CN112986646B - Double-pulse health detection system and method based on all-fiber current transformer - Google Patents
Double-pulse health detection system and method based on all-fiber current transformer Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/24—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using light-modulating devices
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- G—PHYSICS
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R35/00—Testing or calibrating of apparatus covered by the other groups of this subclass
- G01R35/02—Testing or calibrating of apparatus covered by the other groups of this subclass of auxiliary devices, e.g. of instrument transformers according to prescribed transformation ratio, phase angle, or wattage rating
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Abstract
The invention discloses a dipulse health detection system and a dipulse health detection method based on an all-fiber current transformer, wherein the system comprises a dipulse light source module, a light path module, a modulation module and a signal processing module; the double-pulse light source module sends out a periodic double-pulse test light source, and the periodic double-pulse test light source returns to the signal processing module along the light path module after passing through the light path module and the modulation module; according to the detection method provided by the invention, on the basis of the structure of the optical fiber current transformer, a light source is utilized to generate periodic wide and narrow double-pulse signals, the signals are connected in series into an original light path through an optical fiber coupler, and a modulation module and a light path module of the optical fiber current transformer are respectively detected according to different modulation depths of a phase modulator under different voltages and a Rayleigh scattering principle, so that the optical fiber current transformer is rapidly checked for faults; the invention can also have the function of current measurement while providing a double-pulse health detection system.
Description
Technical Field
The invention relates to the technical field of optical fiber current transformer detection, and mainly relates to a double-pulse health detection system and method based on an all-optical fiber current transformer.
Background
In order to adapt to large-scale trans-regional power transmission and develop an ultra-high voltage and other high-capacity, high-efficiency and long-distance advanced power transmission technology in the last five years, China vigorously promotes the construction of ultra-high voltage transmission networks. The improvement of the transmission voltage grade has new requirements on the transmission and detection capability of a power grid, and in an extra-high voltage power grid, an optical fiber current transformer is used as primary equipment for measuring current, and the safe and stable operation of a converter station can be ensured only if the fault does not occur or is eliminated as soon as possible in the working period.
The fiber current transformer equipment used in the converter station is generally based on a Sagnac interferometric structure, although the measurement precision is high, the connection requirement for each optical device is also high, and measurement errors can be caused by temperature changes, device aging and the like. During the construction, operation and maintenance of the extra-high voltage power grid, the electric power operation and inspection department finds that the optical fiber current transformer has a high error rate, and the failure is usually based on experience, and an effective troubleshooting means is lacked, so that the safety of the power grid is seriously influenced, and great challenges are brought to the operation and maintenance of the power grid.
On the other hand, most of optical fiber current transformer equipment in the domestic converter station is purchased from foreign companies or agents, has patent protection and often cannot directly obtain data when a fault occurs. Various problems always occur in the operation process of the optical fiber current transformer, and at present, no health detection method aiming at the optical fiber current transformer exists in China, so that an effective, convenient and easily-obtained optical fiber current transformer health detection method is needed.
Disclosure of Invention
The purpose of the invention is as follows: the invention provides a double-pulse health detection method of an optical fiber current transformer, which is characterized in that on the basis of the structure of the optical fiber current transformer, a light source is utilized to generate periodic wide and narrow double-pulse signals, the signals are connected in series into an original light path through an optical fiber coupler, and a modulation module and a light path module of the optical fiber current transformer are respectively detected according to different modulation depths of a phase modulator under different voltages and a Rayleigh scattering principle, so that the optical fiber current transformer is rapidly checked for faults.
The technical scheme is as follows: in order to achieve the purpose, the invention adopts the technical scheme that:
a double-pulse health detection system based on an all-fiber current transformer comprises a double-pulse light source module, a light path module, a modulation module and a signal processing module; the double-pulse light source module sends out a periodic double-pulse test light source, and the periodic double-pulse test light source returns to the signal processing module along the light path module after passing through the light path module and the modulation module;
the double-pulse light source module outputs periodic double-pulse signals comprising wide pulse signals and narrow pulse signals; the wide pulse signal is used for carrying out health detection on the modulation module, and the narrow pulse signal is used for carrying out health detection on the light path module;
the light path module adopts a reflective Sagnac interference type current transformer light path module;
the modulation module comprises a phase modulator and a driving signal and applies a modulation phase to the light path module; the drive signal of the phase modulator is a sinusoidal sweep voltage whose amplitude varies within the operating voltage range of the phase modulator
The signal processing module comprises a photoelectric detector and a signal processing system; the photoelectric detector is connected with a return light path of the light path module through the optical fiber coupler, receives a return light signal and transmits the return light signal to the signal processing system, and the signal waveform is analyzed and processed to judge the health state of the current transformer.
A detection method of a double-pulse health detection system adopting the all-fiber current transformer comprises the following steps:
step S1, the double-pulse light source module outputs periodic double-pulse signals in a direct modulation or indirect modulation mode, and the signals are divided into wide pulse signals and narrow pulse signals according to pulse width;
the frequency of the driving signal of the modulation module is fmThen T is0＝1/fmThe width of the wide pulse is T-10T0The width τ of the narrow pulse is set to 100 ns; the time interval t ' between the wide pulse and the next narrow pulse is not less than 2nL/c, wherein n is the refractive index of the optical fiber, L is the length of the optical fiber, c is the light speed in vacuum, and the interval t ' between the narrow pulse and the next wide pulse is not less than 2t ', so that the narrow pulse and the scattered light thereof are dissipated in the light path and cannot interfere with the subsequent measurement;
step S2, after the wide pulse signal sent by the double-pulse light source module enters the light path module, the wide pulse signal is modulated by the modulation module phase modulator, carries non-anisotropic phase information, and collects the returned light signal; and the health status of the modulation module can be obtained by the following demodulation method. A demodulation method is proposed, wherein a scale factor SF is defined as follows:
wherein P isMRepresenting the maximum value, P, of the actual power measured when the output wide pulse signal returns after passing through the optical path modulemRepresents the minimum value of the measured actual power,
represents the average of the measured actual powers; phi is amRepresents the modulation depth of the phase modulator; the scale factor SF can be calculated according to the maximum value, the minimum value and the average value of the output waveform, thereby calculating the modulation depth phimThe modulation coefficient of the phase modulator can be obtained according to the modulation depth under different voltages, and the working characteristic and the health state of the phase modulator are judged;
step S3, after a narrow pulse signal sent by the double-pulse light source module enters the light path module, according to the Rayleigh scattering principle, backward scattered light can be generated in the axial direction of the optical fiber, and loss information transmitted along the optical fiber can be collected by receiving the returned scattered light from the input end, so that the attenuation of the optical fiber is obtained; and acquiring the health state of the optical path module according to different attenuation characteristics of different devices.
Has the advantages that:
according to the double-pulse health detection system and method of the all-fiber current transformer, provided by the invention, the health detection is simultaneously carried out on the light path module and the modulation module of the all-fiber current transformer, and the light source module and the modulation module are partially changed on the basis of the original all-fiber current transformer, so that the complexity of the health maintenance of the system is reduced. In addition, the double-pulse health detection system provided by the invention can combine the current measurement and the health detection functions after corresponding setting, so that the all-fiber current transformer with self-detection is formed.
Drawings
FIG. 1 is a block diagram of a dual pulse health detection system based on an all-fiber current transformer provided by the present invention;
FIG. 2 is a diagram of the output pulses of a double-pulse light source module provided by the present invention;
FIG. 3a is a waveform diagram of a wide pulse and its return signal provided by the present invention;
FIG. 3b is a waveform diagram of signals provided by the present invention at different voltage amplitudes;
FIG. 4 is a waveform diagram of a narrow pulse return signal provided by the present invention;
FIG. 5 is a waveform diagram of a double pulse detection signal provided by the present invention;
fig. 6 is a schematic structural diagram of an all-fiber current transformer with self-detection provided by the present invention.
Description of reference numerals:
1-a double pulsed light source; 2-a coupler; 3-a depolarizer; 4-45 degrees of welding points; 5-a polarizer; a 6-phase modulator; 7-polarization maintaining fiber; 8-45 degrees of welding points; 9-a quarter wave plate; 10-sensing optical fiber coil; 11-a mirror; 12-measured current; 13-scan voltage modulation signal; 14-a photodetector; 15-signal processing system.
Detailed Description
The present invention will be further described with reference to the accompanying drawings.
As shown in fig. 1, a double-pulse health detection system based on an all-fiber current transformer includes a double-pulse light source module, a light path module, a modulation module and a signal processing module; the double-pulse light source module sends out a periodic double-pulse test light source, and the periodic double-pulse test light source returns to the signal processing module along the light path module after passing through the light path module and the modulation module;
the double-pulse light source module outputs periodic double-pulse signals comprising wide pulse signals and narrow pulse signals; the wide pulse signal is used for carrying out health detection on the modulation module, and the narrow pulse signal is used for carrying out health detection on the light path module;
the light path module adopts a reflective Sagnac interference type current transformer light path module;
the modulation module comprises a phase modulator and a driving signal and applies a modulation phase to the light path module;
the signal processing module comprises a photoelectric detector and a signal processing system; the photoelectric detector is connected with a return light path of the light path module through the optical fiber coupler, receives a return light signal and transmits the return light signal to the signal processing system, and the signal waveform is analyzed and processed to judge the health state of the current transformer.
The invention mainly comprises a double-pulse light source module and a signal processing module, and a light path module and a modulation module are original parts of the all-fiber current transformer. In the structure of the all-fiber current transformer, light emitted by a light source module enters a light path module, a non-anisotropic phase difference is generated under the action of a modulation module, phase information is superposed in an optical signal and finally returns along a light path, and the phase information enters a data processing module for processing and analysis. In the double-pulse health detection method of the all-fiber current transformer, the original light path module is kept still, only the output of the light source module and the driving signal of the adjusting module are adjusted, so that the light source module outputs double-pulse signals, meanwhile, the driving signals are changed into scanning voltages with uniformly changed amplitudes, and finally, analysis and judgment are carried out according to the returned signals.
The detection method based on the double-pulse health detection system comprises the following specific steps:
step S1, the double-pulse light source module outputs a periodic double-pulse signal by direct modulation or indirect modulation, and the periodic double-pulse signal is divided into a wide-pulse signal and a narrow-pulse signal according to the pulse width, as shown in fig. 2:
the frequency of the driving signal of the modulation module is fmThen T is0＝1/fmThe width of the wide pulse is T-10T0The width τ of the narrow pulse is set to 100 ns; the time interval t ' between the wide pulse and the next narrow pulse is not less than 2nL/c, wherein n is the refractive index of the optical fiber, L is the length of the optical fiber, c is the light speed in vacuum, and the interval t ' between the narrow pulse and the next wide pulse is not less than 2t ', so that the narrow pulse and the scattered light thereof are dissipated in the light path and cannot interfere with the subsequent measurement;
step S2, shown in fig. 3a, is a wide pulse and its return signal waveform (here only the wide pulse signal is shown). When the modulation module is in a healthy working state, the modulation depth of the modulation module is in a linear relation with the driving voltage (when no current is measured in the system). When calculating the modulation depth of the phase modulator from the received return signal waveform, because of the actually measured maximum value PMIs an ideal maximum value PM idealAnd noise PnoiseOf (a) or (b), i.e. PM＝PM ideal+PnoiseSimilarly, the minimum value P actually measuredmAnd average value
Is Pm＝Pm ideal+Pnoise，
Pm ideal＝P0(1+cosφm)
Wherein P is0Is a factor of the output signal power. When cos phimWhen it is 1, it is maximum, so
PM ideal＝2P0
Defining a scale factor
Therefore, the scale factor SF can be calculated according to the maximum value, the minimum value and the average value of the output waveform, and the modulation depth phi is calculatedmAccording to the modulation depth under different voltages, the modulation coefficient of the phase modulator can be obtained, and the working characteristics and the healthy state of the phase modulator are judged.
Fig. 3b shows the signal waveform at different voltage amplitudes.The driving signal of the phase modulator adopts a sine scanning voltage, and the amplitude of the sine scanning voltage is changed within the working voltage range of the phase modulator. When the wide pulse light is modulated by the phase modulator to which the driving signals of different amplitudes are applied, the output waveform is as shown in fig. 3 b. According to the maximum value, the minimum value and the average value of the waveform, the modulation depth phi of the phase modulator under different voltages can be obtainedmTherefore, whether the modulation of the phase modulator is linear and in a reasonable range can be judged, and the health state of the modulation module is obtained.
Step S3, after the narrow pulse signal emitted by the double-pulse light source module enters the light path module, according to the rayleigh scattering principle, the optical fiber generates backward scattered light in the axial direction, and loss information transmitted along the optical fiber can be collected by receiving the returned scattered light from the input end, thereby obtaining the attenuation of the optical fiber. As shown in fig. 4, the narrow pulse return signal waveform is used as an OTDR technique, and the quality of the optical path can be evaluated according to the attenuation of the return signal waveform. Because the length of the optical fiber and the position of the optical device are fixed, and the working environment is stable, the attenuation condition of the optical fiber is related to the optical characteristics of the optical device under normal conditions, if the attenuation is changed, a problem occurs in one of the optical devices, and the health state of the optical path module is obtained according to the different attenuation characteristics of different devices.
Fig. 5 is a diagram of a double pulse detection signal provided by the present invention. After the periodic double-pulse light signals emitted by the double-pulse light source module pass through the light path, the wide pulse signals in the output signals carry health information of the modulation module, the narrow pulses carry health information of the light path module, and finally waveforms shown in fig. 5 are obtained, the waveforms shown in fig. 5 are segmented, and the health evaluation is made by combining the judgment basis of the health detection.
Fig. 6 is a schematic structural diagram of an all-fiber current transformer with self-detection according to an embodiment of the present invention, where 2-12 and 14-15 are basic structures of a reflective Sagnac interferometric all-fiber current transformer, a broadband light source of an existing all-fiber current transformer is replaced with a double-pulse light source, and a modulation signal is replaced with a scanning voltage modulation signal, so that when a measured current exists in a system, the measured current can be obtained according to a ratio of a second harmonic to a fourth harmonic of a detection signal returned by the wide-pulse signal, and a light path module can be subjected to health detection according to the above method, so as to implement the all-fiber current transformer with self-detection.
The above description is only of the preferred embodiments of the present invention, and it should be noted that: it will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the principles of the invention and these are intended to be within the scope of the invention.
Claims (2)
1. A dipulse health detection system based on an all-fiber current transformer is characterized by comprising a dipulse light source module, a light path module, a modulation module and a signal processing module; the double-pulse light source module sends out a periodic double-pulse test light source, and the periodic double-pulse test light source returns to the signal processing module along the light path module after passing through the light path module and the modulation module;
the double-pulse light source module outputs periodic double-pulse signals comprising wide pulse signals and narrow pulse signals; the wide pulse signal is used for carrying out health detection on the modulation module, and the narrow pulse signal is used for carrying out health detection on the light path module;
the light path module adopts a reflective Sagnac interference type current transformer light path module;
the modulation module comprises a phase modulator and a driving signal and applies a modulation phase to the light path module; the driving signal of the phase modulator adopts sine scanning voltage, and the amplitude value of the sine scanning voltage changes within the working voltage range of the phase modulator;
the signal processing module comprises a photoelectric detector and a signal processing system; the photoelectric detector is connected with a return light path of the light path module through the optical fiber coupler, receives a return light signal and transmits the return light signal to the signal processing system, and the signal waveform is analyzed and processed to judge the health state of the current transformer.
2. A detection method using the all-fiber current transformer based double-pulse health detection system according to claim 1, comprising the steps of:
step S1, the double-pulse light source module outputs periodic double-pulse signals in a direct modulation or indirect modulation mode, and the signals are divided into wide pulse signals and narrow pulse signals according to pulse width;
the frequency of the driving signal of the modulation module is fmThen T is0＝1/fmThe width range of the wide pulse is T10-20T0The setting range of the width tau of the narrow pulse is 50-200 ns; the time interval t ' between the wide pulse and the next narrow pulse is not less than 2nL/c, wherein n is the refractive index of the optical fiber, L is the length of the optical fiber, c is the light speed in vacuum, and the interval t ' between the narrow pulse and the next wide pulse is not less than 2t ', so that the narrow pulse and the scattered light thereof are dissipated in the light path and cannot interfere with the subsequent measurement;
step S2, after the wide pulse signal sent by the double-pulse light source module enters the light path module, the wide pulse signal is modulated by the modulation module phase modulator, carries non-anisotropic phase information, collects the returned light signal, and obtains the health state of the modulation module by the following demodulation method; specifically, the scale factor SF is defined as follows:
wherein P isMRepresenting the maximum value, P, of the actual power measured when the output wide pulse signal returns after passing through the optical path modulemRepresents the minimum value of the measured actual power,
represents the average of the measured actual powers; phi is amRepresents the modulation depth of the phase modulator; the scale factor SF can be calculated according to the maximum value, the minimum value and the average value of the output waveform, thereby calculating the modulation depth phimThe value of (A) can be obtained according to the modulation depth under different voltagesModulation coefficient, judging the working characteristics and health status of the phase modulator;
step S3, after a narrow pulse signal sent by the double-pulse light source module enters the light path module, according to the Rayleigh scattering principle, backward scattered light can be generated in the axial direction of the optical fiber, and loss information transmitted along the optical fiber can be collected by receiving the returned scattered light from the input end, so that the attenuation of the optical fiber is obtained; and acquiring the health state of the optical path module according to different attenuation characteristics of different devices.
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