CN108845283B - Three-phase calibrator compatible with detection of electronic mutual inductor and traditional mutual inductor - Google Patents
Three-phase calibrator compatible with detection of electronic mutual inductor and traditional mutual inductor Download PDFInfo
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Abstract
The invention discloses a three-phase calibrator compatible with detection of an electronic transformer and a traditional transformer, which comprises: the invention relates to an electromagnetic type mutual inductor calibrator and an electronic type mutual inductor calibrator, which can accurately reflect the characteristics of an electronic type mutual inductor and a traditional mutual inductor in a working state, and compared with the existing calibrator, the electromagnetic type mutual inductor calibrator can overcome the defects of low efficiency, repeated wiring and the like of a single-phase method; the method has the advantages of being closer to the actual operation working condition, good in compatibility, high in detection system efficiency and the like; thereby can guarantee the fair and fair of electric energy measurement.
Description
Technical Field
The invention relates to the field of mutual inductor calibration, in particular to a three-phase calibration instrument compatible with detection of an electronic mutual inductor and a traditional mutual inductor.
Background
With the development of economy, the proportion of industrial development in national economic construction is increasingly sudden. In order to accurately measure electric energy, the investment of the mutual inductor is more and more extensive. At present, the traditional electromagnetic mutual inductor with an iron core is dominant in relay protection and measurement. However, with the construction of extra-high voltage and the gradual increase of the transmission capacity and the voltage grade of the power system, the traditional electromagnetic transformer has the defect that the traditional electromagnetic transformer is difficult to overcome. The electronic transformer using the optoelectronic technology and the optical fiber sensing technology can overcome the defects of the conventional transformer, so that the development of the electronic transformer becomes a necessary trend. However, the two transformers cannot completely replace each other, and therefore, the three-phase transformers in the power system are mainly divided into a traditional three-phase transformer and an electronic three-phase transformer.
As one of the key devices for data acquisition in the power grid, the role of the power transformer is very important, and mainly comprises: 1) the secondary side metering device is matched with the primary side metering device to realize accurate measurement of primary voltage and current; 2) the relay protection device is matched with a secondary side relay protection device to realize accurate protection and automatic control on power grid faults; 3) the electric isolation between the primary equipment and the secondary equipment is realized, the safety of the secondary equipment and operators is ensured, the high voltage and the large current on the primary side are converted into signals suitable for the secondary equipment, and the metering and relay protection are standardized. Therefore, in order to ensure accurate metering of the electric quantity of the system and high protection speed, the three-phase transformer needs to be calibrated.
The existing distribution network transformer operates under the actual working conditions of three phases of high voltage and large current. The traditional single-phase method has the problems of complex wiring, low detection efficiency and the like. The application provides a based on three-phase detection device to can check up electronic type three-phase transformer and electromagnetic type (tradition) three-phase transformer simultaneously.
Disclosure of Invention
The invention provides a three-phase calibrator compatible with detection of an electronic transformer and a traditional transformer, which can accurately reflect the characteristics of the electronic transformer and the traditional transformer in a working state, and compared with the existing calibrator, the calibrator can overcome the defects of low efficiency, repeated wiring and the like of a single-phase method; the method has the advantages of being closer to the actual operation working condition, good in compatibility, high in detection system efficiency and the like; thereby can guarantee the fair and fair of electric energy measurement.
In order to achieve the above object, the present application provides a three-phase calibration instrument compatible with detection of an electronic transformer and a conventional transformer, the three-phase calibration instrument includes:
electromagnetic type mutual-inductor check gauge includes: the system comprises a standard signal processing circuit, a measured signal processing circuit and a DSP controller, wherein the standard signal generates two paths of signals after passing through a gear shifting voltage division amplifier, a program control voltage division, a program control amplification and a low-pass filter, one path generates a zero-crossing pulse signal and is sent to the DSP controller, and the other path performs A/D conversion through an analog switch and is sent to the DSP controller for processing and displaying; the tested signal is transmitted to an analog switch for A/D conversion through a low-pass filter circuit through gear shifting, an amplifier, program-controlled voltage division and program-controlled amplification, and finally transmitted to a DSP controller for processing and displaying;
electronic transformer check gauge includes: the phase-locked frequency doubling circuit, the synchronous circuit, the two-stage program control amplification, the analog-to-digital converter, the singlechip system and the serial port are communicated; the singlechip system sends out a control A/D conversion command to realize the range switching of the programmable gain amplifier and realize the communication with an upper computer; the difference detection circuit is arranged in the industrial personal computer and is communicated with the upper computer through a serial port; the GPS sends out a clock signal to realize synchronous sampling of the standard signal and the difference signal; the synchronous circuit is used for comparing the phases of an input signal and an output signal of the voltage control oscillator, the phase difference of the two signals is kept constant, and phase locking is realized; the difference detection circuit firstly makes a difference between the standard signal and the signal to be detected, and amplifies the difference between the standard signal and the signal to be detected before A/D conversion so as to adjust the signal to the optimal input range suitable for A/D conversion.
The control of A/D conversion MAX and the switching of the gain of the program control amplifier are adopted, the communication with an upper computer is adopted, the single chip microcomputer AT89S52 is adopted to check the analog output of the electronic transformer by adopting a difference method, and the digital output of the electronic transformer is checked by adopting a direct method.
Further, a signal amplifier in the electromagnetic transformer calibrator consists of a primary amplifier, an intermediate amplifier and an output amplifier which are in signal connection in sequence, wherein the primary amplifier, the intermediate amplifier and the output amplifier are DJ409, TLC2652 and OP07 respectively.
Further, the voltage converter in the electromagnetic transformer calibrator includes: resistors R1-51, resistors R2-52 and an operational amplifier A53, wherein the resistors R1-51 have the resistance value of 99k omega and the accuracy of 0.01 percent, the resistor R2 has the resistance value of 1k omega and the accuracy of 0.01 percent, the operational amplifier A53 uses OPA277, and the THD + N of the OPA277 is 0.002 percent;
current converter in the electromagnetic type mutual-inductor check gauge includes: the current transformer T1-61, the resistor R3-62 and the operational amplifier A63, wherein the transformation ratio of the current transformer T1-61 is 5A/2mA, the accuracy is 0.005%, the resistance value of the resistor R2-62 is 500 omega, the accuracy is 0.01%, the operational amplifier A53 uses OPA277, and the THD + N is 0.002%.
Further, the DSP controller outputs a control command to a serial port of the program-controlled voltage source through the serial port to control the program-controlled voltage source to output voltage, a voltage standard transformer driving the boosting of the voltage is driven to boost the voltage value of the program-controlled voltage source to a primary voltage value, the primary voltage is simultaneously applied to the three-phase voltage of the detected electronic voltage transformer and a standard voltage transformer in the voltage standard transformer with the boosting, and a standard voltage transformer PT 32 in the voltage standard transformer with the boosting outputs secondary conversion voltage a/x of which the accuracy is 0.02 percent to a of the voltage converter0/x0The output of the voltage converter is connected to a channel of the channel synchronous sampling A/D converter, the secondary output of the three-phase voltage of the detected electronic voltage transformer is connected to the input of the voltage tracking and driving, the output voltage of the voltage tracking and driving is connected to the channel of the channel synchronous sampling A/D converter, the sampling value of the channel synchronous sampling A/D converter synchronous sampling channel is calculated, and the amplitude error and the phase error of the synchronous sampling channel are the amplitude error and the phase error of the detected electronic voltage transformer; the DSP controller outputs a control command through the serial port to be transmitted to the serial port of the program-controlled voltage source to control the program-controlled voltage source to output voltage, the current standard transformer driving the rising current is driven to rise the current value of the program-controlled voltage source into a primary current value, and the primary current is simultaneously applied to a primary terminal of the detected electronic current transformer and a current standard with the rising currentThe standard current transformer in the quasi-transformer, the standard current transformer in the current standard transformer with the current rising function outputs the secondary conversion current K1/K2 with the accuracy of 0.02 percent to the T of the current converter0/TxThe output of the current converter is connected to a channel of the channel synchronous sampling A/D converter, the secondary output of the three-phase current of the detected electronic current transformer is connected to the input of the voltage tracking and driving, the output voltage of the voltage tracking and driving is connected to the channel of the channel synchronous sampling A/D converter, the sampling value of the channel synchronous sampling A/D converter synchronous sampling channel is calculated, and the amplitude error and the phase error of the synchronous sampling channel are the amplitude error and the phase error of the three-phase current of the detected electronic current transformer.
Further, the synchronization circuit includes: the phase-locked loop is used for realizing real-time tracking of the sampling frequency of the difference signal to the frequency of the standard signal, and the Schmitt trigger changes the sine wave of the standard signal into a square wave signal required by a phase discriminator in the phase-locked device; the operational amplifier is used for amplifying the output signal of the standard mutual inductor; the phase-locked loop is used for realizing real-time tracking of the sampling frequency of the difference signal to the frequency of the standard signal, the Schmitt trigger is used for converting a sine wave of the standard signal into a square wave signal required by a phase discriminator in the phase-locked loop, and the operational amplifier is used for amplifying an output signal of the standard mutual inductor.
Further, the operational amplifier adopts LF356, the Schmitt trigger adopts CD4093 to shape the signal, the phase-locked loop adopts CD4046 to connect with the frequency divider CD4060, and the fourth pin of CD4060 connects with CD 4046.
Further, the two-stage programmable amplification comprises: PGA204, PGA 205; the magnification is from 1 time to 8000 times; the PGA gain stages are four types, namely 1, 10, 100 and 1000V/V, and the PGA205 gain stages are four types, namely 1, 2, 4 and 8V/V; considering that the difference between different measured signals and standard signals varies within a certain range, different amplification processes need to be performed according to different differences. The programmable gain amplifiers PGA204, 205 are able to meet this requirement. Both programmable gain amplifiers can have their gain digitally selected by two bit TTL or CMOS logic signals a0, a 1. The gains of PGA204 and PGA205 in the difference detection circuit are controlled by the singlechip according to the magnitude of the sampling signal.
Further, the analog-to-digital converter is MAX 125.
One or more technical solutions provided by the present application have at least the following technical effects or advantages:
the invention designs a set of compatible electronic and general electromagnetic three-phase calibrator; considering a three-phase combined transformer in actual engineering, the traditional single-phase measurement method cannot accurately reflect the real situation of the transformer, so that the accuracy of electric energy measurement is seriously influenced; the invention adopts a three-phase detection method, which is not only suitable for the traditional electromagnetic mutual inductor, but also suitable for the electronic mutual inductor; and a solid foundation is laid for the accuracy of electric energy measurement in the electric power system.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention;
FIG. 1 is a schematic diagram of a system of devices;
FIG. 2 is a schematic diagram of an error detection connection of an electronic transformer calibrator;
FIG. 3 is a schematic diagram of a conventional transformer calibrator error detection connection;
FIG. 4 is a basic schematic block diagram of a phase-locked loop;
fig. 5 is a block diagram of a synchronous circuit.
Detailed Description
In order that the above objects, features and advantages of the present invention can be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings. It should be noted that the embodiments and features of the embodiments of the present application may be combined with each other without conflicting with each other.
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those specifically described and thus the scope of the present invention is not limited by the specific embodiments disclosed below.
The device has the main functions of realizing the three-phase integral detection of the electronic transformer and also realizing the three-phase integral detection of the traditional electromagnetic transformer. According to the IEC60044-7/8 standard, both digital quantity and analog quantity output by the electronic transformer are required, so the designed calibrator needs to respectively calibrate the analog quantity and the digital quantity by using a difference method and a direct method, and a schematic diagram of the calibrator is shown in FIG. 1. The functional block diagram is explained below.
1) Traditional electromagnetic type mutual inductor calibrator
The three-phase traditional electromagnetic type mutual inductor calibrator mainly comprises: I/V converter, signal amplifier, low-pass filter, A/D converter, DSP and operation processing unit. The invention adopts DSP as data processing chip. After the standard signal passes through a gear shifting voltage division amplifier, program control voltage division, program control amplification and low-pass filtering, one path of the standard signal generates a zero-crossing pulse signal and sends the zero-crossing pulse signal to a DSP, and the other path of the standard signal is subjected to A/D conversion through an analog switch and then sent to the DSP for processing and displaying. The tested signal is transmitted to an analog switch for A/D conversion through a low-pass filter circuit through gear shifting, an amplifier, program-controlled voltage division and program-controlled amplification, and finally transmitted to a DSP for processing and displaying.
The signal amplifier preferably consists of a primary amplifier, an intermediate amplifier and an output amplifier, which are signal connected in sequence, and are DJ409, TLC2652 and OP07, respectively.
The DJ409 chip is an improved 8-path/double 4-path and CMOS analog multiplexer, and is used for analog signal acquisition, and the output voltage and the sampling voltage keep accurate and stable multiplying power relationship through a plurality of high-precision resistors. The control port of the DJ409 is connected with a digital signal, thereby playing a role of selecting the amplification factor. TLC2652 is a high precision chopper-stabilized operational amplifier produced by texas instruments using advanced LinCMOS processes. The chopper-stabilized operation mode enables the TLC2652 to have excellent direct-current characteristics, and influences of offset voltage and drift thereof, common-mode voltage, low-frequency noise, power supply voltage variation and the like on the operational amplifier are reduced to the minimum, so that the TLC2652 is very suitable for amplifying micro signals. The OP07 chip is a low-noise, non-chopper-stabilized single operational amplifier integrated circuit. Since OP07 has a very low input offset voltage, OP07 does not require additional zeroing measures in many applications. The OP07 has the characteristics of low input bias current and high open-loop gain, and the characteristics of low offset and high open-loop gain make the OP07 particularly suitable for high-gain measuring equipment and amplification of weak signals of a sensor.
The DSP controller uses an ADSP-BF533DSP (digital signal processing) chip of the ideno semiconductor.
The precision voltage converter consists of precision resistors R1-51, precision resistors R2-52 and a high-precision operational amplifier A53, wherein the resistance value of the precision resistors R1-51 is 99k omega, the accuracy is 0.01%, the resistance value of the precision resistors R2 is 1k omega, the accuracy is 0.01%, the high-precision operational amplifier A53 uses OPA277, and the THD + N (total harmonic distortion plus noise) is 0.002%.
The precision current converter consists of a precision current transformer T1-61, a precision resistor R3-62 and a high-precision operational amplifier A63, wherein the transformation ratio of the precision current transformer T1-61 is 5A/2mA, the accuracy is 0.005%, the resistance value of the precision resistor R2-62 is 500 omega, the accuracy is 0.01%, and the high-precision operational amplifier A53 uses OPA277THD + N (total harmonic distortion plus noise) and is 0.002%.
The voltage tracking and driving chip used a high precision operational amplifier a7 with OPA277THD + N (total harmonic distortion plus noise) of 0.002%.
The DSP controller outputs a control command to a serial port of the program-controlled voltage source through the serial port to control the program-controlled voltage source to output voltage, a voltage standard transformer driving a boosting belt to boost the voltage value of the program-controlled voltage source to a primary voltage value, the primary voltage is simultaneously applied to the three-phase voltage of the detected electronic voltage transformer and a standard voltage transformer in the voltage standard transformer with the boosting belt, and a standard voltage transformer PT 32 in the voltage standard transformer with the boosting belt outputs secondary conversion voltage a/x which is accurate to 0.02 percent to a of a precise voltage converter of the device0/x0The output of the precision voltage converter is connected to the channel synchronous sampling ADOn a channel of the converter, secondary output of three-phase voltage of the detected electronic voltage transformer is connected to input of voltage tracking and driving, output voltage of the voltage tracking and driving is connected to a channel of the channel synchronous sampling AD converter, sampling values of the channel synchronous sampling AD converter synchronous sampling channel are calculated through FFT algorithm and other algorithms, and amplitude errors and phase errors of the synchronous sampling channel are the amplitude errors and the phase errors of the detected electronic voltage transformer. The DSP controller outputs a control command to a serial port of the programmable voltage source through the serial port, controls the programmable voltage source to output voltage, drives a current standard transformer for current rise to increase the current value of the programmable voltage source into a primary current value, the primary current is simultaneously applied to a primary terminal of the detected electronic current transformer and a standard current transformer in the current standard transformer with current rise, the standard current transformer in the current standard transformer with current rise outputs secondary conversion current K1/K2 with the accuracy of 0.02 percent to T0/Tx of a precise current transformer of the device, the precise current transformer outputs to be connected to a channel of a channel synchronous sampling A/D converter, secondary outputs of three-phase currents of the detected electronic current transformer are connected to input of voltage tracking and driving, and output voltage of the voltage tracking and driving is connected to the channel of the channel synchronous sampling A/D converter, the channel synchronous sampling A/D converter synchronously samples the sampling value of the channel, and the amplitude error and the phase error of the synchronous sampling channel are calculated through an FFT algorithm, namely the amplitude error and the phase error of the three phases of the detected electronic current transformer.
The AD converter may be MAX125, where MAX125 is a 2X4 channel, 14-bit high-speed, simultaneous sampling, and successive approximation analog-to-digital conversion chip with parallel microcomputer interface, which is available from MAXIM corporation.
2) Electronic transformer calibrator
The three-phase electronic transformer calibrator mainly comprises: the phase-locked frequency doubling circuit, the synchronous circuit, the two-stage program control amplification, the analog-to-digital converter, the singlechip system and the serial port communication. The electronic three-phase electronic voltage transformer or the electronic three-phase electronic current transformer can be independently verified, and the electronic three-phase combined transformer can also be verified.
Firstly, selecting a method for verifying the analog output of the electronic transformer. The direct method in the digital verification method has simple structure and convenient manufacture, and the contained data information is large, but a high-accuracy data acquisition card is needed, so the cost is high; the difference method has low requirement on the accuracy of the difference measuring device, and can realize the calculation, storage, printing and the like of data on the basis of the virtual instrument technology. The calibration device developed by the difference method is low in cost and convenient for subsequent popularization, so that the difference method is adopted to calibrate the analog quantity. The analog signal sampling of the standard mutual inductor adopts a data acquisition card PCI4070 of NI company, and is directly inserted into a peripheral equipment interface (PCI) slot of an industrial personal computer. The relative sampling error of the acquisition card on the standard signal is not more than 0.05%. The difference detection circuit consists of differential amplification, programmable gain amplification, A/D conversion, phase-locked loop, single chip microcomputer and the like. The singlechip is used for sending a command for controlling A/D conversion, realizing range switching of the programmable gain amplifier and realizing communication with an upper computer. The difference detection circuit is arranged in the industrial personal computer and is communicated with the upper computer through a serial port. The GPS sends out a clock signal to realize synchronous sampling of the standard signal and the difference signal.
The digital output of the electronic transformer is checked by a direct method, namely, the output signal of the standard transformer is read into the upper computer through a data acquisition card PCI4070, and the digital output of the tested transformer is read into the upper computer from the merging unit through a network card. The analog quantity and the digital quantity are checked based on a Lab VIEW platform, and the ratio difference and the angle difference are obtained by adopting an FFT algorithm.
Designing a phase-locked frequency multiplication circuit: for a data sampling system, the accuracy requirement is a core problem, and the sampling mode is a key problem. The sampling method can be generally divided into two categories, namely asynchronous sampling and synchronous sampling. Asynchronous sampling means that the sampling frequency is kept unchanged, and the sampling frequency is generally an integral multiple of the power frequency. However, the frequency of the power system is not fixed and may deviate during operation. In this case, the sampling frequency and the reference frequency are no longer integer multiples, i.e., the sampling pulse and the input signal are asynchronous in time position. In this way, the accumulation algorithm may cause a large error, and therefore, it is not suitable for the situation where the requirement of data acquisition accuracy is high. Synchronous sampling can be divided into two modes of positioning sampling and tracking sampling. The positioning sampling can always keep the ratio of the sampling frequency and the reference frequency as an integer, and the sampling points are always positioned at a predetermined fixed position in the fundamental wave, i.e. the sampling process is strictly synchronized with the given phase of the measured sinusoidal fundamental wave. However, this approach will complicate the hardware technology, and the existing algorithms do not require the exact positioning of the sampling points and are therefore not used. Tracking sampling only requires that the sampling frequency tracks the change of the reference frequency, and the ratio of the sampling frequency to the reference frequency is kept as an integer. The tracking synchronous sampling can eliminate the calculation error of a general accumulation type algorithm caused by fundamental wave fluctuation, thereby improving the accuracy of the data acquisition system. The difference detection circuit adopts a synchronous sampling method based on a phase-locked loop. The basic schematic block diagram of the phase-locked loop is shown in fig. 4.
A synchronous circuit: the difference detection circuit synchronous circuit consists of a phase-locked loop, a Schmitt trigger and an operational amplifier. Because the calibrated transformer and the standard transformer both output signals from the same source, the frequencies of the calibrated transformer and the standard transformer are equal. The frequency of the difference signal and the frequency of the standard signal are equal. The phase-locked loop can realize real-time tracking of the sampling frequency of the difference signal to the frequency of the standard signal. The Schmitt trigger converts the sine wave of the standard signal into a square wave signal required by a phase detector in the phase lock device. The operational amplifier is used for amplifying the output signal of the standard mutual inductor. The operational amplifier uses a low-drift, high-speed, high-input-impedance LF356, which is characterized by a low input current, on the order of p A. Moreover, by adopting the operational amplifier, better bandwidth gain and signal-to-noise ratio can be obtained under the condition of more serious noise and interference. The Schmitt trigger shapes the signal by using CD4093, and the phase-locked loop combines CD4046 with a frequency divider CD 4060. Because in dynamic balance CD4046 tracks ultra low frequency signals. The reference frequency of the detection circuit is 50Hz, and N is selected to be proper so that the output of the voltage-controlled oscillator is as high as possible to reduce the output phase jitter. We have chosen to connect the fourth leg of CD4060 to CD4046, i.e. to frequency-multiply the signal by 64. The structure block diagram of the synchronous circuit is shown in figure 5.
Two-stage program control amplification design: the difference detection circuit firstly needs to make a difference between the standard signal and the detected signal. According to the national standard, the analog quantity output of the electronic transformer does not have only one value, so that the possible size of the difference value under different input analog quantities needs to be considered. When the input analog quantity rated value is 6.5V, the possible maximum value of the difference value of the standard signal and the signal to be measured is as follows: Δ U is 6.5 × 2 × 2% ═ 0.26 (V). When the input analog rating is 22.5m V, the minimum possible value of the difference signal is: Δ U is 22.5 × 5% × 0.75% ═ 8.4375(μ V). In small signal systems, it is often desirable that the input to the a/D be close to its full scale value in order to meet accuracy requirements. Therefore, before the difference signal is sent to the A/D, we amplify it to adjust the signal to the optimum input range for A/D conversion. In the above calculations regarding Δ U, it can be seen that for the maximum difference we want to amplify it at least by a factor of 10, i.e. the minimum amplification of the input difference signal is 10, so we have selected the differential amplifier INA110KP with multiple gain amplification options and have selected the fixed 10 gain stage. The internal gain of the differential amplifier INA110KP has 5 gears which are selected from 1, 10, 100, 200 and 500; maximum nonlinearity is ± 0.01%; the maximum gain error is +/-0.1% when the internal gain is 10. For the minimum value of the difference signal, after the minimum value is fixedly amplified by 10 times, the minimum value can be amplified by 8000 times to meet the requirement. Considering that the difference between different measured signals and standard signals varies within a certain range, we need to perform different amplification processes according to different differences. The programmable gain amplifiers PGA204, 205 meet this requirement well. The PGA204 has four gain stages of 1, 10, 100 and 1000V/V, and the PGA205 has four gain stages of 1, 2, 4 and 8V/V.
Selection and application of the analog-to-digital converter ADC: analog-to-digital converters are widely classified into direct a/D converters and indirect a/D converters according to their operating principles. The direct a/D converter can directly convert an analog signal into a digital signal, and the a/D converter has a fast conversion speed, and typical circuits thereof include a parallel comparison type a/D converter and a successive comparison type a/D converter. The indirect a/D converter converts the analog signal into some intermediate quantity (time or frequency) and then converts the intermediate quantity into digital quantity for output. Such a/D converters are slow, and typical circuits are a dual integral a/D converter and a voltage-frequency conversion a/D converter. First, in consideration of the accuracy requirement, we should select a successive approximation a/D converter with relatively high conversion accuracy. Secondly, the A/D converter should have a sample holder integrated inside. Since discrete sample-and-hold units are less accurate and the performance requirements of the capacitors are so high that they are not easily achieved, reducing this step will undoubtedly improve the overall performance index. Furthermore, the resolution requirement of the a/D converter is relatively high because the difference signal is relatively small. According to the above requirements, the analog-to-digital converter MAX125 manufactured by american meixin corporation is selected as the difference detection circuit. MAX125 is a 36-pin, high-speed, 8-channel, 14-bit data acquisition system chip.
The singlechip system is communicated with a serial port: the control of the analog-digital converter MAX125, the switching of the gain of the program control amplifier and the communication with an upper computer need to be realized, the calculated amount is not very large, and only a certain control function needs to be realized, so that the single chip microcomputer AT89S52 is adopted. The single chip microcomputer is a low-power-consumption eight-bit CMOS process processor, is provided with an 8K online programmable Flash memory, and can be programmed for multiple times in a Flash chip. AT89S52 is a powerful processor that can provide a highly flexible, cost effective solution for many embedded applications.
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (6)
1. The utility model provides a compatible electronic transformer and three-phase check gauge that traditional mutual-inductor detected which characterized in that, three-phase check gauge includes:
electromagnetic type mutual-inductor check gauge includes: the system comprises a standard signal processing circuit, a measured signal processing circuit and a DSP controller, wherein the standard signal generates two paths of signals after passing through a gear shifting voltage division amplifier, a program control voltage division, a program control amplification and a low-pass filter, one path generates a zero-crossing pulse signal and is sent to the DSP controller, and the other path performs A/D conversion through an analog switch and is sent to the DSP controller for processing and displaying; tested signals are transmitted to an analog switch through a low-pass filter circuit for A/D conversion through a gear shifting voltage division amplifier, program-controlled voltage division and program-controlled amplification, and finally transmitted to a DSP controller for processing and displaying;
electronic transformer check gauge includes: the phase-locked frequency doubling circuit, the synchronous circuit, the two-stage program control amplification, the analog-to-digital converter, the singlechip system and the serial port are communicated; the singlechip system sends out a control A/D conversion command to realize the range switching of the programmable gain amplifier and realize the communication with an upper computer; the difference detection circuit is arranged in the industrial personal computer and is communicated with the upper computer through a serial port; the GPS sends out a clock signal to realize synchronous sampling of the standard signal and the difference signal; the synchronous circuit is used for comparing the phases of an input signal and an output signal of the voltage control oscillator, the phase difference of the two signals is kept constant, and phase locking is realized; the difference value detection circuit firstly makes a difference between the standard signal and the detected signal, and amplifies the difference value of the difference between the standard signal and the detected signal before A/D conversion so as to adjust the signal to the optimal input range suitable for the A/D conversion;
the synchronization circuit includes: the phase-locked loop is used for realizing real-time tracking of the sampling frequency of the difference signal to the frequency of the standard signal, and the Schmitt trigger changes the sine wave of the standard signal into a square wave signal required by a phase discriminator in the phase-locked device; the operational amplifier is used for amplifying the output signal of the standard mutual inductor; the phase-locked loop is used for realizing real-time tracking of the sampling frequency of the difference signal to the frequency of the standard signal, the Schmitt trigger is used for converting a sine wave of the standard signal into a square wave signal required by a phase discriminator in the phase-locked loop, and the operational amplifier is used for amplifying an output signal of the standard mutual inductor.
2. The three-phase calibrator compatible with electronic transformer and conventional transformer detection according to claim 1, wherein the operational amplifier of the electronic transformer calibrator comprises a primary amplifier, an intermediate amplifier and an output amplifier which are connected in sequence by signals, and the primary amplifier, the intermediate amplifier and the output amplifier are DJ409, TLC2652 and OP07 respectively.
3. The three-phase calibration instrument compatible with the detection of the electronic transformer and the traditional transformer as claimed in claim 1, wherein the DSP controller outputs a control command to the serial port of the programmable voltage source through the serial port to control the output voltage of the programmable voltage source, the voltage standard transformer driving the boosting of the driving belt raises the voltage value of the programmable voltage source to a primary voltage value, the primary voltage is simultaneously applied to the three-phase voltage of the detected electronic voltage transformer and the standard voltage transformer inside the voltage standard transformer with the boosting, and the standard voltage transformer PT 32 inside the voltage standard transformer with the boosting outputs a secondary transformation voltage a/x with the accuracy of 0.02% to the a/x of the voltage converter0/x0The output of the voltage converter is connected to a channel of the channel synchronous sampling A/D converter, the secondary output of the three-phase voltage of the detected electronic voltage transformer is connected to the input of the voltage tracking and driving, the output voltage of the voltage tracking and driving is connected to the channel of the channel synchronous sampling A/D converter, the sampling value of the channel synchronous sampling A/D converter synchronous sampling channel is calculated, and the amplitude error and the phase error of the synchronous sampling channel are the amplitude error and the phase error of the detected electronic voltage transformer; the DSP controller outputs a control command through the serial port to be transmitted to the serial port of the program-controlled voltage source to control the program-controlled voltage source to output voltage, the current standard mutual inductor driving the current rise is driven to rise the current value of the program-controlled voltage source to be a primary current value,primary current is simultaneously applied to a primary terminal of the electronic current transformer to be detected and a standard current transformer in a current standard transformer with current rising, and the standard current transformer in the current standard transformer with current rising outputs secondary conversion current K1/K2 of which the output is accurate to 0.02 percent to T of the current transformer0/TxThe output of the current converter is connected to a channel of the channel synchronous sampling A/D converter, the secondary output of the three-phase current of the detected electronic current transformer is connected to the input of the voltage tracking and driving, the output voltage of the voltage tracking and driving is connected to the channel of the channel synchronous sampling A/D converter, the sampling value of the channel synchronous sampling A/D converter synchronous sampling channel is calculated, and the amplitude error and the phase error of the synchronous sampling channel are the amplitude error and the phase error of the three-phase current of the detected electronic current transformer.
4. The three-phase calibrator compatible with detection of an electronic transformer and a traditional transformer as recited in claim 1, wherein the operational amplifier adopts LF356, the schmitt trigger adopts CD4093 to shape the signal, the phase-locked loop adopts CD4046 to connect with the frequency divider CD4060, and the fourth pin of the CD4060 connects with the CD 4046.
5. The instrument of claim 1, wherein the two-stage programmable amplification comprises: PGA204, PGA 205; the magnification is from 1 time to 8000 times; the PGA204 has four gain stages of 1, 10, 100 and 1000V/V, and the PGA205 has four gain stages of 1, 2, 4 and 8V/V.
6. The three-phase calibration instrument compatible with electronic transformer and conventional transformer detection according to claim 1, wherein the analog-to-digital converter is MAX 125.
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| CN110749850A (en) * | 2019-11-04 | 2020-02-04 | 国网内蒙古东部电力有限公司电力科学研究院 | Method and system for testing transient step response time of direct-current electronic voltage transformer |
| CN111103564A (en) * | 2019-12-31 | 2020-05-05 | 山西互感器电测设备有限公司 | High-voltage transformer Internet of things field data acquisition and transmission standard device and method |
| CN112327237A (en) * | 2020-11-17 | 2021-02-05 | 国网四川省电力公司电力科学研究院 | Error calibration system and method for broadband wide-range current transformer |
| CN113820645A (en) * | 2021-09-16 | 2021-12-21 | 国网四川省电力公司营销服务中心 | Universal mutual inductor calibration equipment and mutual inductor calibration method |
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| CN101290345B (en) * | 2008-06-06 | 2010-10-13 | 北京浩霆光电技术有限责任公司 | Multifunctional mutual-inductor tester |
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