Partial discharge detection device based on polarization change
By using a polarization-based partial discharge detection device, which combines lithium niobate electro-optic crystal and single-photon detector with periodic polarization structure and silicon photomultiplier tube, the problems of complexity and poor anti-interference ability of traditional detection methods are solved, and high-sensitivity and anti-interference partial discharge detection is achieved.
Patent Information
- Application Number
- CN202511382060.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-25
- Publication Date
- 2025-11-28
AI Technical Summary
Existing technologies are insufficient for highly sensitive detection of partial discharge in power equipment. Traditional optical measurement methods are complex, have poor anti-interference capabilities, and their signals are easily affected by the environment, making it difficult to achieve highly sensitive and anti-interference partial discharge detection.
A partial discharge detection device based on polarization change is adopted, which utilizes lithium niobate electro-optic crystal and single-photon detector to convert polarization change into light intensity signal. Combined with periodic polarization structure and silicon photomultiplier tube, it achieves high sensitivity and anti-interference detection.
It achieves highly sensitive partial discharge detection, has strong anti-interference ability, reduces false alarm rate, and improves detection reliability.
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Figure CN121027758A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of partial discharge detection technology, specifically to a partial discharge detection device based on polarization changes. Background Technology
[0002] Partial discharge is a significant indicator of insulation degradation in power equipment (such as GIS gas-insulated switchgear), and accurate detection of it is crucial to ensuring the safe and stable operation of power systems. Furthermore, traditional optical measurement methods (such as interferometer-based methods) are complex and sensitive to environmental vibrations, constituting current technological bottlenecks. For example, pulsed current technology is mature and reliable with wide bandwidth coverage but poor anti-interference capability and susceptibility to background electromagnetic noise; ultra-high frequency methods can locate the discharge source and have strong resistance to low-frequency interference, but suffer from severe signal attenuation and low sensitivity to non-pulsed partial discharges; ultrasonic sensing can provide three-dimensional positioning and is suitable for external detection of high-voltage conductors without electrical contact, but it suffers from high propagation loss. Therefore, there is an urgent need for a highly sensitive and anti-interference partial discharge detection technology, and quantum optical sensing technology is a novel and innovative technology developed based on this need. Summary of the Invention
[0003] The purpose of this invention is to provide a partial discharge detection technology with high sensitivity and strong anti-interference ability, namely a partial discharge detection device based on polarization change.
[0004] This invention is achieved using the following technical solution:
[0005] A partial discharge detection device based on polarization variation, comprising:
[0006] A laser source, used to generate a laser beam;
[0007] A 45° polarizer is used to modulate the laser beam generated by the laser source into 45° linearly polarized light.
[0008] Lithium niobate electro-optic crystal is used to apply a partial discharge field to the crystal, causing a polarization change in 45° linearly polarized light.
[0009] The periodic polarization structure consists of N segments of periodically arranged ferroelectric domains, which are used to accumulate and amplify polarization changes.
[0010] -45° analyzer: Set to the -45° linear polarization direction, it converts polarization changes into light intensity signals through polarization interference;
[0011] A single-photon detector uses a -45° analyzer to convert the light intensity signal into a TTL pulse signal for output.
[0012] Working principle: In use, the lithium niobate electro-optic crystal is placed at the electrical equipment under test. This technical solution mainly uses the photoelectric properties of the lithium niobate electro-optic crystal to detect partial discharge in the electrical equipment. When insulation defects occur in the electrical equipment, a weak high-frequency electric field is generated. This electric field causes extremely subtle polarization or polarization changes in the laser passing through the crystal (the change is only about one ten-thousandth of that in ordinary measurements). To capture this minute change, the system uses an ultra-high sensitivity single-photon detector, which can detect signals at the single photon level. Specifically, a laser beam is generated by a laser source, then modulated into linearly polarized light by a 45° polarizer, and incident on a lithium niobate electro-optic crystal. Under the action of a partial discharge high-frequency electric field (2-6V / m), the lithium niobate electro-optic crystal generates a micro-polarization rotation θ, which is accumulated and amplified to θ΄=N·θ by a periodic polarization structure. Then, it is converted into a single-photon level light intensity change signal by a -45° analyzer. A single-photon detector captures up to 4 consecutive photon events within 200ns. When the single-photon detector outputs ≥2 photon events within 200ns, it is determined to be a partial discharge; otherwise, it is determined to be the absence of a partial discharge phenomenon.
[0013] The essence of this technology is to utilize the Pockels effect of electro-optic crystals to convert the weak, intangible high-frequency electric field of partial discharge into a change in light polarization that can be measured optically, and further into a signal of light intensity variation. Specifically, a lithium niobate electro-optic crystal is used to convert the partial discharge field into a minute rotation of the laser polarization state, and this signal is extracted using a single-photon detector. Simultaneously, to overcome the bottleneck of weak signal, a periodic polarized crystal structure is introduced to realize the polarization change. Analysis of the accumulated polarization changes allows for the detection of partial discharge, thus completing the optical quantum detection technology.
[0014] Furthermore, the device also includes a silicon photomultiplier tube for independently detecting partial discharge photons. It achieves mutual detection through the time correlation with the single-photon detector signal, which significantly improves detection reliability and reduces the false alarm rate.
[0015] Furthermore, a valid partial discharge event is determined when the time difference between the output signal of the single-photon detector and the output signal of the silicon photomultiplier tube is less than 100 ns.
[0016] Furthermore, the laser wavelength of the laser source is 550nm.
[0017] Furthermore, the time resolution of the single-photon detector is 60 ns.
[0018] The beneficial effects of this invention are as follows: This scheme utilizes an electro-optic crystal to convert the partial discharge field into a weak shift in laser polarization, and extracts this signal using a single-photon detector (SPCM). To overcome the bottleneck of weak signal, a periodic polarized crystal structure is introduced to achieve polarization change. By analyzing the polarization change, the detection of partial discharge is obtained, thus completing the photonic quantum detection technology, which has high measurement sensitivity and strong anti-interference ability. Attached Figure Description
[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.
[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] Figure 1 This is a schematic diagram of the partial discharge detection device based on the principle of polarization interference of the present invention.
[0022] In the diagram: 1-Laser source, 2-45° polarizer, 3-Lithium niobate electro-optic crystal, 4-45° analyzer, 5-Single-photon detector, 6-Silicon photomultiplier tube. Detailed Implementation
[0023] To better understand the above-mentioned objectives, features, and advantages of the present invention, the solutions of the present invention will be further described below. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.
[0024] In this description, it should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. It should also be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linkage" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.
[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention, but the invention may also be practiced in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of the invention, and not all embodiments.
[0026] The specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings.
[0027] like Figure 1 As shown, a partial discharge detection device based on polarization variation includes:
[0028] Laser source 1, used to generate a laser beam;
[0029] 45° polarizer 2 is used to modulate the laser beam generated by the laser source into 45° linearly polarized light;
[0030] Lithium niobate electro-optic crystal 3 is used to apply a local discharge field to the crystal, causing a polarization change in 45° linearly polarized light;
[0031] The periodic polarization structure consists of N segments of periodically arranged ferroelectric domains, which are used to accumulate and amplify polarization rotation.
[0032] -45° Analyzer 4: Set to -45° linear polarization direction, converting polarization rotation into light intensity signal;
[0033] The single-photon detector 5 detects the light intensity signal converted by the -45° analyzer and converts it into a TTL pulse signal for output.
[0034] Detailed principle analysis:
[0035] 1. Electro-optic modulation detection
[0036] (1) Utilizing the Pockels effect of lithium niobate electro-optic crystal: the high-frequency electric field of partial discharge (E=2~6V / m) causes the light passing through the crystal to undergo polarization changes.
[0037] (2) Generation of polarization change
[0038] When a beam of linearly polarized light at 45° propagates in a crystal, the two orthogonally polarized components experience a relative delay, macroscopically manifested as a small rotation of the polarization direction by a tiny angle, known as the polarization rotation angle θ. The formula for calculating the polarization rotation angle θ is: θ = (π / λ)·r·E·L, where λ is the laser wavelength; r is the effective electro-optic coefficient of the lithium niobate crystal; E is the intensity of the partial discharge electric field applied to the crystal; and L is the light transmission length of the lithium niobate electro-optic crystal. Based on λ = 550 nm, r = 30 pm / V, E = 4 V / m, and L = 6.8 cm, the obtained θ is extremely small, approximately 7.4 × 10⁻⁶. -5 radian.
[0039] The Jones vector of the 45° linearly polarized light emitted from the polarizer is:
[0040]
[0041] After being processed by the electro-optic crystal, its polarization direction is rotated by a small angle θ, and the Jones vector of the outgoing light becomes:
[0042]
[0043] The Jones matrix (projection operator) for the -45° analyzer is:
[0044]
[0045] The transmitted electric field is the projection of the output light onto the analyzer:
[0046]
[0047] Transmitted light intensity It is proportional to the square of the electric field mode. Considering the incident light intensity... Its relative rate of change is:
[0048]
[0049] Substituting the values into the equation, the calculated polarization rotation angle θ ≈ 7.4 × 10⁻⁶ -5 rad, we can get:
[0050]
[0051] 2. Optical System Design
[0052] (1) Initiator (input light): converts the incident laser into 45° linearly polarized light.
[0053] (2) Electro-optic crystal: A partial discharge field acts on the crystal, causing the light to be polarized and rotated.
[0054] (3) Analyzer: The analyzer is set to -45° linear polarization direction to realize polarization detection and convert polarization rotation into light intensity change (if the analyzer is set to +45°, then it is parallel to the polarizer direction. Regardless of whether the intermediate crystal introduces polarization rotation, most light can pass through, and it is impossible to effectively distinguish whether there is partial discharge phenomenon. If the analyzer is set to -45°, then in the absence of partial discharge phenomenon, ideally no light passes through, so it can be determined whether there is partial discharge phenomenon).
[0055] (4) Detector: Single photon detector (SPCM), outputting TTL pulse signal.
[0056] 3. Signal detection mechanism
[0057] (1) Light intensity variation model:
[0058] The analyzer converts the polarization rotation angle θ into a light intensity signal. According to Malus's law, the relationship between the output light intensity I, the incident light intensity I0, and the polarization rotation angle θ is as follows:
[0059] I = I0·sin²θ
[0060] Since the theoretical output light intensity is zero when there is no partial discharge signal, the change in light intensity ΔI = I0·sin²θ. Therefore, the relative rate of change of light intensity is:
[0061] ΔI / I0=sin²θ
[0062] When the polarization rotation angle θ is extremely small, it can be approximated by a small angle, sinθ≈θ, and the above equation can be simplified to:
[0063] ΔI / I0≈θ²
[0064] Substituting into the previous calculation, the polarization rotation angle θ≈7.4×10 -5 rad, we can get:
[0065] ΔI / I0 = 5.47 × 10 -9
[0066] Therefore, the change in light intensity is extremely weak, ΔI / I0~10 -9 The order of magnitude ("~" usually means "order of magnitude" or "approximately").
[0067] (2) Detector selection:
[0068] Because the change in light intensity is extremely weak, a high-precision single-photon detector with a time resolution of 60 ns (10 ns pulse + 50 ns dead time) is selected. This detector can count individual photons and has extremely high sensitivity. When the single-photon detector outputs ≥2 photon events within 200 ns, it is determined to be a partial discharge; otherwise, it is determined to be the absence of a partial discharge phenomenon.
[0069] The partial discharge field lasts for about 200 ns, and a maximum of 4 consecutive photon counts can be detected. The SPCM can record a maximum of about 4 photon events (because it has a 10 ns pulse and a 50 ns dead time).
[0070] Therefore, the occurrence of a partial discharge event will manifest as a slight increase in the output photon count of the SPCM (from an occasional single count due to background noise to several consecutive counts within a short period of time).
[0071] In practical implementation, the device also includes a silicon photomultiplier tube 6, used to independently detect partial discharge photons. It achieves mutual detection with the single-photon detector signal through time correlation, significantly improving detection reliability and reducing the false alarm rate. Specifically, when the silicon photomultiplier tube outputs a signal, it is designated as the trigger signal; when the single-photon detector outputs a pulse signal, it is designated as the stop signal. Generally, the silicon photomultiplier tube first detects the light signal, generating a pulse, and the time-to-digital converter starts timing. Subsequently, within tens of nanoseconds, the single-photon detector detects the laser signal modulated by the electric field, generating a pulse, and the time-to-digital converter stops timing. Finally, the verification result is calculated based on the time difference between the two detected light signals; a time difference of less than 100 ns proves that the detected signals are reliable. In practical implementation, the time-to-digital converter can be placed in an FPGA programmable controller.
[0072] In practice, a valid partial discharge event is determined when the time difference between the output signal of the single-photon detector and the output signal of the silicon photomultiplier tube is less than 100 ns.
[0073] In practice, the laser wavelength of the laser source is 550nm.
[0074] In practice, the time resolution of the single-photon detector is 60 ns.
[0075] In practical implementation, the ferroelectric domains Λ in the periodic polarization structure satisfy:
[0076]
[0077] Where c is the speed of light, w rf n is the angular frequency of the partial discharge field. g v is the refractive index of the photon group. rf Let be the speed at which the electric field propagates.
[0078] In practice, the single-photon detector has a dead time of 50 ns and a pulse width of 10 ns, and can capture up to 4 consecutive photon counts within a duration of 200 ns.
[0079] In practice, the polarization extinction ratio of the -45° analyzer is greater than 40dB, and the noise of the laser source is lower than -110dBm, to meet the light intensity change sensitivity ΔI / I0~10. -9 .
[0080] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the present invention. Although detailed descriptions have been provided with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments, and they should all be covered within the protection scope of the claims.
Claims
1. A partial discharge detection apparatus based on polarization change, characterized by, Comprising: a laser source (1) for generating a laser beam; a 45° polarizer (2) for modulating the laser beam generated by the laser source into 45° linearly polarized light; a lithium niobate electro-optic crystal (3) for applying a partial discharge electric field to the crystal to cause a polarization change of the 45° linearly polarized light; a periodic polarization structure composed of N segments of periodically arranged ferroelectric domains for accumulating and amplifying the polarization change; a -45° analyzer (4) arranged in a -45° linearly polarized direction to convert the polarization change into an optical intensity signal; a single-photon detector (5) for converting the optical intensity signal converted by the -45° analyzer into a TTL pulse signal output.
2. The partial discharge detection device based on polarization change according to claim 1, characterized in that The device further comprises a silicon photomultiplier (6) for independently detecting partial discharge photons, and mutual detection is achieved through time correlation with the single-photon detector signal.
3. The partial discharge detection device based on polarization change according to claim 2, characterized in that When the time difference between the single-photon detector output signal and the silicon photomultiplier output signal is less than 100 ns, it is determined as an effective partial discharge event.
4. The partial discharge detection device based on polarization change according to claim 3, characterized in that The laser wavelength of the laser source is 550 nm.
5. The partial discharge detection device based on polarization change according to claim 4, characterized in that The time resolution of the single-photon detector is 60 ns.