JP4853730B2 - Optical CT application equipment - Google Patents

Description

  The present invention is an optical CT application apparatus that executes a predetermined determination process based on the output of an optical CT, such as an underground accident section detection device or a system accident determination device, and includes an optical fiber included in the optical CT. The present invention relates to a technique for preventing malfunction caused by stress such as vibration or bending applied to a transmission line.

  Optical CT (current transformer) is a current measurement device that uses the Faraday effect, and is not affected by electromagnetic induction noise and can be measured over a wide band compared to winding CT that has been widely used in the power field. It has excellent features such as long-distance signal transmission. As a result, for example, as disclosed in Patent Document 1, the sensor unit is attached to a predetermined position of the underground cable, and the Faraday effect is received according to the current (detected current) flowing through the underground cable detected by the sensor unit. The optical signal is converted into a light intensity signal, transmitted from the optical fiber transmission line to a light receiving unit installed far away, and the received optical signal is converted into an electrical signal corresponding to the detected current by photoelectric conversion, and the signal is processed By doing so, it is applied to an underground accident section determination device or the like that performs system fault determination processing.

In the case of the above underground line accident section determination device, a filter or the like that extracts a frequency band in the vicinity of the fundamental wave component (for example, 50 Hz) is used, and the sensor output is input to the filter. Presence / absence can be determined.
JP 2006-46978 A

  By the way, if strong vibration or extreme bending (allowable bending radius (for example, 5 cm or 3 cm) or less) occurs in the core portion of the optical fiber transmission line, the progress of the optical signal in the optical fiber is hindered, and the Faraday effect of optical CT. Unnecessary output generated due to vibration or bending is transiently superimposed on the output of. If the unnecessary output becomes excessive, there is a possibility that an error of a device that processes the output increases and an unnecessary operation is caused. As a result, there is a risk of erroneously detecting that an accident has occurred even in a steady state where no accident has occurred.

  For example, in the case of the above system fault determination process, the optical fiber transmission line connected to the sensor unit is bundled and wired together with the optical fiber transmission line installed for other purposes. Therefore, when performing maintenance etc. on an optical fiber transmission line used in a system different from the underground accident section determination device that performs system accident determination processing, the optical fiber transmission for the underground accident section determination device is mistakenly performed. The vibration caused by the maintenance work caused by the maintenance work on another optical fiber transmission line even if it is in contact with the road and causes vibration or bending, or even if it does not come in direct contact. There is a risk of transmission to a fiber transmission line. Then, an abnormal output is generated due to vibration or bending with respect to the optical fiber transmission line, which may cause malfunction.

  Even if a malfunction occurs due to the above causes, when the maintenance work is completed, there will be no bending or vibration on the optical fiber transmission line, and there will be no abnormal output. It will be difficult to do.

  An object of the present invention is to provide an optical CT application apparatus capable of preventing malfunction caused by stress such as vibration or bending applied to an optical fiber transmission line included in an optical CT.

  The present inventors have verified a distortion waveform that is transiently generated in the optical CT output when strong vibration or extreme bending occurs in the core portion of the optical fiber transmission line that causes erroneous detection, and is about 20 Hz or less. It was possible to identify that there are many low frequency components. The low frequency includes a few Hz such as 2 Hz and 5 Hz, and the high frequency in the low frequency component may be 25 Hz. That is, the upper limit of the low frequency component is not just 20 Hz but includes a slightly higher range. In any case, the signal is in a frequency band lower than the fundamental wave component (for example, 50 Hz). Therefore, the magnitude of the fundamental wave component is compared with the magnitude of the low frequency component of about 20 Hz or less, and when the ratio of the low frequency component increases, a predetermined process for preventing malfunction (the process itself) And stop the output (locked to the safe side). Specifically, this can be realized by adopting various configurations shown below. In order to achieve the above-described object, the present invention adopts configurations described in the following (1) to (4).

(1) An optical CT application apparatus that executes a predetermined determination process based on the output of the optical CT, and is arranged in parallel with a determination unit that executes the predetermined determination process and the processing unit. The low frequency extraction means for extracting a low frequency component lower than the fundamental component from the output, the determination means for determining whether the output of the low frequency extraction means is larger than the steady state, and the result of the determination means And a means for invalidating the determination result of the determination means when larger than the steady state.

  The determination means corresponds to the system fault determination processing unit 12 such as 87G relay and relay element of the embodiment. The determination means corresponds to the content rate determination unit 14 and the low frequency content rate detection unit 24 of the embodiment. The invalidating means corresponds to the AND elements 16 and 18 in the embodiment. In the embodiment, both the determination means and the output of the determination means are input to the AND element, so that even if stress is applied and the determination means may make an erroneous determination, the determination means performs the determination process, but the determination result Is not output (leaves in a steady state / normal state), but the determination process itself may be stopped.

  In addition, the optical CT application device measures, for example, the current flowing through the underground line and the like, and determines whether there is a ground fault (detection of an accident section by using a plurality of optical CTs) or the like. It can be realized by various devices other than an underground line accident zone detection device or the like or a protection relay device.

(2) the determination means is for performing a system fault determination on the basis of the fundamental wave component extracted from the output of the optical CT, the determining means determines the content of the low-frequency component to the fundamental wave component It can be configured to make a determination based on the content rate.

  (3) The determination means performs determination processing based on outputs of a plurality of light CTs, and the low frequency extraction means and the determination means are connected to the outputs of the respective light CTs, and at least 1 When it is determined that the output of the determination unit connected to the outputs of the two optical CTs is larger than the steady state, the determination result of the determination unit can be invalidated.

(4) the determination means includes a current differential relay for performing the determination process based on the difference between the outputs of the plurality of optical CT, the low frequency extracting means, the low from said difference output of outputs of the plurality of optical CT The frequency component can also be extracted. In this way, even if there are a plurality of light CTs, it is sufficient to prepare one set of low-frequency extraction means and determination means, so that the configuration is simplified.

  In the present invention, it is possible to prevent malfunctions caused by stress such as vibration and bending applied to the optical fiber transmission line included in the optical CT.

  FIG. 1 shows an example of a system including an optical CT and an optical CT application apparatus. In this example, the optical CT application apparatus is applied to an accident determination apparatus that performs system fault determination. As shown in FIG. 1, this system includes an optical CT1 and an accident determination device 10 that determines the presence or absence of a system fault based on the output of the optical CT1.

  The optical CT 1 includes a sensor unit 2 disposed so that the underground power transmission line 9 to be inspected penetrates, and two optical fiber transmission lines (first optical fiber transmission line 3a, first optical fiber transmission line 3a connected to the sensor unit 2). 2 optical fiber transmission line 3b). The first optical fiber transmission line 3a is connected to a three-port spectroscopic element 4 composed of an optical circulator. The other port of the spectroscopic element 4 includes a light source 5, a first light receiving element 6a serving as a photoelectric converter, Is connected. A second light receiving element 6b, which is a photoelectric converter, is connected to the second optical fiber transmission line 3b. An averaging processing unit 7 is connected to the outputs of the light receiving elements 6a and 6b, and a value (voltage value) obtained by averaging the outputs of the light receiving elements 6a and 6b is used as the output of the light CT1. The first and third light receiving elements 6a and 6b and the averaging processing unit 7 constitute a photoelectric converter 8. Further, the spectroscopic element 4, the light source 5 and the photoelectric converter 8 are installed at an appropriate distance from the sensor unit 2 and are usually arranged in the vicinity of the accident determination device 10.

  As the light source 5, a light source (ASE) using a phenomenon in which spontaneous emission light generated by exciting a rare earth element-added fiber with an excitation light source such as a semiconductor laser is amplified as it is guided in the fiber is used. The first and second optical fiber transmission lines 3a and 3b use single mode optical fibers. ASE has features such as a large output light quantity (several tens of mW), low temporal coherence, and high spatial coherence, and is suitable as a light source for optical CT (current sensor). In addition, since the degree of polarization of the output light is small, it is excellent as a light source in an optical CT using an optical fiber transmission line composed of a single mode fiber. As disclosed in Patent Document 1, a configuration in which a depolarizing element is interposed in the optical fiber transmission line (between the spectroscopic element 4 and the first optical fiber transmission line 3a) may be adopted. Since the degree is small, depolarization by the depolarizing element becomes easy.

  The spectroscopic element 4 is composed of a polarization-independent circulator. The spectroscopic element 4 supplies light emitted from the light source 5 to the first optical fiber transmission path 3a, and supplies light input from the first optical fiber transmission path 3a to the first light receiving element 6a. At this time, by using a polarization-independent circulator as the spectroscopic element 4, light input from each port can be output to a predetermined port without changing the polarization state and intensity of the light.

  Therefore, according to this light CT1, when the light emitted from the light source 5 is given to the spectroscopic element 4 made of an optical circulator, the light is supplied to the first optical fiber transmission line 3a. The light propagated through the first optical fiber transmission line 3 a is incident on the sensor unit 2.

  The sensor unit 2 uses the Faraday effect to change the rotation angle of the polarization azimuth of the light depending on the magnitude of the magnetic field generated by the current flowing through the underground transmission line 9 to be inspected into the two light beams. It is converted into intensity and emitted. One optical signal is incident on the first optical fiber transmission line 3 a, propagated through the first optical fiber transmission line 3 a, and is incident on the first light receiving element 6 a via the spectroscopic element 4. The other optical signal enters the second optical fiber transmission line 3b, propagates through the second optical fiber transmission line 3b, and enters the second light receiving element 6b. Thereby, the two output lights (light according to the detected current value) emitted from the sensor unit 2 are converted into voltages according to the light intensity by the two light receiving elements 6a and 6b, and the average value thereof is converted. By setting the final output voltage, high-precision measurement can be performed.

  For example, the configuration shown in the embodiment of Patent Document 1 and the conventional example can be applied to the specific structure of the sensor unit 2, and other configurations can of course be employed. Similarly, the optical CT can take various configurations in addition to the configuration shown in FIG. 1 and the one disclosed in Patent Document 1.

  The accident determination apparatus 10 arranges the fundamental wave extraction filter 11 and the system fault determination processing unit 12 in series with respect to the output of the light CT1 (voltage corresponding to the detected current). The fundamental wave extraction filter 11 is a filter that extracts a frequency component around 50 Hz that is a fundamental wave component.

  The system fault determination processing unit 12 determines the presence or absence of a system fault based on the output signal that has passed through the fundamental wave extraction filter 11. Basically, based on the presence or absence of a signal of a 50 Hz component that occurs at the time of a system fault, judge. Therefore, as a simple determination algorithm, a threshold value is set, and the output of the fundamental wave extraction filter 11 is compared with the set threshold value. If the threshold value is greater than or equal to the threshold value, it is determined that a system fault has occurred. It can be determined that no accident has occurred. Of course, it can be realized by various determination algorithms such as extracting feature values from the output waveform of the fundamental wave extraction filter 11 and determining based on the extracted feature values.

  The accident determination apparatus 10 of the present embodiment is provided with a low frequency extraction filter 13 so that the output of the light CT1 is given not only to the fundamental wave extraction filter 11 but also to the low frequency extraction filter 13. The low frequency extraction filter 13 is a filter that extracts a frequency component of about 20 Hz or about 20 Hz or less, for example. When stress such as vibration or extreme bending that is less than the allowable bending radius is applied to the optical fiber transmission lines 3a and 3b, a signal of about 20 Hz (for example, 5 to 30 Hz) is superimposed on the detection current signal from the optical CT1. Is output. Therefore, the low frequency extraction filter 13 has a filter characteristic that extracts a frequency component of about 20 Hz generated when stress is applied to the optical fiber transmission line and does not extract a frequency component of 50 Hz that is a fundamental wave. It was supposed to be. The low frequency extraction filter 13 preferably has a filter characteristic that cuts off a frequency component of 50 Hz. However, a frequency component of 50 Hz may pass through due to the performance of the filter or the like, and the fundamental wave is 50 Hz. However, the output of the light CT1 in the steady state may not be exactly 50 Hz but may be within a certain range of dispersion. In this case, even if the low frequency extraction filter 13 cuts off 50 Hz, In some cases, the low frequency extraction filter 13 may extract a frequency component within the range of the variation of. However, in any case, the output of the fundamental wave extraction filter 11 is large (the output of the low frequency extraction filter 13 is small) in the frequency component of 50 Hz due to the relationship of the filter characteristics (gain).

  The frequency component of about 20 Hz passes through the fundamental wave extraction filter 11, but the output of the low frequency extraction filter 13 is large (the output of the fundamental wave extraction filter 11 is small) for the low frequency component of about 20 Hz. .

  Further, the low frequency extraction filter 13 can be configured by either an analog filter or a digital filter. However, the stress on the optical fiber transmission line to be detected this time is temporarily applied and then returns to the normal state, so the response is good and the transient response is the same as the fundamental wave extraction filter to be paired. Preferably there is.

  Furthermore, in the present embodiment, the content rate determination unit 14 is provided after the low frequency extraction filter 13. This content rate determination unit 14 receives the output of the low frequency extraction filter 13 and the output of the fundamental wave extraction filter 11, and the ratio of the output of the low frequency extraction filter 13 in the output of the fundamental wave extraction filter 11 (low frequency extraction) Filter output / fundamental wave extraction filter output), and determines whether or not the obtained value exceeds the threshold value, and if it exceeds the threshold value (the output of the low frequency extraction filter 13 (low frequency component is large)) A detection signal (High) is output.

  The output of the content rate determination unit 14 is inverted via the NOT element 15 and input to one input terminal of the AND element 16. Further, the output of the system fault determination processing unit 12 (at the time of an accident: High) is input to the other input terminal of the AND element 16.

  As a result, in a steady state in which no stress such as vibration or extreme bending is applied to the optical fiber transmission line, the output of the low-frequency extraction filter 13 is small, so the output of the content rate determination unit 14 is Low, and the AND element 16 One input terminal is High. Therefore, the output of the AND element 16 is Low when there is no system fault, that is, when there is no system fault, and is High when a system fault occurs. Therefore, based on the output of the AND element 16, the protection system (not shown) executes a predetermined process at the time of a system failure.

  On the other hand, when stress such as vibration or extreme bending is applied to the optical fiber transmission line, the output of the low frequency extraction filter 13 increases, and when the amount exceeds a certain amount, the output of the content rate determination unit 14 is It becomes High (abnormality detection), and one input terminal of the AND element 16 becomes Low. Therefore, normally, when the stress is divided in this way, the output of the fundamental wave extraction filter 11 also exceeds a certain amount, and the system fault determination processing unit 12 erroneously determines that there is a system fault (the other of the AND element 16). However, the output of the AND element 16 is kept low, and it is possible to prevent the protection system (not shown) from executing a predetermined process at the time of a system fault based on the erroneous determination.

  FIG. 2 shows another embodiment of the present invention. In the present embodiment, an example in which each extraction filter is realized by a digital filter is shown. In FIG. 2, the light CT1 schematically shows the sensor unit 2, the two optical fiber transmission lines 3a and 3b, and the photoelectric converter 8. However, as in FIG. Elements and components are also mounted.

  In the accident determination device 10, the fundamental wave extraction filter 11 of the embodiment shown in FIG. 1 includes a 50 Hz extraction digital filter 11 a and a 90 ° product calculation unit 11 b, and the system accident determination processing unit 12 is a current differential relay. (87G relay). As is well known, the current differential relay is turned on when the difference between two input values is greater than or equal to a reference value. Accordingly, although not shown, there is a system (fundamental wave extraction filter 11) that receives at least one other optical CT output, and the output of the fundamental wave extraction filter 11 of that system is also supplied from another input terminal of the 87G relay. Is done.

  The filter characteristic of the 50 Hz extraction filter 11 a is, for example, “50 Hz DF” shown in FIG. 3, and peaks around 50 Hz, and the gain of 0 Hz (DC component) is 0, that is, is cut off. The calculation process in the 90 ° product calculation unit 11b is a process of squaring data for every 90 ° electrical angle and adding two points, thereby obtaining an amplitude value. The system fault determination process using the current differential relay will be described later.

  On the other hand, a low frequency component included in the output waveform of the optical CT1 is extracted, and a low frequency for locking the output of the system fault determination processing unit 12 (87G relay) when the extracted component exceeds a predetermined content rate. The lock unit 20 is configured by serially connecting an addition filter 21, an integration filter 22, a product calculation processing unit 23, a low frequency content rate detection unit 24, and a lock determination timer 25. Both filters 21 and 22 are realized by digital filters. The output of the optical CT1 is A / D converted at a predetermined sampling period by an A / D converter (not shown), and the digital value is stored in the data memory in the order of sampling. Therefore, each filter performs a filtering process by reading predetermined data stored in the data memory and performing an arithmetic process. In addition, the calculation results calculated by each processing unit are also stored in the memory separately in time series.

The addition filter 21 executes a filter of K = 6, that is, a process of adding the current value and the previous six values. Thus, if the current (nth) output value of the light CT1 is An, the output Bn of the addition filter 21 is
Bn = An + A (n−6)
It is calculated by.

The integration filter 22 executes a process of adding a filter with K = 5, that is, the current value and data for the past five times. As a result, the output Cn of the integration filter 22 is
Cn = Bn + B (n-1) + B (n-2) + B (n-3) + B (n-4) + B (n-5)
It is calculated by.

  A filter that extracts a low frequency component (including a direct current component) and cuts off (suppresses) a frequency component of about 50 Hz, like the low frequency extraction filter 13 shown in FIG. 1, by the two filters 21 and 22 connected in series. Can be configured. As shown in FIG. 3, the filter characteristic “DC DF” of the two filters as a whole has a peak near 0 Hz (DC component), and the gain at 50 Hz is 0, that is, is cut off.

  Further, the product calculation processing unit 23 connected to the subsequent stage of the integration filter 22 substitutes the output Cn of the integration filter 22 into the following formula to calculate Dn.

Dn = root (Cn * Cn-C (n-3) * C (n-3))
That is, this product calculation is a 90 ° product calculation process, and the amplitude of the signal output from the integration filter 22 is obtained. As described above, the product calculation processing unit 23 is configured using the same algorithm as the product calculation for 50 Hz component detection. The low frequency content detection unit 24 in the next stage uses the 50 Hz component and the low frequency in the transient response. This is because the ratio can be obtained with high accuracy by calculating using the amplitude used in the same algorithm in order to obtain the ratio with the component.

  The low frequency content rate detection unit 24 and the lock determination timer 25 correspond to the content rate determination unit 14 shown in FIG. The low ambient content detection unit 24 calculates a ratio between the 50 Hz component given from the 90 ° product calculation processing unit 11b and the low frequency component given from the product calculation processing unit 23, and performs threshold processing on the obtained ratio. To do. In this embodiment, as shown in FIG. 3, the filter characteristic “50 Hz DF” of the 50 Hz extraction digital filter 11a and the filter characteristic “DC DF” of the low frequency extraction digital filter (addition filter 21 + integration filter 22) Since the gains of the respective peaks are different such as “6.6721” and “12”, the ratio cannot be obtained simply as it is. Therefore, in the present embodiment, the filter characteristic of the low-frequency 50 Hz extraction digital filter is corrected by multiplying the reciprocal of the peak ratio by “12 / 6.6721”, and the corrected value and the low frequency The ratio with the output of the extraction filter was calculated.

In particular,
“DC DF gain” / “50 Hz DF × (12 / 6.6921)”
Ask for. Then, the frequency characteristic of this ratio is as shown in FIG. That is, in the case of 50 Hz, since the output (DC DF gain) of the low frequency extraction filter from the filter characteristic “DC DF” shown in FIG. 3 is “0”, the above ratio is also “0”. Then, a value close to 0 is taken around 50 Hz, and when the frequency becomes low, the output (DC DF gain) of the low frequency extraction filter becomes large and “50 Hz DF × (12 / 6.6921)” becomes small. Increase exponentially.

In this embodiment, the threshold value serving as a comparison reference of “DC DF gain” / “50 Hz DF × (12 / 6.6721)”, which is the content of the low frequency component, is set to 0.5. This
Low frequency component / 50 Hz component (after correction)> 0.5
Then, it can be said that a signal of 30 Hz or less, which is a low-frequency component, is included (content ratio is increased). Therefore, the low frequency content rate detection unit 24 outputs an abnormal signal (switched from Low to High) when the obtained ratio exceeds 0.5.

  The lock determination timer 25 monitors the output of the low-frequency content rate detection unit 24, and when an abnormal signal is continuously output for a certain time (for example, 20 ms), the vibration determination to the optical fiber transmission line to be detected It is determined that bending or the like has occurred, and is locked (output is high). As a result, one input terminal of the AND element 18 becomes Low, and the output of the AND element 18 remains Low regardless of the output of the current differential relay (87G relay) 12. Once locked, the state is held for a certain time (for example, 1 second), and then the lock is released (the output is set to Low). Thus, for example, even when the calculated content rate is in the vicinity of the threshold, frequent ON / OFF switching is prevented, and stable operation is performed.

  5 and 6 are graphs showing experimental results in the apparatus of the embodiment shown in FIG. 2 described above. In each graph, the output of optical CT (photocurrent sensor), 50 Hz component detection amount (output of 50 Hz extraction digital filter), and low frequency suppression detection amount (output of low frequency extraction digital filter) were measured. FIG. 5 is a detection waveform when a normal system fault occurs. The output of the optical CT has a clean waveform with a constant amplitude, and a large number of 50 Hz components superimposed thereon are superimposed, and a low frequency component is small. Judging from this figure, for example, by setting a threshold value of about 4 V for the output of 50 Hz component, it is possible to determine whether or not a system fault has occurred.

  FIG. 6 shows a detection waveform when no system failure occurs and stress such as vibration or bending is applied to the optical fiber transmission line. Since the range of the voltage on the vertical axis is different from that in FIG. 5, the output of the optical CT appears to vibrate greatly, but actually, it pulsates greatly in the state of a vibration waveform with an appropriate amplitude as in FIG. . Further, since the absolute amount of the 50 Hz component detection amount is also large, the determination result of the system fault determination processing unit 12 is an accident occurrence as it is. As shown in FIG. 6, it can be confirmed that the low frequency suppression detection amount takes a very large value and the content rate of the low frequency component increases as compared with the 50 Hz component detection amount. And in the example of FIG. 5, the content rate of a low frequency component becomes small. Therefore, as described above, it was confirmed that the presence or absence of abnormality can be determined based on the content rate of the low frequency component.

  In the case of FIG. 5, the determination result of the system fault determination processing unit 12 is that there is an accident (High), and the output of the low frequency lock unit 20 is Low, so that the output of the AND element 18 is High, Processing at the time of the accident occurred. On the other hand, in the case of FIG. 6, the determination result of the system fault determination processing unit 12 erroneously determines that there is an accident (High), but since the output of the low frequency lock unit 20 becomes High, the final result Since the output of the AND element 18 is Low, it is possible to suppress erroneous execution of the processing when the system fault occurs.

  FIG. 7 illustrates another embodiment of the present invention. In this example, an apparatus is shown in which a determination process is performed by the relay element 12 based on outputs of a plurality (two in the figure) of light CT1. An appropriate relay element 12 is selected according to the content of the determination process. Further, in FIG. 7, as in FIG. 2, the optical CT 1 is illustrated with only the sensor unit 2, the two optical fiber transmission lines 3 a and 3 b, and the photoelectric converter 8, but as illustrated in FIG. It has other optical elements and parts. In addition, the device side that performs the determination process based on the outputs of the plurality of optical CT1 is described as a representative of the relay element 12, but other components (such as a filter) are appropriately positioned according to the determination content. May be placed.

  As shown in the figure, the low-frequency lock units 20 are prepared by the number of the light CT1 and connected to each. Then, the outputs of the plurality of low-frequency lock units 20 are connected to the input terminal of the OR element 26, and the output of the OR element 26 is inverted and input to one input terminal of the AND element 18. As a result, when stress such as vibration or extreme bending is applied to the optical fiber transmission line of at least one light CT1, the quality of the corresponding low-frequency lock unit 20 becomes High. Becomes High, is inverted, and Low is input to the AND element 18. Therefore, even if the relay element 12 malfunctions due to such stress, the output of the AND element 18 becomes Low, so that the influence on the outside can be suppressed.

  FIG. 8 shows yet another embodiment. In the present embodiment, the location where a system fault occurs (failure section) is detected, which is based on the embodiment shown in FIG. That is, the two sensor portions 2 of the light CT1 are respectively mounted at appropriate positions on the monitoring target such as the underground line at a certain distance. If the underground line has not caused a ground fault, etc., the magnitude of the current flowing through the underground line is not so different, but if a ground fault has occurred between the two sensor units In this case, current flows upstream from the accident point, but current does not flow downstream from the accident point, and the outputs of the two light CTs are greatly different. Therefore, whether or not an accident has occurred can be determined based on whether or not the output of the optical CT is greatly different. For this reason, the current differential relay element (87G relay) 12c is used.

  More specifically, the outputs of the two lights CT1 are given to the differential current calculation unit 12a, the difference between them is calculated, and the calculation result is given to the current differential relay element 12c. The current differential relay element 12c is turned on (determined that a ground fault or the like has occurred) when the output of the differential current calculation unit 12a is larger than the set value. The set value of the comparison reference may be a fixed value, but in the present embodiment, it is varied according to the output of the suppression current calculation unit 12b. The suppression current calculation unit 12b adds the outputs (scalar amounts) of the two lights CT1, and uses X% of the added outputs as a set value. When the suppression current calculation unit 12b is provided in this manner, the allowable error range increases as the current value increases. These basic configurations and operating principles are the same as in the prior art.

  The low frequency lock unit 20 is connected to the input terminal branched from the output of the differential current detection unit 12a. According to this configuration, when stress such as vibration or extreme bending is applied to the optical fiber transmission line of at least one optical CT, the influence (superimposition on the signal of the low frequency component) is the differential current detection unit. Since it appears at the output of 12a, only one low frequency lock unit 20 is required, which is preferable.

It is a figure which shows an example of the system containing optical CT and an optical CT application apparatus. It is a figure which shows another example of the system containing optical CT and an optical CT application apparatus. It is a graph which shows the filter characteristic of a digital filter. It is a graph which shows the frequency characteristic of the content rate of the low frequency component with respect to a fundamental wave component. It is a graph which shows an experimental result (at the time of a normal accident). It is a graph which shows an experimental result (when vibration, extreme bending, etc. are added with respect to the optical fiber transmission line). It is a figure which shows an example of the system containing several optical CT and optical CT application apparatus. It is a figure which shows the other example of the system containing several optical CT and optical CT application apparatus.

Explanation of symbols

1 light CT
2 Sensor unit 3a First optical fiber transmission line 3b Second optical fiber transmission line 10 Accident determination device 11 Fundamental wave extraction filter 11a 50Hz extraction digital filter 11b 90 ° product calculation unit 12 System accident determination processing unit 13 Low frequency extraction filter 14 Rate determination units 16, 18 AND element 20 Low frequency lock unit 21 Addition filter 22 Integration filter 23 Product operation processing unit 24 Low frequency content rate detection unit 25 Lock determination timer

Claims (4)

An optical CT application apparatus that executes a predetermined determination process based on the output of the optical CT,
Determination means for executing the predetermined determination processing;
Low-frequency extraction means that is arranged in parallel with the processing means and extracts a low-frequency component lower than the frequency of the fundamental component from the output of the optical CT;
Determination means for determining whether the output of the low frequency extraction means is greater than the steady state;
Means for invalidating the determination result of the determination means when the result of the determination means is greater than the steady state. The determination means performs system fault determination based on a fundamental wave component extracted from the output of the optical CT,
The determining means determines the content of the low-frequency component to the fundamental wave component, the optical CT application apparatus according to claim 1, characterized by being configured to perform the determination based on the content. The determination means performs determination processing based on outputs of a plurality of optical CTs,
The low-frequency extraction unit and the determination unit are connected to the output of each optical CT, and when it is determined that the output of the determination unit connected to the output of at least one optical CT is larger than the steady state The optical CT application apparatus according to claim 1, wherein the determination result of the determination unit is invalidated. The determination means includes a current differential relay that performs a determination process based on a difference between outputs of a plurality of optical CTs,
The low frequency extracting means, optical CT application apparatus according to claim 1 or 2, characterized in that for extracting the low frequency component from the output difference between the outputs of the plurality of optical CT.

Images