JPH09243700A - Gas discharge device partial discharge detection method and detection device - Google Patents

Abstract

(57) Abstract: It is possible to reliably determine the presence or absence of partial discharge occurrence even if an electrical noise pulse is output from an opto-electrical conversion unit. SOLUTION: An average value No of the number of electric noise pulses output from an opto-electric converter 16 per unit time when an optical pulse is not generated is obtained in advance, and the opto-electric converter 6 is used to measure the partial discharge. An average value Nm of the number of electric pulses output per unit time is obtained, and when the average value Nm is larger than the average value No, it is determined that partial discharge has occurred and the notification is made.

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 light of partial discharge generated inside a closed container of a gas insulation device.

[0002]

2. Description of the Related Art A gas-insulated device is a compact structure in which a high-voltage transformer and a switchgear are housed in an airtight container together with an insulating gas such as SF ₆ gas. When a partial discharge occurs inside this closed container, the insulating part may deteriorate and eventually dielectric breakdown may occur. Therefore, a device for detecting whether or not partial discharge is generated in the closed container during operation of the device is provided outside the closed container. Partial discharge is a phenomenon in which a current flows in a pulsed manner and light is emitted in a pulsed manner. Therefore, the methods for detecting the partial discharge include a method of detecting an electric pulse with an electric circuit and a method of optically detecting an optical pulse. There is a method.

The former method for detecting electric pulses is often difficult to distinguish between external electric noise and electric pulses due to partial discharge at the site of equipment installation, which eventually leads to a decrease in detection sensitivity of partial discharge. ing. On the other hand, the latter method of detecting an optical pulse has an advantage that it is not affected by external noise at the site because the storage container of the electric device is light-shielding. However, when it is attempted to increase the detection sensitivity of the partial discharge, the electrical noise generated from the photoelectric conversion unit itself that converts light into electricity influences the detection sensitivity.

That is, the heart of the photoelectric conversion section is a photomultiplier tube or a photodiode. Photomultiplier tube
A photocathode (cathode), a plurality of secondary electron multiplication planes (dynodes), and a collector (anode) are provided in the vacuum tube, and a positive voltage is sequentially applied between the photocathode, each dynode, and the collector. When the photocathode receives light from the outside, photoelectrons are generated. The photoelectrons are accelerated by the electric field and collide with a plurality of dynodes one after another to emit secondary electrons. Since the dynode emits a plurality of secondary electrons for one photoelectron, the number of electrons is multiplied each time it collides with the dynode. The number of multiplied electrons is finally captured by the collector,
It is taken out as an electric current. The sensitivity of the photomultiplier tube depends on the material and the number of multiplication stages, but the multiplication factor is 10 ⁵ to 10
It is about ⁷ and can convert weak light into electricity and output it.

The photodiode is a semiconductor and is generally used as a so-called light receiving element together with an optical fiber cable for optical control and optical communication. When a pn junction is formed of, for example, Si or Ge, and this junction is irradiated with light, electron-hole pairs are generated in the p-type and n-type semiconductors. Among them, electrons in the p region are attracted to the n region and holes in the n region are attracted to the p region, so that currents are output from both terminals of the photodiode. Since this output current is proportional to the amount of light applied, it means that the light is converted into the amount of electricity. The photodiode is a pn junction diode, p-
There are i-n junction diodes and avalanche diodes, and the latter avalanche diode is one more than the former two.
The sensitivity is about 0 ² to 10 ⁴ .

[0006] In these opto-electric converters, an electric noise pulse is generated on the output side when the detection sensitivity is extremely increased. A noise pulse is output even if the light receiving surface of the photomultiplier tube or the photodiode is not exposed. The noise pulses include those caused by thermoelectrons that are inevitably generated from the material itself and those caused by the inclusion of impurities contained in the material. In order to suppress the generation of noise pulses, the temperature of the photoelectric conversion unit is usually lowered to about -20 °. Although the generation of the noise pulse is largely reduced by this, the generation of the noise pulse cannot be eliminated.

In particular, noise pulses that are randomly output at intervals of several seconds to several minutes are large, which determines the detection sensitivity of partial discharge of the device. When the photoelectric conversion unit is used in a photoelectric switch or optical communication, there is not much problem because the noise pulse generated from the photoelectric conversion unit itself is used with its sensitivity lowered so as not to be disturbed at all. However, when we try to detect weak light such as partial discharge light, we try to find out the failure of electrical equipment at an early stage.
The sensitivity is high so that even if one photon is input to the photoelectric conversion unit, it can be detected. Therefore, removal of intermittent electrical noise pulses generated from the opto-electrical conversion unit itself at intervals of several seconds to several minutes has been a very important issue.

As described above, the partial discharge has the property of being generated in a pulsed manner. When the high voltage applied to the electric device has a commercial frequency, the partial discharge pulse is generated in synchronization with the voltage waveform or in a completely random manner. When the partial discharge is generated in synchronization with the voltage waveform as in the former case, the electric noise pulse is removed by averaging the electric pulse signal of the partial discharge as shown in the device of FIG. Can be done.

FIG. 6 is a block diagram showing the structure of a conventional partial discharge detection apparatus for gas-insulated equipment. Gas insulation equipment 1
Is equipped with an airtight container 2 in which SF ₆ gas is sealed, and the light-tight terminal 5 penetrates the airtight container 2. An electric device (not shown) is housed inside the closed container 2. The output side of the light-tight terminal 5 is connected to the photoelectric conversion unit 6 via the optical fiber cable 11. Further, the output side of the photoelectric conversion unit 6 is connected to the comparison unit 8 including the setting device 10 via the averaging processing unit 7, and the output side of the comparison unit 8 is connected to the notification unit 9.

In FIG. 6, the light-tight terminal 5 is a closed container 2.
For example, it receives the partial discharge light 4 generated at the failure point 3 inside.
However, the light 4 is guided to the outside of the closed container 2. did
Therefore, the partial discharge light 4 propagates through the optical fiber cable 11.
Then, it is input to the photoelectric conversion unit 6. Photoelectric conversion unit 6
The minute discharge light 4 is converted into an electric signal. The averaging processing unit 7 is photoelectric
The commercial frequency applied to the electric equipment by the output signal of the gas conversion unit 6
Averaging process over a specified number of cycles in synchronization with voltage
And output. The comparison unit 8 receives a signal of the averaged electric signal.
The bell is set to a level V preset by the setter 10.₀When
Compare and level V ₀Only electrical signals at higher levels
Is output. When the notification unit 9 receives the output signal of the comparison unit 8,
The electric device is informed that a partial discharge has occurred.

FIG. 7 is a time chart showing an example of signal processing in the apparatus of FIG. The horizontal axis represents time, and the vertical axis represents voltage or signal level. The top waveform 1S is
It is a high voltage waveform applied to electrical equipment, which is 2 from the top.
The waveform 4S at the stage is an optical signal waveform of partial discharge input to the photoelectric conversion unit 6. Further, the waveforms 6S, 7S, 8S in the third, fourth, and lowest stages from the top are all electrical signal waveforms, and the waveform 6S in the third stage from the top is the output signal of the photoelectric conversion unit 6, respectively. The waveform 7S at the fourth stage from the top is the output signal of the averaging processor 7, and the waveform 8S at the bottom is the output signal of the comparator 8.

In FIG. 7, when a commercial frequency voltage such as the waveform 1S is applied to the electric equipment, the waveform 4S of the second stage is applied.
As described above, it is assumed that the partial discharge optical pulse signal 4A is generated in synchronization with the positive and negative cycles of the waveform 1S. That is, two optical pulse signals 4A are generated at almost the same phase every half cycle of the waveform 1S. Photoelectric conversion unit 6
(FIG. 6) receives the optical pulse signal 4A and the waveform 6S at the third stage
It is converted into an electric pulse signal 4B and output. However, at the same time, the above-mentioned electrical noise pulse 6B is randomly generated from the photoelectric conversion unit 6. The peak values of the electric pulse signal 4B and the electric noise pulse 6B in the waveform 6S are all the same because the photoelectric conversion unit 6 has a square wave shaping circuit inside. That is, all the pulsed signals have the same peak value and are shaped into a square wave of the same shape before outputting the signals. FIG.
The partial discharge detection device is for detecting whether a partial discharge has occurred in the closed container 2. Even with partial discharges of the same size, the light quantity of the partial discharge light 4 entering the light-tight terminal 5 differs depending on the position of the failure point 3. But GIS
Since gas-insulated equipment such as does not generate partial discharge in a normal state, even if the level is small, the occurrence of partial discharge indicates an abnormality of the equipment. Therefore, the performance required of the detector for detecting it is not required to be able to measure the magnitude of partial discharge above a certain level. Therefore, the partial discharge light detection method is an effective means for detecting an abnormality in gas insulation equipment such as GIS.
Therefore, the partial discharge detection device of FIG. 6 is not designed to measure the magnitude of partial discharge. Therefore, the optical-electrical converter 6 outputs electrical pulse signals having the same waveform.

Further, the averaging processing unit 7 (FIG. 6) outputs the input signal by a predetermined number of cycles (eg, for each interval Δt in synchronization with the waveform 1S (commercial frequency voltage) of FIG. 7). The average value of the peak values is obtained over 5 cycles, and a signal having a peak value proportional to the average value is output. The electric pulse signal 4B in the waveform 6S in FIG. 7 is generated at the same phase every cycle. Therefore, even if the electric pulse signal 4B is averaged for a period of 5 cycles, its peak value does not change at all. On the other hand, the electrical noise pulse 6B is randomly generated, and thus the peak value becomes 1/5 if the averaging process is performed for the period of 5 cycles. Therefore, the peak value of the electrical noise pulse 6C in the waveform 7S at the fourth stage in FIG. 7 is one fifth of the peak value of the electrical pulse signal 4C.

Further, when the comparator 8 (FIG. 6) is set to the level V ₀ as shown by the waveform 7S in FIG. 7 by the setter 10, all the electrical noise pulses 6C are removed.
As a result, the comparison unit 8 outputs a signal including only the electric pulse signal 4D like the waveform 8S at the bottom of FIG. The notification unit 9 (FIG. 6) notifies that partial discharge occurs in the electric device when the electric pulse signal 4D is included in the waveform 8S, for example, by displaying it on the screen or sounding an alarm. To do.

On the other hand, in the gas-insulated equipment, partial discharge may occur randomly without being synchronized with the voltage waveform as described above. The metallic foreign matter existing in the closed container makes a jumping motion due to the electrostatic force due to the applied electric field, and also causes partial discharge with an irregular phase. When the partial discharge occurs randomly without being synchronized with the voltage waveform, the signal component due to the partial discharge is also removed by the averaging process in the detection apparatus shown in FIG. The following is a detection device when random partial discharges occur.

FIG. 8 is a block diagram showing the structure of a conventional partial discharge detection apparatus for different gas insulated equipment. The same parts as those in FIG. 6 are designated by the same reference numerals, and repeated description thereof will be omitted. Only the parts different from FIG. 6 will be described below. The light-tight terminal 50 branches the partial discharge light 4 into two optical fiber cables 11. The photoelectric conversion unit 6 is provided at each output end of the optical fiber cable 11.
1, 62 are connected. The output sides of the photoelectric conversion units 61 and 62 are connected to the input terminals of the AND circuit 13, and
The output side of the AND circuit 13 is connected to the notification unit 9.

In FIG. 8, the photoelectric conversion units 61 and 62 are the same as the photoelectric conversion unit 6 in FIG. Further, the AND circuit 13 outputs the electric pulse signal only when the electric pulse signals input from the two input terminals are present at the same time. FIG. 9 is a time chart showing an example of signal processing in the apparatus of FIG. The horizontal axis represents time and the vertical axis represents signal level. Top wave 40
S is an optical signal waveform of partial discharge input to the photoelectric conversion units 61 and 62. Further, the waveforms 61S, 62S, and 13S in the second, third, and lowest stages from the top are all electrical signal waveforms, and the waveform 61S in the second stage from the top is the output signal of the photoelectric conversion unit 61, respectively. The waveform 62S at the third stage from the top is the output signal of the photoelectric conversion unit 62, and the waveform 13S at the bottom is the output signal of the AND circuit 13.

In FIG. 9, when partial discharge occurs, an optical pulse signal 40A is obtained as shown in the uppermost waveform 40S. Although the duration of the optical pulse signal 40A is not constant, it is generally extremely short and is about several ns to several tens of ns. The opto-electric converters 61 and 62 (FIG. 8) receive the optical pulse signal 40A, convert it into electric pulse signals 40B as waveforms 61S and 62S, and output the electric pulse signals 40B. However, the photoelectric conversion unit 6
From 1, 62, the above-mentioned electrical noise pulses 61B, 62
B randomly occurs. The photoelectric conversion units 61 and 62 have the same specifications as each other, but since they are separate devices, the probability that the electrical noise pulses 61B and 62B are simultaneously generated from the devices themselves is extremely low. In addition, each of the signals 40B and 61
B and 62B are all shaped into the same peak value and the same square wave as in FIG.

Further, in FIG. 9, since the AND circuit 13 outputs the signal only when the signal is input at the same time,
Only the electric pulse signal 40C is output as in the waveform 13S at the bottom, and the electric noise pulses 61B and 62B are all removed. As described above, the device of FIG.
Since the one containing only is output to the notification unit 9, it is completely unaffected by electrical noise. In the case of the apparatus shown in FIG. 8, even if partial discharges having the same generation phase occur in each voltage cycle as shown by the waveform 4S in FIG. 7, there is no problem in detecting the partial discharge light. Since the electrical noise pulse is generated at random, only partial discharge can be detected.

FIG. 10 is a block diagram showing the structure of a conventional partial discharge detection apparatus for gas insulation equipment.
The gas insulation device 1 is provided with a hermetically sealed container 2 in which SF ₆ gas is sealed, and a light-tight terminal 50 penetrates the hermetically sealed container 2.
An electric device (not shown) is housed inside the closed container 2. Two optical fiber cables 11 are connected to the output side of the optical hermetic terminal 50, one of the optical fiber cables 11 is directly connected to the input end of the optical combiner 16, and the other is connected via the optical delay device 15 to the optical combiner 15. It is connected to another 16 inputs. Further, in FIG. 10, the output side of the optical combiner 16 is connected to the photoelectric conversion unit 64. The output side of the photoelectric conversion unit 64 is branched into two, and one output side is connected to the input end of the AND circuit 12. The other output side is connected to the other input terminal of the AND circuit 12 via the delay circuit 14. The output side of the AND circuit 12 is connected to the notification unit 9.

In FIG. 10, the light-tight terminal 50 is a container 2
Receive the partial discharge light 4 generated at the failure point 3 inside,
The light 4 is guided to each of the two optical fiber cables 11 outside the closed container 2. One of the partial discharge lights 4 propagates through the optical fiber cable 11 and directly enters the optical combiner 1
6 is input. The other part of the partial discharge light 4 is input to the optical combiner 16 with a delay of time τ by the optical delay device 15. The optical delay device 15 can be composed of only an optical fiber cable, for example. Generally, the propagation speed of light in an optical fiber cable is about 5 ns per 1 m.
Therefore, if an optical fiber cable of 20 m is used as the optical delay device 15, the delay time of the optical pulse signal is 1
It will be 00 ns. That is, the delay time can be arbitrarily set depending on the length of the optical fiber cable. Even if the optical fiber cable becomes long, if it is wound in a disk shape or a cylindrical shape, the overall size does not become so large.

Further, in FIG. 10, an optical combiner 16 combines the optical pulse signals guided by the two fiber cables 11 into one optical pulse signal and outputs the optical pulse signal, which is generally commercially available. . The optical hermetic terminal 50, the optical delay device 15, the optical combiner 16, and the optical fiber cable 11 constitute an optical signal shaping section 100, and an optical pulse obtained by shifting a single optical pulse signal of the partial discharge light 4 by a time τ. It is converted into a signal pair.

Further, in FIG. 10, the photoelectric conversion section 6 is provided.
4 is a photoelectric conversion unit 6, 61, which has been described in detail with reference to FIGS.
It is the same as 62 and is composed of a photomultiplier tube or a photodiode. The delay circuit 14 connected to the output side of the photoelectric conversion unit 64 can delay the electric pulse signal for a predetermined time τ by using, for example, a monostable multivibrator. The AND circuit 12 outputs the electric pulse signal only when the electric pulse signals input from the two input terminals are present at the same time. The notification unit 9 notifies the fact that partial discharge has occurred when an electric pulse signal is input, by a screen display or an alarm.

FIG. 11 is a time chart showing an example of signal processing in the apparatus of FIG. The horizontal axis represents time and the vertical axis represents the signal level. The uppermost waveform 41S is a partial discharge optical signal waveform input from the optical hermetic terminal 50 to the optical combiner 16 via only the optical fiber cable 11.
On the other hand, the second waveform 15S from the top is an optical signal waveform input from the optical hermetic terminal 50 to the optical combiner 16 via the optical fiber cable 11 and the optical delay device 15. The waveform 16S in the third stage from the top is the output signal of the optical combiner 16, the waveform 64S in the fourth stage from the top is the output signal of the photoelectric conversion unit 64, and the waveform 14S in the fifth stage from the top is the output of the delay circuit 14. The signal and the waveform 12S at the bottom are output signals of the AND circuit 12.

The electric pulse signals 41A and 42A in the waveforms 41S and 15S of FIG. 11 are due to the same partial discharge light 4 generated at the failure point 3 (FIG. 10). The peak value of an optical fiber cable slightly decreases as an optical signal propagates. Since a long optical fiber cable is used for the optical delay device 15, the peak value of the optical pulse signal 42A is slightly smaller than that of the optical pulse signal 41A. However, as will be described later, all the signals have the same peak value and are shaped into the same square wave, so there is no problem. In the third stage waveform 16S, the light wave signals 41B and 42B are a pair of signals that are deviated from each other by time τ. Photoelectric conversion unit 64
In FIG. 10, the light wave signal pair 41B, 42B is converted into an electric pulse signal pair 41C, 42C having the same square wave and the same peak value as the waveform 64S in the fourth stage and output. At that time, the electrical noise pulse 64C is also output.

Further, in FIG. 11, the waveform 14 of the fifth step
S is delayed from the waveform 64S by a time τ by the delay circuit 14 (FIG. 10) like the electric pulse signal pair 41D, 42D and the electric noise pulse 64D. Further, since the AND circuit 12 (FIG. 10) receives the waveforms 64S and 14S as input, the electric pulse signals 42C and 41D existing at the same time.
Therefore, only the electric pulse signal 41E is output. Therefore, the waveform 12S at the bottom is only the electric pulse signal 41E, and the electric noise pulse 64D is removed. Since the electric pulse signal 41E is originally generated by the occurrence of partial discharge, the detection time is delayed by τ, but is not affected by the electric noise generated by the photoelectric conversion unit 64 (FIG. 10) at all. The time τ is slightly larger than the duration of partial discharge (several ns to several tens of ns) (for example, 10
0 ns) so that the optical pulse signals do not overlap each other. The pulse width of the electric pulse signals 41C and 42C output from the photoelectric conversion unit 64 in the waveform 64S is set to be smaller than the time τ (for example, 50 ns) so that the electric pulse signals do not overlap each other.

The apparatus shown in FIG. 10 requires only one photoelectric conversion unit 64, which has a low yield and is expensive. Compared with the device of FIG. 8, the optical delay device 15, the optical combiner 16 and the delay circuit 14 are increased, but the latter three can be mass-produced regardless of the yield. Therefore, it does not lead to an increase in manufacturing period or an increase in manufacturing cost. Further, this device is a device that detects whether or not partial discharge has occurred. Therefore, even if the electric pulse signal is delayed by time τ, for example, about 100 ns, there is no problem in practical use. In the case of the device shown in FIG. 10, even if partial discharges having the same generation phase occur in each voltage cycle as shown by the waveforms in FIG. 7, there is no problem in detecting the partial discharges.

[0028]

However, the conventional device as described above has a problem that the noise pulse output from the photoelectric converter is not completely removed. That is, the apparatus shown in FIGS. 8 and 10 has a function of removing electrical noise pulses. However, in the following cases, the electrical noise pulse is mistaken for a partial discharge.

FIG. 12 is a time chart showing another example of signal processing in the apparatus of FIG. 8. No partial discharge is generated, but electrical noise pulses are simultaneously generated from the two photoelectric conversion units 61 and 62. This is the case where 61B and 62B occur. Waveforms 40S, 61S, 62S, 1 in FIG.
3S corresponds to the same as in the case of FIG. In FIG. 12, no signal is seen in the waveform 40S, but electrical noise pulses 61B and 62B from the photoelectric conversions 61 and 62 are simultaneously output as in the waveforms 61S and 62S. Therefore, the output of the AND circuit 13 (FIG. 8) has the waveform 13
The electric pulse signal 13A is output like S, and it is erroneously determined that partial discharge has occurred.

FIG. 13 is a time chart showing another example of the signal processing in the apparatus of FIG. 10, in which no partial discharge is generated, but electrical noise pulses which are shifted from each other by the time τ from the photoelectric conversion section 64. This is the case where 64C and 64E occur. Each waveform 16S, 64S, 14 in FIG.
S and 12S correspond to the same as in the case of FIG.

In FIG. 13, although no signal is seen in the waveform 16S, the electrical noise pulse 64E is generated from the photoelectric conversion 64 with a time τ delayed from the electrical noise pulse 64C as shown in the waveform 64S. Therefore, FIG.
The signals of the waveform 64S and the waveform 14S as shown in FIG.
2 (FIG. 10). Since the electric noise pulse 64E and the electric noise pulse 64D are present at the same time, the electric pulse signal 12A is output to the output of the AND circuit 12 (FIG. 10) like the waveform 12S, and it is erroneous that partial discharge has occurred. To be judged.

In the apparatus of FIGS. 8 and 10, the electric noise pulse is considerably removed as compared with the apparatus of FIG.
A noise pulse may be output, which is an obstacle to detection of partial discharge. In the past, when the frequency of electric pulse generation was high, the measurer used to feel that the discharge was a partial discharge. For that reason, there was a case where an erroneous determination was made.

An object of the present invention is to make it possible to detect the occurrence of partial discharge without error even if an electric noise pulse is output.

[0034]

In order to achieve the above object, according to the method of the present invention, in a gas-insulated device in which an electric device is housed in a light-shielding hermetically sealed container in which an insulating gas is sealed, Is a method of detecting partial discharge by detecting light generated by the method, wherein the average value of the number of pulses per unit time of the electrical noise pulse output from the photoelectric conversion unit when the optical pulse is not generated is No. Is obtained in advance,
The average value Nm of the number of pulses per unit time of the electric pulse output from the photoelectric conversion unit at the time of partial discharge measurement is obtained, and when the average value Nm is larger than the above average No, it is determined that partial discharge has occurred. It is good to let you know.

Further, in order to achieve the above object, according to the present invention, a photoelectric converter for converting an optical pulse generated from a partial discharge into an electric pulse and outputting the electric pulse, and a unit for receiving an output signal of the photoelectric converter. A counter that sequentially counts and outputs the number of pulses generated at each time, an arithmetic unit that stores the output signal of this counter and calculates and outputs the average value Nm of the number of pulses per unit time, and an output signal of this arithmetic unit Is configured to include a determination unit that outputs a signal when the value Nm of the above-mentioned exceeds a predetermined value No, and a notification unit that receives the output signal of this determination unit and reports that partial discharge has occurred in the gas-insulated equipment. It may be done.

According to the method of the present invention, the average value No of the number of electric noise pulses output from the photoelectric conversion unit per unit time is obtained in advance when no optical pulse is generated. Further, the average value Nm of the number of electric pulses output from the photoelectric conversion unit during unit discharge measurement is calculated. When the partial discharge occurs, the electrical pulse output from the photoelectric conversion unit is superposed with the optical pulse due to the electrical noise. Therefore, if partial discharge has occurred, the average value Nm of the number of pulses per unit time output from the photoelectric conversion unit is always larger than the average value No based on only the electrical noise pulse. Therefore, Nm is N
Since it is larger than o, it can be determined that partial discharge has occurred.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments. FIG. 1 is a block diagram showing the configuration of a partial discharge detection device for a gas insulated device according to an embodiment of the present invention. Gas-insulated device 1 is an airtight container 2 containing SF ₆ gas.
The light-tight terminal 5 penetrates through the closed container 2. An electric device (not shown) is housed inside the closed container 2. The output side of the light-tight terminal 5 is connected to the photoelectric conversion unit 6 via the optical fiber cable 11. Further, the output side of the photoelectric conversion unit 6 is provided with a determination unit 10 including a setter 104 via a counter 101 and a calculation unit 102.
3 and the output side of the determination unit 103 is connected to the notification unit 9. Other configurations are the same as the conventional configuration described in FIG. The same portions will be denoted by the same reference symbols and repeated detailed description will be omitted.

In FIG. 1, the counter 101 receives the output signal of the photoelectric conversion unit 6 and sequentially counts and outputs the pulse number r (generation frequency) generated per unit time.
The calculation unit 102 receives the output signal 101S of the counter 101, stores the pulse number r per unit time, calculates the average value Nm of the pulse number r per unit time, and outputs the signal 102S. The determination unit 103 outputs the output signal 103S when the input average value Nm is larger than the predetermined value No set by the setting unit 104. The predetermined value No means that the electrical noise pulse output from the photoelectric conversion unit 6 to the counter 101 is output even without the partial discharge light 4S (optical pulse). In that case, the number of electrical noise pulses per unit time. Is the average value of. The probability of occurrence of the electrical noise pulse output from the photoelectric conversion unit 6 generally follows Poisson distribution.

FIG. 2 is a distribution chart showing the relationship between the frequency of occurrence of electrical noise pulses and the probability. The horizontal axis shows the number of pulses r (occurrence frequency) per unit time, and the vertical axis shows the probability f (r) of occurrence of each occurrence frequency. In FIG. 2, a bar 110 surrounded by dots represents a measurement result, and a bar 111 surrounded by diagonal lines represents a calculation result. In FIG. 2, this actual measurement result 110 is shown in FIG.
At the optical fiber 11 side of the opto-electric converter 6 is shielded,
The output 101S of the counter 101 (in this case, the number of pulses r every 5 minutes, that is, the frequency of occurrence) was sequentially obtained for one hour in a state where the optical pulse did not enter the photoelectric conversion unit 6. Probability f that r occurs for the whole
When (r) is the length of the rod 110, the result is as shown in FIG. In this case, the average value No of the pulse number r generated in 5 minutes was 3.8.

On the other hand, the calculation result 111 in FIG. 2 is obtained by the following Poisson distribution formula.

[0041]

## EQU1 ## f (r) = No ^r · exp (−No) · 100 / r! In this formula 1, f (r) at each occurrence frequency r is calculated to be as shown in FIG. The measured result 110 and the calculated result 111 have very similar tendencies. This means that the electrical noise pulse randomly output from the opto-electric conversion unit substantially follows the Poisson distribution.
The average value No of the occurrence frequency of the electrical noise pulse output from the photoelectric conversion unit depends on the temperature. However, since the photoelectric conversion unit is normally kept at a constant temperature by the temperature controller, the average value N is detected when the partial discharge is detected.
o, that is, the frequency of occurrence of electrical noise pulses is constant.

FIG. 3 is a distribution chart showing the relationship between the occurrence frequency of electric pulses and the cumulative probability. The horizontal axis represents the occurrence frequency r of electric pulses, and the vertical axis represents the cumulative probability F (r). F (r) is
It is a value obtained by sequentially integrating the above-mentioned probability f (r) from r = 0 to each r. The characteristic 112 indicated by the alternate long and short dash line is an example in the case where no optical pulse is generated, and is obtained by integrating the actual measurement result 110 of FIG. On the other hand, the solid line characteristic 113 is an example in the case where a partial discharge occurs. Occurrence frequency r at which the cumulative probability F (r) of the characteristics 112 and 113 becomes 50%
(Average value) is No and Nm, respectively. Characteristic 113 is a partial discharge pulse superimposed on an electrical noise pulse, and its average value Nm is always larger than No. If partial discharge has not occurred, the value of Nm is No.
Matches. Therefore, by comparing the average value Nm with No, it can be known whether or not partial discharge has occurred.

Returning to FIG. 1, the arithmetic unit 102 calculates and outputs the average value Nm from the cumulative probability F (r).
The predetermined value No for the determination unit 103 to compare with Nm may be the value output from the calculation unit 102 when partial discharge has not occurred in advance, and this No may be the set value of the setting unit 104. The value of No is determined by the type of photoelectric conversion unit and the ambient temperature. Therefore, the setting unit 104 is preset to N
If o is stored, the electric noise pulse does not have to be actually measured.

FIG. 4 is a block diagram showing the structure of a partial discharge detection device for a gas insulated device according to a different embodiment of the present invention. Between the AND circuit 13 and the notification unit 9, the counter 101, the arithmetic unit 102, which are the same as those shown in FIG.
8 is the same as the conventional device in FIG. 8 except that the determination unit 103 and the setting unit 104 are provided. Two photoelectric converters 6
1, 62 and the AND circuit 13 significantly reduce the number of generated electric pulse noises, and the characteristic 112 in FIG. 3 shifts to the left side.
It can be determined that the partial discharge has occurred when it becomes larger.

FIG. 5 is a block diagram showing the structure of a partial discharge detection device for a gas insulated device according to a further different embodiment of the present invention. Between the AND circuit 12 and the notification unit 9, the same counter 101 and arithmetic unit 1 as those shown in FIG.
02, a determination unit 103, and a setting unit 104 are interposed, and the same as the conventional device of FIG. Even if the partial discharge light is made into the optical pulse signal pair shifted by the time τ, the number of generated electric pulse noises is considerably reduced, and the characteristic 112 in FIG. 3 is shifted to the left side. Similarly, Nm is No. When it becomes larger, it can be judged that the partial discharge has occurred.

In any of the embodiments shown in FIGS. 1, 3 and 5, even if the partial discharge is continuously generated in each applied voltage cycle as shown in FIG. 7, the partial discharge can be detected. No trouble will occur.

[0047]

As described above, the present invention obtains in advance the average value No of the number of electric noise pulses output from the photoelectric conversion unit per unit time when no optical pulse is generated. Further, the average value Nm of the number of electric pulses output from the photoelectric conversion unit at the time of partial discharge measurement per unit time
Ask for. When Nm is larger than No, it is determined that partial discharge has occurred. As a result, the presence / absence of partial discharge can be reliably determined even when the electrical noise pulse is output from the photoelectric conversion unit.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a partial discharge detection device for a gas insulation device according to an embodiment of the present invention.

FIG. 2 is a distribution chart showing the relationship between the occurrence frequency and probability of electrical noise pulses.

FIG. 3 is a distribution chart showing the relationship between the occurrence frequency of electric pulses and the cumulative probability.

FIG. 4 is a block diagram showing the configuration of a partial discharge detection device for gas-insulated equipment according to a different embodiment of the present invention.

FIG. 5 is a block diagram showing the configuration of a partial discharge detection device for gas-insulated equipment according to yet another embodiment of the present invention.

FIG. 6 is a block diagram showing the configuration of a conventional partial discharge detection device for gas-insulated equipment.

7 is a time chart showing an example of signal processing in the apparatus of FIG.

FIG. 8 is a block diagram showing the configuration of a conventional partial discharge detection device for different gas-insulated equipment.

9 is a time chart showing an example of signal processing in the apparatus of FIG.

FIG. 10 is a block diagram showing the configuration of a conventional partial discharge detection device for gas-insulated equipment.

11 is a time chart showing an example of signal processing in the apparatus of FIG.

FIG. 12 is a time chart showing another example of signal processing in the apparatus of FIG.

13 is a time chart showing another example of signal processing in the apparatus of FIG.

[Explanation of symbols]

101: counter, 102: calculation unit, 103: determination unit,
104: setting unit, r: occurrence frequency, No, Nm: average value of occurrence frequency, 1: gas insulation device, 2: sealed container, 3: failure point, 4: partial discharge light, 5, 50: light-tight terminal, 9: Notification unit, 11: Optical fiber cable, 12, 13: AND circuit, 6, 61, 62, 64: Photoelectric conversion unit, 14: Delay circuit, 15: Optical delay device, 16: Optical combiner

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kiyoshi Fujii 1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Fuji Electric Co., Ltd. No. 1 in Fuji Electric Co., Ltd. (72) Inventor Kiyoshi Kurosawa 4-1, Egasaki-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Electric Power Technology Laboratory (72) Inventor Akira Tanaka, Tsuzuki-ku, Yokohama-shi, Kanagawa 654 Wamachi, Fujitsukasei Co., Ltd. (72) Inventor Yuji Kojima 2-3-5 Higashigotanda, Shinagawa-ku, Tokyo Inside Fujitsutakamizawa Component Co., Ltd.

Claims (2)

[Claims] 1. A method for detecting partial discharge by detecting light generated in a hermetically-sealed container of a gas-insulated device in which an electric device is housed in a light-shielded hermetically-sealed container containing an insulating gas. Unit of the electrical pulse output from the photoelectric conversion unit at the time of partial discharge measurement is obtained in advance by obtaining the average value No of the number of pulses per unit time of the electrical noise pulse output from the photoelectric conversion unit when no pulse is generated. An average value Nm of the number of pulses for each time is obtained, and when the average value Nm is larger than the above average No, it is judged that partial discharge has occurred and the notification is given, and a partial discharge detection method for gas insulated equipment is provided. . 2. An apparatus for carrying out the method according to claim 1, wherein a photoelectric converter for converting an optical pulse generated from partial discharge into an electric pulse and outputting the electric pulse, and a unit for receiving an output signal of the photoelectric converter. A counter that sequentially counts and outputs the number of pulses generated at each time, an arithmetic unit that stores the output signal of this counter and calculates and outputs the average value Nm of the number of pulses per unit time, and an output signal of this arithmetic unit Is configured to include a determination unit that outputs a signal when the value Nm of the above-mentioned exceeds a predetermined value No, and a notification unit that receives the output signal of this determination unit and reports that partial discharge has occurred in the gas-insulated equipment. Partial discharge detection device for gas-insulated equipment, characterized in that