JP3160612B2 - Power system insulation deterioration detection method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detecting insulation deterioration in a power system, and more particularly to a method and apparatus for detecting insulation deterioration in a power distribution system and judging a section in which the deterioration occurs with high sensitivity. The present invention relates to a detection method and device.

[0002]

2. Description of the Related Art Generally, a power system is provided with a protection device for detecting a failure such as a ground fault or a short circuit and stopping power transmission. Such protection devices, for example, in the case of distribution systems,
Since it is provided at the root of the tree-shaped system, once a failure occurs and the protection device operates, a wide-area power failure will be caused. For this reason, regular equipment replacement and patrol inspections are performed to prevent failures.However, in the distribution system, many electrical distribution materials are widely distributed and exposed to various environments. , Due to the fact that equipment is being concealed,
It has not been effective enough.

Most of the failures that occur in actual distribution lines are
This is a ground fault, and this type of failure often involves some precursory phenomenon. Therefore, a technique has been proposed in which the occurrence of insulation deterioration and the section in which the deterioration is detected by detecting the precursor phenomenon are performed, so that the equipment is renewed intensively to prevent a failure before it occurs.

As this prior art, "Basic study on detection method of insulation degradation section of wiring system" (Arayama, Aoyagi,
And the National Institute of Electrical and Energy Engineers of Japan in 1991.

[0005]

In the prior art, it is difficult to distinguish a signal generated due to residual components or pulsed noise from a signal generated due to insulation deterioration, and it has been difficult to detect insulation deterioration with high sensitivity.

It is an object of the present invention to reduce the influence of these residual components and pulse noise, and to detect and determine the occurrence of insulation deterioration of a power system and its section with high sensitivity.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to provide a signal excluding the above-mentioned power supply frequency in a band excluding the above-mentioned power supply frequency by using a signal obtained by removing a high-frequency component equal to or greater than an integral multiple of the power supply frequency of the zero-phase voltage and / or the zero-phase current as a trigger. This is achieved by detecting the occurrence of insulation deterioration using the phase difference spectrum between the zero-phase voltage and the zero-phase current.

[0008] The above-mentioned problems also exist except for ± 10 Hz of the power supply frequency and its integral multiple frequency, and 0 to 10 Hz.
In addition, this is achieved by detecting the occurrence of insulation deterioration using the average value of the phase difference spectrum between the zero-phase voltage and the zero-phase current having a frequency four times or less the power supply frequency.

[0009] The above-mentioned problem also exists in a device for detecting insulation deterioration of a three-phase power system, the value of the zero-phase voltage and / or the zero-phase current of power flowing through the power transmission line when the power transmission line is mounted at an interval. And a plurality of sensor devices that detect the power supply frequency and an integer multiple thereof from the value of the zero-phase voltage and / or the zero-phase current detected by the corresponding sensor devices provided for each of the sensor devices. Calculating means for calculating the magnitude of the generation level of the zero-phase voltage and the zero-phase current, comparing the magnitude of the generation level with a preset value, and outputting the result; and It is also attained by providing a determination means for determining whether or not insulation deterioration has occurred by inputting the outputs of the plurality of calculation means.

[0010] The above-mentioned problems also exist in the insulation of a three-phase power system.
In a device that detects deterioration, equip
And the zero-phase voltage and / or zero of the power flowing through the transmission line.
A plurality of sensor devices for detecting the value of the phase current;
The corresponding sensor device is provided for each
From the value of the zero-phase voltage and / or zero-phase current
-Phase voltage and zero-phase voltage in the band excluding frequency
The magnitude of the flow generation level is calculated, and the magnitude of the generation level is calculated.
Which is smaller than the preset value
Calculating means for outputting the data, and connecting to the plurality of calculating means
The output of the plurality of arithmetic means is provided and the
Judgment of insulation deterioration occurs when preset value is small
The calculating means calculates a phase difference spectrum pattern of the zero-phase voltage and the zero-phase current from the input values of the zero-phase voltage and the zero-phase current, and calculates the phase difference spectrum pattern. Calculate a phase difference average value in a band excluding at least a power supply frequency and an integral multiple of the power supply frequency from the negative frequency and calculate a sum difference between the phase difference average value and a phase difference average value calculated by an adjacent calculating means. The present invention is also achieved by an insulation deterioration detection device for a power system , which determines an insulation deterioration occurrence section based on a sum difference.

[0011] The above problem is further determining means is for determining the overall judgment to insulation degradation occurs interval results in which a plurality of operation means collects insulation deterioration occurs section outputting were collected preceding This is also achieved by the power system insulation deterioration detecting device described in (1).

[0012]

The signs of insulation deterioration in the distribution system often appear as single and intermittent discharge phenomena. This will be described with reference to the example of cracking of the insulator. First, even if a crack is generated only in the insulator, no abnormality occurs on the insulation. However, if salt water or the like permeates the crack, the dielectric strength decreases, leading to a ground fault discharge, and a discharge current flows. But,
When the discharge continues to some extent, the temperature rises in that part, and the moisture evaporates, and the state returns to a normal state temporarily. Since such a short-to-ground fault has a short duration, the protection device does not operate, so that the occurrence of a crack remains unknown. As a result, while repeating the sporadic discharge again,
Eventually, it will be a permanent failure. During this time, the duration of the discharge is relatively long, so that the protection device may operate. However, even in this case, when the power is retransmitted, the moisture evaporates, making it extremely difficult to find the cause.

Therefore, if the occurrence of insulation deterioration is detected by capturing an instantaneous ground fault and the section can be located, the equipment can be systematically replaced before a permanent failure occurs. However, as described above, in the actual distribution system, in addition to the instantaneous ground fault signal, a relatively large residue and a lot of pulse noise are generated, and it is necessary to distinguish these phenomena from the instantaneous ground fault signal. Was difficult.

The inventors have found that the spectrum of the instantaneous ground fault signal has a characteristic different from that of the residual or pulse noise, and the instantaneous ground fault is detected with high sensitivity by using the characteristic. The section could be located. This feature is that the spectrum of zero-sequence voltage and zero-sequence current due to a discontinuous phenomenon such as instantaneous ground fault contains many subharmonic components in addition to the power supply frequency and its integral multiple frequency. The spectrum has a tendency to increase as the frequency component decreases. On the other hand, the residual portion occurs only at the power supply frequency and its integral multiple frequency. It was also found that the subharmonic component generated by the pulse noise occurs in the zero-phase current, but hardly occurs in the zero-phase voltage, and that there is no characteristic that the frequency increases as the frequency decreases.

In the present invention, first, the occurrence of deterioration is detected based on the generation level of the zero-phase voltage and / or the zero-phase current in a band excluding the power supply frequency and an integer multiple thereof. Also,
The degradation occurrence section is located by utilizing the fact that the spectral pattern of the zero-phase current and the zero-phase voltage in the band changes according to the relative positional relationship between the degradation occurrence point and the detection point.

[0016]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a state in which an insulation deterioration detecting device according to the present invention is mounted on a three-phase distribution system.

The distribution system shown in FIG. 1 operates according to a transformer 1 for transforming power supplied from a higher-level high-voltage system into a distribution voltage, and a cutoff command of a protection device (not shown) connected to the transformer 1. A circuit breaker 2, a three-phase bus 3 connected to the circuit breaker 2, and a three-phase feeder (here, a plurality of transmission lines connected to the three-phase bus 3 via circuit breakers 7, 8, and 9). (Including three feeders). The insulation deterioration detecting device mounted on the distribution system includes sensor devices 10A to 10C, 11A to 11C, 12 mounted on the three-phase feeders 4, 5, and 6 at predetermined intervals.
A to 12C and slave stations 1 which are arithmetic means connected to these sensor devices and receiving output signals of the sensor devices, respectively.
Communication line 1 for interconnecting 3A to 13C, 14A to 14C, 15A to 15C and adjacent slave stations on the same feeder
6, 17, 18 and the circuit breakers 7, 8, 9 of the respective feeders.
Stations 13A, 14A, 15A located closest to
And a master station 19 which is a judging means arranged and connected to the main station.

Next, the functions and configurations of the sensor device and the slave station will be described with reference to FIGS. 2 and 3, taking the sensor device 10A and the slave station 13A as examples. Sensor device 10
A to 10C, 11A to 11C, 12A to 12C all have the same configuration, and slave stations 13A to 13C, 14A to 14C,
15A to 15C all have the same configuration.

FIG. 2 is a block diagram showing the functions of the sensor device 10A and the slave station 13A. Zero-phase voltage detection block 2
At 0, the zero-phase voltage of the transmission line 4 at the detection point is detected, and the zero-phase current at the detection point is detected by the zero-phase current detection block 21. The power supply frequency component and its integral multiple frequency component are removed from the detected zero-phase voltage as unnecessary frequency components by the unnecessary frequency component removal block 23A. Similarly,
The unnecessary frequency component removal block 23B also removes the power supply frequency component and its integral multiple frequency component from the zero-phase current detected by the zero-phase current detection block 21. The zero-sequence voltage and zero-sequence current from which the unnecessary frequency components have been removed (ie, subharmonic components and non-integer multiple harmonic components) are converted into a phase difference spectrum by a phase difference spectrum conversion block 30. Next, in the phase difference comparison block 31, the phase difference spectrum at the detection point obtained by the conversion and the phase difference spectrum similarly converted based on the zero-phase voltage and the zero-phase current at the other detection points are calculated. Are compared. Deterioration determination is performed in the deterioration determination block 32 based on the comparison result.

The sensor device 10A includes a zero-phase voltage sensor 20 connected to the three-phase feeder 4 and a three-phase feeder 4
And a zero-phase current sensor 21 coupled to The slave station 13A outputs the output v of the zero-phase voltage sensor 20.
₀ (t) and an output i ₀ (t) of the zero-phase current sensor 21, a two-channel filter 23 and an AD converter 2 connected to the output side of the amplifier 22, respectively.
4 and a memory 2 connected to the output side of the AD converter 24.
5, a comparison circuit 26 connected to the output side of the filter 23, an AND circuit 27 connected to the output side of the comparison circuit 26, the output side of which is connected to the memory 25, and the output side of the memory 25. , And a communication terminal 29 connected to the output side of the processing device 28. The communication terminal 29 is connected to the adjacent slave station 13B on the same feeder as the master station 19 via the communication line 16.

The above-configured sensor device and slave station operate as follows. The output v ₀ (t) of the zero-phase voltage sensor 20 and the output i ₀ (t) of the zero-phase current sensor 21 are
And converted into a voltage signal suitable for signal processing and output. The output signal of the amplifier 22 is input to a two-channel filter 23 and an AD converter 24, respectively. AD
The analog signals of v ₀ (t) and i ₀ (t) input to the converter 24 are converted into digital signals v ₀ (t) d and i ₀ (t) d, and the output is written to the memory 25.

On the other hand, the signal v input to the filter 23
₀ (t) and i ₀ (t) are removed by the filter 23 after removing high frequency components equal to or higher than an integral multiple frequency component (preferably twice the frequency) of the power supply frequency, respectively, and v ₀ ′ (t),
It is input to the comparison circuit 26 as i ₀ ′ (t). In the comparison circuit 26, the input v ₀ ′ (t) and i ₀ ′ (t) are respectively compared with preset threshold values, and v ₀ ′ (t), i
_{If 0} '(t) exceeds the threshold, the signal is
Is output to Here, if both v ₀ ′ (t) and i ₀ ′ (t) exceed the threshold, both inputs to the AND circuit 27 are turned on, and a signal is output from the AND circuit 27 to the memory 25, and Is held. The contents of the held memory are transferred to the processing device 28 and processed in accordance with the algorithm described later. Then, the processing result is transmitted to another slave station or master station 19 via the communication terminal 16 via the communication terminal 29. You.

The operation of the above-mentioned slave station will be described in detail including an algorithm with reference to FIG. In FIG. 4, the operation of S1 (step 1) to S3 (step 3) is the zero-phase voltage v
₀ (t), the progress of holding the zero-phase current i ₀ (t) in the memory 25, and the operation after S4 is the processing content in the processing device 28.

First, in S 1, digital signals v ₀ (t) d and i ₀ (t) d of zero-phase voltage and zero-phase current are written in the memory 25. At S2, as described above, it is determined whether or not to hold the memory contents of the memory 25, and if there is no need to hold, the process returns to S1 and new data is overwritten on the memory 25. The output v of the filter 23 in S2
_{If both 0} ′ (t) and i ₀ ′ (t) exceed the threshold value, it is determined that the possibility of occurrence of deterioration is strong, and as shown in S3, the time when the threshold value is exceeded is centered. Before and after v
₀ (t) d, the memory contents of the i ₀ (t) d data is held. In the present embodiment, as the threshold value, v ₀ ′ (t),
A value three times i ₀ '(t) was set.

Here, the contents of the memory 25 are held when both v ₀ (t) and i ₀ (t) data exceed the threshold value, but when either one of the data exceeds the threshold value, may be determined that the degradation occurs in highly likely, further, v ₀
The determination may be made based on only one of the data of (t) and i ₀ (t).

At S4, the contents of the memory 25 are
After being transferred to 8, the Fourier analysis is performed on v ₀ (t) d and i ₀ (t) d, and the result is stored in V ₀ (f) and I ₀ (f). Here, V ₀ (f) and I ₀ (f) are complex quantities composed of an absolute value and a phase. In S5, V ₀ (f), I ₀
Using the phase of (f), their phase difference θ ₁ is calculated for each frequency.

FIGS. 5 to 7 show examples of the results obtained by actually deteriorating the distribution equipment and performing the processing up to S5. The power supply frequency is 50 Hz. FIG. 5 shows the zero-phase voltage | V ₀ (f)
| Are expressed in dB as a function of frequency Hz, and FIG.
Represents the value of the zero-phase current | I ₀ (f) | in dB as a function of the frequency Hz. 5 and 6, 5
The peaks that occur at 0 Hz and its integer multiples, especially odd multiples of the frequency, occur at almost the same level even when sound, and so-called residuals are dominant | V ₀ (f) |, | I ₀ ( f)
|. In the case of FIG. 5 and FIG. 6, many subharmonic components, ie, many frequency components below the power supply frequency and between the power supply frequency and its integral multiple frequency components, occur in addition to the above-mentioned residual components. The spectrum of the voltage tends to increase as the frequency component decreases. As described above, these features are common in intermittent instantaneous ground fault signals, and the present invention has been made by paying attention to these features.

FIG. 7 shows the phase difference θ ₁ between V ₀ (f) and I ₀ (f). As shown, the spectral pattern of the phase difference theta ₁ shows a tendency to be distributed in the vicinity of 90 degrees in the following band several hundred Hz. This pattern changes variously depending on the deterioration point and the sensor position. In the procedure after S6, the deterioration occurrence section is determined using the characteristics of such a pattern.

In step S6, the power supply frequency and a quadruple frequency of the power supply frequency excluding ± 10 Hz and 0 to 10 Hz of its integral multiple frequency (200 Hz when the power supply frequency is 50 Hz)
The sum of the following phase difference spectra θ ₁ is obtained, and the average value << θ ₁ >> is calculated. Here, the reason for using the average value is that even if the data for calculating the phase difference contains noise, the phase difference due to the noise is distributed near zero degrees, so the average value is close to zero and the noise This is because the effect of the above can be reduced. Further, as a frequency band, 0 to 10
The reason for excluding Hz and the power supply frequency and ± 10 Hz of its integral multiple frequency is that the phase measurement accuracy is a band governed by the residual. In addition, 200Hz
The reason for taking the average only in the following bands is that the zero-phase voltage is mainly distributed in this band, and the S / N ratio deteriorates above this band.

In S7, if there is a slave station on the power supply side (upstream side) of the own station, the average phase difference value << θ ₁ >> of the own station is transmitted to the adjacent slave station on the power supply side. In addition, the average phase difference value << θ ₂ >> obtained by the same calculation from the adjacent slave station on the load side (downstream side) is received and taken into the processing device 28. Here, in the case of the slave station located closest to the power supply side, it is necessary to transmit the calculated << θ ₁ >> to the master station only by receiving the data << θ ₂ >> of the adjacent slave station on the load side. Do not. In S8, the processing device 28
Deterioration determination processing is performed using the phase difference average values << θ ₁ >> and << θ ₂ >> taken in. This processing is described in FIG.
This will be described with reference to FIG.

FIG. 8 is a diagram showing a case where deterioration occurs in a section between the sensor devices 10A and 10B of the feeder 4 in FIG.
The average phase difference << θ ₁ >> obtained in each slave station is shown. As shown in FIG. 8, the sensor device 10A on the power supply side from the deterioration point
In addition to the fact that only the phase difference average value << θ ₁ >> obtained at the slave station 13A by the output signal of the above shows a value near -90 degrees, the values of all other slave stations are values near 90 degrees. . The reason for this is that in general resistance degradation, as a result of leakage current having a phase of -90 degrees with respect to the zero-sequence voltage flowing to the ground, the zero-sequence current at the point closer to the power supply than the degradation point is less than the zero-sequence voltage. T
It has a phase difference of 90 degrees and at the point on the load side from the degradation point,
This is because the zero-phase current has a 90-degree leading phase with respect to the zero-phase voltage.

As described above, the phase of the zero-sequence current with respect to the zero-sequence voltage differs by about 180 degrees across the degradation point, and becomes about -90 degrees on the power supply side and about 90 degrees on the load side and other feeders. Therefore, as a determination algorithm of S8 in FIG. 4, as shown in FIG. 9, first, in S8-1, the sum α and difference β of << θ ₁ >> and << θ ₂ >> are obtained. In S8-2, β
It is determined whether or not the absolute value of is greater than or equal to 90 degrees. If the absolute value is greater than or equal to 90 degrees, it is determined that the slave station that transmitted << θ ₂ >>, that is, "deterioration has occurred between the load-side adjacent slave station and its own station" Proceed to S9. If the absolute value of β is 90 degrees or less, the process proceeds to S8-3.
In S8-3, if the absolute value of α is 90 degrees or less, it is determined that α is caused by noise, and the process proceeds to S9.
If the absolute value of α is 90 degrees or more, it is determined that deterioration has occurred in another section (a section other than the section between the load side adjacent child station and the own station), and the process proceeds to S8-4. In S8-4, the sign of the sign of α is checked. If the value of α is positive, it is determined that “deterioration has occurred in the power supply section or another feeder” and the process proceeds to S9. If the value of α is negative, It is determined that “deterioration has occurred in another section on the load side” and S9
Proceed to.

In S9, the result of the determination is transmitted to the master station 19 via the communication terminal 29 and the communication line 16. The master station 19 collects the determination results transmitted from each of the slave stations, comprehensively checks the determination results of all the slave stations, determines “whether or not deterioration has occurred” and “deterioration occurrence section”, and determines the number of times of deterioration occurrence. It outputs reference data for maintenance such as ranking of deterioration alarm signal based on the accumulated value.

According to the above embodiment of the present invention, the influence of residual noise and pulse noise can be reduced, the occurrence of insulation deterioration and its section can be detected with high sensitivity, and the phase difference calculated by each slave station can be detected. Since only the average value and the determination result are transmitted, there is an effect that the amount of transmission is small.

In the above-described embodiment, a binary decision method of determining whether the value obtained as a result of the calculation is larger than a predetermined value is used for the deterioration decision. A method of indicating the degree of fuzzy, that is, the degree of deterioration by a continuous amount may be used.

The band for obtaining the average value of the phase difference is set to 20.
Although the frequency is set to 0 Hz or less, this band may be arbitrarily changed. For example, when the frequency is 90 Hz or less, data in a band near the power supply frequency may be simply removed.

[0037]

As described above, according to the present invention,
Since the influence of residual components and pulse noise on the zero-phase current and / or zero-phase voltage detected from the power system is reduced, the occurrence of insulation deterioration of the power system and the detection and determination of the generation section can be performed with high sensitivity. Has the effect

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a state in which an embodiment of the present invention is applied to a distribution system.

FIG. 2 is a functional block diagram of the embodiment shown in FIG. 1;

FIG. 3 is a circuit diagram showing details of an example of an apparatus for realizing the functions shown in FIG. 2;

FIG. 4 is a flowchart showing an embodiment of the present invention.

FIG. 5 is a graph showing an intermediate result of the processing according to FIG. 4;

FIG. 6 is a graph showing an intermediate result of the processing according to FIG. 4;

FIG. 7 is a graph showing an intermediate result of the processing according to FIG. 4;

FIG. 8 is a diagram showing an example of data obtained in the embodiment shown in FIG.

FIG. 9 is a procedure diagram showing details of a part of the procedure shown in FIG. 4;

[Explanation of symbols]

4, 5, 6 Transmission line (three-phase feeder) 10A to 10C, 11A to 11C, 12A to 12C Sensor device 13A to 13C, 14A to 14C, 15A to 15C Operation means (slave station) 19 Determination means (master station)

──────────────────────────────────────────────────続 き Continuing from the front page (72) Kunio Hirasawa 4026 Kuji-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Hiroshi Haga 1-1-1 Kokubuncho, Hitachi City, Ibaraki Stock Company Hitachi, Ltd. Kokubu Plant (72) Inventor Hisashinobu Torii 2-4-1, Nishi-Atsujigaoka, Chofu-shi, Tokyo Tokyo Electric Power Company Technical Research Institute (56) References JP-A-2-111217 (JP, A) 2-136435 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02H 3/00 G01R 31/12 H02H 7/26

Claims (2)

(57) [Claims] An apparatus for detecting insulation deterioration of a three-phase power system.
In the above, it is attached to the transmission line at intervals, and
Detects zero-phase voltage and / or zero-phase current value of flowing power
And a plurality of sensor devices corresponding to the respective sensor devices.
The zero-phase voltage detected by the corresponding sensor device and
Or the power supply frequency and its integral multiple frequency from the zero-phase current value
Large generation level of zero-sequence voltage and zero-sequence current
Calculated, and the magnitude of the occurrence level is set in advance.
Operator that outputs which of the two is smaller than the value
And a plurality of stages provided in connection with the plurality of arithmetic means.
The output of the calculating means is input and the preset value
Judgment means for judging occurrence of insulation deterioration when
The computing means calculates the input zero-phase voltage and the zero-phase voltage
From the current value, the phase difference spectrum
Calculate the pattern and calculate a small number from the phase difference spectrum pattern.
At least in the band excluding the power supply frequency and its integral multiple frequency
Calculate the average phase difference value and calculate the average
Calculating the sum difference with the phase difference average value calculated by the calculating means
And determining an insulation deterioration occurrence section based on the sum difference.
An insulation deterioration detection device for a power system, characterized in that: 2. The method according to claim 1, wherein the determining means outputs a plurality of arithmetic means.
Collect insulation degradation sections and comprehensively judge the collected results.
To determine the insulation deterioration section.
2. The apparatus for detecting insulation deterioration of a power system according to claim 1, wherein
Place .