JP2008224392A - Insulation monitor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To restrain an ineffective component of a measuring signal flowing a class B grounding line to monitor an insulating state of a low-voltage side cable way of a transformer. <P>SOLUTION: This insulation monitor is provided with a monitoring signal generation circuit 20 for injecting a monitoring signal of a frequency different from a commercial frequency, into the class B grounding line of the transformer, a phase regulation circuit 40 for extracting a reference signal corresponding to the monitoring signal from a class D grounding reference input taken in from the class B grounding line, and for timing-matching a phase of the reference signal with a phase of a ground electrostatic capacitance in the low-voltage side cable way of the transformer, a detecting means 50 for detecting a current flowing in the class B grounding line, a measuring signal detecting circuit 60 for removing an unnecessary component from a detection output from the detecting means and for generating a measured signal, a restraining signal generating circuit 80 for generating a restraining signal to offset the ground electrostatic capacitance included in the measured signal, based on the reference signal, to be supplied to a restraining part of the detecting means, and a computation processing part 90 for finding a ground insulation resistance of the low-voltage side cable way of the transformer, from the measured signal based on the detection signal of the detecting means with the offset ground electrostatic capacitance. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an insulation monitoring device for monitoring a ground insulation resistance of a low voltage side electric circuit of a transformer in a live line state.

  Generally, high-voltage power transmitted by a transmission / distribution line is supplied to a load (for example, a factory or a general household) at a low voltage by a power receiving transformer. In such a case, it is extremely important to quickly detect a leakage in the electric circuit connecting the power receiving transformer and the load to prevent a leakage accident or the like.

  For this reason, conventionally, an insulation monitoring device is provided in the power receiving transformer as described above. An example of this type of conventional insulation monitoring apparatus is shown in FIG.

  As shown in FIG. 4, the conventional insulation monitoring apparatus includes a frequency divider 210, an amplifier circuit 211, an injection transformer 212, a zero-phase transformer 213, an amplifier circuit 214, a filter 215, an A / A A D converter 216, a CPU 217, a D / A converter 218, a multiplier 219, an adder 220, a resistor R, and a capacitor C are included.

  In FIG. 4, a B-type ground line 223 is connected between the first electric circuit 222 on the output side of the power receiving transformer 221 and the ground. A load 225 is connected to the first electric circuit 222 and the second electric circuit 224 on the output side of the power receiving transformer 221.

  The frequency divider 210 generates a low frequency signal having a frequency different from the commercial frequency. The amplifier circuit 211 amplifies the low frequency signal generated by the frequency divider 210.

  The primary winding 212a of the injection transformer 212 injects the low-frequency signal amplified by the amplifier circuit 211 into the B-type ground line 223 as an insulation monitoring signal. As a result, the insulation monitoring signal is superimposed on the leakage current that flows back through the second electric path 224, the ground, the B-type ground line 223, and the first electric path 222.

  The zero phase transformer 213 detects a leakage current based on the insulation monitoring signal. The amplifier circuit 214 amplifies the leakage current detected by the zero phase transformer 213. The filter 215 extracts the insulation monitoring signal from the leakage current amplified by the amplifier circuit 214. The A / D converter 216 converts the insulation monitoring signal extracted by the filter 215 into a digital signal.

  The CPU 217 detects the insulation monitoring signal extracted by the filter 215 at the timing of the phase 0 °, the phase 180 °, the phase 90 °, and the phase 270 ° of the insulation monitoring signal injected into the B-type ground line 223, and the active component And the output of the D / A converter 218a is controlled so that both of the ineffective components become zero.

  The D / A converter 218a converts an insulation resistance equivalent component of the insulation monitoring signal detected by the CPU 217 into an analog signal. Further, the D / A converter 218b converts the component equivalent to the stray capacitance of the insulation monitoring signal detected by the CPU 217 into an analog signal.

  The multiplier 219a multiplies the reference voltage detected by the tertiary winding 212b of the injection transformer 212 to the insulation resistance equivalent component of the insulation monitoring signal converted into an analog signal by the D / A converter 218a. Process. Further, the multiplier 219b detects the reference voltage detected by the tertiary winding 212b of the injecting transformer 212 with respect to the stray capacitance equivalent component of the insulation monitoring signal converted into an analog signal by the D / A converter 218b. Is multiplied.

  The adder 220 adds an insulation resistance equivalent component of the insulation monitoring signal converted into a resistance current by the resistor R and a stray capacitance equivalent component of the insulation monitoring signal converted into a capacitive current by the capacitor C. The current added by the adder 220 is supplied to the tertiary side of the zero-phase transformer 213 as a suppression signal current.

  When the suppression signal current is supplied to the zero-phase transformer 213 in this way, the insulation resistance component (ground insulation) of the insulation monitoring signal injected into the B-type ground line 223 is canceled by magnetic flux in the zero-phase transformer 213. The component based on the resistance R0) and the stray capacitance component (the component based on the ground capacitance C0) are suppressed. Then, the CPU 217 detects the amount of suppression required to set the insulation resistance equivalent component to zero as the ground insulation resistance R0.

As described above, in the conventional technique, the insulation resistance component (component based on the ground insulation resistance R0) and the stray capacitance component (component based on the ground capacitance C0) of the insulation monitoring signal injected into the B-type ground line 223. A suppression signal for suppressing the above is generated and the ground insulation resistance R0 is monitored.
JP 2005-181148 A

  By the way, in the insulation monitoring apparatus as described above, if only the effective component (component based on the ground insulation resistance R0) of the insulation monitor signal injected into the B-type ground line 223 can be extracted, the ground insulation resistance R0 (or the ground insulation resistance) Current flowing in R0) can be accurately obtained. Therefore, it is only necessary to suppress only the ineffective part of the insulation monitoring signal (component based on the ground capacitance C0).

  However, in the technology at the time when the above-mentioned Patent Document 1 was proposed, the suppression signal for the ineffective portion of the insulation monitoring signal was generated by the capacitor, so that an accurate suppression signal could not be generated, and the ground insulation resistance R0 It was difficult to monitor accurately.

  As described above, there has been a demand for a technique for easily and reliably stably suppressing only the ineffective portion of the insulation monitoring signal.

  The present invention has been made to solve the above-described problems, and is an insulation monitor injected into the class B ground line of the transformer in order to monitor the insulation state of the electric circuit connected to the output side of the transformer. An object of the present invention is to provide an insulation monitoring device capable of easily and reliably suppressing an invalid signal.

  According to a first aspect of the present invention, there is provided a monitoring signal generating circuit for injecting a monitoring signal having a frequency different from a commercial frequency into a B-type grounding line of a transformer, and a D-type grounding reference fetched from the B-type grounding line. A reference signal corresponding to the monitoring signal is extracted from the input, and based on a predetermined clock frequency, the phase timing of the reference signal is matched with the phase timing of the ground capacitance of the low-voltage side circuit of the transformer A phase adjustment circuit; detection means for detecting a current flowing in the B-type ground line; and a measurement signal detection circuit for detecting a measurement signal by removing unnecessary components such as a commercial frequency and its harmonics from the detection output of the detection means And generating a suppression signal for canceling the ground capacitance included in the measurement signal based on the reference signal output from the phase adjustment circuit. A suppression signal generation circuit for supplying a signal to the suppression unit of the detection means, and a low voltage of the transformer from the measurement signal based on the detection output of the detection means in which the ground capacitance is canceled by the supply of the suppression signal And an arithmetic processing circuit for obtaining a ground insulation resistance of the side electric circuit.

  The insulation monitoring device according to claim 2 of the present invention is the insulation monitoring device according to claim 1, wherein the ground insulation resistance included in the measurement signal and the ground insulation resistance are based on the reference signal output from the phase adjustment circuit. A synchronization signal generating circuit that generates a synchronization signal for separating the ground capacitance is further provided.

  The insulation monitoring device according to claim 3 of the present invention is the insulation monitoring device according to claim 2, wherein the arithmetic processing circuit is configured to provide the ground insulation resistance included in the measurement signal based on the measurement signal and the synchronization signal. And the ground capacitance are separated from each other.

  According to a fourth aspect of the present invention, there is provided the insulation monitoring apparatus according to the third aspect, wherein the arithmetic processing circuit is configured to suppress the suppression signal so that the ground capacitance separated from the ground insulation resistance becomes zero. The generation level is controlled in real time with respect to the suppression level of the suppression signal.

  The insulation monitoring apparatus according to claim 5 of the present invention is the insulation monitoring apparatus according to any one of claims 1 to 4, wherein the phase adjustment circuit is configured to input the predetermined clock input from the arithmetic processing circuit. The phase timing of the reference signal is adjusted based on the frequency.

  The insulation monitoring device according to claim 6 of the present invention is the insulation monitoring device according to any one of claims 1 to 5, wherein the detection means is electromagnetically coupled to the B-type ground wire, and the suppression signal is tertiary. It is supplied to the side.

  The insulation monitoring device according to claim 7 of the present invention is the insulation monitoring device according to any one of claims 1 to 6, wherein the monitoring signal generating circuit sends the monitoring signal to the B-type ground via an injection means. And a protective circuit for protecting the monitoring signal generation circuit from an abnormal current that is reversely injected from the B-type ground line via the injection means to the output stage. .

  According to an eighth aspect of the present invention, there is provided an insulation monitoring apparatus comprising: a monitoring signal generating circuit for injecting a monitoring signal having a frequency different from a commercial frequency into a B-type grounding line of a transformer; and a D-type grounding reference taken from the B-type grounding line. A phase in which a reference signal corresponding to the monitoring signal is extracted from the input, and the phase of the reference signal is matched with the phase opposite to the phase of the ground capacitance of the low-voltage side electric circuit of the transformer based on a predetermined clock frequency An adjustment circuit; detection means for detecting a current flowing in the B-type ground line; and a measurement signal detection circuit for detecting a measurement signal by removing unnecessary components such as a commercial frequency and its harmonics from the detection output of the detection means; Based on the reference signal output from the phase adjustment circuit, the ground isolation resistance and the ground capacitance are separated from the low-voltage side electric circuit of the transformer included in the measurement signal. Based on the reference signal output from the synchronization signal generation circuit that generates the signal and the phase adjustment circuit, a suppression signal for canceling the ground capacitance included in the measurement signal is generated, and the suppression signal is Based on the suppression signal generation circuit supplied to the suppression unit of the detection means, the measurement signal and the synchronization signal, the ground insulation resistance and the ground capacitance included in the measurement signal are separated, and the ground static Based on the detection output of the detection means in which the suppression level by the suppression signal is controlled in real time to the suppression signal generation circuit so that the capacitance becomes zero, and the ground capacitance is canceled by the supply of the suppression signal An arithmetic processing circuit for obtaining the ground insulation resistance from the measurement signal.

  The insulation monitoring device according to claim 9 of the present invention is the insulation monitoring device according to claim 8, wherein the phase adjustment circuit is configured to perform the reference based on the predetermined clock frequency input from the arithmetic processing circuit. The phase timing of the signal is adjusted.

  The insulation monitoring apparatus according to claim 10 of the present invention is the insulation monitoring apparatus according to claim 9, wherein the detection means is electromagnetically coupled to the B-type ground line, and the suppression signal is supplied to the tertiary side. Features.

  An insulation monitoring device according to an eleventh aspect of the present invention is the insulation monitoring device according to any one of the eighth to tenth aspects, wherein the monitoring signal generating circuit sends the monitoring signal to the B-type ground via an injection means. And a protective circuit for protecting the monitoring signal generation circuit from an abnormal current that is reversely injected from the B-type ground line via the injection means to the output stage. .

  As described above, according to the present invention, a monitoring signal generating circuit for injecting a monitoring signal having a frequency different from the commercial frequency to the B-type ground line of the transformer, and the monitoring signal from the D-type ground reference input taken from the B-type ground line. And a phase adjustment circuit that matches the phase timing of the reference signal to the phase timing of the ground capacitance of the low-voltage side electric circuit of the transformer, based on a predetermined clock frequency, A detecting means for detecting a current flowing in the B-type ground line, a measurement signal generating circuit for generating a measurement signal by removing unnecessary components such as a commercial frequency and its harmonics from the detection output of the detecting means, and the phase adjustment Based on the reference signal output from the circuit, a suppression signal for canceling the ground capacitance included in the measurement signal is generated, and the suppression signal is detected by the detection means. A suppression signal generation circuit for supplying to the detection unit of the transformer, and ground insulation of the low-voltage side electric circuit of the transformer from the measurement signal based on the detection output of the detection means in which the ground capacitance is canceled by the supply of the suppression signal In order to monitor the insulation state of the electric circuit connected to the output side of the transformer, the insulation monitoring signal injected into the class B ground line of the transformer is provided. The ineffective portion can be easily and reliably suppressed.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of an insulation monitoring device according to the present invention. This insulation monitoring device 10 is a combination of a ground insulation resistance R0 and a ground capacitance (floating capacitance) C0 and a ground impedance Z0. It is provided in the B class grounding wire 4 of the low voltage | pressure side of the receiving transformer 1 which has these.

  A load 2 is connected to the output side (low voltage side) of the power receiving transformer 1. Further, the first electric circuit 3 on the low voltage side of the power receiving transformer 1 is grounded via a B-type grounding wire 4. In addition, a leakage current based on the ground impedance Z0 is circulated in the path formed by the second electric circuit 5 on the low voltage side of the power receiving transformer 1, the ground, the B-type grounding wire 4, and the first electric circuit 3.

  The insulation monitoring apparatus 10 includes a monitoring signal generation circuit 20 that injects a monitoring signal W having a frequency different from the commercial frequency into the B-type ground line 4 of the transformer 1 through a superimposing transformer (CT) 30 as an injection unit. ing.

  The monitor signal generation circuit 20 includes an oscillator (OSC) 21 that generates a signal to be superimposed on the electric circuit, and a power amplifier 22 that amplifies the signal generated by the oscillator (OSC) 21 so that the superimposed transformer (CT) 30 can be driven. And. The oscillator (OSC) 21 generates a signal having a required frequency (for example, 20 Hz) by dividing a clock signal generated based on a crystal oscillator (not shown) attached to an arithmetic processing circuit (MPU) 90 described later. Is.

  The monitoring signal generation circuit 20 also prevents the power amplifier 22 from being damaged by the energy flowing backward through the superposed transformer (CT) 30 when a large current flows through the B-type grounding wire 4 due to a ground fault of the equipment or the like. A protection circuit 23 for protection is provided. A specific configuration of the protection circuit 23 will be described later.

  Further, the insulation monitoring apparatus 10 extracts the reference signal B corresponding to the monitoring signal W from the D-type grounding reference input taken from the B-type grounding wire 4, and based on the predetermined clock frequency, A phase adjustment circuit 40 for adjusting the phase timing to the phase timing of the ground capacitance of the low-voltage side electric circuit 5 of the transformer 1 is provided.

  The phase adjustment circuit 40 includes an alias filter 41 and a switched capacitor filter (SCF) 42. The alias filter 41 removes in advance a frequency component that causes a malfunction in the next-stage switched capacitor filter (SCF) 42 from the D-type ground reference input taken in from the B-type ground line 4.

  The switched capacitor filter (SCF) 42 has a function as a low-pass filter and a function as a phase shifter that adjusts the phase of a signal based on a predetermined clock frequency. That is, the switched capacitor filter (SCF) 42 has an attenuation characteristic that functions as a low-pass filter, as shown in FIG. The switched capacitor filter (SCF) 42 has a clock frequency-phase characteristic that functions as a phase shifter, as shown in FIG.

  With the low-pass filter function, the switched capacitor filter (SCF) 42 removes unnecessary components such as the commercial frequency and its harmonics from the D-type ground reference input taken in from the B-type ground line 4, and the monitoring signal W Can be extracted.

  At the same time, the switched capacitor filter (SCF) 42 can adjust the phase timing of the reference signal B to the phase timing of the ground capacitance of the low-voltage side circuit 5 of the transformer 1 by the phase shifter function. it can. That is, by matching the phase of the reference signal B with the phase opposite to the phase of the ground capacitance of the low voltage side electric circuit 5 of the transformer 1, an accurate phase for canceling the ground capacitance can be generated.

  The switched capacitor filter (SCF) 42 adjusts the phase of the signal based on a predetermined clock frequency, and the clock frequency is commanded from an arithmetic processing circuit (MPU) 90 described later. Therefore, the clock frequency set (adjusted) by the manufacturer at the time of product shipment does not change due to subsequent temperature change or aging change.

  In other words, the phase adjustment by the switched capacitor filter (SCF) 42 is extremely accurate by finely adjusting the clock frequency generated based on a crystal oscillator that is highly stable with respect to temperature change and aging change. In addition, it can be realized with high stability. Compared with the phase alignment accuracy that can be realized by the conventional analog phase shifter, the phase alignment accuracy by the digital switched capacitor filter (SCF) 42 is literally different.

  Further, the insulation monitoring device 10 includes a zero-phase current transformer (ZCT) 50 as detection means for detecting a current flowing through the B-type grounding wire 4.

  The insulation monitoring device 10 also includes a measurement signal detection circuit 60 that detects the measurement signal M by removing unnecessary components such as commercial frequencies and harmonics from the detection output of the zero-phase current transformer (ZCT) 50. .

  The measurement signal detection circuit 60 includes a head amplifier 61, a filter 62, and a level converter 63. The head amplifier 61 converts the current detected by the zero-phase current transformer (ZCT) 50 into a voltage and amplifies it to a required level in the next stage. The filter 62 removes unnecessary components other than the measurement signal M such as the commercial frequency and its harmonics from the output of the head amplifier 61 and amplifies the measurement signal M. The level converter 63 converts the output of the filter 62, that is, the level of the analog signal into a level that can be digitally processed by an arithmetic processing circuit (MPU) 90 described later.

  Further, the insulation monitoring device 10 separates the ground insulation resistance and the ground capacitance of the low-voltage side electric circuit 5 of the transformer 1 included in the measurement signal M based on the reference signal B output from the phase adjustment circuit 40. A synchronization signal generation circuit 70 for generating a synchronization signal S for the purpose is provided.

  The synchronization signal generation circuit 70 serves as a synchronization signal S for separating an effective component (ground insulation resistance) and an ineffective component (ground capacitance) in an arithmetic processing circuit (MPU) 90 to be described later. The reference signal B output from the circuit 40 is converted into a square wave by zero crossing, and the obtained synchronization signal S is supplied to an arithmetic processing circuit (MPU) 90 described later.

  The insulation monitoring device 10 generates a suppression signal P for canceling the ground capacitance included in the measurement signal M based on the reference signal B output from the phase adjustment circuit 40, and sets the suppression signal P to zero. A suppression signal generation circuit 80 that supplies the suppression unit of the phase current transformer (ZCT) 50 is provided.

  The suppression signal generation circuit 80 is a circuit that controls the output level of an accurate cancellation signal generated by the switched capacitor filter (SCF) 42 of the phase adjustment circuit 40, and is a zero-phase current transformer (ZCT) 50. It is continuously controlled in real time by an arithmetic processing circuit (MPU) 90 to be described later so that the current (ineffective component current) which is a component of the ground capacitance becomes zero in terms of magnetic flux. Such a suppression signal generation circuit 80 is configured by, for example, a multiplier.

  Furthermore, the insulation monitoring apparatus 10 includes an arithmetic processing circuit (MPU) 90. The arithmetic processing circuit (MPU) 90 instructs the switched capacitor filter (SCF) 42 of the phase adjustment circuit 40 to use a reference clock frequency for adjusting the phase of the signal. This clock frequency is set (adjusted) by the manufacturer at the time of product shipment, and does not change due to subsequent temperature change or aging change.

  The arithmetic processing circuit (MPU) 90 is also extracted from the detection output of the zero-phase current transformer (ZCT) 50 by the filter 62 via the head amplifier 61 and input from the level converter 63 and the phase adjustment. Based on the reference signal B output from the circuit 40 and the synchronization signal S input from the synchronization signal generation circuit 70, the ground insulation resistance and the ground electrostatic resistance of the low-voltage side electric circuit 5 of the transformer 1 included in the measurement signal M It separates the capacity.

  Then, the arithmetic processing circuit (MPU) 90 separates the ground insulation resistance and the ground capacitance included in the measurement signal M, and then sends the suppression signal generation circuit 80 so that the ground capacitance becomes zero. Thus, the suppression level by the suppression signal P is controlled in real time.

  The suppression signal P supplied from the suppression signal generation circuit 80 to the suppression unit of the zero-phase current transformer (ZCT) 50, that is, the zero-phase change, by real-time control by the arithmetic processing circuit (MPU) 90 for the suppression signal generation circuit 80. The suppression current P supplied to the tertiary side of the flow device (ZCT) 50 is accurately controlled so that the ground capacitance becomes zero.

  As a result, the detection output of the zero-phase current transformer (ZCT) 50 is the one in which the ground capacitance has been canceled, and the arithmetic processing circuit (MPU) 90 has the measurement signal (the ground capacitance is canceled out) based on this detection output. The ground insulation resistance is obtained from the measured signal) M.

  In addition, the arithmetic processing circuit (MPU) 90 controls the functions of the display unit 101 and the operation unit 102 and controls the alarm output 103 and the like.

  Here, the configuration of the protection circuit 23 will be described with reference to FIG. FIG. 3 is a block diagram showing an example of a schematic configuration of the protection circuit 23.

  In FIG. 3, the protection circuit 23 includes a triac 24, a current detection circuit 25, a voltage detection circuit 26, a relay 27, and a fuse 28.

  When the leakage current flowing through the B-type grounding wire 4 increases due to the grounding of the second electric circuit 5 on the output side of the transformer 1 (when a grounding current is generated), this leakage current is used. Electric power is injected into the insulation monitoring apparatus 10 from the B-type ground line 4 via the superposed transformer (CT) 30. The protection circuit 23 is for protecting the power amplifier 22 and the oscillator (OSC) 21 in such a case. A specific example of the operation will be described below.

  First, when a voltage generated due to a ground fault is detected, the drive unit 27a of the relay 27 opens the switch unit 27b. Thereby, the power amplifier 22 and the superposed transformer (CT) 30 are electrically disconnected, and a large current is prevented from flowing into the power amplifier 22.

  Next, when the opening operation of the relay 27 in which the electric power based on the leakage current at the time of a ground fault or the like is injected from the B-type ground line 4 into the protection circuit 23 via the superposed transformer (CT) 30 is not in time, the protection circuit 23 When the current flowing into (the voltage at the output terminal of the power amplifier 22) increases to a predetermined value, the triac 24 is closed.

  In this way, when the output terminal of the power amplifier 22 is short-circuited and a closed circuit is formed by the superposed transformer (CT) 30, the relay 27, and the triac 24, the voltage disappears. It is detected that a current has flowed, and the drive unit 27a of the relay 27 opens the switch unit 27b. As a result, the power amplifier 22 and the superposed transformer (CT) 30 are electrically disconnected. This prevents a large current from flowing into the power amplifier 22 regardless of whether the output terminal of the power amplifier 22 is short-circuited.

  When the relay 27 is opened, no current flows and current detection becomes impossible, but the voltage rises again, so that the relay 27 continues to open by voltage detection.

  In the case of a large current ground fault, the fuse is protected by blowing before the TRIAC burns out.

  After that, the ground fault in the second electric circuit 5 on the output side of the transformer 1 is recovered, and the voltage detection circuit indicates that the voltage generated between the windings of the superposed transformer (CT) 30 has become lower than a predetermined value. When 26 is detected, the drive part 27a of the relay 27 closes the switch part 27b. As a result, the power amplifier 22 and the superposed transformer (CT) 30 are electrically connected.

  The fuse 28 is connected to the power amplifier 22 and the superposed transformer (CT) when a current large enough to damage the triac 24 flows due to the electric power injected from the B-type ground line 4 through the superposed transformer (CT) 30. ) To electrically cut off 30. Therefore, the rating of the fuse 28 and the rating of the triac 24 are determined so that the triac 24 is prevented from being damaged.

  Next, the operation of the insulation monitoring apparatus 10 configured as described above will be described.

  First, the oscillator (OSC) 21 of the monitor signal generation circuit 20 generates a monitor signal W having a required frequency (for example, a sine wave of 20 Hz) different from the commercial frequency based on the clock signal of the arithmetic processing circuit (MPU) 90. Next, the power amplifier 22 amplifies the power of the monitoring signal W so that the superposed transformer (CT) 30 can be driven. Then, the monitoring signal W is injected into the B-type ground line 4 of the transformer 1 from the monitoring signal generation circuit 20 via the superposition transformer (CT) 30 as injection means via the protection circuit 23.

  Further, the alias filter 41 of the phase adjustment circuit 40 removes in advance a frequency component that causes a malfunction in the switched capacitor filter (SCF) 42 from the D-type ground reference input fetched from the B-type ground line 4. Next, the switched capacitor filter (SCF) 42 removes unnecessary components such as the commercial frequency and its harmonics from the output of the alias filter 41 by the low-pass filter function, and a reference signal corresponding to the monitoring signal W is obtained. B is extracted.

  At the same time, the switched capacitor filter (SCF) 42 synchronizes the phase timing of the reference signal B with the phase timing of the ground capacitance of the low-voltage side circuit 5 of the transformer 1 by the phase shifter function. That is, by matching the phase of the reference signal B with the phase opposite to the phase of the ground capacitance of the low voltage side electric circuit 5 of the transformer 1, an accurate phase for canceling the ground capacitance is generated.

  At this time, since the switched capacitor filter (SCF) 42 adjusts the phase of the signal based on a predetermined clock frequency commanded from the arithmetic processing circuit (MPU) 90, it is set by the manufacturer at the time of product shipment. The (adjusted) clock frequency does not change with subsequent temperature changes or aging.

  That is, by using the clock frequency generated and commanded from the arithmetic processing circuit (MPU) 90 based on a crystal oscillator that is highly stable with respect to temperature change and aging change, the switched capacitor filter (SCF) 42 The phase alignment is done very accurately.

  On the other hand, a zero-phase current transformer (ZCT) 50 as detection means detects the current flowing through the B-type ground wire 4. That is, the current flowing through the B-type ground line 4 is circulated through a path formed by the second electric circuit 5 on the low voltage side of the transformer 1, the ground, the B-type ground line 4, and the first electric circuit 3. The leakage current based on the ground impedance Z0 is included. Therefore, the detected current of the zero-phase current transformer (ZCT) 50 includes a leakage current based on the ground impedance Z0.

  Then, the head amplifier 61 of the measurement signal detection circuit 60 converts the current detected by the zero-phase current transformer (ZCT) 50 into a voltage and amplifies it to a required level in the next stage. Next, the filter 62 removes unnecessary components other than the measurement signal M such as the commercial frequency and its harmonics from the output of the head amplifier 61 and amplifies the measurement signal M. The level converter 63 converts the output of the filter 62, that is, the level of the analog signal into a level that can be digitally processed by the arithmetic processing circuit (MPU) 90. That is, the measurement signal detection circuit 60 generates the measurement signal M based on the zero-phase current transformer (ZCT) 50 detection current including the leakage current based on the ground impedance Z0 at the output of the level converter 63.

  Further, the synchronization signal generation circuit 70 is based on the reference signal B output from the phase adjustment circuit 40, and the ground impedance of the low voltage side electric circuit 5 of the transformer 1 included in the measurement signal M output from the measurement signal detection circuit 60. Z0, that is, a synchronization signal S for separating the ground insulation resistance R0 and the ground capacitance C0 is generated. That is, the synchronization signal generation circuit 70 converts the reference signal B output from the phase adjustment circuit 40 into a square wave by zero crossing, and supplies the obtained synchronization signal S to the arithmetic processing circuit (MPU) 90.

  In such a state, the arithmetic processing circuit (MPU) 90 is fetched from the measurement signal M obtained from the detection output of the zero-phase current transformer (ZCT) 50 via the measurement signal detection circuit 60 and the B-type ground line 4. The low-voltage side of the transformer 1 included in the measurement signal M based on the synchronization signal S input from the synchronization signal generation circuit 70 based on the reference signal B output from the D-type ground reference input via the phase adjustment circuit 40 The ground insulation resistance R0 and the ground capacitance C0 of the electric circuit 5 are separated.

  Then, after the arithmetic processing circuit (MPU) 90 separates the ground insulation resistance R0 and the ground capacitance C0 included in the measurement signal M, the suppression signal generation circuit so that the ground capacitance C0 becomes zero. 80, the suppression level by the suppression signal P is controlled in real time. That is, in the zero-phase current transformer (ZCT) 50, the arithmetic processing circuit (MPU) 90 controls the suppression signal generation circuit 80 so that the current (invalid component current) which is a component of the ground capacitance C0 becomes zero in terms of magnetic flux. Real-time control.

  The suppression signal generation circuit 80 generates a suppression signal P for canceling the ground capacitance included in the measurement signal M by real-time control by the arithmetic processing circuit (MPU) 90 for the suppression signal generation circuit 80. The suppression signal P is supplied as a suppression current P from the suppression signal generation circuit 80 to the tertiary side of the zero-phase current transformer (ZCT) 50, and the ground-capacitance C 0 is magnetically reflected in the zero-phase current transformer (ZCT) 50. To zero. As a result, the ground capacitance C0 in the zero-phase current transformer (ZCT) 50 becomes zero in terms of magnetic flux.

  As a result, the detection output of the zero-phase current transformer (ZCT) 50 becomes a value obtained by canceling the ground capacitance C0, and the arithmetic processing circuit (MPU) 90 detects the measurement signal (ground capacitance C0) based on this detection output. The ground insulation resistance R0 is obtained from the measurement signal M).

  In the above embodiment, the switched capacitor filter (SCF) 42 has the phase shifter function to change the phase of the reference signal B to a phase opposite to the phase of the ground capacitance of the low-voltage side circuit 5 of the transformer 1. By combining, it is configured to generate an accurate phase for canceling the ground capacitance, but is not limited to this. That is, for example, the phase of the reference signal B can be matched with the phase of the ground capacitance of the low voltage side electric circuit 5 of the transformer 1. Again, the exact phase required to cancel the ground capacitance can be generated.

  In this case, an appropriate phase inversion circuit is provided in the subsequent stage of the switched capacitor filter (SCF) 42 of the phase adjustment circuit or in the previous stage of the suppression signal generation circuit 80, so that in addition to the phase alignment, the reference The phase of the signal B can be matched with the phase opposite to the phase of the ground capacitance of the low voltage side electric circuit 5 of the transformer 1.

It is a block diagram which shows one Embodiment of the insulation monitoring apparatus by this invention. It is a graph which shows an example of the characteristic of the switched capacitor filter (SCF) of a phase adjustment circuit. It is a block diagram which shows an example of a protection circuit. It is a block diagram which shows an example of the conventional insulation monitoring apparatus.

Explanation of symbols

1 Transformer (Receiving transformer)
2 Load 3 First Electric Circuit 4 Type B Grounding Line 5 Second Electric Circuit 10 Insulation Monitoring Device 20 Monitoring Signal Generation Circuit 21 Oscillator (OSC)
22 Power amplifier 23 Protection circuit 30 Injection means (superposition transformer; CT)
40 Phase adjustment circuit 41 Alias filter 42 Switched capacitor filter (SCF)
50 Detection means (Zero phase current transformer; ZCT)
60 measurement signal detection circuit 61 head amplifier 62 filter 63 level converter 70 synchronization signal generation circuit 80 suppression signal generation circuit 90 arithmetic processing circuit (MPU)

Claims (11)

A monitoring signal generating circuit for injecting a monitoring signal having a frequency different from the commercial frequency into the B-type ground line of the transformer;
A reference signal corresponding to the monitoring signal is extracted from a D-type ground reference input taken from the B-type ground line, and the phase timing of the reference signal is determined based on a predetermined clock frequency on the low-voltage side of the transformer. A phase adjustment circuit that matches the phase timing of the electrostatic capacitance of the circuit,
Detecting means for detecting a current flowing in the B-type ground line;
A measurement signal detection circuit for detecting a measurement signal by removing unnecessary components such as a commercial frequency and its harmonics from the detection output of the detection means;
Suppression that generates a suppression signal for canceling out the ground capacitance included in the measurement signal based on the reference signal output from the phase adjustment circuit and supplies the suppression signal to the suppression unit of the detection means A signal generation circuit;
An arithmetic processing circuit for obtaining a ground insulation resistance of a low-voltage side electric circuit of the transformer from the measurement signal based on a detection output of the detection unit in which the ground capacitance is canceled by the supply of the suppression signal;
An insulation monitoring device comprising:   A synchronization signal generating circuit for generating a synchronization signal for separating the ground insulation resistance and the ground capacitance included in the measurement signal based on the reference signal output from the phase adjustment circuit; The insulation monitoring apparatus according to claim 1.   3. The insulation monitoring apparatus according to claim 2, wherein the arithmetic processing circuit separates the ground insulation resistance and the ground capacitance included in the measurement signal based on the measurement signal and the synchronization signal. .   4. The arithmetic processing circuit performs real-time control of a suppression level by the suppression signal to the suppression signal generation circuit so that the ground capacitance separated from the ground insulation resistance becomes zero. The insulation monitoring device described.   5. The phase adjustment circuit adjusts the phase timing of the reference signal based on the predetermined clock frequency input from the arithmetic processing circuit. 6. The insulation monitoring device described.   The insulation monitoring apparatus according to claim 1, wherein the detection unit is electromagnetically coupled to the B-type ground line, and the suppression signal is supplied to a tertiary side.   The monitoring signal generating circuit injects the monitoring signal into the B-type ground line via an injection unit, and an abnormality that is reversely injected into the output stage from the B-type ground line through the injection unit. The insulation monitoring apparatus according to any one of claims 1 to 6, further comprising a protection circuit that protects the monitoring signal generation circuit from an electric current. A monitoring signal generating circuit for injecting a monitoring signal having a frequency different from the commercial frequency into the B-type ground line of the transformer;
A reference signal corresponding to the monitoring signal is extracted from a D-type ground reference input taken from the B-type ground line, and based on a predetermined clock frequency, the phase of the reference signal is set to the low-voltage side circuit of the transformer. A phase adjustment circuit that adjusts to the opposite phase of the ground capacitance, and
Detecting means for detecting a current flowing in the B-type ground line;
A measurement signal detection circuit for detecting a measurement signal by removing unnecessary components such as a commercial frequency and its harmonics from the detection output of the detection means;
Based on the reference signal output from the phase adjustment circuit, a synchronization signal for generating a synchronization signal for separating the ground insulation resistance of the low-voltage side electric circuit of the transformer and the ground capacitance included in the measurement signal A signal generation circuit;
Suppression that generates a suppression signal for canceling out the ground capacitance included in the measurement signal based on the reference signal output from the phase adjustment circuit and supplies the suppression signal to the suppression unit of the detection means A signal generation circuit;
Based on the measurement signal and the synchronization signal, the ground insulation resistance and the ground capacitance included in the measurement signal are separated, and the suppression signal generation circuit is configured so that the ground capacitance becomes zero. An arithmetic processing circuit that performs real-time control of a suppression level by the suppression signal and obtains the ground insulation resistance from the measurement signal based on the detection output of the detection unit in which the ground capacitance is canceled by the supply of the suppression signal;
An insulation monitoring device comprising:   9. The insulation monitoring apparatus according to claim 8, wherein the phase adjustment circuit adjusts the phase timing of the reference signal based on the predetermined clock frequency input from the arithmetic processing circuit.   The insulation monitoring apparatus according to claim 8 or 9, wherein the detection means is electromagnetically coupled to the B-type ground line, and the suppression signal is supplied to the tertiary side.   The monitoring signal generating circuit injects the monitoring signal into the B-type ground line via an injection unit, and an abnormality that is reversely injected into the output stage from the B-type ground line through the injection unit. The insulation monitoring apparatus according to claim 8, further comprising a protection circuit that protects the monitoring signal generation circuit from an electric current.

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