The optical fiber extrinsic Fabry-Perot interference ultrasonic sensing detection device
Technical field
The present invention utilizes the optical fiber extrinsic Fabry-Perot interference ultrasonic sensing detection device that acoustic emission source is surveyed, and detects at the ultrasonic signal that is produced by acoustic emission sources such as material damage, partial discharge of transformer especially, belongs to sensory field of optic fibre,
Background technology
Acoustic emission source on the ordinary meaning is meant that generally material is subjected to the various distortion and the fracture mechanism that effect produced of external force, when this mechanism takes place, can follow stress wave generation and to around diffusion.Acoustic emission is a kind of important Non-Destructive Testing and evaluation means, it adopts high-sensitive sensor, be subjected to the effect of external force at material or member, and again before it reaches breakage, the acoustic emission signal that acceptance is produced when beginning to occur damaging from these materials or member, by analyzing and processing, realize assessment, thereby avoid the generation of accident material or member state to these signals.
Transformer is the vitals in the electric system, and it costs an arm and a leg, but various faults take place often, to the very big threat of normal safe operation formation of whole electric system.Related data shows, occur in the shelf depreciation (partialdischarge of transformer inside, PD) phenomenon is to cause the one of the main reasons of transformer fault, and the economic loss of a high-power transformer fault may be up to up to ten million dollars, therefore the detection to detection, the especially partial discharge phenomenon of transformer equipment health status is very necessary.Along with the development of power industry, the grade of transformer is more and more higher, and volume is increasing, for the ease of detecting and maintenance, just not only requires the detection to PD, also will realize the location to PD.
Traditional detection to the partial discharge of transformer phenomenon mainly contains the electromagnetic pulse method, chemical method and ultrasonic method.The electric pulse detection method is to use also the most general the earliest a kind of detection method, but is subjected to the influence of electromagnetic interference (EMI) easily, is difficult to control in transformer working site electromagnetic interference (EMI).The chemical detection method mainly is that the content that utilizes gas sensor to detect gas with various in the transformer oil realizes that PD detects.Because shelf depreciation can produce gas with the interaction of oil, these gases can be from discharge source to diffusion all around.But because the coefficient of viscosity of oil is very high, gaseous diffusion is very slow, and from PD occur to abundant gas by sensor to very big delay is arranged, therefore this method is not suitable for being applied in real time on-line monitoring.Because partial discharge phenomenon possibility long-term existence, the infringement that it causes transformer is the process of a long-term accumulation, so gas detection method can be applied to the early stage detection of shelf depreciation.
Traditional supersonic detection method is to utilize piezoelectric transducer to realize that this method is to convert ultrasonic signal to electric signal, also is subjected to the influence of electromagnetic interference (EMI) easily to hyperacoustic detection.
Fibre Optical Sensor is compared with traditional electric transducer has a lot of intrinsic advantages, comprises that volume is little, life-span length, high stability, high sensitivity and anti-electromagnetic interference (EMI), is used widely.And also detected at partial discharge of transformer based on the sonac of optical fiber, aspects such as the fibre optic hydrophone of military field have obtained research and have used.
Summary of the invention
The object of the present invention is to provide propose a kind of simple in structure, make easily, low, the highly sensitive and practical optical fiber extrinsic Fabry-Perot interference ultrasonic sensing detection device of cost, can realize detection to partial discharge phenomenon, and the location that can utilize a plurality of sensing heads and delay inequality detection algorithm to realize discharge source.
In order to achieve the above object, the present invention adopts subordinate's technical scheme: a kind of optical fiber extrinsic Fabry-Perot interference ultrasonic sensing detection device comprises light source, it is characterized in that described light source, connect an optical fiber circulator, an interface of described optical fiber circulator connects an optical fibre Fabry-perot sonac, another interface is connected an oscillograph through a photoelectric conversion module with a signal amplification module, a signal generator connects a piezoelectric transducer, this piezoelectric transducer produces ultrasonic signal, is transferred to described Fabry-Perot sonac; Shown in light source be the 1550nm light source, optical fiber circulator is the 1550nm optical fiber circulator.The light that described 1550nm light source sends imports to described optical fibre Fabry-perot sonac through described 1550nm optical fiber circulator; Described signal generator acts on described piezoelectric transducer and produces ultrasonic signal, and transmission arrives described optical fibre Fabry-perot sonac in air; The described ultrasonic signal that described optical fibre Fabry-perot sonac will receive finally is presented on the described oscillograph by photoelectric conversion module, signal amplification module.
The structure of above-mentioned optical fibre Fabry-perot sonac is: one is inserted in the interior porcelain bushing outer porcelain bushing of overcoat again by single-mode fiber, shown in porcelain bushing and outside the two ends of porcelain bushing metab and quartz vibrating membrane are arranged respectively.The internal face of described single-mode fiber inner face, the medial surface of quartz vibrating membrane, outer porcelain bushing and interior porcelain bushing end face mechanics Fabry-Perot-type cavity; The chamber of described Fabry-Perot-type cavity is long to be the distance that the single-mode fiber end face arrives the quartz vibrating membrane inside surface; The internal diameter of the outer porcelain bushing of described optical fibre Fabry-perot sonac than the external diameter of interior porcelain bushing smaller and make outer porcelain bushing be clamped on the porcelain bushing; Have a slit on the sidewall of described outer porcelain bushing; Described outer porcelain bushing and described interior porcelain bushing utilize the stress deformation of slit to realize the relatively stable of position, and realize the best operating point of Fabry-Perot sonac; The thickness of described quartz vibrating membrane is by the hydrofluorite corrosion control.
Principle of work of the present invention: light is sent by the 1550nm light source, arriving the optical fibre Fabry-perot sensor through optical fiber circulator reflects, when ultrasound wave acts on sensor, reflected light is subjected to hyperacoustic modulation, reflected signal arrives photoelectric conversion module through circulator once more, convert light signal to electric signal, after amplifying, can utilize oscillograph to observe ultrasonic signal.
The present invention has following conspicuous outstanding substantive distinguishing features and remarkable advantage compared with prior art:
(1) have a slit on the outer ceramic wall of optical fibre Fabry-perot sonac, and the internal diameter of outer porcelain bushing be slightly less than in the external diameter (2.5mm) of porcelain bushing, inside and outside porcelain bushing combination tightr under stress;
(2), make that the stability of sensor is improved in the long adjustment process in chamber, and be easy to encapsulation owing to stress between outer porcelain bushing and the interior porcelain bushing;
(3) pick-up unit adopts 1550nm light source cheaply, replaces three-dB coupler with optical fiber circulator, has reduced the loss of light in transmission course;
(4) manufacturing process of sensor is simple, convenient, and the cycle is short, is convenient to produce in batches;
(5) this pick-up unit function admirable not only can be applied to the detection and localization of partial discharge of transformer, can also be applied to association areas such as commercial production, electric power safety.
Description of drawings
Fig. 1 is a systematic schematic diagram of the present invention.
Fig. 2 is an optical fibre Fabry-perot sonac structural representation.
Fig. 3 is the sensor cross-section synoptic diagram.
Embodiment
A preferred embodiment accompanying drawings involved in the present invention is as follows:
Embodiment one: referring to Fig. 1, this optical fibre Fabry-perot ultrasonic sensing and detection device comprises: light source 1, described light source 1, connect an optical fiber circulator 2, an interface of described optical fiber circulator 2 connects an optical fibre Fabry-perot sonac 3, another interface is connected an oscillograph 6 through a photoelectric conversion module 4 with a signal amplification module 5, a signal generator 9 connects a piezoelectric transducer 7, this piezoelectric transducer produces ultrasonic signal 8, is transferred to described Fabry-Perot sonac 3; Shown in light source 1 be the 1550nm light source, optical fiber circulator 2 is the 1550nm optical fiber circulator.
Embodiment two: referring to Fig. 2, above-mentioned present embodiment is identical with embodiment one, special feature is as follows: the basic structure of optical fibre Fabry-perot sonac is: one is inserted in the interior porcelain bushing 14 outer porcelain bushing 13 of overcoat again by single-mode fiber 10, shown in porcelain bushing 14 and outside the two ends of porcelain bushing 13 metab 15 and quartz vibrating membrane 11 are arranged respectively.The medial surface of described single-mode fiber 10 inner faces, quartz vibrating membrane 11, the internal face of outer porcelain bushing 13 and interior porcelain bushing 14 end face mechanics Fabry-Perot-type cavities 12; The long distance that arrives quartz vibrating membrane 11 inside surfaces for single-mode fiber 10 end faces in the chamber of described Fabry-Perot-type cavity; The internal diameter of the outer porcelain bushing 13 of described optical fibre Fabry-perot sonac 3 than the external diameter of interior porcelain bushing 14 smaller and make outer porcelain bushing 13 be clamped on the porcelain bushing 14; Have a slit 16 on the sidewall of described outer porcelain bushing 13; Described outer porcelain bushing 13 utilizes the stress deformation of slit 16 to realize the relatively stable of position with described interior porcelain bushing 14, and realizes the best operating point of Fabry-Perot sonac; The thickness of described quartz vibrating membrane 11 is by the hydrofluorite corrosion control.
Referring to Fig. 3, have a slit on the sidewall of the outer porcelain bushing in the Fabry-Perot sonac.
Principle of work: the light that 1550nm light source 1 sends arrives optical fiber FP sonac 3 through 1550nm optical fiber circulator 2.Because the effect of signal generator 9, piezoelectric transducer 7 sends ultrasound wave 8, and ultrasound wave 8 acts on the vibration that optical fiber FP sonac 3 causes quartz vibrating membrane 11, causes chamber the changing of long hair in FP chamber 12.The end face that incident light arrives I/O single-mode fiber 10 produces Fresnel reflection (less than 4%) the formation first bundle reflected light, and remaining light goes into to inject FP chamber 12.The inside surface generation that incident light arrives quartz vibrating membrane 11 reflects to form the second bundle reflected light.Because the effect of ultrasound wave 8 makes FP chamber 12 chamber changing of long hair, such second restraints catoptrical light path changes, and its phase place changes accordingly.Such second bundle reflected light is exactly the light of being modulated by ultrasound wave 8, and it has carried the relevant information of ultrasound wave 8.The second bundle reflected light is caught by single-mode fiber 10 and is entered inside of optical fibre, interferes with the first bundle reflected light, forms interference light.Interference light is converted electric signal through 1550nm optical fiber circulator 2 by photoelectric conversion module 4 along Optical Fiber Transmission, has realized the demodulation to ultrasonic signal, is presented at oscillograph 6 at last through signal amplification module 5 again.