JP2007256023A - Method and circuit for measuring loss current by displacement current bypass method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit and method for measuring loss current by a displacement current bypass method capable of measuring the loss current at high sensitivity and high accuracy without being affected by noise even if a sample of a measured object has large size. <P>SOLUTION: The loss current measuring circuit 10 comprises a signal detecting section 20 and displacement current bypass section 30 interconnected through an optical fiber 11, detects a current flowing in a sample 1 from a voltage applying transformer 2 to which voltage V1 from a 2-channel signal transmitter 3 is applied with the signal detecting section 20, and outputs, to a monitor 4, loss current obtained by canceling the displacement current component from the detection signal with the displacement current bypass section 30. The signal detecting section 20 comprises a detection resistor 21 connected to the sample 1 in series, an amplifier 23, and an E/O converter 24. The displacement current bypass section 30 comprises an O/E converter 31 for converting input light into an electric signal, a resistor 32 connected to the output end thereof, and a bypass resistor 33 for adjusting the output amount to the resistor 32 of voltage V2 by negative polar cosine wave. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a loss current measuring method and a loss current measuring circuit applicable to a method for diagnosing water tree degradation of a power cable, and more particularly, in an insulator of a crosslinked polyethylene insulated power cable (hereinafter referred to as CV cable). The present invention relates to a loss current measuring method by a displacement current bypass method capable of measuring a flowing loss current component with high accuracy and a loss current measuring circuit thereof.

  The main deterioration form of a CV cable which is a typical power cable is water tree deterioration. This water tree deterioration is an alteration in the insulator caused by the action of moisture and electric field present in the CV cable insulator, and this alteration increases with the passage of time, thereby reducing the insulation performance of the CV cable. May lead to dielectric breakdown. Degradation diagnostic techniques for diagnosing this water tree degradation are being studied.

  For example, a current transformer is connected between the transformer that generates high voltage and the CV cable of the sample (measurement target), and a standard capacitor is connected to the transformer side of the current transformer. Applying an alternating voltage of the voltage, the current flowing in the standard capacitor and the current flowing in the cable insulator detected by the current transformer connected to the CV cable are input to the loss current measurement bridge and detected. A degradation diagnostic method is known in which only the loss current component is extracted by removing the displacement current component (displacement current component) of the CV cable, and further, the degradation of the CV cable is diagnosed based on the third harmonic component included in the loss current. (For example, refer to Patent Document 1).

  However, in the conventional loss current measuring method described in Patent Document 1, since the current transformer provided on the high voltage side applies a reactor, the capacitance of a sample such as a CV cable or other stray capacitance As a result of this combination, the detection circuit including the CV cable and the current transformer causes a resonance phenomenon, and the frequency characteristic of the detection signal is changed to cause waveform distortion. For this reason, an error occurs in the waveform analysis of the deteriorated signal. Furthermore, since the capacitance changes for each sample of the CV cable, that is, the resonance frequency changes for each sample, there is also a problem that the measurement conditions change for each sample.

  As a conventional degradation diagnosis method that is not affected by the capacitance of the sample such as the CV cable or other stray capacitance, for example, an arbitrary waveform generator is used, and a current signal flowing through the sample and a displacement current generated by the arbitrary waveform generator are used. A method is known in which a loss current is detected by adding (synthesizing) signals having opposite phases to each other and canceling the displacement current component from the current flowing through the sample (see, for example, Non-Patent Document 1).

  FIG. 6 shows a loss current measuring apparatus described in Non-Patent Document 1. The loss current measuring circuit 100 is configured based on the principle shown in FIG. 2 of Non-Patent Document 1, and a sample 1 such as a CV cable is connected to the loss current measuring circuit 100 and the secondary winding 2b. An electric transformer 2 that generates a high voltage, a two-channel signal transmitter 3 that generates a sine wave AC voltage V1 and a negative cosine wave AC voltage V2, and a signal from the loss current measurement circuit 100 are observed and processed. The combination with the monitor 4 constitutes a loss current measuring device.

  The loss current measuring circuit 100 includes an input unit 101 connected to an outer conductive portion such as a shielding layer of the sample 1, an amplifier 102 having an input terminal connected to the input unit 101, and connected between the input unit 101 and the ground. A detection resistor 103 and a bypass resistor 104 connected between the input unit 101 and the output terminal of the AC voltage V2 of the two-channel signal transmitter 3 are provided.

  In FIG. 6, the two-channel signal transmitter 3 applies the AC voltage V <b> 1 to the primary winding 2 a of the power transformer 2 and grounds the AC voltage V <b> 2 via the bypass resistor 104 and the resistor 103 of the loss current measuring circuit 100. Apply between.

  When the AC voltage V1 is applied to the primary winding 2a of the voltage transformer 2, a high voltage corresponding to the winding ratio is generated in the secondary winding 2b, and the voltage is applied to the core wire of the sample 1. With the application of this voltage, the energization loop 5 of the secondary winding 2b to the sample 1 to the detection resistor 103 to the secondary winding 2b is formed, and the insulator portion of the sample 1 according to the degree of water tree deterioration of the sample 1 A voltage drop occurs in the detection resistor 103 due to the current i flowing through the outer conductive portion through the detection resistor 103. On the other hand, the AC voltage V <b> 2 from the two-channel signal transmitter 3 is applied to the detection resistor 103 via the bypass resistor 104.

The voltage generated in the detection resistor 103 by the current from the sample 1 and the AC voltage V2 are added at the input terminal of the amplifier 102, thereby canceling the displacement current component with respect to the current flowing through the sample 1. The addition result is amplified by the amplifier 102, and the amplified output is observed by the monitor 4.
JP 2004-354093 A 2005 IEEJ National Convention 2-S10 (17-20 pages)

  When the conventional loss current measuring apparatus described in Non-Patent Document 1 is applied to a small-sized sample, since the loop of the energization loop 5 is small, the loss current is not affected by signal attenuation or external intrusion noise. Can be measured with high sensitivity. However, when applied to a CV cable sample installed on a real line, the distance between the amplifier of the loss current measurement circuit and the application point of the applied voltage is increased, so that the energization loop 5 becomes large, and the effects of signal attenuation and external intrusion noise are affected. It is not easy to measure the loss current with high sensitivity. In addition, in order to bring the amplifier and the applied voltage application point close to each other, strict safety measures are required, so that the practicality is poor.

  Accordingly, an object of the present invention is to provide a displacement current bypass capable of measuring a loss current with high sensitivity and high accuracy without being affected by signal attenuation or external intrusion noise even when a CV cable sample is large. It is an object of the present invention to provide a loss current measurement method and a loss current measurement circuit thereof.

  In order to achieve the above-described object, the present invention provides a detection signal by connecting a detection resistor in series to a measurement object charged during measurement and amplifying a voltage generated at both ends of the detection resistor by a current flowing through the detection resistor. And a signal for removing the displacement current component from the detection signal is applied to the bypass resistor, and the loss current is generated by superimposing the displacement current component removal signal flowing through the bypass resistor on the detection signal. A loss current measurement method using a displacement current bypass method is provided.

In order to achieve the above object, the present invention amplifies and detects a detection resistor connected in series to a measurement object charged during measurement and a voltage generated at both ends of the detection resistor by a current flowing through the detection resistor. A signal detection unit having an amplification unit that outputs the signal;
A bypass resistor to which a signal for removing a displacement current component from the detection signal from the signal detection unit is applied, and a loss current is calculated by superimposing a displacement current component removal signal flowing through the bypass resistor on the detection signal; Provided is a loss current measuring circuit using a displacement current bypass method, characterized in that it includes a displacement current bypass section to be generated.

  According to the loss current measuring circuit and the loss current measuring method of the present invention, it becomes possible to install the signal detection unit in the vicinity of the measurement target regardless of the shape of the measurement target, and the measurement target and the signal detection unit By shortening the distance between them, signal attenuation and intrusion of external noise can be prevented, and loss current can be measured with high sensitivity and high accuracy.

  The present invention provides a loss current measurement by a displacement current bypass method that can measure a loss current with high sensitivity and high accuracy without being affected by signal attenuation or external noise even when a measurement object is large. A circuit and a loss current measuring method thereof can be provided.

(Configuration of loss current measuring device by displacement current bypass method)
[First Embodiment]
FIG. 1 shows a loss current measuring apparatus according to a first embodiment of the present invention. This loss current measuring device generates a high voltage by connecting a sample 1 such as a CV cable to a secondary winding 2b, and generates a sine AC voltage V1 and a negative cosine AC voltage V2. A two-channel signal transmitter 3, a loss current measuring circuit 10 for measuring a loss current, and a monitor 4 for observing and processing a signal from the loss current measuring circuit 10.

  The loss current measuring circuit 10 has a signal detection unit 20 connected to the sample 1 and the power transformer 2 by a CV cable, an input unit connected to the signal detection unit 20 and the 2-channel signal transmitter 3, and a monitor 4 at the output end. The displacement current bypass unit 30 is connected to the displacement current bypass unit 30. The output end of the signal detection unit 20 and the input end of the displacement current bypass unit 30 are connected by an optical fiber 11 that is an optical transmission medium.

  The two-channel signal transmitter 3 has a configuration in which an alternating voltage V1 based on a sine wave is output as a channel 1 and an alternating voltage V2 based on a negative cosine wave (-cos θ) is output as a channel 2.

  The monitor 4 includes a display for displaying the observed waveform on the screen and a circuit for processing the input signal by FFT (Fast Fourier Transform).

(Configuration of signal detector)
The signal detection unit 20 includes a detection resistor connected in series between a high potential end H connected to the high potential side of the secondary winding 2 b of the voltage transformer 2 and a low potential end L connected to the core wire of the sample 1. 21, an arrester 22 connected in parallel to the detection resistor 21, an amplifier 23 as an amplifier having a pair of input terminals connected to the high potential terminal H and the low potential terminal L, and an output terminal of the amplifier 23. And an E / O converter 24 and a DC power supply unit 25 for supplying power to the electronic circuit unit of the amplifier 23 and the E / O converter 24.

  The detection resistor 21 is set to a resistance value at which a predetermined voltage drop is obtained by the current i flowing through the sample 1.

  The arrester 22 is an element for circuit protection that is inserted as necessary. The arrester 22 has non-linear characteristics, and suppresses the voltage across the detection resistor 21 to fall within a specified value when an overvoltage (surge) occurs across the detection resistor 21 due to dielectric breakdown of the sample 1 or the like. . The operation start voltage of the arrester 22 is sufficiently higher (for example, twice or more) than the detection voltage appearing at both ends of the detection resistor 21 so that waveform distortion is not caused by the displacement current flowing in the sample, and the withstand voltage of the amplifier 23 is increased. Set the value lower than the surge voltage.

  The amplifier 23 has a configuration in which a voltage generated at both ends of the detection resistor 21 is used as an input signal, and the input signal is amplified to a predetermined level and output as a detection signal.

  The E / O converter 24 has a circuit configuration for converting the output signal (detection signal) of the amplifier 23 from an electrical signal to an optical signal and outputting the optical signal to the optical fiber 11.

  For the DC power supply unit 25, a battery that does not require wiring for a power supply, has excellent mobility, and is not affected by external noise is suitable.

(Configuration of displacement current bypass section)
The displacement current bypass unit 30 includes an O / E converter 31 that converts an optical signal from the E / O converter 24 into an electrical signal, and a resistor 32 that is connected between the output terminal of the O / E converter 31 and the ground. A bypass resistor 33 to which a signal for removing a displacement current component connected between the output terminal of the AC voltage V2 of the two-channel signal transmitter 3 and the output terminal of the O / E converter 31 is applied.

  An output signal of the O / E converter 31 is generated at both ends of the resistor 32. Among these, a signal obtained by dividing the output signal of the two-channel signal transmitter 3 by the voltage dividing ratio of the bypass resistor 33 and the resistor 32 is superimposed on the resistor 32. For this reason, if the V2 AC voltage is divided to the same magnitude as the displacement current signal in the output signal of the O / E converter 31, the influence of the displacement current is eliminated and only the loss current is detected.

(Loss current measurement method using displacement current bypass method)
(Operation of the first embodiment)
Next, the operation of the loss current measuring apparatus in FIG. 1 will be described. In FIG. 1, when a high-voltage AC voltage V1 is applied from the 2-channel signal transmitter 3 to the primary winding 2a of the power transformer 2, the AC voltage generated in the secondary winding 2b is 20 is applied between the high potential end H and the ground. Due to this applied voltage, the current i flows in the energization loop 5 passing through the secondary winding 2b, the detection resistor 21 to the core wire of the sample 1, the outer conductive portion such as the shielding layer of the sample 1, and the secondary winding 2b. A voltage drop occurs in the resistor 21. The voltage generated at both ends of the detection resistor 21 is amplified by the amplifier 23 and output as a detection signal, and then the amplified output (detection signal) is converted into an optical signal by the E / O converter 24 and output to the optical fiber 11. Is done.

  In the displacement current bypass unit 30, the optical signal from the signal detection unit 20 is received by the O / E converter 31 through the optical fiber 11 and converted into an electrical signal, which is applied to the resistor 32 as the detection signal Sd. At the same time, the displacement current bypass unit 30 takes in the AC voltage V <b> 2 from the two-channel signal transmitter 3 via the bypass resistor 33 and applies it to the resistor 32.

  It is known that when the waveform of the applied voltage (V1) is a sine wave, the displacement current is theoretically a cosine wave (cos θ). Therefore, with respect to the sine waveform of the AC voltage V1, the output of the AC voltage V2 of the signal for removing the displacement current component due to the negative cosine wave (−cos θ) is adjusted by the bypass resistor 33, and the displacement current flowing through the bypass resistor 33 is adjusted. By superimposing the voltage of the component removal signal on the detection signal Sd from the sample 1, the displacement current component is canceled and only the loss current is generated and detected. This loss current signal is output to the monitor 4. The output adjustment by the bypass resistor 33 is performed so that the peak phase of the displacement current waveform (zero cross position of the sine wave) becomes 0 while observing the output of the displacement current bypass unit 30 with the monitor 4.

  FIG. 2 shows an output signal waveform observed by the monitor 4 of FIG. Here, the applied voltage is increased by 1 kV from 1 to 8 kV / mm and measured at 8 points, and waveforms corresponding to 1, 2, 3, 4, 5, 6, 7, and 8 kV / mm, respectively. 41-48 were obtained. As can be seen from FIG. 2, the loss current changes and the waveform distortion tends to increase as the applied voltage increases.

(Effects of the first embodiment)
According to the first embodiment, the following effects are obtained.
(A) Since the signal detection unit 20 including the amplifier 23 can be installed near the power transformer 2 and the sample 1 of the CV cable, signal detection and amplification in the immediate vicinity of the sample 1 can be performed. As a result, the energization loop 5 along the path of the voltage transformer 2 to the detection resistor 21 to the sample 1 to the ground to the voltage transformer 2 becomes small, so that intrusion of external noise can be suppressed. External noise becomes more prominent as the size (inductance) of the energization loop 5 increases. However, since the energization loop 5 is smaller in the present embodiment than in the prior art, the external noise reduction effect is enhanced. For this reason, signal detection can be performed with high sensitivity even if measurement is performed in a place with a poor noise environment.
(B) Since the detection signal from the detection resistor 21 is amplified by the amplifier 23 in the vicinity of the sample 1, it is possible to avoid a decrease in detection sensitivity due to subsequent attenuation of signal transmission.
(C) Since the detection signal is detected by the detection resistor 21, the detection signal is not distorted due to the resonance phenomenon caused by L and C, so that the change in the frequency characteristic of the detection signal can be prevented.
(D) The loss current measurement circuit 10 is physically divided into two parts, a signal detection unit 20 and a displacement current bypass unit 30, and the conventional loss current measurement circuit is obtained by optically insulating between them. Compared to 100, signal detection from the high potential end H side of the sample 1 can be performed easily and easily.
(E) Since the displacement current bypass unit 30 can be installed in the vicinity of the monitor 4, the bypass resistor 33 can be adjusted while using the monitor 4, so that the measurement can proceed efficiently.

[Second Embodiment]
FIG. 3 shows a loss current measuring apparatus according to the second embodiment of the present invention. In this embodiment, in the first embodiment, the arrangement of the sample 1 and the signal detection unit 20 is replaced to detect a signal from the low potential side of the sample 1, and the signal detection unit 20, the displacement current bypass unit 30, Are connected by a connection line 13 such as a cable, and the other configuration is the same as that of the first embodiment.

  With the configuration in which the signal detection unit 20 and the displacement current bypass unit 30 are connected by the connection line 13, the signal detection unit 20 does not use the E / O converter 24 and the DC power supply unit 25a from the first embodiment. The displacement current bypass unit 30 does not use the O / E converter 31 from the first embodiment.

(Operation of Second Embodiment)
In the present embodiment, when the AC voltage V1 is applied from the two-channel signal transmitter 3 to the voltage applying transformer 2, the energization loop 5 by the secondary winding 2b to the sample 1 to the detection resistor 21 to the secondary winding 2b. Current i flows, and a voltage drop occurs in the detection resistor 21. The voltage generated at both ends of the detection resistor 21 is amplified by the amplifier 23 and output as a detection signal, and then the detection signal is transmitted to the displacement current bypass unit 30 via the connection line 13.

  In the displacement current bypass unit 30, the detection signal from the signal detection unit 20 is applied to the resistor 32, and at the same time, the AC voltage V 2 of the signal for removing the displacement current component from the two-channel signal transmitter 3 is taken in via the bypass resistor 33. And applied to the resistor 32. At this time, the resistance value of the bypass resistor 33 and the output of the AC voltage V2 of the two-channel signal transmitter 3 are adjusted to adjust the AC voltage V2 applied to the resistor 32, and the displacement current component that has flowed through the bypass resistor 32 Only the loss current from which the displacement current component is canceled is generated and detected by superimposing the voltage of the removal signal on the detection signal Sd from the sample 1. This loss current signal is output to the monitor 4.

(Effect of the second embodiment)
FIG. 4 shows loss current detection characteristics of the second embodiment and the conventional loss current measuring apparatus shown in FIG. In the figure, a characteristic 51 is an applied voltage-loss current characteristic according to the second embodiment, and a characteristic 52 is an applied voltage-loss current characteristic obtained by the conventional loss current measuring apparatus shown in FIG.

  Referring to FIG. 4, in the characteristic 51 according to the second embodiment, the loss current increases in proportion to the increase of the applied voltage. On the other hand, in the conventional characteristic 52, the voltage dependency of the current value at 2 μA (3.5 kV applied voltage) or less is not observed. This is because the conventional loss current measurement circuit 100 has poor detection sensitivity and a high external noise level.

  As is clear from FIG. 4, the loss current can be measured with high sensitivity while the signal detection is performed from the low potential side of the sample 1 as in the conventional loss current measuring apparatus of FIG. This is because the energization loop 5 can be reduced by installing the detection resistor 21 and the amplifier 23 in the vicinity of the sample 1. Other effects are the same as (b), (c), and (e) in the first embodiment.

[Third Embodiment]
FIG. 5 shows a loss current measuring apparatus according to the third embodiment of the present invention. In this embodiment, the two-channel signal transmitter 3 is not used. For this purpose, the power transformer 2 has a configuration having the tertiary winding 2c, and further has a configuration in which the integrator 12 is connected between the tertiary winding 2c and the bypass resistor 33, and the other configuration is the first embodiment. It is the same as the form.

  The integrator 12 integrates the applied voltage phase information output from the tertiary winding 2 c when applying power to the applying transformer 2 and injects the integration result into the bypass resistor 33.

(Operation of the third embodiment)
In the configuration of FIG. 5, the applied voltage is applied to the primary winding 2 a of the applied transformer 2 by an optional application means (not shown). The alternating high voltage generated in the secondary winding 2b is applied between the high potential end H and the low potential side of the sample 1, and the secondary winding 2b to the detection resistor 21 to the core of the sample 1 to the sample 1 When the current i flows through the energization loop 5 passing through the outer conductive portion such as the shielding layer and the secondary winding 2b, a voltage drop occurs in the detection resistor 21. The voltage generated across the detection resistor 21 is amplified by the amplifier 23 and output as a detection signal. The detection signal is further converted to an optical signal by the E / O converter 24 and transmitted to the displacement current bypass unit 30. The

  At the same time, the applied voltage phase information is input to the integrator 12 from the tertiary winding 2c of the applying transformer 2, and integration is performed. The output signal of the integrator 12 is applied to the bypass resistor 33 of the displacement current bypass unit 30 as a signal for removing the displacement current component.

  In the displacement current bypass unit 30, the optical signal from the signal detection unit 20 is converted into an electric signal by the O / E converter 31, and this is applied to the resistor 32 as the detection signal Sd. Further, the bypass resistor 33 is adjusted to adjust the output voltage applied from the integrator 12 to the resistor 32. When the adjusted displacement current component removal signal is superimposed on the detection signal Sd, the displacement current component flowing through the resistor 32 is canceled. To do. The loss current signal generated and detected in this way is output to the monitor 4 and observed by the monitor 4.

(Effect of the third embodiment)
According to the third embodiment, the following effects are obtained.
(A) Since the two-channel signal transmitter 3 can be omitted, it is possible to reduce the connection change work accompanying the measurement.
(B) Even when the power supply voltage is distorted, the tertiary winding 2c and the integrator 12 can obtain a displacement current component removal signal that follows the waveform distortion. Therefore, compared with the first embodiment, the power supply noise Can be less affected by
Other effects are the same as those of the first embodiment.

  In the third embodiment, when the applied waveform is other than a sine wave, a circuit having a configuration of “inverting amplifier + differentiator” can be used instead of the integrator 12.

[Other embodiments]
The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

  For example, in each of the above embodiments, optical transmission can be changed to wireless transmission.

  In the first and third embodiments, the signal detection unit 20 is connected between the power transformer 2 and the sample 1. However, as in the second embodiment, the signal detection unit 20 is not shown in FIG. The sample 1 shown in FIG. That is, the sample 1 can be connected to the power transformer 2, and the signal detector 20 can be connected between the sample 1 and the ground.

  Further, the DC power supply unit 25 can be replaced with a solar cell or the like instead of the battery, and thus can be used as an on-line loss current measuring device for outdoor equipment. In this case, by performing a periodic measurement of the loss current value using an on-line loss current measuring device for outdoor equipment, an insulation deterioration diagnosis can be performed from the trend of the trend information of the measurement.

It is a circuit diagram of the loss current measuring device concerning a 1st embodiment of the present invention. It is a wave form diagram which shows the output signal waveform observed with the monitor of FIG. It is a circuit diagram of the loss current measuring device concerning a 2nd embodiment of the present invention. It is a characteristic view which shows the detection characteristic of the 2nd Embodiment of this invention and the conventional loss current. It is a circuit diagram of the loss current measuring device concerning a 3rd embodiment of the present invention. It is a circuit diagram of the loss current measuring device indicated in nonpatent literature 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sample 2 Electric power transformer 2a Primary winding 2b Secondary winding 2c Tertiary winding 3 2 channel signal transmitter 4 Monitor 5 Current supply loop 10 Loss current measuring circuit 11 Optical fiber 12 Integrator 13 Connection line 20 Signal detection part 21 Detection Resistor 22 Arrester 23 Amplifier 24 E / O converter 25 DC power supply unit 30 Displacement current bypass unit 31 O / E converter 32 Resistor 33 Bypass resistor 100 Loss current measuring circuit 101 Input unit 102 Amplifier 103 Resistor 104 Bypass resistor H High potential end L Low potential end

Claims (7)

A sensing resistor is connected in series to the object to be charged during measurement,
Amplifies the voltage generated at both ends of the detection resistor by the current flowing through the detection resistor and outputs it as a detection signal;
A displacement current is generated by applying a signal that removes a displacement current component from the detection signal to a bypass resistor, and superimposing a displacement current component removal signal that has flowed through the bypass resistor on the detection signal. Loss current measurement method by bypass method.   The loss current measurement method according to claim 1, wherein the generation of the loss current is performed by removing the displacement current component using a removal signal based on a negative cosine wave.   The generation of the loss current is performed by removing the displacement current component using a removal signal obtained by integrating the applied voltage phase information obtained from the applying transformer that performs the applying electric power. The loss current measuring method by the displacement current bypass method described. A signal detection unit having a detection resistor connected in series to a measurement object charged during measurement, and an amplification unit that amplifies a voltage generated at both ends of the detection resistor by a current flowing through the detection resistor and outputs the detection signal as a detection signal And
A bypass resistor to which a signal for removing a displacement current component from the detection signal from the signal detection unit is applied, and a loss current is calculated by superimposing a displacement current component removal signal flowing through the bypass resistor on the detection signal; A loss current measuring circuit according to a displacement current bypass method, characterized by comprising a displacement current bypass section to be generated.   5. The loss current measuring circuit according to claim 4, wherein the displacement current bypass unit removes the displacement current component using a removal signal generated by a negative cosine wave.   6. The displacement current bypass unit removes the displacement current component by using a removal signal obtained by integrating the applied voltage phase information obtained from the applying transformer that performs the applying electric power. Loss current measurement circuit by the displacement current bypass method described. The signal detection unit includes an electro-optical converter that converts an output of the amplification unit from an electric signal to an optical signal,
The displacement current bypass unit includes an optical-electrical converter that converts the optical signal from the electrical-optical converter of the signal detection unit into an electrical signal,
The loss current measuring circuit according to any one of claims 4 to 6, wherein the electro-optic converter and the opto-electric converter are connected by an optical transmission medium. .

Images