JPH04223281A - Method and device for judging partial electric discharge generation location - Google Patents

Abstract

PURPOSE:To enable judging the partial discharge generation location of power cable lines safely and accurately by detecting the polarity of pulse voltage generated on a metal shield layers and the direction of pulse current flowing in the longitudinal direction of the metal shield layers. CONSTITUTION:When a partial discharge pulse comes in, a voltage pulse signal generated between metal sheaths 4A and 4B on both sides of insulated connection part 2 is detected as the electric potential difference between both ends of detection impedance 5 by way of an amplifier 5a, observed with an oscilloscope 9, and stored in a memory 10a. A current also flows in a wire shield 1a in either direction, induction current flows in a coil 6 in either direction, and electric potential difference is caused beteen both ends of a detection impedance 8. It is observed with the oscilloscope 9 together with the voltage pulse by way of an amplifier 8a and stored 10a. With an arithmetic device 10, the pulse propagation direction is judged from the polarity relation of the voltage and current pulses stored 10a, and is indicated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for determining the direction of partial discharge occurrence, and more particularly to a method and apparatus for determining the direction of partial discharge occurrence in a cable having a metal shielding layer.

0002

BACKGROUND OF THE INVENTION It is important for partial discharge detection to determine which direction the partial discharge occurs from the measurement location.

[0003] In order to distinguish partial discharges in high-voltage induction motors used in nuclear power plants from external noise, the propagation direction of partial discharge pulses in the drive cable is determined, and based on this, partial discharges and external noises are distinguished. Attempts have been made to identify noise. One such method is to detect the waveforms of the voltage wave and current wave of the propagating wave using a circuit configuration as shown in FIG. 6, and to discriminate based on the relationship between the waveforms. This method will be explained below.

In FIG. 6, a coupling capacitor 64 and a detection resistor 65 are connected in series between the conductor and the ground in the middle of a drive cable 63 connecting a power source 61 and a motor 62, and a The input terminal of the voltage wave amplification circuit 66 is connected to. Further, a high frequency zero-phase current transformer 67 is provided surrounding the drive cable 63 and connected to a current wave amplification circuit 68. The outputs of the voltage wave amplification circuit 66 and the current wave amplification circuit 68 are connected to a discrimination circuit 69, and the output of the discrimination circuit 69 is connected to the counting circuit 60.

The operation of the configuration of FIG. 6 is as follows. In the discrimination circuit 69, when the output waves of the voltage wave amplification circuit 66 and the current wave amplification circuit 68 exceed a certain set level, respective shaped pulses are generated, and when these pulses occur simultaneously, the discrimination circuit 69, it is determined that it is a partial discharge pulse, a pulse is generated, and the counting circuit 6
It is counted as 0. It is estimated that this count value is essentially the number of pulses generated on the motor side.

[0006]

However, the above-described conventional methods cannot be applied to live power cables having a metal shielding layer. One of the reasons for this is that the partial discharge pulse current flowing through the internal high-voltage conductor and the partial discharge pulse current flowing through the metal shielding layer cancel each other out, resulting in almost no output from the zero-phase current transformer. The reason is
Since the exposed part of the high voltage conductor must be used to connect the coupling capacitor, e.g.
In some cases, such as in a substation, a coupling capacitor must be provided at a location remote from the measurement point, reducing detection sensitivity. Furthermore, since it is necessary to connect a coupling capacitor to the exposed part of the high-voltage conductor, there is a safety problem when measuring in a live line state.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to realize a method for determining the direction of partial discharge in a power cable line consisting of a cable with a metal shielding layer.

Another object of the present invention is to realize a device for determining the direction of occurrence of partial discharge in a power cable line consisting of a cable having a metal shielding layer.

[0009]

[Means for Solving the Problems] In the method for determining the direction of partial discharge occurrence of the present invention, in order to realize a method for determining the direction of partial discharge occurrence in a power cable line consisting of a cable having a metal shielding layer, Detects the polarity of the pulse voltage generated in the cable's metal shielding layer based on the
Also, based on the partial discharge, the direction of the pulse current flowing along the length of the metal shielding layer is detected, and based on this, the propagation direction of the partial discharge pulse, that is, the direction of partial discharge occurrence (
(based on the measurement location). To detect the polarity of the pulse voltage generated on the metal shielding layer, it is possible to directly detect the pulse voltage generated on the metal shielding layer and determine the polarity. ) The pulse voltage generated in the metal shielding layer by detecting the polarity of the pulse voltage generated between the metal foil electrode provided on the outer periphery of the metal foil electrode and the ground, or between adjacent metal shielding layers via an insulated connection. It is also possible to determine the polarity of the The direction of the pulsed current flowing along the length of the metal shielding layer is determined by the spiral metal shielding layer (
It is possible to connect a detection impedance between both ends of a coil installed outside the wire shield (wire shield) or between two points on a cable separated by an appropriate distance, and detect and determine the polarity of the high-frequency pulse generated at both ends. can. The method for determining the direction of occurrence of partial discharge according to the present invention can also be applied to determination in live power cable lines.

In the device for determining the direction of partial discharge occurrence of the present invention, in order to realize a device for determining the direction of partial discharge occurrence in a power cable line consisting of a cable having a metal shielding layer, the metal shielding of the cable is determined based on the partial discharge. means for detecting the polarity of the pulsed voltage generated in the layer; means for detecting the direction of the pulsed current flowing along the length of the metal shielding layer provided outside the metal shielding layer; and determining means for determining the propagation direction of the pulse based on the polarity of the pulse voltage and the direction of the pulse current. As means for detecting the polarity of the pulse voltage, for example, an impedance connected between a metal shielding layer such as a wire shield and the earth, or an impedance connected between a metal foil electrode provided on the outer periphery of an insulating sheath outside the metal shielding layer and the earth are used. A connected impedance or an impedance connected between metal shielding layers on either side of the insulating connection can be used. Examples of the means provided outside the metal shielding layer to detect the direction of the pulse current flowing along the metal shielding layer include:
A coil installed outside the spiral metal shielding layer (wire shield) wound around the cable and a detection impedance connected to both ends of this coil, or connected to two points separated by an appropriate distance on the metal shielding layer. detection impedance can be used.

[0011] Examples will be shown below to provide a more detailed explanation of the present invention.

0012

Embodiment 1 FIG. 1 shows a configuration (partial discharge direction determining device) used in the method for determining the direction of partial discharge occurrence according to the present invention. In Figure 1, the cable 1 is a wire shield cable, and the wire shield 1a is arranged on the outside of the insulating layer (not shown) of the cable 1, with an appropriate winding pitch, S-twist, Z-twist, or alternately S-twist and Z-twist. It is wrapped so that Metal sheaths 4A, 4 on both sides of the insulator 3 of the insulated connection part 2
A detection impedance 5 is connected between B and B. An amplifier 5a is connected to the detection impedance 5. A coil 6 is provided outside the wire shield 1a so as to interlink with the magnetic flux generated by the current flowing through the wire shield 1a. The winding direction of the coil 6 is depolarized with respect to the winding direction of the wire shield (indicated by : in the figure).
. A load resistor 7 and a detection impedance 8 are connected in parallel to both ends of the coil 6. An amplifier 8a is connected to the detection impedance 8. Amplifier 5a and amplifier 8
Each output of a is connected to an oscilloscope 9 and also to an arithmetic unit 10. The calculation device 10 has a memory 10a, and input signals regarding voltage waves and current waves are stored in the memory 10a before calculation.

The operation of the above configuration will be explained below. When a partial discharge pulse arrives from the right or left side of FIG.
A voltage wave pulse signal is generated at A and 4B, which is detected as a potential difference across the detection impedance 5 via the amplifier 5a, observed by the oscilloscope 9, and stored in the memory 10a. On the other hand, also in the wire shield 1a,
A current flows in either direction based on the partial discharge pulse, and an induced current in either direction is generated in the coil 6 wound around the wire shield 1a. Based on this induced current, a potential difference is generated across the detection impedance 5, which is observed together with the voltage wave pulse signal by the oscilloscope 9 via the amplifier 8a, and is simultaneously stored in the memory 10a. Arithmetic device 10
Then, the pulse propagation direction is determined from the relationship between the polarities of the voltage wave and current wave pulses stored in the memory 10a, and the results are displayed on a suitable display means (not shown). An oscilloscope 9 may be used as a display means.

For example, assume that a partial discharge pulse arrives from the right side of FIG. 1, and its polarity is positive on the inner conductor side and negative on the wire shield side. Metal sheath 4A, 4
The polarity of the pulse generated at B is positive for the left metal sheath 4A and negative for the right metal sheath 4B. on the other hand,
A pulse current flows through the wire shield from the right side of the figure toward the left side based on the partial discharge pulse coming from the right side of FIG. Since the winding direction of the coil 6 is depolarized with respect to the winding direction of the wire shield, an induced current is generated in the coil 6 from the left side to the right side in the figure, and the detection impedance 8
The potential difference generated across the terminal C has a negative polarity and the terminal D on the right has a positive polarity. Therefore, when determining the actual direction of partial discharge occurrence, when such a polarity relationship is obtained, it can be determined that the partial discharge pulse has arrived from the right side.

When the polarity of the pulse voltage is opposite, that is, the internal conductor side is negative and the wire shield side is positive, the metal sheath 4A of the insulated connection part 2 shows negative, the metal sheath 4B on the right side shows positive, and the wire shield Since the direction of the current flowing in is from the left to the right, the potential difference generated across the detection impedance 8 is the terminal C on the left.
indicates positive polarity, and terminal D on the right indicates negative polarity. That is, when a partial discharge pulse arrives from the right side, regardless of the polarity of the partial discharge pulse, the polarity of the metal sheaths 4A, 4B on both sides of the insulating connection part 2 and the detection impedance 5
The polarity of the potential difference produced is opposite. Therefore, when such a polarity relationship is obtained, it is determined that the partial discharge pulse has arrived from the right side.

Similarly, when a partial discharge pulse arrives from the left side, regardless of the polarity of the partial discharge pulse,
The polarity of the metal sheaths 4A, 4B and the polarity of the potential difference generated in the detection impedance 8 become the same. Polarity of metal sheaths 4A and 4B on both sides of insulated connection part 2 and detection impedance 8
Table 1 summarizes the mutual relationship between the polarities of the potential differences that occur and the directions in which the partial discharge pulses arrive. Using this table, the direction in which the partial discharge pulse arrives is determined. In addition,
In Table 1, the metal sheath 4A is shown as A, and the metal sheath 4B is shown as B.

Table 1 is for the case where the winding direction of the coil 6 is depolarizing with respect to the winding direction of the wire shield, and when the winding direction is opposite to the wire shield, the winding direction at both ends C and D of the coil is Since the polarities are opposite, when the relative relationship of the polarities with the connections A and B becomes the same, it is determined that the direction of arrival of the pulse is from right to left. The determination of the pulse arrival direction based on the relationship shown in Table 1 is performed by the arithmetic unit 10 based on the polarity of each pulse of the voltage wave and current wave stored in the memory 10a.

[0018]

Embodiment 2 FIG. 2 shows an example in which voltage wave pulses are detected using a detection impedance inserted between a ground wire (lead wire) from a metal shielding layer such as a normal connection and the ground. The cable 1 and wire shield 1a are the same as in FIG. Grounding wire (lead wire) 21 from the metal shielding layer of the normal connection part, etc.
A detection impedance 22 for detecting voltage wave pulses is inserted between the ground and the ground. Furthermore, both ends of a detection impedance 23 for detecting current waves are connected to two points C2 and D2 on the wire shield. The detection impedance 22 and the detection impedance 23 are
As in the first embodiment, they are each connected to an amplifier, and their outputs are connected to an oscilloscope and an arithmetic unit. In FIG. 2, these illustrations are omitted.

The operation of the above configuration will be explained below. When a partial discharge pulse arrives from the right or left side of FIG. 2, the detection impedance 22 inserted between the ground wire 21 and the earth
, a potential difference is generated based on the voltage wave pulse. This potential difference has a polarity that corresponds to the propagation direction and polarity of the partial discharge pulse. Further, a pulse current flows in either direction along the length of the wire shield, and a potential difference (high frequency pulse voltage) based on the inductance of the wire shield between the two points C2 and D2 is generated in the detection impedance 23. These potential differences are each amplified via an amplifier, observed with an oscilloscope, and simultaneously stored in the memory of the arithmetic unit. Similar to the first embodiment (for example, using the relationships shown in Table 1), the direction of arrival of the pulse is determined by the arithmetic unit based on the polarity of each pulse of the voltage wave and current wave stored in the memory.

[0020]

Embodiment 3 FIG. 3 shows an example in which voltage wave pulses are detected using a detection impedance inserted between a metal foil electrode provided outside the vinyl resin anticorrosion layer of the cable and the ground. The cable 1 and wire shield 1a are the same as in FIG. A metal foil electrode 3 is placed on the outside of the vinyl resin corrosion protection layer 1b of the cable.
1 is provided, and a detection impedance 32 is connected between this and the ground. The vinyl resin anti-corrosion layer 1b is not shown in the figure except for the portion where the metal foil electrode 31 is provided. As in the first embodiment, the detection impedance 32 is connected to an amplifier, and its output is connected to an oscilloscope and an arithmetic unit, but these are not shown in FIG. 3. The detection impedance 23 connected to the two points C2 and D2 on the wire shield is the same as in FIG.

The operation of the above configuration will be explained below. When a partial discharge pulse arrives from the right or left side of FIG. This occurs between the metal foil electrode 31 and the ground, and is detected as a potential difference between both ends of the detection impedance 32. Further, a pulse current flows in either direction along the length of the wire shield 1a, and a current wave pulse is generated in the detection impedance 23 connected between C2 and D2. Similar to the second embodiment, these potential differences are amplified by an amplifier, observed by an oscilloscope, and simultaneously stored in the memory of the arithmetic unit. Based on the polarity information stored in the memory, the pulse arrival direction is determined by the arithmetic unit as in the first embodiment.

In Examples 2 and 3, the current wave pulse was detected by the detection impedance 23 connected between two points on the wire shield 1a, but the detection impedance 23 connected between two points on the wire shield 1a was A coil and sensing impedance may also be used.

[0023]

Embodiment 4 When using the method of Embodiment 1, it is often the case that the winding direction of the wire shield 1a at the observation point is unknown. In this case, the direction of partial discharge cannot be determined because the relationship between the winding direction of the coil 6 wound around the outside of the wire shield 1a and the winding direction of the wire shield 1a cannot be known. In such a case, as shown in FIG. 4, a coil 41 for pulse injection is wound around the outside of the wire shield at an appropriate position on the right (or left) side of the coil 6 for current wave detection, and The pulse generator 42
Connect to.

When a pulse of known polarity is injected from the pulse generator 42 into the cable line via the coil 41, a pulse voltage of either polarity is generated across the coil 6 for current wave detection. From this polarity, it can be known whether the winding direction of the current wave detection coil 6 is polarizing or depolarizing with respect to the wire shield.

[0025]

[Embodiment 5] In the first embodiment, the current wave pulse detection coil 6 was provided only on one side (the right side in the figure) of the insulated connection part 2, but in this example, as shown in FIG. A current wave pulse detection coil 51 was also provided on the left side. coil 5
1, a load resistor 52 and a detection impedance 53 are connected in parallel. The detection impedance 53 is an amplifier 54
The output side of the amplifier 54 is connected to the oscilloscope 9 and the arithmetic unit 10.

The procedure for determining the location where partial discharge occurs using the configuration shown in FIG. 5 is as follows. The propagation direction of the partial discharge pulse is determined on both sides of the insulated connection portion 2 using the same method as in Example 1. If the propagation direction is the same on both sides of the insulated connection part 2, it is determined that the partial discharge is occurring outside of the insulated connection part 2 (or its vicinity). If the propagation direction is opposite, there is a strong possibility that the problem occurs at the insulated connection portion 2.

In each of the above embodiments, the direction of partial discharge occurrence is determined in a live line state, but the method and apparatus of the present invention can also be used to determine the direction of partial discharge occurrence in a power outage state. Applicable.

[0028]

According to the method of the present invention, it is possible to accurately determine the direction in which a partial discharge occurs in a power cable line consisting of a cable having a metal shielding layer. According to the method of the present invention, such determination of the direction in which partial discharge occurs can be safely performed even in a live wire state.

Further, according to the apparatus of the present invention, it is possible to accurately determine the direction in which partial discharge occurs in a power cable line consisting of a cable having a metal shielding layer. In particular, such determination of the direction in which partial discharge occurs can be safely performed even in a live wire state.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a configuration used in an embodiment of a method for determining the direction of partial discharge occurrence according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration used in another embodiment of the method for determining the direction of partial discharge occurrence according to the present invention.

FIG. 3 is an explanatory diagram showing a configuration used in a third embodiment of the method for determining the direction of partial discharge occurrence according to the present invention.

FIG. 4 is an explanatory diagram showing a configuration used in a fourth embodiment of the method for determining the direction of partial discharge occurrence according to the present invention.

FIG. 5 is an explanatory diagram showing a configuration used in a fifth embodiment of the method for determining the direction of partial discharge occurrence according to the present invention.

FIG. 6 is an explanatory diagram showing a conventional method for determining the direction of partial discharge occurrence.

[Explanation of symbols]

1 cable
1a Wire shield 1b Vinyl resin anti-corrosion layer
2 Insulated connection part 3 Insulator
4A, 4B Metal shielding layer 5 detection impedance
5a Amplifier 6 Coil
7 Load resistance 8 Detection impedance
8a Amplifier 9 Oscilloscope
10 Arithmetic device 10a Memory
21 Ground wire 22 Detection impedance
23 Detection impedance 31 Metal foil electrode
32 Detection impedance 41 Pulse injection coil
42 Pulse generator 51 Current wave pulse detection coil 5
2 Load resistance 53 Detection impedance
54 Amplifier 60 Counting circuit
61 Power supply 62 Electric motor
63
Drive cable 64 Coupling capacitor
65 Detection resistor 66 Voltage wave amplification circuit
67 High frequency zero phase current transformer 68 Current wave amplification circuit
69 Discrimination circuit

Claims (10)

[Claims] 1. A method for determining the direction of partial discharge occurrence in a cable having a metal shielding layer, in which the polarity of a pulse voltage generated in the metal shielding layer is detected, and a pulse current flowing along the length of the metal shielding layer is detected. detecting the direction of the partial discharge, determining the propagation direction of the partial discharge pulse from the polarity of the pulse voltage and the direction of the pulse current, and determining the direction of partial discharge generation based on the measurement location. Direction determination method. 2. The cable has an insulated connection, and the polarity of the pulsed voltage is detected by detecting the polarity of the pulsed voltage generated between the adjacent metal shielding layers via the insulated connection. The method of determining the direction of partial discharge occurrence according to claim 1, wherein the method is performed. 3. The cable has an insulating sheath covering the outer periphery of the metal shielding layer, and the polarity of the pulse voltage is detected by providing a foil-like electrode on the outside of the insulating sheath, and connecting the foil-like electrode to the ground. 2. The method of determining the direction of partial discharge occurrence according to claim 1, wherein the method is carried out by detecting the polarity of a pulse voltage generated during the period. 4. The metal shielding layer is a spiral metal shielding layer wound around the cable, and the direction of the pulsed current is detected by providing a coil outside the spiral metal shielding layer, and detecting the direction of the pulse current generated in the coil. 4. A partial discharge generation direction determining method according to claim 1, wherein the method is performed by detecting the polarity of a pulse current. 5. Detection of the direction of the pulse current is performed by connecting a detection impedance between two points in the length direction of the metal shielding layer and detecting the polarity of the pulse voltage generated across the detection impedance. The method for determining the direction of partial discharge occurrence according to any one of claims 1 to 3. 6. A partial discharge direction determination device for determining the direction of partial discharge occurrence in a cable having a metal shielding layer, comprising: means for detecting the polarity of a pulse voltage generated in the metal shielding layer; comprising means for detecting the direction of the pulse current flowing along the horizontal direction, and determining means for determining the propagation direction of the partial discharge pulse based on the polarity of the pulse voltage and the direction of the pulse current detected by these means. A device for determining the direction of partial discharge occurrence, characterized by: 7. The partial discharge according to claim 6, wherein the means for detecting the polarity of the pulse voltage comprises a foil electrode provided outside the insulating sheath and a detection impedance connected between the electrode and the ground. Generation direction determination device. 8. The cable has an insulated connection, and the means for detecting the polarity of the pulsed voltage is connected between the metal shielding layers on both sides of the insulated connection and detects the polarity of the pulsed voltage between the metal shielding layers. 7. The partial discharge generation direction determining device according to claim 6, wherein the device is a means for detecting a partial discharge. 9. The metal shielding layer is a spiral metal shielding layer wound around the cable, and the means for detecting the direction of the pulse current includes a coil provided outside the spiral metal shielding layer; 9. A partial discharge generation direction determining device according to claim 6, further comprising means for detecting the direction of a pulse current generated in said coil. 10. The means for detecting the direction of the pulse current comprises a detection impedance connected between two points in the length direction of the metal shielding layer, and means for detecting the polarity of the pulse voltage generated at both ends of the detection impedance. A partial discharge generation direction determining device according to any one of claims 6 to 8.