JP6959859B2 - Insulation deterioration diagnosis device and insulation deterioration location identification device - Google Patents

Description

The present invention relates to a device for diagnosing insulation deterioration of a power cable or an electric device (hereinafter referred to as "power cable, etc.") connected to a special high-voltage system or a high-voltage system, and performs partial discharge based on a discharge current flowing through a ground wire. The present invention relates to an insulation deterioration diagnostic device for detecting and an insulation deterioration location locating device for locating a location where a partial discharge is occurring.

Partial discharge is a local electrical discharge phenomenon that occurs partially in an insulator due to the local electric field of the insulator (gas, liquid, solid, vacuum) between conductors.
When a partial discharge occurs, the insulating material deteriorates due to ultraviolet rays, high-energy electrons / particles, gas with strong chemical activity, and the like. Due to the occurrence of partial discharge, deterioration of the gas / liquid / solid insulation system progresses, and then dielectric breakdown occurs. Therefore, partial discharge is a factor that determines the life of the insulating material.
In order to detect insulation deterioration of power cables, etc. at an early stage, a statistical method is used to extract all waveforms that exceed the threshold value, distinguish the waveforms by statistical processing, etc., and then determine the presence or absence of partial discharge due to the correlation with the phase voltage. It is being developed.
However, the partial discharge discrimination by the statistical method has the following disadvantages.
(1) Since there is a large amount of broadcast radio waves, radio noise, or system noise, the occurrence of partial discharge cannot be determined unless deterioration progresses and the quantity of partial discharge increases.
(2) Since the partial discharge waveform cannot be detected individually, it cannot be used for positioning the partial discharge.

Further, in Patent Document 1 (Japanese Unexamined Patent Publication No. 2011-237182), as shown in FIG. 8, a partial discharge attached to a ground wire (5) connected to a shielding layer on the outer periphery of the end of the cable (2). A partial discharge discriminator that detects the discharge current flowing through the ground wire (5) using the discriminator and its partial discharge discriminator, and discriminates whether or not a discharge current is generated due to insulation deterioration of the cable (2). The method is disclosed.
The partial discharge discriminator is a current transformer (7), a load resistor (13), a resistor (14), an amplifier (15), a bandpass filter (17), and noise removal that detect the current flowing through the ground wire (5). It includes a unit (19), a waveform storage unit (21), a feature amount derivation unit (23), and a discharge determination unit (25).
Then, the feature amount derivation unit (23) passes through the bandpass filter (17) and based on the waveform stored by the waveform storage unit (21), the magnitude of the amplitude, the direction of vibration, the peak pitch, the convergence time, etc. Derivation of features (see in particular paragraph 0031).
Further, in the discharge determination unit (25), the current signal detected within a predetermined time has a plurality of vibration waveforms based on the feature quantity derived by the feature quantity derivation unit (23), and the plurality of vibration waveforms. When it is judged that a plurality of waveforms having substantially the same size and opposite vibration directions are included in the waveform, it is judged that a partial discharge has occurred at the ground wire (5) which is the measured line (the ground wire (5) to be measured). In particular, see paragraph 0032).
According to the partial discharge discriminating device and the method disclosed in Patent Document 1, although the characteristics of the partial discharge can be grasped to some extent, it is not possible to specify where the insulation deteriorated portion exists, and the determination is made. The reliability was not so high.

Japanese Unexamined Patent Publication No. 2011-237182

The present invention is an insulation deterioration diagnostic device capable of diagnosing insulation deterioration of a power cable or the like in a live wire state without causing a power failure. The purpose is to improve and to be able to determine where the partial discharge is occurring in the power cable or the like.

The insulation deterioration diagnostic apparatus of the invention according to claim 1 is
A current detecting means for detecting a ground line current in a power cable or an electric device,
A feature amount extraction means for extracting a feature amount from current data based on a current detection value detected at regular time intervals by the current detection means, and a feature amount extraction means.
A partial discharge waveform determining means for determining the presence or absence of a partial discharge feature based on the feature amount extracted by the feature amount extracting means,
A noise detection means that detects noise with a magnitude greater than or equal to a predetermined threshold, and
Whether the time when the partial discharge waveform determining means determines that there is a characteristic of partial discharge is after the first duration elapses after the noise detecting means detects noise having a magnitude equal to or larger than a predetermined threshold value. Immediately before determining whether or not noise management means and
Whether or not the noise detecting means has detected noise having a magnitude equal to or greater than a predetermined threshold value from the time when the partial discharge waveform determining means determines that the partial discharge has a characteristic to the time when the second duration elapses. Subsequent noise management means to determine and
It is determined that the first duration has elapsed since the immediately preceding noise management means detected noise having a magnitude equal to or larger than a predetermined threshold value, and the subsequent noise management means has a characteristic of partial discharge. It is provided with a partial discharge generation determining means for determining that a partial discharge has occurred when it is determined that noise having a magnitude equal to or larger than a predetermined threshold value has not been detected between the time of the determination and the elapse of the second duration. It is characterized by that.

The invention according to claim 2 is the insulation deterioration diagnostic apparatus according to claim 1.
When the first wave of the partial discharge is falling, the feature amount extracting means extracts the magnitude of the falling current value, the required falling time, the magnitude of the rising current value, and the required rising time as the feature amount.
In the partial discharge waveform determining means, the magnitude of the falling current value is within a predetermined range, the required falling time is within the third duration, and the magnitude of the rising current value is the falling current value. When the conditions that the size is larger and the rise time is larger than the fall time and less than 3 times the fall time are satisfied, it is judged that the partial discharge is characteristic.
When the first wave of the partial discharge is rising, the feature amount extracting means extracts the magnitude of the rising current value, the required rising time, the magnitude of the falling current value, and the required falling time as the feature amount.
The partial discharge waveform determining means means that the magnitude of the rising current value is within a predetermined range, the required rising time is within a predetermined time, the magnitude of the falling current value is larger than the magnitude of the rising current value, and When the condition that the required fall time is larger than the required rise time and less than three times the required rise time is satisfied, it is determined that the partial discharge is characteristic.

The insulation deterioration diagnostic apparatus of the invention according to claim 3 is
The insulation deterioration diagnostic apparatus according to claim 1 or 2 is installed in each phase of the three-phase power cable.
When the partial discharge generation determination means of any phase determines that a partial discharge has occurred, the recording of the current data and time information of each phase in the one-cycle memory is stopped, and the recording of each phase at the time of the stop is stopped. A partial discharge analysis means for receiving the information of the one-cycle memory is provided.
The partial discharge analysis means
Current peak polarity detecting means for detecting the polarity of the current peak of the waveform determined by the feature amount extracting means and the partial discharge waveform determining means based on the received current data and time information of each phase. In two phases other than the current peak value detecting means for detecting the absolute value of the current peak, the current peak time detecting means for detecting the time of the current peak, and the phase determined to have the characteristic of partial discharge. The other-phase current polarity detecting means for detecting the polarity of the current data at the time of the current peak, the other-phase current value detecting means for detecting the absolute value of the current data at the time of the current peak, and the other-phase current value detecting means.
The polarity detected by the current peak polarity detecting means and the polarity detected by the other-phase current polarity detecting means are opposite polarities, and the absolute value detected by the current peak value detecting means and the other-phase current value. It is characterized by having a partial discharge generation range determining means for determining a partial discharge in a cross-bond connection when the difference from twice the absolute value detected by the detecting means is equal to or less than the determination value.

The insulation deterioration location locating device of the invention according to claim 4 is
One end side slave station is provided on one end side of the power cable or the electric device, and the other end side slave station is provided on the other end side of the power cable or the electric device.
One end of the slave station is one end when it is determined that a partial discharge has occurred by the one end side insulation deterioration diagnosis device and the one end side insulation deterioration diagnosis device having the same configuration as the insulation deterioration diagnosis device according to claim 1 or 2. A one-sided transmission means for transmitting side partial discharge information to the master station is provided.
It was determined that the other end side slave station was partially discharged by the other end side insulation deterioration diagnosis device and the other end side insulation deterioration diagnosis device having the same configuration as the insulation deterioration diagnosis device according to claim 1 or 2. At the time, the other end side transmitting means for transmitting the other end side partial discharge information to the master station is provided.
The master station calculates the position of the insulation deterioration location based on the length and current propagation speed of the electric wire of the power cable or the electric device, and the received one-side partial discharge information and the other-end partial discharge information. Means and
It is characterized by including a display means for displaying the position information of the insulation deterioration location based on the calculation result by the insulation deterioration position calculation means.

According to the insulation deterioration diagnosis device of the invention according to claim 1, since the insulation deterioration of the power cable can be diagnosed in the live line state without causing a power failure, the deterioration state of the power cable or the electric device can be constantly monitored. It is possible.
In addition, since it is determined that a partial discharge has occurred only when a current waveform that may cause a partial discharge is detected during a time period when no large noise is detected, the reliability of the partial discharge generation determination can be improved and the reliability of the partial discharge generation determination can be improved at an early stage. It can be found that the power cable or electrical equipment is in a deteriorated state.

According to the insulation deterioration diagnostic apparatus of the invention of claim 2, in addition to the effect of the invention of claim 1, when the first wave of partial current is falling, the discharge waveform (sin curve 1 cycle approximate waveform) The characteristics, the magnitude of the fall current value, the required fall time, the magnitude of the rise current value, and the required rise time are extracted as feature quantities, and the magnitude of the fall current value is within a predetermined range. The condition that the required downlink time is within the specified time, the magnitude of the rising current value is larger than the magnitude of the falling current value, and the required rising time is larger than the required downlink time and less than 3 times the required downlink time. When the above is satisfied, it is determined that the partial discharge has a characteristic, and when the first wave of the partial discharge rises, the magnitude of the rising current value and the rising, which are the characteristics of the discharge waveform (sin curve 1 cycle approximate waveform), are found. The required time, the magnitude of the falling current value, and the required falling time are extracted as feature quantities, and the magnitude of the rising current value is within a predetermined range, the required rising time is within a predetermined time, and the falling current. When the condition that the magnitude of the value is larger than the magnitude of the rising current value and the required falling time is larger than the required rising time and less than 3 times the required rising time is satisfied, it is determined that the partial discharge is characteristic. Therefore, it is possible to accurately determine the presence or absence of the characteristic of partial discharge.

According to the insulation deterioration location diagnostic device of the invention according to claim 3, the insulation deterioration diagnosis device according to claim 1 or 2 is installed in each phase of the three-phase power cable of the cross-bond grounding method.
When the partial discharge generation determination means of any phase determines that a partial discharge has occurred, the recording of the current data and time information of each phase in the one-cycle memory is stopped, and the recording of each phase at the time of the stop is stopped. A partial discharge analysis means for receiving the information of the one-cycle memory is provided.
The partial discharge analysis means is
Based on the received current data and time information of each phase, the current peak polarity detecting means for detecting the polarity of the current peak of the waveform determined by the feature amount extracting means and the partial discharge waveform determining means to have the characteristic of the partial discharge, and the current peak polarity detecting means. At the time of the current peak, in two phases other than the current peak value detecting means for detecting the absolute value of the current peak, the current peak time detecting means for detecting the time of the current peak, and the phase determined to have the characteristic of partial discharge. The other-phase current polarity detecting means for detecting the polarity of the current data, the other-phase current value detecting means for detecting the absolute value of the current data at the time of the current peak, and the other-phase current value detecting means.
The polarity detected by the current peak polarity detecting means and the polarity detected by the other-phase current polarity detecting means are opposite, and the absolute value detected by the current peak value detecting means and the other-phase current value detecting means detect the polarity. Since it has a partial discharge generation range determining means for determining that it is a partial discharge in the cross-bond connection when the difference from twice the absolute value obtained is less than or equal to the determination value.
It is possible to determine whether or not the partial discharge detected by the insulation deterioration diagnostic apparatus according to claim 1 or 2 is a partial discharge in the cross-bond connection.

According to the insulation deterioration location locating device of the invention according to claim 4, one end side slave station and the other end side slave station are provided at both ends of the power cable or the electric device, and one end side partial discharge information and the other end side partial discharge information are provided. It is transmitted to the master station, and the master station is based on the length (equivalent length) and current propagation speed of the power cable or the electric wire of the electric device, and the received one-side partial discharge information and the other-side partial discharge information. Since the position of the insulation deterioration location can be calculated and displayed, it is possible to determine and notify where in the power cable the insulation deterioration occurs in the live wire state without causing a power failure.
Therefore, the state of insulation deterioration of the power cable can be constantly monitored, and information on the replacement or repair of the power cable can be obtained at any time.

The schematic diagram of the insulation deterioration diagnostic apparatus of Example 1. FIG. The graph which shows a part of the current data recorded in 1 cycle memory 41. A flowchart for determining the occurrence of partial discharge. Explanatory drawing of the cross bond grounding system in a three-phase power cable. The graph which shows a part of each phase current data with partial discharge in a cross-bond grounding type power cable. The schematic diagram of the insulation deterioration part locating apparatus of Example 3. FIG. The flowchart which shows the processing procedure of insulation deterioration position calculation means 28. The block diagram which shows the structure of the partial discharge discriminating apparatus described in Patent Document 1. FIG.

Hereinafter, embodiments of the present invention will be described with reference to examples.

As the outline of the insulation deterioration diagnostic apparatus of the first embodiment is shown in FIG. 1, a current measuring means such as a high frequency CT is attached to the ground wire 3 of the cable head 2 at the end of the power cable 1.
The current detecting means 4 A / D-converts the current signal obtained by the current measuring means by A / D conversion by sampling of 150 MHz or more to obtain current data after performing bandpass filtering of 100 kHz to 20 MHz for each of the three phases and amplifying the signal. obtain.
Then, for detailed processing when the partial discharge is detected, the current data for one cycle of the commercial frequency is cyclically recorded in the one-cycle memory 41 together with the time information obtained from the time measuring means 5.
Further, in a normal partial discharge analysis means, in order to remove noise in a low frequency band, the current data is subjected to 2 MHz high-pass filter processing to obtain current data for processing.
On the other hand, in the low-frequency partial discharge analysis means using a low-frequency component that has little attenuation and can detect a remote location, the current data is subjected to a low-pass filter process of about 1 MHz to obtain low-frequency current data.
The feature amount extracting means 6 and the noise detecting means 7 are connected to the current detecting means 4, and the partial discharge waveform determining means 8 is connected to the feature amount extracting means 6, and the feature amount extracting means 6 extracts the features. Based on the features, the current waveform that may be partially discharged is detected.
The time measuring means 5 transmits time information to the current detecting means 4, the immediately preceding noise management means 9, and the succeeding noise management means 10, but may be a clock that outputs a time conforming to the so-called standard time, or a reference clock. It may be a counter that can be reset in synchronization with a reference time point specified by the means and counts up or down during a certain period of time.
When the time measuring means 5 is a clock, the time information based on the standard time becomes the time information, and when the time measuring means 5 is a counter, the count value becomes the time information.

In the immediately preceding noise management means 9, the noise detecting means 7 has, for example, 0.01 A or more or −0.01 A or less (hereinafter, referred to as “predetermined threshold value or more”), a large noise (waveform determined not to be a partial discharge). (Including) is detected, a count value equivalent to 2 μs is set in the immediately preceding noise counter (not shown), and the count is counted down each time A / D conversion is performed.
That is, if 2 μs has passed since the detection of large noise and the immediately preceding noise counter becomes 0, it can be confirmed that there is no immediately preceding noise.
The time until the immediately preceding noise counter becomes 0 does not have to be limited to 2 μs, and the immediately preceding noise management means 9 determines whether or not the first duration has elapsed after detecting a large noise. It shall be. (Usually, it is selected in the range of 1 to 3 μs, which is several times the duration of partial discharge.)
When the partial discharge waveform determining means 8 detects a current waveform that may be partially discharged, the subsequent noise management means 10 sets a count value equivalent to 2 μs in the subsequent noise counter and counts down each time A / D conversion is performed. .. Then, if the subsequent noise counter is 0 or less (end state), it can be confirmed that there is no subsequent noise. (Actually, the subsequent noise counter waits for the time when the partial discharge may still continue, and starts monitoring after a certain time (for example, 1 μs) has passed since the count value was set. After that, monitor until 1 μs elapses.)
That is, if 2 μs elapses after detecting the current waveform that may be partially discharged and the succeeding noise counter is in the terminated state, it can be confirmed that there is no succeeding noise (in the case of partial discharge, a single shot). However, in the case of noise, the signal is continuous, so if there is no subsequent noise, it is judged that there is a possibility of partial discharge).
The time until the subsequent noise counter becomes 0 is not limited to 2 μs, and the subsequent noise management means 10 detects a current waveform that may be partially discharged until the second duration elapses. In addition, it is determined whether or not a large noise is detected. (In the case of a high frequency band of 3 MHz to 20 MHz, it is usually selected in the range of 1 to 3 μs.)
Then, the partial discharge generation determination means 11 determines that the first duration has elapsed since the immediately preceding noise management means 9 detected a large noise, and the subsequent noise management means 10 is capable of partial discharge. It is determined that a partial discharge has occurred when it is determined that no large noise is detected between the detection of the characteristic current waveform and the elapse of the second duration.

Next, the feature amount extracting means 6 and the partial discharge waveform determining means 8 will be described in detail.
FIG. 2 is a graph showing a part of the current data recorded in the one-cycle memory 41, and is an example of a waveform having a characteristic of partial discharge when the first wave of partial discharge falls.
The feature amount extracting means 6 extracts the magnitude of the falling current value (| Idown |), the required falling time (Tdown), the magnitude of the rising current value (Iup), and the required rising time (Tup) as feature quantities. ..
The noise level fluctuation in the portion surrounded by the dotted line in FIG. 2 is excluded.
Then, the partial discharge waveform determining means 8 determines that the current data has a possibility of partial discharge when the four feature quantities extracted by the feature quantity extracting means 6 satisfy the following four conditions.
(1) The magnitude of the falling current value is within the predetermined range (Ia << | Idown | <Iupper)
(2) Time required for falling down is within a predetermined time (Tdown <Ta)
(3) The magnitude of the rising current value is larger than the magnitude of the falling current value (Iup> | Idown |)
(4) The rise time is larger than the fall time and less than 3 times the fall time (Tdown <Tup <Tdown x 3).
However, when the first wave of partial discharge is rising, the relationship between falling and rising is reversed, and Ia <Iup <Iupper, Tup <Ta, | Idown |> Iup, Tup <Tdown <Tup × 3 4 It becomes a condition.
Similarly, for low-frequency current data, feature quantity extraction and determination of whether or not the waveform has a possibility of partial discharge are performed.
The value of Ia is set to be larger than the circuit noise level in order to make the sensitivity as high as possible, the value of Iupper is about 500 to 1000 mA, and the value of Ta is 3 to 13 MHz in the case of current data recorded in the 1-cycle memory 41. It is about 0.02 to 0.1 μs (in the case of low frequency current data, about 0.3 to 3 μs of 100 kHz to 1 MHz).

FIG. 3 is a flowchart for determining the occurrence of partial discharge.
These processes are continuously performed for each of the U phase, the V phase, and the W phase, but only one phase will be described.
Further, if it is determined that a partial discharge has occurred, the recording in the 1-cycle memory 41 is stopped when the time obtained by subtracting the second duration from the commercial frequency 1 cycle elapses.
The partial discharge analysis means detects a waveform having the characteristics of partial discharge from the current data recorded in the one-cycle memory 41 using the same extraction means as the feature amount extraction means 6, and transmits the commercial frequency 1. For the current data for the cycle, all the waveforms determined to have the above-mentioned partial discharge characteristics are detected.
Then, the partial discharge analysis means sends a command to restart the detection after the detection process is completed.
In the following, each step of the flowchart shown in FIG. 3 will be described by taking the case where the first wave of partial discharge falls as an example.

ST1: Initialization process, that is, a process of clearing the one-cycle memory 41, resetting the immediately preceding noise counter and the succeeding noise counter, and lowering a flag indicating that the succeeding noise counter is being set.
ST2: Current data acquisition processing, that is, the current signal is subjected to 100 kHz to 20 MHz bandpass filter processing by the current detecting means 4, and the amplified signal is A / D converted by sampling at 150 MHz or more to obtain current data. Later, in order to remove noise in the low frequency band, the current data is subjected to 2 MHz high-pass filter processing to obtain current data for processing.
ST3: Feature extraction process, that is, the magnitude of the falling current value (| Idown |), the required time required for falling (Tdown), the magnitude of the rising current value (Iup), and the magnitude of the rising current value (Iup) from the current waveform by the feature amount extracting means 6. A process to extract the rise time (Tup). Further, the same extraction processing is performed on the low frequency data subjected to the 1MHz low-pass filter processing.
ST4: The feature amount determination process, that is, whether or not a noise waveform having a magnitude equal to or larger than a predetermined threshold value is detected by the noise detecting means 7, and four extracted by the partial discharge waveform determining means 8. Based on the feature amount, it is determined whether or not it is a partial discharge waveform, and if a noise waveform is detected, the process proceeds to ST5, if it is a partial discharge waveform, the process proceeds to ST6, and both the noise waveform and the partial discharge waveform must be determined. If so, proceed to ST7.
ST5: Immediate noise counter set processing, that is, a process of setting a count value equivalent to 2 μs in the immediately preceding noise counter and returning to ST2 (current data acquisition).

ST6: Immediate noise counter determination process, that is, a process of determining whether or not the immediately preceding noise counter is 0 or less. If it is not 0 or less, the process proceeds to ST5, and if it is 0 or less, the process proceeds to ST8.
ST7: Subsequent noise counter setting determination process, that is, a process of determining whether or not a flag indicating that the subsequent noise counter is being set is set. If the flag is not set, the process returns to ST2 (current data acquisition), and if the flag is set, the process proceeds to ST9.
ST8: Subsequent noise counter setting determination process, that is, a process of determining whether or not a flag indicating that the subsequent noise counter is being set is set. If the flag is set, the process proceeds to ST10, and if the flag is not set, the process proceeds to ST11.
ST9: Subsequent noise counter determination process, that is, a process of determining whether or not the subsequent noise counter is 0 or less. If it is not 0 or less, it returns to ST2 (current data acquisition), and if it is 0 or less, it proceeds to ST12.
ST10: Subsequent noise counter reset process, that is, a process of resetting the succeeding noise counter, lowering a flag indicating that the succeeding noise counter is being set, and proceeding to ST5.
ST11: Subsequent noise counter set processing, that is, a process of setting a count value equivalent to 2 μs in the succeeding noise counter and setting a flag indicating that the succeeding noise counter is being set.
ST12: Partial discharge generation processing, that is, when the partial discharge generation determination means 11 determines that partial discharge has occurred and the time obtained by subtracting the second duration from the commercial frequency 1 cycle elapses, the recording in the 1-cycle memory 41 is recorded. A process of stopping and transmitting current data and time information for one cycle in each phase to the partial discharge analysis means.
After that, the partial discharge analysis means detects a waveform having a characteristic of partial discharge based on the current data and time information for one cycle in each phase.
When returning to ST2 from any step, a process of managing the immediately preceding noise counter and the succeeding noise counter (specifically, a process of reducing the count value by 1) is performed.

FIG. 4 is an explanatory diagram of a cross-bond grounding method for a three-phase power cable.
The cross-bond grounding method is used in extra-high and ultra-high pressure (220 kV or higher) power cables, and is a three-phase metal near both ends of the power cable in order to cancel the circulating current flowing through the metal sheath by electromagnetic induction. This is a method in which the sheaths are grounded together and three sets of metal sheaths of two of the three phases are short-circuited (cross-bonded) at the middle part of the power cable.
Cross-bonds 1 and 2 in FIG. 4 show a portion in which three sets of two-phase metal sheaths are short-circuited, and are provided at one or a plurality of locations depending on the length of the power cable.
In the second embodiment, when the current measuring means of the first embodiment is installed in each phase of the cross-bond grounding type power cable and the partial discharge generation determining means of any of the phases determines that a partial discharge has occurred, each of them. It is a partial discharge (hereinafter referred to as “partial discharge in the cross bond connection”) generated in the cross bond section shown in FIG. 4 based on the current data in the same time zone obtained by the phase current detecting means. It is a range determination means for determining whether or not.
The range determination means of the second embodiment is usually installed in the partial discharge analysis means of the first embodiment, and when the partial discharge generation determination means of any phase determines that a partial discharge has occurred, the current of each phase. Based on the current data and time information for one cycle obtained from the detection means, it is determined whether or not the cross-bond connection is a partial discharge.

FIG. 5 is a graph showing a part of each phase current data associated with partial discharge in a cross-bond grounded power cable.
In FIG. 5, the solid line graph shows the waveform of the current data determined to have the characteristic of partial discharge in the phase determined to have generated partial discharge, and the dotted line and one-point chain line graphs are solid line graphs in the other two phases. The waveform of the current data measured at the same time as is shown.
Here, if the waveform of the current data in the three phases accompanies the partial discharge in the cross-bond connection, in the cross-bond grounding type power cable, the partial discharge passes through the three-phase collective grounding point on the right side of FIG. In order to cancel the accompanying current change (the magnitude of the current change is the long dotted arrow in the upper right of Fig. 4), the current from the ground wire at the end of each phase is in the opposite direction to the current change due to partial discharge (the magnitude of the reverse current). 3 thin solid line arrows on the right side of FIG. 4) flow and propagate as a current wave.
Then, the current change (thick solid arrow in the upper right of FIG. 4), which is two-thirds of the current change due to the partial discharge, is measured in the ground wire of the phase in which the partial discharge is occurring, and the partial discharge in the other two phases. The reverse current change (thin solid line arrow in the center right of FIG. 4 and thin solid line arrow in the lower right of FIG. 4), which corresponds to one-third of the current change accompanying the discharge, is measured.

Utilizing the above phenomenon, the range determination means of the second embodiment determines whether or not the cross-bond connection is partially discharged by the following procedure.
(1) The polarity of the current peak of the waveform determined to have the characteristic of partial discharge is detected by the current peak polarity detecting means.
(2) The current peak value detecting means detects the magnitude (absolute value) of the current peak of the waveform determined to have the characteristic of partial discharge.
(3) The current peak time detecting means detects the time of the current peak of the waveform determined to have the characteristic of partial discharge.
(4) In the two phases other than the phase determined to have the characteristic of partial discharge by the partial discharge generation range determining means, the polarity of the current data at the time of the current peak detected in the above (3) is the above (1). It is determined whether or not the polarity of the detected current peak is opposite to that of the detected current peak, and the magnitude (absolute value) of the current data at the time of the current peak is twice as large as the magnitude of the current peak detected in (2) above. It is determined whether or not the difference from the (absolute value) is equal to or less than the determination value, and if the polarity is opposite and the difference is equal to or less than the determination value, it is determined that the cross-bond connection is a partial discharge.
(5) In the two phases other than the phase determined to have the characteristic of partial discharge, the magnitude (absolute value) of the current data at the time of the current peak detected in (3) above is small (almost unchanged). In that case, it is determined that it is a single partial discharge (partial discharge other than inside the cross-bond connection), and if not, it is determined that it is noise.

In the third embodiment, the insulation deterioration diagnosis device of the first embodiment is provided at two locations, one end and the other end of the power cable 1, and an insulation deterioration location locating device for identifying where the insulation deterioration location exists. A schematic diagram thereof is shown in FIG.

As shown in FIG. 6, the insulation deterioration location locating device of the third embodiment has one end side slave station 20 installed at one end of the power cable 1 and the other end side slave station installed at the other end of the power cable 1. It is composed of 21 and a master station 22 that defines a phase with an insulation deterioration portion and a position with an insulation deterioration portion based on the information transmitted from each of the slave stations 20 and 21.
The one-side slave station 20 is provided with the one-side insulation deterioration diagnosis device 23 having the same configuration as the insulation deterioration diagnosis device described in the first embodiment, and all detected by the partial discharge analysis means when it is determined that a partial discharge has occurred. The partial discharge detection information (phase information and time information of the waveform having the characteristic of partial discharge) is transmitted to the master station 22 by the one-side transmission means 24.
Further, the other end side slave station 21 includes the other end side insulation deterioration diagnosis device 25 having the same configuration as the insulation deterioration diagnosis device described in the first embodiment, and when it is determined that a partial discharge has occurred, the partial discharge analysis means. All the partial discharge detection information detected by is transmitted to the master station 22 by the other end side transmitting means 26.
The master station 22 includes a receiving means 27 that receives information transmitted from each of the slave stations 20 and 21, and an insulating deterioration position calculating means 28 that calculates a position where the insulation deteriorated portion is located based on the information received by the receiving means 27. The display means 29 for displaying the calculated position of the insulation deterioration portion is provided.

The insulation deterioration position calculation means 28 identifies a phase having an insulation deterioration location based on all the partial discharge detection information transmitted from the slave stations 20 and 21 and received by the reception means 27, and at the same insulation deterioration location. The time difference between the partial discharge detection information that is thought to have reached the slave station 20 at one end and the partial discharge detection information that is thought to have reached the slave station 21 at the other end is propagated due to the partial discharge that occurred at the same timing. A pair within the time required for the cable to pass through (hereinafter referred to as "pair information") is determined, and the time when the waveform having the characteristic of partial discharge reaches the slave stations 20 and 21 is specified.
Then, if the time when the waveform having the characteristic of partial discharge reaches each of the slave stations 20 and 21 can be specified, the position where the insulation deterioration portion is located is calculated by the formula 1 by the method described in Japanese Patent Application Laid-Open No. 2001-133504. can do.
Equation 1: L1 = {L + (t1-t2) × v} / 2
Here, L1 is the length of the power cable 1 from the slave station 20 on one end to the position where the insulation is deteriorated, and L is the length of the power cable 1 from the slave station 20 on one end to the slave station 21 on the other end, t1. Is the arrival time at one end side slave station 20, t2 is the arrival time at the other end side slave station 21, and v is the current propagation velocity in the power cable 1.
In addition, since each slave station starts the partial discharge detection at a fixed time or at a designated hour (1 second, 10 seconds, or 1 minute after the instruction to restart the partial discharge detection), each of the generated partial discharges is detected. If the slave station detects it, the time can be matched.

FIG. 7 is a flowchart showing a processing procedure of the insulation deterioration position calculation means 28.
(1) Partial discharge information reception processing While receiving partial discharge detection information for one cycle from one end side slave station 20 (hereinafter referred to as "one end side partial discharge information"), one cycle worth of partial discharge information is received from the other end side slave station 21. The partial discharge detection information (hereinafter referred to as "the other end side partial discharge information") is received (ST31).
(2) Data comparison processing on both ends side One data (hereinafter referred to as "one end side data") is extracted from one end side partial discharge information (ST32), and the other end side data extraction counter is initialized (included in the other end side partial discharge information). After (ST33), one data (hereinafter referred to as "other end side data") is taken out from the other end side partial discharge information (ST34).
Then, it is determined whether or not the phase information of the one end side data and the phase information of the other end side data match (ST35), and if they do not match, the process returns to ST34, and if they match, the process proceeds to ST36.
When returning to ST34, the data retrieval counter on the other end side is decremented by 1, and if it becomes 0, the process proceeds to ST38.
(3) Pair information extraction processing Propagation by dividing the length (L) of the power cable 1 between the slave station 20 on one end side and the slave station 21 on the other end side by the current propagation velocity (v) between both ends of the power cable 1. Obtain the permissible time (L / v).
Then, the time difference (| t1-t2 |) between the time information (t1) of the one-sided data and the time information (t2) of the other-side data is obtained, and whether | t1-t2 | ≦ L / v is satisfied. It is determined whether or not (ST36), and if it is not satisfied, the process returns to ST34, and if it is satisfied, they are extracted as pair information and the process proceeds to ST37.
As in (2) above, when returning to ST34, the data retrieval counter on the other end side is decremented by 1, and if it becomes 0, the process proceeds to ST38.
(4) Insulation Deterioration Position Calculation Process For the extracted pair information, the length (L1) of the power cable 1 from the position where the insulation deterioration point is located, that is, from the one-side slave station 20 to the position where the insulation deterioration location is located is calculated by Equation 1. Calculate and save the calculation result (ST37).
(5) One-sided data end confirmation process It is confirmed whether all the data has been taken out from the one-sided partial discharge information (ST38), and if it has not been taken out, it returns to ST32, and if it has been taken out, it ends.

With respect to the pair information extracted by such a procedure, the information regarding the phase having the identified insulation deterioration portion and the calculated position of the insulation deterioration portion is output to the display means 29.
As information on the phase, characters such as U, V, W and blue, red, and white are usually used, and as information on the length, a numerical value indicating the length from the slave station 20 at one end is usually used, but blue, A red and white cable layout diagram may be displayed together with a map, and a mark or the like indicating a location of insulation deterioration in the cable may be used.

A modification of the insulation deterioration diagnosis device of Example 1 and the insulation deterioration location locating device of Example 3 is listed.
(1) In the first embodiment, an example in which the insulation deterioration diagnosis device is applied to a three-phase power cable has been described, but it can also be applied to a single-phase or two-phase power cable.
(2) In the insulation deterioration diagnostic apparatus of Example 1, in order to save memory, current data for one cycle of commercial frequency and the like are cyclically recorded in the memory 41 for one cycle, but current data for multiple cycles of commercial frequency and the like are recorded cyclically. May be recorded cyclically.
(3) In the insulation deterioration diagnostic apparatus of Example 1, the current data recorded in the one-cycle memory 41 was subjected to feature quantity extraction and determination as to whether or not the waveform had a possibility of partial discharge. In place of or in addition to the current data, low-frequency current data may be recorded for one commercial frequency cycle to perform feature extraction and determination of whether or not the waveform has a possibility of partial discharge.

(4) Although the description has been made on the premise of a three-phase power cable in the third embodiment, it can also be applied to a single-phase or two-phase power cable, and in the case of a single-phase power cable, it is not necessary to transmit phase information.
(5) In the third embodiment, one end side slave station 20, the other end side slave station 21 and the master station 22 are installed, but the master station 22 may also serve as one end side slave station 20 or the other end side slave station 21. good.
That is, either one end side slave station 20 or the other end side slave station 21 may have a master station function.

1 Power cable 2 Cable head 3 Ground wire 4 Current detection means 5 Timing means 6 Feature extraction means 7 Noise detection means 8 Partial discharge waveform judgment means 9 Immediately preceding noise management means 10 Subsequent noise management means 11 Partial discharge generation judgment means 20 One end side Slave station 21 End side slave station 22 Master station 23 One end side insulation deterioration diagnostic device 24 One end side transmission means 25 One end side insulation deterioration diagnosis device 26 Other end side transmission means 27 Reception means 28 Insulation deterioration position calculation means 29 Display means 41 1 cycle memory

Claims (4)

A current detecting means for detecting a ground line current in a power cable or an electric device,
A feature amount extraction means for extracting a feature amount from current data based on a current detection value detected at regular time intervals by the current detection means, and a feature amount extraction means.
A partial discharge waveform determining means for determining the presence or absence of a partial discharge feature based on the feature amount extracted by the feature amount extracting means,
A noise detection means that detects noise with a magnitude greater than or equal to a predetermined threshold, and
Whether the time when the partial discharge waveform determining means determines that there is a characteristic of partial discharge is after the first duration elapses after the noise detecting means detects noise having a magnitude equal to or larger than a predetermined threshold value. Immediately before determining whether or not noise management means and
Whether or not the noise detecting means has detected noise having a magnitude equal to or greater than a predetermined threshold value from the time when the partial discharge waveform determining means determines that the partial discharge has a characteristic to the time when the second duration elapses. Subsequent noise management means to determine and
It is determined that the first duration has elapsed since the immediately preceding noise management means detected noise having a magnitude equal to or larger than a predetermined threshold value, and the subsequent noise management means has a characteristic of partial discharge. It is provided with a partial discharge generation determining means for determining that a partial discharge has occurred when it is determined that noise having a magnitude equal to or larger than a predetermined threshold value has not been detected between the time of the determination and the elapse of the second duration. An insulation deterioration diagnostic device characterized by this. When the first wave of the partial discharge is falling, the feature amount extracting means extracts the magnitude of the falling current value, the required falling time, the magnitude of the rising current value, and the required rising time as the feature amount.
In the partial discharge waveform determining means, the magnitude of the falling current value is within a predetermined range, the required falling time is within the third duration, and the magnitude of the rising current value is the falling current value. When the conditions that the size is larger and the rise time is larger than the fall time and less than 3 times the fall time are satisfied, it is judged that the partial discharge is characteristic.
When the first wave of the partial discharge is rising, the feature amount extracting means extracts the magnitude of the rising current value, the required rising time, the magnitude of the falling current value, and the required falling time as the feature amount.
The partial discharge waveform determining means means that the magnitude of the rising current value is within a predetermined range, the required rising time is within a predetermined time, the magnitude of the falling current value is larger than the magnitude of the rising current value, and The insulation deterioration diagnosis according to claim 1, wherein it is determined that there is a characteristic of partial discharge when the condition that the required fall time is larger than the required rise time and less than three times the required rise time is satisfied. Device. The insulation deterioration diagnostic apparatus according to claim 1 or 2 is installed in each phase of the three-phase power cable.
When the partial discharge generation determination means of any phase determines that a partial discharge has occurred, the recording of the current data and time information of each phase in the one-cycle memory is stopped, and the recording of each phase at the time of the stop is stopped. A partial discharge analysis means for receiving the information of the one-cycle memory is provided.
The partial discharge analysis means
Current peak polarity detecting means for detecting the polarity of the current peak of the waveform determined by the feature amount extracting means and the partial discharge waveform determining means based on the received current data and time information of each phase. In two phases other than the current peak value detecting means for detecting the absolute value of the current peak, the current peak time detecting means for detecting the time of the current peak, and the phase determined to have the characteristic of partial discharge. The other-phase current polarity detecting means for detecting the polarity of the current data at the time of the current peak, the other-phase current value detecting means for detecting the absolute value of the current data at the time of the current peak, and the other-phase current value detecting means.
The polarity detected by the current peak polarity detecting means and the polarity detected by the other-phase current polarity detecting means are opposite polarities, and the absolute value detected by the current peak value detecting means and the other-phase current value. Insulation characterized by having a partial discharge generation range determining means for determining a partial discharge in a cross-bond connection when the difference from twice the absolute value detected by the detecting means is less than or equal to the determination value. Deterioration diagnostic equipment. One end side slave station is provided on one end side of the power cable or the electric device, and the other end side slave station is provided on the other end side of the power cable or the electric device.
One end of the slave station is one end when it is determined that a partial discharge has occurred by the one end side insulation deterioration diagnosis device and the one end side insulation deterioration diagnosis device having the same configuration as the insulation deterioration diagnosis device according to claim 1 or 2. A one-sided transmission means for transmitting side partial discharge information to the master station is provided.
It was determined that the other end side slave station was partially discharged by the other end side insulation deterioration diagnosis device and the other end side insulation deterioration diagnosis device having the same configuration as the insulation deterioration diagnosis device according to claim 1 or 2. At the time, the other end side transmitting means for transmitting the other end side partial discharge information to the master station is provided.
The master station calculates the position of the insulation deterioration location based on the length and current propagation speed of the electric wire of the power cable or the electric device, and the received one-side partial discharge information and the other-end partial discharge information. Means and
An insulation deterioration location locating device comprising a display means for displaying position information of the insulation deterioration location based on a calculation result by the insulation deterioration position calculation means.

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