), output collimator (95); Magnetic field sensing head (9) is placed in the air gap of magnetism gathering rings (10); Magnetism gathering rings (10) adopts the crystallite magnetic material, has good frequency characteristic, adopts two semi-loops, during installation, needn't disconnect cable, and outside is wound around adhesive waterproof tape.The light source that fpga core is processed subelement (51) is connected with fl transmission optical fiber (7); The light splitting coupler (6) of access 95:5 between the input collimating apparatus (91) of fl transmission optical fiber (7) and each sensing head; The output collimator of each sensing head (95) connects through backward Transmission Fibers (8) separately the photoelectric commutator that fpga core is processed subelement (51).Described magnetic field sensing head (9) is arranged on the cable splice part of easy fault.

In the present embodiment, light source adopts the high-brightness light emitting diode that wavelength is 1550nm, and light source driving circuit is that constant current output is to reduce the fluctuation of light intensity.The steady and continuous light that light source sends, transfer to light splitting coupler (6) by fl transmission optical fiber (7) and be divided into two-way, and a road is carried 95% luminous energy and is transferred to next magnetic field sensing head (9); The input light P0 that 5% luminous energy is carried on another road becomes directional light through input collimating apparatus (91), becomes linearly polarized light through the polarizer (92) and enters magneto-optic element (93).Be arranged in the approximate uniform magnetic field of magneto-optic element (93) in being produced by electric current of magnetism gathering rings (10) air gap, faraday's magneto-optical deflection when passing through magneto-optic element (93), linearly polarized light occurs, its plane of polarization will rotate, the angle of rotation is called Faraday rotation angle θ, proportional with electric current:

. the angle between the light transmission shaft of the light transmission shaft of analyzer (94) and the polarizer (92) is 45., angle value is converted into to output intensity .P be coupled into backward Transmission Fibers (8) through output collimator (95), be transferred to current data (FBG) demodulator (5).The photoelectric commutator of current data (FBG) demodulator (5) is converted to light signal and the proportional electric signal of light intensity, then passes through amplifying circuit output voltage signal u, has:

r is conversion coefficient, relevant with the coupling situation of photoelectric detector parameter and each optical device.Fpga core is processed subelement u is carried out to the A/D conversion, presses following method demodulation current information:

When the θ angle hour, formula

can be reduced to: , wherein the 2nd is AC compounent, the variation of reflection alternating current i; The 1st is DC component, is made as respectively uAC, uDC.Adopt interchange overcome the impact of light source intensity fluctuation and solve electric current than DC terms:

, wherein:

temperature influence just can utilize the temperature-measuring results of distributed Raman thermometric sensing unit (1) and needn't consider extra temperature compensation measure in system of the present invention.

The sensing no-load voltage ratio of symbol used: K (T), magnetic field sensing head above, P0, input light intensity, P, sensing head output intensity, the voltage signal of u, P output after opto-electronic conversion and amplification, the Verdet constant of V (T), magneto-optic element, 1, the logical light length of magneto-optic element, i, tested electric current, the Faraday rotation angle of θ, magneto-optic element, T, temperature, μ 0, permeability of vacuum, the spacing at d, magnetic field sensing head and Ampereconductors center, the magnetic induction density that B, d place current i produce, the magnetic field intensity that H, d place current i produce, the conversion coefficient of R, magnetic field sensing head.

In the present embodiment, each magneto-optic sensing head (9) needs a set of photoelectric commutator and amplifying circuit, is called a sense channel; Fpga core is processed subelement (51) and is comprised 6 passage A/D conversion chips, can access 6 sense channels simultaneously.Fpga core is processed the number of subelement (51) and is determined according to the cable splice quantity that will monitor.Fpga core is processed subelement (51) and is realized opto-electronic conversion and current data demodulation function.

Fpga core is processed subelement (51) and is realized parallel high speed data transfer as the peripheral hardware of ARM core processing subelement (52).ARM core processing subelement (52) comprises ARM working power, LCD interface, mouse and keyboard interface, Ethernet interface, ARM cpu chip, ARM I/O Parallel interface, alarm control interface and gsm communication interface.ARM core processing subelement (52) is realized the functions such as demonstration, man-machine interaction and debugging, ethernet communication, the gsm communication of current data.Real-time current effective value and fault current waveform are stamped markers and are transmitted to operational management server (3) by Ethernet interface.

Referring to Fig. 1, referring to Fig. 3, described distributed Raman thermometric sensing unit (1) comprises temperature sensing optical cable (11) and temperature (FBG) demodulator (4) two parts.Described temperature (FBG) demodulator (4) is comprised of optical processing subelement (41), data acquisition subelement (42), control subelement (43) and thermometric working power subelement (44).Described optical processing subelement (41) comprises pulsed laser, photo-coupler, calibration cell, photoswitch, optical splitter, Stokes light optical filter, Stokes light photoelectric detector, Anti-Stokes light optical filter, Anti-Stokes light photoelectric detector.Described data acquisition subelement (42) comprises temperature measuring A/D C, thermometric FPGA CPU and parallel interface module.Described control subelement (43) comprises LCD interface, mouse and keyboard interface, Ethernet interface, ARM cpu chip, ARM parallel interface, alarm control interface and gsm communication interface.Temperature sensing optical cable (11) is banded in cable surface usually.The core of temp measuring system and key are temperature (FBG) demodulator (4), and its principle of work is: pulsed laser sends the short light pulse of some cycles and duration, and pulsed light enters optical fiber and the temperature sensing optical cable (11) in calibration cell by photo-coupler.In the transmitting procedure of light pulse, in temperature field, the scattered light signal of different distance point returns through photo-coupler along the transmission light path.Raman scattered light has comprised two kinds of frequency contents: Stokes light and Anti-Stokes light, its frequency distribution is in the both sides of incident light frequency.Optical splitter by the light of two different frequencies separately, enters respectively different passages and is processed.Owing to also being mingled with other scattered light and stray light in scattered light, so need to adopt optical filter to carry out bandpass filtering treatment, obtain being close to pure Raman scattered light.Filtered Raman backscattering light the light intensity signal switching electrical signals, obtains the voltage signal corresponding with temperature through photodetector unit after amplification.Data acquisition subelement (42) carries out the A/D conversion by voltage signal, through calculating actual temperature value.Realize that thermometric ultimate principle is: the Raman scattering light intensity is relevant with temperature, and the pass of Stokes light and temperature is

the pass of Anti-Stokes light and temperature is $I_{\mathrm{as}}\∝{(e^{\mathrm{hc\Δ\γ}/\mathrm{kT}}-1)}^{-1}{\mathrm{\λ}}_{\mathrm{as}}^{-4};$ Strength ratio between the two is $R\left(T\right)=\frac{I_{\mathrm{as}}}{I_s}={\left(\frac{{\mathrm{\λ}}_s}{{\mathrm{\λ}}_{\mathrm{as}}}\right)}^4{e}^{-\mathrm{hc\Δ\γ}/\mathrm{kT}};$ Therefore, have: for fixing temperature T 0 (calibration cell demarcation temperature), have: $\frac{1}{T_0}=-\frac{k}{\mathrm{hc\Δ\γ}}[\ln R\left(T_0\right)+4\ln \left(\frac{{\mathrm{\λ}}_{\mathrm{as}}}{{\mathrm{\λ}}_s}\right)];$ ? $\frac{1}{T}=\frac{1}{T_0}-\frac{k}{\mathrm{hc\Δ\γ}}[\ln R\left(T\right)-\ln R\left(T_0\right)];$ λ s and λ as are respectively Stokes and Anti-Stokes light wavelength, and h is Planck's constant, and c is the light velocity in vacuum, and k is Boltzmann constant, the skew wave number that Δ γ is Raman scattered light, and T is absolute temperature.By measuring R (T), just can determine the temperature value along optical fiber measurement point as seen.

Space orientation to measurement point is to realize by optical time domain reflection (OTDR, Optical Time Domain Reflection) technology.When laser pulse transmits in optical fiber, it is t that incident light turns back to optical fiber incident end required time through backscattering, and the distance that laser pulse is passed by optical fiber is 2L,

n is refractive index.Therefore, utilize optical time domain reflection technology can determine along each temperature acquisition in the fiber optic temperature field put the distance of incident end and abnormal temperature point, fibercuts point apart from locating information.

The long temperature sensing optical cable of general every 4km forms a passage, and number of channels m determines according to total cable length, adopts photoswitch timesharing switching between each passage.Data acquisition subelement (42) is converted to light intensity signal electric signal and realizes the temperature demodulation function.Data acquisition subelement (42) is realized parallel high speed data transfer as the peripheral hardware of controlling subelement (43).Control subelement (43) and realize the functions such as demonstration, man-machine interaction and the debug function of temperature data, ethernet communication, gsm communication.The real time temperature value is stamped markers and is sent to operational management server (3) by Ethernet interface.

Referring to Fig. 4, the Real-Time Monitoring of system of the present invention and operational management flow process are:

The temperature real time data that distributed Raman thermometric sensing unit (1) obtains, judged whether that temperaturing lifting abnormality point or temperature surpass threshold point, if having send warning message and provide failure analysis report; The real-time current data that optical magnetic field sensing unit (2) obtains, judged whether the current anomaly point, if having send warning message and provide failure analysis report;

Operational management server (3) receives real time temperature data and current data, carries out real-time current-carrying capacity calculating, has judged whether that electric current surpasses real-time current-carrying capacity point, has and sends early warning information and provide failure analysis report;

During normal operation, complete real-time current-carrying capacity calculating, man-machine interaction and debugging, data storage and demonstration, system operation and maintenance admin log, remote data access etc.

In the present embodiment, for the most frequently used single-core crosslinked tygon (XLPE) cable, the current-carrying capacity computing method are in real time:

To the current-carrying capacity computing method under 100% operating load condition, provide formula according to the IEC60287 standard pin

$I=\sqrt{\frac{({\mathrm{\&theta;}}_c-{\mathrm{\&theta;}}_a)-W_d(0.5{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="HSA0000091969630000012.png"\; state="\{\{state\}\}">T</figure-callout>}}_1+T_2+T_3)}{r[{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="HSA0000091969630000012.png"\; state="\{\{state\}\}">T</figure-callout>}}_1+(1+{\mathrm{\&lambda;}}_1)T_2+(1+{\mathrm{\&lambda;}}_1+{\mathrm{\&lambda;}}_2)T_3]}}---\left(1\right)$

Wherein, r is the AC resistance (Ω/m) of cable conductor, T ₁, T ₂, T ₃be respectively insulation course thermal resistance, inner liner thermal resistance, serving thermal resistance (Km/W), λ ₁, λ ₂for protective metal shell loss factor, armouring loss factor, W _dbe the dielectric loss (J/m) of cable unit length, above parameter adopts cable operating experience numerical value, θ _cfor the nominal operation temperature (the highest permission working temperature for crosslinked polyethylene commonly used (XLPE) insulated conductor is 90 ℃) that cable allows, θ _afor the cable surface temperature.

For the IEC60287 standard, ambient condition is made to simple homogeneity hypothesis and cause the poor deficiency of computational accuracy, utilize the real-time current data, determine that real-time correction factor η equals the variation numerical value of load current according to the changing value of dynamic current-carrying capacity, have

i wherein _f1and I _f2be respectively t1 and t2 load current (being provided in real time by the magnetic field sensing unit) constantly, I ₁and I ₂be respectively according to formula (1) and calculate respectively the current-carrying capacity (t1 and t2 cable surface temperature is constantly provided in real time by temperature sensing unit) obtained.

Current-carrying capacity is revised in real time, and revised t2 real-time current-carrying capacity constantly is made as I _r, I _rthe beneficial effect that the real-time current-carrying capacity of=η I this patent calculates is: traditional IEC60287 provides the method for 100% stable state current-carrying capacity to make simple hypothesis, and its result of calculation is relevant with many uncertainties all the time; For these worries, the actual load of power department control cables usually is no more than and calculates 70% of ratings at present; This means underutilization of resources.This patent utilizes real time temperature and current data, and current-carrying capacity result of calculation is revised, and guarantees that cable has improved again the utilization factor of cable when the situation of overheated and premature ageing can not occur.In addition, while in certain part of system, emergency occurring, can utilize carrying load ability to reconfigure fast system according to the topological structure of system and the reality of cable; Utilize the cable that the remaining load ability is large that the load support to faulty line is provided at short notice, in order to make system can enter as early as possible urgent running status, guarantee uninterrupted power supply.The calculating that this patent method completes current-carrying capacity according to cable jacket temperature and the real-time current of Real-Time Monitoring, thereby environment temperature in existing current-carrying capacity computing method and the impact of soil thermal resistivity have been eliminated, improved measuring accuracy, compared with numerical computation method and there is the computation process Simple fast.

Claims (5)

1. a power cable real-time state monitoring and operation management system and cable temperature measuring method is characterized in that: process subelement, ARM core processing subelement, magnetic field sensing head, operational management server by distributed Raman thermometric sensing unit, data acquisition subelement, optical magnetic field sensing unit, current data (FBG) demodulator, fpga core and form.The temperature (FBG) demodulator of distributed Raman thermometric sensing unit, the current data (FBG) demodulator of optical magnetic field sensing unit are connected with the operational management server by Ethernet interface respectively; Optical filter carries out bandpass filtering treatment to Stokes light and Anti-Stokes light, filtered Raman backscattering light through photodetector unit the light intensity signal switching electrical signals, obtain the voltage signal corresponding with temperature after amplification, the data acquisition subelement carries out the A/D conversion by voltage signal, through calculating actual temperature value.

2. a kind of power cable real-time state monitoring according to claim 1 and operation management system and cable temperature measuring method, it is characterized in that: described optical magnetic field sensing unit comprises current data (FBG) demodulator, fl transmission optical fiber, light splitting coupler, backward Transmission Fibers, magnetism gathering rings and magnetic field sensing head.

3. a kind of power cable real-time state monitoring according to claim 1 and operation management system and cable temperature measuring method is characterized in that: described current data (FBG) demodulator processes subelement by fpga core and ARM core processing subelement forms; Fpga core is processed subelement and is comprised light source, photoelectric commutator, amplifying circuit, A/D conversion chip, FPGA cpu chip, FPGA parallel interface and FPGA working power module; ARM core processing subelement comprises ARM working power, LCD interface, mouse and keyboard interface, Ethernet interface, ARM cpu chip, ARM parallel interface, alarm control interface and gsm communication interface; The magnetic field sensing head is comprised of the input collimating apparatus, the polarizer, magneto-optic element, analyzer, the output collimator that distribute successively along optical path direction; The light source that fpga core is processed subelement is connected with fl transmission optical fiber; The light splitting coupler of access 95:5 between the input collimating apparatus of fl transmission optical fiber and each sensing head; The output collimator of each sensing head connects through backward Transmission Fibers separately the photoelectric commutator that fpga core is processed subelement.

4. a kind of power cable real-time state monitoring according to claim 1 and operation management system and cable temperature measuring method, it is characterized in that: described distributed Raman thermometric sensing unit comprises temperature sensing optical cable and temperature (FBG) demodulator two parts; The temperature (FBG) demodulator is comprised of thermometric working power subelement, optical processing subelement, data acquisition subelement and control subelement; The optical processing subelement comprises pulsed laser, photo-coupler, calibration cell, photoswitch, optical splitter, Stokes light optical filter, Stokes light photoelectric detector, Anti-Stokes light optical filter, Anti-Stokes light photoelectric detector; The data acquisition subelement comprises temperature measuring A/D C, thermometric FPGA CPU and parallel interface module; Control subelement and comprise LCD interface, mouse and keyboard interface, Ethernet interface, ARM cpu chip, ARM parallel interface module, alarm control interface and gsm communication interface.

5. a kind of power cable real-time state monitoring according to claim 1 and operation management system and cable temperature measuring method, it is characterized in that: optical filter carries out bandpass filtering treatment to Stokes light and Anti-Stokes light, filtered Raman backscattering light through photodetector unit the light intensity signal switching electrical signals, obtain the voltage signal corresponding with temperature after amplification, the data acquisition subelement carries out the A/D conversion by voltage signal, the Raman scattering light intensity is relevant with temperature, and the pass of Stokes light and temperature is

the pass of Anti-Stokes light and temperature is strength ratio between the two is $R\left(T\right)=\frac{I_{\mathrm{as}}}{I_s}={\left(\frac{{\mathrm{\&lambda;}}_s}{{\mathrm{\&lambda;}}_{\mathrm{as}}}\right)}^4{e}^{-\mathrm{hc\&Delta;\&gamma;}/\mathrm{kT}};$ Therefore, have: $\frac{1}{T}=-\frac{k}{\mathrm{hc\&Delta;\&gamma;}}-[\ln R\left(T\right)+4\ln \left(\frac{{\mathrm{\&lambda;}}_{\mathrm{as}}}{{\mathrm{\&lambda;}}_s}\right)];$ For fixing temperature T ₀(calibration cell demarcation temperature) has:

; ?

λ _sand λ _asbe respectively Stokes and Anti-Stokes light wavelength, h is Planck's constant, and c is the light velocity in vacuum, k is Boltzmann constant, the skew wave number that Δ γ is Raman scattered light, T is absolute temperature, by measuring R (T), just can determine the temperature value along optical fiber measurement point.

Images