CN104391264B - Multi-function electronic transformer checking system and method for calibration - Google Patents

Abstract

A multifunctional electronic transformer calibration system and calibration method, the calibration system includes a calibration system for analog transformers and a calibration system for digital transformers, Agilent 3458A requires two Agilent 3458A), Agilent 33250, synchronization signal device, GPIB‑USB and self-developed supporting software. The invention does not need other additional built-in modules, its detection accuracy ratio error can reach 0.01%, and its phase error can reach 0.3', which fully meets the industrial detection requirements.

Description

Multifunctional Electronic Transformer Calibration System and Calibration Method

technical field

The invention relates to electronic transformers, in particular to a multifunctional electronic transformer calibration system and calibration method, which is suitable for calibrating the ratio error and phase error of electronic transformers with analog output or digital output in digital substations. test.

Background technique

In the mid-1990s, the International Electrotechnical Commission expected to develop digital integrated substations in the future, and formulated the IEC61850 series standards for future communication networks and systems in substations. The electronic transformer is the lowest measurement device in the substation, and its measurement data must conform to the data format specified by the IEC standard. In order to standardize and promote the development of electronic transformers, IEC formulated the electronic voltage transformer (referred to as EVT) standard IEC60044-7 and electronic current transformer (referred to as ECT) standard IEC60044-8 in 1999 and 2002 respectively. In 2007, my country's Transformer Standardization Technical Committee completed GB/T20840.7-2007 (Transformer - Part 7: Electronic Voltage Transformer) and GB/T20840.8-2007 (Transformer - Part 8: Electronic Voltage Transformer) type current transformer), which marks the official start of the promotion and application of electronic transformers in my country.

The secondary output of the traditional electromagnetic voltage transformer is 100V or The secondary output of the current transformer is 5A or 1A, while the sensing principle and output mode of the electronic transformer are completely different. Whether it is ECT or EVT, the secondary output signal is generally an analog small voltage (less than 4V) or Therefore, the verification method suitable for traditional electromagnetic transformers is no longer applicable to electronic transformers. The current verification and traceability system of electronic transformers in China is still blank. The ratio error and phase of electronic transformers Whether the error calibration is accurate or not directly affects the stability and safety of digital substation operation.

For the ECT of analog output, there are two kinds of verification methods commonly used at home and abroad:

One is similar to the difference calibration principle of the traditional current transformer, which is to add a U/I conversion standard after the tested ECT to convert its output signal into a current signal consistent with the traditional CT, but due to the two The secondary output voltage is very small (minimum 22.5mV), and it is very difficult to convert it into the standard secondary output of 5A and 1A, and there are additional errors of amplifier components and capacity matching problems;

The second method is the calibration method based on direct voltage measurement, as shown in Figure 5. Its advantage is that the magnitudes of the secondary output signals of the standard CT and the ECT to be tested do not need to be equal, but the method of data sampling requires that the two channels must be synchronized, otherwise Phase measurement errors will occur.

For digital output ECT, there are also two verification methods commonly used at home and abroad:

One method is to convert the digital output of the electronic transformer to be tested into an analog output signal and compare it with the analog secondary output signal of the standard transformer through D/A conversion. The advantage of this method is that the analog signal converted by D/A can be calibrated according to the difference method of the traditional electromagnetic transformer, and the cost is low; but the difficulty lies in how to accurately measure the phase error converted into the analog signal, This includes the time delay of data sampling, A/D conversion, data processing, D/A conversion and other links. The most important thing is that it is impossible to distinguish whether the time delay is the response problem of the transformer itself or the introduction of D/A conversion. .

Another method is to convert the analog output of the standard electromagnetic transformer into a digital signal through the A/D converter, the computer collects the standard digital signal, reads the measurement signal of the electronic transformer to be verified through the interface, and calculates it through DFT Measure the magnitude and phase of a signal. The measurement of this method adopts the measurement method of absolute error, which is generally only able to meet the calibration of the ratio error of the 0.2-level electronic transformer due to the influence of A/D accuracy, and because the time synchronization performance cannot determine the traceability, so Phase error is difficult to guarantee measurement accuracy.

Judging from the published patents, the impact of power grid frequency fluctuations on the inspection results is not considered, nor is it mentioned how to reduce the uncertainty of the measurement results.

Contents of the invention

The purpose of the present invention is to provide a multi-functional electronic transformer calibration system and calibration method. The system can keep the ratio difference at 0.01% and the phase difference within 0.3' when the frequency fluctuation is 35 Hz to 65 Hz. The amplitude improves the accuracy of phase measurement and calibration, and meets the calibration requirements of electronic transformers of 0.1S level and below.

Technical solution of the present invention is as follows:

A multifunctional electronic transformer calibration system, including two types: a calibration system for analog transformers and a calibration system for digital transformers:

A calibration system for analog transformers, characterized in that its composition includes: standard transformers, two Agilent3458A digital multimeters, function generators, inductive voltage dividers, standard I/V conversion shunts and electronic transformer control software And the PC of calculation software, the connection relation of each device is as follows: the secondary side of described standard transformer is connected with standard I/V conversion shunt, and the output terminal of this standard I/V conversion shunt is connected with the first Agilent3458A digital multimeter The input terminal of two HP3458A digital multimeters is connected with PC through GPIB-USB line, and described function generator is connected with described PC through GPIB-USB, and described function generator is connected with described two Agilent3458A digital The multimeter is connected, and the input terminal of the second Agilent3458A digital multimeter is connected to the secondary output terminal of the transformer under test.

A digital transformer calibration system is characterized in that its composition includes: standard transformer, the first Agilent3458A digital multimeter, function generator, induction voltage divider, standard I/V conversion shunt and electronic transformer control Software and calculation software PC, the connection relationship of each device is as follows: the secondary side of the standard transformer is connected to the standard I/V conversion shunt, and the output terminal of the standard I/V conversion shunt is connected to the first HP 3458A The input terminal of the digital multimeter, the first HP3458A digital multimeter is connected to the PC through the GPIB-USB line, the function generator is connected to the PC through the GPIB-USB, and the function generator is connected to the first The Agilent3458A digital multimeter is connected, and the detected merging unit of the transformer to be tested is connected with the PC.

The method for calibrating the simulated transformer to be tested by using the calibration system of the simulated transformer comprises the following steps:

1) Select the standard transformer according to the transformation ratio of the transformer to be tested. When the transformer to be tested is a current transformer, the primary current end of the standard transformer and the transformer to be tested are connected in series, and the secondary side of the standard transformer is connected to the standard I/V conversion shunt; when the transformer to be tested is a voltage transformer, the primary voltage terminals of the standard transformer and the transformer to be tested are connected in parallel, and the secondary side of the standard transformer is connected to the induction voltage divider, and the signal The generator accepts the synchronous sampling command sent by the PC, and the two 3458A digital multimeters start synchronously, respectively sampling the secondary output of the standard transformer and the transformer to be tested;

2) Start the program and initialize it;

3) Determine whether the program is connected successfully, if the connection is successful, continue to the next step, otherwise end, check whether the instrument connection line is connected;

4) configure Agilent 3458A and Agilent33250 parameters;

5) The PC sends a single enabling signal to the Agilent 3458A;

6) The PC grabs data from the Ethernet port, judges whether the packet capture is successful, and proceeds to the next step if successful, otherwise returns to step 5);

7) The PC reads the data of Agilent 3458A;

8) Use the improved quasi-synchronous algorithm to calculate the frequency difference and frequency, and judge whether the frequency is within the specified range. If it is outside the specified range, it is considered a wrong point and returns to step 4);

9) PC calculates the ratio difference and phase difference, the amplitude A1 and phase of the standard transformer Amplitude A2 and phase of the tested transformer The formula for calculating the ratio difference is The formula for calculating the phase difference is

10) Display the result;

11) Judging whether the verification is over, if not, return to step 4.

The method for calibrating the digital transformer to be tested by using the calibration system of the digital transformer comprises the following steps:

1) Select the standard transformer according to the transformation ratio of the transformer to be tested. When the transformer to be tested is a current transformer, the standard transformer and the primary current terminal of the transformer to be tested are connected in series, and the secondary side of the standard transformer is connected to the standard I/V Transformation shunt; when the transformer to be tested is a voltage transformer, the primary voltage terminals of the standard transformer and the transformer to be tested are connected in parallel, and the secondary side of the standard transformer is connected to the induction voltage divider, and the synchronization pulse sent by the synchronization device The signals are respectively output to the detected merging unit and the Agilent33250A signal generator of the electronic transformer to be tested. The detected merging unit on the secondary side of the measuring transformer starts synchronous sampling;

2) Start the program and initialize it;

3) Determine whether the program is connected successfully, if the connection is successful, continue to the next step, otherwise end, check whether the instrument connection line is connected;

4) configure Agilent 3458A and Agilent33250 parameters;

5) The PC sends a single enabling signal to the Agilent 3458A;

6) The PC grabs the data of the merged unit to be detected from the Ethernet port, and judges whether the packet capture is successful or not, and if successful, proceeds to the next step, otherwise returns to step 5);

7) The PC reads the data of Agilent 3458A;

8) Use the improved quasi-synchronous algorithm to calculate the frequency difference and frequency, and judge whether the frequency is within the specified range. If it is outside the specified range, it is considered a wrong point and returns to step 4);

9) PC calculates the ratio difference and phase difference, the amplitude A1 and phase of the standard transformer Amplitude A2 and phase of the tested transformer The formula for calculating the ratio difference is The formula for calculating the phase difference is

10) Display the result;

11) Judging whether the verification is over, if not, return to step 5).

Working principle of the present invention:

Electronic transformer with analog output: two Agilent3458A digital multimeters respectively sample the signals of the standard source and the transformer to be tested, convert them into digital signals, and then the PC reads the data of the two digital multimeters (Agilent 3458A);

Electronic transformer with digital output: Agilent3458A digital multimeter samples the standard source signal, the merged unit under inspection collects the signal of the transformer to be tested, and transmits it to the PC through Ethernet;

When the PC acquires two signals, it first calculates the frequency of the standard source signal, then calculates the amplitude and phase of the two signals respectively, and then calculates the ratio difference and phase difference between the transformer to be calibrated and the standard transformer, and saves it.

Features and technical effects of the present invention:

The invention has standard current and voltage transformer interfaces, electronic current and voltage transformer interfaces (Ethernet interface, USB interface). The invention compares the standard transformer with the calibrated transformer, calculates the ratio difference between the calibrated transformer and the standard transformer, the phase difference, and the phase and amplitude of each frequency instrument through an algorithm, and records the calibration results.

The present invention adopts the design idea of a virtual instrument, and configures the parameters of the instrument according to the needs through the supporting program of the PC, so that an important part of completing the whole system is the synchronization of the two-way signals.

The invention can verify the ratio difference between various types of electronic voltage transformers and current transformers with analog output, electronic voltage transformers and current transformers with digital output and various levels of electronic transformers , Phase difference, frequency and amplitude and phase calculation of two signals. In the power grid with complex working conditions and large frequency fluctuations, it can still meet the calibration requirements.

Description of drawings

Fig. 1 is a structural diagram of an electronic transformer calibration system with analog output in the present invention.

Fig. 2 is a structural diagram of the digital output electronic transformer calibration system of the present invention.

Fig. 3 is a program flow chart of the electronic transformer for supporting software analog output in the present invention.

Fig. 4 is a program flow chart of the electronic transformer for digital output of supporting software of the present invention.

Figure 5 is a circuit diagram of the existing calibration method based on direct voltage measurement

Detailed ways

The present invention relates to a multifunctional electronic transformer calibration system, including an electronic transformer calibration system with analog output as shown in Figure 1, including a standard transformer as a standard source signal; a transformer to be tested for providing a signal to be tested ; Two Agilent3458A digital multimeters, used to sample the standard transformer signal and the transformer signal to be tested respectively; Agilent33250 function signal generator, used to receive the trigger signal of the supporting software, and send out the trigger pulse to trigger the Agilent 3458A; GPIB-USB line, use It is used to connect PC, Agilent 3458A digital multimeter and Agilent 33250 function generator; the supporting software is mainly used to set the instrument, receive data, process data, and display important results such as ratio difference and phase difference.

The electronic transformer calibration system with digital output is shown in Figure 2, including the standard transformer as the standard source signal; the transformer to be tested is used to provide the signal to be tested; an Agilent 3458A digital multimeter is used to sample the standard source signal ; Agilent 33250 function generator, used to receive the trigger signal of the synchronization device, and send out the trigger pulse to trigger Agilent3458A; GPIB-USB cable, used to connect PC and HP3458A digital multimeter with Agilent 33250 function generator; supporting software is mainly used to set the instrument , receive data, process data, and display important results such as ratio difference and phase difference.

PC:

The required PC of the present invention should comprise USB interface, Ethernet interface, and USB interface realizes PC supporting software and instrument (Agilent3458A, Agilent33250) communication, and Ethernet interface realizes PC and checked merge unit communication, (can pass optical ether The network-to-power Ethernet device converts Ethernet data into data that the PC can obtain from the network port, so that the PC only needs to include a USB interface and an RJ45 network port).

The supporting software for PC of the present invention adopts the design concept of virtual instrument, and the control program includes instrument parameter configuration, calibration algorithm, calibration record, ratio difference and phase difference display, frequency calculation, image display and so on.

The electronic transformer program flow chart of the analog output of the supporting software of the PC is shown in Figure 3, and the specific process is as follows:

1) Select the standard transformer according to the transformation ratio of the transformer to be tested. When the transformer to be tested is a current transformer, the primary current end of the standard transformer and the transformer to be tested are connected in series, and the secondary side of the standard transformer is connected to the standard I/V conversion shunt; when the transformer to be tested is a voltage transformer, the primary voltage terminals of the standard transformer and the transformer to be tested are connected in parallel, and the secondary side of the standard transformer is connected to the induction voltage divider, and the signal The generator accepts the synchronous sampling command sent by the PC, and the two 3458A digital multimeters start synchronously, respectively sampling the secondary output of the standard transformer and the transformer to be tested;

2) Start the program and initialize it;

3) Determine whether the program is connected successfully, if the connection is successful, continue to the next step, otherwise end, check whether the instrument connection line is connected;

4) configure Agilent 3458A and Agilent33250 parameters;

5) The PC sends a single enabling signal to the Agilent 3458A;

6) The PC grabs data from the Ethernet port, judges whether the packet capture is successful, and proceeds to the next step if successful, otherwise returns to step 5);

7) The PC reads the data of Agilent 3458A;

8) Use the improved quasi-synchronous algorithm to calculate the frequency difference and frequency, and judge whether the frequency is within the specified range. If it is outside the specified range, it is considered a wrong point and returns to step 4);

9) PC calculates the ratio difference and phase difference, the amplitude A1 and phase of the standard transformer Amplitude A2 and phase of the tested transformer The formula for calculating the ratio difference is The formula for calculating the phase difference is

10) Display the result;

11) Judging whether the verification is over, if not, return to step 5).

The electronic transformer program flow chart of the digital output of the supporting software of the PC is shown in Figure 4, and the specific process is as follows:

1) The wiring mode of the transformer to be tested during measurement is shown in Figure 2. The standard transformer is selected according to the transformation ratio of the transformer to be tested. When the transformer to be tested is a current transformer, the primary current of the standard transformer and the transformer to be tested The terminals are connected in series, and the secondary side of the standard transformer is connected to the standard I/V conversion shunt; when the transformer to be tested is a voltage transformer, the primary voltage terminals of the standard transformer and the transformer to be tested are connected in parallel. The secondary side is connected to the induction voltage divider, and the synchronous pulse signal sent by the synchronizing device is respectively output to the detected combining unit of the electronic transformer to be tested and the 33250A signal generator. Under the action of the synchronous second pulse, the secondary side of the standard transformer The 3458A and the electronic transformer to be tested start synchronous sampling.

2) Start the program and initialize it;

3) Determine whether the program is connected successfully, if the connection is successful, continue to the next step, otherwise end, check whether the instrument connection line is connected;

4) configure Agilent 3458A and Agilent33250 parameters;

5) Send a single enabling signal to Agilent 3458A;

6) The PC grabs the data of the merged unit to be detected from the Ethernet port, and judges whether the packet capture is successful or not, and if successful, proceeds to the next step, otherwise returns to step 5);

7) The PC reads the data of Agilent 3458A;

8) The PC uses the improved quasi-synchronous algorithm to calculate the frequency difference and frequency, and judges whether the frequency is within the specified range. If it is outside the specified range, it is considered a wrong point and returns to step 5);

9) The PC calculates the ratio difference and phase difference, the amplitude and phase of the standard transformer and the tested transformer;

According to the sampling data of a single 3458A read by the PC, and the sampling data sent from the detected merging unit of the transformer to be tested captured from the Ethernet port, the rated transformers of the standard transformer and the transformer to be tested are respectively Calculate the respective amplitudes A1, A2 and initial phase and Ratio difference calculation formula The formula for calculating the phase difference is

10) Display the result;

11) Judging whether the verification is over, if not, return to step 5).

Function and performance of the present invention comprise following aspects:

1. This device can verify the current electronic transformer and voltage electronic transformer with analog output, the current electronic transformer and voltage electronic transformer with digital output;

2. The signal range of the electronic transformer interface for analog output is configured according to the transformer model;

3. The transmission protocol of the digital output electronic transformer conforms to the format specified in IEC61850-9-1, IEC61850-9-2 and IEC61850-9-2LE;

4. The PC supporting software of this device adopts the design method of virtual instrument. The interface is equipped with Agilent3458A and Agilent 33250A parameter settings. The ratio difference, phase difference, frequency, amplitude and phase are calculated through the improved quasi-synchronous algorithm, and displayed ; At the same time, it also displays the verification result, the waveform of the standard signal and the signal to be tested.

5. The signal range, sampling frequency, calibration times, standard transformation ratio and tested transformation ratio can be flexibly configured according to needs;

6. The device can achieve a ratio difference of 0.01% and a phase difference of 0.3' within the frequency range of 35-65 Hz.

Claims (2)

1. a kind of multi-function electronic transformer checking system is characterized in that its composition includes：Standard current transformer, standard electric Mutual inductor, two Agilent 3458A digital multimeter, signal generator, inductive voltage dividers, standard I/V is pressed to convert current divider With the PC machine with electronic mutual inductor control software and software for calculation, which has electric current, electricity The a variety of verifying functions of pressure, analog output, digital output；

When calibrating die analog quantity output type electronic mutual inductor, the secondary side of the standard current transformer meets standard I/V and becomes Current divider is changed, the secondary side of the standard potential transformer connects inductive voltage divider, standard I/V transformation current dividers or induction point The input terminal of the output termination First Agilent 3458A digital multimeter of depressor, two Agilent 3458A digital versatiles Table is connected to PC machine, the input termination of second Agilent3458A digital multimeter with signal generator by GPIB-USB lines The secondary output end of to-be-tested transformer, includes the following steps：

1) according to the transformation ratio selection standard mutual inductor of to-be-tested transformer, when mutual inductor to be measured is current transformer, standard is mutual The primary current end of sensor and to-be-tested transformer is connected, and the secondary side of standard mutual inductor connects standard I/V transformation current dividers；When to be measured Mutual inductor when being voltage transformer, the primary voltage end of standard mutual inductor and to-be-tested transformer is in parallel, the two of standard mutual inductor Secondary side connects inductive voltage divider, and the signal generator receives the synchronized sampling order that PC machine is sent out, two Agilent 3458A Digital multimeter starts to synchronize, respectively the secondary output of standard for manual sampling mutual inductor and to-be-tested transformer；

2) startup program is initialized；

3) whether successful connection continues in next step, otherwise to terminate, inspection apparatus connection determining program if successful connection Whether line connects；

4) Agilent 3458A digital multimeter and 33250 signal generator parameters of Agilent are configured；

5) PC machine described in sends out single to Agilent 3458A digital multimeter and enables useful signal；

6) PC machine captures data from Ethernet interface, judges that packet capturing success is no, success just carries out next step, otherwise returns to the 5) Step；

7) PC machine reads the data of two Agilent 3458A digital multimeter；

8) modified quasi-synchronous algorithm is utilized to calculate frequency difference and frequency, whether determination frequency is in prescribed limit, except regulation, Think wrong point, returns to the 4) step；

9) PC machine calculating ratio value difference and phase difference, the amplitude A1 and phase of standard mutual inductorThe amplitude A2 of tested mutual inductor and PhaseThe ratio difference calculation formula isThe calculation formula of the phase difference is

10) result is shown；

11) judge whether verification terminates, be not over and return to the 5) step.

2. multi-function electronic transformer checking system as described in claim 1, it is characterised in that can be used for check digit amount Electronic mutual inductor is exported, method of calibration includes the following steps：

The secondary side of the standard mutual inductor is met into standard I/V and converts current divider, the standard potential transformer it is secondary Side connects inductive voltage divider, and the output of standard I/V transformation current dividers or inductive voltage divider terminates First Agilent 3458A numbers The input terminal of word multimeter, First Agilent 3458A digital multimeter are connect with signal generator by GPIB-USB lines The combining unit digital output of PC machine, to-be-tested transformer is connected with the PC machine；

1) according to the transformation ratio selection standard mutual inductor of to-be-tested transformer, when it is to be measured be current transformer when, standard mutual inductor and wait for The primary current end series connection of mutual inductor is surveyed, the secondary side of standard mutual inductor connects standard I/V transformation current dividers；When to-be-tested transformer is When voltage transformer, the primary voltage end of standard mutual inductor and to-be-tested transformer is in parallel, selects the secondary side in standard mutual inductor Inductive voltage divider is connect, the synchronization pulse that synchronizing device is sent out is exported respectively to the tested merging list of electronic mutual inductor to be measured Member and signal generator, under the action of this lock-out pulse, the First Agilent of the standard mutual inductor secondary side 3458A digital multimeter and the tested combining unit of the to-be-tested transformer secondary side start synchronized sampling；

2) startup program is initialized；

3) whether successful connection continues in next step, otherwise to terminate, inspection apparatus connection determining program if successful connection Whether line connects；

4) parameter of Agilent 3458A digital multimeter and signal generator is configured；

5) PC machine described in sends out single to Agilent 3458A digital multimeter and enables useful signal；

6) PC machine captures from Ethernet interface and is detected combining unit data, judges that packet capturing success is no, in next step, otherwise success is with regard to carrying out Return to the 5) step；

7) PC machine reads the data of Agilent 3458A digital multimeter；

8) modified quasi-synchronous algorithm is utilized to calculate frequency difference and frequency, whether determination frequency is in prescribed limit, except regulation, Think wrong point, returns to the 5) step；

9) PC machine calculating ratio value difference and phase difference, the amplitude A1 and phase of standard mutual inductorThe amplitude A2 of tested mutual inductor and PhaseThe ratio difference calculation formula isThe calculation formula of the phase difference is

10) result is shown；

11) judge whether verification terminates, be not over and return to the 5) step.