Insulation monitoring device, insulation monitoring method

Abstract

To enable calculating a leakage current.SOLUTION: An insulation monitor device is an insulation monitor device that monitors a leakage current about a switching device controlling electricity to be supplied to a load from a power source, and the insulation monitor device comprises: a leakage current acquisition unit that is provided at least one of between a switching device and a load and between the switching device and a primary side, and acquires a leakage current value a leakage current detection unit detects; a primary side voltage acquisition unit that acquires a power source voltage value serving as a voltage value of the power source; and a period identification unit that identifies an on-period serving as a period of the electricity being supplied to the load from the switching device. Further, the insulation monitor device comprises an estimation unit that, with a period of the electricity being not supplied to the load by the switching device as an off-period, and with the power source voltage value as a reference based, estimates a normalized leakage current value serving as an effective value of the leakage current value when the on-period is 100% on the basis of the leakage current value in the on-period.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an insulation monitoring device and an insulation monitoring method.

Background Art

[0002] In order to operate industrial equipment safely, it is necessary to ensure a defined insulation performance. Since the insulation performance may deteriorate due to aging of materials or the like, it is desirable to periodically evaluate the insulation performance. Patent Document 1 discloses a circuit breaker characterized by including a switch unit that intermittently interrupts the load current of the main circuit, a load current detection unit that detects the magnitude of the load current, and a leakage current detection unit that detects the magnitude of the leakage current of the load current.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the invention described in Patent Document 1, there is room for improvement in the method for calculating the leakage current.

Means for Solving the Problems

[0005] The insulation monitoring device according to the first aspect of the present invention is an insulation monitoring device that monitors a leakage current related to a switching device that controls power supplied from a power source to a load, and includes a leakage current acquisition unit that acquires a leakage current value detected by a leakage current detection unit provided at least on one of between the switching device and the load and between the switching device and the primary side, a primary side voltage acquisition unit that acquires a power source voltage value that is the voltage value of the power source, and a period specification unit that specifies an on period that is a period during which power is supplied to the load by the switching device. The period during which power is not supplied to the load by the switching device is defined as an off period, and the insulation monitoring device further includes an estimation unit that estimates a normalized leakage current value that is the effective value of the leakage current value when the on period is 100% based on the power source voltage value and based on the leakage current value during the on period. The insulation monitoring method according to the second aspect of the present invention is an insulation monitoring method executed by an insulation monitoring device that monitors a leakage current related to a switching device that controls power supplied from a power source to a load, and includes a leakage current detection step of acquiring a leakage current value detected by a leakage current detection unit provided at least on one of between the switching device and the load and between the switching device and the primary side, a primary side voltage acquisition step of acquiring a power source voltage value that is the voltage value of the power source, and a period specification step of specifying an on period that is a period during which power is supplied to the load by the switching device. The period during which power is not supplied to the load by the switching device is defined as an off period, and the insulation monitoring method further includes an estimation step of estimating a normalized leakage current value that is the effective value of the leakage current value when the on period is 100% based on the power source voltage value and based on the leakage current value during the on period.

Effects of the Invention

[0006] According to the present invention, the leakage current can be accurately calculated.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 7

Figure 8

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Figure 10

Figure 11

Modes for Carrying Out the Invention

[0008] —First Embodiment— Hereinafter, with reference to FIGS. 1 to 6, a first embodiment of an insulation monitoring device according to the present invention will be described.

[0009] Figure 1 is a hardware configuration diagram of the insulation monitoring system according to the first embodiment. The insulation monitoring device system 100 includes an insulation monitoring device 1, a thyristor regulator 2 which is a switching device, a power supply 91, a primary voltmeter 92, a load ammeter 93, a leakage current detection device 94, a heating element 95, and an alarm device 96. In FIG. 1, solid lines indicate power paths and dashed lines indicate signal paths. However, since current values or voltage values may be used for signal transmission, power may flow through the signal paths indicated by dashed lines. For the information transmission from the primary voltmeter 92, the load ammeter 93, and the leakage current detection device 94 to the insulation monitoring device 1, analog communication or digital communication may be used. Digital communication includes Profibus, IEEE802.3, etc.

[0010] For the sake of description, each of the primary voltmeter 92, the load ammeter 93, and the leakage current detection device 94 does not necessarily have to be an independently used device, and for example, it does not have to be provided with a display unit. The primary voltmeter 92 can also be called a "voltage measurement unit" or a "voltage measurement module". The load ammeter 93 can also be called a "current measurement unit" or a "current measurement module". The leakage current detection device 94 can also be called a "leakage current measurement unit" or a "leakage current measurement module".

[0011] The power supply 91 is an AC power supply that serves as a power source for the heating element 95. The power supply 91 is grounded. In the present embodiment, the side closer to the power supply 91 than the thyristor regulator 2 in the power path is called the "primary side", and the side closer to the heating element 95 than the thyristor regulator 2 is called the "secondary side". The primary voltmeter 92 measures the voltage on the primary side and outputs the information to the insulation monitoring device 1. The primary voltmeter 92 measures the voltage at a high frequency, and the measurement frequency is, for example, several times or more the power supply frequency. For example, when the power supply frequency is 50 Hz, the primary voltmeter 92 measures at 1 kHz or more.

[0012] The load current meter 93 measures the current flowing from the power supply 91 to the heating element 95, which is the load (hereinafter referred to as the "load current"), and outputs the measured current value to the insulation monitoring device 1. Since the load current meter 93 repeats the measurement, the insulation monitoring device 1 can obtain current values in time series, so to speak, the waveform of the current values, as will be described later. The leakage current detection device 94 measures the leakage current and outputs the measured leakage current value to the insulation monitoring device 1. Since the leakage current detection device 94 repeats the measurement, the insulation monitoring device 1 can obtain leakage current values in time series, so to speak, the waveform of the leakage current values, as will be described later. Note that "leakage current" is also called "leakage current". In the present embodiment, the leakage current detection device 94 measures the leakage current generated in the heating element 95. The leakage current detection device 94 is, for example, a zero-phase current transformer (ZCT).

[0013] The heating element 95 is connected to the power supply 91 via the thyristor regulator 2. That is, the heating element 95 is arranged on the secondary side of the thyristor regulator 2. The heating element 95 generates heat when power is supplied. The heating element 95 has a period during which power is supplied and a period during which power supply is cut off due to the operation of the thyristor regulator 2. Hereinafter, the period during which power is supplied is called the "on period", and the period during which power supply is cut off is called the "off period". The notification device 96 is a device that notifies an abnormality using at least one of sound, vibration, light, and video. The notification device 96 is, for example, a speaker, a light, a liquid crystal display, or the like.

[0014] The thyristor regulator 2 includes a CPU 21, a voltmeter 22, and a thyristor 23. The CPU 21 expands and executes a program stored in a ROM (not shown) in a RAM (not shown). The CPU 21 controls the two thyristors 23 so that the temperature of the heating element 95 becomes the set temperature, for example. Specifically, the CPU 21 controls the power supply to the heating element 95 by applying a voltage to the gate terminal of the thyristor 23. The thyristor regulator 2 adopts a phase control method and controls the thyristor 23 based on the timing when the voltage of the power supply 91 measured by the voltmeter 22 passes through 0V.

[0015] Various known methods can be used to control the thyristor 23 by the CPU 21. For example, the CPU 21 acquires the output of a thermometer (not shown) provided near the heating element 95, and determines the range of the phase for applying a voltage to the gate terminal of the thyristor 23 based on a value obtained by multiplying the deviation from the target value by a predetermined gain. Then, with the timing when the voltage of the power supply 91 becomes positive exceeding 0V set as 0 degrees, the gate terminal voltage of the thyristor 23 is applied within the range of the phase determined previously.

[0016] The insulation monitoring device 1 calculates a normalized leakage current based on the outputs of the primary voltage meter 92, the load current meter 93, and the leakage current detection device 94. Details will be described later.

[0017] Figure 2 is a hardware configuration diagram of the insulation monitoring device 1. The insulation monitoring device 1 includes a monitoring CPU 81 which is a central processing unit, a monitoring ROM 82 which is a read-only storage device, a monitoring RAM 83 which is a read-write storage device, a sensor value acquisition unit 84 which acquires the measured values of sensors, and an output unit 85.

[0018] The monitoring CPU 81 expands and executes the program stored in the monitoring ROM 82 in the monitoring RAM 83 to perform various operations described later. The insulation monitoring device 1 may be realized by an FPGA (Field Programmable Gate Array) which is a rewritable logic circuit or an ASIC (Application Specific Integrated Circuit) which is an integrated circuit for specific applications instead of the combination of the monitoring CPU 81, the monitoring ROM 82, and the monitoring RAM 83. Also, the insulation monitoring device 1 may be realized by a combination of different configurations, for example, a combination of the monitoring CPU 81, the monitoring ROM 82, the monitoring RAM 83, and the FPGA instead of the combination of the monitoring CPU 81, the monitoring ROM 82, and the monitoring RAM 83.

[0019] The sensor value acquisition unit 84 acquires the outputs of the primary voltage meter 92, the load current meter 93, and the leakage current detection device 94. The sensor value acquisition unit 84 has a hardware configuration corresponding to the communication method adopted by the primary voltage meter 92, the load current meter 93, and the leakage current detection device 94. For example, when the primary voltage meter 92 outputs the measured value as an analog signal of 4 - 20 mA, the sensor value acquisition unit 84 includes an AD converter. The output unit 85 outputs a signal to the notification device 96 based on the calculation result of the insulation monitoring device 1. The output unit 85 has a hardware configuration that outputs a signal available to the notification device 96. For example, when the notification device 96 is a light, the output unit 85 is a DA converter that outputs an operation signal to the light. For example, when the notification device 96 is a liquid crystal display, the output unit 85 is a display control device that outputs a video signal to the liquid crystal display.

[0020] Figure 3 is a functional block diagram showing the functions of the insulation monitoring device 1. The insulation monitoring device 1 includes a period specifying unit 11, a leakage current acquisition unit 12, a primary side voltage acquisition unit 13, an estimation unit 14, and a notification unit 15. The period specifying unit 11 specifies an off period, which is a period during which the power supply to the heating element 95 is cut off, based on the output of the load current meter 93. The period specifying unit 11 is realized by the calculation of the monitoring CPU 81 and the sensor value acquisition unit 84.

[0021] The leakage current acquisition unit 12 acquires the leakage current value measured by the leakage current detection device 94. The leakage current acquisition unit 12 is realized by the calculation of the monitoring CPU 81 and the sensor value acquisition unit 84. In this embodiment, although the leakage current occurs during the on period when power is supplied to the heating element 95, it does not occur during the off period when power is not supplied to the heating element 95. The on period and the off period are determined by the calculation of the CPU 21 of the thyristor regulator 2, and at least the on period and the off period are not constant. Therefore, it is not possible to accurately estimate the degree of insulation breakdown in the heating element 95 only based on the magnitude of the leakage current value acquired by the leakage current acquisition unit 12.

[0022] The primary voltage acquisition unit 13 acquires the primary voltage value measured by the primary voltmeter 92. The primary voltage acquisition unit 13 is realized by the calculation by the monitoring CPU 81 and the sensor value acquisition unit 84. The estimation unit 14 calculates the normalized leakage current using the leakage current value during the on-period. The normalized leakage current is the effective value of the leakage current indicating the degree of the original insulation breakdown when the on-period is 100%, for example, the effective value of the leakage current complementing the off-period when the on-period and the off-period are 1:1, that is, 50% each, or the effective value of the leakage current when the on-period is 100% and there is no off-period. In the present embodiment, the effective value of the leakage current when the on-period is 100% and there is no off-period is defined as the normalized leakage current.

[0023] The notification unit 15 outputs the information on the normalized leakage current calculated by the estimation unit 14 to the notification device 96. The notification unit 15 may output the value of the normalized leakage current as it is, or may output the relationship with a predetermined threshold value. For example, the notification unit 15 may classify into any of the three levels of safety, caution, and danger according to the magnitude relationship between the two predetermined threshold values and the normalized leakage current, and output the classification result by voice, video, light, etc.

[0024] FIG. 4 is a diagram for explaining the operation of the insulation monitoring system. FIG. 4 shows four time-series changes. In order from the top, they are the primary voltage measured by the primary voltmeter 92, the load current measured by the load current meter 93, the off-period and on-period specified by the period specifying unit 11, and the leakage current measured by the leakage current detection device 94. However, FIG. 4 illustrates the case where the phases of the voltage and the current coincide. Also, the hatching in FIG. 4 is described to emphasize the presence of the measured values. +TH and -TH described in the graph of the load current are threshold values to be described later.

[0025] The monitoring CPU 81 samples the primary-side voltage at high speed and can identify the timing when the primary-side voltage passes through 0V. In FIG. 4, the timing when the primary-side voltage crosses 0V from minus to plus is set as time t0. Then, the next timing when the primary-side voltage crosses 0V from plus to minus is set as time t5, and the next timing when the primary-side voltage crosses 0V from minus to plus is set as time t10.

[0026] The load current shown in the second stage was zero from time t0 to time t1. The magnitude of the load current at time t1 was measured, and then it increased, reached a maximum value, and then turned to decrease, becoming zero at time t5. After that, it was zero until time t6, decreased after being measured at time t6, turned to increase after passing through a minimum value, and became zero again at time t10.

[0027] The period specifying unit 11 specifies the period until the absolute value of this load current exceeds a predetermined threshold TH and becomes zero as the on period, and the other period, in other words, the period when the absolute value of the load current is less than the predetermined threshold from zero, as the off period. In other words, the period specifying unit 11 determines the start of the on period when the load current deviates from the range of +TH to -TH, and then determines the end of the on period when the load current first becomes zero. In the example shown in FIG. 4, as shown in the third stage, the period specifying unit 11 specifies the time t0 to t1 and the time t5 to t6 as the off periods, and the time t1 to t5 and the time t6 to t10 as the on periods.

[0028] The leakage current shown in the fourth stage is the leakage current measured by the leakage current detection device 94. In FIG. 4, the time periods from t0 to t1 and from t5 to t6 are indicated by broken lines, and the time periods from t1 to t5 and from t6 to t10 are indicated by solid lines. Actually, the leakage current measured by the leakage current detection device 94 at the time periods from t0 to t1 and from t5 to t6 is a value with noise added to zero. Since no power is supplied to the heating element 95 during the off period, no leakage current occurs. However, in the present embodiment, in order to calculate the normalized leakage current, the estimation unit 14 estimates the leakage current during the off period by a method described later. Also, since the measured current is an apparent current rather than a true value, the effective value is calculated as described later. The leakage current estimated by the estimation unit 14 is a value as indicated by the broken line.

[0029] (Processing of the Estimation Unit 14) The estimation unit 14 performs a Fourier transform on the leakage current values during the on period to identify the fundamental wave component. However, since the information on the leakage current values during the off period is missing, a window function is used to reduce the weighting of the off period. Also, in this Fourier transform, the vector of the primary side voltage is used as the real number reference. The estimation unit 14 uses the magnitude and phase of the fundamental wave component obtained by the Fourier transform for later processing. For example, consider the case where the leakage current value LI is obtained by the Fourier transform as in the following Equation 1. However, the DC component is omitted in Equation 1.

[0030] LI = A 1 cos(ωt + φ 1 ) + A 2 cos(2ωt + φ 2 ) + ·· (Equation 1)

[0031] In this case, the estimation unit 14 uses the magnitude A 1 of the apparent leakage current and the phase φ 1 to calculate the effective leakage current NE normalized as in the following Equation 2.

[0032] NE = A 1 cos(φ 1 ) (Equation 2)

[0033] (Flowchart) FIG. 5 is a flowchart showing the frequency determination process executed by the estimation unit 14. The estimation unit 14 executes the frequency determination process each time the power supply of the insulation monitoring device 1 is turned on. In the frequency determination process, the primary voltage output by the primary voltage meter 92 is sequentially read and judged. For the sake of simplicity, the description of the process of reading the output of the primary voltage meter 92 is omitted in FIG. 5. Also, the frequency determination process described below is premised on the power supply frequency being either 50 Hz or 60 Hz.

[0034] First, in step S311, the estimation unit 14 determines whether the primary voltage has changed from minus to plus. If the estimation unit 14 determines that it has not changed from minus to plus, it stays in step S311, and if it determines that it has changed from minus to plus, it proceeds to step S312. Since the power supply 91 is an AC power supply and the voltage changes in a short time period, but the phase of the voltage at the timing when the frequency determination process starts is indefinite, in step S311, it waits until the voltage value reaches a specific state.

[0035] In step S312, the estimation unit 14 starts time counting and proceeds to step S313. In step S313, the estimation unit 14 determines whether the primary voltage has changed from plus to minus. If the estimation unit 14 determines that it has not changed from plus to minus, it stays in step S313, and if it determines that it has changed from plus to minus, it proceeds to step S314. In step S314, the estimation unit 14 ends the time counting started in step S312.

[0036] In the subsequent step S315, the estimation unit 14 determines the value of the time count. When the estimation unit 14 determines that the time count is "10 ms", it proceeds to step S316 and determines that the power supply frequency is "50 Hz". When the estimation unit 14 determines that the time count is "8.3 ms", it proceeds to step S318 and determines that the power supply frequency is "60 Hz". When the estimation unit 14 determines that the time count is "other", that is, neither "10 ms" nor "8.3 ms", it proceeds to step S317 and outputs an error. When any of steps S316 to S318 is executed, the process shown in FIG. 5 ends.

[0037] FIG. 6 is a flowchart showing the measurement process executed by the estimation unit 14. The estimation unit 14 does not record the leakage current value acquired by the leakage current acquisition unit 12 as it is, but records only the measured value during the on period as described below. The estimation unit 14 executes the measurement process when the power supply of the insulation monitoring device 1 is turned on. Since the estimation unit 14 continuously executes the measurement process while the insulation monitoring device 1 is operating, there is no end in FIG. 6.

[0038] In step S321, the estimation unit 14 acquires the sensor values, that is, the primary side voltage value output by the primary voltage meter 92, the load current value acquired by the period specifying unit 11, and the leakage current value acquired by the leakage current acquisition unit 12. In the subsequent step S322, the estimation unit 14 determines whether the primary side voltage has crossed zero. Zero crossing means that the positive and negative of the previous measured value and the current measured value are different. Zero crossing applies to both the change from plus to minus and the change from minus to plus. In step S322, when the estimation unit 14 determines that the primary side voltage value has crossed zero, it proceeds to step S323, and when it determines that there is no zero crossing, it returns to step S321. Step S322 is in a state of waiting for the zero crossing point of the voltage, for example, the timing at time t0 in FIG. 4, when starting the first measurement.

[0039] In step S323, the estimation unit 14 determines whether the absolute value of the load current value acquired immediately before is greater than or equal to a predetermined threshold value. When the estimation unit 14 determines that the absolute value of the load current value is greater than or equal to the predetermined threshold value, it proceeds to step S324. When it determines that the absolute value of the load current value is less than the predetermined threshold value, it proceeds to step S326. In step S324, the estimation unit 14 records the latest leakage current value as the measurement value during the on-period and proceeds to step S325.

[0040] In step S325, the estimation unit 14 determines whether the acquired latest primary-side voltage has crossed zero. In step S325, when the estimation unit 14 determines that the primary-side voltage value has crossed zero, it returns to step S323 via the circled A. When it determines that it has not crossed zero, it proceeds to step S327.

[0041] In step S326, the estimation unit 14 acquires the sensor values, that is, the primary-side voltage value output by the primary voltage meter 92, the load current value acquired by the period specifying unit 11, and the leakage current value acquired by the leakage current acquisition unit 12, and returns to step S323. The loop between step S323 and step S326 is waiting for the start of the on-period, corresponding to the processing at times t0 to t1 or times t5 to t6 in FIG. 4. Note that the processing of step S323 and step S326 is actually executed by the period specifying unit 11.

[0042] In step S327, the estimation unit 14 acquires the sensor values, that is, the primary-side voltage value output by the primary voltage meter 92, the load current value acquired by the period specifying unit 11, and the leakage current value acquired by the leakage current acquisition unit 12, and returns to step S324. The loop between step S323 and step S326 continues recording until the on-period ends, corresponding to the processing at times t1 to t5 or times t6 to t10 in FIG. 4. Note that the case of making an affirmative determination in step S325 means that a new measurement cycle has started, so it enters a state where it has exceeded time t0 in FIG. 4 again, and enters the loop between step S323 and step S326.

[0043] According to the above-described first embodiment, the following operational effects can be obtained. (1) The insulation monitoring device 1 monitors the leakage current related to the thyristor regulator 2 that controls the power supplied from the power supply 91 to the heating element 95 which is the load. The insulation monitoring device 1 includes a leakage current acquisition unit 12 that acquires the leakage current value detected by the leakage current detection device 94 provided between the thyristor regulator 2 and the heating element 95, a primary side voltage acquisition unit 13 that acquires the voltage value of the power supply, and a period specifying unit 11 that specifies the on-period which is the period during which power is supplied to the load by the thyristor regulator 2. The period during which power is not supplied to the heating element 95 by the thyristor regulator 2 is defined as the off-period. The insulation monitoring device 1 includes an estimation unit 14 that estimates the normalized leakage current value which is the effective value of the leakage current value when the on-period is 100% based on the voltage value of the power supply with reference to the leakage current value during the on-period. Therefore, the insulation monitoring device 1 can accurately calculate the leakage current.

[0044] (2) The estimation unit 14 performs Fourier transform on the leakage current value during the on-period to estimate the normalized leakage current value.

[0045] (3) The load to which the thyristor regulator 2 supplies power is the heating element 95. Since the power supply to the heating element 95 is switched on and off according to the target temperature, the occurrence of leakage current is not uniform, and it is not easy to estimate the degree of insulation breakdown. However, by using the method according to this embodiment, the degree of insulation breakdown can be evaluated by the normalized leakage current value.

[0046] (4) The period specifying unit 11 specifies the on-period based on the magnitude of the load current which is the current passing through the thyristor regulator 2. Therefore, no special processing is required for the thyristor regulator 2.

[0047] (5) It includes a notification unit 15 that notifies based on the normalized leakage current value. Therefore, the calculation result can be notified to the outside.

[0048] (Modification Example 1) In the above-described first embodiment, the estimation unit 14 performs Fourier transform using the leakage current value during the on-period. However, the estimation unit 14 may estimate the leakage current value during the off-period and perform Fourier transform using the estimated leakage current value during the off-period and the measured leakage current value during the on-period. For the estimation of the leakage current value during the off-period by the estimation unit 14, a linear approximation formula or a quadratic approximation formula may be used, or mirror inversion may be used when the on-period is longer than the off-period.

[0049] The estimation of the leakage current value by mirror inversion focuses only on the fundamental wave and utilizes the fact that it is a clean sine wave or cosine wave and has symmetry. For example, when the off-period is from 0 to 30 degrees and the fundamental wave is a cosine wave, the value at 360 to 330 degrees is used. Since the frequency of the fundamental wave is specified by the aforementioned frequency determination process, if the timing at which the leakage current value changes from negative to positive can be specified, the relationship between time and the phase of the fundamental wave can be specified.

[0050] According to this Modification 1, the following operational effects can be obtained. (6) The estimation unit 14 estimates the leakage current value during the off-period, performs Fourier transform on the obtained leakage current value during the on-period and the estimated leakage current value during the off-period, and estimates the normalized leakage current value.

[0051] (Modification 2) In the above-described first embodiment, the thyristor regulator 2 supplies power to the heating element 95. However, the recipient to which the thyristor regulator 2 supplies power is not limited to the heating element 95. The recipient to which the thyristor regulator 2 supplies power may be any device that consumes AC power, and various loads may be used as the power supply destination. Also, the thyristor regulator 2 may supply power to the load via a step-up or step-down transformer. In this case, a leakage current detection device 94 may be provided between the transformer and the load to evaluate only the leakage current of the load, or a leakage current detection device 94 may be provided between the thyristor regulator 2 and the transformer to evaluate the leakage current of the transformer and the load.

[0052] (Modification Example 3) In the above-described first embodiment, the insulation monitoring device 1 is connected to the notification device 96, and the insulation monitoring device 1 includes the notification unit 15. However, the insulation monitoring device 1 may not include the notification unit 15. In this case, for example, the insulation monitoring device 1 may record the normalized effective leakage current, which is the calculation result, together with the time in a non-volatile storage medium (not shown) and read it out afterwards, or may output the calculation result by communication.

[0053] (Modification Example 4) In the above-described first embodiment, the load current meter 93 is arranged on the secondary side of the thyristor regulator 2, that is, on the side of the heating element 95. However, the load current meter 93 may be arranged on the primary side of the thyristor regulator 2, that is, on the side of the power supply 91.

[0054] (Modification Example 5) In the above-described first embodiment, the primary voltage meter 92 outputs the measured value to the insulation monitoring device 1. However, the primary voltage meter 92 does not necessarily have to output the measured value itself to the insulation monitoring device 1, and may output only the timing signals at the timing when the measured value changes from minus to plus and at the timing when the measured value changes from plus to minus.

[0055] - Second Embodiment - Referring to FIG. 7, a second embodiment of the insulation monitoring system will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and the differences will be mainly described. For points not particularly described, they are the same as those in the first embodiment. In this embodiment, it is mainly different from the first embodiment in that a control signal is obtained from the thyristor regulator.

[0056] Figure 7 is a hardware configuration diagram of the insulation monitoring system in the second embodiment. The difference from the first embodiment is that the thyristor regulator 2 also outputs a control signal to the thyristor 23 to the insulation monitoring device 1. Also, in this embodiment, the insulation monitoring system may not include the load current meter 93. The CPU 21 of the thyristor regulator 2 outputs a signal to the insulation monitoring device 1 when starting and ending the voltage application to the gate terminal of the thyristor 23.

[0057] The period specifying unit 11 of the insulation monitoring device 1 specifies the on-period and the off-period based on the signal output by the CPU 21 of the thyristor regulator 2. Since the other configurations and operations are the same as those in the first embodiment, the description is omitted.

[0058] According to the second embodiment described above, the following operational effects can be obtained. (7) The period specifying unit 11 specifies the on-period based on the control signal output by the thyristor regulator 2. Therefore, the load current meter 93 is unnecessary, and the on-period can be accurately grasped.

[0059] - Third Embodiment - Referring to Figure 8, a third embodiment of the insulation monitoring system will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and the differences will be mainly described. Regarding points not particularly described, they are the same as those in the first embodiment. In this embodiment, mainly, the position where the leakage current detection device 94 for measuring the leakage current is arranged is different from that in the first embodiment.

[0060] FIG. 8 is a hardware configuration diagram of the insulation monitoring system according to the third embodiment. In FIG. 8, the leakage current detection device 94 is arranged on the primary side of the thyristor regulator 2, that is, on the side of the power supply 91. Therefore, the leakage current detection device 94 in the present embodiment measures the leakage current not only in the heating element 95 but also in the thyristor regulator 2. In the first embodiment, the leakage current occurred only during the on-period when power was supplied to the heating element 95 and did not occur during the off-period when power was not supplied to the heating element 95. However, in the present embodiment, there is a possibility that leakage current may occur even during the off-period when power is not supplied to the heating element 95. Note that in the present embodiment, the leakage current generated by the heating element 95 and the leakage current generated by the thyristor regulator 2 cannot be distinguished. Since the configuration and operation of the insulation monitoring device 1 are the same as those in the first embodiment, the description thereof is omitted.

[0061] According to the third embodiment described above, various hardware configurations can be adopted.

[0062] (Modification of the Third Embodiment) FIG. 9 is a hardware configuration diagram of the insulation monitoring system according to a modification of the third embodiment. Comparing FIG. 9 with FIG. 8, the first leakage current detection device 94A is arranged at the position of the leakage current detection device 94 in FIG. 8, and the second leakage current detection device 94B is arranged at the position of the leakage current detection device 94 in FIG. 1. The first leakage current detection device 94A detects the total of the leakage current due to the heating element 95 and the leakage current in the thyristor regulator 2 in the same manner as in the third embodiment. The second leakage current detection device 94B detects the leakage current in the heating element 95.

[0063] The estimation unit 14 of the insulation monitoring device 1 calculates the leakage current normalized with respect to the outputs of the first leakage current detection device 94A and the second leakage current detection device 94B, respectively. The calculation method is the same as that in the first embodiment. Further, the notification unit 15 of the insulation monitoring device 1 notifies the outputs of the first leakage current detection device 94A and the second leakage current detection device 94B, respectively. Since the other configurations and operations are the same as those in the first embodiment, the description thereof is omitted.

[0064] In this modified example, the normalized leakage current value based on the measured value of the second leakage current detection device 94B represents the insulation degradation state of the heating element 95. Also, the value obtained by subtracting the normalized leakage current value based on the measured value of the second leakage current detection device 94B from the normalized leakage current value based on the measured value of the first leakage current detection device 94A represents the insulation degradation state of the thyristor regulator 2.

[0065] - Fourth Embodiment - Referring to FIG. 10, a fourth embodiment of the insulation monitoring system will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and the differences will be mainly described. Regarding points not particularly described, they are the same as those in the first embodiment. In this embodiment, it is different from the first embodiment mainly in that the hardware constituting the insulation monitoring device has increased.

[0066] FIG. 10 is a hardware configuration diagram of the insulation monitoring system in the fourth embodiment. The insulation monitoring device 1B includes an insulation monitoring core device 1A corresponding to the insulation monitoring device 1 in the first embodiment, a primary voltmeter 92, a load current meter 93, and a leakage current detection device 94. The operations of the primary voltmeter 92, the load current meter 93, and the leakage current detection device 94 are the same as those in the first embodiment. The configuration and operation of the insulation monitoring core device 1A are the same as those of the insulation monitoring device 1 in the first embodiment.

[0067] According to the fourth embodiment described above, the following operational effects can be obtained. (8) The insulation monitoring device 1B includes a leakage current detection device 94, a primary voltmeter 92 for measuring the voltage value, and a load current meter 93 for measuring the load current. Therefore, insulation monitoring can be achieved simply by installing the insulation monitoring device 1B with respect to the existing thyristor regulator 2.

[0068] (Modified Example of the Fourth Embodiment) FIG. 11 is a hardware configuration diagram of an insulation monitoring system in a modification of the fourth embodiment. Comparing FIG. 11 with FIG. 10, the insulation monitoring device 1C further includes a thyristor regulator 2 in addition to the configuration of the insulation monitoring device 1B. The configuration and operation of the thyristor regulator 2 are the same as those in the first embodiment.

[0069] According to this modification, the following operational effects can be obtained. (9) The insulation monitoring device 1C includes a thyristor regulator 2. In other words, the insulation monitoring device 1C is a thyristor regulator having an insulation monitoring function.

[0070] In each of the above-described embodiments and modifications, the configuration of the functional blocks is merely an example. Some functional configurations shown as separate functional blocks may be integrated, or the configuration represented by one functional block diagram may be divided into two or more functions. Also, a part of the functions of each functional block may be provided by other functional blocks.

[0071] In each of the above-described embodiments and modifications, the program is assumed to be stored in a ROM (not shown), but the program may be stored in a rewritable non-volatile memory. Also, the insulation monitoring device may include an input / output interface (not shown), and the program may be read from another device via the input / output interface and a medium available to the insulation monitoring device when necessary. Here, the medium refers to, for example, a removable storage medium attached to the input / output interface, or a communication medium, that is, a wired, wireless, optical, etc. network, or a carrier wave or digital signal propagating through the network. Also, part or all of the functions realized by the program may be realized by a hardware circuit or an FPGA.

[0072] Each of the above-described embodiments and modifications may be combined. Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention. The application target of the present invention is not limited to the thyristor regulator, and can be applied to various switching devices that control the load current.

Explanation of Signs

[0073] 1, 1B, 1C... Insulation monitoring device 2... Thyristor regulator 11... Period specifying section 12... Leakage current acquisition section 13... Primary side voltage acquisition section 14... Estimation section 15... Notification section 94... Leakage current detection device 95... Heating element

Claims

1. An insulation monitoring device for monitoring a leakage current related to a switching device that controls power supplied from a power source to a load, comprising: a leakage current acquisition unit that acquires a leakage current value detected by a leakage current detection unit provided in at least one of between the switching device and the load and between the switching device and the primary side; a primary side voltage acquisition unit that acquires a power source voltage value that is the voltage value of the power source; a period specifying unit that specifies an on-period which is a period during which power is supplied to the load by the switching device; wherein a period during which power is not supplied to the load by the switching device is defined as an off-period; an insulation monitoring device further comprising an estimation unit that estimates a normalized leakage current value which is an effective value of the leakage current value when the on-period is 100% based on the power source voltage value, based on the leakage current value during the on-period.

2. The insulation monitoring device according to Claim 1, wherein the estimation unit performs a Fourier transform on the leakage current value during the on-period to estimate the normalized leakage current value.

3. The insulation monitoring device according to Claim 1, wherein the estimation unit estimates the leakage current value during the off-period, performs a Fourier transform on the acquired leakage current value during the on-period and the estimated leakage current value during the off-period, and estimates the normalized leakage current value.

4. The insulation monitoring device according to Claim 1, wherein the load is a heating element.

5. The insulation monitoring device according to Claim 1, wherein the period specifying unit specifies the on-period based on the magnitude of a load current which is a current passing through the switching device.

6. The insulation monitoring device according to Claim 1, wherein the period specifying unit specifies the on-period based on a control signal output by the switching device.

7. The insulation monitoring device according to Claim 5, further comprising the leakage current detection unit, a voltmeter for measuring the voltage value, and a load current meter for measuring the load current.

8. The insulation monitoring device according to Claim 6, further comprising the leakage current detection unit and a voltmeter for measuring the voltage value.

9. The insulation monitoring device according to Claim 7, An insulation monitoring device further comprising the switching device.

10. In the insulation monitoring device according to Claim 1, An insulation monitoring device further comprising a notification unit that notifies based on the normalized leakage current value.

11. An insulation monitoring method executed by an insulation monitoring device that monitors a leakage current related to a switching device that controls power supplied from a power source to a load, A leakage current detection step of obtaining a leakage current value detected by a leakage current detection unit provided at least on one of between the switching device and the load and between the switching device and the primary side; A primary side voltage acquisition step of obtaining a power source voltage value that is the voltage value of the power source; A period specification step of specifying an on period that is a period during which power is supplied from the switching device to the load, including: A period during which power is not supplied from the switching device to the load is defined as an off period, An insulation monitoring method including an estimation step of estimating a normalized leakage current value that is an effective value of the leakage current value when the on period is 100% based on the power source voltage value based on the leakage current value during the on period.

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