JP3107361B2 - Partial discharge detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a partial discharge, and more particularly to a method for measuring a partial discharge in which the detection sensitivity of a partial discharge generated at a normal connection portion is improved.

[0002]

2. Description of the Related Art As a conventional partial discharge measuring method, for example, there is one shown in FIG.

In this measurement method, a foil electrode detection method is applied. As shown in FIG. 6, a pair of metal foil electrodes 4 are provided on both sides of an anticorrosion vinyl layer 6 of an insulated connecting portion 2 via an insulating cylinder 3.
And a detection impedance 5 is connected between the pair of metal foil electrodes 4 to measure a partial discharge. That is, when a partial discharge occurs in the insulating layer portion of the cable 1 or the connecting portion (the adjacent connecting portion including the insulating connecting portion 2), a partial discharge pulse is induced between the sheaths on both sides of the insulating cylinder 3 of the insulating connecting portion 2. The partial discharge is measured by detecting the potential difference between the two sides of the insulating cylinder 3 through the capacitance of the pair of metal foil electrodes 4.

[0004]

However, according to the conventional partial discharge measuring method, the partial discharge cannot be measured because the connecting portion usually does not have a rim in the sheath. Therefore, if an attempt is made to detect a partial discharge of a normal connection at an adjacent insulated connection, the partial discharge pulse will be attenuated while the partial discharge pulse of the normal connection is propagated to the insulated connection. There is an inconvenience that the detection sensitivity is reduced by one digit as compared with the detection of the generated partial discharge.

Accordingly, it is an object of the present invention to provide a partial discharge measuring method capable of improving the detection sensitivity of a partial discharge generated at a connection part.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, the present invention forms a metal shielding layer at least on the outer periphery of an external semiconductive layer in order to improve the detection sensitivity of a partial discharge generated at a normal connection portion. The present invention provides a method for measuring a partial discharge in which a normal connection portion is formed and a partial discharge signal is extracted through a metal shielding layer of the normal connection portion.

That is, according to a first partial discharge measurement method of the present invention, an outer semiconductive layer and a metal shielding layer which are cut off via an insulator are formed on the outer periphery of a conductor connection portion of a power cable,
A copper tube separated by an insulating tube is placed around the outer semiconductive layer and metal shield layer, and the copper tube is connected with a jumper wire to form a normal connection. Attach an iron core, set the high-frequency impedance of the jumper wire to a predetermined value, attach a pair of metal foil electrodes on both sides of the insulating cylinder on the corrosion-resistant vinyl layer of the copper body tube, and connect the detection impedance to the pair of metal foil electrodes. And extracting a partial discharge signal based on a potential difference generated in the detected impedance.

According to a second partial discharge measuring method of the present invention, an insulator and a pair of metal shielding layers cut off at the center are formed on the outer periphery of a conductor connecting portion of a power cable via an external semiconductive layer. A copper tube separated by an insulating tube is placed around the outer periphery of a pair of metal shielding layers, and the copper tube is connected with a jumper wire to form a normal connection, and a high-frequency iron core is attached to the jumper wire as necessary Then, set the high-frequency impedance of the jumper wire to a predetermined value, attach a pair of metal foil electrodes on both sides of the insulating cylinder on the corrosion-resistant vinyl layer of the copper tube, connect the detection impedance to the pair of metal foil electrodes, The partial discharge signal is extracted based on the potential difference generated in the above.

[0009]

[0010]

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS When a partial discharge occurs in an insulating layer portion of a normal connection portion, a partial discharge pulse is induced to a pair of measurement electrodes having a predetermined high-frequency impedance therebetween, and is connected to the pair of measurement electrodes. A potential difference is generated at both ends of the detected impedance, and a partial discharge signal corresponding to the potential difference is output from the detected impedance.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A partial discharge measuring method according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows a method of measuring a partial discharge according to an embodiment of the present invention, in which a partial discharge generated at a normal connection portion is measured. This normal connection comprises a connection sleeve 8 for connecting the conductor 7 of the power cable, an extruded reinforcing insulation 10 provided around the connection sleeve 8 following the insulator 9 of the power cable, and an outer semiconductive An outer semiconductive layer 12 having an edge 12A provided on the outer periphery of the extrusion reinforcing insulating portion 10 following the layer 11, and a metal sheath 1 of the power cable.
3, a metal shielding layer 14 provided on the outer periphery of the outer semiconductive layer 12, and a copper body tube 16 provided on the outer periphery of the metal shielding layer 14 via a waterproof compound 15 and having a corrosion-resistant vinyl layer 17 on the surface. An insulating tube 18 for bisecting the copper body tube 16 in the axial direction, a jumper wire 19 for electrically connecting the copper body tubes 16 on both sides of the insulation tube 18, and a high-frequency iron core detachably provided on the jumper wire 19. Normally, the high-frequency iron core 20 is detached from the jumper wire 19 so that the copper body tubes 16 on both sides of the insulating tube 18 are short-circuited, and the high-frequency iron core 20 is attached to the jumper wire 19 during measurement. Thus, the copper body tubes 16 on both sides of the insulating tube 19 are configured to be insulated from high-frequency signals.

A pair of metal foil electrodes 21 are attached to the outer surface of the corrosion-resistant vinyl layer 17 on both sides of the insulating tube 18 with respect to the ordinary connection portion having such a configuration. 22 are connected, and
A partial discharge measuring device 23 is connected to the detection impedance 22.

In the above configuration, when performing the partial discharge measurement, the high-frequency core 2 is connected to the jumper wire 19 of the ordinary connection portion.
By attaching 0, the copper body tubes 16 on both sides of the insulating tube 18 are insulated from high-frequency signals. In this state, when a partial discharge occurs in the insulating layer portion of the ordinary connection portion, a partial discharge pulse is induced between the copper body tubes 16 on both sides of the insulating tube 18 and detected from the pair of metal foil electrodes 21. When the partial discharge pulse is detected by the pair of metal foil electrodes 21, a potential difference occurs at both ends of the detection impedance 22, and the partial discharge measuring device 23
Tunes and amplifies the partial discharge signal based on this potential difference at the frequency having the highest S / N ratio to measure the partial discharge.

In the above embodiment, a high-frequency iron core 20 is provided on the jumper wire 19 so that a predetermined value of high-frequency impedance is added to the jumper wire 19 connecting the copper body tube 16 of the normal connection portion. The partial discharge pulse can be directly taken out, and the detection sensitivity of the partial discharge generated at the normal connection can be improved. Even if the high-frequency iron core 20 is provided on the jumper wire 19, the commercial frequency impedance is low, so that it functions as a normal connection part.

FIG. 2 shows a second partial discharge measuring method according to the present invention.
In this example, the measurement of the partial discharge generated in the normal connection portion is performed. In this embodiment, the same portions as those in FIG. 1 are denoted by the same reference numerals and symbols, and thus duplicate description will be omitted. However, the outer semiconductive layer 11 of the power cable is usually provided on the outer periphery of the connection sleeve 8 of the connection portion. A configuration in which a subsequent external semiconductive layer 12 is formed and a metal shielding layer 14 having an edge portion 14A on the outer periphery of the external semiconductive layer 12 is different from FIG.

In the above configuration, when performing the partial discharge measurement, the high-frequency core 2 is connected to the jumper wire 19 of the ordinary connection portion.
By attaching 0, the copper body tubes 16 on both sides of the insulating tube 18 are insulated from high-frequency signals. In this state, when a partial discharge is generated in the insulating layer portion of the ordinary connection portion, a partial discharge pulse is induced between the copper body tubes 16 on both sides of the insulating tube 18 by electrostatic coupling via the metal shielding layer 14, and a pair of the discharge pulses is generated. Metal foil electrode 2
1 is detected. When the partial discharge pulse is detected by the pair of metal foil electrodes 21, a potential difference is generated between both ends of the detection impedance 22, and the partial discharge measuring device 23 tunes the partial discharge signal based on the potential difference at the frequency having the highest S / N ratio. Amplify and measure partial discharge.

FIG. 3 shows a third embodiment of the partial discharge measuring method according to the present invention.
In this example, the measurement of the partial discharge generated in the normal connection portion is performed. In this embodiment, the same portions as those in FIG. 2 are denoted by the same reference numerals and symbols, and duplicate description will be omitted. However, the edge cut portions 14B are provided at both ends of the outer periphery of the outer semiconductive layer 12 of the normal connection portion. 2 differs from FIG. 2 in the configuration in which the metal shield layer 14 is formed and the configuration in which the primary winding of the detection impedance 22 is connected to the metal shield layer 14 and the copper body tube 16 via the detection lead wire 26. . The detection lead wire 26 on the side connected to the metal shielding layer 14 is connected to the copper body tube 16 via an arrester 25 to protect the measuring instrument and the like from surge voltage. 24 is a spare detection lead wire.

In the above configuration, when a partial discharge occurs in the insulating layer portion of the normal connection portion, a partial discharge pulse is guided to the metal shielding layer 14. For this reason, a potential difference occurs at both ends of the detection impedance 22 in which one of the primary windings is connected to the copper body tube 16, and the partial discharge measuring device 23 converts a partial discharge signal based on this potential difference at a frequency having the highest S / N ratio. Tune, amplify and measure partial discharge.

FIG. 4 shows a fourth embodiment of the partial discharge measuring method according to the present invention.
In this example, the measurement of the partial discharge generated in the normal connection portion is performed. In this embodiment, the same portions as those in FIG. 3 are denoted by the same reference numerals and symbols, and thus redundant description will be omitted. However, an edge cut portion 14C is formed at the center of the metal shielding layer 14 of the normal connection portion. A configuration in which the primary winding of the detection impedance 22 is connected to the metal shielding layers 14 on both sides of the edge cutout 14C via a detection lead wire 26, and one of the detection lead wires 26 is a copper body tube via an arrester 25A. 16 and the configuration in which the other of the detection lead wires 26 is connected to the neutral wire 22A of the detection impedance 22 via the arrester 25B.

In the above configuration, when a partial discharge occurs in the insulating layer portion of the ordinary connection portion, a partial discharge pulse is guided to the metal shielding layers 14 on both sides of the marginal portion 14C, and the metal shielding layers 14 on both sides are partially It has a potential corresponding to the discharge pulse. For this reason, a potential difference occurs between the metal shielding layers 14 on both sides at both ends of the detection impedance 22, and the partial discharge measuring device 23
Tunes and amplifies the partial discharge signal based on this potential difference at the frequency having the highest S / N ratio to measure the partial discharge.

FIG. 5 shows an equivalent circuit of the partial discharge measuring method at the insulated connection part. The conductor 27 connected by the connection sleeve 28 and the copper body 30 insulated by the insulating cylinder 29 are electrostatically coupled, and the copper body 30 is electrically connected. And detection impedance 3
The electrostatic coupling of 1 causes a potential difference in the detection impedance 31 due to partial discharge. Here, the configurations of the above-described first and second embodiments have the same equivalent circuit as this insulated connection portion, and the configuration of the third embodiment has a configuration in which the metal electrode portion is C ₁ and the cable portion is C 1. ₂ and the configuration of the fourth embodiment is such that each metal electrode portion is C _1.
And corresponding to the C _2.

[0024]

As described above, according to the method for measuring partial discharge of the present invention, a normal connection portion having at least an outer periphery of a semiconductive layer and a metal shielding layer cut off is formed.
Since the partial discharge signal is extracted through the metal shield layer of the normal connection, the detection sensitivity of the partial discharge generated in the normal connection can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a first embodiment of the present invention.

FIG. 2 is an explanatory view showing a second embodiment of the present invention.

FIG. 3 is an explanatory view showing a third embodiment of the present invention.

FIG. 4 is an explanatory view showing a fourth embodiment of the present invention.

FIG. 5 is an explanatory diagram showing an equivalent circuit of an insulated connecting portion.

FIG. 6 is an explanatory view showing a conventional partial discharge measuring method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cable 2 Insulated connection part 3 Insulation cylinder 4 Metal foil electrode 5 Detection impedance 6 Corrosion-proof vinyl layer 7 Conductor 8 Connection sleeve 9 Insulator 10 Extrusion reinforcement insulation part 11 External semiconductive layer 12 External semiconductive layer 12A Edge cut 13 Metal sheath Reference Signs List 14 Metal shielding layer 14A, 14B, 14C Edge cutout 15 Waterproof compound 16 Copper body tube 17 Corrosion-proof vinyl layer 18 Insulation cylinder 19 Jumper wire 20 High-frequency iron core 21 Metal foil electrode 22 Detected impedance 22A Neutral wire 23 Partial discharge meter 24 Detection Lead wire 25 Arrester 25A, 25B Arrester 26 Lead wire for detection

Continuing on the front page (72) Inventor Kan Endo 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture Power Systems Research Laboratories, Hitachi, Ltd. (72) Inventor Tsutomu Tashiro 5-chome Hidakacho, Hitachi City, Ibaraki Prefecture No. 1-1 Nippon Electric Cable Co., Ltd. Power System Research Laboratory (72) Inventor Hiroshi Suzuki 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture Nippon Electric Cable Co., Ltd. Power System Research Laboratory (72) Inventor Imai Tomoaki 5-1-1 Hidakacho, Hitachi City, Ibaraki Prefecture Power System Laboratory, Hitachi, Ltd. (56) References JP-A-63-131079 (JP, A) JP-A-8-5701 (JP, A) JP-A-6-331685 (JP, A) JP-A-64-59085 (JP, A) JP-A-7-174809 (JP, A) JP-A-2-95275 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) G01R 31/12

Claims (2)

(57) [Claims] 1. An outer semiconductive layer and a metal shielding layer which are cut off via an insulator on an outer periphery of a conductor connection portion of a power cable, and an insulating cylinder is formed on an outer periphery of the outer semiconductive layer and the metal shielding layer. The copper body tube separated by the above is arranged, the copper body tube is connected by a jumper wire to form a normal connection portion, a high-frequency iron core is attached to the jumper wire, and the high-frequency impedance of the jumper wire is set to a predetermined value. A pair of metal foil electrodes are attached to both sides of the insulating cylinder on the corrosion-resistant vinyl layer of the copper body tube, a detection impedance is connected to the pair of metal foil electrodes, and a partial discharge is performed based on a potential difference generated in the detection impedance. A partial discharge detection method comprising extracting a signal. 2. A pair of metal shielding layers partially cut off via an insulator and an external semiconductive layer are formed on the outer periphery of the conductor connecting portion of the power cable, and the outer periphery of the pair of metal shielding layers is insulated on the outer periphery of the pair of metal shielding layers. A copper body tube separated by a tube is arranged, and the copper body tube is connected with a jumper wire to form a normal connection portion.A high-frequency iron core is attached to the jumper wire, and a high-frequency impedance of the jumper wire is set to a predetermined value. A pair of metal foil electrodes are attached to both sides of the insulating cylinder on the corrosion-resistant vinyl layer of the copper body tube, a detection impedance is connected to the pair of metal foil electrodes, and a portion based on a potential difference generated in the detection impedance is provided. A partial discharge detection method, wherein a discharge signal is extracted.