CN102426279B - All-optical high-voltage voltage transformer - Google Patents

Abstract

The invention proposes an all-optical high-voltage voltage transformer, which includes a high-voltage induction device on the high-voltage side, a shielding insulation device, a sensor head and a photoelectric unit on the low-voltage side. The light emitted from the light source is divided into two beams through the optical path. The intersecting linearly polarized light is transmitted to the sensor head through the polarization-maintaining optical fiber; under the action of the electric field, the sensor head makes the two beams of linearly polarized light produce a phase difference, and the vibration directions of the two beams of linearly polarized light are rotated by 90° respectively. Realize its mode interchange; the two beams of linearly polarized light returned from the sensor head are transmitted back to the optical path part for interference through the polarization maintaining fiber, and then the circuit part detects the interference light intensity signal and performs signal processing to form a digital signal output . The transformer can completely isolate the high and low voltage sides, has the advantages of high safety, strong anti-interference ability, small size, light weight, simple structure, etc., and is easy to realize networking and digitalization; wide frequency response, large dynamic range, High measurement accuracy.

Description

An all-optical high-voltage voltage transformer

technical field

The invention belongs to the field of voltage transformers, in particular to an all-optical high-voltage voltage transformer structure.

Background technique

With the development of science and technology, more and more power systems need to be in high-voltage or ultra-high-voltage environments. It is very unsafe to measure their voltage signals artificially, so voltage transformers play a very important role in power systems. It is one of the indispensable basic test equipment for power system monitoring. Usually, the primary side of the voltage transformer is connected to the primary system (for example: high-voltage line), and the secondary side is connected to measuring instruments, relay protection equipment, etc. At present, voltage transformers mainly include electromagnetic type and non-electromagnetic type (such as: electronic type, photoelectric type), the most widely used is the traditional electromagnetic induction voltage transformer, and the capacitor voltage divider type is also used in some ultra-high voltage fields. Transformer. With the growth of power demand and the continuous improvement of power quality requirements, the power system is developing towards the trend of ultra-high voltage and large capacity. This traditional voltage transformer has increasingly exposed its shortcomings in the safe operation of the power system, improving the accuracy of electric energy measurement and improving the automation of the power system: for example, it is difficult to insulate under high voltage and ultra-high voltage, and the insulation structure is complicated; The transformer connected to the power grid is equivalent to a nonlinear inductive load. Under certain conditions, ferromagnetic resonance may occur between it and the system capacitance, and there are ferromagnetic saturation and ferromagnetic resonance phenomena, resulting in waveform distortion and large linearity errors. ; The body of the transformer is filled with oil, and there is a potential danger of explosion; it has defects such as bulky size and amazing quality.

In the prior art, some optical voltage transformers are also disclosed. Compared with traditional electromagnetic voltage transformers, although they have signals transmitted by optical signals, their insulation performance is good; they do not contain iron cores, are less affected by electromagnetic interference, and have no iron cores. Magnetic resonance, magnetic saturation and hysteresis caused by large inductance; measurement frequency bandwidth, large dynamic range, closed-loop control without the danger of high voltage caused by open circuit, etc. However, due to its structural defects, there are still many problems: for example, the isolation of the high and low voltage sides increases the length of the light transmission path, which introduces optical path noise and interference; due to the lack of effective insulation of the high and low voltage side structures, if directly exposed to the air Improper neutralization or insulation treatment not only poses safety hazards, but also causes deviations in the measurement structure due to external interference; in addition, the structure of the photoelectric unit can be made more compact and the operation is more convenient through structural improvement.

Contents of the invention

In order to overcome the above-mentioned defects of the prior art, the object of the present invention is to propose an all-optical high-voltage voltage transformer capable of completely isolating the high-voltage and low-voltage sides, with high safety, strong anti-interference ability, simple structure and convenient operation.

The all-optical high-voltage voltage transformer of the present invention is realized through the following technical scheme:

An all-optical high-voltage voltage transformer, the transformer includes a sensing unit on the high-voltage side and a photoelectric unit on the low-voltage side, the sensing unit and the photoelectric unit are connected through a polarization-maintaining optical fiber, characterized in that:

The sensing unit includes a high voltage induction device, a shielding insulation device and a sensing head, the high voltage induction device induces a high voltage potential from a high voltage line and forms a stable electric field in the shielding insulation device, and the sensing head is placed in the electric field;

The photoelectric unit includes an optical path part and a circuit part placed in the secondary case;

The light emitted from the light source is divided into two beams of orthogonal linearly polarized light through the optical path, and then transmitted to the sensor head through the polarization maintaining fiber; the sensor head makes the two beams of linearly polarized light pass through the sensor head under the action of the electric field phase difference After the two beams of linearly polarized light are reflected and pass through the sensor head again, the total phase difference is And the vibration directions of the two beams of linearly polarized light are rotated by 90° respectively to realize their mode exchange; the two beams of linearly polarized light returned from the sensor head are transmitted back to the optical path part through the polarization maintaining fiber for interference, and then detected by the circuit part After interfering with the light intensity signal and performing signal processing, a digital signal output is formed.

Wherein, the high-voltage induction device includes a metal guide rod and a pressure equalizing ball, and the metal guide rod induces a high-voltage potential from a high-voltage line, and extends the lower part of the metal guide rod carrying the high-voltage potential into the shielding insulation device, and the metal guide rod The lower end is provided with a pressure equalizing ball.

Wherein, the shielding and insulating device includes a sealed cylindrical shielding device, and the inside of the shielding device is filled with SF ₆ gas for insulation.

Wherein, the sensor head includes a collimator lens, a Faraday rotator and an electro-optic crystal, and the two opposite surfaces of the Faraday rotator are respectively bonded to the light incident surface of the collimator lens and the electro-optic crystal, on the electro-optic crystal, and The other surface opposite to the light incident surface is coated with a reflective film, and the upper and lower end surfaces of the electro-optic crystal are respectively equipped with electrodes.

Wherein, the polarization-maintaining optical fiber and the sensing head are made of insulating materials, and the sensing head is placed on one side of the metal guide rod.

Wherein, the polarization directions of the two orthogonal linearly polarized lights are rotated by 45° each time they pass through the Faraday rotator.

Among them, the two beams of orthogonal linearly polarized light obtained from the optical path in the secondary cabinet are respectively transmitted along the X-axis and Y-axis of the polarization-maintaining fiber, and after passing through the 45° Faraday rotator, the polarization directions of the two beams are all in the same direction After being rotated by 45°, it is incident into the electro-optic crystal, and the electro-optic crystal produces a linear electro-optic effect under the action of an electric field, making the two beams of linearly polarized light produce a phase difference When the two beams of light are reflected by the reflective film arranged on the end face of the electro-optic crystal, the two beams of light pass through the electro-optic crystal again, and the phase difference is doubled, that is, the total phase difference is After passing through the Faraday rotator, the polarization directions of the two beams of light are rotated by 45° on the basis of the previous rotation, that is, the two beams of light are rotated by 90°; at this time, the linear polarization transmitted along the X-axis of the polarization-maintaining fiber The light becomes transmitted along the Y-axis of the polarization-maintaining fiber, and the linearly polarized light initially transmitted along the Y-axis of the polarization-maintaining fiber becomes transmitted along the X-axis of the polarization-maintaining fiber, that is, the exchange of the two light modes is realized.

Wherein, the phase difference generated by the two beams of linearly polarized light Among them, l is the length of the electro-optic crystal in the direction of light propagation, d is the thickness of the electro-optic crystal in the direction of the applied electric field, n ₀ is the refractive index of the electro-optic crystal, γ ₄₁ is the electro-optic coefficient of the electro-optic crystal, U is added on the electro-optic crystal Voltage.

Wherein, the optical path part includes a light source, a coupler I, a Y waveguide modulator and a coupler II, and the light emitted from the light source enters the Y waveguide modulator after being coupled by the coupler I, and is divided into two parts in the Y waveguide modulator. A beam of orthogonal linearly polarized light, the two beams of light are coupled by the coupler II and enter the polarization maintaining fiber and then transmitted to the sensor head; Returning, after being coupled by the coupler II, interference occurs at the Y waveguide modulator, and the interference light intensity signal after the interference is coupled by the coupler I, and then enters the circuit part for signal processing.

Wherein, the circuit part includes:

The photodetector is used to detect the interference light intensity signal sent by the optical path part, and convert the signal into an analog voltage signal, and send it to the analog-to-digital converter;

Analog-to-digital converter, which converts the analog voltage signal into a discrete digital signal and sends it to the digital signal processing unit;

A digital-to-analog converter converts the digital staircase wave generated by the digital signal processing unit into an analog staircase wave;

a driving circuit for driving the Y-waveguide modulator that the analog staircase wave is applied to the optical path; and

The digital signal processing unit is used for data demodulation of the digital signal. Through the integral control algorithm, the step height of the step wave is generated, and the digital step wave is formed through accumulation, and sent to the digital-analog converter to be converted into an analog step wave, and passed through the drive circuit. Applied to the Y waveguide modulator of the optical path to realize closed-loop control; the digital signal processing unit is also used to generate a modulated square wave, which is converted into an analog square wave by a square wave drive circuit, and then superimposed with an analog ladder wave , and then applied to the Y waveguide modulator of the optical path; the digital signal processing unit is also used to smooth and filter the digital signal to form a digital signal output.

Wherein, the digital signal processing unit includes a digital signal processor (hereinafter referred to as DSP) and a field programmable gate array (hereinafter referred to as FPGA).

The beneficial effects of the present invention are:

1. The transformer of the present invention uses optical elements as the sensing head on the high-voltage side, and the photoelectric unit is placed in the secondary chassis on the low-voltage side, and the signal is transmitted through the polarization-maintaining optical fiber in the middle, which greatly simplifies the insulation structure and realizes high-voltage and low-voltage The complete isolation of the transformer side has the advantages of high safety, small size, light weight, etc., and it is easy to realize networking and digitalization; and there is no iron core in the transformer, and there are no problems such as magnetic saturation and ferromagnetic resonance.

2. In the shielding device of the present invention, SF ₆ gas is used as the insulating medium, which will not cause dangers such as fire and explosion; both the sensing head and the polarization-maintaining optical fiber are made of insulating materials and are small in size, which greatly simplifies the insulating structure and realizes high, The complete isolation of the low-voltage side provides high safety.

3. The sensor head of the present invention is mainly composed of Faraday rotator and electro-optic crystal, which is small in size and light in weight, and is convenient for on-site use. In addition, by coating a reflective film on one side of the electro-optic crystal, the use of the reflective film The reflective optical path and the optical rotation effect of the Faraday rotator realize the reciprocity of the optical path in the transformer, so that the optical path has a high anti-interference ability.

4. The photoelectric unit of the present invention has the advantages of wide frequency response, large dynamic range, fast response speed, digital output, and high measurement accuracy.

Description of drawings

Fig. 1 is the structural representation of all-optical high-voltage voltage transformer of the present invention;

Fig. 2 is a structural schematic diagram of a sensing head;

Fig. 3 is a schematic diagram of the structural principle of the optical path part;

Fig. 4 is a schematic diagram of the structural principle of the circuit part;

In the figure, 1-polarization maintaining fiber, 2-metal guide rod, 3-pressure equalizing ball, 4-shielding device, 5-Faraday rotator, 6-electro-optic crystal, 7-reflective film, 8-electrode, 9-secondary Chassis, 10-light source, 11-coupler I, 12-Y waveguide modulator, 13-coupler II, 14-photodetector, 15-analog-to-digital converter, 16-digital signal processing unit, 17-digital-to-analog conversion device, 18-drive circuit, 19-high voltage line, 20-sensor head, 21-collimator lens, 22-square wave drive circuit.

Detailed ways

The all-optical high-voltage transformer of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The all-optical high-voltage voltage transformer of the present invention is mainly composed of three parts: a sensing unit on the high-voltage side, a photoelectric unit on the low-voltage side, and a polarization-maintaining optical fiber connecting the sensing unit and the photoelectric unit.

As shown in Figure 1, the sensing unit includes a high voltage sensing device, a shielding insulation device and a sensing head.

The high-voltage induction device includes a metal guide rod 2 and a pressure equalizing ball 3, and the shielding and insulating device includes a sealed cylindrical shielding device 4 and SF ₆ gas filled in the shielding device for insulation. The metal guide rod 2 senses the high-voltage potential from the high-voltage line 18, and extends the lower part of the metal guide rod 1 carrying the high-voltage potential into the shielding device 4. The lower end of the metal guide rod is installed with a pressure equalizing ball 3, and the shielding device is filled with SF ₆ gas for insulation , a stable electric field will be generated inside the closed space.

The sensor head is fixed on one side of the metal guide rod 2 located inside the shielding device, as shown in Figure 2, the sensor head is mainly composed of a collimator lens 21, a Faraday rotator 5 and an electro-optic crystal 6, and the two parts of the Faraday rotator 5 Two opposite surfaces are respectively bonded on the front end face (i.e. the light incident face) of the collimating lens 21 and the electro-optic crystal 6, on the electro-optic crystal, the rear end face relative to the front face is coated with a reflective film 7, on the electro-optic crystal 6, Electrodes 8 are respectively installed on the lower end faces. The electrode 8 of the electro-optic crystal senses the potential in the electric field and adopts lateral modulation, that is, the direction of the electric field applied to the electro-optic crystal 6 is perpendicular to the direction of light propagation. The working principle of the sensing head is: two beams of orthogonal linearly polarized light obtained by the optical path part in the secondary chassis 9 are respectively transmitted along the X-axis and the Y-axis of the polarization-maintaining fiber, and after passing through the 45° Faraday rotator 5, The polarizations of both beams are rotated 45 degrees in the same direction. Then they are incident into the electro-optic crystal 6, and the electro-optic crystal produces an electro-optic effect under the action of an external electric field, so that the two beams of light have a certain phase difference Among them, l is the length of the crystal in the direction of light propagation, d is the thickness of the crystal in the direction of the applied electric field, n ₀ is the refractive index of the crystal, γ ₄₁ is the electro-optic coefficient of the crystal, and U is the voltage applied to the crystal. After being reflected by the reflective film 7, the two beams of light pass through the electro-optic crystal 6 again, and the phase difference is doubled, that is, the total phase difference is The two beams of light pass through the Faraday rotator 5 again after exiting the electro-optic crystal 6. According to the non-reciprocity of the Faraday effect, the vibration directions of the two beams of light are rotated 45 degrees along the previous rotation direction, so that they rotate 90 degrees respectively. At this time, the light originally propagating along the X-axis of the polarization-maintaining fiber is changed to propagate along the Y-axis of the polarization-maintaining fiber, and the light originally propagating along the Y-axis of the polarization-maintaining fiber is now propagated along the X-axis of the polarization-maintaining fiber, realizing the interaction of modes Change. Then it is transmitted back by the polarization-maintaining optical fiber 1, and the optical path part and the circuit part in the secondary cabinet 9 acquire the interference light intensity of the two beams of light and perform detection and signal processing. Because the two beams of light that interfered have passed through the X-axis and Y-axis of the polarization-maintaining fiber during the optical transmission process, but there is a slight difference in time, so the light returning to the photodetector only carries the electro-optic crystal to them phase modulation information.

The photoelectric unit on the low-voltage side includes an optical path part and a circuit part placed in the secondary case 9 .

As shown in Figure 3, the optical path is mainly composed of a light source 10, a coupler I 11, a Y waveguide modulator 12 and a coupler II 13. The working principle is: the light emitted by the light source 10 enters the Y-waveguide modulator 12 after passing through the coupler 111. The Y-waveguide modulator is also called an integrated optical phase modulator, which is a multifunctional device consisting of a Y-shaped beam splitter and Composed of two phase modulators, the use of the Y waveguide modulator can make the mechanism of the optical path part more compact, reduce the volume of the secondary cabinet, and make the operation more convenient. The light entering the Y waveguide is divided into two beams by the Y-type beam splitter, and modulated by two phase modulators into two beams of orthogonal linearly polarized light. These two beams of linearly polarized light enter the polarization-maintaining fiber 1 through the coupler II 13 , the two transmission modes along the polarization-maintaining fiber 1 are transmitted to the sensing head. After passing through the sensor head, the two beams of linearly polarized light carrying the voltage information to be measured return along the original optical path, interfere at the Y waveguide modulator 12, and then are coupled into the photodetector 14 of the circuit part by the coupler I11, and Signal processing is carried out in the circuit part.

As shown in FIG. 4 , the circuit part is mainly composed of a photoelectric converter 14 , an analog-to-digital converter 15 , a digital signal processing unit 16 , a digital-to-analog converter 17 and a corresponding driving circuit 18 . The signal processing process is: the photodetector 14 detects the interference light intensity signal carrying the voltage information to be measured from the optical path, and converts the signal into a voltage signal, and then transmits it to the analog-to-digital converter 15 to convert the voltage signal into a discrete The digital signal is sent to the digital signal processing unit 16, which is realized by DSP and FPGA. The FPGA demodulates the discrete digital signal, and integrates the demodulation results to generate the step height of the step wave, which is then accumulated to form a digital step wave, which is sent to the digital-to-analog converter 17 for conversion into an analog step wave, and passed through the drive circuit 18 Applied to the Y waveguide modulator 12 of the optical path part to realize closed-loop control; the FPGA also produces a modulated square wave, which is converted into an analog square wave by the square wave drive circuit 22, and after the analog square wave is superimposed with the above-mentioned analog ladder wave, it is applied to the Y waveguide modulator 12; in addition, the DSP performs smoothing and filtering on the demodulated data of the FPGA, and the digital signal is output by the FPGA. After that, the existing measuring equipment can be used to indirectly measure the voltage information to be measured, that is, the magnitude of the electric field, by measuring the output digital signals of the two beams of light.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: the present invention can still be Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention shall be covered by the scope of the claims of the present invention.

Claims (8)

1. a full optical high-voltage voltage transformer, this mutual inductor comprises the photovoltaic element being positioned on high-tension side sensing unit He being positioned at low-pressure side, and described sensing unit is connected by polarization maintaining optical fibre (1) with photovoltaic element, it is characterized in that:

Described sensing unit, comprises high voltage induction device, shielding insulation device and sensing head, and described high voltage induction device is responded to high-voltage potential from hi-line and form consistent electric field shielding insulation device, and described sensing head is placed in this electric field;

Described photovoltaic element, comprises the light path part and circuit part that are placed in secondary cabinet (9);

The light sent from light source is divided into the orthogonal linearly polarized light of two bundles through light path part and reaches sensing head by polarization maintaining optical fibre; Described sensing head, under the effect of electric field, makes two bunch polarized lights by producing phase differential after sensing head two bunch polarized lights are through reflection again by after sensing head, and total phase differential is and the direction of vibration of two bunch polarized lights is half-twist respectively, realizes its modes swap; The two bunch polarized lights returned from described sensing head are transmitted back to light path part by polarization maintaining optical fibre interferes, then detects interference light intensity signal by circuit part and after carrying out signal transacting, form digital signal and export;

Described high voltage induction device comprises metal guide rod (2) and voltage equalizing ball (3), described metal guide rod responds to high-voltage potential from hi-line, stretch in shielding insulation device by metal guide rod (2) bottom being loaded with high-voltage potential, the lower end of described metal guide rod is provided with voltage equalizing ball (3);

Described shielding insulation device comprises the cylindrical shield device (4) of sealing, and described shield assembly (4) inside is filled with SF ₆gas insulate;

Described circuit part comprises:

Photodetector (14), for detecting interference light intensity signal that light path part sends and this signal being converted to analog voltage signal, delivers to analog to digital converter (15);

Analog to digital converter (15), sends into digital signal processing unit (15) after analog voltage signal is converted to discrete digital quantity signal;

Digital to analog converter (17), is converted to analogue step ripple by the digital staircase that digital signal processing unit produces;

Driving circuit (18), drives analogue step ripple to be applied to the Y waveguide modulator (12) of light path part; And

Digital signal processing unit (16), for carrying out data demodulates to digital quantity signal, after Integral Processing, produce staircase waveform bench height, digital staircase is formed through cumulative, and deliver to digital analog converter (17) and be converted to analogue step ripple, be applied to the Y waveguide modulator (12) of light path part through overdrive circuit (18), realize closed-loop control; Described digital signal processing unit (16) is also for generation of modulated square wave, this modulated square wave converts simulation square wave to through square wave driving circuit (22), superpose with analogue step ripple again, be then applied to the Y waveguide modulator (12) of light path part; Described digital signal processing unit (16) also for after the smoothing filtering of digital quantity signal, forms digital signal and exports.

2. full optical high-voltage voltage transformer as claimed in claim 1, it is characterized in that: described sensing head comprises collimation lens (21), Faraday mirror (5) and electro-optic crystal (6), two opposite faces of described Faraday mirror (5) are bonded in the light entrance face of collimation lens (21) and electro-optic crystal (6) respectively, on electro-optic crystal, on relative with light entrance face another side, be coated with reflectance coating (7), the upper and lower end face of described electro-optic crystal (6) is separately installed with electrode (8).

3. full optical high-voltage voltage transformer as claimed in claim 2, is characterized in that: described polarization maintaining optical fibre and sensing head adopt insulating material to make, and described sensing head is placed in the side of metal guide rod (2).

4. full optical high-voltage voltage transformer as claimed in claim 2, is characterized in that: described two restraint orthogonal linearly polarized light at every turn when Faraday mirror (5), and its polarization direction all rotates 45 °.

5. full optical high-voltage voltage transformer as claimed in claim 2, it is characterized in that: obtained by the light path part in secondary cabinet (9) two restraint orthogonal linearly polarized light respectively along X-axis and the Y-axis transmission of polarization maintaining optical fibre, through 45 ° of Faraday mirrors (5), incide in electro-optic crystal (6) after the polarization direction of two-beam rotates 45 ° all in the same direction, electro-optic crystal produces linear electro-optic effect under electric field action, makes two bunch polarized lights produce phase differential be arranged at reflectance coating (7) reflection on electro-optic crystal end face when two-beam after, two-beam is again through electro-optic crystal, and phase differential doubles, and namely total phase differential is again through Faraday mirror (5), the polarization direction of two-beam along rotating 45 ° again on previous postrotational basis, and namely two-beam have rotated 90 ° separately; Now, the Y-axis become along polarization maintaining optical fibre along the linearly polarized light of polarization maintaining optical fibre X-axis transmission is at first transmitted, and the X-axis become along polarization maintaining optical fibre along the linearly polarized light of polarization maintaining optical fibre Y-axis transmission is at first transmitted, and namely achieves the exchange of two-beam pattern.

6. the full optical high-voltage voltage transformer as described in claim 1 or 5, is characterized in that:

The phase differential that described two bunch polarized lights produce

Wherein, l is the length of electro-optic crystal on optical propagation direction, and d is the thickness of electro-optic crystal on extra electric field direction, n ₀the refractive index of electro-optic crystal, γ ₄₁be the electrooptical coefficient of electro-optic crystal, U is the voltage be added on electro-optic crystal.

7. full optical high-voltage voltage transformer as claimed in claim 1, it is characterized in that: described light path part comprises light source (10), coupling mechanism I (11), Y waveguide modulator (12) and coupling mechanism II (13), the light sent from described light source (10) enters Y waveguide modulator (12) after coupling mechanism I (11) coupling, in Y waveguide modulator, be divided into the linearly polarized light that two bundles are orthogonal, this two-beam enters polarization maintaining optical fibre (1) and reaches sensing head after coupling mechanism II (13) coupling; After sensing head, the two-beam carrying information of voltage to be measured returns along polarization maintaining optical fibre again, be coupled through coupling mechanism II (13), interfere at Y waveguide modulator (12) place, interference light intensity signal after interfering, via after coupling mechanism I (11) coupling, enters circuit part and carries out signal transacting.

8. full optical high-voltage voltage transformer as claimed in claim 1, is characterized in that: described digital signal processing unit (16) comprises digital signal processor (DSP) and field programmable gate array (FPGA).