JP2008309681A - Insulation deterioration monitoring device and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulation deterioration monitoring device for detecting the error of determination of insulation deterioration by obtaining the effective component of leakage current of the maximum phase of the insulation deterioration in a star circuit of a neutral earthing system or a non-earthing three-phase circuit, and to provide its method. <P>SOLUTION: The insulation deterioration determination monitoring device 5 includes: a zero phase current transformer 4 for detecting the leakage current of a non-measuring electric path by monitoring the insulation deterioration in the three-phase electric path 3 of non-earthing or star connection of the neutral point earthing; a rectangular wave output means 9 for outputting a start signal of an operation cycle by detecting one inter-line voltage signal of the non-measuring electric path and a zero cross point of an inter-line voltage phase signal; a storing part 13 for storing to tabulate the voltage waveform of two sets of effective values 1; and a calculating part 11 for calculating the leakage current from a current signal of the zero phase current transformer 4 and the voltage waveform stored to the storing part 13. The monitoring device calculates and compares two phase components of the leakage current from first voltage waveform and second voltage waveform tabulated based on the start signal and the output current of the zero phase current transformer 4, and calculates the leakage current value of the maximum phase of an insulation deterioration phase based on the phase component of the large value. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an insulation deterioration monitoring apparatus and method, and more particularly to a technique for monitoring insulation deterioration by calculating a leakage current of an electric circuit of a distribution system including a load facility.

In the distribution system, the insulation state is regularly measured to prevent leakage fires and electric shock accidents, but in the past, the power distribution line (cables, wires) and the mega ring of the load equipment (insulation resistance measurement) after power failure ). In recent years, a method of constantly measuring a leakage current with a live wire has been adopted.
JP 2005-172617 A Japanese Patent Laid-Open No. 06-339218 JP-A 61-54463

  In the above-mentioned patent document 1, when the power distribution method is a three-phase circuit, there is a problem that the effective component calculation of the leakage current is limited to the delta circuit and cannot be applied to the star circuit. In Patent Document 2, a zero-phase current transformer (hereinafter referred to as ZCT) and a grounded instrument transformer (hereinafter referred to as GPT) provided in an ungrounded circuit are used. There is a problem that an accurate numerical value cannot be obtained because whether or not the phase of the output current of the ZCT is within a predetermined range is used. In Patent Document 3 above, the leakage current is measured as the sum of the three phases because of the voltage signal superposition method, and the electric circuit is judged as three-wire simultaneous deterioration and averaged insulation deterioration state. Since it is detected that the deteriorated phase is not deteriorated and the minimum insulation deteriorated phase is detected to be deteriorated, there is a problem that early detection cannot be performed and a misjudgment is caused. For example, when the leakage current of the R phase is 20 mA, the leakage current of the S phase is 0.1 mA, and the leakage current of the T phase is 2 mA, the voltage superposition method averages 7.36 mA, which is a degradation of 20 mA. The phase is 1/3 of the result (-63.2%) and appears as a large error. Moreover, even if it is 0.1 mA, the value is 73.6 times as large, and the result of the determination of insulation deterioration cannot be made at all.

  In addition, when the ground phase voltage is used as a reference as shown in FIG. 7, there is a method of taking the ground line signal 23 at the neutral point of the transformer 20 in the 4-wire distribution line and calculating the in-phase component with this reference voltage. There is a problem that the number of wiring is large. Further, as shown in FIG. 8, there is a problem that the neutral grounding line signal may not be taken in at a position away from the transformer 20 in the three-wire distribution path, and measurement cannot be performed.

  An object of the present invention is to solve these problems and to provide an insulation deterioration monitoring apparatus and method for calculating an effective component of leakage current in a three-phase star circuit or the like.

  The present invention relates to an insulation deterioration monitoring device for monitoring insulation deterioration in a star connection of neutral point grounding or an ungrounded three-phase circuit, and includes one line voltage signal of the non-measurement circuit and the line voltage phase signal. The rectangular wave output means for detecting the zero cross point of the output and outputting the start signal of the calculation cycle, the storage unit for storing the two voltage waveforms of the effective value 1 in a table, and the zero for detecting the leakage current of the non-measurement circuit An arithmetic unit that calculates a leakage current from the current signal from the phase current transformer and the voltage waveform stored in the storage unit, and the first voltage waveform and the second voltage waveform that are tabulated based on the start signal And two phase components of the leakage current are calculated from the output current of the zero-phase current transformer and compared, and the deterioration degradation monitor calculates the leakage current value of the maximum phase of the insulation degradation phase based on the larger phase component Device.

  Further, the present invention is an insulation deterioration monitoring device for monitoring insulation deterioration in a star connection of neutral point grounding or a non-grounded three-phase circuit, wherein one line voltage signal of the non-measurement circuit and the line voltage A rectangular wave output means for detecting the zero-cross point of the phase signal and outputting a start signal of the calculation cycle, two sets of effective value 1 voltage waveforms, and two sets of effective values 1 that are 180 degrees out of phase with respect to the two sets A storage unit that stores voltage waveforms in a table, and a calculation unit that calculates a leakage current from a current signal from a zero-phase current transformer that detects a leakage current of a non-measurement circuit and a voltage waveform stored in the storage unit Leakage current from the first voltage waveform, the second voltage waveform, the third voltage waveform, the fourth voltage waveform and the output current of the zero phase current transformer tabulated based on the start signal. Calculate the four phase components and compare them to find the largest phase Min is insulation deterioration monitoring device for calculating the leakage current of the maximum phase insulation deterioration phase based on.

  The present invention also provides a current signal obtained by detecting a leakage current of a non-measurement circuit with a zero-phase current transformer in a star connection of neutral point grounding or a non-grounded three-phase circuit, and one line voltage of the non-measurement circuit. A signal and a zero crossing point of the line voltage signal as a start signal of an operation cycle, and two sets of voltage waveforms of effective value 1 are tabulated and stored in a storage unit; a current signal of the zero-phase current transformer; A step of calculating a leakage current from the voltage waveform stored in the storage unit, a first voltage waveform and a second voltage waveform tabulated based on the start signal, and an output current of the zero-phase current transformer And calculating the leakage current value of the maximum phase of the insulation deterioration phase based on the phase component having a larger value by comparing the two phase components of the leakage current.

  Furthermore, the present invention relates to a current signal obtained by detecting a leakage current of a non-measurement circuit with a zero-phase current transformer in a star connection of neutral point grounding or a non-grounded three-phase circuit, and one line voltage of the non-measurement circuit. The signal and the zero crossing point of the line voltage signal are used as the start signal of the calculation cycle, and two sets of effective value 1 voltage waveforms and two sets of effective value 1 voltage waveforms that are 180 degrees out of phase with respect to the two sets. A step of storing in a table; a step of calculating a leakage current from the current signal of the zero-phase current transformer and the voltage waveform stored in the storage; and a first voltage tabulated based on the start signal Four phase components of the leakage current are calculated from the waveform, the second voltage waveform, the third voltage waveform, the fourth voltage waveform, and the output current of the zero-phase current transformer, and compared to obtain the largest value. Calculate the leakage current value of the maximum phase of the insulation deterioration phase based on the phase component An insulating deterioration monitoring method and a step.

  According to the present invention, the effective component of the leakage current of the maximum phase of the insulation deterioration phase can be calculated by the input of one voltage signal and ZCT even in a star connection of neutral point grounding or a non-grounded three-phase circuit. To provide an insulation deterioration monitoring apparatus and method capable of eliminating erroneous determination in the superposition method, reducing the number of connection lines, reducing the man-hours for wiring, and reducing the attention at the time of installation because the installation direction of ZCT is not limited. Can do.

The best mode for carrying out the present invention will be described.
Embodiments of the insulation deterioration monitoring apparatus and method according to the present invention will be described below with reference to FIGS.

  Example 1 will be described. The insulation deterioration monitoring apparatus of the present embodiment will be described with reference to FIG. FIG. 3 shows a configuration of a non-measurement electric circuit for monitoring insulation deterioration and an insulation deterioration monitoring device. 1 is a three-phase star-connected transformer in which a neutral point 2 on the secondary side is installed. The electric circuit is an R-phase, S-phase, or T-phase electric circuit. 4a is a ZCT, which is installed in an electric circuit to be measured, and a plurality of units may be installed as in 4n as required. 5 is an insulation deterioration monitoring device of this embodiment, 6 and 7 are voltage signal lines for taking in a voltage phase from between the R-phase and S-phase lines of the electric circuit 3, and 8 is a step-down voltage level of the voltage signal lines 6 and 7. In addition, step-down insulation means for performing insulation, 9 is a rectangular wave generating means for detecting the zero cross point of the voltage signal and outputting a calculation start signal, and 10a is detected by the ZCT of ZCT 4a,. Amplifying / A / D converting means for amplifying the leakage current and converting an analog signal into a digital signal, corresponding to ZCT4a,..., 4n. 11 receives the calculation start signal from the rectangular wave generating means 9 and detects the leakage current from the digital signal from the amplification / A / D converting means 10a,..., 10n and the voltage waveform of effective value 1 described later. Arithmetic control means mainly for calculating effective components, 12 is a selection means for sequentially selecting and transmitting voltage waveform data of effective value 1 stored in the storage means 13 to the arithmetic control means, and 13 is a storage means. Voltage waveform data of value 1 is stored, voltage waveform data 13b of effective value 1 delayed by 30 degrees from the line voltage, voltage waveform data 13c of effective value 1 delayed by 150 degrees from the line voltage, and line voltage The voltage waveform data 13a having an effective value of 1 with the same phase, that is, a voltage of 0 degree is stored in a table. The voltage waveform data 13a having an effective value of 1 at a voltage of 0 degrees is for application to a single-phase electric circuit and is for expanding the range of use. 14 is a display means for displaying the leakage current value Io and the calculation result of the effective component of the leakage current, 15 is a communication means for transmitting the calculation result to the host device, and 16 is the insulation deterioration monitoring device 5. It is a power supply part for supplying an appropriate voltage to each part.

  The operation of the insulation deterioration monitoring device 5 configured as described above is performed by detecting the zero cross point of the line voltage signal taken in from the electric circuit 3 and amplifying the signal from the ZCT 4a by the calculation start signal output from the rectangular wave generating means 9. The calculation (1) described later is performed using the leakage current waveform Io captured through the A / D conversion means and the voltage waveform data 13b having an effective value 1 delayed by 30 degrees and stored in the storage unit 13.

Next, a later-described calculation (2) is performed using the voltage waveform 13c having an effective value 1 delayed by 150 degrees and the leakage current Io stored in the storage unit 13c. Next, the value (1) and the value (2) are compared, and the calculation (3) described later is performed for the larger result. In this way, the effective component of the leakage current of the maximum phase of insulation deterioration is calculated.
Here, if the accuracy of the effective component of the calculated leakage current is calculated using the values described in the voltage superposition method, the R phase is 20 mA, the S phase is 0.1 mA, and the T phase is 2 mA. The combined leakage current Io is 19.01 mA, and the leakage current of the maximum phase of insulation deterioration calculated from this value by the above method is 19.9 mA. Since it is 19.9 mA for the R phase, ie 20 mA, a result of -0.05% is obtained. That is, it is possible to obtain a result with much higher accuracy than the voltage superposition method.

  By the way, in the insulation deterioration monitoring apparatus of the present embodiment, the voltage signal lines 6 and 7 for taking in the voltage phase are taken in from the R phase and the S phase of the electric circuit 3, but may be taken in from the T phase and the R phase. Moreover, you may take in from S phase and T phase. That is, the calculation may be performed from any phase, and the relationship with the next voltage phase may be maintained at 120 degrees. Further, if it is the next voltage phase that is one distance away, it may be maintained at 240 degrees, but the voltage waveform data of effective value 1 stored in the storage unit 13 may be arranged in a similar relationship. However, there is a possibility that it will be confused if the expression is good everywhere, and it is also possible to decide uniquely because the R-phase and T-phase on the actual wiring are both ends of the electric circuit.

  In the above description, the neutral point grounded star circuit is described, and the star circuit and the delta circuit of the non-grounded circuit are omitted. However, it is obvious that the voltage phases have the same relationship and can be performed in the same manner. That is, in the non-grounded circuit, GPT or a ground compensation capacitor is used to measure the leakage current, and these neutral points are grounded to be the same as a neutral point grounded star circuit.

  Next, the insulation deterioration monitoring method in Embodiment 1 will be described with reference to FIGS. FIG. 1 is a vector diagram of an insulation deterioration monitoring method showing the present embodiment. Fig. 5 shows the phase relationship between a three-phase three-wire or four-wire grounded neutral point and a three-phase three-wire star circuit and a delta circuit in a non-grounded circuit. Each phase voltage has a phase difference of 120 degrees. Yes, each phase voltage that becomes the ground reference voltage is delayed by 30 degrees from each line voltage. FIG. 6 is an example in which this relationship is expressed in time series based on the line voltage VS-VR. That is, the R phase voltage VR is delayed by 30 degrees, the S phase is delayed by 150 degrees, and the T phase is delayed by 270 degrees. The neutral point (N point) grounding method is grounded to the ground as shown by the dotted line. Further, it is well known that the non-grounded circuit is grounded by GPT or a ground compensation capacitor instead of neutral point grounding.

  In FIG. 1A, the voltage VR 'indicates that it is delayed by 30 degrees from the line voltage, and the voltage VS' and the voltage VT 'are the same. In addition, insulation deterioration occurs in the R-phase line, slight insulation deterioration occurs in the T-phase line, and the S-phase line indicates an example of a healthy phase. In general, a neutral point grounded star circuit is known to have a very small capacitance (capacitor) component of the electric circuit, and a star circuit and a delta circuit in a non-grounded circuit are also known to be extremely small. Therefore, the combined leakage current of the R-phase leakage current Ior and the T-phase leakage current Iot is detected by ZCT and appears between the R phase and the T phase as Io. Let the phase for the R phase at this time be φ.

  Here, in order to develop the combined leakage current Io detected by ZCT into the original R-phase leakage current Ior, Io * cosφr and Io * sinφr multiplied by tan 30 degrees may be added. Alternatively, the square root of the value obtained by subtracting the square of Io * cos φr from the square of the leakage current Io, and the result obtained by multiplying the square root by 30 degrees may be added. To develop the leakage current Iot of the T phase, divide Io * sinφr by tan 30 degrees or subtract the square of Io * cosφr from the square of leakage current Io and divide it by tan30 degrees. That's fine.

  What is required here is the maximum phase that has undergone insulation degradation. The above example is based on the premise that the R phase is the maximum phase of insulation degradation and the T phase is the next largest degradation phase. However, it is unknown at which position Io detected by ZCT appears.

In this embodiment, the problem is solved as follows.
First, Io * cosφr which is the in-phase component with the R-phase voltage VR ′ of the leakage current Io, that is, the value (1) in FIG. 1A, is calculated, and then the in-phase component with the S-phase voltage VS ′, FIG. b) Calculate Io * cosφs which is the value (2) of the two, compare the two of these results, and add the value obtained by multiplying Io * cosφ and Io * sinφ by tan 30 degrees using the larger value. Alternatively, the square root is obtained by subtracting the square of Io * cosφ from the square of the leakage current Io, and the result obtained by multiplying the square root by 30 degrees is added.
Here, Io * cosφ and Io * sinφ are representatively represented by the phase angle of the leakage current Io in each phase, but if expressed only by the effective component of Io * cosφ, that is, the leakage current Io, the leakage current Io The square can be unified by subtracting the square of Io * cosφ from the square.

According to the above method, it is not necessary to start from the R-phase voltage VR ′, and may start from the S-phase voltage VS ′, or may start from the T-phase voltage VT ′. That is, it is only necessary to calculate for two phases, and it is only necessary to calculate for any two phases while maintaining the relationship of 30 degree delay, 150 degree delay, and 270 degree delay with reference to the line voltage.
In FIG. 1B, the value (2) of the in-phase component of the S-phase voltage VS ′ is 180 degrees opposite, but if it is calculated by a trigonometric function, it has a size with a sign. No problem.

Expressing the above in the formula,
Iox = Io * cos φ + √ (Io ² − (Io * cos φ) ² ) (1)
It becomes.

  Next, since the calculation for Io * cosφ, that is, the effective component of the leakage current Io is the same-phase component as the phase voltage, power calculation is performed with the line voltage waveform of effective value 1 delayed by 30 degrees or 150 degrees tabulated. However, the contents are based on the above-mentioned Patent Document 1 filed by the inventor and will not be described.

  A second embodiment will be described. The insulation deterioration monitoring apparatus of the present embodiment will be described with reference to FIG. The same parts as those of the apparatus of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the apparatus of the second embodiment, the effective value 1 waveform data 13d delayed 210 degrees from the line voltage and the effective value 1 waveform data 13e delayed 330 degrees from the line voltage are stored in the storage unit 13 as a table. Yes.

  The operation of the insulation deterioration monitoring device 5 configured as described above is performed after the calculation of the effective component of the leakage current Io and the waveform data 13b and 13c of the effective value 1 having the voltage delay of 30 degrees and the voltage of 150 degrees. Further, the effective component of the waveform data 13d and 13e having effective values 1 with a voltage of 210 degrees and a delay of 330 degrees and the leakage current Io is calculated, and the largest of the four is used as the calculation result.

  As described above, even if there is a ZCT installation direction error or a ZCT secondary output line wiring error, the effective component of the leakage current of the maximum phase of insulation deterioration is correctly calculated. Therefore, installation and construction of ZCT are easy to perform, and a power failure for re-execution of the ZCT secondary wiring becomes unnecessary, which is extremely effective.

  The insulation deterioration monitoring method according to the second embodiment will be described with reference to FIG. As shown in FIG. 7, the installation direction of the ZCT for detecting the leakage current is K on the power source side and L on the load side, and k and l correspond to the secondary side output. However, if the installation direction is wrong or the connection on the secondary side is wrong, the position of the combined leakage current Io appears different by 180 degrees. In addition, if the line voltage is taken as R—S, for example, S—R, similarly, the result is 180 degrees different, and the maximum leakage current with the correct insulation deterioration cannot be obtained.

  The second embodiment has been solved in view of such problems, and correctly calculates the leakage current of the maximum phase of the insulation deterioration phase even if the installation and wiring are wrong.

  In FIG. 2, Io is a combined leakage current that appears at the same position as in the first embodiment, Io ′ is a combined leakage current that appears when the installation direction of ZCT is wrong, and this Io ′ has an R-phase voltage VR. The value (1) of the in-phase component (active component) and 'is calculated, and then the value (2) of the in-phase component (active component) and the voltage VS' of the S phase are calculated. Then, the magnitudes of the value (1) and the value (2) are compared. Since the value (1) is negative and the value (2) is large, the leakage current Io ′ is calculated using the first value. The same calculation as in the example is performed. However, since the leakage current Io 'when the installation direction is wrong is different by 180 degrees, the developed size Ios' is smaller than the size of Ior.

Therefore, instead of shifting the phase of the leakage current Io by 180 degrees, the voltage phases VR ′ and VS ′ are respectively shifted by 180 degrees and the line voltages are 210 degrees and 330 degrees (30 degrees and 150 degrees plus 180 degrees). The calculation is performed.
That is, after the calculation according to the first embodiment, the results of the values calculated at the line voltages of 210 degrees and 330 degrees are compared, and the largest value is set as the value of the maximum phase of insulation deterioration.

  According to this method, since the leakage current of the maximum phase of insulation deterioration is correctly calculated even if the ZCT installation direction and the connection of the secondary output line are wrong, attention during installation can be reduced.

  As described above, the insulation deterioration monitoring device according to the embodiment is suitable for measuring leakage currents of distribution lines (electric circuits) of the distribution system including load facilities, that is, monitoring insulation deterioration states. The effective component of the leakage current of the maximum phase of insulation deterioration of the distribution line (electric circuit) is calculated, so the insulation deterioration state can be judged appropriately, and the effect when used is great. is there.

FIG. 3 is a vector diagram for explaining the operation of the insulation deterioration monitoring apparatus according to the first embodiment. The vector diagram explaining the operation | movement of the insulation deterioration monitoring apparatus of Example 2. FIG. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory diagram of an insulation deterioration monitoring device according to a first embodiment. FIG. 6 is a configuration explanatory diagram of an insulation deterioration monitoring device according to a second embodiment. The vector diagram of the neutral point grounded three-phase star circuit for demonstrating an Example. The voltage waveform figure for demonstrating an Example. The figure explaining the taking-in of the voltage to the insulation monitoring apparatus of the prior art example 1. FIG. The figure explaining the taking-in of the voltage to the insulation monitoring apparatus of the prior art example 2. FIG.

Explanation of symbols

  3 Electrical path, 4a,..., 4n ZCT, 5 Insulation deterioration monitoring device, 6, 7 Voltage lead-in line, 9 Rectangular wave generating means, 10a,..., 10n Amplification / A / D conversion means, 11 Calculation control means 12 selection means 13 storage means 13a voltage 0 degree effective value 1 waveform data 13b voltage 30 degree delayed effective value 1 waveform data 13c voltage 150 degree delayed effective value 1 waveform data 13d voltage 210 degree delayed effective value 1 waveform Data, 13e Voltage 330 degree delayed RMS value 1 waveform data.

Claims (4)

An insulation deterioration monitoring device that monitors insulation deterioration in a neutral connection star connection or ungrounded three-phase circuit,
Table of one line voltage signal in the non-measurement circuit, rectangular wave output means for detecting the zero cross point of the line voltage phase signal and outputting the start signal of the calculation cycle, and two sets of voltage waveforms having an effective value of 1 A storage unit configured to store, a calculation unit that calculates a leakage current from a current signal from a zero-phase current transformer that detects a leakage current of a non-measurement circuit, and a voltage waveform stored in the storage unit, and the start signal The two phase components of the leakage current are calculated from the first voltage waveform and the second voltage waveform tabulated based on the output current and the output current of the zero-phase current transformer, and the phase component having a larger value is compared. An insulation deterioration monitoring device that calculates a leakage current value of a maximum phase of an insulation deterioration phase based on the above. An insulation deterioration monitoring device that monitors insulation deterioration in a neutral connection star connection or ungrounded three-phase circuit,
One line voltage signal of the non-measurement circuit, a rectangular wave output means for detecting a zero-crossing point of the line voltage phase signal and outputting a start signal of an operation cycle, two sets of effective value 1 voltage waveforms, Two sets of voltage waveforms having an effective value of 1 that are 180 degrees out of phase with respect to two sets are stored in a table, a current signal from a zero-phase current transformer that detects a leakage current of a non-measurement circuit, and the above storage A calculation unit that calculates a leakage current from the voltage waveform stored in the unit, and a first voltage waveform, a second voltage waveform, a third voltage waveform, and a fourth voltage that are tabulated based on the start signal. The four phase components of the leakage current are calculated from the waveform and the output current of the zero-phase current transformer, and the leakage current value of the maximum phase of the insulation degradation phase is calculated based on the phase component having the largest value by comparison. An insulation deterioration monitoring device characterized by that.   Neutral grounded star connection or ungrounded three-phase circuit, current signal detected by zero-phase current transformer in leakage current of non-measurement circuit, one line voltage signal of non-measurement circuit, Using the zero-cross point of the voltage signal as a start signal of the calculation cycle, two sets of effective value 1 voltage waveforms are tabulated and stored in the storage unit, the current signal of the zero-phase current transformer and the storage unit The leakage current is calculated from the step of calculating the leakage current from the measured voltage waveform, the first voltage waveform and the second voltage waveform tabulated based on the start signal, and the output current of the zero-phase current transformer. And calculating a leakage current value of a maximum phase of the insulation deterioration phase based on a phase component having a large value by comparing two phase components. An insulation deterioration monitoring method comprising:   Neutral grounded star connection or ungrounded three-phase circuit, current signal detected by zero-phase current transformer in leakage current of non-measurement circuit, one line voltage signal of non-measurement circuit, A step of storing a table of two sets of effective value 1 voltage waveforms and two sets of effective value 1 voltage waveforms, which are 180 degrees out of phase with respect to the two sets, using the zero cross point of the voltage signal as a start signal of a calculation cycle. Calculating a leakage current from the current signal of the zero-phase current transformer and the voltage waveform stored in the storage unit; and a first voltage waveform and a second voltage tabulated based on the start signal Calculate the four phase components of the leakage current from the waveform, the third and fourth voltage waveforms and the output current of the zero-phase current transformer, and compare and insulate based on the phase component of the largest value And calculating a leakage current value of the maximum phase of the deteriorated phase. Insulation deterioration monitoring method characterized by.

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