JP4354499B2 - Judgment method for buried piping - Google Patents

Description

  The present invention is a determination of buried piping that can be suitably performed to determine whether or not a pipe such as a gas pipe buried in the ground is the same pipe as a pipe buried in a different place. Regarding the method.

  For example, when performing water pipe construction, other pipes other than water pipes, such as medium-pressure gas pipes, may be buried in close proximity to the place to be excavated. With respect to the medium pressure gas pipe exposed by test digging or the like, it is determined which of the plurality of pipes existing at the excavation site is the same pipe as the medium pressure gas pipe exposed at the different location. Therefore, a measuring instrument called a pipe locator having a loop checker function is used.

  In the determination method of the buried pipe using this pipe locator, the exposed gas pipe is exposed to check whether the gas pipe exposed by the test digging is the same pipe as any of the plurality of pipes existing at the excavation site. An AC voltage of 2 kHz is applied between the gas pipe and each pipe at the excavation site, the impedance at that time is measured, and if the measured impedance is 50Ω or less, it is determined that they are the same pipe. (For example, refer to Patent Document 1).

JP 63-300990 A

  In the above-described conventional technology for identifying a gas pipe, the impedance changes depending on the properties of the medium, such as the diameter of the gas pipe, the specific resistance of the soil, and the distance to other adjacent pipes. There is a problem that it cannot be judged.

  The object of the present invention is to embed pipes capable of accurately determining whether or not each pipe is the same pipe regardless of the properties of a medium such as soil existing between the buried pipe and other pipes. It is to provide a determination method.

In the present invention, an AC voltage is applied in a frequency range of 50 Hz to 10 kHz between a pipe embedded in a predetermined first position and a pipe embedded in a second position different from the first position. Te, measure the current and voltage, a pipe which is embedded in prior Symbol first position, embedded and pipe is embedded in the second position you determine whether the same tube設配tube In the determination method , when there is a frequency in which the current phase advances from the voltage phase in the frequency range, the pipe embedded in the first position and the pipe embedded in the second position If it is determined that the pipes are different, and there is no frequency at which the current phase is higher than the voltage phase, the pipe embedded in the first position and the pipe embedded in the second position are the same pipe. determination method der buried piping and judging that there .

According to the present invention, when the current and voltage are measured by changing the frequency in the frequency range of 50 Hz to 10 kHz , if a frequency at which the current phase is higher than the voltage phase is confirmed, it is embedded in the first position. It is determined that the pipe that is embedded and the pipe that is embedded in the second position are different from each other, and if there is no frequency that causes the current phase to advance beyond the voltage phase, the pipe that is embedded in the first position And the pipe embedded in the second position are determined to be the same pipe.
In the case of different pipes, the phase angle θ indicating the delay of the current waveform when the frequency is 50 Hz with reference to the voltage waveform is a negative value (that is, the current phase is ahead of the voltage phase). When the frequency is increased, the phase angle θ increases. On the other hand, in the case of the same piping, the phase angle θ is a positive value at a frequency of 50 Hz, and the phase angle θ increases as the frequency increases. This has been confirmed experimentally. That is, in the case of different pipes, there is a frequency where the phase angle θ is a negative value in the frequency range of 50 Hz to 10 kHz, whereas in the case of the same pipe, the frequency range of 50 Hz to 10 kHz. It has been experimentally confirmed that there is no frequency at which the phase angle θ has a negative value.
Therefore, it is possible to accurately determine the difference between the pipes based on the measured phase angle θ regardless of the properties of the medium such as soil existing between the pipes embedded in the first and second positions. , determination accuracy is improved, it is possible to obtain a highly reliable determination result.

  Furthermore, the present invention is characterized in that after the plurality of contacts are brought into contact with each of the pipes and the continuity between the contacts is confirmed, the AC voltage is applied via one or both of the contacts. To do.

  According to the present invention, since a plurality of contacts are brought into contact with each pipe and conduction between the respective contacts is confirmed, the AC voltage is applied through one or both of the contacts. Can be determined with higher reliability.

  According to the present invention, since it is determined based on the phase angle θ between the pipes whether or not the pipes embedded in different places are the same pipe, properties such as soil existing between the pipes Regardless of, it can be determined with high accuracy.

  FIG. 1 is a plan view showing an embedded state of each of the gas pipes A and B to which the method for determining an embedded pipe according to an embodiment of the present invention is applied. In connection confirmation work of medium pressure gas pipes (hereinafter referred to as “piping”) A and B which are buried pipes, one pipe A or B buried in a predetermined first position P1 and the first position An alternating voltage is applied in the frequency range of 50 Hz to 10 kHz by the phase angle measuring device 1 between the other pipe B embedded in the second position P2 different from P1, and the current and voltage phase angle θ. Measure.

  One pipe A has a pipe part A1 buried along one road 2 and a pipe part A2 bent and connected perpendicularly to this pipe part A1 and buried along the other road 3. . The other pipe B includes a pipe part B1 extending along one road 2 and a pipe part B2 connected to the pipe part B1 and extending along the other road 3 intersecting the one road 2 Have These pipes A and B are galvanized steel pipes (nominal diameter 15A) having an outer diameter of 21.7 mm and a wall thickness of 2.8 mm.

  The phase angle measuring device 1 may be realized by an AC power supply device described later or may be realized by an LCR meter. The pipe A or B embedded in the first position P1 and the pipe B embedded in the second position P2 according to the measured value of the phase angle θ measured by the phase angle measuring apparatus 1 as described above. It is determined whether or not they are the same tube.

  Specifically, the phase angle measuring device 1 is provided with a display unit 4 for displaying the measured value of the phase angle θ, and the measurer visually observes the measured value of the phase angle θ displayed on the display unit 4. To do. When the measured value of the phase angle θ is 0 ° ≦ θ, it is determined that the pipe B embedded in the first position P1 and the pipe B embedded in the second position P2 are the same pipe, When the measured value of the phase angle θ is θ <0 °, it is determined that the pipe A embedded in the first position P1 and the pipe B embedded in the second position P2 are different pipes.

  In the phase angle measuring device 1, a plurality of contacts (2 each in the present embodiment) 5a and 5b; 6a and 6b are brought into contact with the pipes A and B, respectively, and between the contacts 5a and 5b and each contact. After confirming the continuity between the children 6a and 6b, the AC voltage is applied via either one of the contacts 5a and 5b; 6a and 6b or both 5a and 5b; 6a and 6b. Confirmation of continuity between the contacts 5a and 5b and between the contacts 6a and 6b is realized by turning on and off the lamps connected in series between the contacts 5a and 5b and between the contacts 6a and 6b. May be. When such a configuration is used, the contacts 5a, 5b and 6a, 6b are electrically connected by lighting of the lamp, and all the contacts 5a, 5b and the contacts 6a, 6b are connected to the pipe A. , B can be confirmed to be in electrical contact with each other. Further, when the lamp is turned off, it can be confirmed that at least one of the contacts 5a and 5b and at least one of the contacts 6a and 6b are not in electrical contact with the pipes A and B. .

  With such a configuration, each contact 5a, 5b; 6a, 6b is reliably connected to each pipe A, B, and an AC voltage for measuring the phase angle θ from the phase angle measuring device 1 is supplied to each pipe A. , B can be applied.

  When an AC power supply device is used as the phase angle measuring device 1 described above, a voltage-controlled waveform having a frequency to be applied is generated by a function generator, and this waveform is input to the AC power supply. Proportional alternating current is generated by current control. This alternating current is applied to each of the aforementioned contacts 5a, 5b; 6a, 6b, the current waveform and voltage waveform at that time are measured and recorded with a digital oscilloscope, and the data is written on the disk-shaped recording medium. The written data is copied to a personal computer, and the absolute value | Z | of the impedance is obtained by dividing the peak value of the voltage waveform by the peak value of the current waveform, and the phase angle θ is obtained from the phase shift.

  When an LCR meter is used as the phase angle measuring device 1, lead wires from the contacts 5a, 5b of one pipe A or the contacts 6a, 6b of the other pipe B are connected to the H of the LCR meter. The lead wire connected to the current terminal and the voltage terminal on the side, and connected to one pipe A or the other pipe B at locations other than the first and second positions P1, P2 is connected to the L-side current terminal of the LCR meter. Connect to the voltage terminal. As measurement items, these values can be obtained by setting the measurement mode of the absolute value | Z | of the impedance and the phase angle θ.

  Next, an AC voltage is applied between the pipes A and B in a frequency range of 50 Hz to 10 kHz, and the current and voltage phase angle θ is measured, so that the pipes A and B are the same at two different points. In order to confirm that the difference between the pipes can be accurately determined regardless of the properties of the medium such as the soil existing between the pipes A and B, the inventor has conducted The experiment will be described.

<Experimental equipment>
As shown in FIG. 2, the gas pipe used in the experiment is an L-shaped pipe having a length of 3.8 m and a length of 3. 5 mm made of a galvanized steel pipe of 15 A (outer diameter 21.7 mm, wall thickness 2.8 mm). A 0m straight pipe is used, and the corners of the L-shaped pipe are connected at right angles by elbows 8, and caps 9 are attached to the four ends of the L-shaped pipe and the straight pipe so that water can enter the interior. Prevented.

FIG. 3 shows a state in which the L-shaped pipe and the straight pipe are arranged in parallel to the bottom surface of the water tank used in the experiment, and FIG. 4 shows a state in which the L-shaped pipe and the straight pipe are arranged orthogonally. As shown in FIG. 3, the terminal T _{A is} located at the end of the horizontal portion of the L-shaped tube, the terminal T _{B is positioned} at the end of the straight tube, the terminal T _C is positioned at the vertical portion of the L-shaped tube, and 100 mm from the end. Provided.

<Experimental conditions>
Table 1 shows the experimental conditions.

  There are three types of media to be put in the water tank: industrial water, 0.045% salt water (hereinafter, salt water A) and 0.51% salt water (hereinafter, salt water B). The positional relationship of the gas pipe used in the experiment is two patterns that are parallel and orthogonal. The gap is 3 cases of 0 mm, 16 mm and 160 mm in each case. When the gap is 0 mm, the L-shaped tube and the straight tube are in contact. However, in the case of being parallel, since the cap portions at both ends are in contact, the gap between the parallel portions other than both ends was set to 4 mm.

<Measurement method>
Table 2 shows the results of impedance measurement using an AC power source.

The voltage amplitude V _{0P in} Table 2 is a half value of the full amplitude of the peak-to-peak, that is, a half value width. The current amplitude I _{0P is} also a half width. The absolute value | Z | of the impedance is a value obtained by dividing the voltage amplitude V _0P by the current amplitude I _0P . The delay time Δt is a delay time of the current waveform with respect to the voltage waveform. The phase angle θ is a value obtained by dividing the delay time Δt by the period and multiplying by 360 °.

  Comparing the measurement result of the LCR meter and the measurement result of the AC power supply, the absolute value | Z | and the phase angle θ of the impedance were measured for each case from case 2-1 to case 4-15 even with the LCR meter. . It was confirmed that the measurement value of the LCR meter and the measurement value by the AC power source showed good agreement between the measurement results.

<Measurement results in water>
Industrial water was put in a water tank to a depth of 106 cm, and the electrical conductivity at a water temperature of 9 ° C. and 9 ° C. was 0.202 mS / cm (specific resistance 4950 Ω · cm). In this state, the measurement was performed when the two gas pipes were parallel and the gaps were 0 mm, 16 mm, and 160 mm, and the following results were obtained.

(1) In the case of the same pipe (between T _{A and} T _C terminals), and even when different pipes (between T _{B and} T _C terminals) are in contact with zero gap, the absolute value of impedance | Z | The impedance was 2Ω or less in the following region, and the impedance increased as the frequency increased.

  (2) When the gap is 16 mm and 160 mm, the absolute value | Z | of the impedance decreases once as the frequency increases, and then increases. (If the gap is parallel and the gap is 16 mm, it will increase after 13.7 kHz.)

(3) In the case of the same pipe (between T _{A and} T _C terminals) and different pipes (between T _{B and} T _C terminals), when the gap is 0 and the phase angle θ increases from a positive value However, when the gap is 16 mm and 160 mm with different pipes, it gradually increases from a negative value (a state where the current phase is ahead of the voltage phase).

  (4) When the gap is orthogonal from 16 mm to 160 mm, the absolute value | Z | of the impedance is larger than that of the parallel case, and the initial phase angle θ (near 50 Hz) is negative, but the absolute value is parallel. It was smaller than the case.

<Measurement results in salt water A>
After putting 5 kg of salt into the water tank and circulating the water for 30 minutes, about 150 ml of the water was sampled and the conductivity was measured. As a result, it was 0.441 mS / cm at 13.8 ° C. Similarly, when 5 kg (10 kg in total) was added and the conductivity was measured, it was 0.731 mS / cm (14.0 ° C.), and the total was 14 kg, 0.938 mS / cm (13.3 ° C.). The total amount of 15 kg was 0.993 mS / cm (11.8 ° C.), so the charging was stopped. Then, when this salt water was cooled with the refrigerator and the electrical conductivity in 8 degreeC (water temperature in the water depth of 45 cm of a water tank) was measured, electrical conductivity was 1.01 * 10 < ^-3 > S / cm (specific resistance 990 ohm * cm). Met. Hereinafter, this salt water is referred to as “salt water A”. Since the amount of water is 33.4 m ³ (7.13 m × 4.42 m × 1.06 m), the weight concentration of the salt is 0.045%. As a result of measuring the absolute value | Z | of the impedance when the gas pipes are parallel in the salt water A, the following can be understood.

(1) In the case of the same pipe (between T _{A and} T _C terminals) and different pipes (between T _{B and} T _C terminals), when the gap is 0 and the contact is absolute, the absolute value | Z | The impedance was 2Ω or less in the following region, and the impedance increased as the frequency increased.

  (2) When the gap was 16 mm and 160 mm, the absolute value | Z | of the impedance once decreased with an increase in frequency, and then started to increase.

(3) In the case of the same pipe (between T _{A and} T _C terminals) and in a different pipe (between T _{B and} T _C terminals), when the gap is 0 and the phase angle θ increases from a positive value However, when the gap was 16 mm and 160 mm with different tubes, it gradually increased from a negative value (a state in which the current phase is ahead of the voltage phase).

  (4) When the gap is 16 mm and 160 mm orthogonal, the impedance is greater than when parallel, and the initial (near 50 Hz) phase angle θ is negative, but its absolute value is smaller than when parallel. It was.

  (5) When the gap was 16 mm and 160 mm, the absolute value of the impedance was smaller and the absolute value of the initial phase angle (negative value) was larger than when only the industrial water was used.

<Relationship between specific resistance and impedance of medium>
In the above experiment, the measurement result of the impedance was confirmed for each measured medium. Here, the specific resistance was examined as a parameter for each experimental condition. Only industrial water, salt water A and salt water B are expressed as 5000Ω · cm, 1000Ω · cm, and 100Ω · cm, which are approximate values of specific resistance, respectively. Regarding the absolute value of impedance, the minimum value regarding the frequency of the absolute value of impedance when the specific resistance of the medium is 5000 Ω · cm is the minimum value regarding the frequency of the absolute value of impedance when the specific resistance of the medium is 1000 Ω · cm. It was about 5 to 6 times. This corresponds to the fact that the specific resistance has increased about five times. However, when the specific resistance of the medium was 100 Ω · cm, the minimum value of the absolute value of the impedance was larger than expected with this ratio.

Regarding the measurement result of the same tube (between T _{A and} T _C terminals), when measuring the absolute value of impedance and the phase angle θ when parallel, the measurement result shows almost the same value regardless of the specific resistance of the medium. It was. This was a natural result because most of the current was flowing through the lead wires and the L-shaped gas tube.

  Assuming that the proportionality is established with respect to the two-dimensional in-plane impedance of the gas pipe, the length is the same 3 m, and when the diameter of the galvanized gas pipe is increased to 200A or 300A, as shown in Table 3 Furthermore, even when the gap is 1.6 m or 2.3 m, the impedance becomes 50 Ω or less at 50 Hz to 10 kHz in water having a specific resistance of 5000 Ω · cm or less.

  Table 4 shows the absolute value | Z | of impedance and the phase angle θ at frequencies of 50 Hz, 500 Hz, and 1990 Hz.

  When the gap was 16 mm or 160 mm, it was confirmed that the phase angle θ of the impedance between BC terminals at 50 Hz was clearly a negative value from −27 ° to −8 °.

<Examination by equivalent circuit model>
(1) C-only one-element model Here, the above-described measurement results are examined using an equivalent circuit model. Depending on the experiment, one C-only element, two LR elements, an LCR five-element model, and a five-element model including Warburg impedance are considered.

First, the results of impedance measurement when the medium is air were examined using a one-element model with only the capacitance C, and whether a two-dimensional analytical solution of capacitance can be used in a three-dimensional experiment was examined. The complex impedance Z of the equivalent circuit model when there is one capacitor is expressed by the following equation.

Here, ω is an angular frequency (= 2πf), C is a capacitance of the capacitor, and j is an imaginary unit (j ² = −1). Accordingly, the absolute value | Z | of the impedance and the phase angle θ are expressed as follows.

If the absolute value of the impedance at a specific frequency is found from the equations (2) and (3), the capacitance C can be obtained by the following equation.

  The capacitance was calculated from the absolute value of impedance at 500 Hz as a representative value. Table 5 shows a comparison result between the measurement result and the calculated value.

The calculated values in Table 5 are values obtained by multiplying the theoretical value of capacitance per unit length by a length of 3 m. The calculated values are all calculated in parallel. Therefore, the ratio between the measured value and the calculated value is smaller in the case of orthogonality. Regarding the capacitance between the L-shaped tube and the straight tube, the measured value and the calculated value are both on the order of 10 ⁻¹¹ , so the analytical solution can be used for studying the order. Possible causes of the error include applying a two-dimensional analytical solution to a three-dimensional shape close to two dimensions and a capacitance other than between the gas pipes.

FIG. 5 shows a comparison between the measured value and the calculation result according to Formula 2 of the one-element model (C = 4.55 × 10 ⁻¹¹ F) with respect to the absolute value of the impedance when the gap is 16 mm in parallel in the air. A relatively good agreement.

<Examination by LR two-element model>
Next, consider the data obtained by measuring the impedance between T _A terminal and T _C terminal of the same L-shaped tube, obtaining the value of the resistor R ₂ and the impedance L due to the influence of the lead wire of the measurement circuit. In this case, since there is no portion corresponding to the capacitor C, a two-element equivalent circuit model as shown in FIG. 6 is considered.

The complex impedance Z, its absolute value | Z |, and the phase angle θ are expressed by the following equations.
Z = R ₂ + jωL (5)
| Z | = {R ₂ ² + (ωL) ² } ^1/2 (6)
θ = tan ⁻¹ (ωL / R ₂ ) (7)

Varying the _{R 2} and L of Formula 6 and Formula 7, when determining the best fit _{R 2} and L and the measurement data, respectively the 0.18Ω and 2.0 × ^{10 -5} H. FIG. 7 shows a comparison between the measured value and the calculated value regarding the absolute value of the impedance at this time. Further, FIG. 8 shows a comparison between the measured value and the calculated value regarding the phase angle θ. It can be seen that there is a very good agreement.

Here, 0.18Ω of the resistance R ₂ is a value substantially corresponding to the resistance of the lead wire. On the other hand, the inductance L will be considered below as the impedance of a rectangular circuit.

The impedance of a rectangular circuit whose cross section is a lead wire having a radius r and whose one side is a and whose other side is b is given by Equation 8.

Substituting r = 1 × 10 ⁻³ m, a = 3 m, and b = 1 m as approximate dimensions of the measurement circuit into this equation 8a, the following equation is obtained.
L = 1.09 × 10 ⁻⁵ [H] (8b)

  This value is 1 / 1.83 of the best fit value, but the order is correct. Since a part of the measurement circuit is a gas pipe and there are other factors such as the presence of a parallel line of about 8 m from the circuit to the measuring instrument, an error may have occurred.

In the next examination, the resistance of the lead wire uses this R ₂ value of 0.18Ω, and the measurement circuit impedance uses this L value of 2.0 × 10 ⁻⁵ H.

<Examination by LCR 5-element model>
Next, in water or in saline, in a state where there is a gap, the impedance measurements between T _C terminal T _B terminal and the L-shaped tube straight tube, consider an equivalent circuit model of 5 elements shown in FIG. The inside of the frame is a portion of two gas pipes, and an equivalent circuit model used in the AC impedance method is used in this portion. The left part is the aforementioned two-element model.

  The complex impedance, its absolute value, and phase angle θ in the case of this five-element model are as follows.

For example, if the gap is 160 mm in water and the gap is 160 mm, the values of R _1, R _{3, and} C in Equation 10 and Equation 11 are changed, the measured data are compared, and the value that best fits the measured data is obtained. ,It is as follows.
R ₁ = 24.82Ω, R ₃ = 14Ω, C = 3.0 × 10 ⁻⁴ F

  A comparison between the measured value and the calculated value of the absolute value of the impedance at this time is shown in FIGS. 10 and 11 (up to 2 MHz). Moreover, the comparison between the measured value and the calculated value of the phase angle θ is shown in FIGS. 12 and 13 (up to 2 MHz). The calculated and measured values show a relatively good agreement.

<Examination by equivalent circuit using Warburg impedance>
When the current is conducted by ions and the rate limiting of the ion conduction is the material diffusion rate, Warburg impedance is used as an equivalent circuit element for this phenomenon. This impedance Zw is given by the following equation.

  Here, W is the Warburg coefficient, and ω is the angular frequency (= 2πf). In the case of only Warburg impedance, the absolute value is expressed by Equation 13 and the phase angle θ is expressed by Equation 14.

Warburg impedance, in most cases, or charge transfer resistance R ₁ is connected in series, the electric double layer capacitance C appears together are connected in parallel, it is difficult determination, the determination to create a drawing, such as: can do.

First, as shown in FIG. 14, the relationship between the real part (Z ′ = Re (Z)) of the impedance of the gas pipe and the medium part and 1 / √ω is plotted. Further, the value obtained by multiplying the imaginary part of impedance (Z ″ = Img (Z)) by −1 and 1 / √ω is plotted. Check if these two plots are both straight and parallel. Also check that the straight line of the imaginary part passes through the origin. At this time, the value at the point where the straight line of the real part intersects the imaginary axis is the charge transfer resistance R ₁ connected in series.

  Here, as can be seen from Equation 12, the slope of the straight line between the real part and the imaginary part is the Warburg coefficient W.

Next, as shown in FIG. 15, a plot of the logarithm of the absolute value | Z−R ₁ | of the impedance obtained by subtracting R ₁ from the impedance of the gas pipe and the medium portion and the logarithm of the frequency is created. In the case of a normal R and C equivalent circuit model, this slope is −1, whereas in the case of Warburg impedance, the slope of this line is −½ according to Equation 13. When the above check conditions are satisfied, this phenomenon is a conductive phenomenon that can be modeled by Warburg impedance.

  Further, in the case of Warburg impedance, the complex impedance diagram shown in FIG. 16 is a straight line with a slope of 45 ° as expected from Equation 12, so FIG. 14 is also an index for determination.

Next, measurement data using Warburg impedance will be examined. As a whole equivalent circuit model, a five-element model as shown in FIG. 17 is considered. Here, L is the impedance of the measurement circuit, R ₂ is the lead wire resistance, which are 2.0 × 10 ⁻⁵ H and 0.18Ω, respectively, as studied in the two-element model. The gas pipe and the medium part are models composed of Warburg impedance, charge transfer resistance R ₁ and electric double layer capacitance C.

  If the combined impedance of the three elements of the gas pipe and the medium is Zp, this impedance Zp is given by the following equation.

  Therefore, the impedance Z of the entire five elements is as follows.

Here, since R ₂ and L are known, the remaining R ₁ , W, and C may be obtained.
Next, as an example, it will be examined whether Warburg impedance can be applied in the case of underwater, parallel, and a gap of 160 mm.

First, a complex impedance diagram is shown in FIG. As the frequency increases from 50 Hz, it is linearly toward the lower left direction. Next, a Warburg plot as shown in FIG. 14 is shown in FIG. The upper real part line and the lower imaginary part line are both straight and parallel, and the imaginary part line is toward the origin. When two points in the low frequency range of 50 Hz and 62.9 Hz were selected and the Warburg coefficient W was determined from the average of the slopes of the two curves, it was 91.69 Ω / √s. Further, regarding the real part line above, R ₁ obtained from the value of the imaginary axis at the intersection of the imaginary axis and the straight line connecting the two points corresponding to these two frequencies was 23.63Ω.

FIG. 20 shows a plot of the relationship between log | Zw | and logf with respect to Zw obtained by subtracting the value of R ₁ from the measured value Zp of the impedance of the gas pipe and the medium. In the figure, the slope of a point corresponding to two points in the low frequency region with frequencies of 50 Hz and 62.9 Hz was found to be −0.43, which was close to the Warburg impedance slope of −0.5. From the above, it is considered appropriate to model this measurement result with Warburg impedance.

  Since it was difficult to determine the remaining coefficient C shown in FIG. 17 from the experimental data, the relative permittivity of water (from a water temperature of 7 ° C.) is added to the measured value of the capacitance in the air described above. 9) and the relative dielectric constant of air, 1.000536. Table 6 shows the predicted values of capacitance.

The constants of the equivalent circuit obtained as described above are as follows.
L = 2.0 × 10 ⁻⁵ [H]
R2 = 0.18 [Ω]
R1 = 23.63 [Ω]
W = 91.69 [Ω / √s]
C = 2.80 × 10 ⁻⁹ [F]

  FIG. 21 shows a comparison between the absolute value of the impedance calculated by Equation 16 and the measured value using the values of these constants. FIG. 22 shows the logarithmic display of the horizontal axis with the frequency range up to 1 MHz. FIG. 23 shows a comparison between the calculated value by Equation 16 and the experimental value regarding the phase angle θ. FIG. 24 shows a logarithmic display of the horizontal axis with a frequency range of 1 MHz or less. As is apparent from these figures, it was confirmed that the measured values and the calculated values by the five-element equivalent circuit model including Warburg impedance showed a relatively good match, and the other cases were the same.

  As is clear from the above examination results, the state in which industrial water is put in the water tank (specific resistance is about 5000 Ω · cm), and the specific resistance is about 1000 Ω · cm and about 100 Ω · cm by adding salt. The results of an experiment in which two gas pipes with a diameter of 21.7 mm (nominal diameter 15 A) and a length of 3 m are installed in a medium of various kinds and the impedance between them is measured at a frequency of 50 Hz to 10 kHz are summarized as follows. It is as follows.

  (1) When two galvanized gas pipes (white tube) with a diameter of 21.7 mm (nominal diameter 15 A) and a length of 3 m are in water with a specific resistance of 5000 Ω · cm, there is a gap of 160 mm between them. However, the measured value that the absolute value | Z | of the impedance was 40Ω or less from 50 Hz to 10 kHz was obtained. When the medium was salt (specific resistances 1000 Ω · cm and 100 Ω · cm), the absolute value of the impedance further decreased. It has been confirmed that the conventional criterion 50Ω may not be applicable.

  (2) The measurement result of (1) corresponds to the case where two gas pipes having a diameter of 216.3 mm (nominal diameter 200 A) and a length of 3 m are separated by 1.6 m, assuming that the double-sided similarity rule holds. .

(3) The impedance phase angle θ is 3 ° at 50 Hz in the case of between the T _{A and} T _C terminals of the same tube and between the T _{B and} T _C terminals where the two gas tubes are in metal contact. It is a positive value, and the phase angle θ increases as the frequency increases. In contrast, when the gap is between the _T B -T _C terminal of 16mm and 160 mm, the phase angle theta, at -8 ° and a negative value from -27 ° at frequency 50 Hz (current phase leads the voltage phase) Yes, and then increases with increasing frequency.

  (4) As a result of examining the measurement data using several equivalent circuit models, it became clear that the measurement results can be simulated by a five-element equivalent circuit model including Warburg impedance. The Warburg impedance is an impedance element model used when the conductive behavior is governed by the diffusion process of a substance.

  (5) As a result of predicting a case of 50 Hz or less using a five-element equivalent circuit model including Warburg impedance, a result was obtained that the phase angle θ approaches −45 ° as the frequency decreases.

  (6) When the gas pipes are in contact with each other, the impedance is small and it is difficult to determine the same pipe, but it is possible to determine if there is a coating such as asphalt jute winding on the surface. .

It is a top view which shows the embedment state of each gas pipe A and B to which the determination method of embedment piping of one Embodiment of this invention is applied. It is a figure which shows the gas pipes A and B used for experiment. It is a figure which shows the state which immersed gas pipes A and B in the water tank used in experiment in parallel, FIG. 3 (1) shows the plane, FIG. 3 (2) shows the cross section. It is a figure which shows the state which made gas pipes A and B orthogonally immersed in the water tank used for experiment, FIG. 4 (1) shows the plane, FIG. 4 (2) shows the cross section. It is a graph which shows the comparison of the measured value of impedance | Z | in the state which immersed gas pipes A and B in air with a gap of 16 mm in parallel, and the calculated value by a 1 element equivalent circuit model. It is a diagram showing a two-element equivalent circuit model of the LR _2. It is a graph which shows the comparison with the measured value of impedance | Z | in the state which immersed gas pipes A and B in salt water A in parallel with the gap of 160 mm, and a calculated value. It is a graph which shows the comparison with the measured value and calculated value of phase angle (theta) in the state which immersed the gas pipes A and B in the salt water A in parallel with the gap of 160 mm. It is a figure which shows a LCR5 element equivalent circuit model. It is a graph which shows the comparison with the measured value and calculated value of impedance | Z | with a frequency of 10 kHz or less in the state where gas pipes A and B were immersed in water with a gap of 160 mm in parallel. It is a graph which shows the comparison with the measured value and calculated value of impedance | Z | with a frequency of 2 MHz or less in the state where gas pipes A and B were immersed in water with a gap of 160 mm in parallel. It is a graph which shows the comparison with the measured value and calculated value of phase angle (theta) of the frequency of 10 kHz or less in the state which immersed the gas pipes A and B in water with the gap of 160 mm in parallel. It is a graph which shows the comparison with the measured value and calculated value of phase angle (theta) of the frequency of 20 MHz or less in the state which immersed the gas pipes A and B in water with the gap of 160 mm in parallel. It is a Warburg plot figure. It is a Bode diagram of Warburg impedance. It is a complex impedance diagram. It is a figure which shows the 5 element equivalent circuit model using Warburg impedance. It is a complex impedance figure in the state where gas pipes A and B were immersed in water with a gap of 160 mm in parallel. It is a Warburg plot figure in the state where gas pipes A and B were immersed in water with a gap of 160 mm in parallel. It is a graph which shows the relationship between log | Zw | and log (f) in the state which immersed the gas pipes A and B in water in parallel with the gap of 160 mm.

It is a graph which shows the comparison of the measured value of impedance | Z | in the state which immersed gas pipes A and B in water in parallel with the gap of 160 mm, and the calculated value by the equivalent circuit model of Warburg impedance. It is a graph which shows the comparison of the measured value of impedance | Z | with a frequency of 1 MHz or less and the calculated value by the equivalent circuit model of Warburg impedance in the state where the gas pipes A and B in water are immersed in parallel with a gap of 160 mm. It is a graph which shows the comparison with the measured value of the phase angle (theta) in the state which immersed the gas pipes A and B in water in parallel with the gap of 160 mm, and the calculated value by the equivalent circuit model of Warburg impedance. It is a graph which shows the comparison with the measured value by the equivalent circuit model of Warburg impedance with the measured value of phase angle (theta) below 1 MHz in the state where the gas pipes A and B were immersed in water with a gap of 160 mm in parallel.

Explanation of symbols

Phase angle measuring device 1
Road 2
Contacts 5a, 5b; 6a, 6b
Piping A, B
1st position P1
Second position P2
Phase angle θ

Claims (2)

An AC voltage is applied in a frequency range of 50 Hz to 10 kHz between a pipe embedded in a first position determined in advance and a pipe embedded in a second position different from the first position. the voltage is measured, met determination method of the preceding SL and has pipe is embedded in the first position, embedded and pipe is embedded in the second position you determine whether the same tube設配tube And
If there is a frequency in which the current phase is ahead of the voltage phase in the frequency range, it is determined that the pipe embedded in the first position and the pipe embedded in the second position are different pipes. However, when there is no frequency at which the current phase advances more than the voltage phase, it is determined that the pipe embedded in the first position and the pipe embedded in the second position are the same pipe. Judgment method of characteristic buried piping . After the confirming the conduction between each contact child by contacting a plurality of contacts in the pipes, according to claim 1 Symbol, characterized in that for applying the AC voltage either or through both of the respective contact Judgment method of listed underground piping.

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