CN115825519B - Measuring system of cantilever beam type extrinsic optical fiber double-Fabry-Perot current transformer - Google Patents
Measuring system of cantilever beam type extrinsic optical fiber double-Fabry-Perot current transformer Download PDFInfo
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- CN115825519B CN115825519B CN202310011552.1A CN202310011552A CN115825519B CN 115825519 B CN115825519 B CN 115825519B CN 202310011552 A CN202310011552 A CN 202310011552A CN 115825519 B CN115825519 B CN 115825519B
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Abstract
The invention provides a measuring system of an cantilever beam type extrinsic optical fiber dual-Fabry-Perot current transformer, and belongs to the technical field of measuring devices. The invention comprises the following steps: the system comprises a magnetic conduction loop, a cantilever beam type extrinsic Fabry-Perot sensor, a permanent magnet and a demodulation system; the cantilever beam type extrinsic Fabry-Perot sensor is provided with two Fabry-Perot cavities, wherein one Fabry-Perot cavity is influenced by cantilever beam strain and environmental temperature, and the other Fabry-Perot cavity is only influenced by the environmental temperature. According to the invention, by arranging the two Fabry-Perot cavities, one Fabry-Perot cavity is influenced by the strain of the cantilever beam and the ambient temperature, the other Fabry-Perot cavity is influenced by the ambient temperature only, and the influence of the ambient temperature on the sensor can be eliminated by making a difference between the output light signals of the two Fabry-Perot cavities, so that the current measurement range and the sensitivity are improved.
Description
Technical Field
The invention relates to the technical field of current measurement devices, in particular to a measurement system of an cantilever beam type extrinsic optical fiber dual-Fabry-Perot current transformer.
Background
Along with the continuous increase of electricity consumption of the technological progress, the power transmission industry is increasingly refined and gradually developed to intelligent and networked, so that the requirements on power transmission are safer and more reliable. The development of the relay protection system is required to follow the steps of the power industry, wherein the part which is most central to relay protection in the power system is current measurement, and the current measurement is directly related to the reliability of system analysis, the accuracy of system detection and the safety of electric energy metering, which are key factors for maintaining the normal operation of the power system, so that the requirements on the accuracy and the reliability of current measurement and fault monitoring equipment are higher and higher. Along with the increase of the transmission capacity and the improvement of the voltage class of the power system, the traditional electromagnetic current transformer cannot meet the requirements of the intelligent power grid due to the defects of magnetic saturation, narrow measurement frequency band, potential insulation safety hazard, large volume and the like.
With the development of optical fiber sensing technology, the optical current transformer is widely applied in a plurality of fields by virtue of the advantages of electromagnetic interference resistance, wide measurement frequency band, small volume, on-line monitoring and the like. However, since the optical sensor is greatly affected by the ambient temperature, temperature compensation measures must be taken into consideration.
Therefore, a measuring device capable of solving the technical problem of temperature and strain cross sensitivity and improving the range and sensitivity of measuring current is urgently needed.
Disclosure of Invention
In view of the above, in order to solve the technical problem of temperature and strain cross sensitivity and improve the range and sensitivity of measured current, the invention provides a measuring system of a cantilever beam type extrinsic optical fiber dual-Fabry-Perot current transformer, which comprises two Fabry-Perot cavities, wherein one Fabry-Perot cavity is influenced by cantilever beam strain and environmental temperature, the other Fabry-Perot cavity is influenced by environmental temperature only, and the influence of the environmental temperature on a sensor can be eliminated by making a difference between output optical signals of the two Fabry-Perot cavities, so that the range and sensitivity of current measurement are improved.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a measurement system for an cantilever beam type extrinsic fiber dual fabry-perot current transformer, comprising:
the magnetic conduction loop is wound with an induction coil;
an cantilever beam type extrinsic Fabry-Perot sensor is provided with two Fabry-Perot cavities, wherein one Fabry-Perot cavity is influenced by cantilever beam strain and environmental temperature, and the other Fabry-Perot cavity is only influenced by the environmental temperature;
the permanent magnet is arranged on the cantilever beam type extrinsic Fabry-Perot sensor and is used for driving the cantilever beam to generate periodic strain;
a demodulation system for recovering a signal of a current to be measured, comprising:
the laser device sends out optical signals which enter the two Fabry-Perot cavities through the coupler to carry out refraction and reflection, and finally stable interference phenomena are formed at the two ends of the Fabry-Perot cavities;
the interferometer is used for receiving interference signals generated by the two Fabry-Perot cavities and changing the interference signals into periodic signals through a phase modulator in the interferometer;
an optical-to-electrical converter for demodulating the periodic signal into an electrical signal;
and the data acquisition card is used for acquiring the demodulated electric signals.
Preferably, the cantilever beam type extrinsic Fabry-Perot sensor comprises:
one end of the cantilever Liang Danying diaphragm is suspended, and the other end of the cantilever Liang Danying diaphragm is fixed;
and tail fibers with end surfaces plated with reflecting films of the optical fibers and the cantilever Liang Danying diaphragm form two Fabry-Perot cavities respectively.
Preferably, the cantilever beam type extrinsic Fabry-Perot sensor further comprises a glass sleeve and a fixed structure;
the two glass sleeves are connected through the fixing structure, the other end of the diaphragm of the cantilever Liang Danying is fixed on the fixing structure, and the optical fibers respectively penetrate through the two glass sleeves.
Preferably, the laser is a DFB semiconductor laser.
Preferably, the coupler is a 3db coupler.
Preferably, the interferometer is a mach-zehnder interferometer.
Compared with the prior art, the invention has the following beneficial effects:
according to the measuring system of the cantilever beam type extrinsic optical fiber Fabry-Perot current transformer, provided by the invention, two Fabry-Perot cavities are arranged, one Fabry-Perot cavity is influenced by the strain of the cantilever beam and the environmental temperature, the other Fabry-Perot cavity is influenced by the environmental temperature only, the influence of the environmental temperature on the sensor can be eliminated by making a difference between output light signals of the two Fabry-Perot cavities, and the current measuring range and the sensitivity are improved.
The measuring system of the cantilever beam type extrinsic optical fiber Fabry-Perot current transformer provided by the invention has high detection precision on dynamic strain signals by using a demodulation method of a Mach-Zehnder interferometer, and is suitable for measuring alternating current.
Drawings
FIG. 1 is a schematic diagram showing the variation of reflected light power of an extrinsic fiber Fabry-Perot sensor with cavity length;
FIG. 2 is a schematic structural diagram of an cantilever-type extrinsic fiber Fabry-Perot sensor;
FIG. 3 is a schematic diagram of a current measurement system of a fiber optic current transformer;
in the figure, 1, a magnetic conduction loop, 11, an induction coil, 2, a cantilever beam type extrinsic Fabry-Perot sensor, 21, a Fabry-Perot cavity, 22, a cantilever Liang Danying membrane, 23, an optical fiber, 24, a glass sleeve, 25, a fixed structure, 3, a permanent magnet, 4, a demodulation system, 41, a laser, 42, a coupler, 43, a phase modulator, 44, a photoelectric converter and 45, a data acquisition card.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention; it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments, and that all other embodiments obtained by persons of ordinary skill in the art without making creative efforts based on the embodiments in the present invention are within the protection scope of the present invention.
In the description of the present invention, it should be noted that the positional or positional relationship indicated by the terms such as "upper", "lower", "inner", "outer", "top/bottom", etc. are based on the positional or positional relationship shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
In the description of the present invention, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "configured to," "engaged with," "connected to," and the like are to be construed broadly, and may be either fixedly connected, detachably connected, or integrally connected, for example; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
As shown in fig. 3, the present invention provides a measurement system of an cantilever type extrinsic optical fiber fabry-perot current transformer, comprising:
the magnetic conduction loop 1 is wound with an induction coil 11;
an cantilever-type extrinsic Fabry-Perot sensor 2 having two Fabry-Perot cavities 21, one of which is affected by the cantilever strain and the ambient temperature and the other of which is affected only by the ambient temperature;
the permanent magnet 3 is arranged on the cantilever beam type extrinsic Fabry-Perot sensor 2 and is used for driving the cantilever beam to generate periodic strain;
a demodulation system 4 for recovering a signal of a current to be measured, comprising:
the laser 41, the optical signal that it sends enters two Fabry-Perot cavities 21 through the coupler 42, refract and reflect, form the stable interference phenomenon at the cavity 21 both ends of Fabry-Perot finally;
an interferometer for receiving the interference signals generated by the two fabry-perot cavities and converting the interference signals into periodic signals via a phase modulator 43 therein;
an optical-to-electrical converter 44 for demodulating the periodic signal into an electrical signal;
a data acquisition card 45 for acquiring the demodulated electrical signal.
In the present invention, the cantilever-type extrinsic Fabry-Perot sensor 2 includes:
the cantilever Liang Danying diaphragm 22, one end of which is suspended and the other end of which is fixed;
the tail fiber of the optical fiber 23, the end face of which is plated with a reflecting film, and the cantilever Liang Danying diaphragm 22 respectively form two Fabry-Perot cavities 21.
In the present invention, the cantilever-type extrinsic Fabry-Perot sensor 2 further comprises a glass sleeve 24 and a fixing structure 25;
the two glass sleeves 24 are connected through the fixing structure 25, the other end of the diaphragm 22 of the cantilever Liang Danying is fixed on the fixing structure 25, and the optical fibers 23 respectively penetrate through the two glass sleeves 24.
In the present invention, the laser 41 is a DFB semiconductor laser.
In the present invention, the coupler 42 is a 3db coupler.
In the invention, the interferometer is a Mach-Zehnder interferometer, has high detection precision on dynamic strain signals, and is suitable for measuring alternating current.
In the measuring system of the cantilever beam type extrinsic optical fiber Fabry-Perot current transformer, the cantilever beam type extrinsic Fabry-Perot sensor 2 is formed into the Fabry-Perot cavity 21 by two parallel planes with a certain reflectivity, and has the advantages of simple structure, high sensitivity and high response speed. The Fabry-Perot cavity 21 consists of a cantilever Liang Danying diaphragm and a tail fiber end face of the optical fiber coated with the reflecting film, and the cavity is air. According to the basic principle of multi-beam interference, the output optical power of the reflection spectrum of the cantilever beam type extrinsic Fabry-Perot sensor 2 is as follows:
in which I 0 (lambda) is the intensity of incident light, R 1 、R 2 The reflectivity of the end face of the tail fiber and the reflectivity of the quartz diaphragm are respectively, l is the cavity length of the Fabry-Perot cavity, lambda is the wavelength of incident light, n is the refractive index of medium in the cavity, and n=1 when the medium is air. As shown in fig. 1, a schematic diagram of the relationship between the reflected light power of the cantilever type extrinsic fp sensor 2 and the cavity length is shown.
As shown in fig. 2, one end of a quartz membrane 22 of a cantilever arm is suspended (a suspended end is formed), the other end of the quartz membrane 22 of the cantilever arm is fixed on a fixed structure 25 (a fixed end is formed), a cantilever beam structure is formed, then the tail fibers of the optical fibers with the two end surfaces coated with the reflecting films and the quartz membrane 22 of the cantilever arm form two fabry-perot cavities 21, preferably, the distance between the tail fiber end surfaces of the optical fibers and the quartz membrane 22 of the cantilever arm is adjusted by using an optical triaxial micro-motion instrument, so that the cavity lengths of the two fabry-perot cavities 21 are consistent, and then the tail fibers of the optical fibers are fixed by using ultraviolet curing glue. The structure can enable the Fabry-Perot cavity of one suspension end to be influenced by the strain of the cantilever beam and the environmental temperature, and the Fabry-Perot cavity of the other fixed end is only influenced by the environmental temperature, so that the influence of the environmental temperature on the sensor can be eliminated by making difference between output light signals of the two Fabry-Perot cavities.
In the invention, when the natural frequency of the cantilever Liang Danying diaphragm 22 is calculated, the Euler-Bernoulli theory or the iron Moschinokoff theory can be utilized to list the motion differential equation and the boundary condition of the cantilever Liang Danying diaphragm 22, and the equation is solved to obtain the first-order natural frequency. When the measured signal frequency does not exceed the first order natural frequency, the cantilever Liang Danying diaphragm 22 amplitude is relatively smooth and maximum at the natural frequency. The cantilever Liang Danying diaphragm 22 has a first order natural frequency of:
where h and L are the thickness and length, respectively, of the diaphragm 22 of cantilever Liang Danying and ρ and E are the mass density and Young's modulus, respectively, of the diaphragm 22 of cantilever Liang Danying. It can be seen that the shorter the length of the cantilever Liang Danying diaphragm 22, the greater the thickness, and the higher the first order natural frequency thereof.
In the invention, the demodulation system consists of a laser, a coupler, a phase modulator, a photoelectric converter and a data acquisition card, wherein the laser 41 is preferably a DFB semiconductor laser, and a narrow linewidth distributed feedback laser with the central working wavelength of 1550nm is adopted. The optical signals emitted by the DFB semiconductor laser enter two Fabry-Perot cavities through the coupler 42, multiple refraction and reflection are carried out between the end faces of the fiber pigtails and the diaphragms, and finally stable interference phenomena are formed on the two end faces of the Fabry-Perot cavities, and then two paths of reflected light enter the interferometer. The coupler 42 is preferably a 3dB coupler, and the interferometer is preferably a mach-zehnder interferometer.
The Mach-Zehnder interferometer is composed of a coupler and a phase modulator, and two paths of reflected light are received by the Mach-Zehnder interferometer, wherein one path of reflected light is used as a measuring arm, and the other path of reflected light is used as a reference arm. The phase modulator 43 is to wind and paste the optical fiber on the ring-shaped piezoelectric ceramic, and then stimulate the piezoelectric ceramic to make the optical fiber vibrate periodically, so that the interference signal becomes a periodic signal. The Mach-Zehnder interferometer converts the change of reflected light caused by the change of the cavity length of the Fabry-Perot cavity 21 into the change of the phase of an interference signal, finally, the demodulation of an output optical signal is realized through the photoelectric converter 44, the output end of the photoelectric converter 44 is connected with the data acquisition card 45, and the data acquisition card 45 is used for acquiring an electric signal demodulated by the photoelectric converter 44.
As shown in fig. 3, a preferred embodiment of a measurement system of an cantilever type extrinsic optical fiber fabry-perot current transformer provided by the present invention is shown, which is implemented by a magnetic conductive loop 1, an induction coil 11, a permanent magnet 3, and a cantilever type extrinsic optical fiber fabry-perot sensor 2. When current flows through the tested circuit, the electromagnetic induction causes the induction coil 11 wound on the magnetic conduction circuit 1 to generate alternating induced electromotive force, and periodic attractive force and repulsive force are generated on the permanent magnet 3 with fixed polarity, and the permanent magnet 3 is fixed with one end of the diaphragm 22 of the cantilever Liang Danying to drive the suspended end of the diaphragm 22 of the cantilever Liang Danying to generate periodic strain. Under the action of stress, the cavity length of the Fabry-Perot cavity 21 on the cantilever beam type extrinsic optical fiber Fabry-Perot sensor 2 changes, the amplitude and the phase of the output light of the sensor change, and finally, a signal of the current to be detected is restored through a demodulation system and is displayed in an oscilloscope.
In the invention, a preferred connection mode of the demodulation system is shown in fig. 3, a laser 41 is connected with an optical fiber 23 through a coupler 42, so that an optical signal emitted by the laser enters two Fabry-Perot cavities through the coupler for refraction and reflection, and finally, stable interference phenomena are formed at two end surfaces of the Fabry-Perot cavities; the interference signal is transmitted to a phase modulator 43 in the interferometer through a coupler 42, so that the interference signal is changed into a periodic signal, and finally, the periodic signal is converted into an electric signal through a photoelectric converter 44, and the electric signal is collected by a data collection card 45 and is displayed in an oscilloscope.
The above is only a preferred embodiment of the present invention; the scope of the invention is not limited in this respect. Any person skilled in the art, within the technical scope of the present disclosure, may apply to the present invention, and the technical solution and the improvement thereof are all covered by the protection scope of the present invention.
Claims (6)
1. A measurement system for an cantilever beam type extrinsic optical fiber dual-fabry-perot current transformer, comprising:
the magnetic conduction loop is wound with an induction coil;
an cantilever beam type extrinsic Fabry-Perot sensor is provided with two Fabry-Perot cavities, wherein one Fabry-Perot cavity is influenced by cantilever beam strain and environmental temperature, and the other Fabry-Perot cavity is only influenced by the environmental temperature;
the permanent magnet is arranged on the cantilever beam type extrinsic Fabry-Perot sensor and is used for driving the cantilever beam to generate periodic strain;
a demodulation system for recovering a signal of a current to be measured, comprising:
the laser device sends out optical signals which enter the two Fabry-Perot cavities through the coupler to carry out refraction and reflection, and finally stable interference phenomena are formed at the two ends of the Fabry-Perot cavities;
the interferometer is used for receiving interference signals generated by the two Fabry-Perot cavities and changing the interference signals into periodic signals through a phase modulator in the interferometer;
an optical-to-electrical converter for demodulating the periodic signal into an electrical signal;
the data acquisition card is used for acquiring the demodulated electrical signals;
the cavity lengths of the two Fabry-Perot cavities are identical, and the two Fabry-Perot cavities are extrinsic Fabry-Perot cavities.
2. The measurement system of the cantilever-type extrinsic optical fiber dual-fabry-perot current transformer according to claim 1, wherein the cantilever-type extrinsic fabry-perot sensor comprises:
one end of the cantilever Liang Danying diaphragm is suspended, and the other end of the cantilever Liang Danying diaphragm is fixed;
and tail fibers with end surfaces plated with reflecting films of the optical fibers and the cantilever Liang Danying diaphragm form two Fabry-Perot cavities respectively.
3. The measurement system of the cantilever-type extrinsic optical fiber dual-fabry-perot current transformer according to claim 2, wherein the cantilever-type extrinsic fabry-perot sensor further comprises a glass sleeve and a fixed structure;
the two glass sleeves are connected through the fixing structure, the other end of the diaphragm of the cantilever Liang Danying is fixed on the fixing structure, and the optical fibers respectively penetrate through the two glass sleeves.
4. The measurement system of the cantilever type extrinsic optical fiber dual-fabry-perot current transformer according to claim 1, wherein said laser is a DFB semiconductor laser.
5. The measurement system of the cantilever-type extrinsic optical fiber dual-fabry-perot current transformer according to claim 1, wherein said coupler is a 3db coupler.
6. The measurement system of an cantilever-type extrinsic optical fiber dual-fabry-perot current transformer according to claim 1, wherein said interferometer is a mach-zehnder interferometer.
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