JP2013053949A - Acetylene gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an acetylene gas sensor capable of effectively detecting acetylene gas from an insulating medium used in an electric power apparatus.SOLUTION: An acetylene gas sensor comprises: a light source for emitting light of a first wavelength range including at least a part of wavelength of 1510 nm to 1540 nm and a second wavelength range including a wavelength from the first wavelength range to less than 100 nm; a container which is charged with a fluid and has a space for passing the light; a light branching device for branching the light having passed through the container into first and second light; a first filter to which the light of the first wavelength is made incident and which passes the light of the first wavelength range and shields the light of the second wavelength range; and a second filter to which the light of the second wavelength is made incident and which passes the light of the second wavelength range and shields the light of the first wavelength range.

Description

  The present invention relates to an acetylene gas sensor that detects acetylene gas.

An apparatus capable of diagnosing abnormality or deterioration of power equipment (including an electrical equipment and an electrical equipment container that houses the electrical equipment and is filled with an insulating medium) has been proposed (see Patent Documents 1 and 2).
In the apparatus described in Patent Document 1, an opening outside a pipe communicating with an electrical equipment container is closed with a transparent glass tube, and a detection tube that detects decomposition gas contained in an insulating medium inside the glass tube by color change. Place. By monitoring the discoloration of the detector tube with an optical sensor, it is possible to diagnose abnormalities and deterioration of power equipment.

  In the apparatus described in Patent Document 2, light emitted from a light source is passed through a gas detection cell containing a gas to be measured and then divided into two by a beam splitter. One light divided into two is passed through an interference filter that transmits only light having the absorption wavelength of the detection target gas, and the other light is transmitted through an interference filter that transmits light other than the absorption wavelength of the measurement target. The light transmitted through each interference filter is recombined by the beam splitter, the interference light generated by the combination is converted into an electric signal, and the concentration of the gas to be detected is detected based on the intensity.

JP 2002-373813 A Japanese Utility Model Publication No. 5-55051

  However, in the apparatus described in Patent Document 1, the detection sensitivity of the detector tube with respect to acetylene gas becomes a problem. The acetylene gas is a gas caused by arc discharge or partial discharge in particular, and it is determined that there is an abnormality in the electrical equipment even if the detected amount is very small.

  In the detection apparatus described in Patent Document 2, a semiconductor laser is used as a light source. However, the semiconductor laser has a narrow wavelength range, and it is difficult to manufacture a semiconductor laser having a wavelength range suitable for detection of acetylene gas (for example, a wide range of 1320 nm to 1550 nm as the wavelength of signal light and reference light). In addition, the optical path length of the two lights separated by the beam splitter must be selected appropriately so as to cause interference. If the optical path length changes, the brightness of the interference light will fluctuate and the detection accuracy of the sensor will be reduced. Let

  An object of this invention is to provide the acetylene gas sensor which aimed at the efficient detection of acetylene gas from the insulation medium used for an apparatus for electric power.

  The acetylene gas sensor according to one embodiment of the present invention emits light in a first wavelength range including at least a part of wavelengths from 1510 nm to 1540 nm, and a second wavelength range including a wavelength within 100 nm from the first wavelength range. A fluid is enclosed; a light source that emits light; a first optical fiber that transmits light emitted from the light source; a first lens that converts light transmitted through the first optical fiber into parallel light; A container having a space through which light emitted from the first lens passes, a second lens for converting parallel light that has passed through the space into convergent light, and light emitted from the second lens A second optical fiber for transmitting the light, an optical branching device for branching the light transmitted by the second optical fiber into first and second light, and the first light being incident, Passes light in the wavelength range, and the second wavelength range A first filter that blocks light; a second filter that receives the second light, passes light in the second wavelength band, and blocks light in the first wavelength band; A first photodetector for receiving light emitted from one filter, a second photodetector for receiving light emitted from the second filter, and the first and second photodetectors. And a signal processor for calculating the amount of acetylene gas in the fluid based on the first and second electric signals from each of them.

  ADVANTAGE OF THE INVENTION According to this invention, the acetylene gas sensor which aimed at the efficient detection of acetylene gas from the insulating medium used for an apparatus for electric power can be provided.

It is a schematic block diagram which shows the acetylene gas sensor of 1st Embodiment. It is a figure which shows an example of the emission spectrum of a super luminescence diode (cited from the specification table | surface of Dense Light Semiconductor SLD DL-CS5254A). It is a figure which shows the absorption spectrum of acetylene gas (cited from http://www.dartmouth.edu/~chem81/labs/C2H2.html). It is a schematic block diagram which shows the acetylene gas sensor of 2nd Embodiment. It is a schematic block diagram which shows the acetylene gas sensor of 3rd Embodiment. It is a schematic block diagram which shows the acetylene gas sensor of 4th Embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a schematic configuration diagram showing an acetylene gas sensor according to the first embodiment. The acetylene gas sensor includes a super luminescence diode (SLD) 20, optical fibers 21a to 21d, collimator lenses 22a and 22b, a coupler 23, bandpass filters 24a and 24b, avalanche photodiodes (APD) 25a and 25b, a signal processor. 26, an electrical equipment container 30 is provided.

  As shown in FIG. 2, the emission spectrum of the super luminescence diode (SLD) 20 has a wavelength range of 1500 to 1590 [nm] with a peak near 1555 nm. The SLD 20 is a light source that emits at least light in the wavelength region A2 having a distance D from the wavelength region A1 and the wavelength region A1 including at least some wavelengths of 1513 to 1543 [nm]. Wavelength regions A1 and A2 are respectively detected for detection of absorption by acetylene (detection of acetylene) and detection of absorption by a substance other than acetylene (for example, insulating medium (oil) itself, substance caused by insulating medium) (calibration of acetylene detection ( Set for reference)). In FIG. 2, wavelength ranges A1 and A2 are included in the emission spectrum, and examples of the wavelength ranges A1 and A2 and the interval D include 1510 to 1540 [nm], 1560 to 1580 [nm], and 20 [nm]. Indicated.

The wavelength region A1 corresponds to the absorption wavelength region of acetylene gas. As shown in FIG. 3, the range of the absorption spectrum of acetylene gas is 6480 to 6610 [cm ⁻¹ ] in wave number display, and 1513 to 1543 [nm] in wavelength display. The wavelength range A1 may include the entire absorption wavelength range “1513 to 1543 [nm]” or only a part thereof.

As shown in FIG. 3, the absorption wavelength region of the acetylene gas includes absorption peaks P1 (wavelength: 1520.1 [nm], wave number: 6578.5 [cm ⁻¹ ]), P2 (wavelength: 1530.3 [ nm], wave number: 6534.5 [cm ⁻¹ ]). For this reason, it is preferable that the wavelength range A1 includes at least one of the absorption peaks P1 and P2. In order to ensure sensitivity, the width W of the wavelength region A1 (the difference between the upper and lower limits λ1 and λ2 of the wavelength region A1 (W = λ2−λ1)) is preferably about 10 nm or more (more preferably, The width W is about 20 nm or more).

  The wavelength region A2 is set outside the absorption wavelength region “1513 to 1543 [nm]” of the acetylene gas. However, considering the wavelength dependence of absorption by substances other than acetylene, it is not preferable that the wavelength region A2 deviates greatly from the wavelength region A1. For this reason, it is preferable that the interval D between the wavelength region A2 and the wavelength region A1 is within 100 nm (the wavelength region A2 includes a wavelength within 100 nm from the wavelength region A1) (more preferably, the interval D is 50 nm). And more preferably, the distance D is within 20 nm)).

  The optical fiber 21a transmits the infrared light emitted from the SLD 20 to the collimator lens 22a.

  The collimator lens 22a is a lens that converts infrared light transmitted through the optical fiber 21a into parallel light.

  The electrical device container 30 is a container having a space in which a fluid to be inspected is sealed and light emitted from the collimator lens 22a passes. This fluid is a gas or liquid containing acetylene gas. An insulating medium such as a transformer (for example, insulating oil) itself can be an inspection target. Alternatively, a gas component (acetylene or the like) dissolved in the insulating medium may be extracted and used as an inspection target.

  The electrical device container 30 includes side plates 31a and 31b facing each other and quartz glass 32a and 32b disposed on the side plates 31a and 31b, respectively. The quartz glasses 32a and 32b function as windows made of a material that transmits light in the wavelength ranges A and A2. It is preferable to prevent reflection of infrared light from the surfaces of the quartz glasses 32a and 32b by applying an antireflection coating to the surfaces of the quartz glasses 32a and 32b.

  The collimator lens 22b is a lens that converts parallel light that has passed through the space of the electrical device container 30 into convergent light and makes it incident on the optical fiber 21b. Infrared light is reduced to the diameter of the core of the optical fiber 21b.

  The optical fiber 21 b transmits the infrared light emitted from the collimator lens 22 b to the coupler 23.

The coupler 23 is an optical branching device that branches the infrared light transmitted through the optical fiber 21b into first and second infrared lights.
The optical fibers 21c and 21d transmit the first and second infrared lights branched by the coupler 23 to the band-pass filters 24a and 24b, respectively.

  The band filters 24a and 24b receive the first and second infrared lights branched by the coupler 23, respectively. Each of the band filters 24a passes only light in the wavelength bands A1 and A2 (the band filter 24a passes light in the wavelength band A1 and blocks light in the wavelength band A2. The band filter 24b is in the wavelength band A2. The light passes through and the light in the wavelength band A1 is blocked).

  The APDs 25a and 25b function as photodetectors that receive light emitted from the bandpass filters 24a and 24b, respectively.

  The signal processor 26 calculates the amount of acetylene gas in the fluid in the electrical device container 30 based on the first and second electrical signals S1 and S2 from the APDs 25a and 25b, respectively. As will be described later, the relationship between the ratio (S1 / S2) or the logarithm (log (S1 / S2)) of the signal intensities S1 and S2 from the APDs 25a and 25b and the amount of acetylene gas in the fluid in the electrical equipment container 30 The amount of acetylene gas in the electrical equipment container 30 can be calculated based on the table T representing

Since the band-pass filter 24a passes only light in the wavelength band A1 corresponding to the absorption wavelength band of acetylene gas, the intensity of the signal S1 from the APD 25a (for example, the output current from the APD) is the absorption coefficient α1, acetylene gas. It decreases according to the concentration N1 of acetylene gas. In general, the intensity of the signal S1 is a function of α1, N1, and L.
α1: Absorption coefficient of acetylene gas (average absorption coefficient in wavelength range A1)
N1: Concentration of acetylene gas in the space of the electrical equipment container 30 L: Optical path length in the space of the electrical equipment container 30

However, absorption by substances other than acetylene is not considered here. In consideration of absorption by acetylene gas and substances other than acetylene, the intensity of the signal S1 is a function of αx, Nx, Ax in addition to α1, N1, L.
αx: Absorption coefficient of substances other than acetylene gas in the space of the electrical equipment container 30 (average absorption coefficient in the wavelength region A1)
Nx: Concentration of substances other than acetylene gas in the space of the electrical equipment container 30 Ax: Absorptivity in the wavelength region A1 due to contamination of the surfaces of the quartz glasses 32a and 32b

Since the band-pass filter 24b passes only light in the wavelength band A2 corresponding to the absorption wavelength band of acetylene gas, the intensity of the signal S2 from the APD 25b (for example, output voltage from the APD) is αx ′, Nx, Ax ′. Is a function of
αx ′: Absorption coefficient of substances other than acetylene gas in the space of the electrical equipment container 30 (average absorption coefficient in the wavelength region A2)
Ax ′: Absorptivity in the wavelength region A2 due to dirt on the surfaces of the quartz glasses 32a and 32b

  As described above, the wavelength region A2 is outside the absorption wavelength region of acetylene gas. For this reason, the signal S2 does not reflect absorption due to acetylene gas (APD output voltage drop), but reflects absorption due to contamination of the insulating medium or contamination of the surfaces of the quartz glasses 32a and 32b. That is, the signal S2 represents a decrease in the amount of passing light due to aging.

The signal processor 26 obtains a ratio ΔS between the signals S1 and S2.
ΔS = S1 / S2
By taking the ratio ΔS, the influence of absorption by substances other than acetylene gas can be canceled. This is because the difference between the absorption coefficients αx and αx ′ and the absorption rates Ax and Ax ′ is small (αx to αx ′, Ax to Ax ′) because the interval D between the wavelength regions A1 and A2 is not large.

  There is a proportional relationship between the logarithm “log (S1 / S2)” of the ratio ΔS and the concentration N1 of the acetylene gas. For this reason, for example, by enclosing a fluid having a known acetylene gas concentration in the space of the electrical equipment container 30, and measuring the signal intensities S1 and S2 from the APDs 25a and 25b, the ratio of the signal intensities S1 and S2 (S1 / S2) or the logarithm thereof and the table T representing the relationship between the amount of acetylene gas in the fluid in the electrical equipment container 30 can be created. The created table T is stored in the signal processor 26 and can be used to calculate the amount of acetylene gas.

(Operation of the acetylene gas sensor of the first embodiment)
Hereinafter, the operation of the acetylene gas sensor will be described.
Infrared light emitted from the SLD 20 is transmitted by the optical fiber 21a and converted into parallel light by the collimator lens 22a. The parallel infrared light passes through the insulating medium in the electrical equipment container 30 through the quartz glass 32 a and 32 b of the electrical equipment container 30. The infrared light that has passed through the insulating medium is focused by the collimator lens 22b, and is incident on and transmitted to the optical fiber 21b.

  The infrared light is divided into two by the coupler 23 and converted into electrical signals S1 and S2 by avalanche photodiodes (APD) 25a and 25b through band-pass filters 24a and 24b.

  As described above, based on the table T and the signals S1 and S2, the signal processor 26 calculates the amount of acetylene gas (concentration N1) in the insulating medium. That is, the signal processor 26 can reduce the influence of absorption other than ethylene gas by using the signal S2 from the APD 25b (the signal S1 from the APD 25a is corrected). As a result, it is possible to detect acetylene gas in the insulating medium, which is judged to be abnormal in electrical equipment, with high sensitivity in consideration of aging.

(Second Embodiment)
FIG. 4 is a configuration diagram of the second embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted. In this embodiment, the laser 41a and 41b are used in place of the super luminescence diode 20 in the first embodiment.

  The laser 41a is a light source that emits infrared light in a wavelength region A1 including at least a part of wavelengths 1513 to 1543 [nm] corresponding to the absorption wavelength of acetylene gas.

  The laser 41b does not correspond to the absorption wavelength of the acetylene gas, and the infrared light in the wavelength region A2 including the wavelength D (for example, within 100 nm) from the wavelength region A1 (reference light for monitoring the secular change of the laser 41a). A light source that emits light.

In the first embodiment, since the light source is the super luminescence diode (SLD) 20, the widths W1 and W2 of the wavelength regions A1 and A2 are wide.
On the other hand, in this embodiment, since the light sources are the lasers 41a and 41b, the widths W1 and W2 of the wavelength regions A1 and A2 are narrowed. By making the emission wavelength of the laser 41a correspond to the absorption peaks P1 and P2 of the acetylene gas, it is possible to detect acetylene with high sensitivity.

The optical fibers 21e and 21f transmit laser beams emitted from the lasers 41a and 41b, respectively.
The coupler 23a combines the laser beams transmitted by the optical fibers 21e and 21f into a single beam, and functions as a mixer that mixes the light emitted from the lasers 41a and 41b.

  The interference filters 42a and 42b are filters having pass wavelength bands that pass wavelengths corresponding to light emitted from the lasers 41a and 41b, respectively. A bandpass filter and an interference filter are the same in that they transmit light having a wavelength set at the time of design, but a filter for selecting a wavelength intended for a laser with a particularly narrow window is generally called an interference filter.

  Similar to the first embodiment, the signal processor 26 calculates the amount of acetylene gas in the fluid in the electrical device container 30 based on the first and second electrical signals S1 and S2 from the APDs 25a and 25b, respectively. . As will be described later, based on the table T representing the relationship between the ratio (S1 / S2) of the signal intensities S1 and S2 from the APDs 25a and 25b or the logarithm thereof and the amount of acetylene gas in the fluid in the electrical equipment container 30, The amount of acetylene gas in the device container 30 can be calculated.

  Also in this embodiment, as described above, the signal processor 26 calculates the amount of acetylene gas (concentration N1) in the insulating medium based on the table T and the signals S1 and S2. That is, the signal processor 26 can reduce the influence of absorption other than acetylene gas using the signal S2 from the APD 25b (the signal S1 from the APD 25a is corrected). As a result, it is possible to detect acetylene gas in the insulating medium, which is judged to be abnormal in electrical equipment, with high sensitivity in consideration of aging.

(Third embodiment)
FIG. 5 is a configuration diagram of the third embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  Here, unlike the first embodiment, the quartz glass 32a and 32b are not used, and the optical fiber 21 is connected to the inside of the electrical equipment container 30 through the seal portions 33a and 33b and the collimator lenses 22a and 22b. Deploy. By not disposing the quartz glass 32a, 32b between the collimator lenses 22a, 22b, reflection by the quartz glass 32a, 32b and light loss can be reduced. As a result, acetylene gas in the insulating medium can be detected with higher sensitivity.

(Fourth embodiment)
FIG. 6 is a configuration diagram of the fourth embodiment. The same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

Here, the acetylene gas sensor according to the first embodiment is attached to a transformer as one of power devices. An iron core 51 and a winding 52 are arranged in the electric equipment container 50, and a flange 53 is attached to the upper part of the electric equipment container 50. This flange 53 is connected to a flange 55 of a sensor container 54 in which quartz glass 32a and 32b are arranged on both sides. The flange 55 is arranged on a surface of the sensor container 54 different from the installation surface of the quartz glass 32a, 32b. By installing a light emitting part and a light receiving part outside the quartz glass 32a, 32b, it becomes possible to detect acetylene gas in the insulating oil in the transformer.
The flange 55 may be fixed to a boss provided in the transformer tank.

  The sensor container 54 is connected to the electric device container 50 by the flanges 53 and 55. As a result, the sensor container 54 can be easily removed, and the surface of the quartz glass 32a, 32b can be easily removed or replaced. In addition, it can be easily installed on existing transformers.

  It is also possible to install the collimator lens 22 in the sensor container as in the third embodiment. In this case, as in the third embodiment, installation and inspection are easy.

(Other embodiments)
Embodiments of the present invention are not limited to the above-described embodiments, and can be expanded and modified. The expanded and modified embodiments are also included in the technical scope of the present invention.

For example, for the electric device container 30 in the first, second, and third embodiments and the electric device container 50 in the fourth embodiment, the electric power in which an insulating medium is sealed is a target for detecting acetylene gas. Any power device having a device may be used, such as a transformer, an instrument transformer, a bushing, or a reactor.
Also, the sensor mounting position may be changed, or the number of sensor mountings may be changed.
In the embodiment, the signal S1 is corrected by dividing the signal S1 by the signal S2 (to obtain the ratio (S1 / S2)). The signal S1 may be corrected by other methods.

20 Super luminescence diode 21a-21f Optical fiber 22a, 22b Collimator lens 23a Coupler 24a, 24b Bandpass filter 25a, 25b APD
26 Signal processor 30 Electric equipment container 31a, 31b Side plate 32a, 32b Quartz glass 33a, 33b Sealing part 41a, 41b Laser 42a, 42b Interference filter 50 Electric equipment container 51 Iron core 52 Winding 53 Flange 54 Sensor container 55 Flange

Claims (6)

A light source that emits light in a first wavelength range including at least a part of wavelengths of 1510 nm to 1540 nm and a second wavelength range including a wavelength within 100 nm from the first wavelength range;
A first optical fiber for transmitting light emitted from the light source;
A first lens for converting light transmitted through the first optical fiber into parallel light;
A container containing a fluid and having a space through which light emitted from the first lens passes;
A second lens that converts parallel light that has passed through the space into convergent light;
A second optical fiber for transmitting light emitted from the second lens;
An optical branching device for branching light transmitted through the second optical fiber into first and second light;
A first filter that receives the first light, passes the light in the first wavelength range, and blocks the light in the second wavelength range;
A second filter that receives the second light, passes the light in the second wavelength range, and blocks the light in the first wavelength range;
A first photodetector for receiving light emitted from the first filter;
A second photodetector for receiving light emitted from the second filter;
A signal processor for calculating the amount of acetylene gas in the fluid based on the first and second electric signals from the first and second photodetectors;
An acetylene gas sensor comprising: 2. The acetylene gas sensor according to claim 1, wherein the light source is a super luminescence diode (SLD) including infrared light in the first and second wavelength regions in an emission wavelength region. 3. The light source is
A first infrared laser including infrared light in the first wavelength region in an emission wavelength region;
A second infrared laser that includes infrared light in the second wavelength region in an emission wavelength region;
The acetylene gas sensor according to claim 1, further comprising a mixer that mixes light emitted from the first and second infrared lasers. The container is disposed on each of the first and second surfaces facing each other and the first and second surfaces, and the first and first materials are made of materials that transmit light in the first and second wavelength regions. Two windows,
4. The acetylene according to claim 1, wherein the first and second lenses are disposed outside the container so as to face the first and second windows. 5. Gas sensor. The acetylene gas sensor according to any one of claims 1 to 3, wherein the first and second lenses are disposed inside the container so as to face each other. The container is connected to the power device or includes at least part of the power device, including an electrical device and an electrical device container that houses the electrical device and is filled with an insulating medium;
The acetylene gas sensor according to claim 1, wherein the fluid is the insulating medium.

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