Insulation monitoring device

Abstract

To provide an insulation monitoring device capable of detecting a sign of insulation deterioration and further easily identifying the location of insulation deterioration.SOLUTION: An insulation monitoring device includes a first ZCT 2a attached to a lead-in cable 6 to a cubicle 7, a second ZCT 2b attached to an A-class grounding wire 12a of a shielding member 11 of the lead-in cable 6, a third ZCT 2c attached to an A-class grounding wire 12b of a main disconnection device 72 of the cubicle 7, a sign determination unit 4 that determines a sign of insulation deterioration, and a notification unit 5 that gives a notification on a determination result of the sign determination unit 4. The sign determination unit 4 determines that there is a sign of insulation deterioration when one of the second ZCT 2b and the third ZCT 2c, and the first ZCT 2a simultaneously detect a zero-phase current indicating an abnormal value of a certain value or more, and transmits a sign detection signal including the location information of a ZCT 2 that has detected the abnormal value to the notification unit 5.SELECTED DRAWING: Figure 1

Description

【Technical Field】 【0001】 The present invention relates to an insulation monitoring device for preventing in advance ground fault accidents occurring in high-voltage power receiving equipment. 【Background Art】 【0002】 There is a high-voltage ground fault relay as a means for detecting a ground fault of a high-voltage lead-in cable. When a ground fault current flows continuously for 50 msec or more, this high-voltage ground fault relay determines that a ground fault has occurred and performs control to cut off the high-voltage power receiving equipment from the incoming line. In this case, since the high-voltage ground fault relay performs a cutoff operation when it detects a ground fault, there are cases where it is cut off without warning even during load operation, and unexpected situations such as failures of load equipment may occur. As a countermeasure against this, for example, there is the technology disclosed in Patent Document 1. This is a technology that captures a precursor phenomenon before the high-voltage ground fault relay determines a ground fault and issues an alarm. When a zero-phase current of a needle-shaped wave whose current width does not reach 3 cycles is detected a plurality of times within a certain period, it is regarded as a precursor phenomenon, and a ground fault caution signal is output. 【Prior Art Documents】 【Patent Documents】 【0003】 【Patent Document 1】 Japanese Patent Application Laid-Open No. 9-19045 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0004】 The technology of the above Patent Document 1 can take countermeasures before the circuit is cut off because it detects a precursor of a ground fault and outputs a ground fault caution signal before the high-voltage ground fault relay performs a cutoff operation in response to a ground fault. However, it was not possible to detect ground fault currents shorter than 50 msec, especially spike-like ground fault currents of 1 msec or less, and therefore, it was not possible to detect signs of insulation deterioration. Furthermore, although it is necessary to pinpoint the location of insulation deterioration (the location of the ground fault) and take countermeasures after receiving a ground fault warning signal, identifying the location is not easy and is a time-consuming task. 【0005】 Therefore, in view of these problems, the present invention aims to provide an insulation monitoring device that can detect signs of insulation deterioration and facilitate the identification of the location of insulation deterioration. [Means for solving the problem] 【0006】 To solve the above problems, the insulation monitoring device according to claim 1 includes a first zero-phase current transformer attached to a service drop cable to a high-voltage power receiving facility, a second zero-phase current transformer attached to the grounding wire of the shielding member of the service drop cable, a third zero-phase current transformer attached to the Class A grounding wire of the high-voltage equipment of the high-voltage power receiving facility, and a signal converter that converts the zero-phase current output by the zero-phase current transformer into a digital signal. The system includes a prediction unit for determining signs of insulation deterioration and a notification unit for notifying the results of the prediction unit's determination. The signal converter is arranged integrally with or near each zero-sequence current transformer, and the detected zero-sequence current is digitally converted and transmitted to the prediction unit. The prediction unit determines that there are signs of insulation deterioration if it detects zero-sequence currents exceeding a certain value simultaneously in either the second zero-sequence current transformer, the third zero-sequence current transformer, and the first zero-sequence current transformer, and transmits a prediction detection signal to the notification unit, which includes location information of the zero-sequence current transformer that showed the abnormal value. With this configuration, if a zero-sequence current exceeding a certain value is detected simultaneously at multiple locations, including the service drop cable, that is, if ground fault discharges occur simultaneously at multiple locations, including the service drop cable, it is determined that there are signs of insulation deterioration. Therefore, by making a judgment based on ground fault discharges at multiple locations, it is possible to prevent false detections of signs of insulation deterioration and to detect insulation deterioration in high-voltage circuits at an early stage and take action before it leads to a ground fault. Furthermore, since information on the location of ground fault discharge detection is notified, it is possible to limit the affected area, making it easier to pinpoint the location of the fault. In addition, since the information on the zero-sequence current, which indicates an abnormal value above a certain threshold, is digitized and transmitted to the predictive maintenance unit, it is possible to reduce the likelihood of the predictive maintenance unit malfunctioning due to noise. 【0007】 The invention of claim 2 is the configuration described in claim 1, wherein the high-voltage receiving equipment comprises a first cubicle to which a service cable is connected and to which high voltage is supplied, and a second cubicle to which high voltage is supplied via a feed cable that passes through the first cubicle, and the first to third zero-phase current transformers are installed relative to the first cubicle, as well as a fourth zero-phase current transformer attached to the feed cable, a fifth zero-phase current transformer attached to the grounding wire of the shielding member of the feed cable, and a high voltage receiving equipment installed in the second cubicle. The system includes a sixth zero-sequence current transformer attached to the Class A grounding wire of the voltage equipment, and the zero-sequence current information detected by these zero-sequence current transformers is transmitted to a predictive detection unit. The predictive detection unit determines that there is an indication of insulation deterioration on the high-voltage side of the second cubicle when it detects a zero-sequence current of an abnormal value above a certain level in either the fifth zero-sequence current transformer or the sixth zero-sequence current transformer, and transmits a predictive detection signal to a notification unit that includes location information of the zero-sequence current transformer that showed the abnormal value. With this configuration, if a zero-sequence current exceeding a certain value is detected simultaneously at multiple locations on the second cubicle side, including the feed cable, that is, if ground fault discharge occurs at multiple locations on the second cubicle side, including the feed cable, it is determined that there is a sign of insulation deterioration on the second cubicle side. Therefore, by making a judgment based on ground fault discharge at multiple locations, it is possible to prevent false detection of signs of insulation deterioration, and it is possible to detect insulation deterioration of the high-voltage circuit on the second cubicle side at an early stage and take action before it leads to a ground fault. 【0008】 The invention of claim 3 is characterized in that, in the configuration described in claim 1 or 2, the predictive indicator unit has a storage unit that stores the association between a combination of zero-phase current transformers that is determined to have an indication of insulation deterioration and an area where insulation deterioration occurs, and when it is determined that there is an indication of insulation deterioration, it reads information of the area where insulation deterioration occurs corresponding to the combination of zero-phase current transformers that detected an abnormal value from the storage unit, attaches it to the predictive indicator signal and transmits it. With this configuration, the notification unit that receives the warning signal can notify the area where the insulation degradation occurred, along with the notification of the insulation degradation. Therefore, the cubicle manager can limit the inspection area, which is convenient. [Effects of the Invention] 【0009】 According to the present invention, if a zero-sequence current exceeding a certain value is detected simultaneously at multiple locations, including the service drop cable, that is, if ground fault discharge occurs simultaneously at multiple locations, including the service drop cable, it is determined that there is a sign of insulation deterioration. Therefore, by making a judgment based on ground fault discharge at multiple locations, it is possible to prevent false detection of signs of insulation deterioration and to detect insulation deterioration in high-voltage circuits at an early stage and take action before it leads to a ground fault. Furthermore, since information on the location of ground fault discharge detection is notified, it is possible to limit the affected area and easily pinpoint the location of the incident. [Brief explanation of the drawing] 【0010】 [Figure 1] This is a configuration diagram showing an example of an insulation monitoring device according to the present invention. [Figure 2] This is a diagram illustrating the operating principle of the signal converter. [Figure 3] This is an explanatory diagram of the input and output waveforms of a signal converter. [Figure 4] This is an explanatory diagram illustrating other examples of input and output waveforms of a signal converter. [Figure 5] This is a block diagram of the warning sign judgment unit. [Figure 6] This diagram illustrates the combination of zero-phase current transformers that indicate signs of insulation degradation. (a) shows the output waveform of the first signal converter based on the output of the first zero-phase current transformer, (b) shows the output waveform of the second signal converter based on the output of the second zero-phase current transformer, and (c) shows the output waveform of the third signal converter based on the output of the third zero-phase current transformer. [Figure 7] This is a diagram illustrating the configuration of an insulation monitoring device for a high-voltage power receiving facility consisting of two cubicles. [Modes for carrying out the invention] 【0011】 Hereinafter, embodiments embodying the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing an example of an insulation monitoring device according to the present invention. The insulation monitoring device 1 includes a plurality of zero-phase current transformers (hereinafter referred to as "ZCTs") 2, a signal converter 3 that digitally converts the analog signals output by the ZCTs 2, a prediction determination unit 4 that determines the occurrence of a sign of insulation degradation, and a notification unit 5 that notifies the external of the determination result. In FIG. 1, reference numeral 6 denotes an incoming cable for drawing in high-voltage power such as AC 6600V supplied from an electric power company, and reference numeral 7 denotes a cubicle as high-voltage power receiving equipment. Each ZCT 2 and the signal converter 3 form a pair, and the output of the signal converter 3 is transmitted to the prediction determination unit 4 via signal lines L1 to L3. 【0012】 In the cubicle 7, a transformer 71 that converts high voltage to low voltage is housed to supply the received high-voltage power to a load (not shown). The incoming cable 6 is connected to the transformer 71 that steps down the voltage via a main disconnecting device (circuit breaker) 72, a high-voltage capacitor facility 73, and the like. The power stepped down by the transformer 71 is supplied to a load not shown via a switchboard 8 or the like. 【0013】 Three ZCTs 2 and signal converters 3 (the first to third ZCTs 2a to 2c, the first to third signal converters 3a to 3c) are installed for this high-voltage power receiving equipment. Specifically, they are installed at three locations on the high-voltage side of the cubicle 7. The first ZCT 2a is attached to the incoming cable 6. The incoming cable 6 is composed of three cables through which three-phase alternating current is passed, and the first ZCT 2a is attached to this three-phase alternating current. The second ZCT 2b is attached to the type A ground wire 12a of a shielding member 11 made of a copper tape or the like wound around the incoming cable 6. The third ZCT 2c is attached to the common type A ground wire 12b of high-voltage devices such as the main disconnecting device 72 and the high-voltage capacitor facility 73 installed in the cubicle 7. 【0014】 The signal converter 3 is installed integrally or in the vicinity for each ZCT2, and includes a sample-and-hold circuit and a comparator circuit. It converts an analog signal of a steep beard-shaped zero-phase current waveform output when the ZCT2 receives a ground fault discharge into a digital signal, that is, performs A / D conversion and outputs it. FIG. 2 is a principle explanatory diagram of the signal converter 3, and FIG. 3 is a waveform explanatory diagram showing the relationship between the input and output of the signal converter 3. The operation of the signal converter 3 will be described with reference to FIGS. 2 and 3. In FIG. 2, 31 is an integration capacitor, 32 is a determination circuit, 33 is a charging contact for charging the integration capacitor 31, and 34 is a discharging contact for discharging the integration capacitor 31. Note that the integration capacitor 31 may be in another form that temporarily stores current. FIG. 3 is an explanatory diagram showing a case where the measurement period t is turned on / off in联动 with the voltage period of the measurement target. FIG. 3(a) is the output waveform of the ZCT2, FIG. 3(b) is the integration waveform (the stored voltage of the integration capacitor 31), and FIG. 3(c) is the output waveform of the determination circuit 32. 【0015】 The on / off measurement period t of the charging contact 33 and the discharging contact 34 can be arbitrarily changed. For example, it may be in联动 with the voltage period (positive / negative inversion) of the measurement target as shown in FIG. 3. In FIG. 3, the charging contact 33 is in the on state while the commercial power voltage is positive or negative, and only operates in the off state at the time of positive / negative inversion. The discharging contact 34 only operates in the on state at the time of positive / negative inversion. As a result, the integration waveform shown in FIG. 3(b) is generated. When a steep beard-shaped waveform Q due to a ground fault discharge as shown in FIG. 3(a) occurs, an integration waveform exceeding a preset constant value (threshold value T) is generated. 【0016】 The determination circuit 32 stores the threshold value T (shown in FIG. 3(b)). When the stored charge amount of the integration capacitor 31 exceeds the threshold value T, it outputs a "1" signal as shown in FIG. 3(c). That is, it outputs a ground fault discharge detection signal. And the generation of such a signal is implemented by a sample-and-hold circuit and a comparator circuit. The ground fault discharge detection signal is output, for example, within the width of the voltage half-cycle t of the commercial power. 【0017】 The whisker-like waveform Q is a ground fault waveform that occurs in a short time of less than 1 msec. When such a waveform is detected and its magnitude exceeds the threshold T, a ground fault discharge detection signal as shown in Figure 3(c) is output. Therefore, the measurement period can be sufficiently shorter than the commercial power period. Figure 4 is an explanatory diagram of another example of the input and output waveforms of the signal converter 3, showing the case where the measurement period t is approximately 1 / 20th of the measurement period t in Figure 3. The charging contact 33 turns off when the measurement period t is reached, and the discharge contact turns on when the measurement period is reached. As a result, similar to the measurement period in Figure 3, the integral waveform shown in Figure 4(b) is generated, and if a steep, whisker-like waveform Q occurs due to ground fault discharge as shown in Figure 4(a), an integral waveform exceeding a predetermined constant value (threshold T) is generated. The measurement period can be set to any value less than 50 msec. 【0018】 Figure 5 shows a block diagram of the Prediction Judgment Unit 4. As shown in Figure 5, the Prediction Judgment Unit 4 includes three signal input units 41 (41a to 41c) that receive the output signals of each signal converter 3, an input IF 42 that receives signals from the signal input units 41, an output IF 43 that outputs a prediction detection signal, a storage unit 44 that stores the relationship between the combination of ground fault discharge detection signals and the area where insulation deterioration occurs, and a Prediction Judgment Unit CPU 45 that determines whether there is an indication of insulation deterioration and controls the Prediction Judgment Unit 4. 【0019】 The memory unit 44 stores the relationship between the following combinations of ground fault discharge detection signals and the area where insulation degradation occurs. It stores the combination of the first ZCT2a and the second ZCT2b, and the combination of the first ZCT2a and the third ZCT2c as combinations that indicate the occurrence of insulation degradation. When the combination of the first ZCT2a and the second ZCT2b is detected, the incoming cable 6 is stored as the area where insulation degradation occurs, and when the combination of the first ZCT2a and the third ZCT2c is detected, the inside of the cubicle 7 is stored as the area where insulation degradation occurs. 【0020】 Figure 6 is an explanatory diagram of combinations of ZCT2 that the predictive detection unit 4 determines to have an indication of insulation deterioration, where (a) shows the output waveform of the first signal converter 3a based on the output of the first ZCT2a, (b) shows the output waveform of the second signal converter 3b based on the output of the second ZCT2b, and (c) shows the output waveform of the third signal converter 3c based on the output of the third ZCT2c. As shown in Figure 6, even if any of the ZCT2 independently detects a zero-sequence current waveform corresponding to a ground fault discharge and the signal converter 3 outputs a ground fault discharge detection signal, the predictive indicator unit 4 does not determine that there is an indication of insulation deterioration. 【0021】 However, if the first ZCT2a and the second ZCT2b simultaneously (indicated by M1), or the first ZCT2a and the third ZCT2c simultaneously (indicated by M2), detect a zero-sequence current exceeding a predetermined value (threshold T), the memory unit 44 determines from the stored information that there is an indication of insulation degradation and outputs a warning signal from output IF43. 【0022】 At that time, the predictive detection signal output by the predictive detection unit 4 includes information on the combination of ZCT2s from which the abnormality occurred, and information on the insulation degradation occurrence area stored in the memory unit 44, and is transmitted with these attached. For example, if the first ZCT2a and the second ZCT2b simultaneously detect a ground fault discharge, information about the associated insulation degradation area, i.e., information indicating that insulation degradation has occurred somewhere in the incoming cable 6, is transmitted to the notification unit 5, and the notification unit 5 then notifies (displays) this information. 【0023】 The notification unit 5 has a display unit, an audible alarm unit, etc. (not shown), and is connected to the predictive detection unit 4 by a signal line L10. When it receives a predictive detection signal from the predictive detection unit 4, the display unit shows the location information of the ZCT2 where the abnormality occurred and the information of the area where the insulation deterioration occurred. Depending on the settings, it also emits an alarm sound to notify of the occurrence of an abnormality. 【0024】 Furthermore, while the prediction unit 4 and the notification unit 5 communicate via signal line L10, wireless communication is also possible, or the notification unit 5 could be a mobile phone carried by the administrator, and notifications could be sent via the internet. Additionally, if all three ZCTs 2 detect a zero-sequence current equivalent to a ground fault discharge, it can be assumed that insulation degradation has occurred in both the incoming cable 6 and the cubicle 7, and it would be beneficial to display such information. 【0025】 In this manner, if a zero-sequence current exceeding a certain value is detected simultaneously at multiple locations, including the service drop cable 6, that is, if ground fault discharge occurs at multiple locations including the service drop cable 6, it is determined that there is an indication of insulation deterioration, and a warning signal is output. Therefore, by making a judgment based on ground fault discharge at multiple locations, it is possible to prevent false detection of signs of insulation deterioration, and to detect insulation deterioration in high-voltage circuits at an early stage and take action before it leads to a ground fault. Furthermore, since the information on the zero-sequence current, which indicates an abnormal value above a certain threshold, is digitized and transmitted to the predictive detection unit 4, the likelihood of the predictive detection unit 4 malfunctioning due to noise can be reduced. Furthermore, in addition to the location of ground fault discharge detection, information on the area where insulation degradation has occurred associated with the detection location is also provided, allowing the cubicle manager to limit the inspection area, which is convenient. Furthermore, the information attached to the warning signal does not necessarily need to include information about the area where insulation degradation occurred; the area can be estimated using only the information about the location of the ground fault discharge detection. 【0026】 Figure 7 shows another example of the insulation monitoring device 1. While Figure 1 above shows a configuration applied to a high-voltage power receiving facility consisting of one cubicle 7, Figure 7 shows a configuration applied to a high-voltage power receiving facility consisting of two cubicles (first cubicle 7a, second cubicle 7b). Note that both cubicles 7a and 7b have the same configuration as the cubicle shown in Figure 1 above, so their explanation is omitted. As shown in Figure 7, commercial power is supplied to the first cubicle 7a via a high-voltage inlet cable 6a, and to the second cubicle 7b, the high-voltage side of the first cubicle 7a is branched off by a high-voltage branching section 74 and supplied via a high-voltage feed cable 6b. Furthermore, the power stepped down in the first cubicle 7a is supplied to loads (not shown) via the distribution panel 8a, and the power stepped down in the second cubicle 7b is supplied to loads (not shown) via the distribution panel 8b. 【0027】 When the high-voltage receiving equipment consists of two cubicles 7a and 7b as described above, ZCT2 is installed for both cubicles 7a and 7b. For the first cubicle 7a, the 1st to 3rd ZCT2a to 2c are installed in the same locations as shown in Figure 1 above. For the second cubicle 7b, the 4th to 6th ZCT2d to 2f are installed in three locations on the high-voltage side of the second cubicle 7b. Specifically, the fourth ZCT2d is attached to the upstream side of the feed cable 6b that supplies high-voltage power to the second cubicle 7b. The fifth ZCT2e is attached to the Class A grounding wire 12c of the shielding member 11 of the feed cable 6b. The sixth ZCT2f is attached to the Class A grounding wire 12d of the main circuit breaker 72 of the second cubicle 7b. Furthermore, as shown in Figure 7, the 4th ZCT2d and 5th ZCT2e are installed in the first cubicle, which is upstream of the feed cable 6b. 【0028】 Each of these is provided with a signal converter (1st to 6th signal converters 3a to 3f), which converts the analog signal into a digital signal and transmits it to the predictive detection unit 4 via signal lines L1 to L6. 【0029】 On the other hand, the pre-determination unit 4 is equipped with six signal input units 41 corresponding to the number of ZCT2, and the storage unit 44 stores information on combinations for determining pre-determination of insulation degradation in the first to sixth ZCT2a to 2f, and the association of those combinations with the corresponding insulation degradation occurrence areas. Specifically, the stored information for insulation degradation areas based on the combination of the 1st to 3rd ZCT2a to 2c is the same as described above, but the stored information for insulation degradation areas with the addition of the 4th to 6th ZCT2d to 2f is set and stored as follows. If the first ZCT2a, fourth ZCT2d, and fifth ZCT2e simultaneously detect a ground fault discharge, the insulation degradation area will be the supply cable 6a. If the first ZCT2a, fourth ZCT2d, and sixth ZCT2f simultaneously detect a ground fault discharge, the insulation degradation area will be the high-voltage side of the second cubicle 7b. 【0030】 Based on the combination information of ZCT2 stored in the memory unit 44, the prediction unit 4 determines that there is an indication of insulation degradation. Once it determines that there is an indication of insulation degradation, the location information of the ZCT2 that made the determination, and the information of the associated insulation degradation occurrence area are notified to the notification unit 5. Furthermore, if ground fault discharge is detected simultaneously in other combinations, it can be considered that insulation degradation or malfunction has occurred in multiple locations, so it would be good to display such information. 【0031】 Thus, even in a configuration where a second cubicle 7b is supplied with high-voltage power from the first cubicle 7a via a feed cable 6b, if a zero-sequence current exceeding a certain value is detected simultaneously at multiple locations on the second cubicle 7b side, including the feed cable 6b, that is, if ground fault discharge occurs at multiple locations on the second cubicle 7b side, including the feed cable 6b, it is determined that there are signs of insulation deterioration on the second cubicle 7b side. Therefore, by making a judgment based on ground fault discharge at multiple locations, it is possible to prevent false detection of signs of insulation deterioration, and to detect insulation deterioration of the high-voltage circuit on the second cubicle 7b side at an early stage and take action before it leads to a ground fault. 【0032】 In the above embodiment, two cases were described: one in which the high-voltage power receiving equipment consists of one cubicle 7, and another in which it consists of two cubicles, a main (first cubicle 7a) and a sub (second cubicle 7b). However, the insulation monitoring device of the present invention is not limited to these two cases. This method can be easily applied to high-voltage receiving equipment where, in addition to the main cubicle to which the high-voltage inflow cable 6 is connected, multiple sub-cubicles are connected from the main cubicle by feed cables 6b. As described above, by installing ZCT2 at three locations on the high-voltage side corresponding to each cubicle and detecting ground fault discharge, it is possible to identify the area where the initial stage of insulation degradation occurred based on the combination of locations detected simultaneously. [Explanation of symbols] 【0033】 1. Insulation monitoring device, 2 (2a~2f)...ZCT (Zero-phase current transformer), 3 (3a~3f)...Signal converter, 4...Predictive detection unit, 5...Notification unit, 6,6a...Incoming cable, 6b...Outgoing cable, 7...Cubicle, 7a...First cubicle, 7b...Second cubicle, 11...Shielding member, 12 (12a,12b)...Type A grounding wire, 32...Determination circuit, 41...Signal input unit, 44...Memory unit, 45...Predictive detection unit CPU, 71...Transformer, 72...Main circuit breaker (disconnector), T...Threshold.

Claims

[Claim 1] The first zero-phase current transformer attached to the service entrance cable to the high-voltage power receiving equipment, A second zero-phase current transformer is attached to the grounding wire of the shielding member of the aforementioned incoming cable, A third zero-phase current transformer attached to the Class A grounding wire of the high-voltage equipment of the aforementioned high-voltage power receiving equipment, A signal converter that converts the zero-sequence current output by the zero-sequence current transformer into a digital signal, A warning unit for determining signs of insulation degradation, It has a notification unit that notifies the judgment result of the aforementioned predictive indicator unit, The signal converter is arranged integrally with or near each of the zero-sequence current transformers, and the detected zero-sequence current is digitally converted and transmitted to the prediction unit. The aforementioned indicator detection unit determines that there is an indication of insulation deterioration if it detects a zero-sequence current exceeding a certain value simultaneously in either the second zero-sequence current transformer or the third zero-sequence current transformer and the first zero-sequence current transformer. An insulation monitoring device characterized by transmitting a predictive detection signal to the notification unit, which includes location information of the zero-phase current transformer that showed the aforementioned abnormal value. [Claim 2] The high-voltage receiving equipment comprises a first cubicle to which the incoming cable is connected and to which high voltage is supplied, and a second cubicle to which high voltage is supplied via a feed cable that passes through the first cubicle. The first to third zero-phase current transformers are installed in relation to the first cubicle, and the fourth zero-phase current transformer is attached to the feed cable, A fifth zero-phase current transformer attached to the grounding wire of the shielding member of the aforementioned feed cable, The system includes a sixth zero-phase current transformer attached to the Class A grounding wire of the high-voltage equipment installed in the second cubicle, The zero-sequence current information detected by these zero-sequence current transformers is transmitted to the prediction unit. If the aforementioned indicator detection unit detects a zero-sequence current exceeding a certain value simultaneously in either the fifth zero-sequence current transformer or the sixth zero-sequence current transformer, and in the first zero-sequence current transformer and the fourth zero-sequence current transformer, it determines that there is an indication of insulation deterioration on the high-voltage side of the second cubicle. The insulation monitoring device according to claim 1, characterized in that it transmits a predictive detection signal to the notification unit, which includes location information of the zero-phase current transformer that showed the abnormal value. [Claim 3] The aforementioned indicator determination unit has a storage unit that stores the association between the combination of zero-phase current transformers that is determined to be an indicator of insulation deterioration and the area where insulation deterioration occurs. The insulation monitoring device according to claim 1 or 2, characterized in that, when it is determined that there is a sign of insulation deterioration, it reads from the storage unit information of the insulation deterioration occurrence area corresponding to the combination of zero-phase current transformers that detected the abnormal value, attaches it to the sign detection signal, and transmits it.

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