CN108020710B - Oil-gas pipeline low-frequency stray current open-type magnetic measurement device and method - Google Patents
Oil-gas pipeline low-frequency stray current open-type magnetic measurement device and method Download PDFInfo
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Abstract
The invention relates to an oil and gas pipeline low-frequency stray current open-type magnetic measurement device and a method, wherein the oil and gas pipeline low-frequency stray current open-type magnetic measurement device is composed of a magnetic ring formed by stacking a plurality of groups of strip permalloy magnetic conductive strips, at least 3 magnetic Hall elements and at least 3 signal conditioning modules. According to the technical scheme, the open-loop magnetic Hall current measuring principle is adopted to install the oil-gas pipeline low-frequency stray current open-type magnetic measuring device, the oil-gas pipeline low-frequency stray current is measured, and the accurate oil-gas pipeline low-frequency stray current value can be obtained.
Description
Technical Field
The invention relates to the technical field of natural disaster prevention of buried pipelines, in particular to an open type magnetic measurement device and method for low-frequency stray current of an oil and gas pipeline.
Background
At present, oil and gas long-distance pipelines built in China are all over the country and most of the oil and gas long-distance pipelines are buried underground. When a magnetic storm occurs, an induced current, namely, a Geomagnetically Induced Current (GIC), is generated in a distributed closed conductor loop formed by the buried metal pipeline and its coating and the earth. Meanwhile, high-speed rail, direct current transmission grounding electrode, high voltage alternating current transmission system and the like near the pipeline can also generate current to enter the pipeline. The intrusion of these low frequency stray currents interferes with the pipe-to-ground potential (PSP) measurements, causing the Cathodic Protection (CP) devices to run away or even react, causing increased corrosion of the pipeline, thereby reducing the useful life of the pipeline. To investigate the effect of these electromagnetic interferences on the pipe, it is necessary to measure low frequency stray currents in the pipe.
At present, the buried pipeline detection and buried depth measurement research is more at home and abroad, and more detection equipment is available in the market. However, the current measuring equipment in the oil and gas pipeline is few, and the following methods are mainly used at present:
firstly, a DSTL model is established for a pipeline, geomagnetic table data near the pipeline and relevant parameters of the pipeline are input, and finally, the pipeline ground potential and the pipeline current are calculated. The Chinese patent application 201510579331.X of the invention provides a method for calculating GIC and PSP of a buried oil and gas pipeline affected by geomagnetic storm, and provides a new pipeline model LZS-DSTL, which inputs geomagnetic storm data, related environmental parameters and pipeline parameters near the pipeline to further calculate GIC and PSP. The method can only calculate the geomagnetic induction current in the oil and gas pipeline, and does not include the current caused by equipment such as a high-speed rail, a direct-current power transmission grounding electrode, a high-voltage alternating-current power transmission system and the like.
Secondly, standard pipe-to-ground potential (PSP) testing, closely spaced potential testing technology (CIPS), direct current potential gradient method (DCVG), Pearson (Person) method, variable frequency selection method, direct current-to-potential method and the like. The invention patent 200810119164.0 in China proposes a device and method for measuring the geomagnetic induction current and the pipe-to-ground potential of a buried pipeline, wherein a GPS synchronous recording device is arranged on a test pile on the pipeline, the instantaneous pipe-to-ground potential of each measuring point is recorded, and the electric field intensity of the earth surface and the pipeline parameters are calculated. However, when the pipe is operated for many years, the resistance of the pipe changes due to corrosion, and thus the measured pipe current also changes with the operating time of the pipe. This is an undesirable phenomenon for pipe current measurement.
And thirdly, detecting the induced current of the buried pipeline in a non-contact mode under the non-excavation state, namely measuring by a magnetic method. A stray current detector SCM produced by British Raddick is mainly used for detecting corrosion points of a pipeline, and the inflow point and the outflow point of current are positioned, so that the pipeline current can only be roughly calculated, and the precision is poor. The invention patent 201110097516.9 in China provides a method for measuring buried depth of a buried pipeline, the direction of stray current and the geomagnetic azimuth angle, which monitors the magnetic field intensity above the buried pipeline in real time through 4 fluxgate sensors arranged in the straight line direction on the ground plane, and calculates the buried depth, the current direction and the magnitude of the pipeline. The method has the advantages of simple measurement method, no need of additional signal source, real-time measurement data, capability of arbitrarily installing monitoring points and the like, but has lower precision of the measurement data and larger error.
The Hall current sensor based on the Hall effect can accurately measure the current flowing in the conductor, but the existing mature Hall sensor is mainly used for measuring the current of a 50 or 60 Hz power frequency power supply circuit of an electric power system, and the current of the conductor with the large diameter of an oil-gas pipeline can be measured by the method. Firstly, when current measurement is carried out on the existing oil and gas pipeline, excavation needs to be carried out on site, soil around the pipeline is taken out, then the pipeline is sleeved with the sensor open type magnetic ring, and then current information is taken out from a coil of the magnetic ring. The measurement accuracy requirement is difficult to achieve for very low frequency direct current.
In summary, the following outstanding problems exist in measuring the stray current at very low frequencies of buried oil and gas pipelines:
firstly, it is feasible to adopt the principle or method of hall current sensor for power frequency or higher frequency current signal, practice shows that it is difficult to achieve the measurement accuracy requirement for very low frequency direct current.
Secondly, in order to ensure the measurement accuracy, when the sensor magnetic ring is installed, the axis of the pipeline and the circle center of the sensor magnetic ring should be overlapped as much as possible, and for a large-diameter conductor such as an actual oil and gas pipeline on site, the installation accuracy requirement is difficult to realize, so that the measurement error cannot meet the industrial site requirement.
Third, at present, it is extremely difficult to realize high-precision current measurement for a general open-type magnetic ring because of a small contact area. In summary, the measuring device and the method in the prior art cannot accurately measure the low-frequency stray current of the oil-gas pipeline.
Disclosure of Invention
In order to solve the technical problem, the invention provides an oil-gas pipeline low-frequency stray current open-type magnetic measurement device and method, which comprises the following steps: firstly, measuring the pipeline current by taking a permalloy magnetic strip as a magnetic ring based on a method for directly measuring magnetism generated by the pipeline current, and ensuring the measurement precision of low-frequency direct current; secondly, the special magnetic ring structure design ensures the magnetic measurement precision of the open type magnetic ring; thirdly, the sensor is combined and positioned to eliminate the error of misalignment between the axis of the pipeline and the circle center of the sensor magnetic ring. Like this, just can effectual solution prior art measure the defect and not enough to oil gas pipeline low frequency stray current.
In order to achieve the above object, the present invention adopts the following technical solutions.
The invention discloses an oil-gas pipeline low-frequency stray current open-type magnetic measuring device which is used for accurately measuring the oil-gas pipeline low-frequency stray current.
The invention relates to a low-frequency stray current open-type magnetic measuring device for an oil and gas pipeline, which comprises a magnetic ring formed by stacking a plurality of groups of strip permalloy magnetic strips, at least 3 magnetic Hall elements and at least 3 signal conditioning modules; the magnetic ring is conveniently opened and closed by adopting a special design, and good consistency of measured data is ensured under the condition of repeated opening and closing, so that the convenience of installation and the accuracy of the measured data on the oil and gas pipeline site are achieved; a magnetic Hall element is embedded in the magnetic ring and generates a Hall effect to generate voltage; the signal conditioning module consists of a magnetic Hall element voltage acquisition module, an operational amplification module, a voltage output module and a power supply module; the magnetic Hall element voltage acquisition module is used for acquiring small voltage acquired by a magnetic Hall element on the magnetic ring and transmitting a signal to the operational amplification module; the operation amplification module transmits signals obtained after the signals are amplified in equal proportion to the voltage output module; the voltage output module transmits the amplified voltage signal to an output interface for other equipment to use; the power supply module provides stable power supply for the magnetic Hall element voltage acquisition module, the operational amplification module and the voltage output module.
Preferably, the magnetic ring is provided with a plurality of long nails for fixing the shape of the magnetic ring.
In any of the above technical solutions, preferably, the strip-shaped permalloy magnetic strip used for the magnetic ring is a soft strip-shaped permalloy magnetic strip.
In any of the above technical solutions, preferably, the magnetic ring is formed by stacking 5 soft strip permalloy magnetic strips, the oil and gas pipeline low-frequency stray current open-type magnetic measurement device is formed by 3 magnetic hall elements and 3 signal conditioning modules, the 3 magnetic hall elements are embedded in the 5 soft strip permalloy magnetic strips, the 5 soft strip permalloy magnetic strips are tightly attached to each other to form a magnetic ring, the 3 magnetic hall elements are respectively embedded in the left side, the right side and the lower side of the magnetic ring, the mounting structure is used for measuring the magnetic induction intensity generated by the current of the conductor in the middle of the magnetic ring, and the measurement directions of the mounting structure are all counterclockwise along the tangent line of the magnetic ring.
In any of the above technical solutions, preferably, the magnetic ring is in a fixed annular shape, 5 soft strip permalloy magnetic strips are tightly attached, the soft strip permalloy magnetic strips are bent in an annular shape, and the 3 magnetic hall elements are fixed by using a spike punch, and the spike is ensured to be insulated from the magnetic ring.
In any of the above technical solutions, it is preferable that, before the installation of the oil and gas pipeline low-frequency stray current open-type magnetic measurement device is completed, the upper portion of the magnetic ring is kept in an open state, after the pipeline is sleeved, the soft strip permalloy magnetic conductive strip is bent to close the magnetic ring into a circular ring shape, and the magnetic ring is fixed by using a long nail.
In any of the above technical solutions, preferably, the oil and gas pipeline low-frequency stray current open-type magnetic measurement device includes a soft strip permalloy magnetic conductive strip L1-L′1、L2-L′2、L3-L′3、L4-L′4And L5-L′5The magnetic ring comprises magnetic rings, magnetic Hall elements 5-5 ', 9-9' and 13-13 'embedded in the magnetic rings, 3 signal conditioning modules and spikes 1-1', 2-2 ', 3-3', 6-6 ', 7-7', 8-8 ', 10-10', 11-11 ', 12-12', 14-14 ', 15-15', 16-16 'and 17-17' for fixing the shapes of the magnetic rings; in the mounting structure, 1 ', 2 ', 3 ', 4 ', 6 ', 7 ', 8 ', 10 ', 11 ', 12 ', 14 ', 15 ', 16 ' and 17 ' are fixing holes, and 5 ', 9 ' and 13 ' are positions for fixing the magnetic Hall element; in the mounting structure, the soft strip permalloy magnetic strips are wound into a ring shape and then tightly attached to each other at the upper end of the magnetic ring, and are fastened through the long nails, so that each soft strip permalloy magnetic strip is tightly contacted, the low magnetic resistance of the magnetic ring is ensured, and an effective magnetic path is established for magnetic induction lines in the magnetic ring.
The invention also discloses an oil-gas pipeline low-frequency stray current open-type magnetic measurement method, which adopts the oil-gas pipeline low-frequency stray current open-type magnetic measurement device. Adopt open-loop magnetism hall current measurement principle to accomplish oil gas pipeline low frequency stray current open-type magnetism measuring device's installation, measure oil gas pipeline low frequency stray current, specifically include following step:
1) mixing L with1-L′1、L2-L′2、L3-L′3、L4-L′4And L5-L′55 soft strip permalloy magnetic conductive strips are tightly attached together and curled upwards from the position of 9' according to a circular ring shape;
2) the method comprises the following steps of arranging 3 magnetic Hall elements at different positions in a magnetic ring by adopting a measuring method for avoiding errors caused by eccentricity of a pipeline, embedding 3 magnetic Hall elements at the positions 5 ', 9 ' and 13 ', perforating and fixing the magnetic Hall elements at the positions 6 ', 7 ', 8 ', 10 ', 11 ' and 12 ' by using hard long nails, and forming and fixing 5 soft strip permalloy magnetic guide strips into a semicircular magnetic ring with an opening at the upper half part, wherein the measuring operation is not carried out at the moment, and the magnetic Hall elements are in an opening state;
3) when the magnetic ring installed in the step 1) and the step 2) is used as an oil-gas pipeline low-frequency stray current open-type magnetic measuring device to measure the oil-gas pipeline low-frequency stray current, excavating the landfill soil around the pipeline to be measured, and sleeving the pipeline from the opening of the upper half part;
4) curling two sides of 5 soft strip permalloy magnetic strips inwards from 4 'and 14' according to a ring shape, and stacking two sides of each soft strip permalloy magnetic strip at one time to ensure that the contact area of each soft strip permalloy magnetic strip is large enough;
5) punching and fixing the positions 1 ', 2', 3 ', 4', 14 ', 15', 16 'and 17' by using hard long nails, and forming and fixing 5 soft strip permalloy magnetic strips into a complete annular magnetic ring to ensure that the soft strip permalloy magnetic strips are mutually stacked in a large enough contact area and are in a closed state;
6) starting a signal conditioning module in the oil-gas pipeline low-frequency stray current open-type magnetic measurement device, and measuring the magnetic induction intensity B of the positions of 3 magnetic Hall elements1、B2And B3；
7) According to the field situation, the diameter R of the magnetic ring and the vacuum permeability mu are adjusted0As a constant, and B measured1，B2，B3Substituting into formula
And obtaining the accurate low-frequency stray current value of the oil-gas pipeline.
In any of the above technical solutions, preferably, the measurement method for avoiding an error caused by eccentricity of the pipe includes: according to the Pitot-savart theorem, the magnetic induction intensity generated by the current I flowing in the infinite straight wire at a point P away from the wire by R is
Wherein, mu0Is the magnetic permeability in vacuum; in the measurement of the oil and gas pipeline current, the oil and gas pipeline current is equivalent to an infinite straight conducting wire positioned at the axis of the pipeline so as to be convenient for the calculation of the pipeline current; according to the formula (1), the magnetic induction intensity generated by the current is in direct proportion to the current and in inverse proportion to the distance between the measuring point and the current; when the installation of the magnetic ring can not ensure that the axis of the pipeline and the circle center of the magnetic ring are completely overlapped, a very large measurement error can be caused, in order to reduce the error caused by the deviation of the axis of the pipeline, 3 magnetic Hall elements are arranged at different positions in the magnetic ring of the oil-gas pipeline low-frequency stray current open-type magnetic measurement device to eliminate the error, and the specific method comprises the following steps:
assuming a positional relationship of the pipe, the magnetic ring and the magnetic sensor: the circle center of the magnetic ring is O, and the axis of the pipeline is O/The positions of the magnetic sensor on the magnetic ring are H1, H2 and H3, H1 and H2 are on the same straight line, H1 and H3 are mutually vertical, and H2 and H3 are mutually vertical; taking a magnetic ring of the oil-gas pipeline low-frequency stray current open-type magnetic measuring device as a plane, establishing an x-y axis coordinate system, wherein the radius of the magnetic ring is R, and the circle center of the magnetic ring is an origin of coordinates O (0, 0); magnetic Hall element H on left side of magnetic ring1The coordinate of the position is (-R,0), and the measuring direction is vertically downward along the anticlockwise tangential direction of the magnetic ring; magnetic Hall element H on right side of magnetic ring2The coordinates are (R,0),the measuring direction is vertically upward along the anticlockwise tangential direction of the magnetic ring; magnetic Hall element H below magnetic ring3The coordinate is (0, -R), and the measuring direction is vertically to the right along the anticlockwise tangential direction of the magnetic ring; the axis coordinate of the pipeline is O' (x, y), and the low-frequency stray current in the pipeline is I; the measuring directions of the 3 magnetic Hall elements are all along the anticlockwise tangential direction of the magnetic ring, and the measuring results are B1、B2And B3(ii) a The distance between the measuring point of the 3 magnetic Hall elements and the axial center point O' (x, y) of the pipeline is R1、R2And R3；
Obtaining the expressions of the magnetic induction intensity of the sensor at three positions according to the formula (1):
the following equation sets are established according to equation (2) and the distance equation between two points:
solving the expression of the pipeline current I through the above equation set (3), namely the equation (4):
measuring the positions of 3 magnetic Hall elements to obtain a result B1、B2And B3The numerical value of I can be calculated by taking the value into consideration, and the accurate low-frequency stray current value of the oil-gas pipeline can be obtained without considering the offset of the axis of the pipeline and the circle center of the magnetic ring.
Compared with the prior art, the technical scheme of the invention has the following characteristics:
1. the current of the oil-gas pipeline measured by the magnetic sensor is superior to that of the traditional current Hall sensor.
2. The open type structure has high precision. A plurality of groups of soft permalloy magnetic conductive strips are stacked to form a magnetic ring of the measuring device, the contact area of the magnetic sheets at the joint of the magnetic ring is larger, and the consistency and the accuracy of measured data are ensured. The soft magnetic sheet enables the opening and closing modes to be easier to operate, and the field installation to be more convenient and faster. And because the contact area is large, the repeatability of the measurement result in a high-precision range is ensured before and after the transmitter is started.
3. The magnetic Hall element has high positioning precision. The magnetic induction intensity generated by the current is measured by adopting 3 magnetic Hall elements, and the measurement error caused by the eccentricity of the pipeline is corrected by an algorithm, so that the calculation result of the current is more accurate.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a schematic diagram of the open-loop Hall current measurement principle of the oil and gas pipeline low-frequency stray current open-type magnetic measurement device according to the invention;
FIG. 2 is a block diagram of a signal conditioning module of a preferred embodiment of the oil and gas pipeline low frequency stray current open-type magnetic measurement device according to the present invention;
FIG. 3 is a schematic structural diagram of a magnetic ring of a preferred embodiment of the oil and gas pipeline low-frequency stray current open-type magnetic measurement device in an open state according to the present invention;
FIG. 4 is a schematic structural diagram of a magnetic ring of a preferred embodiment of the oil and gas pipeline low-frequency stray current open-type magnetic measurement device in a closed state according to the present invention;
FIG. 5 is a schematic view of the outermost layer of the magnet ring of the low-frequency stray current open-type magnetic measurement device for an oil and gas pipeline according to a preferred embodiment of the invention;
FIG. 6 is a flow chart of a measurement method of a preferred embodiment of the oil and gas pipeline low frequency stray current open-type magnetic measurement method according to the present invention;
fig. 7 is a schematic diagram of the measurement of the pipeline current by the oil and gas pipeline low-frequency stray current open-type measurement device according to a preferred embodiment of the oil and gas pipeline low-frequency stray current open-type magnetic measurement method.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to solve the problems of measurement of low-frequency stray current of an oil and gas pipeline in the prior art, the embodiment of the invention provides an oil and gas pipeline low-frequency stray current open-type magnetic measurement device and method.
The oil and gas pipeline low-frequency stray current open-type measuring device provided by the embodiment of the invention comprises a magnetic ring formed by stacking a plurality of groups of strip permalloy magnetic strips, 3 magnetic Hall elements and 3 signal conditioning modules. The magnetic ring of the measuring device can be conveniently opened and closed by adopting a special design, and the good consistency of the measured data can be ensured under the condition of repeated opening and closing, so that the installation convenience and the measured data accuracy on the oil and gas pipeline site are achieved.
The oil and gas pipeline low frequency stray current open-type measuring device of this embodiment has adopted open-loop magnetism hall current measurement principle, and its principle is shown as figure 1. The conductor to be tested is placed at the circle center of the magnetic ring, Ip is current flowing in the conductor to be tested, when Ip flows through the lead, a magnetic field is generated around the lead, the magnetic induction intensity of the magnetic field is in direct proportion to the current, the magnetic field is gathered in the magnetic ring, and the magnetic Hall element generates a Hall effect through the magnetic Hall element embedded in the magnetic ring, generates voltage, and outputs the voltage after being amplified through the operational amplifier module. The output voltage is proportional to the magnetic induction, i.e., the magnitude of Ip.
The signal conditioning module in the oil and gas pipeline low-frequency stray current open-type measuring device described in this embodiment functions as an operational amplifier, converts the magnetic induction intensity generated by Ip current into a voltage signal for output, and the structure diagram is shown in fig. 2. The signal conditioning module consists of a magnetic Hall element voltage acquisition module, an operational amplification module, a voltage output module and a power supply module. The magnetic Hall element voltage acquisition module acquires small voltage acquired by a magnetic Hall element on the magnetic ring and transmits the signal to the operational amplification module, the operational amplification module transmits the signal acquired after the signal is amplified in equal proportion to the voltage output module, and the voltage output module transmits the amplified voltage signal to the output interface for other equipment to use. The power supply module provides stable power supply for the magnetic Hall element voltage acquisition module, the operational amplification module and the voltage output module.
This embodiment oil gas pipeline low frequency stray current open-type measuring device, its magnetic ring structural design:
the traditional clamp type Hall current sensor cannot ensure the close contact of the magnetic ring, so that the measurement error is large. A magnetic ring in the oil-gas pipeline low-frequency stray current open-type measuring device adopts a new structure so as to achieve the close contact of the magnetic ring. Fig. 3 is a schematic structural diagram of a magnetic ring in an oil-gas pipeline low-frequency stray current open-type measuring device in an open state. Wherein 1-1 ', 2-2', 3-3 ', 6-6', 7-7 ', 8-8', 10-10 ', 11-11', 12-12 ', 14-14', 15-15 ', 16-16' and 17-17 'are long nails in the shape of a fixed magnetic ring, 5-5', 9-9 'and 13-13' are magnetic Hall elements embedded in the magnetic ring, and L is L1-L′1、L2-L′2、L3-L′3、L4-L′4And L5-L′5Is a flexible strip of permalloy magnetically conductive strip (5 strips are assumed here for ease of discussion and description). The magnetic ring is composed of 5 soft strip permalloy magnetic strips, and 3 magnetic Hall elements are embedded in the magnetic ring. 5 soft strip permalloy magnetic conductive strips are tightly attached together and wound into a magnetic ring, and 3 magnetic Hall elements are respectively embedded in the left side, the right side and the lower part of the magnetic ring and used for measuring the magnetic induction intensity generated by the current of the middle conductor of the magnetic ring, and the measuring directions are all inverses of the tangent lines of the magnetic ringThe hour hand direction. In order to ensure that the magnetic ring is in a fixed annular shape, all the soft strip-shaped permalloy magnetic strips are tightly attached, the soft strip-shaped permalloy magnetic strips are bent in an annular shape, the positions 6 ', 7', 8 ', 10', 11 'and 12' among the 3 Hall elements are fixed by using long nail through holes, and the insulation between the long nails and the magnetic ring is ensured so as to ensure that the shape of the magnetic ring is fixed to be circular. Before installation, the upper part of the magnetic ring is kept in an open state, after the pipeline is sleeved, the soft strip-shaped permalloy magnetic guide strip is bent to enable the magnetic ring to be closed into a circular ring shape, and the magnetic ring is fixed by using a long nail.
Fig. 4 is a schematic structural diagram of the oil and gas pipeline low-frequency stray current open-type measuring device in a closed state. Wherein 1-1 ', 2-2', 3-3 ', 6-6', 7-7 ', 8-8', 10-10 ', 11-11', 12-12 ', 14-14', 15-15 ', 16-16' and 17-17 'are long nails in the shape of a fixed magnetic ring, 5-5', 9-9 'and 13-13' are magnetic Hall elements embedded in the magnetic ring, and L is L1-L′1、L2-L′2、L3-L′3、L4-L′4And L5-L′5Is a soft strip permalloy magnetic conductive strip. At the upper end of the magnetic ring, the soft strip permalloy magnetic conductive strips are wound into a ring shape and then tightly attached together in a mode of a graph 4, and are fastened by using long nails, so that each soft strip permalloy magnetic conductive strip is in close contact, the low magnetic resistance of the magnetic ring is ensured, and an effective magnetic path is established for magnetic induction lines in the magnetic ring.
Fig. 5 is an expanded view of the outermost layer of the magnetic ring. Wherein 1 ', 2 ', 3 ', 4 ', 6 ', 7 ', 8 ', 10 ', 11 ', 12 ', 14 ', 15 ', 16 ' and 17 ' are fixing holes, and 5 ', 9 ' and 13 ' are positions for fixing the magnetic Hall element.
The magnetic ring of this structure has improved the maneuverability at the on-the-spot installation of oil gas pipeline, has also guaranteed the close contact of each magnetic strip of leading when the magnetic ring closes simultaneously, makes the magnetic ring can both keep the uniformity of measured data under the condition of repeated dismouting.
By adopting the scheme, the low-frequency stray current open-type measuring device for the oil and gas pipeline is installed and the pipeline current is measured, as shown in figure 6, the steps are as follows:
1) as shown in FIG. 1, mixing L1-L′1、L2-L′2、L3-L′3、L4-L′4And L5-L′ 55 soft strip permalloy magnetic conductive strips are tightly attached together and curled upwards from the position of 9' according to a circular ring shape;
2) 3 magnetic Hall elements are embedded at the positions 5 ', 9 ' and 13 ', and are fixed by punching holes at the positions 6 ', 7 ', 8 ', 10 ', 11 ' and 12 ' by using hard long nails, 5 magnetic strips are formed and fixed into a semicircular magnetic ring with an opening at the upper half part, and at the moment, the measurement work is not carried out, and the magnetic Hall element is in an opening state;
3) when the measuring device is used as a measuring device for measuring the low-frequency stray current of the oil-gas pipeline, digging out the landfill soil around the pipeline to be measured, and sleeving the pipeline from the opening of the upper half part;
4) as shown in fig. 2, two sides of 5 soft strip-shaped permalloy magnetic strips are curled inwards from 4 'and 14' in a ring shape, and the two sides of each soft strip-shaped permalloy magnetic strip are stacked once, so that the contact area of each soft strip-shaped permalloy magnetic strip is ensured to be large enough;
5) as shown in fig. 2, hard spikes are used to punch and fix the positions 1 ', 2', 3 ', 4', 14 ', 15', 16 'and 17', and 5 soft strip permalloy magnetic strips are combined and fixed into a complete annular magnetic ring, so as to ensure that the soft strip permalloy magnetic strips are mutually stacked with a sufficiently large contact area and are in a closed state;
6) starting a signal conditioning module in the oil-gas pipeline low-frequency stray current open-type measuring device, and measuring the magnetic induction intensity B of the positions of 3 magnetic Hall elements shown in figure 61、B2And B3；
7) According to the field situation, the diameter R of the magnetic ring and the vacuum permeability mu are adjusted0As a constant, and B measured1，B2，B3And (4) substituting the formula (4) to obtain the accurate low-frequency stray current value of the oil-gas pipeline.
In the process of measuring the pipeline current by adopting the oil-gas pipeline low-frequency stray current open-type measuring device, the measuring method for avoiding the error caused by the eccentricity of the pipeline comprises the following steps:
according to the Biao-Saval theorem, the magnetic induction intensity generated by the current I flowing in the infinite straight wire at a point P away from the point R is equal to
Wherein, mu0Is the permeability in vacuum.
In the measurement of the current of the oil and gas pipeline, the oil and gas pipeline can be considered to be a steel ring with uniformly distributed materials, and the current is uniformly distributed along the steel ring, so that the current of the oil and gas pipeline can be equivalent to an infinite straight wire positioned at the axis of the pipeline, and the calculation of the current of the pipeline is facilitated.
According to the above formula, the magnetic induction intensity generated by the current is proportional to the magnitude of the current and inversely proportional to the distance from the measuring point to the current. For a large-diameter conductor such as an oil-gas pipeline, the magnetic ring installation of the measuring device cannot ensure that the axis of the pipeline is completely overlapped with the circle center of the magnetic ring, so that a very large measuring error can be caused.
In order to reduce errors caused by the deviation of the axis of the pipeline, the oil-gas pipeline low-frequency stray current open-type measuring device adopts 3 magnetic Hall elements which are positioned at different positions in a magnetic ring to eliminate the errors. The specific method comprises the following steps:
assuming that the positions of the pipeline, the magnetic ring and the magnetic sensor are as shown in FIG. 7, the center of the magnetic ring is O, and the axis of the pipeline is O/The positions of the magnetic sensors on the magnetic ring are H1, H2 and H3 coordinates as shown in the figure, H1 and H2 are on the same straight line, H1 and H3 are perpendicular to each other, and H2 and H3 are perpendicular to each other. Taking a magnetic ring of the oil-gas pipeline low-frequency stray current open-type measuring device as a plane, establishing an x-y axis coordinate system, taking the radius of the magnetic ring as R, taking the circle center of the magnetic ring as a coordinate origin O (0,0), and taking a magnetic Hall element H on the left side of the magnetic ring1The coordinate of the position is (-R,0), the measuring direction is vertically downward along the anticlockwise tangential direction of the magnetic ring, and the magnetic Hall element H on the right side of the magnetic ring2The coordinates are(R,0) the measuring direction is vertically upward along the anticlockwise tangential direction of the magnetic ring, and the magnetic Hall element H below the magnetic ring3The coordinates are (0, -R), the measuring direction is perpendicular to the right along the anticlockwise tangential direction of the magnetic ring, the axis coordinate of the pipeline is O' (x, y), and the low-frequency stray current in the pipeline is I. The installation mode of the 3 magnetic Hall elements is shown in figure 6, the measurement directions are all along the anticlockwise tangential direction of the magnetic ring, and the measurement results are B1、B2And B3. The distances between the three magnetic Hall element measuring points and the pipeline axis point O' (x, y) are R respectively1、R2And R3。
The sensor magnetic induction intensity expressions of three positions can be obtained according to the formula (1):
the following equation set can be established according to equation (2) and the distance equation between two points:
the expression for the pipe current I can be solved by the above equation set (3):
measuring the positions of 3 magnetic Hall elements to obtain a result B1、B2And B3The value of I can be obtained by substituting. The method does not need to consider the offset of the axis of the pipeline and the circle center of the magnetic ring, and the obtained result is more accurate.
The foregoing is merely illustrative of the preferred embodiments of the present invention and is not to be construed as limiting the scope of the invention; the above description is only for the specific embodiment of the present invention, and is not intended to limit the scope of the present invention; any modification, equivalent replacement, improvement and the like of the technical solution of the present invention by a person of ordinary skill in the art without departing from the design spirit of the present invention shall fall within the protection scope determined by the claims of the present invention.
The patent of the invention is funded by the fund of national emphasis research and development project (No. 2016YFC0802103).
Claims (9)
1. The utility model provides an oil gas pipeline low frequency stray current open-type magnetic measuring device for accurate measurement oil gas pipeline low frequency stray current, its characterized in that: the measuring device comprises a magnetic ring formed by stacking a plurality of groups of strip permalloy magnetic strips, at least 3 magnetic Hall elements and at least 3 signal conditioning modules; the magnetic ring is conveniently opened and closed by adopting a special design, and good consistency of measured data is ensured under the condition of repeated opening and closing, so that the convenience of installation and the accuracy of the measured data on the oil and gas pipeline site are achieved; a magnetic Hall element is embedded in the magnetic ring and generates a Hall effect to generate voltage; the signal conditioning module consists of a magnetic Hall element voltage acquisition module, an operational amplification module, a voltage output module and a power supply module; the magnetic Hall element voltage acquisition module is used for acquiring small voltage acquired by a magnetic Hall element on the magnetic ring and transmitting a signal to the operational amplification module; the operation amplification module transmits signals obtained after the signals are amplified in equal proportion to the voltage output module; the voltage output module transmits the amplified voltage signal to an output interface for other equipment to use; the power supply module provides stable power supply for the magnetic Hall element voltage acquisition module, the operational amplification module and the voltage output module.
2. The oil and gas pipeline low frequency stray current open-type magnetic measurement device of claim 1, characterized by: the magnetic ring is provided with a plurality of long nails, and the long nails are used for fixing the shape of the magnetic ring.
3. The oil and gas pipeline low frequency stray current open-type magnetic measurement device of claim 1, characterized by: the strip-shaped permalloy magnetic strip adopted by the magnetic ring is a soft strip-shaped permalloy magnetic strip.
4. The oil and gas pipeline low-frequency stray current open-type magnetic measurement device of any one of claims 1, 2 and 3, wherein: the magnetic ring that piles up to form by 5 soft banding permalloy magnetic conduction strips, 3 magnetic hall elements and 3 oil gas pipeline low frequency stray current open-type magnetic measuring device that signal conditioning module constitutes, 3 magnetic hall elements of embedding in 5 soft banding permalloy magnetic conduction strips, 5 soft banding permalloy magnetic conduction strips hug closely and are coiled into a magnetic ring together, the left side of magnetic ring, 3 magnetic hall elements are embedded respectively to right side and below, mounting structure is used for measuring the produced magnetic induction intensity of magnetic ring intermediate conductor current, its measuring direction is the anticlockwise along the magnetic ring tangent line.
5. The oil and gas pipeline low frequency stray current open-type magnetic measurement device of claim 4, characterized by: the magnetic ring is in a fixed annular shape, 5 soft strip-shaped permalloy magnetic conducting strips are tightly attached, the soft strip-shaped permalloy magnetic conducting strips are bent in an annular shape, and the 3 magnetic Hall elements are fixed by using long nail punching holes, so that the long nails are ensured to be insulated from the magnetic ring.
6. The oil and gas pipeline low frequency stray current open-type magnetic measurement device of claim 4, characterized by: before the installation of the oil-gas pipeline low-frequency stray current open-type magnetic measuring device is completed, the upper part of the magnetic ring is kept in an open state, after the pipeline is sleeved, the soft strip-shaped permalloy magnetic conducting strip is bent to enable the magnetic ring to be closed into a circular ring shape, and the magnetic ring is fixed by using a long nail.
7. The oil and gas pipeline low frequency stray current open-type magnetic measurement device of claim 4, characterized by: the oil-gas pipeline low-frequency stray current open-type magnetic measurement device comprises a soft strip permalloy magnetic conduction strip L1-L′1、L2-L′2、L3-L′3、L4-L′4And L5-L′5Magnetic ring composed of stack, magnetic Hall elements 5-5 ', 9-9 ' and 13-13 ', 3 signal coils embedded in the magnetic ringThe number conditioning module and the spikes 1-1 ', 2-2 ', 3-3 ', 6-6 ', 7-7 ', 8-8 ', 10-10 ', 11-11 ', 12-12 ', 14-14 ', 15-15 ', 16-16 ' and 17-17 ' in the shape of the fixed magnetic ring; in the mounting structure, 1 ', 2 ', 3 ', 4 ', 6 ', 7 ', 8 ', 10 ', 11 ', 12 ', 14 ', 15 ', 16 ' and 17 ' are fixing holes, and 5 ', 9 ' and 13 ' are positions for fixing the magnetic Hall element; in the mounting structure, the soft strip permalloy magnetic strips are wound into a ring shape and then tightly attached to each other at the upper end of the magnetic ring, and are fastened through the long nails, so that each soft strip permalloy magnetic strip is tightly contacted, the low magnetic resistance of the magnetic ring is ensured, and an effective magnetic path is established for magnetic induction lines in the magnetic ring.
8. An oil and gas pipeline low-frequency stray current open-type magnetic measurement method, which adopts the oil and gas pipeline low-frequency stray current open-type magnetic measurement device as claimed in any one of claims 1 to 7, and is characterized in that: adopt open-loop magnetism hall current measurement principle to accomplish oil gas pipeline low frequency stray current open-type magnetism measuring device's installation, measure oil gas pipeline low frequency stray current, specifically include following step:
1) mixing L with1-L′1、L2-L′2、L3-L′3、L4-L′4And L5-L′55 soft strip permalloy magnetic conductive strips are tightly attached together and curled upwards from the position of 9' according to a circular ring shape;
2) the method comprises the following steps of arranging 3 magnetic Hall elements at different positions in a magnetic ring by adopting a measuring method for avoiding errors caused by eccentricity of a pipeline, embedding 3 magnetic Hall elements at the positions 5 ', 9 ' and 13 ', perforating and fixing the magnetic Hall elements at the positions 6 ', 7 ', 8 ', 10 ', 11 ' and 12 ' by using hard long nails, and forming and fixing 5 soft strip permalloy magnetic guide strips into a semicircular magnetic ring with an opening at the upper half part, wherein the measuring operation is not carried out at the moment, and the magnetic Hall elements are in an opening state;
3) when the magnetic ring installed in the step 1) and the step 2) is used as an oil-gas pipeline low-frequency stray current open-type magnetic measuring device to measure the oil-gas pipeline low-frequency stray current, excavating the landfill soil around the pipeline to be measured, and sleeving the pipeline from the opening of the upper half part;
4) curling two sides of 5 soft strip permalloy magnetic strips inwards from 4 'and 14' according to a ring shape, and stacking two sides of each soft strip permalloy magnetic strip at one time to ensure that the contact area of each soft strip permalloy magnetic strip is large enough;
5) punching and fixing the positions 1 ', 2', 3 ', 4', 14 ', 15', 16 'and 17' by using hard long nails, and forming and fixing 5 soft strip permalloy magnetic strips into a complete annular magnetic ring to ensure that the soft strip permalloy magnetic strips are mutually stacked in a large enough contact area and are in a closed state;
6) starting a signal conditioning module in the oil-gas pipeline low-frequency stray current open-type magnetic measurement device, and measuring the magnetic induction intensity B of the positions of 3 magnetic Hall elements1、B2And B3；
7) According to the field situation, the diameter R of the magnetic ring and the vacuum permeability mu are adjusted0As a constant, and B measured1，B2，B3Substituting into formula
And obtaining the accurate low-frequency stray current value of the oil-gas pipeline.
9. The oil and gas pipeline low-frequency stray current open-type magnetic measurement method of claim 8, wherein: the measuring method for avoiding the error caused by the eccentricity of the pipeline comprises the following steps: according to the Pitot-savart theorem, the magnetic induction intensity generated by the current I flowing in the infinite straight wire at a point P away from the wire by R is
Wherein, mu0Is the magnetic permeability in vacuum; in the measurement of oil and gas pipeline current, oil and gas are introducedThe pipeline current is equivalent to an infinite straight wire positioned at the axis of the pipeline so as to be convenient for calculating the pipeline current; according to the formula (1), the magnetic induction intensity generated by the current is in direct proportion to the current and in inverse proportion to the distance between the measuring point and the current; when the installation of the magnetic ring can not ensure that the axis of the pipeline and the circle center of the magnetic ring are completely overlapped, a very large measurement error can be caused, in order to reduce the error caused by the deviation of the axis of the pipeline, 3 magnetic Hall elements are arranged at different positions in the magnetic ring of the oil-gas pipeline low-frequency stray current open-type magnetic measurement device to eliminate the error, and the specific method comprises the following steps:
assuming a positional relationship of the pipe, the magnetic ring and the magnetic sensor: the circle center of the magnetic ring is O, and the axis of the pipeline is O/The positions of the magnetic sensor on the magnetic ring are H1, H2 and H3, H1 and H2 are on the same straight line, H1 and H3 are mutually vertical, and H2 and H3 are mutually vertical; taking a magnetic ring of the oil-gas pipeline low-frequency stray current open-type magnetic measuring device as a plane, establishing an x-y axis coordinate system, wherein the radius of the magnetic ring is R, and the circle center of the magnetic ring is an origin of coordinates O (0, 0); magnetic Hall element H on left side of magnetic ring1The coordinate of the position is (-R,0), and the measuring direction is vertically downward along the anticlockwise tangential direction of the magnetic ring; magnetic Hall element H on right side of magnetic ring2The coordinate is (R,0), and the measuring direction of the coordinate is vertically upward along the counterclockwise tangent direction of the magnetic ring; magnetic Hall element H below magnetic ring3The coordinate is (0, -R), and the measuring direction is vertically to the right along the anticlockwise tangential direction of the magnetic ring; the axis coordinate of the pipeline is O' (x, y), and the low-frequency stray current in the pipeline is I; the measuring directions of the 3 magnetic Hall elements are all along the anticlockwise tangential direction of the magnetic ring, and the measuring results are B1、B2And B3(ii) a The distance between the measuring point of the 3 magnetic Hall elements and the axial center point O' (x, y) of the pipeline is R1、R2And R3；
Obtaining the expressions of the magnetic induction intensity of the sensor at three positions according to the formula (1):
the following equation sets are established according to equation (2) and the distance equation between two points:
solving the expression of the pipeline current I through the above equation set (3), namely the equation (4):
measuring the positions of 3 magnetic Hall elements to obtain a result B1、B2And B3The numerical value of I can be calculated by taking the value into consideration, and the accurate low-frequency stray current value of the oil-gas pipeline can be obtained without considering the offset of the axis of the pipeline and the circle center of the magnetic ring.
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