JP5455776B2 - Current measuring device - Google Patents

Description

  The present invention relates to a current measuring device that is attached to, for example, a GIS (gas insulated switchgear) or the like and measures a current flowing through a central conductor thereof.

  A conventional current measuring device using a Rogowski coil, for example, as shown in Patent Document 1 below, converts a noise filter that removes harmonics from the output of the Rogowski coil and converts the output of the noise filter into an appropriate voltage value. Input adjustment unit, A / D conversion unit that converts an analog signal from the input adjustment unit into a digital signal, and a CPU that takes in the digital signal from the A / D conversion unit and performs processing necessary for subsequent current detection processing The current value flowing through the conductor is measured by transmitting the processing result of the CPU to the control device.

JP 2001-141755 A

  However, in the technique disclosed in Patent Document 1, the noise filter and the input adjustment unit that handle analog signals have individual variations with respect to the standard value, so that the output of each device is different. An error is generated. In addition, since the noise filter and the components that make up the input adjustment unit have temperature characteristics with respect to the standard value, the amplitude and phase of the output of the noise filter and input adjustment unit vary depending on the environmental temperature, resulting in current measurement. There was a problem that the error of the output of the apparatus was large in both amplitude and phase.

  The present invention has been made in view of the above, and obtains a current measuring apparatus capable of obtaining a stable output by suppressing errors due to variations in components constituting a noise filter and an input adjustment unit and temperature characteristics. With the goal.

In order to solve the above-described problems and achieve the object, the present invention provides a current measuring device for detecting a current flowing in a conductor, comprising: a noise filter for removing harmonic noise of an input signal; and an output of the noise filter. An input adjustment unit that converts the output adjustment value to an appropriate output amplitude value, an A / D conversion unit that converts the output of the input adjustment unit into digital data, a temperature sensor that detects an environmental temperature in which the device is installed, and the noise filter In addition, the temperature characteristics of the amplitude fluctuation and the phase fluctuation in the input adjustment unit are held, and the digital data is subjected to amplitude correction processing corresponding to the change in the environmental temperature, and the input signal is constant. comprising an arithmetic processing unit for outputting the processing result at the timing of the phase delay, and at the time of testing of the apparatus, is input to the noise filter as said input signal Connected to a simulation signal source that outputs a sine wave signal and a synchronization pulse synchronized with the sine wave signal, and the arithmetic processing unit generates the temperature characteristic of the amplitude fluctuation based on the output of the A / D conversion unit while, it characterized that you generate temperature characteristics of the phase fluctuation based on the phase difference between the synchronized zero-cross pulse signal and the sync pulses on the output of the input adjustment unit.

  According to the current measuring device of the present invention, there is an effect that a stable output can be obtained by suppressing errors due to variations in components constituting the noise filter and the input adjusting unit and temperature characteristics.

FIG. 1 is a diagram illustrating a configuration example of a current measuring apparatus according to an embodiment. FIG. 2 is a diagram illustrating an example of amplitude fluctuation for each environmental temperature. FIG. 3 is a diagram illustrating an example of temperature characteristics of amplitude fluctuation. FIG. 4 is a diagram showing the phase delay amount and the timing of each pulse. FIG. 5 is a diagram illustrating an example of a phase variation for each environmental temperature. FIG. 6 is a diagram illustrating an example of a temperature characteristic of phase variation. FIG. 7 is a diagram illustrating a connection example in actual operation of the current measuring device according to the embodiment.

  Hereinafter, a current measuring device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the following embodiments.

Embodiment.
FIG. 1 is a diagram illustrating a configuration example of a current measuring apparatus according to an embodiment. As illustrated in FIG. 1, the current measurement device 1 according to the embodiment includes a noise filter 14 and a signal processing unit 17. The output of the signal processing unit 17 is sent to the control device 22 and used for operations such as operation and monitoring of equipment including a GIS (not shown) during actual operation. The noise filter 14 is connected to a Rogowski coil (not shown) during actual operation and removes harmonics from the output signal of the Rogowski coil. However, when the current measuring device 1 is tested, the noise filter 14 As shown in FIG. 1, a simulated signal source 36 is connected instead of the Rogowski coil.

  When the current measuring device 1 according to the embodiment is applied to a power device such as GIS, for example, the rated frequency component of the output signal of the Rogowski coil input to the noise filter 14 is 50 Hz or 60 Hz which is a commercial power frequency. It becomes. Therefore, when the test of the current measuring device 1 is performed, the simulation signal source 36 outputs a predetermined sine wave signal 37 of 50 Hz or 60 Hz, as in actual operation. The simulated signal source 36 is a general signal generator that outputs a sine wave signal 37 and outputs a synchronization pulse 38 synchronized with the sine wave signal 37. The synchronization pulse 38 is a digital signal that is at a high level when the level of the sine wave signal 37 is a positive value and that is at a low level when the level of the sine wave signal 37 is a negative value.

  The signal processing unit 17 includes, as its internal configuration, an input adjustment unit 18 that converts the output of the noise filter 14 into an appropriate output amplitude value, and an A / D conversion unit that converts an analog signal from the input adjustment unit 18 into a digital signal. 19, an arithmetic processing unit (hereinafter referred to as “CPU”) 20 that takes in a digital signal from the A / D conversion unit 19 and performs processing for current detection, a noise filter 14, and a signal processing unit 17 are installed. The temperature sensor 31 for detecting the temperature of the environment, the analog signal from the input adjustment unit 18 and a reference potential (here, circuit ground potential) are compared, and the zero cross pulse signal 34 synchronized with the analog signal from the input adjustment unit 18. Of the zero cross pulse signal 34 from the comparator 32 and the synchronizing pulse 38 from the simulation signal source 36 is calculated. A phase difference signal generator 33 for generating a phase difference signal 35 of the zero-cross pulse signal 34 for the pulse 38, a.

  The CPU 20 includes a memory 20 a that holds temperature characteristics of amplitude fluctuation and phase fluctuation in the noise filter 14 and the input adjustment unit 18. The memory 20a may be provided outside the CPU 20 and connected to the CPU 20 so that writing and reading can be performed.

  Next, temperature characteristics of amplitude variation and phase variation in the noise filter 14 and the input adjustment unit 18 of the current measuring device 1 according to the embodiment will be described. The noise filter 14 and the input adjustment unit 18 generally function as a low-pass filter. For this reason, theoretical reduction of the output amplitude value and phase delay occur depending on the standard values of the components constituting the noise filter 14 and the input adjustment unit 18. The theoretical output amplitude value based on the standard values of the components constituting the noise filter 14 and the input adjustment unit 18 is hereinafter referred to as “output amplitude theoretical value”, and the standards of the components constituting the noise filter 14 and the input adjustment unit 18. The theoretical phase delay amount based on the value is hereinafter referred to as “phase delay amount theoretical value”.

  However, since the components constituting the noise filter 14 and the input adjustment unit 18 have individual variations with respect to the standard values, the actual values for the output amplitude theoretical value and the phase delay amount theoretical value are different for each device. Cause an error in output amplitude value and phase delay amount.

  Further, since the components constituting the noise filter 14 and the input adjustment unit 18 have temperature characteristics with respect to the standard value, the error of the output amplitude value and the phase delay amount for each apparatus varies depending on the environmental temperature. .

  Therefore, in the current measuring device 1 according to the embodiment, when the current measuring device 1 is tested, the temperature characteristics of the amplitude variation and the phase variation are generated for each device and stored in the memory 20a. By applying the temperature characteristics of these amplitude fluctuations and phase fluctuations to the digital signal after A / D conversion and outputting it, errors in output amplitude values and phase delay amounts due to component variations and temperature characteristics of each device To obtain a stable output.

  Next, generation of temperature characteristics of amplitude fluctuation and phase fluctuation of the current measuring apparatus 1 according to the embodiment will be described with reference to FIGS. FIG. 2 is a diagram illustrating an example of an amplitude variation for each environmental temperature, and FIG. 3 is a diagram illustrating an example of a temperature characteristic of the amplitude variation. FIG. 4 is a diagram showing the amount of phase delay and the timing of each pulse. In FIG. 4, the horizontal axis indicates time and the vertical axis indicates the level of each signal. In FIG. 4A, the relative phase delay amount of the output signal of the input adjustment unit 18 with respect to the sine wave signal 37. For the sake of simplicity, the levels of both signals are shown equally. FIG. 5 is a diagram illustrating an example of a phase variation for each environmental temperature, and FIG. 6 is a diagram illustrating an example of a temperature characteristic of the phase variation. The memory 20a stores in advance an output amplitude theoretical value and a phase delay amount theoretical value when a predetermined sine wave signal 37 is input from the simulation signal source 36.

  As described above, the temperature characteristics of the amplitude fluctuation and the phase fluctuation of the current measuring device 1 according to the embodiment are generated when the current measuring device 1 is tested. When testing the current measuring apparatus 1 according to the embodiment, as shown in FIG. 1, a simulated signal source 36 is connected instead of a Rogowski coil (not shown). A predetermined sine wave signal 37 input from the simulation signal source 36 is input to the A / D conversion unit 19 via the noise filter 14 and the input adjustment unit 18 and converted into digital data. On the other hand, the output signal of the input adjustment unit 18 is also input to the comparator 32 at the same time. Here, the output signal of the input adjustment unit 18 includes errors in the output amplitude value and the phase delay amount due to variations in components for each apparatus and temperature characteristics.

  The CPU 20 detects the output amplitude value for each environmental temperature from each digital data at different environmental temperatures (here, T1, T2, T3), and the output amplitude theoretical value stored in the memory 20a and each of the environmental temperatures. From the output amplitude value, calculate the ratio of each output amplitude value for each environmental temperature to the theoretical output amplitude value (hereinafter referred to as “output amplitude ratio”), and linearly interpolate the output amplitude ratio between each environmental temperature, A temperature characteristic of the amplitude variation shown in FIG. 3 is generated and stored in the memory 20a. The output amplitude ratio between the environmental temperatures can be calculated using, for example, the least square method. 2 and 3, the output amplitude values at three environmental temperatures are obtained. However, by detecting the output amplitude values at more environmental temperatures and obtaining the output amplitude ratio, the temperature of the amplitude fluctuation is obtained. The accuracy of characteristics can be increased.

  On the other hand, the comparator 32 compares the signal from the input adjustment unit 18 with a reference potential (here, circuit ground potential). When the signal from the input adjustment unit 18 is larger than the reference potential, the comparator 32 becomes a high level, and the input When the signal from the adjustment unit 18 is smaller than the reference potential, a zero cross pulse signal 34 that is at a low level is output. That is, the zero cross pulse signal 34 is a digital signal synchronized with the signal from the input adjustment unit 18.

  The phase difference signal generation unit 33 calculates an exclusive OR of the synchronization pulse 38 input from the simulation signal source 36 and the zero cross pulse signal 34 input from the comparator 32 to generate the phase difference signal 35. The phase difference corresponding to the High level pulse width of the phase difference signal 35 becomes the phase delay amount in the noise filter 14 and the input adjustment unit 18.

  The CPU 20 detects the phase delay amount for each environmental temperature from the high level pulse width of the phase difference signal 35 at different environmental temperatures (here, T1, T2, T3), and the theoretical value of the phase delay amount stored in the memory 20a. And the ratio of each phase delay amount for each environmental temperature to the theoretical phase delay amount (hereinafter referred to as “phase delay ratio”) from each phase delay amount at each environmental temperature, and the phase between each environmental temperature The delay ratio is linearly interpolated to generate the temperature characteristic of the phase fluctuation shown in FIG. 6 and store it in the memory 20a. The phase delay ratio between the environmental temperatures can be calculated using, for example, the least square method. 5 and 6, the phase delay amount at three environmental temperatures is obtained. However, by detecting the phase delay amount at more environmental temperatures and obtaining the phase delay ratio, the phase fluctuation temperature can be obtained. The accuracy of characteristics can be increased.

  Next, the operation at the time of actual operation of the current measuring apparatus 1 according to the embodiment will be described with reference to FIG. 1, FIG. 3, FIG. 6, and FIG. FIG. 7 is a diagram illustrating a connection example in actual operation of the current measuring device according to the embodiment. As shown in FIG. 7, in the actual operation of the current measuring apparatus 1 according to the embodiment, the Rogowski coil 3 for detecting the current flowing in the conductor 2 is connected instead of the simulated signal source 36 shown in FIG. . The memory 20a stores temperature characteristics of amplitude fluctuations and phase fluctuations generated when the current measuring apparatus 1 is tested.

  An input signal from the Rogowski coil 3 is input to the A / D conversion unit 19 via the noise filter 14 and the input adjustment unit 18 and converted into digital data.

  The CPU 20 reads the output amplitude ratio a corresponding to the environmental temperature t detected by the temperature sensor 31 from the temperature characteristics of the amplitude fluctuation stored in the memory 20a (FIG. 3), and the digital input from the A / D converter 19 Amplitude correction processing is performed by dividing the data by the read output amplitude ratio a. This suppresses errors in output amplitude values due to component variations and temperature characteristics of each device.

  Then, the CPU 20 reads the phase delay ratio b corresponding to the environmental temperature t detected by the temperature sensor 31 from the temperature characteristics of the phase fluctuation stored in the memory 20a (FIG. 6), and based on the read phase delay ratio b. Then, the processing result is output to the control device 22 at a timing at which a constant phase delay occurs with respect to the input signal. This suppresses errors in the phase delay amount due to component variations and temperature characteristics of each device.

  As described above, according to the current measurement device according to the embodiment of the present invention, the temperature characteristics of amplitude fluctuation and phase fluctuation in the noise filter and the input adjustment unit are held for each device, and the noise filter and signal processing are performed by the temperature sensor. The temperature of the environment in which the unit is installed is detected, the output amplitude ratio corresponding to the detected environmental temperature is read, the amplitude correction processing of the digital data output from the A / D conversion unit is performed, and the detected environment The phase delay ratio corresponding to the temperature is read out, and based on the phase delay ratio, the processing result is output to the control device at a timing that becomes a constant phase delay with respect to the input signal. Stable output can be obtained by suppressing errors in the output amplitude value and phase delay amount due to variations and temperature characteristics.

  In addition, when testing a current measuring device, a predetermined sine wave signal is input from a simulated signal source, which is a general signal generator, and an output amplitude ratio with respect to a theoretical output amplitude value is obtained for each different environmental temperature to obtain an amplitude. Generates a temperature characteristic of fluctuation and inputs a synchronization pulse synchronized with a predetermined sine wave signal to detect the phase delay amount in the noise filter and input adjustment unit, and the phase relative to the theoretical value of the phase delay amount for each different environmental temperature Since the delay ratio is obtained and the temperature characteristic of the phase fluctuation is generated, the temperature characteristic of the amplitude fluctuation and the phase fluctuation can be generated without requiring a measuring device other than the own apparatus.

  In the embodiment, the case where the present invention is applied to a current measuring device that measures a current flowing through a central conductor such as GIS has been described. However, the present invention can also be applied to a voltage measuring device or other industrial currents. / Can also be used in the field of voltage measuring devices.

  Further, in the embodiment, the configuration including the comparator and the phase difference signal generation unit and generating the temperature characteristics of the amplitude variation and the phase variation during the test has been described. However, the comparator and the phase difference signal generation unit are not provided. Even in the configuration in which the temperature characteristics of amplitude fluctuation and phase fluctuation are held in the CPU in advance, as in the embodiment, errors in the output amplitude value and the phase delay amount due to variations in parts for each apparatus and temperature characteristics are detected. Of course, it is possible to suppress and obtain a stable output.

  The configurations described in the above embodiments are examples of the configurations of the present invention, and can be combined with other known techniques, and a part of the configurations is omitted without departing from the gist of the present invention. Needless to say, it is possible to change the configuration.

  As described above, the current measuring device according to the present invention is useful as an invention that can suppress errors due to variations in the components constituting the noise filter and the input adjustment unit and errors due to temperature characteristics and can obtain a stable output.

DESCRIPTION OF SYMBOLS 1 Current measuring device 2 Conductor 3 Rogowski coil 14 Noise filter 17 Signal processing part 18 Input adjustment part
19 A / D conversion unit 20 CPU (arithmetic processing unit)
20a Memory 22 Controller 31 Temperature sensor 32 Comparator 33 Phase difference signal generator 34 Zero cross pulse signal 35 Phase difference signal
36 Simulated signal source 37 Sine wave signal 38 Sync pulse

Claims (4)

A current measuring device for detecting a current flowing through a conductor,
A noise filter that removes harmonic noise from the input signal;
An input adjustment unit for converting the output of the noise filter into an appropriate output amplitude value;
An A / D conversion unit for converting the output of the input adjustment unit into digital data;
A temperature sensor that detects the environmental temperature in which the device is installed;
The temperature characteristic of the amplitude fluctuation and the temperature characteristic of the phase fluctuation are held in the noise filter and the input adjustment unit, and the digital data is subjected to amplitude correction processing corresponding to the change in the environmental temperature, and the input signal An arithmetic processing unit that outputs a processing result at a timing with a constant phase delay,
Equipped with a,
At the time of testing the device itself, connected to a sine wave signal input to the noise filter as the input signal, and a simulation signal source that outputs a synchronization pulse synchronized with the sine wave signal,
The arithmetic processing unit includes:
A temperature characteristic of the amplitude variation is generated based on the output of the A / D conversion unit, and the temperature of the phase variation is based on a phase difference between the zero cross pulse signal synchronized with the output of the input adjustment unit and the synchronization pulse. current measuring device, characterized in that that generates a characteristic. A comparator for comparing the output and a reference potential of the input adjustment unit, and outputs the pre Kize b-cross pulse signal,
A phase difference signal generator for generating a phase difference signal between the previous SL zero-cross pulse signal and the synchronizing pulses,
Current measuring device according to claim 1, wherein the obtaining further Bei a. The phase difference signal generation unit generates the phase difference signal by calculating an exclusive OR of the synchronization pulse and the zero cross pulse signal,
The current measurement device according to claim 2, wherein the arithmetic processing unit detects a phase delay amount of the zero-cross pulse signal with respect to the synchronization pulse based on a pulse width of the phase difference signal. The arithmetic processing unit holds a theoretical value of output amplitude and a theoretical value of phase delay based on standard values of components constituting the noise filter and the input adjustment unit, and the theoretical value for the output amplitude for each different environmental temperature. A temperature characteristic of the amplitude fluctuation is generated by obtaining a ratio of an output amplitude value, and a temperature characteristic of the phase fluctuation is generated by obtaining a ratio of the phase delay amount to the phase delay amount theoretical value. Item 4. The current measuring device according to Item 3.

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