JPS5827040A - Detecting method for short-circuiting spot at conductor-covered insulating pipe - Google Patents

Abstract

PURPOSE:To detect a spot where an outer covering material and a core tube short-circuit, by a method wherein a conductive core tube, an outer periphery of which a conductive sheathing material covers through the medium of an electrically insulating heat insulator 3, is earthed, and a periodical voltage is applied all the way through to the outer sheathing material and the core tube to detect a leak magnetic field or a change in the leak magnetic field. CONSTITUTION:A conductor-sheathed insulating pipe 1 is constituted such that a conductive outer sheathing material 4 is formed on an outer periphery of a conductive core tube 2 through the medium of an electrically insulating heat insulator 3. When detecting a spot 5 where the core tube 2 and the outer sheathing material 4 short-circuit, the core tube 2 is earthed, and an outer of an oscillator 7, employing, for example, a fork oscillator, is applied all the way through to the core tube 2 and the outer sheathing material 4 through a diode (D) 14, in parallel with which a switch (S) 13 is placed. If, with a S 13 closed, a voltage is applied, and an electrostatic induction detector 8 is caused to approach the insulating pipe 1, a leak electric field is detected irrespective of the presence of a short-circuiting spot, and a speaker 10 sounds. If, which a S 13 closed, a rectified voltage is applied through a D14, and in the case of no short-circuit spot, no current flows after charging by the use of an electrostatic capacity, and it is not detected by a detector. But if there is a short-circuiting spot, it can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a novel method for detecting short circuits in insulated pipes such as hot water supply pipes, particularly conductor-coated insulated pipes whose outer periphery is coaxially coated with a conductive jacket material. It is something to do.

In general, hot water pipes are installed indoors in locations that are difficult to see, such as under the floor, so when installing the interior of the room after piping, the nails used for this are driven into the hot water pipes by mistake. Even if this happens, we do not notice it, so after completing the interior work, we detect whether or not there is any damage to the hot water pipe due to the nailing, and the location of the damage and repair it to prevent water leakage accidents from the hot water pipe. It is necessary to prevent it. Therefore, the 8th
It has been proposed to use a conductive coated heat insulated pipe (hereinafter abbreviated as heat insulated pipe) 1 as shown in the figure as a hot water supply pipe. This heat insulating pipe 11d is made by covering a core pipe 2 made of a nailed pipe with a conductive jacket material 4 such as carbon rubber through an insulating heat insulating material 3 such as polyurethane foam. If a DC voltage is applied between the outer covering material 4 and the core tube 2 and the outer covering material 4 are short-circuited by the nail 5 due to the above-mentioned nailing, a current will flow, and when they are not nailed, insulation will flow. The resistor prevents current from flowing, making it easy to determine whether or not a nail has been driven. In addition, by measuring the DC resistance of the insulated pipe 4 and calculating the distance to the nailing point where the short circuit occurred from the measured resistance value, it is possible to know the distance from the measurement point to the nailing point. This makes it easier to find and repair nailing points. However, in reality, the resistance value of the jacket material 4 is not constant and varies, and the resistance value is not constant at the joint part of the piping path of the insulated pipe 1, so that short circuits obtained by the above DC resistance method can be avoided. The problem was that it was difficult to ensure the accuracy of the calculated distance to the point. Furthermore, when there is one or more short-circuit points in the piping route due to nailing, or when the piping route is branched, the distance calculated from the measured resistance value has no meaning at all. In other words, even if the heat insulating pipe 1 is used, the conventional method can only determine the presence or absence of a short circuit, and is still ineffective in searching for the location of the short circuit.

The present invention makes it possible to search for the location of such a short circuit.

The inventor of the present invention first focused on applying a method for detecting short circuits in electric wires, etc. When a ground fault occurs in a wire, an intermittent current is passed through the wire, and a detector that detects this intermittent current is moved along the wire to detect the point at which the detector no longer detects the intermittent current. This is a method of detecting the ground fault location. However, even when this method was applied to the heat-insulated pipe 1 described above, it had no effect at all.

This is because even though the above method is effective for overhead distribution lines, single-wire wiring, or parallel electric wires, the above-mentioned insulated pipe 1 in which the core pipe 1 and the jacket material 3 are coaxially arranged becomes a coaxial cable, and the core This is thought to be because the magnetic fluxes emitted by the tube 1 and the jacket material 3 cancel each other out. However, if we look at the electrical structure of the conductor-covered heat-insulating pipe 1, we will see that in the case of a coaxial cable, the resistance between the inner conductor and the outer conductor is set to be negligible, whereas the heat-insulating pipe 1 In this case, the resistance of the core tube 2 made of a steel pipe is negligibly small, and on the other hand, the outer jacket material is a complete resistor made of four resistors, and its resistance is Kn/m.

If the capacitance is θ, JgjPF/m, and the insulation resistance between the core tube 2 and the jacket material 4 is ooMn/m or more, and the circuit is a lumped constant circuit, the insulation resistance will be the contact resistance in a nailing accident. If the contact resistance is ignored, the result will be as shown in FIG. 9, which is not a perfect coaxial cable. Therefore, we thought that a leakage electric field and a leakage magnetic field were generated in this insulated pipe 1, and after repeated trial and error to find a method to detect the short circuit using this leakage electric field and leakage magnetic field, we found that the core It has been discovered that when the tube 2 is grounded, the leakage electric field and leakage magnetic field disappear at the short circuit point, and the short circuit point can be detected by detecting this vanishing point by electric field induction and magnetic field induction.

To explain this with reference to FIG. 1, in the insulated pipe 1 where a short circuit accident has occurred at point A, the core pipe 2 is grounded 6, and an audible frequency alternating current 7 is applied across the jacket material 4 and the core pipe 2.
On the other hand, an electric field induction detector 8 having a well-known structure for picking up leakage electric fields, which is wired so as to input its output to a speaker 10 via an amplifier 9, is placed close to the adiabatic tube 1, and the adiabatic tube 1 When I moved it from end B of
The sound volume decreased as it approached the short-circuit point A, and the sound stopped when it passed the short-circuit point. This means that a leakage electric field is generated in the insulation tube 1 from the end B of the insulation tube 1 to the short circuit point A, an electric field induced voltage is generated in the detector 9, and the leakage electric field disappears at the short circuit point A. . This was the same even if the electric field induction detector 8 was replaced with an electromagnetic induction detector to detect the leakage magnetic field linked to the leakage electric field.

Although it is not yet clear why the above-mentioned earth 6 causes such a phenomenon, the present invention will be proven below using experimental data.

○ A conductor-coated insulated pipe 1 with a length of 2 m, in which the core tube 2 is a copper pipe with an outer diameter of /j, /cm, and the jacket material 4 is a carbon-based rubber with an outer diameter of iJ,, r cm. , the conductivity of the core tube 2 is 2j~J%, the resistance of the outer sheathing material 4 is Ω/m%, the capacitance is θ, JdsPF/m, and the relationship between the core tube 2 and the outer sheathing material 4 is An alternating current of 10o■, 10oθH2 is applied to the above-mentioned heat-insulating tube 1 having an insulation resistance of rooMn/m by the method shown in FIG. Figures 2 to 4 are obtained by speeding up the process.
Experimental data as shown in the figure was obtained. When the short-circuit tube N shown in a and b in Fig. 2 is set at the end B of the insulated pipe 1, and when it is set at the position a and b/'i in dam m in Fig. 3, Figures a and l) in Figure 4 show the data when set at 7 m, and each a in Figures 2 to 4 shows the data when the detector 8 is detected from the insulated pipe 1 by /jcmlli. Each of the figures in FIGS. 4 to 4 shows data obtained when the detector 8 was detected at a distance of JOCm. As shown in the graphs of FIGS. 2 to 4, the output voltage of the detector 8 rapidly attenuates when it reaches the short-circuit point and disappears when it almost coincides with the short-circuit point. It has been proven that short circuits can be detected. Similar results were obtained even when an experiment was performed on an actually installed SOm-long insulated pipe.

In the above experiment, the core tube 2 and the outer sheath i4 of the insulated tube 1 were short-circuited by a nail, but even if this nailing caused the core tube
There may be a case where the nail 5 does not cause a short circuit between the nail 5 and the jacket material 4. For example, cracks occur in the jacket material 4 due to the bending process of the insulated pipe 1 during piping, and this crack occurs when a nail 5 is driven into the hole, and the nail 5 pierces the core pipe 2. There is no struggle, and the nail 5 does not come into contact with the jacket material 4, so no short circuit occurs.

However, even at this time, if water leaks from the nailed point of the insulated pipe 1, and the nail 5 and the sheathing material 4 are short-circuited due to water leakage, we thought that the nailed point could be found by the method of the present invention, and so we conducted the following procedure. We conducted an experiment.

In other words, when the core tube 2 and the sheath material 4 are directly short-circuited by the nail 5, the contact resistance at the knee part F'i/θ to □Ω is extremely small. On the other hand, when there is an indirect short circuit due to water leakage, the contact resistance /θ at the knee is approximately Ω to ioKΩ. Therefore, as shown in FIG. 5, a hole 11 is made in the jacket material 4 of the insulated pipe 1, and a nail 5 is driven into the core pipe 2 through the hole 11, and water is replaced between the nail 5 and the jacket material 4. Variable resistor 1
When the detection method of the present invention was attempted by changing the resistance value of the variable resistor 2, the resistance value varied depending on the voltage applied to the core tube 2 and the jacket material 4, but according to experiments, the resistance value was changed by the variable resistor 12. Even if the resistance value is JMΩ to 10MΩ, water leakage occurs due to the above nailing, and this causes the outer covering material 4 to leak.
It has been found that if a short circuit occurs between the core tube 2 and the nail 5 due to water leakage and the nail 5, the nailing point can be detected.

Therefore, at the time of completion inspection after construction of a building, the above-mentioned insulated pipe 1
Since it is customary to perform a water leakage test by applying a pressure of 10 kg/crrz, it is preferable to use the method of the present invention after the water leakage test. Furthermore, when the applied voltage necessary for the detection was varied, sufficient detection could be achieved with a voltage as low as JyV, which is safe for the human body.

Furthermore, in the method of the present invention, the voltage applied to the core tube 2 and the jacket material 4 can be applied to alternating current (including sine waves, other pulse waves, rectangular waves, and triangular waves) and pulsating currents (residual rectified waves, single-wave rectified waves). waves and other pulsating currents, including pulse waves), but
The following differences arise by selectively using this alternating current and pulsating current.

In FIG. 1, when the switch 13 is closed and a sinusoidal AC voltage is applied, a displacement current flows through the capacitance C of the circuit shown at 9 rgJ. , the leakage electric field is detected and the speaker 10 emits a sound regardless of the presence or absence of a short circuit. However, switch 1
3 is opened and a half-wave rectified voltage (
If a rectified wave (or aftereffect rectified wave passed through a bridge circuit) is applied, no current will flow after the capacitor C is charged unless there is a short circuit in the insulated tube 1, and therefore, even if the leakage electric field detector 8 is placed close, the leakage electric field will not be detected. Although it is not detected and speaker 1o does not sound,
When there is a short circuit, current flows and the speaker 10 emits a sound. Therefore, when using pulsating current, it is possible to determine whether there is a short circuit, and it also has the function of the DC resistance method mentioned at the beginning, and only when it is determined that there is a short circuit, can the short circuit be detected. It would be a good idea to do some detection work.

Conversely, when using alternating current as the applied voltage, use the direct current resistance method to determine the presence or absence of a short circuit before applying this alternating voltage.
All you have to do is apply AC voltage only to those with short circuits and detect the short circuits.

In addition, earth 6 includes countervoices that utilize the capacitance with the ground, and these include those that use insulated wires running along the ground, and those that connect conductive wires to aluminum foil of approximately g0Cm x R θam. It is conceivable that the case f of the circuit shown in FIG. 6, which will be described later, is made of metal.

Next, an embodiment of the circuit used in the method of the present invention will be explained with reference to FIGS. 6 and 7. FIG. 6 shows a voltage application device, which includes an oscillation stage 17 including a tuning fork oscillator (trade name: Microfork) 15 and an amplifier 16, which is a dedicated IC for this, and whose oscillation output is manually applied via a variable resistor 18 for adjusting the oscillation output. an output amplifier 19, a transformer 20 for boosting the output of the output amplifier 19 and matching impedance; a changeover switch 13 and a diode 14 shown in FIG. 1; and a constant current resistor 21.
The oscillation output output from the oscillation stage I 17 by the DC power element B is applied to the core tube 2 and the jacket material 4 from the terminals 22 and 23.

Figure 7 shows a short-circuit detection device, with a jack 24 to which the electric field induction detector (moshikake magnetic field induction detector) 8 shown in Figure 1 is connected, and for selective use of the electric field induction detector and the magnetic field induction detector. an impedance matching means 25, a preamplifier 26, an output amplifier 29 which is manually powered through a McTive filter (operator) that amplifies the output of the preamplifier 26, and an output amplifier 29 driven by the output of the output amplifier 29. It has a speaker 30 and a DC ammeter 32 into which the output of the McTave filter 27 is inputted via an amplifier 31. Furthermore, a measuring terminal 33.3 is brought into contact with the core tube 2 and the jacket material 4.
4. A resistance measuring section 37 having an amplifier 35 and an oscillator 36 is configured, and the input terminal of the aforementioned output amplifier 29 is selectively connected to the output terminal 38 of the resistance measuring section 37 and the output terminal 39 of the variable resistor 28. A switch 4o for switching is provided.

In the circuit of FIG. 7, first, the changeover switch 40 is switched to the output terminal 38 of the resistance measurement section 37 as shown by the solid line, and the resistance measurement section 37 is connected to the output amplifier 29, and the measurement terminals 33 and 34 are connected to the test object. A DC power source B is applied to the heat insulated pipe 1 by bringing it into contact with the core pipe 2 and the jacket material 4 of the heat insulated pipe 1. If there is no short circuit, there is no input voltage to the amplifier 35 due to the insulation resistance between the core tube 2 and the jacket material 4, but if there is a short circuit, the voltage corresponding to the resistance up to the short circuit will be applied to the amplifier 3.
5, the oscillator 36 is activated by the amplified output, and the oscillation output is input from the changeover switch 40 to the output amplifier 29.
Therefore, the speaker 30 sounds. Therefore, the presence or absence of a short circuit can be determined based on the presence or absence of sound from the speaker 30.
When the speaker 30 sounds, connect the selector switch 40 to the output terminal 39 of the variable resistor 28 as shown by the broken line.
An oscillation output is applied to the core tube 2 and the jacket material 4 by the voltage application device shown in FIG. 6, and the electric field induction detector (or magnetic field induction detector) 8 is moved along the conductor-coated heat-insulating tube 1.

When this electric field induction detector (magnetic field induction detector) 8 picks up a leakage electric field (or leakage magnetic field), the induced current flows through the preamplifier 26, McTape filter 27, variable resistor 28, and output amplifier 29. Then, it enters the speaker 30 and a sound is emitted, while the strength of the leakage electric field (leakage magnetic field) is displayed by a meter after passing through the amplifier 31 and a DC ammeter 32. When the electric field induction detector (or magnetic field induction detector 8) reaches a short-circuit point and the leakage electric field disappears, the speaker 30 stops sounding, and the DC ammeter 32 indicates around the 0 point. Short circuits can be detected.

Note that the voltage applied to the conductor-coated heat-insulating tube 1 can be a low frequency, a high frequency, a high frequency modulated at an audio frequency, or the like.

As described above, the present invention provides an electric field induction that captures the leakage electric field change of the insulated tube while the core tube of the conductor-covered insulated tube is grounded and a periodic voltage is applied across the jacket material and the core tube. A detector or a magnetic field induction detector that detects changes in the leakage magnetic field is moved along the insulated tube to detect the short circuit from the vanishing point of the leakage electric field and the leakage magnetic field, so the resistance of the conductor-coated insulated tube is This has the advantage of being able to accurately detect short-circuit points without affecting resistance variations in the joints of pipes, and even if there is a short-circuit in one or more places in the pipe due to nailing, the voltage applied end of the insulated pipe can be detected accurately. By moving the detector from the beginning to find the short-circuit points one by one and removing the nail each time, you can detect all the short-circuit points, and even if the pipe line is branched, it can be detected along each branch pipe line. By moving the magnetic field induction detector across the electric field induction detector, a short circuit can be easily detected.

In addition, when the voltage applied to the conductor-coated insulated tube is a pulsating current, if there is no short circuit in the insulated tube, no current will flow after the charging current flows, so an electric field induction detector or magnetic field induction detector Since a leakage electric field or a leakage magnetic field is not spread even if the conductor-coated heat-insulated pipe is brought close, there is an advantage that the presence or absence of a short circuit in the conductor-covered heat-insulated pipe can be determined before detecting the short circuit.

Furthermore, when the voltage applied to the conductor-coated insulated tube is AC, the presence or absence of a short circuit in the insulated tube can be easily detected by determining the presence or absence of a short circuit using the DC resistance method before applying this voltage. Become.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the method of the present invention, Figs. 2 to 4 are graphs showing experimental data, Fig. 5 is a diagram showing the water leakage test method, and Fig. 6 shows an embodiment of the present invention. Figure 7 is a circuit diagram of the voltage application device, Figure 7 is a circuit diagram of the short-circuit detection device, Figure 8 is a cross-sectional view of a conductor-covered heat-insulated pipe to which the present invention is applied, and Figure 9 is a lumped constant of the heat-insulated pipe shown in Figure 8. It is a circuit. 1... Conductor coated heat insulated tube, 2. O. conductive core tube, 3.
...Insulating heat-insulated pipe, 4. Conductive jacket material, 6. Earth, 8. Electric field induction detector or magnetic field induction detector.咄f爲一－－◆桏絨一－－◆Deafness 1 j1力4 １－－◆Himeren 111 佽子籠→vi 经一-ツ淋. -Kaede Ichiro

Claims (1)

[Scope of Claims] 8. In a conductor-coated heat-insulating tube formed by covering the outer periphery of a conductive core tube with a conductive jacket material via an insulating heat-insulating material, the core tube is grounded, and the jacket material and the core An electric field induction detector that applies a periodic voltage across the tube to detect changes in the leakage electric field of the insulated tube, or an arsenic field induction detector that detects changes in the leakage magnetic field.
1. A method for detecting a short circuit in a conductor-coated heat-insulated pipe, the method comprising detecting a short circuit between the jacket material and the core tube using a heat detector. (h) A method for detecting a short circuit in a conductor-coated heat-insulated pipe according to claim 7, wherein the periodic voltage is an alternating current. ! 8. The method of detecting a short circuit in a conductor-coated heat-insulated pipe according to claim 7, wherein the periodic voltage is a pulsating current. Before applying a periodic voltage, a DC voltage is applied across the jacket material and the core tube of the conductor-coated insulated pipe, and the presence of a short circuit between the jacket material and the core tube is determined based on the DC resistance. A method for detecting a short circuit in a conductor-coated heat-insulated pipe according to claim 1, which includes a direct current resistance method.