CN110749304A - Transformer substation ground settlement monitoring device and method based on weak grating - Google Patents
Transformer substation ground settlement monitoring device and method based on weak grating Download PDFInfo
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Abstract
The device comprises an ultra-weak grating strain optical cable, a weak grating demodulation module and a data processing and communication terminal; the ultra-weak grating strain optical cable is connected with a weak grating demodulation module, and the weak grating demodulation module is connected with a data processing and communication terminal; the ultra-weak grating strain optical cable is used for transmission of optical signals and induction of strain; the weak grating demodulation module is used for demodulating the wavelength variation reflected by the ultra-weak grating; and the data processing and communication terminal is used for acquiring the ground settlement information of the transformer substation after the wavelength data is processed. The invention overcomes the defects of the existing transformer substation ground settlement monitoring equipment in terms of measurement density, measurement precision and real-time performance, and has the advantages of distributed type, high precision, quick response and the like; has important application value in the fields of transformer substation settlement and environmental protection.
Description
Technical Field
The invention relates to the technical field of building settlement monitoring, in particular to a transformer substation ground settlement monitoring device and method based on weak gratings.
Background
The main technical parameters of traditional building settlement monitoring are measured by using a traditional instrument to the site manually and periodically, and are restricted by various factors such as manpower, weather, site and the like, so that the workload is huge, settlement data cannot be monitored in time, and meanwhile, certain human errors exist in manual monitoring. The main settlement monitoring methods in the prior art include: simple visual measurement method, settlement calculation method and deformation conversion method. The existing settlement measuring device directly measures the relative displacement between the fixed rod mark and the settlement building, thereby obtaining the foundation settlement value. In the process of treating the underwater riprap and ballast foundation, the fixing rod is likely to be deformed by the impact of ballast, and the accuracy of the measurement result can be directly influenced. Moreover, the monitoring method is very heavy in workload, but the measured data amount is relatively small, the monitoring time is long, and the monitoring method is easily influenced by environmental factors, so that the measuring accuracy is poor. For example: at present, the traditional method of adding a level gauge to a fixed observation point is mostly adopted for settlement observation in the building industry, the observation point needs to be pre-buried in the construction process, the equipment requirement is not high, the settlement data is measured manually, the settlement data cannot be accurately and continuously obtained, and the accuracy rate of the observation data is relatively low. The conventional observation methods are therefore clearly not suitable for the rapidly growing building construction needs.
When a transformer substation is arranged in a place where a collapse possible area exists, if the settlement data of a transformer substation building cannot be known in time, a huge risk is formed for safe operation of the transformer substation. A substation is an important component of a power grid, and functions to transform voltage, receive and distribute electric energy, control the flow of electric power, and regulate voltage in an electric power system. Buildings in substations are power infrastructure for ensuring the safety of power grids, and since most substations are built in remote areas, geological conditions and climatic conditions in the areas often cause the foundation of the substations to sink. The safety problem of the foundation building of the transformer substation is increasingly prominent during construction and later operation. At present, a level monitoring method is mainly adopted for monitoring the foundation settlement of the transformer substation. The method is to judge the settlement amount of the foundation by manually and periodically inspecting the settlement pile heads arranged at the on-site settlement monitoring points and observing the change between each settlement observation point and a reference point by using a precision level gauge. However, the monitoring method is very heavy in workload, but relatively small in measured data amount, long in monitoring time, and easily affected by environmental factors, so that the accuracy of judgment is poor.
The optical fiber can be used as a transmission channel of an optical signal, can also be used as an induction medium of environmental parameters (such as temperature, stress, vibration and the like), has the advantages of small volume, light weight, easiness in laying, electromagnetic interference resistance and the like, and is widely applied to the sensing field. The optical fiber sensor is used for detecting various physical parameters in engineering based on the unique optical characteristics and sensing characteristics of the optical fiber. Compared with the traditional method, the method has the advantages of higher sensitivity, difficult electromagnetic interference, good insulativity, corrosion resistance, long service life, integration of acquisition and transmission of physical parameter information, simple structure, small volume, light weight, less power consumption and the like. Can be used for measuring physical parameters such as strain, temperature, pressure, displacement and the like.
The existing optical fiber water temperature monitoring equipment can be divided into two categories: distributed optical fiber monitoring devices based on scattering (raman scattering or brillouin scattering) and optical fiber monitoring devices based on high reflectivity gratings (FBGs). The former often has the problems of high false alarm rate, poor positioning accuracy, weak anti-interference capability, complex data demodulation and the like. The high-reflectivity grating with a periodic structure is carved on the optical fiber through a specific technical means, and strain monitoring is realized by utilizing the characteristic that the grating structure is sensitive to environmental parameter change. However, the reflectivity of the common grating is high, the multiplexing number of the gratings is small, the spatial resolution is often limited, in addition, the common grating is mostly coated after peeling and writing, the coating uniformity is poor, the temperature linearity is not good, and the requirement of high-precision temperature monitoring is difficult to meet. The ultra-weak fiber grating is a fiber grating with extremely low reflectivity, the reflectivity of the grating is usually lower than 0.1%, and when a single optical pulse signal is transmitted in an optical fiber, a large number of ultra-weak fiber gratings can be transmitted, and reflected signals are sequentially left. The absolute intensity of these reflected signals, although not large, is sufficient to be collected and detected by existing photodetection devices. Therefore, the weak grating is engraved in one optical fiber at high density to form an ultra-weak optical fiber grating array, so that the density of the effective sensing units can be greatly improved. In addition, the wavelength division multiplexing technology is introduced into the ultra-weak fiber grating, so that the sensing density can be further improved, and a solid physical foundation is provided for carrying out sensing of the strain array.
Disclosure of Invention
The invention provides a transformer substation ground settlement monitoring device and method based on weak gratings, which apply ultra-weak fiber gratings to transformer substation foundation settlement monitoring, overcome the defects of the existing transformer substation ground settlement monitoring equipment in terms of measurement density, measurement precision and real-time performance, and have the advantages of distributed type, high precision, quick response and the like; has important application value in the fields of transformer substation settlement and environmental protection.
The technical scheme adopted by the invention is as follows:
the transformer substation ground settlement monitoring device based on the weak grating comprises an ultra-weak grating strain optical cable, a weak grating demodulation module and a data processing and communication terminal; the ultra-weak grating strain optical cable is connected with a weak grating demodulation module, and the weak grating demodulation module is connected with a data processing and communication terminal;
the ultra-weak grating strain optical cable is used for transmission of optical signals and induction of strain;
the weak grating demodulation module is used for demodulating the wavelength variation reflected by the ultra-weak grating;
the data processing and communication terminal is used for acquiring the ground settlement information of the transformer substation after the wavelength data is processed;
the ultra-weak grating strain optical cable is provided with a plurality of fixed points, and the fixed points are used for being connected with facilities to be monitored by a transformer substation.
The ultra-weak grating strain optical cable comprises an optical fiber core positioned in the center, and an ultra-weak grating array formed by a plurality of ultra-weak grating sensing units which are identical or wavelength division multiplexed and have low reflectivity is engraved on the optical fiber core.
The ultra-weak grating array is inscribed by adopting a non-peeling process, and a coating layer of the ultra-weak grating array is a modified polyacrylate layer or an ultraviolet-transmitting coating layer.
The ultra-weak grating strain optical cable is sequentially wrapped with an armor layer, a braid layer and an outer sheath from an inner layer to an outer layer, the ultra-weak grating array is in a free moving state, and after the ultra-weak grating strain optical cable is exposed out of an optical fiber core through a circular incision, an adhesive is poured in the ultra-weak grating strain optical cable to be cured with the optical fiber core to form a glue joint fixed point; the glue joint fixed point is sleeved with a protective shell.
And the optical fiber core is embedded in the ultra-weak grating strain optical cable, and is fixed with the ultra-weak grating sensing unit of the ultra-weak grating array at equal intervals after the optical fiber core applies pretension.
The weak grating demodulation module adopts narrow-band scanning laser as a light source, the narrow-band scanning laser is incident into a plurality of ultra-weak grating sensing units after electro-optical modulation, a plurality of fixed points correspond to the plurality of ultra-weak grating sensing units one by one, signal light reflected by all the ultra-weak grating sensing units is collected by a high-speed acquisition card, reflected light of non-gratings is filtered by an algorithm, reflected signals of all the ultra-weak grating sensing units are extracted, and the peak wavelength of each ultra-weak grating sensing unit in an ultra-weak grating array is obtained through wavelength fitting.
The weak grating demodulation module, the data processing and communication terminal are all arranged in a central control room of the transformer substation and are connected with a communication network through Ethernet, WIFI or GPS.
The data output port of the weak grating demodulation module is connected with a data processing and communication terminal in a wired or wireless mode; the data processing and communication terminal is connected with the external network and uploads the data to the terminal through the external network.
The device also comprises an installation fixture used for installing and fixing the ultra-weak grating strain optical cable, wherein the installation fixture comprises a plurality of fixing pieces, and each fixing piece is provided with a clamping piece used for fixing a glue joint fixing point.
The transformer substation ground settlement monitoring method based on the weak grating comprises the following steps:
step one, calibrating displacement, strain and wavelength:
calibrating the relation between the reflection wavelength drift amount of the ultra-weak grating strain optical cable and absolute strain and displacement by using an experiment table to obtain a 'strain-displacement-wavelength' calibration curve;
step two, layout of ultra-weak grating strain optical cables:
and carrying out multi-dimensional layout on the ultra-weak grating strain optical cable in a transformer substation: laying in the horizontal direction, laying in the vertical direction and laying in the underground settlement; a facility to be monitored by the transformer substation is fixed with a plurality of fixed points of the ultra-weak grating strain optical cable;
step three, grating positioning:
the weak grating demodulation module emits continuous laser, optical pulses are formed after modulation and are coupled into the ultra-weak grating strain optical cable, and the wavelengths of the continuous laser are sequentially increased according to specified intervals; light pulses with different wavelengths are incident on the ultra-weak grating sensing units with different spatial positions, the time of the light pulses reaching the detector after reflection is different, and the relationship between the grating position and the length is established by combining auxiliary length marks through wavelength and time calculation;
step four, length measurement:
4.1, according to the wavelength information of the grating at different positions obtained in the third step, establishing a calibration file, and storing the calibration file in a data processing and communication terminal;
4.2, resetting the wavelength of the continuous laser, scanning the wavelength again, recording the reflection information of the grating at the corresponding position, obtaining the grating wavelength at the current moment through algorithm fitting, and storing the grating wavelength in a data processing and communication terminal;
4.3, repeating the previous step for n-1 times, storing the peak wavelength data measured each time, and establishing an array;
4.4, carrying out algorithm processing on the data measured for n times to obtain a millisecond-level normalized wavelength value in the current time period;
4.5, an algorithm preset in the data processing and communication terminal inverts the strain distribution of the grating points at different positions according to the current normalized wavelength value and the calibrated length wavelength curve;
step five, cyclic measurement:
and repeating the fourth step to obtain the values of the different depth positions of the settlement strain of the transformer substation at the next moment.
The invention discloses a transformer substation ground settlement monitoring device and method based on weak gratings, which have the following technical effects:
1: overcomes the defects of the prior settlement monitoring equipment in measuring density, measuring precision and real-time property, and has the advantages of distributed type, high precision, quick response and the like
2: due to the ultra-low reflectivity characteristic of the ultra-weak grating array, light pulses can continuously penetrate thousands of ultra-weak grating sensing units and sequentially generate reflected signals, and the spatial resolution of the current time division demodulation technology is 2 meters; in combination with the wavelength division multiplexing technology, within each time division interval, the wavelength of 40 is wavelength division multiplexed again, and the spatial resolution can reach 0.05 meter.
3: easy to lay, the network organization is convenient: the writing technology of the ultra-weak fiber grating is the same as that of the common fiber grating, but the exposure time of a single grating is correspondingly reduced, the technology is mature, and the cost performance of the grating is high.
4: in addition, the settlement monitoring device only needs one set of demodulation equipment for measurement in a large range, and has good cost performance compared with the traditional single high-precision electronic measurement sensor.
Drawings
Fig. 1 is a schematic connection diagram of a transformer substation settlement monitoring system according to the present invention.
Fig. 2 is a schematic structural diagram of the ultra-weak grating strain optical cable of the present invention.
FIG. 3 is a schematic view of an ultra-weak grating strain cable installation fixture of the present invention.
FIG. 4 is a schematic diagram of the ultra-weak grating strain cable test according to the present invention.
FIG. 5 is a graph of the deformation of the fiber optic cable of the present invention versus the change in wavelength.
FIG. 6 is a plot of displacement versus micro-strain calibration for an optical cable in accordance with the present invention.
FIG. 7 is a drawing of the deep portion deformation monitoring cable layout according to the present invention.
Fig. 8 is a schematic view of monitoring vertical displacement of a reference pile and a test pile according to the present invention.
Wherein: 8-ultra-weak grating strain optical cable.
Detailed Description
As shown in fig. 1, the transformer substation ground settlement monitoring device based on the weak grating comprises an ultra-weak grating strain optical cable, a weak grating demodulation module 9 and a data processing and communication terminal 10; the ultra-weak grating strain optical cable is connected with a weak grating demodulation module 9, and the weak grating demodulation module 9 is connected with a data processing and communication terminal 10.
The ultra-weak grating strain optical cable is used for transmission of optical signals and induction of strain;
the weak grating demodulation module 9 is used for demodulating the wavelength variation reflected by the ultra-weak grating;
the data processing and communication terminal 10 is used for obtaining the ground settlement information of the transformer substation after the wavelength data is processed;
the ultra-weak grating strain optical cable is provided with a plurality of fixed points, and the fixed points are used for being connected with facilities to be monitored by a transformer substation.
As shown in fig. 2, the ultra-weak grating strain optical cable includes an optical fiber core 1 located at the center, and an ultra-weak grating array formed by a plurality of identical or wavelength division multiplexing low-reflectivity ultra-weak grating sensing units 7 is inscribed on the optical fiber core 1.
The ultra-weak grating array is inscribed by adopting a non-peeling process, and a coating layer of the ultra-weak grating array is a modified polyacrylate layer or an ultraviolet-transmitting coating layer.
The ultra-weak grating strain optical cable is sequentially wrapped with an armor layer 2, a braid layer 3 and an outer sheath 4 from an inner layer to an outer layer, the ultra-weak grating array is in a free moving state, and after the ultra-weak grating strain optical cable is exposed out of the optical fiber core 1 through a circular cut, an adhesive 6 is poured in the ultra-weak grating strain optical cable and is cured with the optical fiber core 1 to form a glue joint fixed point; the protective shell 5 is sleeved at the glue joint fixed point.
The braided layer 3 is a metal braided layer, and the adhesive 6 is epoxy resin adhesive.
An optical fiber core 1 is embedded in the ultra-weak grating strain optical cable, and the diameter of the optical fiber core 1 is about 0.5 mm-1 mm. After the optical fiber wire core 1 is applied with pretension, the optical fiber wire core and the ultra-weak grating sensing unit 7 of the ultra-weak grating array are fixed at equal intervals, fixed points of the optical fiber wire core have certain intervals, and the interval between adjacent fixed points is 30 cm.
The strain optical cable of ultra-weak grating is a fixed point type strain sensing optical cable, which is a strain sensing optical cable which utilizes the strain generated by the grating receiving external tension or temperature change. The ultra-weak grating array and the armor layer 2 are in a free moving state, and the ultra-weak grating array, the armor layer 2 and the outer sheath 4 are fixed through a certain distance, so that the spatial discontinuous non-uniform segmentation is realized, and the strain measurement result can be used for directly calculating the deformation and the temperature.
The landslide monitoring is considered, the fixed point interval is 2 meters, the outer sheath 4 and the protective shell 5 are wound on the grating after the grating is wound, the outer sheath is composed of a braided layer 3, an armor layer 2 and polyether elastic TPU, and the cabling process comprises the following steps: the oversheath 4 that constitutes polyether elasticity TPU extrudees through the cable machine evenly scribbles around optical fiber core 1 and weaving layer 3, through the water-cooling, spouts the rectangle mark of 50 millimeters long and 8 millimeters wide according to 2 meters intervals through the ink jet numbering machine, and the cable is black, and the colour of the rectangle mark that spouts is white, makes things convenient for the quick position of finding out the rectangle mark of site operation. After the cable is pulled in, the outer sheath 4 is peeled off by 40 mm, the improved epoxy resin adhesive is filled in the outer sheath, and then two semicircular clips are sleeved on the outer sheath to serve as a protective shell 5.
The weak grating demodulation module 9 adopts narrow-band scanning laser as a light source, the narrow-band scanning laser is incident into the multiple ultra-weak grating sensing units 7 after electro-optical modulation, the multiple fixed points correspond to the multiple ultra-weak grating sensing units 7 one by one, signal light reflected by all the ultra-weak grating sensing units 7 is collected through a high-speed collection card, reflected light of non-gratings is filtered by an algorithm, reflected signals of all the ultra-weak grating sensing units 7 are extracted, and the peak wavelength of each ultra-weak grating sensing unit 7 in an ultra-weak grating array is obtained through wavelength fitting.
The weak grating demodulation module 9 and the data processing and communication terminal 10 are all arranged in a central control room of the transformer substation and are connected with a communication network through Ethernet, WIFI or GPS.
The weak grating demodulation module 9 adopts an RS-HFBGA-04 type demodulation module.
The data processing and communication terminal 10 adopts PWS-2015G-R2 flat panel microprocessor and TR321 series dual-network port industrial router.
The data output port of the weak grating demodulation module 9 is connected with the data processing and communication terminal 10 in a wired or wireless manner; the data processing and communication terminal 10 is connected to an external network and uploads data to the terminal via the external network.
The transformer substation ground settlement monitoring method based on the weak grating comprises the following steps:
step one, calibrating displacement, strain and wavelength:
calibrating the relation between the reflection wavelength drift amount of the ultra-weak grating strain optical cable and absolute strain and displacement by using an experiment table to obtain a 'strain-displacement-wavelength' calibration curve;
step two, layout of ultra-weak grating strain optical cables:
and carrying out multi-dimensional layout on the ultra-weak grating strain optical cable in a transformer substation: laying in the horizontal direction, laying in the vertical direction and laying in the underground settlement; fixing facilities to be monitored by the transformer substation with a plurality of fixed points of the ultra-weak grating strain optical cable;
step three, grating positioning:
the weak grating demodulation module 9 emits continuous laser, forms optical pulses after modulation, couples the optical pulses into the ultra-weak grating strain optical cable, and the wavelengths of the continuous laser are sequentially increased according to specified intervals; light pulses with different wavelengths are incident on the ultra-weak grating sensing unit 7 with different spatial positions, the time of reaching a detector after reflection is different, and the relationship between the grating position and the length is established by wavelength and time calculation and auxiliary length marks;
step four, length measurement:
4.1, according to the wavelength information of the grating at different positions obtained in the third step, establishing a calibration file, and storing the calibration file in the data processing and communication terminal 10;
4.2, resetting the wavelength of the continuous laser, scanning the wavelength again, recording the reflection information of the grating at the corresponding position, obtaining the grating wavelength at the current moment through algorithm fitting, and storing the grating wavelength in the data processing and communication terminal 10;
4.3, repeating the previous step for n-1 times, storing the peak wavelength data measured each time, and establishing an array;
4.4, carrying out algorithm processing on the data measured for n times to obtain a millisecond-level normalized wavelength value in the current time period;
4.5, an algorithm preset in the data processing and communication terminal 10 inverts the strain distribution of the grating points at different positions according to the current normalized wavelength value and the calibrated length wavelength curve;
step five, cyclic measurement:
and repeating the fourth step to obtain the values of the different depth positions of the settlement strain of the transformer substation at the next moment.
As shown in fig. 3, the device further includes an installation fixture 11 for installing and fixing the ultra-weak grating strain optical cable, where the installation fixture 11 includes a plurality of fixing members 11.1, and each fixing member 11.1 is provided with a clamping member 11.2 for fixing a glue joint.
The fixing piece 11.1 adopts angle iron, and the clamping piece 11.2 is a clamp with a screw and used for fixing the angle iron and the fixed-point optical cable together.
As shown in fig. 4, the test diagram of the ultra-weak grating strain optical cable is shown in fig. 4, and fig. 4 includes an adjusting screw 12.1, a fixing nut 12.2, a slider 12.3, a fixing angle iron 12.4, a weak grating demodulation module 9, and a steel plate 12.5.
The glue joint fixed point A of the fixed point type strain sensing optical cable is fixed on the sliding block 12.3, the glue joint fixed point B of the fixed point type strain sensing optical cable is fixed on the fixed angle iron 12.4, and the fixed point type strain sensing optical cable is connected with the weak grating demodulation module 9. After the adjusting screw 12.1 penetrates through the fixing nut 12.2, the end part of the adjusting screw 12.1 is connected and matched with the sliding block 12.3, and the end part of the adjusting screw 12.1 and the sliding block 12.3 can rotate in the sliding block 12.3 and can drive the sliding block 12.3 to horizontally move left and right along the steel plate 12.5.
When the bonding fixed point A strains the optical fiber, the adjusting screw 12.1 drives the sliding block 12.3 to move leftwards, the bonding fixed point A moves leftwards, the change of the wavelength and the strain is recorded after 1mm of movement each time, and the distance between the fixing nut 12.2 and the bonding fixed point A is measured by a caliper. The test results are shown in table 1, the curve of fig. 5 is drawn from table 1, and the test accuracy reaches 99.9% as can be seen from the graph 5.
Table 1 fixed point cable test data table, in table 1, the Ax column is the unit of change in displacement in millimeters.
As can be seen from FIG. 6, the linearity of the calibration curve is very good, and both the linearity and the linearity of the calibration curve reach more than 99.9%. In order to early warn of slow deformation and sudden foundation settlement, a method for monitoring settlement in a deep hole is sampled on site, the condition of a deformation area is measured in advance, and the monitoring scheme is shown in fig. 7.
In fig. 7, a foundation is provided with a reference pile 13.1, and the reference pile 13.1 is formed by pouring concrete into a steel pipe. A supporting steel pipe 13.2 is arranged perpendicular to the reference pile 13.1, one end of a steel wire rope 13.3 is connected with the upper portion of the reference pile 13.1 through a tensioner 13.4, the other end of the steel wire rope 13.3 bypasses a pulley arranged at the top end of the supporting steel pipe 13.2, and the tail end of the other end of the steel wire rope 13.3 is a free end and used for laying an ultra-weak grating strain optical cable.
In fig. 7: "↓" is in the direction of the drilled hole 14, and "↓" is in the direction of the drilled hole 14; 1 #, 2 #, 3 # 4 #, 5 #, 6 # 7 #, 8 # and 9 # each of which indicates a plurality of site fixing.
The optical cable is laid as follows:
① drilling a 200 mm diameter borehole 14 at a selected location with a drill;
② placing the optical cable into the bottom of the hole with 15 m depth by using a weight dropper and a steel pipe for pressurizing when the drill is just lifted;
③, in order to enlarge the measuring range, when laying the optical cables, 1 fixed point optical cable of 2 meters and 1 fixed point optical cable of 10 meters are selected to be laid;
④, monitoring the strain condition of the optical cable through the weak grating demodulation module 9 and the data processing and communication terminal 10;
⑤, backfilling the borehole, namely, during backfilling the borehole 14, calculating to fill clay balls of 20 cm only at the cementing fixed point of the optical cable, and backfilling the rest positions with undisturbed soil, so as to ensure that the cementing fixed point of the optical cable is well coupled with the stratum, wherein during backfilling the borehole 14, the tightness degree of the optical cable needs to be continuously adjusted, so that the strain generated by the optical cable is preferably not more than 500 micro-strain.
Basic principle of settlement monitoring of reference pile 13.1: firstly, drilling a drill hole 14 reaching the bedrock by using a drilling machine, then manufacturing a reference pile 13.1, respectively arranging monitoring optical cables between the reference pile 13.1 and the monitoring pile 15.1, and monitoring the strain change of the optical cables through a weak grating demodulation module 9 and a data processing and communication terminal 10 because the reference pile 13.1 does not generate the settlement change, thereby determining the settlement change of the reference pile 13.1.
In fig. 8, a fixing frame 15.2 is provided on the reference pile 13.1, and an angle iron is used as the fixing frame 15.2. The fixed frame 15.2 is provided with a pulley 15.4 through a connecting rod 15.3, one end of a stainless steel wire 15.5 is hung with a heavy object 15.6, and the heavy object 15.6 adopts a cement pile with the length of 0.5 meter. The other end of the stainless steel wire 15.5 is connected with a steel plate 15.7, the steel plate 15.7 is connected with a monitoring pile 15.1, and a cementing fixed point C of the monitoring optical cable is fixed with the steel plate 15.7 through a clamp. In fig. 8, "↓" indicates the optical cable in, and "↓" indicates the optical cable out.
Manufacturing a reference pile 13.1:
① drilling a hole to bedrock (19 m deep) at a safe position 6 m from the high-pressure equipment by using a drilling machine;
② placing the steel pipe with a diameter of 160 mm into the hole after welding, pouring concrete into the steel pipe, wherein the height of the steel pipe from the ground surface is 3 m.
And (3) laying of monitoring optical cables:
①, according to the monitoring schematic diagram 8, welding the fixed mount 15.2 with the support steel pipe 13.2 of the reference pile 13.1, punching the connecting rod 15.3, fixing the stainless steel pulley 15.4 with a screw, hanging a weight 15.6 on one end of the stainless steel wire, connecting the other end with the steel plate, and connecting the steel plate with the monitoring pile 15.1;
②, fixing the cementing fixed point C of the monitoring optical cable and the steel plate 15.7 of the monitoring pile 15.1 through a metal clamp;
③, fixing the other glue joint fixed point of the monitoring optical cable with the fixed frame 15.2 of the reference pile 13.1 through another metal clamp;
④ the optical cable between the reference pile 13.1 and the monitoring pile 15.1 is protected by PVC pipe, the PVC pipe is fixed with the stainless steel wire 15.5, the PVC pipe is used as protection pipe, and the measurement difference generated by the optical cable sag is avoided.
⑤, under the condition of weak grating demodulation module 9, data processing and monitoring of communication terminal 10, adjusting the tensioner to make the strain generated by the optical cable reach 1/20 of the full range;
⑥, fixing the monitoring optical cables between the other 4 monitoring piles 15.1 and the reference pile 13.1 in sequence.
Claims (10)
1. Transformer substation's ground settlement monitoring devices based on weak grating, its characterized in that: the system comprises an ultra-weak grating strain optical cable, a weak grating demodulation module (9) and a data processing and communication terminal (10); the ultra-weak grating strain optical cable is connected with a weak grating demodulation module (9), and the weak grating demodulation module (9) is connected with a data processing and communication terminal (10);
the ultra-weak grating strain optical cable is used for transmission of optical signals and induction of strain;
the weak grating demodulation module (9) is used for demodulating the wavelength variation reflected by the ultra-weak grating;
the data processing and communication terminal (10) is used for acquiring the ground settlement information of the transformer substation after the wavelength data is processed;
the ultra-weak grating strain optical cable is provided with a plurality of fixed points, and the fixed points are used for being connected with facilities to be monitored by a transformer substation.
2. The weak grating-based substation ground settlement monitoring device of claim 1, wherein: the ultra-weak grating strain optical cable comprises an optical fiber core (1) positioned in the center, wherein an ultra-weak grating array formed by a plurality of identical or wavelength division multiplexing low-reflectivity ultra-weak grating sensing units (7) is inscribed on the optical fiber core (1).
3. The weak grating-based substation ground settlement monitoring device of claim 1, wherein: the ultra-weak grating array is inscribed by adopting a non-peeling process, and a coating layer of the ultra-weak grating array is a modified polyacrylate layer or an ultraviolet-transmitting coating layer.
4. The weak grating-based substation ground settlement monitoring device of claim 1, wherein: the ultra-weak grating strain optical cable is sequentially wrapped with an armor layer (2), a braid layer (3) and an outer sheath (4) from an inner layer to an outer layer, the ultra-weak grating array is in a free moving state, and after the ultra-weak grating strain optical cable is exposed out of the optical fiber core (1) through a circular cut, an adhesive (6) is poured in the ultra-weak grating strain optical cable and is cured with the optical fiber core (1) to form a glue joint fixed point; the glue joint fixed point is sleeved with a protective shell (5).
5. The weak grating-based substation ground settlement monitoring device of claim 1, wherein: the optical fiber core (1) is embedded in the ultra-weak grating strain optical cable, and after the optical fiber core (1) applies pretension, the optical fiber core is fixed with the ultra-weak grating sensing unit (7) of the ultra-weak grating array at equal intervals.
6. The weak grating-based substation ground settlement monitoring device of claim 1, wherein: the weak grating demodulation module (9) adopts narrow-band scanning laser as a light source, the narrow-band scanning laser is incident into the multiple ultra-weak grating sensing units (7) after electro-optical modulation, the multiple fixed points correspond to the multiple ultra-weak grating sensing units (7) one by one, signal light reflected by all the ultra-weak grating sensing units (7) is collected through a high-speed collection card, reflected light of non-gratings is filtered by an algorithm, reflected signals of all the ultra-weak grating sensing units (7) are extracted, and the peak wavelength of each ultra-weak grating sensing unit (7) in the ultra-weak grating array is obtained through wavelength fitting.
7. The weak grating-based substation ground settlement monitoring device of claim 1, wherein: the weak grating demodulation module (9) and the data processing and communication terminal (10) are all arranged in a central control room of the transformer substation and are connected with a communication network through Ethernet, WIFI or GPS.
8. The weak grating-based substation ground settlement monitoring device of claim 1, wherein: the data output port of the weak grating demodulation module (9) is connected with a data processing and communication terminal (10) in a wired or wireless mode; the data processing and communication terminal (10) is connected with an external network and uploads the data to the terminal through the external network.
9. The weak grating-based substation ground settlement monitoring device of claim 1, wherein: the device also comprises an installation fixture (11) used for installing and fixing the ultra-weak grating strain optical cable, wherein the installation fixture (11) comprises a plurality of fixing pieces (11.1), and each fixing piece (11.1) is provided with a clamping piece (11.2) used for fixing a glue joint fixed point.
10. The transformer substation ground settlement monitoring method based on the weak grating is characterized by comprising the following steps of:
step one, calibrating displacement, strain and wavelength:
calibrating the relation between the reflection wavelength drift amount of the ultra-weak grating strain optical cable and absolute strain and displacement by using an experiment table to obtain a 'strain-displacement-wavelength' calibration curve;
step two, layout of ultra-weak grating strain optical cables:
and carrying out multi-dimensional layout on the ultra-weak grating strain optical cable in a transformer substation: laying in the horizontal direction, laying in the vertical direction and laying in the underground settlement; a facility to be monitored by the transformer substation is fixed with a plurality of fixed points of the ultra-weak grating strain optical cable;
step three, grating positioning:
the weak grating demodulation module (9) emits continuous laser, optical pulses are formed after modulation and are coupled into the ultra-weak grating strain optical cable, and the wavelengths of the continuous laser are sequentially increased according to specified intervals; light pulses with different wavelengths are incident on the ultra-weak grating sensing unit (7) with different spatial positions, the time of reaching a detector after reflection is different, and the relationship between the grating position and the length is established by wavelength and time calculation and auxiliary length marks;
step four, length measurement:
4.1, according to the wavelength information of the grating at different positions obtained in the third step, establishing a calibration file, and storing the calibration file in a data processing and communication terminal (10);
4.2, resetting the wavelength of the continuous laser, scanning the wavelength again, recording the reflection information of the grating at the corresponding position, obtaining the grating wavelength at the current moment through algorithm fitting, and storing the grating wavelength in the data processing and communication terminal (10);
4.3, repeating the previous step for n-1 times, storing the peak wavelength data measured each time, and establishing an array;
4.4, carrying out algorithm processing on the data measured for n times to obtain a millisecond-level normalized wavelength value in the current time period;
4.5, an algorithm preset in the data processing and communication terminal (10) inverts the strain distribution of the grating points at different positions according to the current normalized wavelength value and the calibrated length wavelength curve;
step five, cyclic measurement:
and repeating the fourth step to obtain the values of the different depth positions of the settlement strain of the transformer substation at the next moment.
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