Discharge Detection Unit

Abstract

To monitor discharge events occurring in a plurality of phases with a single discharge detection unit.SOLUTION: A discharge detection unit 1 includes: a phase angle setting unit 23 capable of setting a measurement starting point for each phase of a wiring system having different phase angles for each phase; and a determination unit 26 capable of determining in which phase the discharge event is detected based on the timing when noise output was seen or a measurement start point or a determination time period established based on the measurement start point.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electric discharge detection unit. [Background technology]

[0002] As described in Patent Document 1, a structure is known that uses a current sensor or a voltage sensor to extract high-frequency discharge noise superimposed on commercial frequencies. In this example, a high-pass filter extracts noise output in the high-frequency band, and a determination unit determines that a discharge has occurred if the noise level exceeds a threshold value for a certain period of time, and then operates a switching unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-184480

[0004] In wiring systems with multiple phase angles, such as three-phase three-wire and three-phase four-wire systems, the phase angles between RS, ST, and TR are offset. This means that noise manifests at different locations depending on the phase in which a discharge event occurs. Furthermore, noise from discharges can leak into each phase. Therefore, conventional systems using a single discharge detection unit and setting phase angles based on a single power supply waveform may fail to detect the discharge event depending on the phase in which it occurs. This requires the preparation of a discharge detection unit for phase angle control corresponding to each phase, which increases the number of components. Another problem is the need for a separate device capable of performing calculations and judgments to compare and evaluate the received judgment results. Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors of the present invention have made extensive research into this issue and have attempted to solve it. The problem that the present invention aims to solve is to make it possible to monitor discharge events occurring in multiple phases with a single discharge detection unit. [Means for solving the problem]

[0006] In order to solve the above problem, the discharge detection unit includes a phase angle setting unit that can set a measurement start point for each phase of a wiring system having different phase angles for each phase, and a determination unit that can determine in which phase a discharge event has been detected, based on the timing when noise output is observed and the measurement start point or a determination time period defined based on the measurement start point.

[0007] Furthermore, it is preferable that the phase angle setting unit be configured to determine a measurement start point for one phase from the detected waveform, and to determine the measurement start points for other phases by performing calculations to shift the measurement start points by a predetermined time based on the determined measurement start point.

[0008] Furthermore, it is preferable that the phase angle setting unit be configured to be able to determine the measurement start point from the detected waveform of each phase.

[0009] Furthermore, it is preferable that the phase division unit is configured to distinguish between a peak time region including the region before and after the peak at the commercial frequency for the output waveform extracted by the filter unit, and a zero value time region before and after the output at the commercial frequency becomes zero, for each phase, and the determination unit performs a calculation to determine the difference between the output of the peak time region and the output of any zero value time region before and after the peak time region, and determines that a discharge event has occurred in the phase where the difference is equal to or greater than a predetermined first threshold value.

[0010] Furthermore, it is preferable that the phase division unit determines a peak time region for each phase that includes a region before and after the peak at the commercial frequency for the output waveform extracted by the filter unit, and the determination unit is configured to determine that a discharge event has been detected in a phase when the timing at which the noise output was observed and the peak time region match in only one phase.

[0011] Furthermore, the determination unit is preferably configured to notify an external device that determination cannot be made when there are a plurality of phases in which the output at the timing of the zero value time region is equal to or greater than the second threshold value.

[0012] Furthermore, the determining unit is preferably configured to reduce the amplification rate of the output waveform extracted by the filter unit when there are a plurality of phases in which the output at the timing of the zero value time region is equal to or greater than the second threshold value. [Effects of the Invention]

[0013] The present invention makes it possible to monitor discharge events occurring in multiple phases with a single discharge detection unit. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 10 is an image diagram showing an example in which a discharge detection unit is applied to a wiring system. [Figure 2] FIG. 10 illustrates the occurrence of a discharge event. [Figure 3] 10A and 10B are diagrams showing an image of a voltage waveform in each phase and a change over time in the detected value of noise extracted by a filter section corresponding to each phase. [Figure 4] FIG. 10 is a diagram showing an example of measurement start points determined for each phase. [Figure 5] FIG. 10 is a diagram showing an example in which the ST phase measurement start point and the TR phase measurement start point are determined by calculation from the RS phase measurement start point. [Figure 6] FIG. 10 is a diagram showing the measurement start points of noise extracted by the filter sections corresponding to each phase, and the division of the noise into areas A, B, A', and B' from each measurement start point. [Figure 7] This diagram shows the difference between area A and area B of the noise detection value extracted by the filter section corresponding to each phase. On the right side, a table showing the change over time of the area for each phase is shown. [Figure 8] FIG. 10 is a diagram illustrating continuous detection of the difference between peak time regions and zero value time regions. [Figure 9]This is a diagram showing that the difference between the peak time region and the zero value time region continuously satisfies the condition, then stops satisfying the condition once, and then satisfies the condition again. [Figure 10] FIG. 10 is a diagram showing an example in which the amplification factor is changed so that the second threshold is not exceeded in the 0 time region after the second threshold has been exceeded in all phases, and an example in which the third threshold is set. [Figure 11] FIG. 10 is a diagram showing an example in which only the peak time region is used for discharge detection. [Figure 12] FIG. 10 is a diagram showing an example of identifying in which phase a discharge event has been detected by using noise extracted from a filter section set to correspond to one phase. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the invention is described below. As can be seen from Figures 1 to 4, the discharge detection unit 1 of this embodiment includes a phase angle setting unit 23 that can set a measurement start point for each phase of a wiring system having a different phase angle for each phase, and a determination unit 26 that can determine in which phase a discharge event has been detected, based on the timing at which a noise output is observed and the measurement start point or a determination time period defined based on the measurement start point. This makes it possible to monitor discharge events that occur in multiple phases with a single discharge detection unit 1.

[0016] Here, an example in which the discharge detection unit 1 is used in a three-phase, three-wire power distribution system will be described. The discharge detection system of the example shown in Fig. 1 includes a filter unit 21 having a high-pass filter that extracts noise output in the high-frequency band, an amplifier unit 22 that amplifies the output of the filter unit 21, a phase angle setting unit 23 that sets the phase angle that serves as the measurement start point for each phase, a phase division unit 24 that divides the voltage waveform into multiple regions based on the information set by the phase angle setting unit 23, a smoothing unit 25 that performs peak hold on the waveforms output by the amplifier unit 22 and the phase division unit 24, and a determination unit 26 that determines whether the output exceeds a predetermined threshold. All of these units except the filter unit 21 are included in the discharge detection unit 1. The filter unit 21 is configured to be able to extract noise output from at least one phase.

[0017] When multiple phases exist, even if a discharge event occurs in one of the multiple phases, noise may leak into the other phases. For example, even if a discharge event occurs in the ST phase as shown in Figure 2, noise output that passes through filter unit 21 that detects the RS phase and filter unit 21 that detects the TR phase was observed as shown in Figure 3.

[0018] Just by checking that noise has occurred, it is not possible to determine on which phase the discharge noise has been superimposed, so a measurement start point is set for each phase (see Figure 4). For example, the measurement start point can be determined from the detected waveform of each phase. More specifically, the voltage waveform for each phase can be extracted and the measurement start point set. The measurement start point is preferably set at 45° on each voltage waveform. This is the start point of the peak time region, which will be described later.

[0019] It is possible to set the measurement start point without detecting the waveforms of all phases. For example, the measurement start point for one phase can be determined from the detected waveform, and the measurement start points for the other phases can be determined by calculating the measurement start point so that the determined measurement start point is shifted by a predetermined time.

[0020] More specifically, the following procedure can be used. For example, extract only the RS-phase voltage waveform and set the measurement start point for the RS-phase. Then, perform calculations to determine the measurement start points for the other phases. In the case of a delta connection, since the phases are shifted by 120°, assuming one cycle is 16.7 ms, the measurement start point for the ST-phase can be set to a predetermined time (16.7 ms × 1 / 3 after the measurement start point for the RS-phase, for 60 Hz), and the measurement start point for the TR-phase can be set to a predetermined time later (16.7 ms × 2 / 3 after the measurement start point for the RS-phase, for 60 Hz) (see Figure 5).

[0021] The measurement start point can be set by the phase angle setting unit 23. It is preferable that the determination unit 26 compares this measurement start point or a determination time period defined based on the measurement start point with the timing at which a noise output was observed, and determines in which phase the discharge event was detected.

[0022] The examples shown in Figures 2 to 5 relate to outputs in a three-phase, three-wire delta connection, but this is not the only example. For example, a Y connection is also acceptable. If there is a different phase shift, the measurement start point should be set accordingly.

[0023] It is preferable that the phase dividing unit 24 is configured to distinguish between a peak time region including the region before and after the peak at the commercial frequency related to the output waveform extracted by the filter unit 21 and a zero value time region before and after the output at the commercial frequency becomes zero, for each phase.

[0024] Furthermore, it is preferable that the judgment unit 26 is configured to perform a calculation to determine the difference between the output of the peak time region and the output of a zero-value time region either before or after the peak time region, and to judge that a discharge event has occurred in a phase in which the difference is equal to or greater than a predetermined first threshold value.

[0025] The phase dividing unit 24 of the embodiment divides the regions from the measurement start point of each phase to distinguish between a peak time region (region A) before and after the peak point of the voltage waveform (current waveform) and a zero value time region (region B) before and after the zero crossing point of the voltage waveform (current waveform) (see FIG. 6). Then, a calculation is performed to derive the difference C between the output of region A and the output of region B, and the result is used to determine whether a discharge event has been detected.

[0026] 6, "Area A output - B area output = difference C," and if this difference C is equal to or greater than the first threshold, it is determined that a discharge event was detected in the phase from which the result was obtained. That is, it is checked whether "difference C ≧ first threshold." In the example shown in FIG. 6, the difference between the noise detection values ​​of the RS filter unit 21 is a negative value, the difference between the noise detection values ​​of the ST filter unit 21 is a positive value, and the difference between the noise detection values ​​of the TR filter unit 21 is 0. The first threshold is set to a positive value, and in this example, since the difference between the noise detection values ​​of the ST filter unit 21 is equal to or greater than the first threshold, a discharge event was detected in the ST phase.

[0027] In the example shown in FIG. 6, the measurement start point for each phase is set to coincide with the start point of the peak time region, but the measurement start point for each phase may also be set based on the zero cross point at the commercial frequency.

[0028] In the example shown in Figure 6, the output from region A' and region B' are not used to determine whether a discharge event has been detected, but they may be used for the determination. In the example shown in Figure 7, the discharge noise associated with a discharge event can be detected as shown on the left. The right side of Figure 7 shows a summary of which region each phase falls into during a given time period.

[0029] To achieve this, the measurement start point for each phase is first set, and then the peak time region (region A, region A') and zero value time region (region B, region B') of the output of the filter unit 21 for each phase are determined based on the measurement start point.

[0030] To make this determination, the difference (C, C') between the output of the filter unit 21 for each phase in the peak time region and the output of the zero value time region is calculated. Note that "output of region A - output of region B = difference C" and "output of region A' - output of region B' = difference C'".

[0031] In the example shown in Figure 7, the difference (C, C') between the output of the filter unit 21 in the RS phase in the peak time region and the output in the zero value time region is calculated, and the calculation result is compared with the first threshold. Since it can be determined that the difference C is less than the first threshold, it can be determined that a discharge event has not been detected in the RS phase.

[0032] Similarly, when the difference in the region of the output of the filter section 21 in the ST phase is calculated, it can be determined that the difference C derived from "output of region A - output of region B = difference C" reaches the first threshold, and therefore it can be determined that the discharge event was detected in the ST phase.

[0033] Similarly, when the difference in the area of ​​the output of the filter section 21 for the TR phase is calculated, it can be determined that the calculation result is below the first threshold, and therefore it can be determined that a discharge event has not been detected in the TR phase.

[0034] Because of the above results, it can be determined that this discharge event was detected in the ST phase. In this way, one discharge detection unit 1 can determine multiple phases, so each phase can be determined while reducing the number of devices. In this embodiment, the output of the peak time region and the zero value time region are calculated using the sum or average of the set regions.

[0035] In the above example, if a state in which the first threshold value is exceeded is confirmed even once, it is determined that a discharge event has been detected. However, since sudden noise is also possible, it is preferable to determine that a discharge event has been detected when it is determined that the condition is continuously met.

[0036] For example, if the difference C between area A and area B (or the difference C' between area A' and area B') is greater than or equal to a threshold value, it is judged as "1", and the number of times it is judged as "1" during a specified time period set as the discharge judgment time is added up, and if the added value is greater than or equal to a specified value, it is judged to be a discharge event.

[0037] More specifically, for example, the discharge determination time is set to 500 ms. At 60 Hz, one cycle is approximately 16.7 ms, and determination is made once per cycle. If the sum reaches 30 after 500 ms (after 30 consecutive measurements), a discharge event is determined to have occurred. For example, when determining the RS pole using the integrated value of the positive output of the voltage waveform (current waveform), a discharge event may be determined to have occurred when C001 + C003 + C005... + C032 is equal to or greater than a predetermined value. In the embodiment shown in FIG. 8, the integrated value does not exceed the predetermined value, so a discharge event is not determined to have occurred.

[0038] In this way, by comparing the sum values ​​of each phase after the discharge determination time has elapsed and confirming that the suspected event is repeated, it is possible to more accurately determine the phase in which the discharge event has been detected. Note that the discharge determination time can be freely set in the discharge detection unit 1 of the embodiment. In addition, in the example shown in FIG. 8, determination is made using either the difference C or the difference C' for each phase.

[0039] Incidentally, when determining that a discharge event has been detected based on the continuity of an event suspected of being a discharge event, such as by measuring the discharge determination threshold multiple times or by using an integrated value as a condition for determining that a discharge event has been detected, the noise may momentarily attenuate (see FIG. 9). For this reason, it is preferable to implement control that assumes that such an event will occur. For example, in order not to reset the measurement of the discharge determination time even if the noise momentarily attenuates midway, it is preferable to treat the event suspected of being a discharge event as continuing if it is only a momentary drop (attenuation only within the continuity determination time) and continue measuring the discharge determination time without resetting it.

[0040] The continuity determination time is a time during which an event suspected of being a discharge event is treated as continuing even if no event suspected of being a discharge event is detected, and it is preferable to set it as a predetermined range in advance.

[0041] Furthermore, it is preferable that the continuity determination time be measured only when the discharge determination time count has started, and that if the count has not started, the continuity determination time is not determined. In other words, it is preferable that the continuity determination time be measured on the premise that an event suspected of being a discharge event has been detected.

[0042] Even in this case, it is preferable that measurement of the continuity determination time only starts when an output in which the difference between area A and area B, etc., exceeds the first threshold value can be measured multiple times in succession (for a predetermined period of time.) In other words, if an event suspected of being a discharge event occurs repeatedly to a certain extent and then no event suspected of being a discharge event is detected, it is preferable to control so as to check whether this state continues for the continuity determination time.

[0043] If the threshold value drops beyond the set continuity determination time, it is preferable to reset the measurement of the discharge determination time.

[0044] However, when a discharge event occurs and a device that outputs noise is used, noise may be picked up overall. In this case, if a calculation is performed to derive the difference between area A and area B, the result may not exceed the threshold, even though a discharge event has occurred. For this reason, it is preferable to determine whether the output of area B (area B') exceeds a second threshold different from the first threshold, and if it does exceed the second threshold, to control the device so that an external notification is sent to indicate that the determination cannot be made (see Figure 10).

[0045] Furthermore, in the case of a three-phase, three-wire system, noise may leak in. To deal with noise leaks caused by using equipment that outputs noise, it is preferable to notify an external device that a determination cannot be made when there are multiple phases whose output at the timing of the zero-value time region (region B (region B')) is equal to or greater than the second threshold.

[0046] When the output of the B region (B' region) exceeds the second threshold for a certain period of time, it is preferable to reduce the sensitivity and the output waveform. By reducing the gain of the amplifier 22 that amplifies the high frequency signal that has passed through the filter 21, it may be possible to determine whether the output waveform is equal to or lower than the first threshold. In this case, the gain is reduced so that the continuous output waveform is equal to or lower than the second threshold.

[0047] Furthermore, if feedback occurs, it is better to check whether the output at the timing of the zero value time region is equal to or greater than the second threshold for multiple phases. Therefore, if there are multiple phases in which the output at the timing of the zero value time region is equal to or greater than the second threshold, it is preferable to reduce the amplification rate of the output waveform extracted by the filter unit 21.

[0048] If the sensitivity is left lowered even after use of a specific noise-emitting device has ended, the detection range may become narrower or noise associated with discharges may become undetectable. Therefore, after controlling the sensitivity to be lowered to below the second threshold, if the output at the timing of the zero-value time region falls below a third threshold set lower than the second threshold, it is preferable to control the sensitivity to return to the original setting. Note that if the third threshold is used, the output amplification factor should be higher than the third threshold when it is lowered.

[0049] In the above example, the output of the A region (A' region) and the output of the B region (B' region) are used for the judgment, but only the output of the A region (A' region) may be used for the judgment. In other words, it is also possible to use only the peak time region for the judgment without using the zero value time region. In this case, the phase dividing unit 24 simply determines, for each phase, a peak time region that includes the region before and after the peak at the commercial frequency related to the output waveform extracted by the filter unit 21.

[0050] In this case, it is preferable that the determination unit 26 determines that a discharge event has been detected in a phase when the timing at which a noise output was observed and the peak time region match in only one phase. It is also preferable to determine the phase in which a discharge event has been detected by comparing whether the output periods of the peak time regions match.

[0051] Even in this case, the measurement start point is set for each phase. Then, the peak time region (region A, region A') of the output of the filter unit 21 for each phase is determined based on the measurement start point. After that, control is performed to check whether the output of the filter unit 21 matches the output of the peak time region set for each phase and whether the output periods of the peak time region match.

[0052] For example, the output of the filter unit 21 for the RS phase is compared to the output of the peak time region (region A, region A') set for the RS phase to see if they match, or if the periods of the outputs of the peak time regions match. In the example shown in Fig. 11, since there is no output in the peak time region set for the RS phase, it is determined that a discharge event has not been detected in the RS phase.

[0053] Similarly, when it was checked whether the output of the filter unit 21 and the output of the peak time region (region A, region A') set for the ST phase matched, or whether the period of the output of the peak time region matched, it was found that the output of the filter unit 21 and the output of region A, or the output period, matched, and it was therefore determined that a discharge event had been detected in the ST phase.

[0054] Similarly, when it was checked whether the output of the filter unit 21 and the output of the peak time region (region A, region A') set for the TR phase matched, or whether the output period of the peak time region matched, it was found that the output of the filter unit 21 and the output of region A, or the output period, did not match, and therefore it was determined that a discharge event had not been detected in the ST phase.

[0055] From the determination results for each phase obtained in this manner, it can be determined that a discharge event has been detected in the ST phase.

[0056] In this case, it is preferable to consider a discharge event as one in which noise is superimposed on the peak time region in only one phase, and if it is determined that a discharge event has occurred in multiple phases, to determine that the noise is not a discharge event occurring in that phase (or between phases) but rather that it is due to noise influence from an electrical device that is constantly generating noise. Even in this case, it is preferable to be able to notify an external device that a discharge event cannot be determined. It is also preferable to control the sensitivity to be reduced so that a discharge event can be measured.

[0057] In the above-described embodiment, a filter unit 21 is provided for each phase, but in a wiring system where sneak interference may occur, a filter unit 21 may be provided for only one phase. In this case, information is input to the determination unit 26 based on the output waveform output from one filter unit 21 (see FIG. 12).

[0058] As can be seen from the determination logic shown in Fig. 12, one cycle is divided into several parts so that the peak time region and the zero value time region can be distinguished, and it is possible to identify in which phase a discharge event was detected by comparing the time state of each phase with the output waveform output from the filter unit 21. In the example shown in Fig. 12, one cycle is divided into 16 parts.

[0059] In this case, it is preferable to identify the phase in which the discharge event was detected by checking whether the output of the filter unit 21 matches the output of the peak time region (region A, region A') set for each phase, or whether the periods of the output of the peak time region match.

[0060] Although the present invention has been described above using the embodiments as examples, the present invention is not limited to the above embodiments and can be embodied in various forms. For example, the filter section may be provided in the discharge detection unit, or may be separately connected to the discharge detection unit. [Explanation of symbols]

[0061] 1 Discharge detection unit 21 Filter section 22 Amplification section 23 Phase angle setting section 24 Phase division section 25 Smooth section 26 Judgment section

Claims

1. An amplifier section that amplifies the output of the filter section; a phase angle setting unit that can set a measurement start point, which is a phase that is used as a reference for comparison with the timing at which noise output is observed, for each phase of a wiring system having a different phase angle for each phase; a determination unit capable of determining in which phase a discharge event has been detected based on the timing at which a noise output is observed and the measurement start point or a determination time period defined based on the measurement start point; Equipped with The phase angle setting unit is a discharge detection unit that can set the measurement start point from the waveform extracted for each phase.

2. A phase angle setting unit capable of setting a measurement start point, which is a phase used as a reference for comparison with the timing at which noise output is observed, for each phase of a wiring system having a different phase angle for each phase; a determination unit capable of determining in which phase a discharge event has been detected based on the timing at which a noise output is observed and the measurement start point or a determination time period defined based on the measurement start point; a phase splitter; Equipped with the phase dividing unit is configured to distinguish, for each phase, a peak time region including a region before and after a peak at the commercial frequency related to the output waveform extracted by the filter unit, from a zero value time region before and after the output at the commercial frequency becomes zero; The determination unit is a discharge detection unit that performs a calculation to determine the difference between the output of the peak time region and the output of a zero-value time region either before or after the peak time region, and determines that a discharge event has occurred in a phase where the difference is equal to or greater than a predetermined first threshold value.

3. A phase splitter is provided, the phase division unit determines a peak time region including a region before and after the peak in the commercial frequency of the output waveform extracted by the filter unit for each phase; 3. The discharge detection unit according to claim 1, wherein the determination unit determines that a discharge event has been detected in a phase when the timing at which a noise output is observed and the peak time region coincide in only one phase.

4. 4. The discharge detection unit according to claim 2, wherein the determination unit notifies an external device that determination is not possible when there are a plurality of phases whose outputs at the timing of the zero value time region are equal to or greater than the second threshold.

5. A phase angle setting unit capable of setting a measurement start point, which is a phase used as a reference for comparison with the timing at which noise output is observed, for each phase of a wiring system having a different phase angle for each phase; a determination unit capable of determining in which phase a discharge event has been detected based on the timing at which a noise output is observed and the measurement start point or a determination time period defined based on the measurement start point; a phase splitter; Equipped with the phase dividing unit is configured to distinguish, for each phase, a peak time region including a region before and after a peak at the commercial frequency related to the output waveform extracted by the filter unit, from a zero value time region before and after the output at the commercial frequency becomes zero; the determination unit performs a calculation to determine a difference between the output in the peak time region and the output in a zero value time region either before or after the peak time region, and determines that a discharge event has occurred in a phase in which the difference is equal to or greater than a predetermined first threshold value; The determination unit is a discharge detection unit that reduces the amplification rate of the output waveform extracted by the filter unit when there are multiple phases whose output at the timing of the zero value time region is equal to or greater than the second threshold.

Images