JPH11153640A - Detection method for partial discharge of power cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve detection accuracy of partial discharge, by arranging a pair of foil electrode on external sheath of power cable having a copper tape shield layer, arranging a high frequency iron-core between electrodes, and increasing the impedance of the shield. SOLUTION: When partial discharge occurs in an insulator 2 between a high voltage conductor 1 of CV cable 10 and an external semiconducting layer 3, reciprocal current based on the partial discharge flows between the conductor 1 and a copper tape shield layer 4. This current flows as sheath current along the shield layer 4, and the shield layer 4 has an increased impedance by a high frequency iron-core 7, and by this, the electric potential difference induced between both ends of a detection impedance 8 increases. When the shield layer 4 is normal, the sheath current flows in the longitudinal direction of the cable 10. When looseness and play exists in the shield layer, contact resistance increases and the sheath current spirally flows in the circumferential direction of the cable 10. In this case, the electric potential caused between the both ends of the detection impedance 8 gradually becomes large and the detection accuracy of the partial discharge is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of detecting a partial discharge of a power cable, and more particularly to a method of detecting a partial discharge occurring in a power cable line having a shield layer formed by spirally winding a copper wire, a copper tape or the like. About.

[0002]

2. Description of the Related Art Conventionally, a method for detecting partial discharge of a power cable having a spirally wound metal sheath is disclosed in, for example, Japanese Patent Publication No. 6-8847. In this partial discharge detection method, a detection coil is provided outside a wire-shielded power cable, and a high-frequency iron core is arranged outside the detection coil to increase the impedance of the detection coil. Based on this, the potential difference generated at both ends of the detection impedance is increased.

As another method for detecting partial discharge of a power cable having a spirally wound metal sheath, Japanese Patent Laid-Open No.
There is one disclosed in JP-A-49365. This partial discharge detection method has a pair of foil electrodes arranged at a predetermined interval in a length direction of a power cable, a detection impedance is connected between the pair of foil electrodes, and a potential difference generated at both ends of the detection impedance. Is measured to measure the partial discharge of the power cable.

[0004]

However, according to the conventional partial discharge detection method, a spirally wound wire shield,
Since the impedance between two points of a metal sheath such as a tape shield is very low, the potential difference between the pair of foil electrodes is small even if an induced current based on partial discharge flows therethrough. There is a problem that high partial discharge measurement cannot be performed. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for detecting a partial discharge of a power cable in which the potential difference between a pair of foil electrodes generated based on the partial discharge is increased to improve the detection accuracy of the partial discharge.

[0005]

According to the present invention, in order to achieve the above object, a shield layer is formed by spirally winding a metal tape or a metal wire around an outer periphery of a power cable core, and an outer sheath is formed around the outer periphery thereof. In the method for detecting partial discharge of a power cable that has been applied, a pair of foil electrodes electrostatically coupled to the shield layer are arranged at two points on the outer periphery of the outer sheath at a predetermined distance. A high-frequency core for increasing the inductance of the shield layer is arranged between the two points on the outer periphery of the outer sheath, and a detection impedance of a predetermined value is connected between the pair of foil electrodes, and both sides of the detection impedance are connected. And a method for detecting a partial discharge of a power cable, which detects the partial discharge based on a potential difference of the power cable.

In the above-described partial discharge detection method, the pair of foil electrodes are connected to a calibration pulse generator that injects a calibration pulse in parallel with the detection impedance, and detects a spectrum based on the injected calibration pulse. May be.

In order to achieve the above object, the present invention provides a power cable in which a metal tape or a metal wire is spirally wound around an outer periphery of a power cable core to form a shield layer, and an outer sheath is provided on the outer periphery. In the method for detecting a partial discharge of a power cable for detecting a partial discharge, a pair of foil electrodes for signal detection electrostatically coupled to the shield layer are arranged at two points on the outer periphery of the outer sheath at a predetermined distance. A high-frequency iron core for increasing the inductance of the shield layer is disposed between the two points on the outer periphery of the outer sheath, and a pair of foil electrodes for detecting a calibration pulse electrostatically coupled to the shield layer is connected to the outer sheath. Are arranged at two points separated by a predetermined distance on the outer periphery of the sensor, a detection impedance of a predetermined value is connected between the pair of foil electrodes for signal detection, and the detection pulse for the calibration pulse detection is connected. A method for detecting a partial discharge of a power cable is provided, in which a calibration pulse is injected from a pair of foil electrodes to calibrate a measuring device for detecting a partial discharge, and the measuring device detects the partial discharge based on a potential difference on both sides of a detection impedance. I do.

In the above-described partial discharge detection method, the pair of foil electrodes for injecting the calibration pulse may be provided close to the pair of foil electrodes for signal detection, and the pair of foil electrodes for signal detection may be provided. May be provided at a predetermined interval.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1A shows a partial discharge detection device for a power cable according to a first embodiment of the present invention.
The CV cable 10 to be measured for partial discharge includes a high-voltage conductor 1 (an internal semiconductive layer is not shown), an insulating layer 2 provided outside the high-voltage conductor 1, and an external semiconductive layer provided outside the insulating layer 2. A layer 3 and a copper tape shielding layer 4 provided by spirally winding a copper tape outside the outer semiconductive layer 3
And a pair of metal foil electrodes 6A and 6B arranged at a predetermined interval along the CV cable 10 on the outside of the corrosion-resistant vinyl sheath 5 provided outside the copper tape shielding layer 4. And three high-frequency iron cores 7 arranged between the metal foil electrodes 6A and 6B. The pair of metal foil electrodes 6A and 6B are connected to a detection impedance 8, and a calibration pulse oscillator 9 is connected in parallel to both ends of the detection impedance 8. Detection impedance 8
Are not shown in the figure.

FIG. 1B shows a cross section taken along the line AA 'in FIG. 1A. The high-frequency core 7 is constituted by a pair of core pieces 7A and 7B divided in the circumferential direction of the CV cable 10. Have been.

FIG. 2 is a circuit diagram showing the partial discharge detecting device shown in FIG. Here, the coil L corresponds to the copper tape shielding layer 4 in which the induced current of the partial discharge generated in the CV cable 10 flows spirally, and a pair of a capacitor 50 formed at this predetermined position via the anticorrosion vinyl sheath 5 is provided. Metal foil electrode 6
A and 6B are electrostatically coupled. The metal foil electrodes 6A, 6
By arranging the high-frequency core 7 between B, the impedance of the copper tape shielding layer 4 in this section is increased.

In the above configuration, the CV cable 10
When partial discharge occurs in the insulator 2 between the high-voltage conductor 1 and the external semiconductive layer 3, a reciprocating current based on the partial discharge flows between the high-voltage conductor 1 and the copper tape shielding layer 4. This reciprocating current flows as a sheath current along the copper tape shielding layer 4,
The impedance of the copper tape shielding layer 4 is increased by the high-frequency iron core 7, thereby increasing the potential difference generated between both ends of the detection impedance 8. This potential difference is measured by a measuring device (not shown).

When the copper tape shielding layer 4 is in a normal state, the sheath current flows in the length direction of the CV cable 10, but the copper tape shielding layer 4 becomes loose or rattle due to thermal expansion and contraction of the CV cable 10. In this case, the contact resistance between adjacent turns of the copper tape increases, and the sheath current spirally flows in the circumferential direction of the CV cable 10. In this case, the voltage drop in the length direction of the copper tape shielding layer 4 becomes larger, and the potential difference generated at both ends of the detection impedance 8 becomes further larger, so that the detection accuracy of the partial discharge is improved.

As shown in FIG. 2, in the present invention, the high-frequency iron core 7 is arranged in the detection section of the partial discharge formed by the pair of metal foil electrodes 6A and 6B, so that the coil L by the copper tape shielding layer 4 is formed. Has a large inductance.

Further, in the above configuration, the CV is supplied from the calibration pulse generator 9 via the pair of metal foil electrodes 6A and 6B.
If a calibration pulse is injected into the cable 10, it can be used as a reference signal when determining the configuration of measurement sensitivity and the frequency characteristics of a high-frequency pulse when a partial discharge occurs. in this case,
By injecting the calibration pulse through the copper tape shielding layer 4 having the increased impedance, the injection efficiency of the calibration pulse is improved.

FIG. 3 shows a device for detecting partial discharge of a power cable according to a second embodiment of the present invention, in which metal foil electrodes 6A and 6B for signal detection and a corrosion-resistant vinyl sheath between the metal foil electrodes 6A and 6B are provided. 5 and a detection impedance 8 connected to the metal foil electrodes 6A and 6B.
And metal pulse electrodes 6C and 6D for signal injection, and a calibration pulse oscillator 9 connected to the metal foil electrodes 6C and 6D.

If the injection of the calibration pulse is performed separately from the detection of the partial discharge based on the above-described configuration and the injection of the calibration pulse is performed, the sensitivity calibration of the partial discharge detection can be performed at any position of the CV cable 10, for example, the partial discharge detection. This can be performed while the position and the calibration pulse injection position are brought close to or far from each other, and a frequency with a high S / N ratio can be selected simultaneously with the calibration of a measuring instrument (not shown).

In this embodiment, detection of partial discharge of a CV cable having a copper tape shielding layer as a power cable has been described. For example, the same effect can be obtained for detection of partial discharge of a power cable in which a wire shield or the like is spirally wound. Can be played.

[0019]

As described above, according to the method for detecting partial discharge of a power cable of the present invention, a pair of foil electrodes are arranged on an outer sheath of a power cable having a copper tape shielding layer,
Since a high-frequency iron core is placed between the foil electrodes to increase the impedance of the copper tape or the copper wire shielding layer, the potential difference between a pair of foil electrodes generated in accordance with the partial discharge is increased to increase the detection accuracy of the partial discharge. Can be.

[Brief description of the drawings]

FIG. 1A is an explanatory view showing a partial discharge detection device according to a first embodiment of the present invention. (b) A sectional view taken along the line AA 'of (a).

FIG. 2 is an explanatory diagram showing the circuit of FIG. 1;

FIG. 3 is an explanatory diagram showing a partial discharge detection device according to a second embodiment of the present invention.

[Explanation of symbols]

 1, high-voltage conductor 2, insulating layer 3, external semiconductive layer 4, copper tape shielding layer 5, corrosion-resistant vinyl sheath 6A, metal foil electrode 6B, metal foil electrode 6C, metal foil electrode 6D, metal foil electrode 7, high-frequency iron core 7A, Iron core piece 7B, iron core piece 8, detection impedance 9, calibration pulse oscillator 50, capacitor

Claims (5)

[Claims] 1. A partial discharge of a power cable for detecting a partial discharge of a power cable in which a shield layer is formed by spirally winding a metal tape or a metal wire around an outer periphery of a power cable core and an outer sheath is provided on the outer periphery thereof. In the detection method, a pair of foil electrodes that are electrostatically coupled to the shield layer are arranged at two points on the outer periphery of the outer sheath at a predetermined distance, and a high-frequency iron core that increases inductance of the shield layer is connected to the outside. It is arranged between the two points on the outer periphery of the sheath, a detection impedance of a predetermined value is connected between the pair of foil electrodes, and the partial discharge is detected based on a potential difference on both sides of the detection impedance. To detect partial discharge of power cables. 2. The pair of foil electrodes are connected to a calibration pulse generator that injects a calibration pulse in parallel with the detection impedance, and detects a spectrum based on the injected calibration pulse. Power cable partial discharge detection method. 3. A partial discharge of a power cable for detecting a partial discharge of a power cable in which a metal tape or a metal wire is spirally wound around an outer periphery of a power cable core to form a shield layer and an outer sheath is provided on the outer periphery thereof. In the detection method, a pair of foil electrodes for signal detection, which are electrostatically coupled to the shield layer, are separated from each other by a predetermined distance on the outer periphery of the outer sheath.
A pair of foil electrodes for calibrating pulse injection that are arranged at a point, and a high-frequency iron core that increases the inductance of the shield layer is arranged between the two points on the outer periphery of the outer sheath, and that is electrostatically coupled to the shield layer. A pair of foil electrodes for injecting the calibration pulse are arranged at two points on the outer periphery of the outer sheath separated by a predetermined distance, and a detection impedance of a predetermined value is connected between the pair of foil electrodes for signal detection. A method for detecting a partial discharge of a power cable, comprising: calibrating a measuring device for detecting a partial discharge by injecting a calibration pulse from the measuring device; . 4. The method of detecting a partial discharge of a power cable according to claim 3, wherein the pair of foil electrodes for injecting the calibration pulse is provided near the pair of foil electrodes for signal detection. 5. The partial discharge of a power cable according to claim 3, wherein the pair of foil electrodes for injecting the calibration pulse is provided at a predetermined interval from the pair of foil electrodes for signal detection. Detection method.