JP2670426B2 - Method and apparatus for locating position of partial discharge of power cable - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial discharge measurement of a cable for evaluating the insulation performance and the degree of insulation deterioration of a long power cable in a live state or a test state.
The present invention relates to a method and apparatus for locating a partial discharge occurrence position of a power cable that accurately locates the occurrence site.

[0002]

2. Description of the Related Art The main causes of dielectric breakdown of power cables such as CV cables are defects such as external damage, defective construction, and water trees generated in live power cables. In the event of damage or poor construction, a partial discharge of a certain magnitude occurs, and eventually this partial breakdown portion (referred to as an electrical tree) evolves, leading to complete cable breakdown. A breakdown from a water tree portion or a fine defect inside the cable also causes a partial insulation breakdown and finally leads to a breakdown of the entire path. Therefore, a partial discharge pulse current always flows before the cable breakdown.

Also, in the case of an OF cable or a pipeline air cable (GIL), there is a defect not only in a main insulating portion such as oil-impregnated paper or SF6 gas but also in a connecting portion and a composite insulating portion such as an insulating support. Partial discharge may occur due to metal powder inside or inside. Therefore, partial discharge measurement is very important as a method for evaluating insulation of power cables. In particular, since the connection work at the site does not go through a shipping test at the factory, it is important to perform the partial discharge measurement at the site to ensure its reliability.

Various methods have been proposed in the past as a method of locating the position of occurrence of partial discharge. For example, Japanese Patent Application No. 1-184474 discloses a method of arranging a plurality of electric field photosensors along a power cable and locating the generation position thereof by the arrival time difference of partial discharge pulses detected by the electric field photosensor. Has been done. As a method of locating the partial discharge occurrence position, a method of calculating the position where the partial discharge pulse is generated from the nature and propagation speed of the partial discharge pulse propagating and reflecting inside the cable as described above was a typical example.

As a method that is a further development of the above method, as shown in Japanese Patent Application No. 3-237514, a partial discharge pulse propagating inside a cable is split and propagated to the sheath side at a sheath insulation connection. Although a position locating method using the phenomenon of occurrence has been proposed, the position of the locating position is determined from the difference in propagation time after previously grasping the propagation speed of each part in advance.

[0006]

In the above-described method of calculating the position of occurrence based on the propagation and reflection of the partial discharge pulse, it is necessary to measure the propagation speed, the reflection point, and the like in advance. There is a large measurement error in the value measured in several hundreds of meters, and there is a drawback that the error of the orientation position becomes large when the local discharge generation position is calculated using this value in the long cable at the site.

[0007] Further, normally, a coaxial cable or an optical fiber
A measurement line such as a cable is drawn in, but it was necessary to measure the propagation velocity of this portion in advance and correct it.
Even in this case, there is a problem that it is easily affected by a measurement error of the propagation velocity and the measurement line length, a phase delay inside the measuring instrument, and the like, and eventually the error of the partial discharge occurrence position orientation is expanded.

The present invention has been made in view of the above-mentioned problems of the prior art, and directly and easily corrects the propagation speed, the transmission delay of the measurement line, and the device delay, and corrects them accurately. It is an object of the present invention to provide a method and apparatus for locating a partial discharge occurrence position of a power cable, which is capable of locating a partial discharge occurrence position.

[0009]

FIG. 1 is a diagram illustrating the principle of the present invention. In the figure, 1 is a power cable, 2 is an intermediate connection part, 3 is a measurement point, 3a is a measurement part for measuring a partial discharge pulse or a simulated pulse detected at a terminal connection part or each intermediate connection part, and 3b is a measurement position. Are the first and second simulated pulse generators provided in the vicinity of the intermediate connection, and 6 is a transmission line for transmitting the measurement signal and the simulated pulse.

In order to solve the above-mentioned problems, the invention of claim 1 of the present invention is such that a partial discharge detector is attached to the terminal connection part or each intermediate connection part 2 of the long power cable 1, and the terminal connection part and each intermediate connection are provided. In the partial discharge occurrence position locating method of the power cable for locating the partial discharge occurrence position by the arrival time difference of the partial discharge pulse signals detected at at least two or more places of the section 1 or the cable 1, at least two places are previously set. Simulated pulses were sequentially injected from the terminal connection part, the intermediate connection part, or between the conductor sheaths of the cable, and the transmission delay of the partial discharge pulse and the time delay of the measurement system in the predetermined section of the cable were measured, and the actual partial discharge occurred. At this time, the time difference between the actual partial discharge pulse signals obtained from at least two measured points and the transmission delay and measurement obtained at the time of injection of the above-mentioned simulated pulse. Based on the time delay of the system, in which so as to orientation actual partial discharge generation position.

According to a second aspect of the present invention, in the first aspect of the invention, the simulated pulse is injected from the foil electrode attached to the terminal connection portion or the intermediate connection portion 2. According to a third aspect of the present invention, in the first or second aspect of the invention, a portion for measuring the actual partial discharge pulse and the simulated pulse and a portion for injecting the simulated pulse are separated from the measured insulation connection portion and the cable. It is a place where it was.

The invention of claim 4 of the present invention is the same as claims 1 and 2.
Alternatively, in the invention of claim 3, the simulated pulse injecting means is provided at least at two or more places, and the simulated pulse is injected between the terminal connecting portion, the intermediate connecting portion or the conductor sheath of the cable with a predetermined time difference from each simulated pulse injecting means. It is intended to be injected. According to the invention of claim 5 of the present invention, detection is performed by a partial discharge detector attached to the terminal connection portion or each intermediate connection portion 2 of the long power cable 1 and a partial discharge detector installed in at least two or more places. Means for determining the arrival time difference of the partial discharge pulses generated,
In a partial discharge generation position measuring system provided with means for locating a partial discharge generation position from the arrival time difference, simulated pulse generation in which simulated pulses are sequentially injected from at least two end connection parts, intermediate connection parts 2 or sheaths of cables. The transmission delay of the partial discharge pulse in a predetermined section of the cable from the arrival time difference at the measurement point 3 of the simulated pulse detected by the means 3b, 4, 5 and the partial discharge detectors installed in at least two or more points and the measurement system Means for measuring time delay and difference in arrival time of partial discharge pulse detected by partial discharge detector at measurement point 3 when partial discharge occurs and transmission delay of partial discharge pulse obtained by injecting the simulated pulse And means for locating the partial discharge occurrence position based on the time delay of the measurement system.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, a gate circuit that passes only a signal of a predetermined specified phase among the applied potential phases and a signal that has passed through the gate circuit are averaged. An averaging circuit for averaging is provided, and the partial discharge pulse signals passing through the gate circuit are averaged. According to a seventh aspect of the present invention, in accordance with the fifth aspect of the present invention, an absolute value circuit for outputting an absolute value of an input signal and an averaging circuit for averaging the output of the absolute value circuit are provided. Is converted into an absolute value by an absolute value circuit, and the partial discharge pulse signals converted into the absolute value are averaged.

[0014]

[Action]

(1) Calculation of basic constants In order to locate the partial discharge occurrence position by the arrival time difference of the partial discharge pulse signals, first calculate the basic constants. As shown in FIG. 2, the distance between the A joint and the B joint of the insulation connection portion 2 is L, the pulse propagation time between them is t, the propagation time from the A joint to the measuring section 3a of the A joint is t _A , and the B joint is The propagation time to the measurement unit 3a of the B joint is t _B.

Here, as shown in FIG. 2A, a simulated pulse is injected from the simulated pulse generator 4 into the A joint,
The difference in arrival times of the pulses of V ₁ and V ₂ observed at the measuring units 3a of the A joint and the B joint, respectively, is measured by the measuring unit 3a.
And this is set as t ₁ . The measurement unit 3a is provided on the same location, by triggering by what people or pulses on the same oscilloscope, the pulse V ₁ and V
A time difference of ₂ can be measured.

Next, as shown in FIG. 2B, the same as above
, The simulated pulse from the simulated pulse generator 5 to the B joint
Is injected, and at the measuring section 3a of the A joint and B joint
Each observed V₁And V_TwoThe arrival time difference of the pulse of
Measured by the measuring unit 3a, t _TwoAnd Then next
Thus, the pulse between the A and B joints
Propagation time t and measurement including transmission delay due to transmission line 6
The difference K in the delay time of the system is calculated. Measuring unit 3 when a simulated pulse is injected into the A joint
Time difference t observed at a ₁Is as follows.

T₁= T + t_B-T_A (1) Measuring unit 3 when a simulated pulse is injected into the B joint
Time difference t observed at a _TwoIs as follows. t_Two= T + t_A-T_B (2) From the above formulas (1) and (2), A joint and B joy
The propagation time t of the pulse between the
The following equation is obtained when the difference K between them is obtained.

K = t_B-T_A= 1/2 (t₁-T_Two) (3) t = 1/2 (t₁+ T_Two) (4) (2) Target of partial discharge occurrence position from actual partial discharge measurement signal
As shown in Fig. 1, from A joint to B joint side
L_xIt is assumed that there is a partial discharge occurrence site at a remote position P.
Partial discharge pulse generated at P propagates to the left and right of cable 1.
And t_1x, T_2xIn time of A joint, B joint
And then t _AAnd t_BObserved by the observation unit 3a after
Is done.

Here, when the arrival time difference Δt between the actual partial discharge pulses V ₁ and V ₂ detected at the A joint and the B joint is observed by the oscilloscope of the observing section 3a, the observed value Δt and (1) are obtained. The partial discharge occurrence position L _x can be calculated as follows from the difference K between the pulse propagation time t and the delay time of the measurement system. Δt = t _2x + t _B − (t _1x + t _A ) = t _2x −t _1x + K (5) where F is from the partial discharge occurrence point P to the A joint and B
Letting the difference in the time of propagation of the partial discharge pulse in the joint, F is expressed as follows.

F = t _2x −t _1x = Δt−K (6) Since t _2x + t _1x = t as described above, | F / t |
When ≦ 1 (when the location where the partial discharge occurs is from the A joint), the propagation time t _1x of the partial discharge pulse between the location where the partial discharge occurs and the A joint is expressed by the following equation (7). t _1x = (t + K-Δt) / 2 (7) Therefore, partial discharge occurrence point (distance from A joint)
Is given by the following equation (8).

L _x = t _1x × (L / t) (8) When F / t = −1, the section on the right side of the B joint in FIG. And when F / t = 1, A in the figure including the boundary points of the section
The section on the left side of the joint is the point where the partial discharge occurs. Further, (L / t) in the equation (8) is equal to the propagation velocity v of the partial discharge pulse.

The above description is for locating the partial discharge generation position from the two joints. However, by locating the partial discharge generation position using any other two joints, and comparing the results. , More reliable orientation can also be performed. Also, the above explanation is for the A joint,
Although the simulation pulse is injected from the B joint, as shown in FIG. 1, the simulation pulse can be injected from the measurement point 3 by the simulation pulse generator 3b, and the position where the partial discharge occurs can be similarly located.

According to the present invention, based on the above-mentioned principle, the place where the partial discharge occurs is located.
In the inventions of 2 and 5, using an actual cable locally,
Since the propagation delay of the partial discharge pulse and the delay corresponding to the delay of the measurement system can be easily corrected as it is, it is possible to perform efficient and highly accurate position location.

According to the third aspect of the present invention, since the location where the actual partial discharge pulse and the simulated pulse are measured and the location where the simulated pulse is injected are located away from the measured intermediate connecting portion and the cable, they are located near the actual cable. Efficient orientation is possible without the need to perform work such as installing a simulated pulse generator. According to the fourth aspect of the present invention, the simulated pulse injection means is provided at least at two or more places, and the simulated pulse is injected from the simulated pulse injection means by a timer with a predetermined time difference between the terminal connection portion, the intermediate connection portion or the conductor sheath of the cable. Since the injection is performed, the simulated pulse can be injected without the need for manpower and efficient measurement can be performed.

According to another aspect of the present invention, there is provided a gate circuit that passes only a signal of a predetermined specified phase among the applied potential phases, and an averaging processing circuit that averages the signals that have passed through the gate circuit. Since the partial discharge pulse signals that have passed through the gate circuit are averaged, it is possible to locate the partial discharge occurrence position with high accuracy. In the invention of claim 7, the partial discharge pulse signal is converted into an absolute value by the absolute value circuit, and the partial discharge pulse signal converted into the absolute value is averaged. Therefore, the same effect as in claim 6 is obtained. Can be obtained, and the averaging process can be simply performed without distinguishing between positive and negative rising edges.

[0026]

【Example】

(1) Example 1 In order to confirm the above-mentioned principle, a confirmation test was conducted by the system shown in FIG. In the figure, 1 is 275 kV,
It is a 2500 mm ² CV cable, and insulation connections S1, S2, S3 are made on this cable, and insulation connections S1, S
A pair of foil electrodes 12 were attached to the sheath insulating portions of S2 and S3.

At the time of detection, a detection impedance 13 was connected to the foil electrode 12 and an oscilloscope 11 was connected to the detection impedance 13 to detect a pulse. At the time of pulse injection, the pulse generator 14 was connected to the foil electrode 12 to inject the pulse. The foil electrode 12
A 250 mm × 250 mm copper plate was used for this. First,
Pulse generator 1 from insulated connections S1 and S3
4 observes the time difference t ₁ of the detection pulse when the simulated pulse is injected and the simulated pulse is injected from the insulation connection portion S1 and the time difference t ₂ of the detection pulse when the simulation pulse is injected from the insulation connection portion S3 by the oscilloscope 11. did.

Next, a simulated pulse is injected from the insulating connecting portion S2 25 m away from the insulating connecting portion S1 to inject
The difference Δt between the arrival time of the pulse detected at 1 in the oscilloscope 11 and the arrival time of the pulse detected at the insulated connection S3 in the oscilloscope 11 was observed. FIG. 4A is a table showing the above results, and
The figure (b) has shown the observed waveform.

As shown in FIG. 7A, a test was conducted 7 times, K, T, v were obtained from the measured values t ₁ , t ₂ , Δt, and the pulse injection position was determined. Part S1 to 25
With respect to the pulse injection position at a distance of m, positioning was possible within a range of about ± 1 m. This is about 2 percent error for a distance of about 100 m between the insulated connections S1 and S2. (2) Embodiment 2 FIG. 5 is a view showing a first embodiment in which the present invention is applied to an actual line. In FIG. 5, 1 is a 275 kV CV cable, 21 is a normal connection section, and 22 is an insulated connection section. A foil electrode 23 of 250 mm × 250 mm is attached to both sides of the sheath insulating portions of the insulating connection portions JB2, JB3, JB5, and JB6.
4 are connected.

Reference numeral 25 is an amplifier, and 26 is an electro-optical converter for converting an electric signal into an optical signal, which is an insulating connection portion JB2, JB.
The signals detected by 3, JB5 and JB6 are amplified by an amplifier 25 and converted into an optical signal by an electro-optical converter 26, and a measurement chamber 30 is passed through an optical fiber 27 (several hundreds of meters to 10 km).
Is transmitted to In the measurement chamber 30, 31 is an opto-electric converter that converts an optical signal transmitted by the optical fiber 27 into an electric signal, 32 is a changeover switch, and the changeover switch 3
2, it is possible to select any 2 outputs from the outputs of the photoelectric converter 31. Reference numeral 33 is an amplifier that amplifies the output of the changeover switch 32, 34 is a partial discharge measuring unit, 36 is an oscilloscope, 37 is an interface, and 35 and 38 are processing devices that perform processing such as locating the partial discharge occurrence position.

In the figure, the insulating connection JB2,
A pulse generator is installed in the vicinity of at least two insulating connections of JB3, JB5, and JB6, a simulated pulse is injected from the pulse generator through the foil electrode 23, and the oscilloscope 36 causes a time difference t between the detection pulses described above. ₁ , t ₂
Is obtained, and the obtained time differences t ₁ and t ₂ of the detection pulses are given to the processing device 38 via the interface 37. And
The processor 38 obtains and stores the difference K between the pulse propagation time t between the insulated connections and the delay time of the measuring device.

When the partial discharge is generated, the partial discharge pulse is detected by the foil electrode 23 and the detection impedance 24 of the insulating connection portion and transmitted to the measuring chamber 30 via the optical fiber 27. The partial discharge pulse transmitted to the measuring chamber 30 is transmitted through the changeover switch 32 and the amplifier 33 to the partial discharge measuring unit 3
4 and the oscilloscope 36. When the occurrence of the partial discharge is detected by the partial discharge measuring device 34, the oscilloscope 36 calculates the arrival time difference Δt of the actual partial discharge pulse detected at the two insulating connection portions.

The obtained arrival time difference Δt is given to the processing device 38 via the interface 37, and is based on the above-described pulse propagation time t between the insulating connections, the delay time difference K of the measuring equipment, and the measured Δt. The location where the partial discharge occurs is located. In addition, insulative connection parts JB2, JB3, JB
5, the simulated pulse is injected from two or more points of JB6, and the propagation time t of the pulse between the insulating connection portions in each,
The difference K between the delay times of the measuring devices is obtained and stored in the processing device 38, and when the partial discharge occurs, the processing device 38 uses the above t and K and the value of Δt detected at each of the two positions to generate the partial discharge occurrence position. By orienting and comparing them, more accurate orientation can be performed.

Further, as shown in FIG. 5, first and second simulated pulse injecting means 28 and 28 'are provided in advance at, for example, two positions of the cable terminating portion, and the simulated pulse injecting means 28 and 2 are provided.
While attaching receivers 29, 29 'to 8',
By providing the transmitter 39 in the measurement chamber 30 and outputting the simulated pulse injection signal from the transmitter 39 with a predetermined time difference, the simulated pulse can be automatically injected with a predetermined time difference.

That is, when injecting the simulated pulse, the processor 38 installed in the measurement chamber 30 first outputs the first simulated pulse injection signal, which is wirelessly transmitted from the transmitter 39 to the receiver 29. A simulated pulse is injected from the first simulated pulse injection means 28. Then, after a predetermined time counted by the timer, a second simulated pulse injection signal is output from the processing device 38, wirelessly transmitted from the transmitter 39 to the receiver 29 ′ in the same manner as above, and the second simulated pulse is injected. Injection means 2
Inject a simulated pulse from 8 '.

With the above configuration, the simulated pulse can be injected without requiring manpower.
Further, if the simulated pulse injecting means 28 and 28 'are provided in the terminal connection portion, the simulated pulse can be injected without the operator entering the tunnel in which the cable is laid, and the working efficiency can be improved. Further, it becomes possible to wirelessly send the simulated pulse injection command.

Incidentally, as means for transmitting the simulated pulse injection signal to the first and second simulated pulse injection means 28, 28 ', for example, a telephone line may be used in addition to the radio as described above. Alternatively, a dedicated line can be used. Further, the installation location of the simulated pulse injection means 28, 28 'is not limited to the terminal connection portion as shown in FIG. 5, but it can be provided at any location of the insulation connection portion or the cable. Two or more means may be provided.

Further, in the above description, the first and second
The simulated pulse injection signal is output from the processing device 38. However, a simulated pulse injection signal output device including a timer or the like is separately provided to transmit the first and second simulated pulse injection signals. Good. By the way, when locating the partial discharge position by the arrival time difference of the partial discharge pulse signals at two or more places as described above, when the arrival time difference is obtained at the rising edge of the pulse, if the measurement signal has a noise component, the pulse is accurately generated. The rise time cannot be obtained, and the error included in the position location result becomes large.

FIG. 6 is a diagram showing an embodiment for coping with the above-mentioned problem. In this embodiment, the accuracy is high by averaging the partial discharge pulses generated in a specific phase of the applied potential phase. It is designed to enable position location.
That is, the original waveform of partial discharge is a damped oscillation waveform, and there are positive and negative pulse rising edges.
Therefore, when the rising edge of the waveform is to be measured with high accuracy, simply averaging the original waveform will result in a distorted rising point, which does not meet the demand.

Therefore, the rise of the pulse is discriminated into a signal of positive polarity and a signal of negative polarity by using a gate circuit, and the rising portion of the pulse is accurately measured by averaging only one of the signals. It is a thing. In FIG. 6, reference numeral 50 denotes a phase gate for passing a partial discharge pulse generated in a specific phase of a potential application phase, 51 denotes an averaging circuit, and 35 denotes an oscilloscope.

In the figure, the two partial discharge signals detected with a time difference are input to the phase gate 50. In the phase gate 50, a phase region in which the gate operates is set in advance, and a pulse having a positive pulse rising edge,
Alternatively, only pulses having a negative pulse rising edge are discriminated and output. The averaging processing circuit 51 averages the signals whose rising polarities are discriminated as described above a specified number of times. The averaged signal is input to the oscilloscope 35, and the arrival time difference between the two partial discharge pulses is obtained.
When the oscilloscope 35 has an averaging processing function, a signal discriminating the rising edge may be directly input to the oscilloscope.

In the averaged partial discharge signal, since the noise component generated at random is reduced, the rising portion of the pulse becomes sharp and the measurement can be performed more accurately. Therefore, it is possible to reduce the reading error included in the arrival time difference between the two partial discharge pulses and perform highly accurate position localization. In the above embodiment, the gate circuit is used to pass the partial discharge pulse signal of a specific phase, but instead of the gate circuit, an absolute value circuit is provided, and the partial discharge pulse signal is changed by the absolute value circuit. The same effect can be obtained by converting into an absolute value and averaging the converted partial discharge pulse signals. Further, when the absolute value circuit is used, the averaging process can be simply performed without distinguishing whether the rising is positive or negative.

FIG. 7 is a diagram showing the result of position orientation when the average value circuit is not provided and when it is provided. The figure shows the arrival time difference Δt of the partial discharge pulse and the position locating result (distance from the slit S1 to the partial discharge generation position) in the case where the averaging process is not performed and the case where the averaging process is performed, and the measurement is performed under the following conditions. The results are shown.

That is, the slits S1, S2, S3 are provided at three locations on the 22 kV CV cable, and the slits S1-
The length between S2 and S1-S3 is 50m and 1 respectively.
It was set to 00m. A pair of foil electrodes are attached to the slits S1 and S2 so as to sandwich the sheath insulating portion, and two foil electrodes are attached.
Connected to the sensing impedance via a 0 cm covered wire,
A coaxial cable with a length equal to the measurement line from the detection impedance to the phase gate 43 was used.

In the slit S2, a needle stick defect is formed on the outer conductor of the cable so that partial discharge is generated.
The set phase of the phase gate was set to −45 ° to 90 °, and only partial discharge of rising positive electrode was selected. Then, a voltage of 42 kV was applied to the 22 kV cable, a partial discharge was generated and the position was located, and the results shown in FIG. 7 were obtained.

As is apparent from FIG. 7, the average value of the position location results when the averaging process is not performed is 54.2 m, whereas the average value of the position location results when the averaging process is performed is 5 m.
It is 0.9 m, and the slit S is better when averaged.
A result close to 50 m from the slit 1 to the slit S2 was obtained. (3) Third Embodiment FIG. 8 is a diagram showing a second embodiment in which the present invention is applied to an actual line. In the embodiment shown in FIG. 5, injection of a simulated pulse is performed in the vicinity of an insulation connection portion. However, in the present embodiment, a pulse generator is provided in the measurement chamber 30, and the simulated pulse is sent to the insulated connection via the optical fiber 27 '.

In the figure, the same parts as those shown in FIG. 5 are designated by the same reference numerals, and in the figure,
In the embodiment of FIG. 5, an operating unit 41 for performing an operation for sending a simulated pulse to an insulating connection, a pulse generator 42 for generating a simulated pulse, and an amplifier 4 for amplifying the output of the pulse generator 42.
3. A changeover switch 44 for selectively outputting the output of the amplifier 43 is provided. In addition, the optical fiber 27 '
In order to enable the signal to be transmitted bidirectionally as a core, the amplifier 25, the electro-optical converter 26, and the photoelectric converter 31 shown in FIG. 25 ', electro-optical converter /
Opto-electric converter 26 ', electro-optical converter / opto-electric converter 3
Instead of 1 ′, a switch was provided in series with the detection impedance 24, and when the simulated pulse was injected, the switch was opened, and the simulated pulse was applied between the foil electrodes 23 and injected into the cable. It is a thing.

In the figure, in order to inject the simulated pulse, the insulating connection to which the simulated pulse is injected is selected, and the output of the amplifier 43 is switched by the changeover switch 44 to the corresponding electro-optical converter / photo-electric converter 31. 'Connect to. At this time, the changeover switch 32 of the line into which the simulation pulse is injected is kept open. Next, the operation unit 41 is operated to operate the pulse generator 4
A simulated pulse is generated from 2, and the amplifier 43 → changeover switch 44 → electro-optical converter / photo-electric converter 31 '→ optical fiber 27' → electro-optical converter / photo-electric converter 26 '→ amplifier 25' It is applied to the foil electrode 23 of the insulating connection portion. At this time, a control signal is sent from the changeover switch 44 to the insulating connection portion, and the switch provided on the detection impedance 23 'is opened.

As a result, a simulated pulse is injected into the cable 1, the injected simulated pulse is detected at another insulating connection, and is sent to the measurement chamber 30 by a route opposite to the above.
The times t ₁ and t ₂ described above are obtained by the oscilloscope 36. The processing device 37 determines and stores the difference K between the propagation time t of the pulse between the insulated connecting portions and the delay time of the measuring device from the determined times t ₁ and t ₂ , as in the first embodiment.

Next, when a partial discharge occurs, the partial discharge pulse is transmitted to the measurement chamber 30 and the arrival time difference Δt of the partial discharge pulse is obtained by the oscilloscope 36, as in the embodiment shown in FIG. The obtained arrival time difference Δt is
Provided to the processor 38 via the interface 37,
The location of the occurrence of the partial discharge is determined based on the propagation time t of the pulse between the insulated connecting portions, the difference K between the delay times of the measuring devices, and the measured Δt.

For example, in the principle diagram of FIG. 1, the transmission delay between the C joint and the A joint is t _AC , the transmission delay between the B joint and the D joint is t _BD , and the transmission delay between the C joint and the measurement point. Let t _{c be} the delay of the measurement system and t _D be the delay of the measurement system between the D joint and the measurement point.
Inject a simulated pulse from the measuring unit V3 to the C joint, and
When the simulated pulse is detected by the joint and the A joint, the arrival time difference t ₁ of the simulated pulse at the measurement location is expressed by the following equation (9).

T ₁ = t _C + t _AC + t + t _B −t _C −t _AC −t _A = t + t _B −t _A (9) In addition, a simulated pulse is injected from the measurement unit V4 to the D joint, and the B joint and the A joint. When the simulated pulse is detected at, the arrival time difference t ₂ of the simulated pulse at the measurement location is expressed by the following equation (10).

T ₂ = t _D + t _BD + t + t _A −t _D −t _BD −t _B = t + t _A −t _B (10) The above equations (9) and (10) are the same as the above equations (1) and (2). Since it is the same, as described above, the difference K between the pulse propagation time t between the insulated connections and the delay time of the measuring device can be obtained, and when partial discharge occurs, at joint A and joint B The location of occurrence of partial discharge can be determined by the detected partial discharge pulse.

As described above, if the connection portion for injecting the simulated pulse and the connection portion for measuring the partial discharge are different,
It is possible to cancel the transmission delay between the insulating connection portions on the injection side of the simulated pulse and the delay of the measurement system, and it is possible to obtain the same effect as that of injecting the simulated pulse directly from the insulating connection portion. In the above embodiment, the processing device 38
Automatically injects a simulated pulse at each measurement point
When the partial discharge is generated, it is possible to automatically locate the partial discharge occurrence point based on the obtained time Δt and the above t and K.

In the above embodiment, a foil electrode is provided at the insulated connecting portion to detect a partial discharge pulse and to inject a simulated pulse. By attaching the foil electrode 23 thereto and detecting the partial discharge pulse or injecting the simulation pulse, the position where the partial discharge occurs can be located with higher accuracy. In this case, the outer semiconductive layer may be left as it is, and a slit may be formed only in the metal portion for measurement.

Further, also in this embodiment, the gate circuit (or the absolute value circuit) and the averaging processing circuit shown in FIG. 6 can be provided to improve the measurement accuracy.

[0057]

As described above, according to the present invention, the simulated pulse is sequentially injected in advance from at least two end connection parts, intermediate connection parts or the sheaths of the cable to be measured, so that the cable The transmission delay of the partial discharge pulse in a predetermined section and the time delay of the measurement system are measured, and when the actual partial discharge occurs, the time difference between the actual partial discharge pulse signals obtained from at least two measured points and the simulated pulse. Since the actual partial discharge occurrence position is located based on the transmission delay obtained at the time of injection and the time delay of the measuring device, the following effects can be obtained. Since the time correction can be directly performed using an actual cable on site, the location of the partial discharge occurrence can be efficiently and highly accurately located. Since the time delay of the measurement line and the measuring device can be corrected at the same time, it is possible to locate the partial discharge occurrence location with high accuracy. By making it possible to inject the simulated pulse from the measurement room, it is not necessary to go to the cable laying site to inject the simulated pulse, and efficient work can be performed. Simulated pulse injection means are provided at least at two or more locations, and a manual pulse is injected from each simulated pulse injection means with a predetermined time difference by a timer between a terminal connection portion, an intermediate connection portion, or a conductor sheath of a cable, thereby requiring labor. A simulated pulse can be injected without any need, and efficient measurement can be performed. A gate circuit or an absolute value circuit that passes only a signal of a predetermined specified phase among the applied potential phases and an averaging processing circuit that averages the signals that have passed through the gate circuit are provided. By averaging the partial discharge pulse signals that have passed through the circuit, it is possible to locate the partial discharge generation position with high accuracy.

[Brief description of the drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a diagram illustrating the principle of the present invention.

FIG. 3 is a diagram showing an example of a confirmation test for confirming the principle of the present invention.

FIG. 4 is a diagram showing a result of a confirmation test.

FIG. 5 is a diagram showing a first embodiment in which the present invention is applied to a real line.

FIG. 6 is a diagram showing an example of improving the location accuracy in the example of FIG.

FIG. 7 is a diagram showing measurement results of the example of FIG.

FIG. 8 is a diagram showing a second embodiment in which the present invention is applied to a real line.

[Explanation of symbols]

1 Power cable 2,22 Insulation connection part 3 Measurement part 3a Measurement part 3b, 4,5 5 Simulated pulse generator 6 Transmission line 12,23 Foil electrode 13,24,23 'Detecting impedance 11,36 Oscilloscope 21 Normal connection part 25, 33, 43 Amplifier 25 'Bidirectional amplifier 26 Electro-optical converter 26' Electro-optical converter / optical-electrical converter 27, 27 'Optical fiber 28, 28' Simulated pulse injection means 29, 29 'Receiver 30 Measurement room 31 Light Electric converter 31 'Electro-optical converter / optical-electrical converter 32,44 Changeover switch 34 Partial discharge measurement unit 37 Interface 35,38 Processing unit 39 Transmitter 41 Operation unit 42 Pulse generator 50 Phase gate 51 Averaging processing circuit

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Masaki Matsuki 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Toshiyuki Sato 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Inside Electric Industries Co., Ltd. (72) Inventor Hidetoshi Yasui 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Yoshio Maruyama 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Examiner in a corporation Nobuhiko Egashira (56) References JP-A-6-82512 (JP, A) JP-A-63-193077 (JP, A) JP-A-2-223871 (JP, A) 264869 (JP, A) JP-A-2-167484 (JP, A)

Claims (7)

(57) [Claims] 1. A partial discharge detector is attached to a terminal connection or each intermediate connection of a long power cable, and at least two of the terminal connection, each intermediate connection, or the cable.
In the partial discharge occurrence position locating method of the power cable for locating the partial discharge occurrence position by the arrival time difference of the partial discharge pulse signals detected at more than one place, in advance, at least two end connection parts, intermediate connection parts or cable Simulated pulses are sequentially injected from between the conductor sheaths, and the transmission delay of the partial discharge pulse and the time delay of the measurement system in a predetermined section of the cable are measured, and when an actual partial discharge occurs, from at least two measured points Locating a partial discharge occurrence position of a power cable based on a time difference between the obtained actual partial discharge pulse signal and a transmission delay and a time delay of a measurement system obtained during the injection of the simulated pulse. Method. 2. The method for locating a partial discharge occurrence position of a power cable according to claim 1, wherein the simulated pulse is injected from a foil electrode attached to the terminal connection portion or the intermediate connection portion. 3. The point where the actual partial discharge pulse and the simulated pulse are measured, and the point where the simulated pulse is injected are located away from the measured intermediate connection and the cable. Method for locating the partial discharge occurrence of power cables in Japan. 4. A simulated pulse injection means is provided at at least two or more locations, and a simulated pulse is injected from each simulated pulse injection means with a predetermined time difference by a timer between a terminal connection portion, an intermediate connection portion, or a conductor sheath of a cable. 4. The method for locating a partial discharge occurrence position of a power cable according to claim 1, 2, or 3. 5. The arrival of a partial discharge pulse detected by a partial discharge detector attached to a terminal connection portion or each intermediate connection portion of a long power cable and partial discharge detectors installed in at least two or more places. In a partial discharge occurrence position measuring device comprising a means for obtaining a time difference and a means for locating a partial discharge occurrence position from the arrival time difference, a simulation pulse is sequentially provided from at least two terminal connection portions, intermediate connection portions, or between the sheaths of the cable. The transmission delay of the partial discharge pulse in a predetermined section of the cable and the time of the measurement system from the arrival time difference between the simulated pulse generating means to be injected and the simulated pulse measuring points detected by at least two or more partial discharge detectors installed The means for measuring the delay and the partial discharge pulse detected by the partial discharge detector when the partial discharge occurs. Portion at which the partial discharge generation position is located based on the arrival time difference at the measurement point of the discharge voltage, the transmission delay of the partial discharge pulse obtained by injecting the simulated pulse, and the time delay of the measurement system. Discharge generation position measuring device. 6. A gate circuit for passing only a signal of a predetermined specified phase among the applied potential phases, and an averaging processing circuit for averaging the signals passed through the gate circuit are provided, and the gate circuit is passed through. 6. The partial discharge generation position measuring device according to claim 5, wherein the partial discharge pulse signals are averaged. 7. An absolute value circuit for outputting an absolute value of an input signal, and an averaging circuit for averaging the output of the absolute value circuit, wherein the partial discharge pulse signal is converted into an absolute value by the absolute value circuit. The partial discharge occurrence position measuring device according to claim 5, wherein the partial discharge pulse signal converted into the value is averaged.