JP2750249B2 - Detector for dissolved gas in oil for diagnosis of OF cable insulation deterioration - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting dissolved gas in oil which is suitable for use in diagnosing insulation deterioration of an OF cable or the like.

[0002]

2. Description of the Related Art Conventionally, insulation deterioration diagnosis of an OF cable or the like is performed whenever necessary by collecting insulation oil to be diagnosed from a joint box of an actual line, and dissolving a gas dissolved in the insulation oil into a mechanical device such as a Tepler pump or a piston. After the separation and extraction using a conventional method, the presence or absence or concentration of the gas is quantitatively analyzed using chromatography. This traditional method is too laboratory and inefficient,
There are several problems, such as a long time required for quantitative analysis of gas.

On the other hand, in the field of transformers, an insulation deterioration diagnosis method as shown in FIG. 1 has been proposed. According to this method, a gas extraction chamber 3 containing a gas separation filter 4 is disposed in a part of a transformer container 1, and a gas dissolved in the insulating oil 2 is separated and extracted by using the filter, and the gas is stored in a gas reservoir 7. The portable gas measuring device 8 and the diagnostic device 9 are connected to the gas extraction chamber 3 when the gas reaches the equilibrium state, and the presence or concentration of the gas in the gas reservoir 7 is measured. In this way, insulation deterioration diagnosis of the transformer is performed.

The gas separation filter 4 is formed by forming a semipermeable membrane 6 made of a polymer material on one side of a support disk 5 made of a porous metal. As this kind of porous metal, there is, for example, a sintered body of stainless steel, and as the polymer material, there is, for example, PFA (tetrafluoroethylene-perfluoroalkyl ether copolymer), which is one kind of fluororesin. The semi-permeable membrane 6 is formed by heating and fusing a PFA film to one surface of the support disk 5. The gas measuring device 8 has a built-in contact combustion type gas sensor or semiconductor type gas sensor (not shown) for detecting gas, and a diagnostic device 9 is a microcomputer required for diagnosing insulation deterioration of a transformer. , Display / recorder, power supply, etc. (not shown).

[0005] The latter method using a gas separation filter is excellent in that the insulation deterioration diagnosis of a transformer can be performed automatically and accurately. In principle, the method is also used for the insulation deterioration diagnosis of an OF cable. It is also possible. However, in the case of an OF cable (especially, a 275 kV-class OF cable), since the oil pressure of the insulating oil inside the joint box is as large as 8 kg / cm ^{2 at the} maximum, a gas separation filter having the same size as that for the transformer diagnosis was used. In this case, the mechanical strength is insufficient, and the central portion expands in a convex shape and bursts. For this reason, the present inventors made the support disk thicker,
An attempt was made to provide the required strength by reducing the gas permeation area, but in this case, the permeability of the gas dissolved in the oil was extremely reduced, and the gas permeated through the gas separation filter was in an equilibrium state. Turns out to require a long time to reach.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to sufficiently withstand the oil pressure even when the pressure of the insulating oil to be diagnosed is large. It is another object of the present invention to provide a novel oil-dissolved gas detection device capable of efficiently separating and extracting a dissolved gas in oil in a short time.

[0007]

The gist of the present invention is to provide an OF card.
In a device for detecting dissolved gas in oil for diagnosis of cable insulation deterioration,
The oil-dissolved gas detector is an OF cable joint
One of the two fittings on the box
A cylindrical structure made of porous metal
-Shaped support member and an organic polymer material on an outer surface of the support member.
Dissolved gas in oil composed of semipermeable membrane formed by electrostatic coating
Filter formed on the outer periphery of the filter
A first space for filling with insulating oil;
Second space for storing the permeated gas formed inside the
And the joint space is provided in the first space.
Oil sampling pipe connected to the plug of
And a discharge pipe for discharging the insulating oil to be diagnosed.
In the space of No.2, there is a gas detector using infrared absorption characteristics.
It has a step. In the device for detecting a dissolved gas in oil according to the present invention, a cylindrical member is used as a support member of the gas separation filter, and a semipermeable membrane is formed on an outer surface of the support member. The gas separation filter thus configured can have a sufficiently large effective gas permeation area while maintaining sufficient mechanical strength, and can efficiently perform separation and extraction of dissolved gas in oil. I can do it.

However, if the support member of the gas separation filter is formed in a cylindrical shape, its shape becomes more complicated than that of a disk, so that a PFA film or the like is heated and fused to form a semipermeable membrane. Although difficult, such difficulties can be easily overcome by utilizing electrostatic coating methods. That is, the PF is converted into a solution by adding an appropriate solvent.
Since a polymer material such as A can be supplied as a paint to a cathode of an electrostatic coating apparatus, a cylindrical support member, which is a conductive material, is used as an anode (object to be coated). By applying an electrostatic field therebetween, a semi-permeable membrane having a desired thickness can be easily formed on the supporting member.

A first space for filling the insulating oil to be diagnosed is formed around the gas separation filter, and a second space for storing the permeated gas is formed inside the filter. I do. Inside the second space (gas reservoir)
It is desirable to incorporate a gas detection means that utilizes infrared absorption characteristics. This type of means can detect the presence or concentration of dissolved gas in oil with higher sensitivity than a conventional catalytic combustion type gas sensor or semiconductor type gas sensor.

[0010]

In general, when hydraulic pressure (equally distributed surface load) is applied to one side of a disk having a fixed periphery, the maximum bending stress σ _max acting on the center of the disk is expressed by the following equation. Can be done.

[0011]

(Equation 1) Here, P ₁ : oil pressure R: pressure receiving radius of disk T: plate thickness of disk

In equation (1), assuming that P ₁ is 8 kg / cm ² , which is the maximum oil pressure value for a 275 kV class OF cable,
And the maximum allowable bending stress σ of the disk within the elastic limit
Assuming that _max is 3 kg / mm ² which is the yield point strength (actually measured value) of the stainless steel sintered body (SUS316), the relationship between the pressure receiving diameter φ _D (= 2R) of the disk and the plate thickness T is obtained. The relationship shown in FIG. 2 is established. Therefore, if the ideal thickness T of the disk is 2 mm in consideration of the workability, gas permeability, etc. of the stainless steel sintered body, the disk is used as a support member of the gas separation filter. It can be seen that the desired pressure receiving diameter φ _D in this case is 28 mm, and the effective surface area A in contact with the insulating oil in that case is 616 mm ² .

Next, a hydraulic pressure (equally distributed surface load) is applied to the outer periphery of the cylinder.
, The buckling pressure (buckling strength) P _cr when the cylinder buckles under external pressure can be generally expressed by the following equation. However, if the ratio L / phi _d of the length L and outer diameter phi _d of the cylinder is 2.5 or more, it is necessary to consider the length of the cylinder in a strict sense, here, easy Therefore, it is assumed that the ratio of both L / phi _d is approximately 1.

[0014]

(Equation 2) Where E: Young's modulus I: Second moment of area ν: Poisson's ratio r: Outer radius of cylinder

[0015] Here, the second moment I are generally from t ^3/12 (where t is the thickness of the cylinder) can be expressed as, a Poisson's ratio ν of comparable conventional cast iron 0.2
Assuming 3, Equation 2 can be rewritten as:

[0016]

(Equation 3)

In equation (3), the maximum hydraulic pressure P on the outer periphery of the cylinder
_max is equal to the buckling strength P _cr, and the Young's modulus E of the cylinder is 1500 kg / mm of the sintered stainless steel (SUS316).
² (measured value) and the outer diameter of the cylinder φ _d (= 2
When the relationship between r) and the plate thickness t is obtained, the relationship as shown in FIG. 3 is established. For this reason, as in the case of the above-mentioned disk, if the ideal thickness of the cylinder is 2 mm, the pressure receiving outer diameter φ _{d of the} cylinder that can be used within the elastic limit (= 2r)
Is 68 mm, and if the length L of the cylinder is 50 mm considering practicality when used as a gas separation filter, the effective surface area A in contact with the insulating oil is 1 mm.
0700 mm ² .

On the other hand, regarding the permeation of dissolved gas in oil through a semipermeable membrane made of a polymer material, the following relationship is generally established.

[0019]

(Equation 4) Here, P ₂ : gas partial pressure after passing through the semipermeable membrane (P _a ) k: equilibrium constant (determined by oil temperature and gas type) (P _a / pp
m) v: concentration of dissolved gas in oil at 20 ° C under atmospheric pressure (pp
m) alpha: permeability coefficient in oil dissolved gas ^{(l · m / m 2 ·} s · P a) a: thickness of the semipermeable membrane (m) V: volume of the gas reservoir space semipermeable membrane permeated gas (l ) A: Effective surface area of the semipermeable membrane (m ² ) τ: Permeation time of gas

[0020] In Formula 4, in the assumption that the gas partial pressure P _a post partial pressure and the semipermeable membrane permeation oil dissolved gas has reached an equilibrium state, the value of _{P 2 / (k × v)} 0 .9 is enough. Therefore, the effective surface area A obtained from Equation 1 is 616 mm ²
Is used as a support member, and a thickness of 7
For a conventional gas separation filter having a 5 μm heat-fused PFA semipermeable membrane formed thereon, the time required for dissolved gas in oil (eg, CH ₄ gas) to permeate through the filter and reach an equilibrium state is calculated using Equation 4. As a result, the time is
That's 458 days. However, since the α / a value at an oil temperature of 40 ° C. is assumed to be 1.5 × 10 ⁻¹⁰ (l / m · s · P _a ) and compared with the case of the present invention described later, The volume V of the gas storage space for the membrane-permeable gas is 0.161 (l).
Was assumed.

On the other hand, the effective surface area A obtained from the equation (3)
There using cylindrical is 10700Mm ² as a support member,
For the gas separation filter of the present invention in which a 95 μm-thick PFA semipermeable membrane is formed on its outer peripheral surface by using an electrostatic coating method, the time required to reach the same equilibrium state is calculated using Equation 4. The time is only about 18 days. However, when the oil temperature is 40 ° C., the α / a value is 1.
^{39 × 10 -10 (l / m} 2 · s · P a) [experimental value], the volume V (cylindrical inner volume) of the gas reservoir space is assumed to 16100mm ^2.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to one embodiment shown in FIGS. In this embodiment,
As shown in FIG. 4, a joint box 12 which is a connection portion of the OF cable 11 is provided with two plugs 13a and 13b at front and rear positions in the longitudinal direction of the cable, and one of them (13a) is provided. On the other hand, a dissolved gas in oil detection device 16 was connected via a stop valve 14. This device was provided with an oil drain valve 15 and connected to an optical cable 17 for transmitting the detected gas concentration to a diagnostic device (not shown).

FIG. 5 shows the detailed structure of the dissolved gas in oil detecting device 16. The inside of this device was partitioned back and forth by an intermediate partition plate 18, and a cylindrical support member 19 was disposed in one of the spaces (left side in the drawing). Cylindrical support member 19
Outside space constitutes an oil reservoir 20, and its inside space constitutes a gas reservoir 21. The space on the other side (right side in the drawing) of the intermediate partition plate 18 forms an optical fiber storage section 22. The cylindrical support member 19 is made of a porous metal made of a sintered body of stainless steel, and has a P
The semi-permeable membrane 23 was formed by electrostatically applying an FA paint. These constitute a gas separation filter as a whole. The oil reservoir 20 includes a joint box 12.
An oil sampling pipe 24 for introducing the insulating oil to be diagnosed from (see FIG. 4) and an oil drain pipe 25 for discharging the insulating oil to be diagnosed from the oil reservoir 20 are provided.

Two reflecting mirrors 26a and 26b opposed to each other at an angle of 45 degrees are fixed to fixing corners 27a and 27b at one corner in the cylindrical gas reservoir 21 formed by the supporting member 19.
Arranged through. These reflecting mirrors are connected to the intermediate partition plate 18.
And a light emitter 28a for emitting infrared rays toward one reflecting mirror 26a and a reflected light returning from the other reflecting mirror 26b. The light receiving device 28b for taking in the intermediate partition plate 1
8 attached. The light-emitting device 28a and the light-receiving device 28b each include a lens 29, a receptacle 30, and an optical connector 31. Further, optical fibers 32a and 32b extending from the optical cable 17 were connected to the optical connectors 31 of the light emitting device 28a and the light receiving device 28b, respectively. Reference numeral 33 denotes an optical cable 17 on the wall of the optical fiber housing 22.
Cable gland for fixing

The insulating oil to be diagnosed in the joint box 12 shown in FIG.
The oil reservoir 20 of the gas detector 16 through the oil collecting pipe 24
The dissolved gas in the oil is separated and extracted by the gas separation filter including the cylindrical support member 19 and the semipermeable membrane 23 and accumulated in the gas reservoir 21. The density is detected by an optical system including the reflectors 26a and 26b, the light emitter 28a and the light receiver 28b, and the detection information is sent to a diagnostic device (not shown) via the optical cable 17. In the diagnostic device, by analyzing the wavelength band of infrared absorption,
The presence or absence and concentration of dissolved gas in oil are examined to diagnose the degree of insulation deterioration of the OF cable.

[0026]

According to the gas-dissolved gas detection apparatus of the present invention, the gas separation filter is formed by forming a semi-permeable membrane on the cylindrical support member, so that the mechanical strength of the filter is sufficiently large. You can do it. For this reason, the device has a significantly improved hydraulic resistance and gas permeability as compared with a conventional gas detection device that forms a gas separation filter by forming a semipermeable membrane on a disk-shaped support member. It is possible to detect the dissolved gas in the oil such as the OF cable at an early stage to perform the insulation diagnosis.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing an example of a conventional dissolved gas detection device in oil.

FIG. 2 is a characteristic curve diagram for explaining the relationship between the thickness of the disk and the pressure receiving diameter when hydraulic pressure is applied to one surface of the disk.

FIG. 3 is a characteristic curve diagram for explaining the relationship between the plate thickness of the cylinder and the pressure receiving outer diameter when hydraulic pressure is applied around the cylinder.

FIG. 4 is a schematic view of a joint box portion of an OF cable to which an embodiment of the apparatus for detecting a dissolved gas in oil according to the present invention is applied.

FIG. 5 is a cross-sectional view showing a detailed structure of one embodiment of a device for detecting a dissolved gas in oil according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transformer container 2 ... Insulated oil to be diagnosed 3 ... Gas extraction chamber 4 ... Gas separation filter 7 ... Gas reservoir 8 ... Gas measuring device 9 ... Diagnostic device 11 ... OF cable 12 ... Joint box 16 ... Gas detection device 17 ... Optical cable 18 intermediate partition plate 19 cylindrical support member 23 semi-permeable membrane 26 reflecting mirror 28a light emitting device 28b light receiving device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akiyuki Nakamura 5-1-1, Hidaka-cho, Hitachi City, Ibaraki Prefecture Inside the Opto-System Research Laboratories, Inc. (72) Inventor Mitsuhiro Sato Date, Hitachi City, Ibaraki Prefecture 5-1-1 Takamachi Inside the Hidaka Plant of Hitachi Cable Co., Ltd. (56) References JP-A-4-102047 (JP, A) JP-A-3-32725 (JP, A) JP-A-4-64039 (JP, A) JP-A-4-353739 (JP, A) JP-A-59-10349 (JP, A) JP-A-55-87028 (JP, A) JP-A-48-12481 (JP, A) Kaihei 5-72123 (JP, A) Shokai 2-63449 (JP, U) Shokai 61-147962 (JP, U)

Claims (1)

(57) [Claims] 1. Dissolved gas in oil for diagnosis of OF cable insulation deterioration
In the detection device, the device for detecting dissolved gas in oil is an OF type.
Cable joint box.
A structure connectable to one of the stoppers, comprising a cylindrical support member made of porous metal and a semi-permeable membrane formed by electrostatically coating an organic polymer material on the outer surface of the support member. A filter for separating dissolved gas in oil, a first space formed on the outer periphery of the filter for filling the insulating oil to be diagnosed, and a second space for storing a permeated gas formed inside the filter. And the first space includes a front space.
Connected to the connection box of the joint box
Oil sampling pipe for introducing oil and discharge for discharging the insulating oil to be diagnosed
A tube, wherein the second space has an infrared absorption characteristic.
OF card characterized by comprising gas detection means used
Detector for dissolved gas in oil for diagnosis of cable insulation deterioration .