CN106324323B - An all-fiber-optic current transformer and its current measuring method - Google Patents

Abstract

The invention provides an all-fiber current transformer and its current measurement method, which mainly consists of three parts: a sensing unit, a signal processing unit and a combining unit. The sensing unit adopts the principle of Faraday's magneto-optic effect to sense the current of the conductor under test, and generate a light intensity signal carrying the data information of Faraday's optical rotation angle. The signal processing unit mainly completes the input of the optical signal of the sensing unit, the analysis of the output optical signal, digital processing, temperature compensation, etc., and outputs according to the specified synchronous serial mode. The merging unit completes the synchronization, switching or parallel logic of the information of the signal processing unit, and transmits it to the electrical measuring instrument and the relay protection equipment.

Description

An all-fiber-optic current transformer and its current measuring method

【Technical field】

The invention relates to an all-fiber current transformer based on the Faraday magneto-optical effect principle. It is suitable for electric energy metering, relay protection and power monitoring of GIS.

【Background technique】

The current transformer is responsible for the measurement of the current in the power system. As an important part of GIS, the traditional electromagnetic current transformer can no longer meet the smart grid's low cost of current transformer due to its large size, high cost, small dynamic range, easy to generate ferromagnetic resonance, analog output and other unfavorable factors. , small size, good linearity, digital output, safe and reliable requirements. The application of active electronic transformers in switches of 126-252kV voltage level is becoming more and more reliable. Although it has the advantages of small size, digital output, and no magnetic saturation, due to the limitations of its structure and principle, it cannot be used at higher voltage levels. The reliability of the grid is greatly reduced, affecting the reliable operation of the smart grid.

【Content of invention】

The invention provides an all-fiber current transformer and its current measurement method, which can effectively solve the disadvantages of traditional electromagnetic transformers such as large volume, small dynamic range, easy ferromagnetic resonance, high voltage generated by open circuit, and analog output, etc. The shortcomings of active electronic transformers such as poor anti-interference, complex structure, and poor stability are eliminated. Meet the smart grid's requirements for low energy consumption, high accuracy, safety and reliability of current transformers.

To achieve the above object, the present invention adopts the following technical solutions:

An all-fiber current transformer based on the principle of Faraday's magneto-optic effect, including a sensing unit, a signal processing unit, and a merging unit, the merging unit is connected with an electrical measuring instrument and a relay protection device, and the sensing unit includes a winding The sensing fiber is made into a closed ring connected end to end. The head and tail of the sensing fiber are respectively fused with a reflector and a conversion fiber. The signal processing unit is provided with a light source, and the light emitted by the light source is divided into two beams. Afterwards, the conversion fiber is converted into two beams of light with opposite rotation directions, which are reflected by the mirror after being transmitted in the sensing fiber.

The conversion optical fiber is a helical birefringent optical fiber, which is divided into an increasing double helix section and a uniform double helix section.

The reflector is welded to the end of the sensing fiber, forming an angle of 45° with the cross section of the sensing fiber.

The sensing optical fiber is installed in the U-shaped groove of the annular flange, and the reflection mirror and the conversion optical fiber are parallel to each other in the tangential direction of the U-shaped groove.

The reflector and the conversion optical fiber are closely arranged along the normal direction of the ring structure.

The other end of the conversion fiber is electrically connected to the signal processing unit through a polarization maintaining fiber.

The annular flange is made of metal material, and the upper part is covered with an annular cover plate of insulating material, which blocks the induction current of the annular flange.

The number of turns of the sensing optical fiber in the protection ring is determined according to the magnitude of the measured current, the accuracy required by the transformer and the size of the ring.

The signal processing unit includes an optical circuit module, a circuit module, a power supply module and a protective casing, the optical circuit module is used to transmit, receive and measure optical signals, and outputs the phase difference of two beams of light, and the circuit module is used to analyze the two beams of light The phase difference is used to calculate the current and output the result as a digital signal.

The optical path module includes a laser emitter that emits a light source, a coupler that couples the light emitted by the light source, a polarizer that divides the light source into two beams of linearly polarized light, and a modulator connected to the polarizer, for the two beams of light Light source detector for interferometry.

The circuit module includes sequentially connected signal processing and digital output, wherein the input end of the signal processing is further connected with temperature compensation to eliminate the influence of temperature on measurement deviation.

The digital output outputs the measurement structure to the merging unit in a synchronous serial manner.

The protective casing is made of ferromagnetic material, and has corresponding levels of anti-electromagnetic shielding, waterproof, and moisture-proof functions for the optical path module, circuit module, and power module placed therein, and has installation and data output and input interfaces.

A current measurement method of an all-fiber current transformer. The continuous light emitted by the light source is divided into two beams of light whose polarization directions are perpendicular to each other. After receiving the light, the conversion fiber converts the two vertical linearly polarized lights into left-handed and right-handed The elliptically polarized light propagates around the circumference in the sensing fiber, and the two polarized lights are reflected by the mirror, and the rotation direction of the two elliptically polarized lights is also reversed; the two reflected lights return to the conversion fiber and are converted Two paths of mutually perpendicular linearly polarized light beams are finally restored to two paths of mutually perpendicularly polarized light beams. After the two paths of light beams are sent back to the signal processing unit, the signal processing unit calculates the current accordingly.

The signal processing unit calculates the phase difference according to the phase difference of the returned two beams of light.

Compared with the prior art, the present invention has at least the following beneficial effects: the all-optical current transformer has low energy consumption, low cost, accurate measurement, stable performance, safety and reliability, easy installation and maintenance, and avoids high energy consumption of electromagnetic transformers, It is easy to produce the disadvantages of open circuit and explosion hazard, and at the same time, it eliminates the disadvantages of electronic transformers, such as stable phase difference and susceptibility to electromagnetic field interference.

【Description of drawings】

Fig. 1 shows the structural diagram of the sensing unit in the present invention.

Fig. 2 shows the structure diagram of sensing unit A-A in the present invention.

Fig. 3 is a system diagram of an all-fiber current transformer in the present invention.

In the figure: 1. Ring-shaped cover plate; 2. Ring-shaped flange; 3. Sensing fiber; 4. Conversion fiber; 5. Reflector; 6. Polarization-maintaining fiber.

【Detailed ways】

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific examples.

An all-fiber-optic current transformer based on Faraday's magneto-optical effect principle, which is mainly composed of a sensing unit, a signal processing unit and a merging unit. The sensing unit adopts the Faraday magneto-optic effect principle to sense the current of the conductor under test, generate a light intensity signal and carry the data information of the Faraday optical rotation angle. The signal processing unit mainly completes the input of the optical signal of the sensing unit, the analysis of the output optical signal, digital processing, temperature compensation, etc., and outputs according to the specified synchronous serial mode. The merging unit completes the synchronization and parallel logic of the information of the signal processing unit, and transmits it to the electrical measuring instrument and the relay protection equipment.

Fig. 1, 2 show the structural diagram of sensing unit among the present invention, and described sensing unit is ring-type structure, and it is mainly made of annular cover plate 1, annular flange 2, sensing optical fiber 3, conversion optical fiber 4. The reflector 5 and the polarization maintaining fiber 6 are composed. According to the measured rated current, dynamic stable current, measurement accuracy and the U-shaped groove size of the ring flange 2, the length of the sensing fiber 3 is calculated. One end of 3 is welded with a reflector 5, so that the reflector 5 forms an included angle of 45° with the cross section of the optical fiber. The other end of the sensing fiber 3 is fused with the conversion fiber 4 so that the cores of the two fibers are aligned. At the same time, the other end of the conversion fiber 4 is fused with the polarization-maintaining fiber 6, and the cores of the two are aligned during the fusion. After the welding is completed, it is wound into a closed ring connected end to end and fixed in the U-shaped groove of the ring flange, and the reflector 5 and the conversion optical fiber 3 are parallel to each other in the tangential direction of the U-shaped groove, and along the The tangential direction of the ring structure is arranged close to each other, and the polarization-maintaining optical fiber 6 is used as the lead-out end of the sensing unit to lead out from the exit of the ring-shaped flange 2 to connect with the subsequent data processing unit.

The conversion optical fiber is a helical birefringent optical fiber, which is divided into an increasing double helix section and a uniform double helix section, and converts linearly polarized light into elliptically polarized light; the ring flange is made of metal material, and a U-shaped groove is opened in the middle. The ring made of sensing fiber, reflector and conversion fiber is fixed in the U-shaped groove. The ring cover is made of insulating material, which can block the induced current of the shell. After the two are matched, they are placed in it. The optical device plays a protective role.

Fig. 3 shows the system diagram of the all-optical fiber current transformer in the present invention, and the whole system is divided into three parts according to the functions, which are respectively the sensing unit, the signal processing unit and the merging unit. The sensing unit adopts the Faraday magneto-optic effect principle to sense the current of the conductor under test and generate a light intensity signal carrying the data information of the Faraday optical rotation angle. The signal processing unit mainly completes the input of the optical signal of the sensing unit, the analysis of the output optical signal, digital processing, etc., and outputs according to the specified synchronous serial mode. The merging unit completes the synchronization, switching or parallel logic of the signal processing unit information, and transmits it to electrical measuring instruments and relay protection equipment.

The signal processing unit is mainly composed of an optical path module, a circuit module, a power supply module and a protective shell. The optical path module completes the emission, reception, measurement and output of the optical signal, and the circuit module receives the data information of the optical path module and converts it into a digital signal for output.

The optical path module is mainly composed of optical devices such as a laser transmitter, a coupler, a polarizer, and a photodetector, and emits two beams of linearly polarized light to the sensing unit, and simultaneously uses Sagnac to reflect the two beams of linearly polarized light back. The principle of interference measures the phase difference of two beams of polarized light.

The circuit module, through analyzing the phase difference, corresponds to the measured current, and outputs the measurement result to the merging unit in a synchronous serial manner.

The power supply module converts the externally supplied power into the current or voltage required by each electronic component.

The protective casing is made of ferromagnetic material, and has corresponding levels of anti-electromagnetic shielding, waterproof, and moisture-proof functions for the optical path module, circuit module, and power module placed therein, and has installation and data output and input interfaces.

In Fig. 3, the implementation process of the all-fiber-optic current transformer to measure the current is as follows: the light source in the data processing unit is working, the continuous light emitted by the coupler is polarized by the polarizer into two beams of linearly polarized light, The phase modulation is completed by the modulator and divided into two beams of light whose polarization directions are perpendicular to each other, and output through the polarization-maintaining fiber; at the front end of the sensing fiber of the sensing unit, the conversion fiber converts the two vertical linearly polarized lights into left-handed and right-handed elliptical polarization Light, elliptically polarized light propagates around the circumference in the sensing fiber; after the two polarized lights go around the conductor for several times, there is a reflector at the end of the sensing fiber to reflect the two beams of light, and the two beams of elliptically polarized light The rotation direction of the light is also reversed; the two paths of light return to the conversion fiber, and the conversion fiber converts them into two mutually perpendicular linearly polarized beams, which are transmitted back to the polarizer by the polarization-maintaining fiber, and return to two mutually perpendicular polarizations Light, two beams of light waves are coherently superimposed at the light source detector.

When there is no current in the conductor, the relative propagation speed of the two beams of light is the same, and there is no phase difference when coherently superimposed at the photodetector; when there is current in the conductor, an electromagnetic field will be generated around the current-carrying conductor. Two beams of elliptically polarized light waves touching a current-carrying conductor, due to the principle of Faraday’s magneto-optic rotation effect, the electromagnetic field formed by the current-carrying conductor decelerates one elliptically polarized light, and accelerates the other elliptically polarized light. When the optical signal is reflected back, the acceleration and deceleration effects of the two elliptically polarized lights are doubled due to the reversal. At this time, the propagation speed of the two beams of light changes relative to each other, that is, a phase difference appears.

The phase difference of the two optical signals has a strict correspondence with the measured current. By measuring the phase difference of the two beams of light, the magnitude of the measured current is obtained, and the measurement information is digitally output to the merging unit. The merging unit processes the data The digital information of the unit is digitally converted according to the IEC61850-9-2LE protocol, and output to the relay protection system and the current measuring instrument.

In actual application, the sensing unit is a single-phase structure, each phase is installed outside the measured current, the data processing unit corresponds to the sensing unit one by one, placed on the spot or in a smart cabinet, and the merging unit is shared by three phases Type, placed in the intelligent control cabinet or protection room.

The above content is a detailed description of the present invention in conjunction with specific preferred modes, and it cannot be determined that the embodiments of the present invention are limited thereto. For those of ordinary skill in the technical field of the present invention, any simple modification made according to the spirit of the present invention And equivalent structural transformation or modification, all belong to the scope of patent protection determined by the claims submitted by the present invention.

Claims (8)

1. one kind is based on Faraday magnetooptical effect principle all-fiber current transformator, it is characterised in that: including sensing unit, signal Processing unit and combining unit, the combining unit are connect with electric testing instrument and relay protection device, and the sensing is single Member includes the sensor fibre (3) for turning to end to end close ring, and the head and the tail of the sensor fibre are separately installed with reflecting mirror (5) and upconversion fiber (4) it, is provided with light source in the signal processing unit, after the light which issues is divided into two-beam, warp Upconversion fiber is converted to the opposite two-beam in direction of rotation, after transmitting in sensor fibre, is reflected by a reflector；

The upconversion fiber (4) is helical structure birefringence fiber；

The signal processing unit includes light path module, circuit module, power module, and the light path module is for emitting, receiving With measurement optical signal, the phase difference of two-beam is exported, the circuit module is used to parse the phase difference of two-beam, and calculates with this Electric current, and result is exported with digital signal；

The light path module includes the laser emitter for emitting light source, the coupler coupled to the light that light source issues, by light Source is divided into two bundles the polarizer of linearly polarized photon, the modulator connecting with the polarizer, and the light source of interferometry is carried out to two-beam Detector.

2. a kind of all-fiber current transformator according to claim 1, it is characterised in that: affiliated upconversion fiber includes being incremented by Double helix section and uniform double helix section.

3. a kind of all-fiber current transformator according to claim 1, it is characterised in that: the reflecting mirror (5) and sensing The section of optical fiber (3) is in 45 ° of angles.

4. a kind of all-fiber current transformator according to claim 1, it is characterised in that: the sensor fibre is mounted on ring In the U-lag of shape flange, the reflecting mirror (5) and upconversion fiber (4) are parallel to each other in the tangential direction of U-type groove.

5. a kind of all-fiber current transformator according to claim 1, it is characterised in that: the reflecting mirror (5) and conversion Optical fiber (4) is close to arrangement along the normal direction of ring structure.

6. a kind of all-fiber current transformator according to claim 4, it is characterised in that: the annular flange (2) is Metal material, the ring-like cover board (1) of top covering insulating material, has blocked the induced current of annular flange.

7. a kind of all-fiber current transformator according to claim 1, it is characterised in that: the signal processing unit also wraps Include guard shield；The guard shield, is made of ferromagnetic, to being put into light path module therein, circuit module, power supply mould Block has corresponding anti-electromagnetic shielding, waterproof, moisture-proof function, while there are installation and data outputs, input interface.

8. a kind of current measuring method based on all-fiber current transformator described in claim 1, it is characterised in that: at data The light of the light source sending in unit is managed after coupler, is polarized as two beam linearly polarized photons, modulated device completion phase-modulation And it is divided into the two orthogonal light in beam polarization direction, it is exported by polarization maintaining optical fibre；Upconversion fiber is by two beam vertical linear polarisation light It is converted into left-handed and right-handed elliptical polarization light, elliptically polarized light is circumferentially propagated in sensor fibre；Two-way polarised light is around leading After body has turned several circles, there is a reflecting mirror in the terminal of sensor fibre, two-beam is reflected, while two beam elliptically polarized lights Direction of rotation also reversed；Two-way light returns at upconversion fiber, they are switched to the mutually perpendicular line of two-way again by upconversion fiber Property light beam, polarizer is passed back by polarization maintaining optical fibre, reverts to the mutually perpendicular polarised light of two-way, two-beam wave is detected in light source Coherent superposition occurs at device；

When no current in conductor, the relative propagation velocity of two-beam is identical, does not have phase when coherent superposition at photodetector Potential difference；When there is electric current in conductor, the appearance phase difference of two-beam；The phase difference of two ways of optical signals and tested electric current have stringent Corresponding relationship, the size of the corresponding electric current tested out of phase difference by measuring two-beam.