CN103868619B - The temperature detection sensor system of transmission line-oriented - Google Patents

Abstract

The temperature detection sensor system facing transmission lines provided by the present invention includes: transmission lines, screws, microstrip antennas, insulating layers, metal heat conduction parts, heat insulation parts and multiple sensors; the sensors arranged in the metal casings of transmission lines pass through The metal heat conduction part is connected to the wire core of the transmission line, and is connected to the metal casing of the transmission line through the heat insulation part; the microstrip antenna is connected to the outside of the metal casing of the transmission line by screws, and a Insulation. The long-distance, multi-point connection and anti-interference surface acoustic wave wireless sensor method provided by the present invention solves the "near and far effect" of the code division multiplexing coded passive sensor system, and can meet the requirements of the smart grid for wireless monitoring of the temperature of power equipment Require.

Description

Temperature Detection Sensor System for Power Transmission Lines

technical field

The invention relates to the field of temperature monitoring of power equipment, in particular to a temperature detection sensor system for power transmission lines.

Background technique

Among the many monitoring quantities of power equipment status monitoring, temperature is one of the most critical detection quantities. Through temperature monitoring, the operating status and fault information of power equipment can be understood in a timely and accurate manner. Monitoring the operating temperature of power equipment, such as the oil temperature of transformers, and the conductor temperature of transmission lines (overhead lines and power cables) can be used to calculate the load limit capacity and equipment aging degree, thereby providing a basis for dynamic capacity increase or maintenance of power equipment. Monitor the temperature of the stator and rotor of the generator, high-voltage switchgear, busbar joints, outdoor knife switch, circuit breaker contacts, capacitors, reactors, high-voltage cables, transformers, etc., and can find out in time when abnormal conditions or faults occur Accompanying local or global overheating or relative anomalies in temperature distribution can also provide historical data for failure analysis.

Existing technical solutions for temperature monitoring of power equipment mainly include infrared temperature measurement, active wireless temperature measurement, and distributed optical fiber temperature measurement. Infrared temperature measurement is greatly affected by environmental conditions, and the cost of the scheme is also high. Active wireless temperature measurement schemes generally use batteries or current transformers (CT) to power the temperature measurement chip after being powered, and the sensing distance is very long. However, in harsh environments such as high temperature, ultra-low temperature, and strong electromagnetic fields, there are problems with the life of batteries and electronic components. Active sensors that use CT to get power, because the coils that get power from CT have installation location requirements, cannot supply power even when the line is faulty, and its application also has great limitations. Optical fiber temperature measurement belongs to the wired temperature measurement method, and the optical fiber or its sheath on the primary side of the high voltage measurement has insulation problems to the ground. At the same time, the optical fiber is easy to break and break. In addition, the cost of optical fiber sensor equipment is relatively high.

The wireless temperature sensor based on surface acoustic wave (SAW for short) technology uses piezoelectric materials, which has pure passive and wireless characteristics, and does not need to consider issues such as sensor power supply, high-voltage insulation, and equipment rotation; it can withstand High temperature and low temperature (~-200~1000°C); it does not involve the migration process of electrons in semiconductor materials, long life, strong anti-discharge shock and anti-electric field, magnetic field and other interference capabilities; small sensor size (centimeter level), light weight, Easy structure design and installation. It can be seen that SAW wireless sensing technology provides an ideal technology platform with broad application prospects for temperature monitoring of power equipment.

However, the currently developed SAW wireless sensor array cannot fully meet the temperature monitoring requirements in smart grid and UHV applications. The problems mainly include:

Problem 1: The working distance is not enough. Taking the temperature monitoring of dynamic capacity expansion of overhead lines as an example, if the installed SAW reader is considered as the center of the sphere, the effective radius is at least about 30 meters. The SAW wireless sensor developed by US Sengenuity Company for temperature monitoring of switch cabinets has a temperature measurement distance of only 2 meters. The SAW wireless temperature measurement system developed by Brunsbüttel, Preussen Elektra and Darmstadt University of Technology in Germany in the late 1990s is used for applications such as power transmission lines, semiconductor oxide arresters, and isolating switches. The working distance can reach 10 meters, but In order to popularize and apply it in power equipment monitoring, its working distance still needs to be further improved.

Problem 2: The number of temperature points detected at the same time is not enough. In the monitoring of transmission lines, consider the three-phase AC high-voltage transmission line on the same tower. If it is installed on the transmission line connected to both sides of the tower, consider the situation of multiple circuits on the same pole and the ambient temperature that needs to be calculated by the conductor temperature model. For monitoring and other situations, the number of sensors should be at least 7 or more. The temperature monitoring requirements for transformer oil temperature, switchgear temperature and other electrical equipment have similar requirements for the number of sensors. The number of sensors in the SAW wireless sensor array for switchgear temperature monitoring developed by Sengenuity of the United States can reach 6 (using 3 antennas, up to 18 after implementing space division multiplexing), but it occupies a bandwidth of 20MHz, far exceeding The 1.87MHz bandwidth requirement allowed by the 433MHz band. The SAW wireless sensor for electric temperature measurement developed by domestic Huazhong University of Science and Technology, Shanghai Jiaotong University, Chongqing University, and the Institute of Acoustics of the Chinese Academy of Sciences also belongs to this working method.

Question 3: The anti-interference performance of the sensor needs to be improved. With the wide application of wireless sensors in the "smart grid", the possibility of the sensing array being affected by sudden and in-band co-frequency interference has greatly increased; in various applications of the "smart grid", the frequency selection of different scenarios The effects of sexual fading, multipath effect, and climate environment are also different, which may cause the interruption of the wireless link of the passive sensor, the loss of echo data, or the measurement outliers due to poor signal-to-noise ratio. These factors seriously affect the reliability of the sensing array, which may cause false alarms or even malfunction of relay protection.

In recent years, some scholars have proposed a SAW radio frequency tag sensing technology scheme using Orthogonal Frequency Coding (OFC). This scheme draws on the idea of Orthogonal Frequency Division Multiplexing (OFDM) in wireless communication, which can effectively overcome the frequency selective fading of the channel, and is conducive to improving the reliability of SAW sensors. At the same time, each reflective grating of OFC's SAW wireless sensor is narrow-band, and basically does not reflect other orthogonal frequencies. Compared with the reflective delay line SAW sensor, the reflectivity of each reflective grid is no longer only about 10% (otherwise the subsequent reflective grid will not receive the query pulse energy), but can reach 40-50%. Only the reflection loss of the reflection grid, the SAW sensor using OFC can reduce the insertion loss by 12-13dB. Orthogonal frequency division coding is a kind of spread spectrum coding, which is similar to intrapulse information modulation radar. When the sensor is demodulating, it can increase the signal-to-noise ratio of 20log ₁₀ N according to the number of chips N contained in each bit, which is beneficial to the Increased distance. According to literature reports, OFC-encoded SAW radio frequency tags (RFID) have a reading distance of up to 60 meters. However, there are still some difficulties to be overcome when this encoding method is used for temperature sensors:

Difficulty 1: Because it is sensitive to temperature, piezoelectric materials with low temperature coefficients cannot be selected as substrate materials like OFC-RFID. However, due to temperature changes, similar to the Doppler frequency shift generated by OFDM in communication systems, the original condition of mutually orthogonal frequencies is destroyed. When the reader demodulates the sensor information, the correlation peak performance drops sharply as the temperature range increases. The temperature measurement range reported in the literature is only 55 degrees.

Difficulty 2: OFC itself does not have multiple access capabilities. SAW devices are purely passive and can only passively reflect inquiry signals, but cannot actively control when to send or stop sending information. When the reader wants to query and read multiple OFC-SAW sensors at the same time, the existing solution is to combine time division multiplexing with OFC coding. However, due to the limitation of the applicable wireless bandwidth and the length of the SAW substrate material, it is difficult to realize 8 kinds of piezoelectric substrates on a 10 mm long piezoelectric substrate (which is already the limit, and the propagation loss and diffraction loss of SAW will be unacceptably large if it is longer). above sensor types.

Contents of the invention

Aiming at the defects in the prior art, the object of the present invention is to provide a temperature detection sensor system for transmission lines.

According to the temperature detection sensor system for transmission lines provided by the present invention, it includes: transmission lines, screws, microstrip antennas, insulating layers, metal heat conducting parts, heat insulating parts and multiple sensors;

The sensor includes: a one-way interdigital transducer, a frequency orthogonal reflective grating chip group;

The frequency orthogonal reflective grating chip group includes: n sequentially arranged chips;

The n chips constitute a sensor code;

Each chip consists of a periodic electrode that reflects an orthogonal sub-frequency;

The sub-frequencies formed between the plurality of chips are orthogonal to each other;

The time-domain length of each chip reflection signal remains the same, satisfying the orthogonal condition;

The sensor set in the metal casing of the transmission line is connected to the core of the transmission line through the metal heat conducting part, and connected to the metal casing of the transmission line through the heat insulation part; the microstrip antenna is connected to the outside of the metal casing of the transmission line by screws, and the microstrip An insulating layer is arranged between the antenna and the metal casing of the transmission line.

Preferably, in each frequency orthogonal reflective grating chip group, an equal fixed time delay τ _D is set between adjacent chips as protection padding, so as to superimpose and interact with different frequency signals in the time domain space The effect forms a partition to suppress interference between sub-frequency.

Preferably, the sensor is a sensor optimized through the following steps:

-Using Green's function combined with finite element tools to optimize the structure of the SAW sensor transducer and reflective grid to reduce insertion loss, specifically: according to different orientations on the lithium niobate substrate, the transducer and open circuit, short circuit, floating finger reflective grid Under the fundamental frequency and the second harmonic frequency: the number of fingers, metallization thickness, metallization rate and floating finger topological weighting, position weighting and reflection, transmission coefficient amplitude and phase change law, calculate the number of different fingers, metal The reflection coefficient and transmission coefficient of the reflective grating under the conditions of metallization thickness and metallization rate. Using its regularity, a SAW sensor with the same reflection coefficient of each orthogonal frequency component is designed. Using the temperature coefficient described by Lagrangian and bringing in the Green's function, the reflection grating topology with the lowest temperature change slope for the reflection characteristics of each orthogonal frequency is optimized to reduce the influence of temperature on the reflectivity and ensure that the reading distance of the sensor does not increase with temperature and decreased significantly.

Preferably, the sensor codes formed by the frequency orthogonal reflective grating chip groups contained in different sensors are different.

Preferably, in a sensor array composed of multiple sensors, the sub-frequency formed by the first chip corresponding to each sensor code is different, and the arrangement of the sub-frequency formed by the following n-1 chips adopts a random code, Based on precoding with the largest carrier-to-interference ratio or Turbo code coding.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention proposes a long-distance, multi-point connection and anti-interference surface acoustic wave wireless sensor method based on orthogonal frequency, which is an innovation, because this technical route can better solve code division multiplexing by means of orthogonal frequency technology The "far and near effect" of the coded passive sensor system can simultaneously read the system with the farthest range of multiple passive SAW sensors, which meets the requirements of the smart grid for wireless monitoring of the temperature of power equipment. In terms of specific technical routes, there are two research characteristics. One is to solve the problem that the orthogonal frequency code will be non-orthogonal after being affected by temperature. The present invention proposes that adding the protection filling between the reflection grids can ensure the reflection of each sub-frequency signal between the chips on the SAW sensor. No mutual interference will be formed. Even if each chip is affected by temperature and the reflection frequency shifts, this time slot can also form a barrier to the superposition and mutual influence of different frequency signals in the time domain space, suppressing the interference between sub-frequency interference. The second is that when using the reflection grid of the surface acoustic wave device to represent the orthogonal frequency code, the present invention uses the generalized Green's function combined with the finite element theory to accurately analyze the reflection of the Rayleigh wave at the fundamental frequency and the harmonic frequency of the reflection grid composed of sparse electrodes. , transmission and scattering, and other physical problems, which solve the shortcomings of slow calculation speed and low calculation accuracy of body wave scattering in the international Fourier transform method.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is the overall framework of the power equipment temperature monitoring scheme based on the OFC surface acoustic wave sensor of the present invention;

Fig. 2 is the time-frequency characteristic of multi-sensor code division multiplexing encoding;

Fig. 3 is a schematic diagram of adaptive matched filtering based on code division multiple access;

Figure 4 shows the sensor structure for temperature monitoring of transmission lines.

In the picture:

101 is the counterpart bolt;

102 is the wire core of the transmission line;

103 is a screw;

104 is a microstrip antenna;

105 is a surface acoustic wave sensor;

106 is the metal casing of the transmission line.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

The invention provides a SAW (passive wireless) sensor technology combining code division multiple access (CDMA) and OFC coding. Code division multiple access is a good way to solve multiple access in mobile communication. However, passive SAW sensors cannot actively perform power equalization like communication devices, that is, when multiple sensors and readers have "near and far effects", the echo amplitudes differ greatly, and the information of each sensor cannot be separated through correlation calculations. Therefore, A SAW sensor array with CDMA encoding alone is not practical. However, if the orthogonal frequency coding is combined with CDMA, the power balance can be realized by estimating the spectrum size of each orthogonal frequency first, and then the multi-sensor information can be separated and solved one by one. Since all reflected echo signals of the SAW sensor in this way are allowed to overlap each other in the time domain, they can be well separated in the time-frequency two-dimensional space. In addition, the designed sensor echo signals can realize code division multiplexing More than 8 different sensors can be implemented easily.

The SAW sensor combined with orthogonal frequency and CDMA code can adopt a demodulation method different from the current OFC-SAW temperature sensor when measuring temperature. On the one hand, it is possible to accurately calculate the relationship between the reflection characteristics of the SAW reflection grating and each orthogonal frequency as a function of temperature, and optimize the topology structure of the reflection grating with the lowest slope of the reflection characteristics of each orthogonal frequency to the temperature change, and reduce the influence of temperature on the reflectivity. Ensure that the reading distance of the sensor does not decrease significantly as the temperature increases; on the other hand, a demodulation method based on the measured temperature adaptive search and matched filtering can be used to obtain the measured temperature value while obtaining the matching output.

In order to solve the temperature monitoring requirements of "smart grid" power equipment, especially UHV power equipment, this invention proposes a surface acoustic wave passive wireless sensing method based on the combination of orthogonal frequency coding and code division multiple access to realize remote Distance, multi-point connection measurement, and high-reliability temperature monitoring.

The overall framework of the monitoring system that can be realized by using the present invention will be described below.

As shown in Figure 1, the temperature monitoring model space of the constructed power equipment includes: readers, broadband antennas, and multiple surface acoustic wave sensors. Among them, the surface acoustic wave sensor includes: a one-way interdigital transducer, a frequency orthogonal reflective grating chip group; the surface acoustic wave sensor 1~N are randomly distributed (according to the actual needs of power equipment monitoring, the value of N is between 8 and 10 room upon request).

The temperature monitoring signal processing flow is as follows:

Step 1: The reader transmits an upchirp query signal through a broadband antenna, and the upchirp query signal propagates to the surface acoustic wave sensor in the strong electromagnetic interference channel A;

Step 2: The surface acoustic wave sensor receives the OFC signal through the unidirectional interdigital transducer according to the upper chirp query signal and converts it into a surface acoustic wave signal;

Step 3: Let the surface acoustic wave signal be reflected by the frequency orthogonal reflective grating chip group and pass through the unidirectional interdigital transducer to form an echo signal;

Step 4: The echo signal propagates to the reader in the strong electromagnetic interference channel A, and the reader receives the echo signal through the broadband antenna and performs downchirp;

Step 5: The reader performs signal processing such as demodulation of the down-chirped echo signal, and performs multi-sensor identification and temperature information extraction.

Among them, the up and down linear frequency modulation can increase the processing gain by about 20-50, which is beneficial to improve the working distance of the surface acoustic wave sensor.

The technical route of OFC combined with CDMA coding will be described below.

As shown in the lower right corner of Figure 1, the surface acoustic wave sensor contains 8 chips s f ₀ ~ f ₇ and constitutes a code, where a chip refers to a chip. Each chip is composed of a periodic electrode to form a reflection of an orthogonal sub-frequency; the sub-frequency formed between multiple chips is orthogonal to each other. The number of electrodes in each chip should be designed according to the orthogonal frequency coding theory to ensure that the time-domain length of the reflected signal of each chip remains consistent (corresponding to the time delay τ _C in Figure 1 in the time response), satisfying the positive Pay conditions. The arrangement order of each chip is different to form other codes. For example: the arrangement order of f ₆ , f ₄ , f ₀ , f ₇ , f ₁ , f ₂ , f ₅ , and f ₃ in Figure 1 constitutes a code; if f ₄ , f ₇ , f ₆ , f ₀ , The arrangement order of f ₁ , f ₂ , f ₃ and f ₅ constitutes another sensor. According to the orthogonal coding theory, when the device responds to the autocorrelation operation, it can have a high correlation peak (theoretically, the surface acoustic wave sensor with N-bit orthogonal frequency coding can process the echo signal by compressing the pulse, which can form N ² times the processing gain, combined with the processing gain of up and down chirp 50, so the wireless range of the sensor can be greatly improved under the same transmission power and receiving sensitivity). However, when two devices with different codes perform cross-correlation calculations, there are very low cross-correlation peaks. The present invention studies and simulates and selects those codes with very low cross-correlation peaks to form a sensor array. Even if these sensors respond to the query signal of the reader at the same time, the echoes are mixed together in the time domain, and they can still be multiplexed by code division. method to distinguish.

It can also be seen in Fig. 1 that an equal fixed time delay τ _D (protection filling) is added between each code chip. Adding this protection filling can ensure that the reflections of each sub-frequency signal between the chips on the SAW sensor will not cause mutual interference. Even if each chip is affected by temperature and the reflection frequency shifts, this time slot can also be in The time domain space forms a partition for the superposition and mutual influence of different frequency signals, and suppresses the interference between sub-frequency.

The multi-sensor detection and recognition, frequency offset estimation and temperature detection based on adaptive matched filtering are described below.

In order to realize the recognition of multiple surface acoustic wave sensors and improve the recognition rate of codes in complex electromagnetic environments, it is necessary to reduce the distance between coded signals for the method of adopting correlation operations in echo signal processing to improve signal processing gain and identification methods. The cross-correlation of each sub-frequency chip needs to be optimized. The possible permutation methods can refer to random codes, precoding based on the largest carrier-to-interference ratio, or Turbo code coding, all of which can reduce intersymbol interference and ensure the improvement of signal processing gain. The above method is also the multiple access principle of code division multiplexing. However, when the distance between multiple sensors and readers is not equal, the power and noise level of the echo signals of each sensor are not equal. Effectively separate out the responses of each sensor in case of aliasing with each other.

The present invention makes each sensor in the surface acoustic wave sensor array code the first chip sub-frequency differently, and the arrangement of the next n-1 frequencies adopts random code, precoding based on the largest carrier-to-interference ratio, or Turbo code coding. The added time slot when solving inter-symbol interference on the sensor substrate also plays a role in sensor identification. If the delay τ _D is greater than the sum of the propagation time of the modulated signal and the echo signal in the channel after the sensor response, such as a spherical space with a radius of 30 meters, the delay is less than 200ns, then the delay can guarantee reading When the multi-sensor echo signal is received by the sensor, the second encoded signal echoed by any sensor will not enter the first encoded signal time gap in the time domain space. As shown in Figure 3, f(t) is the superposition of all sensor response signals in time domain, g[(f-△f _i ),(t-τ _i ),s _i ] is the adaptive matched filter function, and is the frequency offset Shift, time delay, function of power matching coefficient, the best matching coefficient (△f _M ,τ _M ,s _M ) is the matching coefficient value corresponding to the maximum correlation peak. In the first (τ _c +τ _D ) time slot of the demodulated echo signal, signals with different frequency components correspond to different sensors. In this way, several sensor information contained in the aliased signal and the codes of these several sensors can be preliminarily identified according to the first coded signal. According to the evaluation of the power spectrum of each echo signal, the invention performs power equalization on different coded sensors. At this time, the accuracy of the frequency offset of each sub-frequency is not high and cannot be used for temperature detection, but it can greatly reduce the temperature search range of the subsequent matched filtering process and improve the search efficiency.

Then, according to the method shown in Figure 3, adaptive matched filtering can be carried out successively, when the autocorrelation When the calculation correlation peak reaches the maximum value, the temperature value corresponding to the coded sensor can be determined. Then replace another code existing in the array echo signal and search according to Fig. 3 again. It should be noted that the generated matching signal g(f,s,t) seems to be a two-dimensional signal, but the two independent variables are only functions of temperature, and the respective values can be determined according to the searched temperature . Therefore, the entire search speed can be guaranteed.

The optimized response of the sensor is described below.

In order to ensure the low-loss representation of the orthogonal frequency code on the SAW sensor, the present invention focuses on the frequency response characteristics of the interdigital transducer, the transduction efficiency, and the reflection characteristics and frequency response characteristics of the reflection grid, and optimizes the design of its parameters. Because the metallization thickness of the reflective grids with orthogonal frequency encoding is the same, but the number of reflective grid cycles and the number of reflective electrodes vary greatly, it can be reflected according to different orientations on the lithium niobate substrate, transducers and open circuit, short circuit, and floating finger strips. Under the fundamental frequency and the second harmonic frequency of the grid: the number of fingers, the metallization thickness, the metallization rate and the floating finger topological weighting, position weighting and reflection, the amplitude and phase variation of the transmission coefficient, calculate the number of different fingers, The reflection coefficient and transmission coefficient of the reflective grid under the conditions of metallization thickness and metallization rate. Obtain its regularity to ensure the design of SAW sensors with the same reflection coefficient of each orthogonal frequency component. Using the temperature coefficient described by Lagrangian and bringing in the Green's function, the reflection grating topology with the lowest temperature change slope for the reflection characteristics of each orthogonal frequency is optimized to reduce the influence of temperature on the reflectivity and ensure that the reading distance of the sensor does not increase with temperature and decreased significantly.

In terms of sensor structure, issues such as sensor installation, sensor accuracy and dynamics, elimination of installation stress, and interfering factors such as reader crystal oscillator temperature drift should be considered comprehensively. Fig. 4 is a temperature detection sensor system for transmission lines adopted by the present invention. As shown in Figure 4, the installation position of the sensor can be in good contact with the wire core through the metal, and at the same time, it is separated from the shell metal by the heat insulating material to ensure that the temperature can well follow the change of the core wire temperature, and at the same time it will not be caused by Heat dissipation from the housing metal affects measurement accuracy. The microstrip antenna and the shell plate are separated by insulating material and fixed by screws. Use tools such as finite element software to optimize the sensor structure size and the heat capacity and heat conduction structure of the package. Improve sensor dynamics indicators. The package and leads of the sensor are important factors affecting the stability of the sensor. Since SAW is very sensitive to mass loading, factors such as dust, oil stains, and moisture may completely disable the sensor. How to ensure that the surface of the substrate is completely isolated from the outside world through reasonable packaging, and ensure that the measured object can be efficiently loaded on the substrate after the sensor is installed, so as to achieve mechanical firmness, vibration resistance, impact resistance, and avoid thermal stress and package parasitics. The influence of components and high-frequency surface waves is a problem that must be considered and solved when packaging surface wave sensors.

In terms of antenna design, the form of microstrip line antenna is adopted. The full-wave simulation software Ansoft HFSS is used for modeling, and the parameters such as reflection coefficient, gain, pattern and impedance curve of the antenna are simulated and calculated. The correct design of the feed system is very important to improve the antenna radiation and reception efficiency. The impedance of the surface acoustic wave device itself and the impedance of the transmitting antenna can be matched through the microstrip feeder network structure. According to the impedance characteristic curve of the antenna, the microstrip balun feeder is designed so that the impedance of the antenna gradually changes to 50Ω in the design frequency band. The frequency band of the antenna is preliminarily selected at 890MHz-940MHz with a center frequency of 915MHz according to the characteristics of the electromagnetic interference signal of the electric equipment monitoring site.

According to the invention, the interference-free synchronous reading of 8-10 sensors within 30 meters is realized, the temperature detection range is -50°C to +150°C, and the detection error is within ±1°C. Among them, the 915MHz wireless SAW sensor has a working distance of up to 5 meters. By reducing the reflection loss of the sensor by 12-13dB, the up and down linear frequency modulation brings a processing gain of 50 times the code division multiplexing demodulation processing gain of 64. The two items are equivalent to 30dB. Therefore, it is possible to increase the operating distance of the sensor to 30 meters.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (3)

1. the temperature detection sensor system of a transmission line-oriented, it is characterised in that including: power transmission line, screw, Microstrip antenna, insulating barrier, metal heat-conducting portion, insulation part and multiple sensor；

Described sensor, including: unidirectional interdigital transducer, frequency orthogonal reflecting grating chip set；

Described frequency orthogonal reflecting grating chip set, including: n the chip being arranged in order；

Described n chip constitutes a kind of sensor coding；

Each chip is made up of the electrode in a kind of cycle, forms the reflection to a positive jiao zi frequency；

The sub-frequency formed between described n chip is mutually orthogonal；

The time domain length of each chip reflected signal keeps consistent, meets orthogonality condition；

The sensor being arranged in the metal shell of power transmission line by metal heat-conducting portion connect power transmission line core, and by every Hot portion connects the metal shell of power transmission line；Microstrip antenna is connected by screw the outside of the metal shell at power transmission line, micro-strip Insulating barrier it is provided with between antenna and the metal shell of power transmission line；

In each frequency orthogonal reflecting grating chip set, between adjacent chip, it is respectively provided with an equal fixed delay τ_DFilling as protection, to cut off the superposition of different frequency signals with the formation that influences each other at time domain space, suppression is each Interference between sub-frequency；

Described sensor is the sensor after optimizing as follows:

-combine finite element tool by Green's function, optimize SAW sensor transducer and reflecting grating structure, reduce and insert Loss, particularly as follows: according to different orientation, transducer and open circuit, short circuit, floating finger formula reflecting grating on lithium niobate substrate Under fundamental frequency and secondary harmonics: finger number, metallization thickness, degree of metalization and floating finger topological weighting, position weighting With reflection, the amplitude of transmission coefficient and Phase Changing, calculate different finger number, metallization thickness, degree of metalization bar The reflectance factor of reflecting grating and transmission coefficient under part；Utilize it regular, design each quadrature frequency components reflectance factor phase Same SAW sensor；Utilize Lagrangian describe under temperature coefficient, bring Green's function into, optimization to each just Hand over the reflecting grating topological structure that the temperature change slope of frequency hop characteristic is minimum, reduce the temperature impact on reflectivity, protect Card sensor reading distance is along with temperature raises and is remarkably decreased.

The temperature detection sensor system of transmission line-oriented the most according to claim 1, it is characterised in that no The sensor coding that frequency orthogonal reflecting grating chip set contained by same sensor is constituted is different.

The temperature detection sensor system of transmission line-oriented the most according to claim 2, it is characterised in that In the sensor array that multiple sensors are constituted, the sub-frequency that the first chip that each sensor coding is corresponding is formed is each not Identical, and the arrangement of the sub-frequency of n-1 chip formation below uses random code, based on maximum the prelisting of Carrier interference ratio Code or Turbo code coding.