KR20080015752A - Low voltage on-line insulation monitoring system - Google Patents

Abstract

A low voltage on-line insulation monitoring system is provided to detect and monitor an effective leakage current value corresponding to an insulation resistance value or a resistance component, accurately. A low voltage on-line insulation monitoring system comprises a low frequency overlapping device, a zero-phase current transformer(9,11), a current/voltage converter(61), an amplifier(62,64), a filter(63), a frequency detector(66), an analog/digital converter(65), and a control device(70). The low frequency overlapping device overlaps two kinds of low frequency signal voltages(f1 Hz, f2 Hz) to a low voltage line, separately. The zero-phase current transformer detects a leakage current flowing between the low voltage line and ground. The frequency detector determines whether the frequency of the low frequency signal is f1 Hz or f2 Hz using a leakage current component.

Description

Low Voltage On-line Insulation Monitoring System {Low Voltage On-Line Insulation Monitoring System}

The present invention relates to a live wire insulation monitoring device which detects and monitors a resistance component directly related to a ground fault regardless of the magnitude of the capacitance existing at the wire line and the load input terminal in the live state without interrupting the low voltage converter insulation state. there is,

Low frequency (f1, f2) of two components is installed by low frequency superposition device separately installed on the low voltage side of the transformer for the insulation monitoring device COST, and for easy insulation measurement and installation at the site where insulation monitoring is to be performed. When alternatingly superimposed on an AC circuit of a commercial frequency and superimposing the low frequency signal voltage of f1 Hz, the leakage current (ifa1) flowing to the ground of the converter and the load by this low frequency signal voltage and the low frequency signal of f2 Hz described above When the voltage is superimposed, the low-frequency signal voltage detects the leakage current (ifa2) flowing to the ground of the converter and the load, respectively, and then calculates from the leakage current of two components, the ifa1 leakage current and the ifa2 leakage current. By removing the capacitance component irrelevant to the insulation state (leakage) and calculating only pure resistance component, the insulation resistance value or effective leakage prevention directly related to the insulation state (leakage) The present invention relates to a live insulation monitoring device of a low-voltage converter that displays and monitors a threshold value.

Conventionally, in order to detect and monitor the insulation state of a low voltage converter, the insulation resistance meter method of measuring the insulation resistance between the converter and the earth ground with an insulation resistance meter by shutting off the switch connected to the high voltage / low voltage transformer, that is, by power failure, and the switch connected to the high voltage / low voltage transformer There is a leakage current meter that detects leakage current and insulation deterioration by detecting a leakage current flowing through the neutral point of the low voltage side of the transformer or two ground wires which are grounded once in a live state without being cut off. In these methods, the insulation resistance meter must be interrupted when measuring the insulation state of the converter. Therefore, there is a problem that the power supply must be stopped at the place where electricity is continuously used. The method of monitoring the insulation state by measuring the leakage current flowing through the 2 types of ground wire such as clamp meter (leakage ammeter) or earth leakage alarm in the live state without the leakage current and the line due to the insulation resistance between the converter and the ground is long. Is detected by the vector sum of the leakage current caused by the capacitance generated in the capacitor and the capacitance of the noise filter inserted into the input of the load equipment, and thus the capacitance is reduced even when the insulation resistance is very good. If it is very large, the leakage current caused by the capacitance component also increases, so that the insulation state is poor, that is, a short circuit or There has been a problem that the fault detection is determined to have occurred.

Due to this problem, many foreign countries apply the low frequency overlapping method as shown in FIG. 1 used to measure the leakage current corresponding to the insulation resistance component due to the insulation state in the live state. A low current such as a low frequency superimposed on the low frequency overlapping device 13 flowing to the second type ground line 2 with the image current transformer 9 or 11 is detected, and the reactive component current corresponding to the capacitance component at this low frequency leakage current is detected. Interconnection with the low frequency overlapping device 13 with a separate synchronization signal input line 15 to synchronize with the frequency of the low frequency overlapping device 13 to remove the active component current corresponding to the insulation resistance. The low frequency voltage signal corresponding to point a of the second type grounding line 2 corresponding to the secondary side of the overlapping transformer 7 which is the output of the signal should be connected to the insulation monitoring device 14. The connection line used for synchronizing with the low frequency signal has a problem that it is inconvenient to be applied in actual field because many places are difficult to connect in the long distance. So, in order to solve this problem, Utility Model No. 20-2005-0024602 filed by the present applicant having the circuit configuration as shown in Figs. 2 and 3 is isolated from the leakage current of two kinds of low frequency components, f1 Hz and f2 Hz. The resistance was composed of a device using the method of calculating the insulation resistance R using the following equation.

This apparatus will be described in more detail with reference to FIGS. 2 and 3 as follows.

Two kinds of low-frequency signal voltages, superimposed transformer (7) and f1 Hz and f2 Hz, are placed between the neutral point of the high-voltage / low-voltage transformer (1) or the second earth ground (2) connected between the one earth point and the second earth (6). The low-voltage superposition device 8, which is generated at the same time, is superimposed on the AC low-voltage converter of the commercial frequency (50 Hz or 60 Hz) of the low-voltage converter 4, and the low-voltage signal is applied by the two kinds of low-frequency signal voltages applied simultaneously. The leakage current flowing between the furnace 4 and the earth ground 12 is detected by the image current transformer 9 or 11 connected to the insulation monitoring device 10, and the leakage current detected by the image current transformer 9 or 11 above. Is converted into a voltage value by the current / voltage converter 21, and the voltage value converted by the voltage converter 21 is amplified by the amplifier 22, and then the band pass filter 23a and f1 for f1 are used. Through the amplifier 24a and the analog / digital converter 25a for f1, the leakage current of the f1 Hz low frequency component The corresponding if1a value, the f2 bandpass filter 23b, the f2 amplifier 24b, and the f2 analog / digital converter 25b, respectively, extract the if2a value corresponding to the leakage current of the f2 Hz low frequency component, and control the controller. In (30), a method of calculating the insulation resistance R of the pure active ingredient corresponding to the ground fault, that is, removing the leakage current component of the reactive component due to the capacitance is used.

However, since the device overlaps two kinds of low frequency signal voltages, f1 Hz and f2 Hz, in the low frequency superposition device 8, two band pass filters 23a, f2 Hz and f2 Hz to extract two low frequency components, respectively. 23b), two amplifiers 24a, 24b and two analog / digital converters 25a, 25b must be used, so that the circuit is complicated and the band is small when the difference between the two low frequencies of f1 Hz and f2 Hz is small. Since the pass filter has to be designed with high accuracy, the circuit has become more complicated and the device cost has been increased.

Therefore, without connecting the reference voltage input line 15 to the insulation monitoring device or connecting the low frequency base line 15, it is easy to apply a wide range in actual field, and the circuit is simple and economically accurate and corresponds to pure insulation resistance. There has been a need for an insulation monitoring apparatus capable of detecting and monitoring only insulation resistance components.

The present invention has been made to satisfy the above requirements, and does not use the synchronous signal connection line or the reference voltage input line 15, and the circuit is not complicated, so it is economical and eliminates leakage current due to the capacitive component. In order to detect the leakage current or insulation resistance value due to the insulation resistance component, the low frequency superposition device 40 and the superposition transformer 7 or the superposition resistance 7a separately provided on the low voltage side two ground lines of the transformer 1 are provided. Two kinds of low frequency (f1 and f2 Hz) signal voltages are alternately superimposed on the low voltage converter 4, respectively, so that the low current components of the low frequency component f1 Hz and f2 Hz flow to the ground by these two kinds of low frequencies. Leakage current (if2) of low-frequency component of and the leakage current (if0) flowing to the ground due to AC voltage of the existing live-phase AC frequency (60Hz or 50Hz) because the commercial AC is live, the image current transformer (9 or 11) Leakage current of low frequency component flowing between low voltage converter 4 and earth after f1 Hz low frequency overlapping, leakage current (if0 + if1) of AC commercial frequency component, low voltage converter (f2 Hz low frequency overlapping) From the leakage current of the low frequency component flowing between the ground and the earth and the leakage current of the AC commercial frequency component (if0 + if2), the value corresponding to the if1 leakage current of the f1 Hz low frequency component and the if2 leakage current of the f2 Hz low frequency component Instead of using an amplifier, filter, or analog / digital converter, one kind of amplifier, filter, analog / digital converter, and a frequency detector further invented are used to detect the superimposed low frequency components and to detect the frequency detector. It extracts the leakage current component of the low frequency component, and removes the capacitance component from the leakage current of the extracted low frequency component, and calculates pure resistance component only. It is possible to apply the insulation monitoring device that COST provide a cost-effective and accurate insulation resistance or hot-line insulation monitor which can detect the effective leakage current value corresponding to the resistance component monitoring apparatus it is an object.

In order to achieve the object of the present invention, the insulation monitoring device of the low

In order to monitor the insulation of the low voltage transformer through the neutral point of the low voltage side transformer or the ground wire connected to one ground, the low voltage signal flows between the low voltage circuit and the ground by the low frequency signal by superimposing the common AC frequency and other low frequency signal voltage. In the insulation monitoring device for detecting the current with an image current transformer, and detecting and monitoring the leakage current or insulation resistance component of the resistance component directly related to the pure insulation insulation (leakage) between the phase and the ground from the detected leakage current,

Two types of low frequency signal voltages (f1 Hz, f2 Hz) do not overlap at the same time to detect and monitor the effective leakage current or insulation resistance component of the resistance component directly related to the pure insulation reduction (leakage) between the low voltage circuit and the ground. A low frequency overlapping device having a function of being able to overlap each of the low voltage converters individually without; An image current transformer for detecting a leakage current flowing between the low voltage converter and the ground by the low frequency signal voltage superimposed on the low voltage converter by the low frequency overlapping device; A current / voltage converter for converting the leakage current detected by the image current transformer into a voltage signal; An amplifier for amplifying the minute current value or the voltage value corresponding to the leakage current converted by the current / voltage converter; A filter for removing components of a commercial alternating frequency from the leakage current signal amplified by the amplifier; A frequency detector for judging whether the frequency of the low frequency signal superimposed on the low voltage converter by the low frequency superposition device from the leakage current component extracted from the filter is f1 Hz or f2 Hz; An analog / digital converter for converting an analog signal output from the amplifier or filter into a digital signal; And a control device for reading and calculating the data of the analog / digital converter and the frequency detector and various data.

In order to achieve the object of the present invention, the insulation monitoring device of the low

In order to monitor the insulation of the low voltage transformer through the neutral point of the low voltage side transformer or the ground wire connected to one ground, the low voltage signal flows between the low voltage circuit and the ground by the low frequency signal by superimposing the common AC frequency and other low frequency signal voltage. In the insulation monitoring device for detecting the current with an image current transformer, and detecting and monitoring the leakage current or insulation resistance component of the resistance component directly related to the pure insulation insulation (leakage) between the phase and the ground from the detected leakage current,

Two types of low frequency signal voltages (f1 Hz, f2 Hz) do not overlap at the same time to detect and monitor the effective leakage current or insulation resistance component of the resistance component directly related to the pure insulation reduction (leakage) between the low voltage circuit and the ground. A low frequency overlapping device having a function of being able to overlap each of the low voltage converters individually without; An image current transformer for detecting a leakage current flowing between the low voltage converter and the ground by the low frequency signal voltage superimposed on the low voltage converter by the low frequency overlapping device; A current / voltage converter for converting the leakage current detected by the image current transformer into a voltage signal; An amplifier for amplifying a microcurrent value or a voltage value corresponding to the leakage current converted by the current / voltage converter; A filter for removing components of a commercial alternating frequency from the leakage current signal amplified by the amplifier; A frequency detector for judging whether the frequency of the low frequency signal superimposed on the low voltage converter by the low frequency superposition device from the leakage current component extracted from the filter is f1 Hz or f2 Hz; An analog / digital converter for converting an analog signal output from the amplifier or filter into a digital signal; And a control device for reading and controlling the data of the analog / digital converter and the frequency detector and various data. The insulation resistance value or the effective leakage current value is calculated by the following equation.

 (E0: phase voltage of commercial AC, E1: f1 low frequency signal voltage, f1: low frequency (f1 Hz), f2: low frequency (f2 Hz), E2: f2 low frequency signal voltage, a: leakage current measurement circuit) Amplification factor, ifa1: final leakage current value corresponding to f1 low frequency component, ifa2: final leakage current value corresponding to f2 low frequency component)

For commercial AC voltage

Or for low frequency signal voltage

According to the present invention, two types of superposition transformers, superimposed resistors, and low frequency superposition devices connected between the earth and two earth wires connected to the neutral point or one ground point of the high-voltage / low voltage conversion transformer in the live state of the commercial AC frequency as described above. Leakage currents (if0 + if1) and f2 Hz at the superimposition of the low frequency signals (f1, f2) are superimposed on commercial AC frequency converters by time difference, and are superimposed on the F1 Hz low frequency signal through an image transformer in the middle of the two types of ground lines or converters. It detects the leakage current (if0 + if2) flowing at the low frequency signal overlap, removes the leakage current (if0) of the commercial AC voltage through the filter, and extracts only if1 and if2 leakage currents of the low frequency component, and calculates the calculation process. By removing the capacitance component between the phase and ground of the converter and load irrespective of insulation degradation (leakage), and the insulation resistance component directly related to insulation degradation (leakage) or Only the effective leakage current value is calculated, the insulation state is good, but the capacitance is large, which solves the problem of detection and measurement in the form of a short circuit, and in the insulation monitoring device that monitors the insulation state of the low-voltage power line in the live state, the reference voltage input line or low frequency It is possible to effectively monitor and measure the insulation state of low-voltage power line in live state easily without any trouble in applying live insulation monitoring device in the field without connecting signal synchronization line with insulation monitoring device, and detect two low frequency signals Without the use of amplifiers, filters, and analog / digital converters, two low-frequency signals are superimposed on a commercial AC low-voltage converter with a time difference in a low frequency superposition device. Simplify the circuit of the insulation monitoring device using the digital converter It can be effective. In addition, an alarm output unit and a communication unit may be added to configure a device that can be controlled remotely.

Hereinafter, the insulation monitoring device of the low-voltage converter in the live state of the present invention will be described with reference to the accompanying drawings.

As described above, FIG. 1 illustrates an apparatus for monitoring an insulation state of a low-voltage converter currently used in a foreign country in a live state, and FIGS. 2 and 3 illustrate an insulation state of a conventional low-voltage converter filed by the present applicant. It describes a device for monitoring live conditions.

Figure 4 illustrates the concept of the insulation monitoring device in the live state of the present invention, Figure 5 is a first embodiment of the insulation monitoring device 50 according to the present invention, Figure 6 is an insulation monitoring device according to the present invention 7 is a second embodiment of FIG. 7, and FIG. 7 is a third embodiment of the insulation monitoring device 50 according to the present invention, and FIG. 8 is a fourth embodiment of the insulation monitoring device 50 according to the present invention. Yes.

9 to 11 show another embodiment of the leakage current measuring unit 60 inside the insulation monitoring device 50 according to the present invention, and the increase and decrease of the amplifier and the change of the position of the frequency detector 66 are changed. Fig. 12 is an operation explanatory diagram of the low frequency overlapping apparatus 40 of the present invention, and Fig. 13 illustrates the main flow used for the control device 70 inside the insulation monitoring apparatus 50 of the present invention. Another method using the superimposition resistor 7a instead of the superimposed transformer 7 is a method of superimposing the low frequency signal overlapping signal of FIG. Yes. The superposition transformer 7 and the superposition resistance 7a can be applied to both grounding methods, such as the low-voltage connection grounding the neutral point of the wire connection or the one-phase grounding of the delta connection. For the sake of clarity, Fig. 14 shows a diagram of the one-fold grounding method of the delta connection.

The first embodiment of the present invention will be described in more detail. In FIG. 4, electricity is supplied to the low-voltage converter 4 and the load 5 in the state where the switch 3 is closed, that is, in the live state, in the high-voltage / low-voltage conversion transformer 1, and the converter 4 and the load ( 5) Commercial alternating frequency to earth through the insulation resistance (in the present invention, denoted by parallel synthesis resistance as R) and the capacitance (in the present invention, expressed by C). Leakage current (if0) corresponding to the phase voltage (E0) of 50 Hz or 60 Hz (in the present invention, denoted as f0), the neutral point (or single ground point) and earth on the low voltage side of the high / low voltage conversion transformer 1 T1 and t3 hours (f1) according to the values set as shown in the embodiment of FIG. 12 in the overlapping transformer 7 or the overlapping resistor 7a and the low frequency overlapping device 40 separately installed between the two types of ground wires 2 connected to each other. And f2 is a time for easy identification of low frequency signals, but this time can be zero. By not operating the wave signal voltage, the low frequency signal voltage of f1 Hz is output for t2 hours and the low frequency signal voltage of f2 Hz is output for t4 hours. Each of the two superimposed low frequency (f1, f2) signals flows through the switch (3) between the converter (4) and the phase (5) of the load (5) and the earth (L1). Is the signal voltage value of f1 Hz low frequency, E2 is the leakage current (if1, f1 low frequency signal overlapping current) corresponding to f2 Hz low frequency signal voltage value, and leakage current (if2, f2 low frequency signal overlapping current) ) Is detected by the image current transformer ZCT (9 or 11), and the leakage current (if0 + if1, if0 + if2) corresponding to each of two frequency components detected by the image current transformer (9 or 11) is measured by the insulation monitoring device (50). ), The leakage current (if0) of the commercial AC frequency component is removed by amplification and filtering, In the low frequency superimposition device judged by the controller 66, only the leakage currents of two low frequency components of each of the low frequency signals f1 and f2 superimposed are extracted and the extracted leakage currents ifa are f1 Hz low frequencies. When superimposed, it is returned to ifa1 and when f2 Hz low frequency is superimposed to ifa2, the capacitance of the controller 70 is removed through the calculation process of the main flow as shown in FIG. Monitor the insulation state corresponding to the component, ie insulation resistance or effective leakage current.

      5, which corresponds to Embodiment 1 of the present invention, is a method for detecting an insulation resistance component related to an electrical leak by removing the capacitance component irrelevant to an insulation state, that is, not related to an electrical leakage, in the insulation monitoring apparatus 50; A detailed description will be given with reference to FIGS. 12 and 13.

      Various data setting such as t1, t2, t3, t4, f1, f2, E1, E2 in the main flow stored in the ROM 72 of the control device 70 inside the insulation monitoring device 50 as in the embodiment of FIG. When the frequency detection flow 110 is executed while the flow 100 is executed in the data setting unit 76 in the control device 70 of FIG. 5, the frequency of the leakage current input to the frequency detector 66 is detected. . When the low frequency (f1, f2) signal voltages are superimposed through the low voltage converter 4 by the low frequency overlapping order setting of the embodiment as shown in Fig. 12, they are detected by the image current transformer 9 or 11, and the voltage / current converter 61 A filter 63 which converts a leakage current into a voltage value, amplifies the voltage value corresponding to the converted leakage current through the amplifier 62, and passes only a constant low frequency wave (or a band pass filter passing only a predetermined frequency band). And then determine whether the frequency of the value (ifa) corresponding to the leakage current of the low frequency component (f1 or f2) amplified by the amplifier 64 corresponds to f1 Hz or f2 Hz. Alternatively, if the frequency detected through the frequency detector 66 for detection corresponds to f1 Hz, a flow of replacing the value (leakage current if corresponding to the low frequency component) read through the analog / digital converter ADC 65 with ifa1. (130), and then check the frequency If the frequency detected through the output unit 66 corresponds to f2 Hz, a flow 150 is performed in which the value read through the analog / digital converter ADC 65 (leakage current if corresponding to the low frequency component) is replaced with ifa2. In addition, when the frequency detected by the frequency detector 66 is not f1 Hz or f2 Hz, that is, the time t1 at which the f1 and f2 signals that do not overlap the low frequency overlapping signals of the low frequency overlapping device 40 as shown in FIG. t3), the process returns to the low frequency detection flow 110. When the frequency f1 Hz is detected, the CPU 71 inputs the f1 Hz low frequency superimposed signal through the analog / digital converter ADC 65. When the leakage current (ifa1) corresponding to the leakage current leaked to the ground is detected, and a frequency of f2 Hz is detected, the CPU 71 mounts the ground at the time of f2 Hz low frequency overlap inputted through the analog / digital converter ADC 65. Both leakage currents (ifa2) corresponding to leakage currents Upon detection of the two, the CPU 71 executes a calculation flow 160 to remove the capacitance component corresponding to the reactive component and to calculate only the insulation resistance component corresponding to the active component through the following time-based process. A display & output flow 170 is displayed to display and output the leakage current value (including the alarm output and the remote communication output).

Next, the calculation flow 160 will be described in detail.

 The symbols used in the following calculations are as follows.

    f0: Commercial AC voltage frequency (60Hz or 50Hz)

    f1: f1 Hz low frequency which is superimposed on the converter (4) through the second earth ground (2)

    f2: f2 Hz low frequency which is superimposed on the converter (4) through the second earth ground (2)

    if0: ground-to-ground leakage current corresponding to the common frequency (f0) detected by the image transformer (9 or 11)

    if1: Ground-to-ground leakage current corresponding to the low frequency of f1 Hz detected by the image transformer (9 or 11)

    if2: Ground-to-earth leakage current corresponding to the low frequency of f2 Hz detected by the image transformer (9 or 11)

    a: Total amplification factor of the current / voltage converter 61 and the amplifiers 62 and 64 used in the leakage current measurement unit.

    E0: Phase voltage of commercial AC frequency (60Hz or 50Hz)

    E1: Low frequency (f1) signal voltage which is superimposed on the converter 4 through the 2 type ground line (2)

    E2: Low frequency (f2) signal voltage which is superimposed on the converter 4 through the 2 type ground line (2)

    R: Parallel composite insulation resistance between phase and ground of converter 4 and load 5

    C: Parallel composite capacitance between phase and ground of converter 4 and load 5

    The leakage current value of the low frequency component lower than the commercial alternating frequency is filtered by filtering the commercial alternating frequency component at the f1 Hz low frequency overlapping output from the analog / digital converter 65 in the insulation monitoring device 60 and input to the CPU 71 ( ifa1) and f2 Hz low frequency superimposition filter the commercial AC frequency component and the leakage current value (ifa2) of the low frequency component lower than the commercial AC frequency is as follows.

      In order to eliminate the effect of C corresponding to the reactive component (imaginary part),

을 좌우항에 곱하면

Multiply by the left and right terms

     Subtracting equation (2) from equation (4)

   When the insulation resistance R is obtained from equation (5), it is as follows.

식을 사용하여 절연저항치를 저항성분에 의한 유효 누설전류값 또는 저주파수(f1, f2)의 신호전압에 대한 유효누설전류

으로 계산할 수 있다. 그리고 절연저항R이 계산되면 상기의 계산식에 절연저항R을 대입하면 정전용량C성분도 계산할 수 있을 것이다. 반대로 식(2)과 식(2)에 상수를 곱하여 절연저항R성분을 소거시키고 정전용량C성분을 구한 후, 다시 절연저항R을 계산하는 방법을 사용할 수 도 있을 것이다.The function related to insulation resistance R in Equation (6) shows that it can be calculated irrespective of capacitance C. In addition, the insulation resistance R value calculated above is applied to the phase voltage of commercial AC (60Hz or 50Hz). Effective leakage current

Using the formula, the insulation resistance value is the effective leakage current due to the resistance component or the effective leakage current with respect to the signal voltage at low frequencies (f1, f2).

Can be calculated as When the insulation resistance R is calculated, the capacitance C component may be calculated by substituting the insulation resistance R in the above formula. Conversely, by multiplying Equation (2) and Equation (2) by a constant, the insulation resistance R component may be erased, the capacitance C component may be obtained, and the insulation resistance R may be calculated again.

 In addition, if the magnitudes of the low frequency signal voltages E1 and E2 are the same as in Equation (6), the calculation may be simplified as in the following equation.

Next, the second embodiment of the present invention is a conceptual diagram of an insulation monitoring apparatus, Fig. 6, which is an internal detailed description of the insulation monitoring apparatus, and Fig. 12, which is an operation explanatory diagram of the low frequency superposition apparatus, and a diagram of main flow used in the control apparatus. It consists of 13. The difference from the first embodiment is that the constant value of the function required for the calculation, such as E1, E2, f1, f2, which is calculated on the insulation resistance value R or the effective leakage current value as described above, is converted to an electronic component such as a setting switch in the first embodiment. Compared with setting in the setting section 47, in the second embodiment, a device such as a device address number in the case where the key input section 77 is used as an electronic component such as a key pad and a plurality of insulation monitoring devices 50 are used. The value required for the operation is input using the key input unit 77, and the alarm is output to the outside through the alarm output unit 78 when the effective leakage current value is calculated to be less than or equal to a predetermined value. Alarm can be output, and if you want to monitor remotely, you can configure the function to use various types of communication methods (RS-232, RS-485, CDMA, power line communication) through the communication unit 79.Also, an embodiment in which the function of the communication unit 79 is removed may be additionally configured. The low frequency leakage current value detection, calculation, low frequency signal overlapping method and the like are the same as in the first embodiment.

Next, the third embodiment of the present invention is a conceptual diagram of an insulation monitoring apparatus, FIG. 7, which is an internal detailed explanation diagram of the insulation monitoring apparatus, and FIG. 12, which is an operation explanatory diagram of a low frequency superposition apparatus. It consists of 13. The difference from the first embodiment is that in FIG. 4, in which the connection position of the frequency detector 66 for determining or detecting whether the low frequency signal superimposed on the low voltage converter 4 is f1 Hz or f2 Hz is detected. Although connected between the amplifier 64 and the analog / digital converter 65, the low frequency is detected from the component value corresponding to the leakage current input from the analog / digital converter 65. However, in FIG. The low frequency is detected from the component value corresponding to the leakage current input from the amplifier 64 by being connected between the filter 63 and the amplifier 64, and the rest are the same as in the first embodiment.

Next, the fourth embodiment is a schematic diagram of an insulation monitoring apparatus, FIG. 8, which is an internal detailed explanation diagram of the insulation monitoring apparatus, and FIG. 12, which is an operation diagram of the low frequency superposition apparatus, and a diagram of main flow used in the control apparatus. It consists of 13. 5 differs from the second embodiment in that FIG. 5 is a connection position of the frequency detector 66 for determining or detecting whether the low frequency signal superimposed on the low voltage converter 4 is f1 Hz or f2 Hz. Although connected between the amplifier 64 and the analog / digital converter 65, the low frequency is detected from the component value corresponding to the leakage current input from the analog / digital converter 65. However, in FIG. The low frequency is detected from a component value that is connected between the filter 63 and the amplifier 64 and corresponds to the leakage current input from the amplifier 64, and the rest of them are the same as in the second embodiment.

9, 10 and 11 show the leakage current measuring unit 60 inside the insulation monitoring device 50 of FIGS. 4 to 8 used in the first to fourth embodiments. In another embodiment, in order to more easily design and manufacture the leakage current measuring unit 60, the amplifier 64 is removed from the leakage current measuring unit 60 of the first and second embodiments. Another embodiment, another embodiment as shown in FIG. 10 with the amplifier 62 removed, and FIG. 11 with the amplifier 62 removed from the leakage current measurement unit 60 in the third and fourth embodiments described above. In yet another embodiment, these three further embodiments comprise only one amplifier.

And although the current / voltage conversion unit 61 is composed of the internal structure of the insulation monitoring device 50, the whole or part of the portion having the function of the current / voltage conversion unit 61, the portion of the insulation monitoring device 50 There may also be embodiments configured externally.

Although the invention made by the present inventors has been described in detail according to the above embodiments, it is illustrative of the preferred embodiments of the present invention, and the present invention is not limited to the present invention and various modifications can be made without departing from the gist of the present invention. Of course.

1 is a diagram illustrating a conventional insulation resistance measuring apparatus in a live state

2 is an explanatory view of an insulation resistance measuring apparatus in a live state according to the present applicant

Figure 3 is an internal detailed explanatory view of the insulation monitoring device in the live state according to the present inventors

4 is a conceptual diagram illustrating the insulation monitoring device in the live state of the present invention;

Figure 5 is a detailed internal view of Embodiment 1 of the insulation monitoring apparatus in the live state of the present invention;

Figure 6 is a detailed internal view of the second embodiment of the insulation monitoring device in the live state of the present invention;

Figure 7 is a detailed internal view of Embodiment 3 of the insulation monitoring apparatus in the live state of the invention;

8 is an internal detailed view of Embodiment 4 of an insulation monitoring apparatus in a live state of the invention;

9 is another embodiment 1 of the leakage current measuring unit of the present invention

10 is another embodiment 2 of the leakage current measuring unit of the present invention

11 is another embodiment 3 of the leakage current measuring unit of the present invention

12 is an operation explanatory diagram of a low frequency overlapping apparatus used in the present invention

Figure 13 is the main flow used in the control device used in the present invention

14 is a conceptual diagram illustrating an insulation monitoring apparatus according to another embodiment in the live state of the present invention;

<Explanation of symbols for the main parts of the drawings>

1: high / low voltage conversion transformer 2: Class 2 ground wire

3: switchgear 4: converter (rail)

5: Load equipment 6: Class 2 grounding

7: Superposition Transformer 8: Low Frequency Superposition

9: Current transformer (ZCT) 10: Insulation monitoring device

11: ZCT 12: Class 3 Ground

13: Low frequency superposition device 14: Insulation monitoring device

15: reference voltage input line 20: leakage current measuring unit

21: current / voltage conversion unit 22: amplifier

23a: band pass filter (for f1) 23b: band pass filter (for f2)

24a: amplifier (for f1) 24b: amplifier (for f2)

25a: analog / digital converter (for f1) 25b: analog / digital converter (for f2)

30: controller

31: CPU 32: ROM

33: RAM 34: I / O

35: display unit 36: voltage, frequency setting unit

37: Key input 38: Alarm output

39: communication unit 40: low frequency overlapping device

50: insulation monitoring device 60: leakage current measuring unit

61: current / voltage converter 62: amplifier

63: filter 64: amplifier

65: analog / digital converter 66: frequency detector

70: controller

71: CPU (Operation Control Unit) 72: ROM

73: RAM 74: I / O

75: display unit 76: DATA setting unit

77: Key Input 78: Alarm Output

79: communication

Claims (2)

In order to monitor the insulation of the low voltage transformer through the neutral point of the low voltage side transformer or the ground wire connected to one ground, the low voltage signal flows between the low voltage circuit and the ground by the low frequency signal by superimposing the common AC frequency and other low frequency signal voltage. In the insulation monitoring device for detecting the current with an image current transformer, and detecting and monitoring the leakage current or insulation resistance component of the resistance component directly related to the pure insulation insulation (leakage) between the phase and the ground from the detected leakage current, Two types of low frequency signal voltages (f1 Hz, f2 Hz) do not overlap at the same time to detect and monitor the effective leakage current or insulation resistance component of the resistance component directly related to the pure insulation reduction (leakage) between the low voltage circuit and the ground. A low frequency overlapping device having a function of being able to overlap each of the low voltage converters individually without; An image current transformer for detecting a leakage current flowing between the low voltage converter and the ground by the low frequency signal voltage superimposed on the low voltage converter by the low frequency overlapping device; A current / voltage converter for converting the leakage current detected by the image current transformer into a voltage signal; An amplifier for amplifying a microcurrent value or a voltage value corresponding to the leakage current converted by the current / voltage converter; A filter for removing components of a commercial alternating frequency from the leakage current signal amplified by the amplifier; A frequency detector for judging whether the frequency of the low frequency signal superimposed on the low voltage converter by the low frequency superposition device from the leakage current component extracted from the filter is f1 Hz or f2 Hz; An analog / digital converter for converting an analog signal output from the amplifier or filter into a digital signal; Low voltage, characterized in that it comprises a control device for reading and calculating and controlling the data of the analog-digital converter and the frequency detector and various data, and calculates the insulation resistance value or the effective leakage current value by the following formula: Live insulation monitoring device of converter

 (E0: phase voltage of commercial AC, E1: f1 low frequency signal voltage, f1: low frequency (f1 Hz), f2: low frequency (f2 Hz), E2: f2 low frequency signal voltage, a: leakage current measurement circuit) Amplification factor, ifa1: final leakage current value corresponding to f1 low frequency component, ifa2: final leakage current value corresponding to f2 low frequency component) For commercial AC voltage

Or for low frequency signal voltage

In order to monitor the insulation of the low voltage transformer through the neutral point of the low voltage side transformer or the ground wire connected to one ground, the low voltage signal flows between the low voltage circuit and the ground by the low frequency signal by superimposing the common AC frequency and other low frequency signal voltage. In the insulation monitoring device for detecting the current with an image current transformer, and detecting and monitoring the leakage current or insulation resistance component of the resistance component directly related to the pure insulation insulation (leakage) between the phase and the ground from the detected leakage current, Two types of low frequency signal voltages (f1 Hz, f2 Hz) do not overlap at the same time to detect and monitor the effective leakage current or insulation resistance component of the resistance component directly related to the pure insulation reduction (leakage) between the low voltage circuit and the ground. A low frequency overlapping device having a function of being able to overlap each of the low voltage converters individually without; An image current transformer for detecting a leakage current flowing between the low voltage converter and the ground by the low frequency signal voltage superimposed on the low voltage converter by the low frequency overlapping device; A current / voltage converter for converting the leakage current detected by the image current transformer into a voltage signal; An amplifier for amplifying a microcurrent value or a voltage value corresponding to the leakage current converted by the current / voltage converter; A filter for removing components of a commercial alternating frequency from the leakage current signal amplified by the amplifier; A frequency detector for judging whether the frequency of the low frequency signal superimposed on the low voltage converter by the low frequency superposition device from the leakage current component extracted from the filter is f1 Hz or f2 Hz; An analog / digital converter for converting an analog signal output from the amplifier or filter into a digital signal, and a control device for reading and controlling data and various data of the analog / digital converter and the frequency detector; Live insulation monitoring device of a low-voltage converter characterized in that it comprises a

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