JPH07229947A - Measurement of partial discharge and method for locating its generation point - Google Patents

Abstract

PURPOSE:To provide a method for measuring partial discharge by which partial discharge in an ordinary connecting part of a power cable can be detected accurately. CONSTITUTION:Discharge pulse detectors 4 and 4' are respectively provided in the insulation connecting parts 3 and 3' on both sides of an ordinary connecting part, 2. The output from the detectors 4 and 4' is inputted to a time-lag detection part A which discriminates whether or not a time difference is within a specified range and a level detection part B which discriminates whether or not the ratio of pulse size is within a specified range, and the discriminated outputs of both the detectors A and B are judged by a general judging part C so as to detect a partial discharge pulse. Thus, the discriminating capacity can be improved in comparison with a conventional measuring method for partial discharge in which the discharge pulse and noise are discriminated with the aid of the time difference between pulses.

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 of a normal connection portion of a power cable line and a method for locating a partial discharge generation position of a power cable by using the measuring method.

[0002]

2. Description of the Related Art When a partial discharge pulse generated in a power cable line connected by a straight connection such as a normal connection portion or an insulation connection portion passes through the insulation connection portion, the sheath insulation portion of the insulation connection portion A method has been used in which the phenomenon of generating a differential voltage between the metal sheaths on both sides is used to detect the differential voltage and measure the partial discharge of the insulating connection.

However, there is a problem that the partial discharge cannot be directly measured by this method because the connecting portion usually has no sheath insulating portion.

However, also with respect to this problem, as shown in FIG. 5, for example, the insulating connecting portions 3 and 3'on both sides of the ordinary connecting portion 2 are provided.
Of the partial discharge pulse propagating to the cable, and the time difference between the pulses detected at the insulation connection parts 3 and 3'on both sides is the cable 1 between the ordinary connection part 2 and the insulation connection parts 3 and 3'on both sides.
A method has been proposed in which only the pulse having a time difference corresponding to the propagation time difference due to the difference in 1 ′ length is used as the partial discharge generated in the normal connection portion 2, and it is possible to measure indirectly, though it is possible.

[0005]

However, the above-mentioned method of measuring the partial discharge of the ordinary connection portion causes the following problems in the power cable line having a lot of external noise.

That is, even when noise is randomly entered in the insulating connection portions on both sides, the time difference of the noise, which is originally another thing, as shown in FIG. 4, occurs when partial discharge occurs in the normal connection portion. Being equal to the time difference is a certain probability.

This probability can be reduced by precisely measuring the time difference between the pulses and setting the range of the time difference for determining that the pulse normally comes from the connecting portion to be very narrow and performing the determination.

However, it is not always easy to measure the pulse time difference in real time, and in reality,
The limit is about 1 microsecond.

Therefore, when there is a noise about once every several to several tens of microseconds, the probability that it is erroneously determined as a partial discharge pulse coming from the connection portion becomes a non-negligible magnitude and there is a problem. .

SUMMARY OF THE INVENTION An object of the present invention is to provide a partial discharge measuring method capable of discriminating a partial discharge of a normal connecting portion from noise with high accuracy.

[0011]

In order to solve the above problems, according to the present invention, a partial discharge measuring method for measuring a partial discharge of a normal connecting portion of a power cable line at an insulating connecting portion on both sides of the normal connecting portion. In the above, among the pulses detected at the insulating connection portions on both sides, only the pulse having the ratio of the time difference of the predetermined range and the magnitude of the predetermined range was determined as the partial discharge generated at the normal connection portion. Of.

At this time, a simulation pulse is injected between the metal shielding layer of the normal connection portion and the ground with the time difference and the size ratio for the above determination, and at that time, the pulse of the pulse detected at the insulating connection portions on both sides is injected. It can be calculated from the time difference and the size ratio.

Further, regarding the time difference and the size ratio for the above judgment, an electrode is provided on the anticorrosion layer of the ordinary connecting portion, and a simulated pulse is injected between the electrode and the ground, at that time, the insulating connecting portions on both sides. It can also be determined from the time difference and the ratio of the magnitudes of the pulses detected in.

Further, at this time, partial discharge in a certain section of the power cable line is detected by insulating connection portions provided at both ends of the section, and a value obtained by measuring a time difference and a size ratio of the partial discharge pulses, An electrode is provided on the cable anticorrosion layer in the section, a simulated pulse is injected between the electrode and the ground, and the time difference and the ratio of the simulated pulse detected at the insulating connection portions at both ends are compared with each other. Find the electrode position where the values match,
A method of locating the obtained electrode position as a partial discharge occurrence position can also be performed.

[0015]

In the partial discharge measuring method configured as above,
Measure the pulse size ratio along with the time difference between the pulses detected at the insulation connection parts on both sides of the normal connection part, and normally connect only the pulses whose measured time difference and size ratio fall within the preset range. It is determined that the pulse is a partial discharge pulse generated in a part.

As a result, the probability of erroneously deciding random noise as a partial discharge signal from a normal connecting portion can be greatly reduced, as compared with the conventional determination based on only the time difference.

At this time, in order to enhance the ability to discriminate between the noise and the partial discharge signal, it is effective to set the range of the time difference and the size ratio for determining the partial discharge signal from the normal connection portion as narrow as possible. Target.

However, if the setting is made narrow, it is important to confirm that the setting is appropriate, and if the setting is incorrect, the partial discharge generated at the normal connection portion may be judged as noise. is there.

For this reason, a simulation pulse is injected between the metal shield layer of the ordinary connection portion and the ground with the time difference and the size ratio for the above determination, and at that time, the time difference between the pulses detected at both insulating connection portions and In the method of finding from the size ratio,
A simulated pulse is injected between the metal shield layer of the normal connection part and the ground, and the injected pulse is measured at the insulation connection part by the same method as the actual measurement, and the measured pulse is judged to be a partial discharge pulse. By judging whether the above settings are appropriate depending on whether it is possible,
Find a reasonable time difference and size ratio.

By the way, the method of injecting the simulated pulse between the metal shield layer of the ordinary connection portion and the ground has been proposed in the past as a method of calibrating the partial discharge of the ordinary connection portion, but it is not suitable as the calibration method. Was not used.

This is because the partial discharge pulse is injected by 100% between the center conductor and the metal shield layer, whereas when the pulse is injected between the metal shield layer and the ground, a part of the injected pulse current is , It is difficult to accurately determine the ratio of the divided current between the center conductor and the metal shield layer, and the rest between the metal shield layer and the ground, and it is difficult to determine the ratio between the target center conductor and the metal shield layer. The reason is that it is impossible to reach the purpose of calibration in which the size itself is a problem because it is not known whether or not only a pulse current is injected.

However, in the present invention, since the time difference and magnitude ratio of the pulses reaching the insulating connection portions on both sides is required, and it is not necessary to know the magnitude of the injected pulse current itself, this method is used. It is valid.

At this time, the time difference and the size ratio for the above determination are detected at both insulating connection parts by providing an electrode on the anticorrosion layer of the normal connection part and injecting a simulated pulse between the electrode and the ground. In the method of determining the time difference and magnitude ratio of the pulse, instead of directly injecting the simulated pulse between the metal sheath of the normal connection part and the ground, an electrode is provided on the anticorrosion layer of the normal connection part, and this electrode and the ground are connected. By injecting a simulated pulse into the, the simulated pulse is indirectly injected through the capacitance formed between the metal shield layer of the normal connection part and the electrode, and the simulated pulse is judged to be a partial discharge pulse. Whether or not the above setting is appropriate is determined depending on whether or not it is performed.

Further, an electrode is provided on the cable anticorrosion layer, a simulated pulse is injected between the electrode and the ground, and the partial discharge of the cable section is determined from the time difference and the ratio of the simulated pulse detected at the insulation connection portions at both ends of the section. In the method of locating, the method of injecting the simulated pulse with the electrode provided on the anticorrosion layer can be applied to the cable part as well, and the electrode provided on the cable anticorrosion layer is moved, and the electrode and ground By injecting the simulated pulse into the cable and finding the electrode position where the time difference and the size ratio of the simulated pulse detected at the insulation parts at both ends are the same as the time difference and the size ratio of the pulse during partial discharge, Locate the partial discharge position of.

[0025]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a power cable 1 as a first embodiment.
1 shows a partial discharge measuring device for discriminating partial discharge and noise of a normal connecting portion 2 of a 1'line from a time difference and a ratio of magnitudes of pulses detected at insulating connecting portions 3 and 3'on both sides of the normal connecting portion 2. .

The partial discharge measuring device comprises discharge pulse detectors 4 and 4 ', a time lag detecting section A, a level detecting section B, and a comprehensive judging section C.

The discharge pulse detectors 4 and 4'are attached to the insulating connection parts 3 and 3'provided on both sides of the ordinary connection part 2 respectively, and detect the discharge pulse propagating through the power cables 1 and 1 '. The signal is sent to the time lag detector A and the level detector B via the optical fiber cables 5 and 5 '.

The time lag detecting section A is composed of pulse rising detecting sections 6 and 6'and a time difference determining section 7.

The pulse rise detectors 6 and 6'are provided for each of the discharge pulse detectors 4 and 4 ', and recognize the arrival time of the pulse sent from the discharge pulse detectors 4 and 4'.
The time difference determination unit 7 is notified of the time.

The time difference determination unit 7 measures the time difference between the pulses sent from both the pulse rise detection units 6 and 6 ', and if the time difference is within a predetermined range, validates the pulse and makes a comprehensive determination. Send to Part C.

The level detecting section B includes a pulse wave height detecting section 8,
8'and a size determination unit 9.

The pulse wave height detectors 8 and 8'are provided for the discharge pulse detectors 4 and 4 ', respectively.
The magnitude of the pulse sent from 4'is recognized, and the result is sent to the magnitude judging unit 9.

The magnitude judging section 9 compares the outputs from both the pulse wave height detecting sections 8 and 8 ', validates the pulse if the ratio is within a predetermined range, and sends it to the comprehensive judging section C. .

Based on the results sent from the time difference determination unit A and the size determination unit B, the comprehensive determination unit C determines that only the pulses that both determination units A and B are valid are the partial discharge of the normal connection unit 2. judge.

In an actual system, the comprehensive judgment section C can have various forms. For example, the comprehensive determination unit C
The reliability of the judgment is not limited to the final judgment of partial discharge only by the ratio of the time difference and the magnitude of the pulse, but also the pattern recognition judgment such as the relationship between the phase of the commercial frequency and the pulse detection phase and the pulse duration. It is conceivable to combine the function of increasing the frequency, the function of issuing an alarm based on the judgment result, and the function of displaying the judgment result and the original waveform.

Further, in the operation of this apparatus, it is necessary to define a range in which it is determined that the pulse arrival time difference and the size ratio are effective. As a means to do this, it is desirable to determine each connection part by on-site measurement, but if a slight decrease in accuracy is allowed, it can be calculated from the surge propagation characteristics of the power cables 1, 1'measured in advance. It is possible to ask.

For example, the arrival time difference is that the power cables 1 from the ordinary connection portion 2 to the insulated connection portions 3 and 3'on both sides are
It can be calculated by multiplying the difference in 1'length by the surge propagation speed.

Needless to say, when there is a difference in length between the optical fiber cables 5 and 5 ', the time difference due to this must be calculated and included in the same manner.

Here, since the surge propagation speed is a constant with a relatively small variation, the decrease in accuracy due to the use of the numerical value obtained by the calculation is relatively small.

On the other hand, the pulse size ratio can be similarly obtained by multiplying the difference in length of the power cables 1, 1'by the surge attenuation factor. The variation of the attenuation rate is quite large, and it is necessary to keep a wide range in which it is determined to be effective in consideration of it.

This embodiment is constructed as described above, and the partial discharge measuring method will be explained by describing the operation of the apparatus.

In such a power cable 1, 1 ', a discharge pulse propagating through the power cable 1, 1'is detected by the discharge pulse detectors of the insulated connections 3, 3', and now the normal connection 2 When a partial discharge occurs, the discharge pulse propagates through the power cables 1, 1 ′ on both sides of the normal connection part 2 and discharges the insulated connection parts 3, 3 ′ connected to the respective power cables 1, 1 ′. It is detected by the pulse detectors 4, 4 '.

The discharge pulse detectors 4 and 4'detect the discharge pulse by the optical fiber cables 5 and 5 '.
It is transmitted to the time lag detector A and the level detector B.

In the time lag detecting section A, the arrival time of the pulse signal inputted from each of the discharge pulse detectors 4 and 4'is recognized by each pulse rising detecting section 6 and 6 ', and the time is sent to the time difference determining section 7. Tell. The time difference determination unit 7 measures the time of both pulses, and the time difference is a preset time difference, that is, the difference between the lengths of the power cables 1 and 1'from the normal connection unit 2 to the insulated connection units 3 and 3'on both sides. Within the range of the time difference caused by the difference in the lengths of the optical fiber cables 5 and 5'from the discharge pulse detectors 4 and 4'of the insulation connection portions 3 and 3'to the pulse rise detectors 4 and 4'of the time lag detection portion A. If so, the pulse is validated and sent to the comprehensive judgment unit C.

Further, in the level detecting section B, the magnitude of the pulse signal inputted from each of the discharge pulse detectors 4 and 4'is recognized by the pulse wave height detecting sections 8 and 8 ', and the magnitude is judged by the magnitude judging section. If the ratio of the magnitudes is within a predetermined range, that is, the range of the ratio of the attenuation rate due to the difference in the lengths of the power cables 1 and 1 ', the pulse is considered to be valid and the overall determination unit is detected. Send to C.

In the comprehensive judgment section C, the partial discharge is measured by regarding only the pulses validated by the time lag detection section A and the level detection section B as the partial discharge pulses in the normal connection section 2.

At this time, for example, in the insulating connection portions 3 and 3 ',
When the pulsed noise is randomly induced, the comprehensive determination unit C is examining the ratio between the pulse detection time difference and the size, and the pulse noise time difference is within the set time range as shown in FIG. Even if the time lag detecting unit A recognizes that the pulse height detectors 8 and 8 ′ have the same peak value as the power cable 1 and 1 ′ and the optical fiber cables 5 and 5 ′. The probability that pulsed noise with a rate is generated is low, and therefore the probability that the level detection unit B recognizes noise as effective is low.

Therefore, the present apparatus can correctly distinguish the discharge pulse and the noise.

By the way, in order to enhance the ability to discriminate between the noise and the partial discharge signal, it is necessary to set the range of the time difference and the size ratio for determining the partial discharge pulse from the normal connection portion 2 as narrow as possible. Is.

However, in the case where the setting is narrow, it is important to confirm that the setting is appropriate, and if the setting is incorrect, the partial discharge generated in the normal connection portion 2 is judged as noise. There is a risk that

Therefore, as a second embodiment, FIG. 2 shows a measuring device for confirming the validity.

This measuring device is the partial discharge measuring device of the first embodiment provided with a simulated pulse generator.

That is, the normal connecting portion comprises a conductor sleeve 10, an insulator 11 for reinforcing the sleeve 10 and a metal shielding layer (metal sheath) 12 for covering the insulator 11, as shown in FIG. An anticorrosion layer 13 is provided on the surface of the metal shielding layer 12. In addition, the metal shielding layer 1
2 is provided with a ground terminal 14 for shielding, and the simulated pulse generator 15 is connected between the metal shield layer 12 and the ground to inject a simulated pulse. The arrival time difference and the size ratio of the pulses detected by the discharge pulse detectors 4 and 4'installed at 3'are measured by the same method as in the first embodiment.

At this time, if the setting is appropriate, this pulse should be judged as valid by both the time difference judgment section 7 and the size judgment section 9, and the comprehensive judgment section C should recognize it as a partial discharge.

If it is not determined to be effective, the setting of the effective range of the arrival time difference and the size ratio is changed and the same operation is repeated so that the injected simulated pulse is recognized as a partial discharge. You can ask for the correct settings.

If a function for measuring and displaying the arrival time difference and the size ratio is added to the time difference determination unit 7 and the size determination unit 9, it is possible to directly set a desired set value from the measurement result. Therefore, more efficient settings can be made.

As a method of injecting the simulated pulse between the metal sheath 12 of the ordinary connecting portion 2 and the ground, the ground wire of the ordinary connecting portion 2 is removed and the simulated pulse generator 15 is connected between the ground terminal 14 and the ground. Although it is ideal to do so, if you do not want to remove the ground wire, insert a split type magnetic core in the ground wire and connect the simulated pulse generator 14 to the secondary winding wound around the core. Injection is also possible by this.

Next, as a third embodiment, an electrode 16 is provided on the anticorrosion layer 13 of the ordinary connection portion 2 instead of injecting a simulated pulse between the metal sheath 12 of the ordinary connection portion 2 and the ground in the second embodiment. A method of injecting a simulated pulse will be described.

In this method, the simulated pulse is indirectly injected via the capacitance formed between the metal shield layer 12 of the normal connection portion 2 and the electrode 16 provided on the anticorrosion layer 13 shown in FIG. Therefore, as the electrode 16, for example, an aluminum foil of about 10 cm square is attached to the anticorrosion layer 13, and the purpose can be sufficiently achieved.

Therefore, the injection of the simulated pulse can be performed very easily without removing the ground wire of the normal connection portion 2 or using the magnetic core, which is very effective in examining the validity of the set value. is there.

The method of injecting the simulated pulse of the third embodiment by the electrode 16 provided on the anticorrosion layer 13 of the ordinary connection portion 2 is as follows.
It is also applicable to the power cables 1 and 1 '.

Therefore, as a fourth embodiment, a method of locating the occurrence position when a partial discharge occurs in the power cable 1, 1'part using the above method will be described.

In this method, an electrode 16 is provided on the anticorrosion layer 13 of the power cables 1 and 1'in the section where the orientation is performed, a simulated pulse is injected between the electrode 16 and the ground, and the insulating connection portions 3 at both ends of the section are provided. , 3 ', the electrode position where the ratio between the time difference and the magnitude of the simulated pulse and that of the partial discharge for which the generation position is desired to be located coincides is searched, and the position is set as the partial discharge generation position.

At this time, the electrode 16 may be small, as described in the third embodiment, and may be pressed against the anticorrosion layer 13, so that the electrode position can be easily found.

[0066]

According to the method of claims 1 to 3 of the present invention, when indirectly measuring the partial discharge of the ordinary connection portion, the noise and the partial discharge can be automatically discriminated from each other without relying on the judgment of a person. I can do it well. Therefore, it is effective for measurement in a noisy environment.

In particular, a method of connecting a simulated pulse generator between the metal shield layer of the ordinary connection portion and the ground of claim 2 and injecting a simulated pulse to confirm the validity of the difference in the arrival time of the pulses and the ratio of the magnitudes. Then, since it is possible to easily determine the correct setting value of the pulse arrival time difference and the magnitude ratio, it is possible to improve the accuracy of discrimination between the noise and the discharge pulse.

In this case, in the method of providing an electrode on the anticorrosion layer of the normal connection portion of claim 3 and injecting the simulated pulse by the electrode, the injection of the simulated pulse can be performed only by sticking the electrode on the anticorrosion layer. The validity of the set values can be measured very easily.

Further, in the method of injecting the simulated pulse of claim 4 by the electrode provided on the anticorrosion layer of the normal connection portion and locating the generation position when the partial discharge occurs in the cable portion,
If partial discharge measurement is performed using a device compatible with the above measurement method, even if a partial discharge occurs in the cable, the position where the partial discharge occurs can be located without adding a new device. it can.

[Brief description of drawings]

FIG. 1 is a block diagram of a first embodiment.

FIG. 2 is a block diagram of a second embodiment.

FIG. 3 is a schematic diagram showing a normal connection part.

FIG. 4 is an operation explanatory view for explaining a conventional problem.

FIG. 5 is a block diagram showing a conventional partial discharge measurement method.

[Explanation of symbols]

 1 Power cable 2 Normal connection part 3, 3'Insulation connection part 4, 4'Discharge pulse detector 5 Optical fiber cable 6, 6'Pulse rising detection part 7 Time difference judgment part 8, 8'Pulse height detection part 9 Size judgment Part 10 Conductor sleeve 11 Insulator 12 Metal shielding layer 13 Anticorrosion layer 14 Ground terminal 15 Simulated pulse generator 16 Electrode A Time lag detector B Level detector C Comprehensive judgment unit

Claims (4)

[Claims] 1. A partial discharge measuring method for measuring a partial discharge of an ordinary connection portion of a power cable line at an insulation connection portion on both sides of the normal connection portion, wherein a pulse detected at the insulation connection portion on both sides is: A partial discharge measuring method, characterized in that only a pulse having a ratio of a time difference of a predetermined range and a magnitude of a predetermined range is determined as a partial discharge generated at a normal connection portion. 2. A time difference between the time difference and the magnitude ratio for the above judgment is simulated by injecting a simulated pulse between the metal shield layer of the normal connection portion and the ground, and the time difference between the pulses detected at the insulating connection portions on both sides. 2. The partial discharge measuring method according to claim 1, wherein the partial discharge measuring method is obtained from a ratio of the size and the size. 3. A time difference and a size ratio for the above judgment are provided by providing an electrode on an anticorrosion layer of a normal connecting portion and injecting a simulated pulse between the electrode and the ground, at that time, insulating connecting portions on both sides. 2. The partial discharge measuring method according to claim 1, wherein the partial discharge measuring method is obtained from a time difference and a ratio of magnitudes of the pulses detected in. 4. A partial discharge in a certain section of the power cable line is detected by insulating connection portions provided at both ends of the section,
A value obtained by measuring the time difference and magnitude ratio of the partial discharge pulse, and providing an electrode on the cable anticorrosion layer in the section, injecting a simulated pulse between the electrode and the ground, and a simulation detected at the insulation connection parts at both ends. A method for locating a partial discharge occurrence position, in which a pulse time difference and a measured value of a ratio are compared with each other to find an electrode position where the two values are the same, and the obtained electrode position is a partial discharge occurrence position.