JP4398198B2 - Insulation degradation region diagnosis system and method for electric wire or cable - Google Patents

Description

  The present invention relates to a system and method for diagnosing insulation deterioration of an electric wire or cable that conducts electricity, and more particularly, to a system and method suitable for specifying a region where insulation deterioration of an electric wire or cable has occurred.

An electric wire or cable for power transmission may be deteriorated in insulation due to a temporal change of an insulator or a bad environment. In order to prevent such an accident due to insulation deterioration, various methods have been conventionally used to determine insulation deterioration of electric wires and cables. For example, in the methods disclosed in Patent Documents 1 and 2, an AC voltage is supplied to an electric wire or cable, a leakage current to the ground is measured, and insulation deterioration is determined based on the leakage current. In addition, as a method for determining insulation deterioration of electric wires and cables, there are a method using an insulation megar, a residual charge measurement method, and the like.
Japanese Patent No. 3034651 Japanese Patent Laid-Open No. 06-186275

  By the way, in order to reduce the repair cost of electric wires and cables, it is desirable to repair only the portion where the insulation deterioration of the electric wires or cables has occurred. For that purpose, it is necessary to specify at which point or in which region the insulation deterioration has occurred in one electric wire or cable. However, any of the conventional insulation deterioration determination methods described above diagnoses deterioration of a single electric wire or the entire cable, and it is impossible to specify a location where insulation deterioration has occurred. In addition, although there is a fault locator as an accident point detection device for long-distance transmission lines, it is difficult to apply to electric wires and cables of several hundred meters or less.

  As described above, conventionally, there has been no method for identifying an insulation deterioration region of an electric wire or cable of several hundred meters or less, and when it is determined that insulation deterioration has occurred, the entire electric wire or cable must be replaced. A large amount of money was necessary.

  The present invention has been made to solve such a problem, and an object thereof is to be able to specify a region where insulation deterioration of an electric wire or cable that conducts electricity has occurred.

In order to achieve the above object, the invention described in claim 1
A system for diagnosing an insulation deterioration area of an electric wire or cable that conducts electricity,
A single-phase AC voltage source provided between the conductor of the electric wire or cable in a power failure state and the ground, and
An AC ground fault current converter having a resistor for grounding the AC current supply source, and a voltage detector for detecting a voltage generated in the resistor;
A current transformer for detecting leakage current of the electric wire or cable, a phase determination unit for obtaining a phase difference between the detected current signal and a voltage signal detected by the AC ground fault current converter, and the obtained A resistance leakage current determination unit that obtains a resistance leakage current based on the phase difference and the detected current signal, and the electric wire or cable based on the obtained resistance leakage current and the supply voltage of the AC voltage supply source. An insulation resistance measuring instrument having a resistance determination unit for measuring insulation resistance;
A correlation determination unit for obtaining a correlation between an insulation resistance value measured by the insulation resistance measuring instrument at a plurality of points of the electric wire or cable and a position along the length direction of the electric wire or cable at each measurement point; ,
When there is a region where the gradient in the calculated correlation exceeds a predetermined value, an insulation deterioration determination unit that determines the region as an insulation deterioration region;
Characterized by comprising

Further, the invention described in claim 2, wherein the insulation resistance in the insulation deterioration region diagnosis system of the electric wire or cable according to claim 1, a voltage signal detected by the AC ground fault current converter, a wired or wireless The phase determination unit of the insulation resistance measurement device obtains the phase difference based on the transmitted voltage signal.

Further, the invention described in claim 3 is the periodic signal in which both the insulation resistance measuring instrument and the AC ground fault current converter are synchronized with each other in the insulation deterioration region diagnosis system for the electric wire or cable according to claim 1. And the phase detection unit of the insulation resistance measuring device obtains the phase difference based on the periodic signal.

The invention described in claim 4 is a method for diagnosing an insulation deterioration region of an electric wire or cable that conducts electricity,
AC voltage is supplied by a single-phase AC power supply source between the conductor of the wire or cable in a power failure state and the ground,
The AC current supply source is grounded by a resistor, and a voltage generated in the resistor is detected by a voltage detector,
Detect the leakage current of the wire or cable with a current transformer,
Obtaining a phase difference between the detected leakage current and the detected voltage signal;
A resistance leakage current is obtained based on the obtained phase difference and the detected current signal,
Measure the insulation resistance value of the wire or cable based on the obtained resistance leakage current and the supply voltage of the AC voltage supply source,
Obtaining the correlation between the insulation resistance value measured by the insulation resistance measuring instrument at a plurality of points of the wire or cable and the position along the length direction of the wire or cable at each measurement point,
When there is a region where the gradient in the obtained correlation exceeds a predetermined value, the region is determined as an insulation deterioration region.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to specify the area | region where the insulation deterioration of the electric wire or cable which conducts electricity has arisen.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. In the accompanying drawings, FIG. 1 is an overall system configuration diagram showing a first embodiment of the present invention, and FIG. 2 is a diagram showing an example of a correlation between a cable length (resistance measurement point) and an insulation resistance value.

  First, the outline of the cable insulation deterioration diagnosis in the first embodiment of the present invention will be described. In the present embodiment, as a diagnosis of the insulation deterioration region of the cable 2 for power transmission, the power supply terminal and the load terminal of the cable 2 are disconnected, the cable 2 is brought into a power failure state, and then the charge is obtained by grounding the conductor of the cable 2 Keep fully discharged. Thereafter, as shown in FIG. 1, the AC power supply device 1 as the voltage supply source of the present invention is connected to one end of the conductor of the cable 2, and the clamp type current transformer 13 and the portable type are utilized using a manhole or the like. The resistance leakage current Ir of the cable 2 is measured by the AC circuit ground fault detector 4 and the insulation resistance value is measured from the current value.

  When the cable is not deteriorated in insulation, the insulation resistance measurement value R changes with a substantially uniform gradient with respect to the cable length (cable length from the voltage supply point) as shown by a broken line in FIG. On the other hand, when insulation deterioration occurs locally, as shown by the solid line in FIG. 2, the gradient of the insulation resistance value in the region including the insulation deterioration location (region A of cable A and region II of cable B in the figure). Becomes larger. The reason for this is that, as schematically shown in FIG. 3, the resistance leakage current Ir measured at the measurement point Q where the cable length from the voltage supply point P is L is from the measurement point Q to the other end R of the cable 2. This is because the total resistance of the current flowing from the cable 2 to the ground in the range of ## EQU2 ## and the measured insulation resistance value R represents the overall insulation resistance between the QRs of the cable 2. For example, when the insulation deterioration occurs between the point B and the point C as in the cable A of FIG. 2, the influence of the insulation deterioration does not appear in the insulation resistance value measured at the point C. The measured value of the insulation resistance decreases by the amount of insulation deterioration between BCs (that is, the decrease of the insulation resistance value), so that the gradient increases between BCs (region I).

  Therefore, in this embodiment, the insulation resistance value of the cable 2 is measured at a plurality of points at appropriate intervals, the correlation between the measurement point and the insulation resistance measurement value is obtained, and the insulation deterioration region is determined from the change in the gradient. Judgment is made.

  In the first embodiment of the present invention, a single-phase AC power supply device 1 is used as a current supply source, and the supply voltage V from the AC power supply device 1 to the cable 2 is measured by the AC ground fault current converter 3. By detecting the phase difference θ between the voltage signal thus measured and the leakage current I, the resistance leakage current Ir is obtained, and the insulation resistance R is detected by dividing the supply voltage V by the resistance leakage current Ir.

That is, as shown in FIG. 4, the leakage current I can be decomposed into a resistance leakage current Ir and a capacitance leakage current Ic, and the phase of the resistance leakage current Ir and the supply voltage V coincide with each other. Therefore, using the phase difference θ between the leakage current I and the supply voltage V,
Ir = I · cos θ
Thus, the resistance leakage current Ir is obtained. Then, using this resistance leakage current Ir, R = V / Ir
Thus, the insulation resistance value R is obtained.

  In this embodiment, the cable 2 installed on the ground or the seabed is described as being diagnosed for the insulation degradation region. However, the insulation degradation region is also exactly the same for the wires installed on the ground or in the air. Can be diagnosed.

  Hereinafter, the cable insulation deterioration region diagnosis system of the present embodiment will be described in more detail.

  As shown in FIG. 1, the AC power supply device 1 is grounded via an AC ground fault current converter 3. As described above, after the cable 2 is in a power failure state in advance and the conductor of the cable 2 is grounded to completely discharge the electric charge, the AC power supply device 1 and the AC ground fault current converter 3 are connected. And

  The AC ground fault current converter 3 detects a variable resistor 31, an ammeter 32 that detects and displays the current flowing through the variable resistor 31, and detects a voltage at both ends of the variable resistor 31 and responds to the detected voltage. And a voltage detector 33 for outputting the received signal. The operator can adjust the ground fault current flowing from the AC power supply device 1 by operating the variable resistor 31 based on the display of the ammeter 32. Further, the detection signal from the voltage detector 33 represents the supply voltage V of the AC power supply device 1.

  The cable 2 is provided with a clamp type current transformer 13. The clamp type current transformer 13 is connected to an AC electric circuit ground fault detector 4 as an insulation resistance measuring device of the present invention, detects a leakage current I flowing from the cable 2 to the ground side, and detects this AC electric circuit ground. Supply to the tangential point detector 4. The AC circuit ground fault detector 4 is connected to the AC ground fault current converter 3 by wire or wirelessly, and the detection signal of the supply voltage V detected by the AC ground fault current converter 3 is detected as an AC circuit ground fault point. Is supplied to the container 4.

  The AC circuit ground fault detector 4 includes a signal amplifier 41, a noise filter 42, a phase analyzer 43, a resistance measurement unit 44, a resistance display unit 45, and the like. The signal amplifier 41 amplifies the leakage current I from the clamp type current transformer 13, and the noise filter 42 removes noise components other than the frequency of the power supply V of the AC power supply device 1. The phase analyzer 43 detects the phase difference θ between the leakage current I from which the noise component has been removed and the voltage signal V supplied from the AC ground fault current converter 3, and the resistance measurement unit 44 is described above. Thus, using the phase difference θ, the resistance leakage current Ir is obtained from the leakage current I by Ir = I · cos θ, and further, the insulation resistance value R is obtained by R = V / Ir. The insulation resistance value R thus measured is displayed on the resistance display section 45. Preferably, as the measurement accuracy of the insulation resistance value R, for example, it is desirable that an insulation resistance with a capacitance of 1 μF or more and 100 KΩ or more can be measured.

  In the above description, the detection signal of the supply voltage V detected by the AC ground fault current converter 3 is supplied to the AC electric circuit ground fault detector 4 by wire or wirelessly. In consideration of easy carrying of the device, the AC circuit ground fault point detector 4 and the AC ground fault current converter 3 are each provided with a time generator that generates periodic clock signals that are accurately synchronized with each other. Thus, the AC circuit ground fault detector 4 can detect the phase difference θ based on the clock signal without connecting the AC ground fault current converter 3 and the AC circuit ground fault detector 4. Good. However, since there is an error in the cycle of the clock signal generated by the time generator, it is necessary to correct the error every few hours, for example. For a technique for generating two periodic signals synchronized with each other, see, for example, Japanese Patent Laid-Open No. 5-273291.

  As shown in FIG. 1, a transmission device 5 such as a mobile phone is connected to the AC electric circuit ground fault point detector 4, and the insulation resistance value R measured by the AC electric circuit ground fault point detector 4 and the measurement Cable specifying information for specifying the target cable 2 and measurement point specifying information for specifying the measurement point of the cable 2 are transmitted to the receiving device 6 on the server 12 side. Here, as the insulation resistance value R, the measurement operator may manually input the resistance value displayed on the resistance display unit 45, or the measurement value may be directly transmitted. Further, for example, a measurement operator can input a manhole number or the like as the measurement point specifying information. In addition to the insulation resistance value R, the leakage current I, the resistance leakage current Ir, the capacitance leakage current Ic, and the supply voltage V may be transmitted to the server 12 and used for data management.

  The server 12 includes a correlation determination unit 121, and by the correlation determination unit 121, a measurement point of the insulation resistance value R (specifically, a cable from an end portion on the side where a voltage is supplied from the AC power supply device 1 2) and a measured value of insulation resistance are created and displayed as a graph as shown in FIG. 2, or information representing the correlation is recorded in the database 7. For example, when a manhole number is used as the measurement point specifying information, a table indicating the relationship between the manhole number and the measurement cable length is held on the server 12 for each cable, and the measurement point is referred to by referring to this table. The cable length is to be determined.

  The insulation resistance value of the cable is affected by temperature, humidity, electric wire, cable material, model, and the like. Therefore, in the present embodiment, the data of the insulation resistance value under various conditions for various cables are stored in the database 7 and the data analysis unit 122 is provided in the server 12, and the data analysis unit 122 performs mathematical processing such as data mining. By performing the clustering based on the above and correcting the measurement value of the insulation resistance according to the air temperature, the temperature, etc., the specific accuracy of the insulation deterioration region can be improved.

  In the present embodiment, the transmission device 9 is provided in the server 12 and information representing the correlation created by the correlation determination unit 121 is transmitted to the reception device 10 on the manager 11 side. Then, the manager 11 observes the displayed graph by displaying the correlation in the receiving apparatus 10 as shown in FIG. 2, for example, and the section I of the cable A and the cable B in FIG. It can be determined that the insulation deterioration has occurred in the section where the gradient is large as in section II. In the present embodiment, by transmitting data from the server 12 to the receiving device 10 on the manager 11 side, the manager 11 can quickly determine the insulation degradation area of the cable 2. Therefore, for example, the manager 11 can instruct the worker to measure the area in which the insulation degradation has occurred immediately more finely, and can specify the location where the insulation degradation has occurred more accurately. In addition, it is possible to promptly give mutual judgment between the operator and the manager, such as being able to issue an instruction for cable replacement work immediately.

  In the above description, the correlation determination unit 121 of the server 12 creates a correlation between the resistance measurement point and the insulation resistance value R, and a person determines the location where the insulation deterioration has occurred from this correlation. However, the present invention is not limited to this, and the correlation determination unit 121 may automatically determine the location where the insulation deterioration has occurred from the degree of change in the correlation gradient. In this case, when the insulation deterioration is determined, an alarm signal indicating the region is transmitted from the transmission device 9 to the reception device 10 so that the administrator can be notified of the insulation deterioration occurrence region more quickly. it can.

  In the above description, the portable AC circuit ground fault detector 4 is carried by an operator and the insulation resistance at each point of the cable is measured using a manhole or the like. Alternatively, a plurality of AC electric circuit ground fault detectors 4 may be provided permanently so that the location where the insulation deterioration occurs can be specified based on the insulation resistance values detected by the plurality of AC electric circuit ground fault detectors 4. This configuration is suitable when, for example, a daily measurement operation is difficult like a submarine cable. In addition, if there is a region where insulation degradation is expected in the near future, an AC circuit ground fault detector 4 is permanently installed at a point across the region so that the occurrence of insulation degradation can be determined at all times. Also good. When the current transformer is permanently installed from the time of the new installation of the cable, not only the clamp type but also other types of current transformers can be used.

Next, a second embodiment of the present invention will be described.
FIG. 5 is an overall configuration diagram showing a second embodiment of the present invention. In FIG. 5, the same components as those in FIG. 1 of the first embodiment are denoted by the same reference numerals. As shown in FIG. 5, in this embodiment, a DC power supply device 100 is provided instead of the AC power supply device 1 of the first embodiment, and a clamp type DC current transformer 130 is provided instead of the clamp type current transformer 13. In place of the AC circuit ground fault detector 4, a DC circuit ground fault detector 400 is provided. Moreover, the positive electrode of the DC power supply device 100 is connected to the conductor of the cable 2, and the negative electrode is directly connected to the ground. Also in this embodiment, prior to diagnosis of the cable 2, the DC power supply 100 is connected to the cable 2 after the cable 2 is in a power failure state and the electric charge of the cable 2 is completely discharged.

  The clamp type DC current transformer 130 is a current transformer having a function of detecting a DC resistance leakage current Id of the cable 2. Therefore, in this embodiment, it is not necessary to obtain the phase difference from the supply voltage V when measuring the insulation resistance value R, and the resistance measurement unit 404 of the DC circuit ground fault detector 400 has the relationship of R = V / Id. Using the equation, the insulation resistance value R can be measured directly from the leakage current Id. As measurement accuracy of the insulation resistance value R, for example, it is preferable that an insulation resistance of 100 KΩ or more can be measured. Note that the configurations and functions of the transmission device 5, the server 12, the transmission device 9, and the reception device 10 are the same as those in the first embodiment, and a description thereof will be omitted.

  As described above, in the second embodiment of the present invention, it is not necessary to obtain the phase difference from the supply voltage V by detecting the leakage current using the clamp type DC current transformer 130. Can be easy.

1 is an overall configuration diagram showing a first embodiment of the present invention. It is a figure which shows an example of correlation with a cable length and an insulation resistance value. It is a schematic diagram for demonstrating the relationship between the leakage current measurement position of a cable, and an insulation resistance measured value. It is a figure which shows the relationship between the leakage current I, the resistance leakage current Ir, and the electrostatic capacitance leakage current Ic. It is a whole block diagram which shows the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply device 2 Cable 3 AC ground fault current converter 4,400 AC electric circuit ground fault point detector 43 Phase analysis part 44,405 Resistance measurement part 5,9 Transmitter 6,10 Receiver 7 Recording database 11 Manager 12 Server 121 Correlation determination unit 122 Data analysis unit 100 DC power supply device 13 Clamp type current transformer 130 Clamp type DC current transformer

Claims (4)

A system for diagnosing an insulation deterioration area of an electric wire or cable that conducts electricity,
A single-phase AC voltage source provided between the conductor of the electric wire or cable in a power failure state and the ground, and
An AC ground fault current converter having a resistor for grounding the AC current supply source, and a voltage detector for detecting a voltage generated in the resistor;
A current transformer for detecting leakage current of the electric wire or cable, a phase determination unit for obtaining a phase difference between the detected current signal and a voltage signal detected by the AC ground fault current converter, and the obtained A resistance leakage current determination unit that obtains a resistance leakage current based on the phase difference and the detected current signal, and the electric wire or cable based on the obtained resistance leakage current and the supply voltage of the AC voltage supply source. An insulation resistance measuring instrument having a resistance determination unit for measuring insulation resistance;
A correlation determination unit for obtaining a correlation between an insulation resistance value measured by the insulation resistance measuring instrument at a plurality of points of the electric wire or cable and a position along the length direction of the electric wire or cable at each measurement point; ,
When there is a region where the gradient in the calculated correlation exceeds a predetermined value, an insulation deterioration determination unit that determines the region as an insulation deterioration region;
An insulation deterioration region diagnosis system for an electric wire or a cable, comprising: The voltage signal detected by the AC ground fault current converter is transmitted to the insulation resistance measuring device by wire or wirelessly, and the phase determination unit of the insulation resistance measuring device is based on the transmitted voltage signal. wire or cable insulation degradation region diagnosis system according to claim 1, wherein the determining the phase difference. Both the insulation resistance measuring instrument and the AC ground fault current converter have a periodic signal generating means synchronized with each other, and the phase detection unit of the insulation resistance measuring instrument is configured to output the phase difference based on the periodic signal. The insulation deterioration region diagnosis system for an electric wire or cable according to claim 1, wherein: A method for diagnosing an insulation deterioration region of an electric wire or cable that conducts electricity,
AC voltage is supplied by a single-phase AC power supply source between the conductor of the wire or cable in a power failure state and the ground,
The AC current supply source is grounded by a resistor, and a voltage generated in the resistor is detected by a voltage detector,
Detect the leakage current of the wire or cable with a current transformer,
Obtaining a phase difference between the detected leakage current and the detected voltage signal;
A resistance leakage current is obtained based on the obtained phase difference and the detected current signal,
Measure the insulation resistance value of the wire or cable based on the obtained resistance leakage current and the supply voltage of the AC voltage supply source,
Obtaining the correlation between the insulation resistance value measured by the insulation resistance measuring instrument at a plurality of points of the wire or cable and the position along the length direction of the wire or cable at each measurement point,
An insulation degradation region diagnosis method for an electric wire or a cable, wherein when there is a region where the gradient in the obtained correlation exceeds a predetermined value, the region is determined as an insulation degradation region.

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