阅读说明：本技术 一种高压输电线网的覆冰状态监测方法 (Icing state monitoring method for high-voltage transmission line network ) 是由 郑喆轩 项勇 杨华东 水彪 黎单驰 张心贲 于 2020-12-17 设计创作，主要内容包括：本发明属于分析及测量控制技术领域,公开了一种高压输电线网的覆冰状态监测方法,获取OPGW高压输电线缆的环境温度、布里渊频移曲线,解调布里渊频移曲线得到OPGW高压输电线缆中的光纤温度信息、光纤应力应变信息,根据环境温度的变化率、光纤温度的变化率,解调获得OPGW高压输电线缆的覆冰厚度,结合阈值判断是否符合报警条件、开启融雪程序。本发明有效解决了长距离OPGW高压输电线缆的覆冰状态难以有效、可靠、经济地监测的难题。(The invention belongs to the technical field of analysis and measurement control, and discloses an icing state monitoring method of a high-voltage transmission line network. The invention effectively solves the problem that the icing state of the long-distance OPGW high-voltage transmission cable is difficult to effectively, reliably and economically monitor.)

1. A method for monitoring the icing state of a high-voltage transmission line network is characterized by comprising the following steps:

step 1, obtaining the environmental temperature of an OPGW high-voltage transmission cable;

step 2, obtaining a Brillouin frequency shift curve of the OPGW high-voltage power transmission cable;

step 3, demodulating the Brillouin frequency shift curve to obtain optical fiber temperature information and optical fiber stress strain information in the OPGW high-voltage power transmission cable;

step 4, judging whether the optical fiber temperature is lower than the freezing point or not according to the optical fiber temperature information; if the temperature of the optical fiber is not lower than the freezing point, no alarm is needed, and the step 1 is returned; if the temperature of the optical fiber is lower than the freezing point, further judging the change trend of the Brillouin frequency shift along with time;

if the Brillouin frequency shift is reduced or unchanged along with the time, entering a step 5; if the Brillouin frequency shift is increased along with time, further judging whether the environment temperature meets a preset first alarm condition;

if the environment temperature is lower than the freezing point and the environment temperature is reduced along with time, the first alarm condition is considered to be met, an alarm signal is sent out, a snow melting program is started, and the step 1 is returned; otherwise, the first alarm condition is considered not to be met, the alarm is not needed, and the step returns to the step 4;

step 5, demodulating and obtaining the ice coating thickness of the OPGW high-voltage power transmission cable according to the change rate of the environment temperature and the change rate of the optical fiber temperature, and entering step 6;

step 6, judging whether the icing thickness meets a preset second alarm condition or a preset third alarm condition;

if the thickness of the ice coating is larger than the thickness threshold value, the second alarm condition is considered to be met, an alarm signal is sent out, a snow melting program is started, and the step 1 is returned; otherwise, the third alarm condition is considered to be met, an alarm signal is sent out, and the step 1 is returned to.

2. The method according to claim 1, wherein said step 4, after said first alarm condition is considered to be met and before said alarm signal is issued, further comprises: and correcting the optical fiber stress-strain information by combining the environmental temperature to obtain and display the corrected optical fiber stress-strain information.

3. The method according to claim 1, wherein in step 4, if the ambient temperature is below the freezing point and the ambient temperature decreases with time, the stress on the optical fiber at that time is determined to be higher than 40% of the rated breaking force, and it is determined that the brillouin frequency shift increase with time is caused by an increase in the stress on the optical fiber in the OPGW high-voltage transmission cable, and it is determined that the first alarm condition is met.

4. The method according to claim 1, wherein in step 5, the specific implementation manner of obtaining the ice coating thickness of the OPGW high-voltage transmission cable by demodulation according to the change rate of the ambient temperature and the change rate of the fiber temperature is as follows:

calculating to obtain the corresponding relation among the change rate of the environment temperature, the change rate of the optical fiber temperature and the ice coating thickness by adopting a numerical simulation method; and demodulating to obtain the ice coating thickness of the OPGW high-voltage power transmission cable by utilizing the corresponding relation.

5. The method according to claim 4, wherein said step 5, before demodulating the thickness of the ice coating, further comprises: and calibrating the corresponding relation through an indoor icing and freezing rain laboratory.

6. The method according to claim 4, characterized in that in step 5, the numerical simulation method uses a finite element method.

7. The method according to claim 6, wherein in step 5, the correspondence is expressed as:

wherein the content of the first and second substances,which represents the rate of change of the ambient temperature,representing the rate of change of the temperature of the fiber, b (t, x) representing the ice coating thickness of the fiber at a time t, at a distance x from the starting point; m represents a relation function and is calculated by a finite element method.

8. The method according to claim 1, wherein in step 1, the ambient temperature is obtained by a weather station; and in the step 2, acquiring and obtaining the Brillouin frequency shift curve through a BOTDA or BOTDR host.

9. The method according to claim 1, wherein in step 6 the thickness threshold is 50 mm.

Technical Field

The invention relates to the technical field of analysis and measurement control, in particular to a method for monitoring the icing state of a high-voltage transmission line network.

Background

The safety operation of a high-voltage transmission line network is seriously threatened by freezing rain icing due to overload, insulator ice flashover, ice shedding, tower falling and the like. Because the high-voltage transmission line network is often arranged in an unmanned area or an area with a severe environment, the traditional manual inspection method is difficult to effectively observe the whole section of the high-voltage transmission line in real time. The monitoring means of carrying the camera by the unmanned aerial vehicle and matching with the machine vision algorithm is limited by the single non-cruising flight distance of the unmanned aerial vehicle of several kilometers. Consider that: on one hand, the charging efficiency of the existing unmanned aerial vehicle-mounted solar charging and other sustainable energy acquisition methods cannot meet the high power requirement of the unmanned aerial vehicle during flying; on the other hand, the unmanned aerial vehicle parking apron with the solar charging piles or other sustainable energy acquisition devices is built every several kilometers, and economic feasibility is not achieved due to the high manufacturing cost, high maintenance cost and the like. Therefore, a highly efficient, reliable and economical ice coating state monitoring method for a high-voltage transmission line network serving a long distance is in urgent need to be solved.

BOTDR (Brillouin optical time domain reflectometry) and BOTDA (Brillouin optical time domain analysis) technologies are used as distributed optical fiber sensing technologies, and the BOTDR and BOTDA distributed optical fiber sensing technology has the advantages that distributed monitoring, long-distance monitoring and electromagnetic interference resistance can be achieved, monitoring is not limited by terrain conditions, and the like. The traditional BOTDA or BOTDR technology can demodulate the temperature information or the stress strain information of the optical fiber to be measured through monitoring the BFS (Brillouin frequency shift). For an OPGW (optical fiber composite overhead ground wire) high-voltage transmission cable, in order to minimize the influence of the external environment on optical signals transmitted by communication optical fibers in the cable, an optical fiber redundancy design is adopted when manufacturing the cable. Namely: OPGW cables are loose-jacketed cables, with the length of the optical fiber in the cable being longer than the cable length. Within a certain range, when the OPGW cable is subjected to larger stress due to the increase of the thickness of the ice coating and thus undergoes elongation deformation, the optical fiber in the cable still maintains a relaxed state, and the BFS of the optical fiber does not change significantly. According to the GB/T7424.2-E1 standard, a qualified OPGW cable is required to "no significant strain (0.01% or 100 μ ∈) of the fiber at 40% rated strain-off force (RTS) applied, 0.25% or less (2500 μ ∈) of fiber strain at 60% RTS, and 0.05dB or less of fiber additional attenuation". The measurement accuracy of stress strain which can be achieved by the existing BOTDA technology is several to tens of mu epsilon, so that the value of RTS <40 percent, namely the value of ice coating thickness less than 50mm, is difficult to effectively measure by only a method for measuring the stress strain. Namely: in the traditional demodulation algorithm which is difficult to pass through the BOTDA or the BOTDR, stress strain suffered by the optical fiber is demodulated through the BFS curve, and then icing information of the OPGW cable is obtained. On the other hand, the temperature value is not directly related to the icing state of the OPGW high-voltage transmission cable. Such as: when the temperature reaches-3 ℃, the OPGW cable may already be covered with a very thick ice. However, the OPGW cable may also not be iced when the temperature reaches-10 ℃. Therefore, it is difficult to demodulate the fiber temperature by the BFS curve in the conventional demodulation algorithm of the BOTDA or the BOTDR, and further obtain the icing information of the OPGW cable.

Disclosure of Invention

The invention provides a method for monitoring the icing state of a high-voltage transmission line network, and solves the problem that the icing state of a medium-and-long-distance OPGW high-voltage transmission cable is difficult to effectively, reliably and economically monitor.

The invention provides a method for monitoring the icing state of a high-voltage transmission line network, which comprises the following steps:

step 1, obtaining the environmental temperature of an OPGW high-voltage transmission cable;

step 2, obtaining a Brillouin frequency shift curve of the OPGW high-voltage power transmission cable;

step 3, demodulating the Brillouin frequency shift curve to obtain optical fiber temperature information and optical fiber stress strain information in the OPGW high-voltage power transmission cable;

step 4, judging whether the optical fiber temperature is lower than the freezing point or not according to the optical fiber temperature information; if the temperature of the optical fiber is not lower than the freezing point, no alarm is needed, and the step 1 is returned; if the temperature of the optical fiber is lower than the freezing point, further judging the change trend of the Brillouin frequency shift along with time;

if the Brillouin frequency shift is reduced or unchanged along with the time, entering a step 5; if the Brillouin frequency shift is increased along with time, further judging whether the environment temperature meets a preset first alarm condition;

if the environment temperature is lower than the freezing point and the environment temperature is reduced along with time, the first alarm condition is considered to be met, an alarm signal is sent out, a snow melting program is started, and the step 1 is returned; otherwise, the first alarm condition is considered not to be met, the alarm is not needed, and the step returns to the step 4;

step 5, demodulating and obtaining the ice coating thickness of the OPGW high-voltage power transmission cable according to the change rate of the environment temperature and the change rate of the optical fiber temperature, and entering step 6;

step 6, judging whether the icing thickness meets a preset second alarm condition or a preset third alarm condition;

if the thickness of the ice coating is larger than the thickness threshold value, the second alarm condition is considered to be met, an alarm signal is sent out, a snow melting program is started, and the step 1 is returned; otherwise, the third alarm condition is considered to be met, an alarm signal is sent out, and the step 1 is returned to.

Preferably, in the step 4, after the first alarm condition is considered to be met and before the alarm signal is issued, the method further includes: and correcting the optical fiber stress-strain information by combining the environmental temperature to obtain and display the corrected optical fiber stress-strain information.

Preferably, in the step 4, if the ambient temperature is lower than the freezing point and the ambient temperature decreases with time, it is determined that the stress applied to the optical fiber at this time is higher than 40% of the rated tensile strength, and it is found that the brillouin frequency shift increase with time is caused by an increase in the stress applied to the optical fiber in the OPGW high-voltage power transmission cable, and it is considered that the first alarm condition is met.

Preferably, in the step 5, a specific implementation manner of obtaining the ice thickness of the OPGW high-voltage power transmission cable by demodulation according to the change rate of the environment temperature and the change rate of the optical fiber temperature is as follows:

calculating to obtain the corresponding relation among the change rate of the environment temperature, the change rate of the optical fiber temperature and the ice coating thickness by adopting a numerical simulation method; and demodulating to obtain the ice coating thickness of the OPGW high-voltage power transmission cable by utilizing the corresponding relation.

Preferably, in the step 5, before demodulating the thickness of the ice coating, the method further includes: and calibrating the corresponding relation through an indoor icing and freezing rain laboratory.

Preferably, in the step 5, the numerical simulation method uses a finite element method.

Preferably, in step 5, the correspondence relationship is expressed as:

wherein the content of the first and second substances,which represents the rate of change of the ambient temperature,representing the rate of change of the temperature of the fiber, b (t, x) representing the ice coating thickness of the fiber at a time t, at a distance x from the starting point; m represents a relation function and is calculated by a finite element method.

Preferably, in the step 1, the ambient temperature is obtained through a weather station; and in the step 2, acquiring and obtaining the Brillouin frequency shift curve through a BOTDA or BOTDR host.

Preferably, in step 6, the thickness threshold is 50 mm.

One or more technical schemes provided by the invention at least have the following technical effects or advantages:

the method comprises the steps of obtaining the environment temperature and the Brillouin frequency shift curve of the OPGW high-voltage power transmission cable, demodulating the Brillouin frequency shift curve to obtain optical fiber temperature information and optical fiber stress strain information in the OPGW high-voltage power transmission cable, demodulating the icing thickness of the OPGW high-voltage power transmission cable according to the change rate of the environment temperature and the change rate of the optical fiber temperature, judging whether an alarm condition is met or not by combining a threshold value, and starting a snow melting program. The invention synthesizes meteorological conditions, utilizes the temperature information and the stress strain information of the optical fiber in the OPGW high-voltage transmission cable to demodulate and obtain the icing information of the OPGW high-voltage transmission cable, and effectively solves the problem that the icing state of the long-distance OPGW high-voltage transmission cable is difficult to effectively, reliably and economically monitor. The invention overcomes the problem that the traditional BOTDA or BOTDA technology can only demodulate the temperature value of the optical fiber or the stress strain information through a BFS curve but can not demodulate the icing state information of the OPGW high-voltage transmission cable, and realizes the effective monitoring of the icing state of the long-distance OPGW high-voltage transmission cable. Compared with the traditional distributed optical fiber sensing technology, the invention does not need additional field construction and does not influence the work of a high-voltage transmission line network.

Drawings

Fig. 1 is a schematic working principle flow chart of a method for monitoring an icing state of a high-voltage transmission line network according to an embodiment of the present invention;

fig. 2 is a schematic diagram illustrating a corresponding relationship among a change rate of an ambient temperature, a change rate of an optical fiber temperature, and an ice coating thickness, which are adopted in the method for monitoring an ice coating state of a high-voltage power transmission line network according to the embodiment of the present invention.

Detailed Description

In order to better understand the technical solution, the technical solution will be described in detail with reference to the drawings and the specific embodiments.

The embodiment provides a method for monitoring an icing state of a high-voltage transmission line network, and the method comprises the following steps of:

step 1, obtaining the environmental temperature of the OPGW high-voltage transmission cable.

In particular, said ambient temperature (T) is obtained by a meteorological station_ref)。

And 2, acquiring a Brillouin frequency shift curve (namely a BFS curve) of the OPGW high-voltage power transmission cable.

Specifically, the brillouin frequency shift curve is acquired through a BOTDA or BOTDR host.

Step 3, demodulating the Brillouin frequency shift curve to obtain optical fiber temperature information (T) in the OPGW high-voltage transmission cable_wire) Optical fiber stress strain information (S)_wire)。

The Brillouin frequency shift curve demodulation method can demodulate the Brillouin frequency shift curve by adopting a traditional demodulation algorithm.

Specifically, BFS is α · Δ T + β · Δ ∈, α is a brillouin temperature coefficient, and β is a brillouin stress coefficient. The brillouin temperature coefficient and brillouin stress coefficient may be measured experimentally for a given optical fiber or cable, respectively. For example, for the G652D fiber, BFS corresponds to approximately 20 microstrain or 1 degree Celsius per 20MHz change.

Step 4, judging the optical fiber temperature (T) according to the optical fiber temperature information_wire) Whether below freezing point; if the temperature of the optical fiber is not lower than the freezing point, no alarm is needed, and the step 1 is returned; and if the temperature of the optical fiber is lower than the freezing point, further judging the change trend of the Brillouin frequency shift along with time.

The judgment of the change trend of the Brillouin frequency shift along with the time comprises the following conditions:

(4.1) if the brillouin frequency shift decreases or does not change with time, proceeding to step 5.

Specifically, if the BFS is measured to decrease or not change with time, indicating that the temperature is still decreasing, then the icing information of the OPGW high-voltage power transmission cable is calculated next.

(4.2) if the Brillouin frequency shift is increased along with the time, further judging whether the environment temperature meets a preset first alarm condition.

The judgment of whether the ambient temperature meets the preset first alarm condition comprises the following conditions:

(4.2.1) if the environment temperature is lower than the freezing point and the environment temperature is reduced along with time, determining that the first alarm condition is met, sending an alarm signal (alarm degree: advanced), starting a snow melting program, and returning to the step 1.

Specifically, if the ambient temperature is lower than the freezing point and the ambient temperature decreases with time, it is determined that the stress applied to the optical fiber at this time is higher than 40% of the rated tensile strength, it is found that the increase in the brillouin frequency shift with time is caused by the increase in the stress applied to the optical fiber in the OPGW high-voltage transmission cable, and it is considered that the first alarm condition is met.

(4.2.2) otherwise, the first alarm condition is not considered to be met, no alarm is needed, and the step returns to the step 4.

Specifically, if the measured ambient temperature increases with time, it indicates that the increase in BFS is caused by an increase in ambient temperature, and no alarm is required.

In a preferred embodiment, after the first alarm condition is considered to be met and before the alarm signal is issued, the method further comprises: and correcting the optical fiber stress-strain information (namely correcting the influence of temperature in BFS curve change) by combining the environmental temperature to obtain and display the corrected optical fiber stress-strain information.

And 5: and demodulating to obtain the ice coating thickness of the OPGW high-voltage transmission cable according to the change rate of the environment temperature and the change rate of the optical fiber temperature, and entering the step 6.

Specifically, the specific implementation manner of obtaining the ice coating thickness of the OPGW high-voltage transmission cable by demodulation according to the change rate of the environmental temperature and the change rate of the optical fiber temperature is as follows: calculating to obtain the corresponding relation among the change rate of the environment temperature, the change rate of the optical fiber temperature and the ice coating thickness by adopting a numerical simulation method; and demodulating to obtain the ice coating thickness of the OPGW high-voltage power transmission cable by utilizing the corresponding relation.

The numerical simulation method may employ a finite element method. The correspondence is expressed as:

wherein the content of the first and second substances,which represents the rate of change of the ambient temperature,representing the rate of change of the temperature of the fiber, b (t, x) representing the ice coating thickness of the fiber at a time t, at a distance x from the starting point; m represents a relation function calculated by a finite element method, as shown in fig. 2.

In a preferred embodiment, before demodulating the thickness of the ice coating, the method further comprises: and calibrating the corresponding relation through an indoor icing and freezing rain laboratory so as to improve the accuracy of the data.

The principle of the step 5 is as follows: the specific heat capacity of the OPGW high-voltage power transmission cable increases along with the increase of the thickness of the ice coating, namely when the change rate of the ambient temperature is constant, the temperature change speed of the optical fiber measured by the BOTDA or the BOTDA decreases along with the increase of the thickness of the ice coating.

Step 6: and judging whether the icing thickness (H _ ice) meets a preset second alarm condition or a preset third alarm condition. If the thickness of the ice coating is larger than the thickness threshold value, the second alarm condition is considered to be met, an alarm signal (alarm degree: advanced) is sent out, a snow melting program is started, and the step 1 is returned; otherwise, the third alarm condition is considered to be met, an alarm signal (alarm degree: middle level) is sent out, and the step 1 is returned to.

For example, the OPGW is about 50mm iced when it is 40% stressed, and the thickness threshold is set to 50 mm.

The method for monitoring the icing state of the high-voltage transmission line network provided by the embodiment of the invention at least comprises the following technical effects:

1. the monitoring distance is long: the longest monitoring distance of the invention to the icing state of the OPGW high-voltage transmission cable reaches hundred kilometers magnitude;

2. the positioning precision is high: the invention can realize the space positioning of the repeated ice-covered area in the meter level;

3. distributed monitoring: the invention can realize the distributed monitoring of the icing state of the OPGW high-voltage transmission cable;

4. not limited to terrain and environment: the applicable environment of the invention comprises unmanned areas, deserts, tropical rain forests, low-pressure and low-oxygen environments and other environments;

5. anti-electromagnetic interference: the sensing unit does not contain an electrical element and cannot be influenced by electromagnetic interference;

6. the demodulation precision is improved through multi-parameter monitoring: the invention can monitor the temperature and stress strain of the OPGW high-voltage transmission cable in real time and demodulate the icing information by an algorithm.

Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.