Transformer grounding current sampling circuit, measuring device, system and method

Abstract

The invention discloses a transformer grounding current sampling circuit, a transformer grounding current measuring device, a transformer grounding current measuring system and a transformer grounding current measuring method, and relates to the technical field of transformer grounding current measurement, and the transformer grounding current sampling circuit comprises a current sensor which is used for generating an induction current signal according to the grounding current of a to-be-measured transformer; a plurality of sampling resistors with different resistance values, the plurality of sampling resistors are sequentially connected in series with the current sensor, and the plurality of sampling resistors are used for sampling the induction current signals at the same time to obtain a plurality of sampling voltage signals; and sampling voltage signals corresponding to different sampling resistors are respectively used for calculating grounding current of different measuring ranges. The multi-range measurement requirement of the transformer grounding current can be considered, and the transformer grounding current measurement efficiency is improved.

Description

Technical Field

[0001] The present application relates to the technical field of transformer grounding current measurement, and in particular to a transformer grounding current sampling circuit, measurement device, system and method. Background Art

[0002] In related technologies, a multi-range solution of "current sensor + multi-channel analog switch + multi-channel conditioning circuits with different gains" can be used to measure the grounding current of the transformer to determine whether it has a multi-point grounding fault; wherein, the input signals of the multi-channel amplifier all come from the same sampling resistor connected in series with the current sensor, and are amplified to the appropriate current size through different circuit gains; when the current measurement range is not appropriate, the multi-channel analog switch is controlled by the microcontroller to connect to the conditioning circuit with appropriate gain to achieve range switching.

[0003] However, in the above solution, after switching the range, the sampling resistor needs to be used again for current sampling and subsequent measurement operations. The overall process is relatively cumbersome, and it is difficult to simultaneously take into account the measurement requirements of multiple ranges such as large range and small range, resulting in low current measurement efficiency. Summary of the Invention

[0004] The main purpose of this application is to provide a transformer grounding current sampling circuit, measurement device, system and method, aiming to solve the technical problem in related technologies that transformer grounding current measurement is difficult to simultaneously take into account multi-range measurement requirements and has low measurement efficiency.

[0005] To achieve the above objectives, the present application proposes a transformer grounding current sampling circuit, which includes: A current sensor is used to generate an induced current signal according to the ground current of the transformer to be measured; Multiple sampling resistors with different resistance values are connected in series with the current sensor in sequence. The multiple sampling resistors are used to sample the induced current signal at the same time to obtain multiple sampling voltage signals; the sampling voltage signals corresponding to different sampling resistors are used for ground current calculation of different ranges.

[0006] In one embodiment, the plurality of sampling resistors include a first sampling resistor and a second sampling resistor, and the resistance of the first sampling resistor is greater than the resistance of the second sampling resistor.

[0007] In one embodiment, the transformer ground current sampling circuit further includes a plurality of conditioning circuits connected to the plurality of sampling resistors in a one-to-one correspondence; The conditioning circuit is used to amplify and filter the sampling voltage signals at both ends of the corresponding sampling resistor.

[0008] In one embodiment, the transformer ground current sampling circuit further includes a plurality of amplitude limiting circuits connected in parallel with the plurality of sampling resistors in a one-to-one correspondence; The amplitude limiting circuit is used to perform amplitude limiting processing on the sampling voltage signal at both ends of the corresponding sampling resistor.

[0009] In addition, to achieve the above-mentioned purpose, the present application also proposes a transformer grounding current measuring device, which includes: A current sampling module, comprising a plurality of sampling resistors with different resistance values, a plurality of conditioning circuits and a plurality of amplitude limiting circuits; Among them, multiple sampling resistors are used to simultaneously sample the induced current signal to obtain multiple sampled voltage signals; the sampled voltage signals corresponding to different sampling resistors are respectively used to calculate the ground current of different ranges; multiple conditioning circuits are connected to the multiple sampling resistors in a one-to-one correspondence, and the conditioning circuits are used to amplify and filter the sampled voltage signals at both ends of the corresponding sampling resistors; multiple limiting circuits are connected in parallel with the multiple sampling resistors in a one-to-one correspondence, and the limiting circuits are used to limit the sampled voltage signals at both ends of the corresponding sampling resistors; an analog-to-digital conversion module connected to the plurality of conditioning circuits and configured to convert the processed plurality of sampled voltage signals into corresponding digital signals; The data processing module is connected to the analog-to-digital conversion module and is used to perform harmonic calculations on multiple digital signals to obtain ground current measurement results.

[0010] In addition, to achieve the above-mentioned purpose, the present application also proposes a transformer grounding current measurement system, which includes: The transformer grounding current measuring device as described above; and The current sensor is connected to the current sampling module of the transformer grounding current measuring device through a two-core wire, and is used to generate an induced current signal according to the grounding current of the transformer to be measured and transmit the induced current signal to the current sampling module.

[0011] In one embodiment, a transformer ground current measurement system includes: a first current sensor, the first current sensor being configured as an iron core current sensor, the iron core current sensor being disposed at an iron core grounding wire of the transformer to be measured, and being configured to generate a first induced current signal according to an iron core grounding current of the transformer to be measured; a second current sensor, the second current sensor being configured as a clamp current sensor, disposed on a clamp grounding wire of the transformer to be measured, and configured to generate a second induced current signal according to a clamp grounding current of the transformer to be measured; A first current sampling module is connected to the first current sensor; The second current sampling module is connected to the second current sensor.

[0012] In addition, to achieve the above-mentioned purpose, the present application also proposes a transformer grounding current measurement method, which can be used in the above-mentioned transformer grounding current measurement device. The transformer grounding current measurement method includes: The ground current signals of different ranges are sampled through the current sampling module; The sampling voltage signals at both ends of each sampling resistor are converted into corresponding digital signals through the analog-to-digital conversion module; The data processing module performs harmonic calculation on multiple digital signals to obtain ground current measurement results.

[0013] In one embodiment, the step of performing harmonic calculation on a plurality of digital signals by a data processing module to obtain a ground current measurement result includes: determining a first target digital signal from a plurality of digital signals; Performing harmonic calculation on the first target digital signal to obtain a first initial current measurement result; When the first initial current measurement result is within a preset range, performing harmonic calculations on a first target digital signal having a fundamental wave cycle length multiple times to obtain multiple first current measurement results; the preset range is the range corresponding to the first target digital signal; determining a ground current measurement based on an average of the plurality of first current measurements; If the first initial current measurement result is not within the preset range, the first target digital signal is re-determined from the remaining digital signals, and the step of performing harmonic calculation on the first target digital signal to obtain the first initial current measurement result is returned to, until the first initial current measurement result is within the range corresponding to the first target digital signal.

[0014] In one embodiment, the step of performing harmonic calculation on a plurality of digital signals by a data processing module to obtain a ground current measurement result includes: Performing harmonic calculation on the multiple digital signals to obtain multiple second initial current measurement results corresponding to the multiple digital signals; determining a second target digital signal from the plurality of digital signals based on the plurality of second initial current measurement results; performing harmonic calculations multiple times on a second target digital signal having a fundamental wave cycle length to obtain multiple second current measurement results; A ground current measurement is determined based on an average of the plurality of second current measurements.

[0015] One or more technical solutions proposed in this application have at least the following technical effects: The transformer grounding current sampling circuit provided in the present application includes a current sensor and multiple sampling resistors with different resistance values connected in series with the current sensor; the current sensor can convert grounding currents of different ranges into induced current signals, thereby the multiple sampling resistors with different resistance values connected in series with the current sensor directly and synchronously sample the induced current signals, and the sampling voltage signals corresponding to the different sampling resistors can be used for grounding current calculations of different ranges, so as to ensure that in the subsequent grounding current measurement, the transformer grounding current sampling circuit can directly and simultaneously provide sampling signals of multiple ranges for selection without reusing a single sampling resistor for sampling after the range is switched. In this way, the current measurement efficiency can be improved while taking into account the multi-range measurement requirements of the transformer grounding current. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0018] Figure 1 It is a structural diagram of a dual current sensor solution in the related art; Figure 2 This is a schematic diagram of the structure of a multi-range solution consisting of a "current sensor + multi-channel analog switch + multi-channel conditioning circuits with different gains" in the related art; Figure 3 This is a schematic diagram of the structure of the transformer ground current sampling circuit of this application; Figure 4 This is a schematic diagram of the structure of the transformer grounding current measurement system of this application; Figure 5 The schematic diagram of the transformer grounding current measurement system is a schematic diagram of the transformer grounding current measurement system that can simultaneously measure the grounding current of the core and the clamp; Figure 6 A schematic flow chart of the first embodiment of the transformer grounding current measurement method provided in this application; Figure 7 This is a brief flowchart of the transformer grounding current measurement method of this application.

[0019] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0020] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0021] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), such directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0022] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0023] During normal operation, the grounding current in the transformer's core or clamps is typically in the milliampere range, never exceeding 100mA. However, when multiple grounding points occur in the core or clamps, the grounding current increases significantly. Therefore, measuring the current in the ground lead can be used to determine whether the transformer has a multiple-point grounding fault. Because the grounding current in the core or clamps ranges widely, from milliamperes under normal circumstances to several amperes or even tens of amperes during a fault, current monitoring requires both high-current and high-precision low-current measurements.

[0024] In related technologies, there are three main solutions for current measurement. The first is a dual current sensor solution. Figure 1 It is a structural diagram of the dual current sensor solution in the related art, such as Figure 1As shown, transformer current can be measured using two current sensors with different ranges, large and small. The small-range sensor is responsible for measuring mA-level currents, while the large-range sensor is used to measure currents above several hundred mA. The currents measured by the small-range and large-range sensors are then processed by the corresponding conditioning circuits, analog-to-digital conversion modules, and the microcontroller to obtain the final current measurement results. In this solution, two sensors are required for current monitoring of the core and the clamp, respectively, for a total of four sensors. This increases hardware costs and complicates on-site installation, commissioning, and wiring. Some dual-current solutions integrate the conditioning circuit into the current sensor, directly outputting a voltage signal. While this facilitates subsequent data collection, it is more susceptible to external interference than the current signal. The sensor also requires additional power, further complicating wiring.

[0025] In order to simplify the circuit structure, the related technology proposes the second and third solutions. The second solution is a multi-range solution consisting of "current sensor + multi-channel analog switch + multi-channel conditioning circuits with different gains"; Figure 2 This is a structural diagram of a multi-range solution consisting of a "current sensor + multi-channel analog switch + multi-channel conditioning circuits with different gains" in the related art, such as Figure 2 As shown, the current sensor can monitor the transformer's ground current and output an induced current signal. This induced current signal is sampled through a sampling resistor. The microcontroller, through program control, switches a multi-channel analog switch to connect the signal collected by the sampling resistor to conditioning circuits with different gains (including multiple amplifier circuits with different gains and corresponding filter circuits), thereby achieving wide-range current measurement. However, since there is only one current sensor and one sampling resistor, the input signal of the multi-channel amplifier circuit comes from the same sampling resistor, and different circuit gains are required to amplify the input signal to the appropriate level. This makes it difficult to simultaneously meet the requirements of both large-scale and low-current high-precision measurement. Moreover, only one range of signal is collected at a time. If the selected range is inappropriate, the microcontroller needs to control the switching of the multi-channel analog switch to connect the sampled signal to an amplifier circuit with a different gain to achieve range switching. The signal is then collected again to calculate the current value. This complicates the control scheme and signal calculation process, and also affects the efficiency of current detection.

[0026] The third solution uses a current sensor and a digital programmable amplifier. The program adjusts the gain of the programmable amplifier to amplify signals of different amplitudes, thereby achieving wide-range current measurement. This is similar to the second solution. The input signals to be processed are all from a single source. It is also difficult to simultaneously take into account multi-range measurement requirements such as large and small ranges. The cumbersome calculation process affects the current detection efficiency.

[0027] In order to solve the above problems, a transformer grounding current sampling circuit of the present application is proposed, which includes a current sensor and multiple sampling resistors with different resistance values connected in series with the current sensor; wherein, the current sensor can generate an induced current signal according to the grounding current of the transformer to be measured, and the multiple sampling resistors with different resistance values can directly and synchronously sample the induced current signals of different ranges by being connected in series with the current sensor, so as to ensure that the transformer grounding current sampling circuit can simultaneously provide sampling signals of multiple ranges for subsequent grounding current measurement selection, without the need to switch ranges and reuse a single sampling resistor for sampling calculation. In this way, the current measurement efficiency can be improved while taking into account the multi-range measurement requirements of the transformer grounding current.

[0028] The following will describe and introduce the present invention through multiple embodiments.

[0029] See also Figure 3 , Figure 3 This is a schematic diagram of the structure of the transformer ground current sampling circuit in this application.

[0030] In this embodiment, the transformer ground current sampling circuit may include: a current sensor and a plurality of sampling resistors with different resistance values.

[0031] Among them, the current sensor is used to generate an induced current signal based on the grounding current of the transformer to be measured; multiple sampling resistors are connected in series with the current sensor in sequence, and the multiple sampling resistors can be used to simultaneously sample the induced current signal to obtain multiple sampling voltage signals; the sampling voltage signals corresponding to different sampling resistors are used for grounding current calculations of different ranges.

[0032] Specifically, the current sensor can be a current sensing device such as a current transformer. The current sensor is generally arranged on the grounding wire of the transformer to monitor the grounding current of the transformer in real time, and convert the monitored grounding current into an induced current signal for output. The size of the induced current signal is proportional to the strength of the grounding current, so the grounding current condition of the transformer can be reflected by the induced current signal; and the current sensor outputs a current signal, which has a strong anti-interference performance compared with the voltage signal. Even after transmission through a longer wire, it can still maintain a high signal-to-noise ratio, which can ensure the accuracy of subsequent grounding current measurements.

[0033] A plurality of sampling resistors with different resistance values can be connected in series with the current sensor through wires in sequence, and the sampling resistors with different resistance values can sample the induced current signal at the same time to obtain a sampled voltage signal; and the sampled voltage signals corresponding to the different sampling resistors are used for the calculation of the grounding current of different ranges; wherein, for small-scale current measurement, a large-resistance sampling resistor can be used to obtain sufficient voltage signal amplitude, thereby improving the signal-to-noise ratio and subsequent measurement accuracy; for large-scale current measurement, a small-resistance sampling resistor can be used to prevent signal saturation and cutoff, ensuring that the sampled signal is within the processable range of the subsequent analog-to-digital conversion module. It should be noted that the resistance setting of the above-mentioned plurality of sampling resistors with different resistance values can be selected according to the actual range requirements. Generally, a smaller range corresponds to a larger resistance sampling resistor, and a larger range corresponds to a smaller resistance sampling resistor; by setting a plurality of sampling resistors with different resistance values in series, signals of different ranges can be collected at the same time, thereby, in the subsequent signal measurement and processing, multiple range measurement values can be selected at the same time, without the need to resample after the range is switched, which can improve the overall efficiency of the transformer grounding current measurement. In one feasible embodiment, the multiple sampling resistors may include a first sampling resistor and a second sampling resistor, wherein the resistance of the first sampling resistor is greater than the resistance of the second sampling resistor. With this sampling resistor configuration, the voltage drop across the first sampling resistor is used for low current measurement to ensure that the sampled voltage signal has sufficient amplitude and signal-to-noise ratio. The voltage drop across the second sampling resistor is used for high current measurement to ensure that the corresponding sampled voltage signal is sufficiently small to prevent signal saturation and cutoff. The configuration of the first sampling resistor and the second sampling resistor enables the acquisition of dual-range current signals, meeting the dual requirements of high-precision low current measurement and wide-range high current measurement.

[0034] In order to improve the signal quality of the sampled voltage signal and ensure the accuracy and reliability of subsequent data processing, Figure 3 As shown, the transformer ground current sampling circuit may further include a plurality of conditioning circuits connected to the plurality of sampling resistors in a one-to-one correspondence; the conditioning circuits are used to amplify and filter the sampled voltage signals across the corresponding sampling resistors; each of the conditioning circuits may include an amplifier and a filter; the amplifier may amplify the sampled voltage signal so that the sampled voltage signal is within the processable range of the subsequent analog-to-digital conversion module, facilitating subsequent processing and measurement; the filter may remove unnecessary noise from the sampled voltage signal, ensuring the purity of the voltage signal, thereby improving the accuracy and reliability of subsequent data processing.

[0035] In addition, since multiple sampling resistors with different resistance values will simultaneously perform current sampling in actual current sampling, when a large current range flows through a large resistance sampling resistor, the sampling voltage signal across the sampling resistor may be too large, which will impact and damage the subsequent conditioning circuit, analog-to-digital conversion module, etc.; Therefore, in a feasible implementation method, such as Figure 3 As shown, the transformer ground current sampling circuit may further include a plurality of limiting circuits connected in parallel with the plurality of sampling resistors in a one-to-one correspondence; that is, a limiting circuit is connected in parallel with each sampling resistor; the limiting circuit is mainly used to limit the sampling voltage signal across the corresponding sampling resistor to protect the subsequent conditioning circuit and the analog-to-digital conversion module used for measurement from being damaged.

[0036] It is not difficult to see that in the transformer grounding current sampling circuit provided in this embodiment, the current sensor can convert grounding currents of different ranges into induced current signals, thereby directly and synchronously sampling the induced current signals with multiple sampling resistors of different resistance values connected in series with the current sensor. The sampling voltage signals corresponding to the sampling resistors of different resistance values can be used for grounding current calculations of different ranges, respectively. This ensures that in the subsequent grounding current measurement, the transformer grounding current sampling circuit can directly and simultaneously provide sampling signals of multiple ranges for selection without the need to reuse a single sampling resistor for sampling after the range is switched. In this way, the current measurement efficiency can be improved while taking into account the multi-range measurement requirements of the transformer grounding current.

[0037] Furthermore, the present application also proposes a transformer grounding current measurement system, which may include a transformer grounding current measurement device and a current sensor; Figure 4 As shown, Figure 4 This is a structural diagram of a transformer grounding current measurement system; the above-mentioned transformer grounding current measurement device may include a current sampling module, an analog-to-digital conversion module, and a data processing module; wherein the current sampling module may include multiple sampling resistors with different resistance values, multiple conditioning circuits, and multiple limiting circuits; wherein the multiple sampling resistors are used to simultaneously sample the induced current signal to obtain multiple sampled voltage signals; the sampled voltage signals corresponding to different sampling resistors are respectively used to calculate grounding currents of different ranges; multiple conditioning circuits are connected to the multiple sampling resistors in a one-to-one correspondence, and the conditioning circuits are used to amplify and filter the sampled voltage signals at both ends of the corresponding sampling resistors; multiple limiting circuits are connected to the multiple sampling resistors in a one-to-one correspondence in parallel, and the limiting circuits are used to limit the sampled voltage signals at both ends of the corresponding sampling resistors.

[0038] like Figure 4As shown, the current sensor can be connected to the current sampling module of the transformer grounding current measuring device through a two-core wire. The current sensor can generate an induced current signal according to the grounding current of the transformer to be measured and transmit the induced current signal to the current sampling module; the current sensor and the current sampling module constitute the transformer grounding current sampling circuit as mentioned above, so the specific description of the transformer grounding current measuring device can also refer to the relevant content in the aforementioned transformer grounding current sampling circuit. Since the transformer grounding current measuring device and system of the present application adopt all the technical solutions of all the above-mentioned embodiments, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be repeated here.

[0039] The analog-to-digital conversion module is connected to multiple conditioning circuits, and can convert the sampled voltage signals at both ends of each sampling resistor after being processed by the conditioning circuit into corresponding digital signals so that the data processing module can perform data analysis and processing; the data processing module is connected to the analog-to-digital conversion module. After obtaining the multiple digital signals output by the analog-to-digital conversion module, the data processing module can perform harmonic calculation on the multiple digital signals to obtain the ground current measurement results of the transformer to be measured.

[0040] When performing harmonic calculations, the data processing module can usually use the harmonic method to calculate data for multiple fundamental wave periods at a time. This allows a single calculation to output a current RMS with a high signal-to-noise ratio. However, calculating digital signals for multiple fundamental wave periods at a time can be sensitive to the fundamental wave frequency. That is, when the fundamental wave frequency changes, the longer the data length of the digital signal used for harmonic analysis, the greater the current calculation error caused by the frequency difference. Therefore, in order to avoid the influence of fundamental wave frequency fluctuations, the data processing module can be used to perform harmonic calculations on a digital signal with a fundamental wave period length to obtain ground current measurement results. Performing harmonic calculations based on a digital signal with a fundamental wave period length ensures that the calculated data is always at the same frequency, thereby avoiding errors caused by frequency fluctuations and improving the accuracy of the ground current source measurement results.

[0041] Furthermore, since a digital signal with a fundamental wave length is relatively short, and short signal lengths may be affected by transient interference or noise during harmonic analysis, resulting in fluctuations in the measured value, to reduce the potential deviations caused by these fluctuations, the data processing module can also be used to perform multiple harmonic calculations on a digital signal with a fundamental wave period length, obtain multiple current measurement results, and determine the ground current measurement result based on these multiple current measurement results. Specifically, the data processing module can perform multiple independent calculations, each using data from a digital signal with a complete fundamental wave length to perform harmonic analysis, obtain a current measurement result, and then integrate these multiple accumulated current measurement results through statistical methods (such as mean, weighted mean, etc.) to obtain a more accurate current measurement result, thereby eliminating the potential deviations caused by a single measurement.

[0042] It is worth mentioning that in measuring the grounding current of the transformer, it may be necessary to measure the transformer core current and the clamp current to comprehensively determine whether the transformer has a multi-point grounding fault. Therefore, in a feasible embodiment, the transformer grounding current measurement system may include a first current sensor, a second current sensor, a first current sampling module, and a second current sampling module to simultaneously measure the core grounding current and the clamp grounding current. Figure 5 The diagram shows the structure of a transformer grounding current measurement system that can simultaneously measure the grounding current of the core and the clamp.

[0043] like Figure 5 As shown, the first current sensor can be configured as a core current sensor, which is installed on the core grounding wire of the transformer to be measured and is used to generate a first induced current signal based on the core grounding current of the transformer to be measured. The second current sensor can be configured as a clamp current sensor, which is installed on the clamp grounding wire of the transformer to be measured and is used to generate a second induced current signal based on the clamp grounding current of the transformer to be measured. The first current sensor is connected to the first current sampling module, and the second current sensor is connected to the second current sampling module. With this configuration, the number of data acquisition channels of the analog-to-digital conversion module can be doubled, allowing the sampled voltage signals output by the first and second current sampling modules to be connected to the same analog-to-digital conversion module for subsequent analysis and processing by the data processing module.

[0044] It should be noted that in actual wiring operations, the above-mentioned sampling resistor, limiting circuit and conditioning circuit, analog-to-digital conversion module and data processing module can be set in the same package to obtain the above-mentioned transformer grounding current measuring device, and then the core current sensor is installed on the core grounding wire of the transformer to be measured, and the clamp current sensor is installed on the clamp grounding wire of the transformer to be measured, and the current sensor is connected to the current sampling module in the transformer grounding current measuring device using a 2-core wire. This arrangement makes the wiring relatively simple, and the transmission path between the current sensor and the sampling resistor mainly transmits the current signal output by the current sensor, which has strong anti-interference performance and can still maintain a high signal-to-noise ratio even after transmission through a longer wire, without affecting the accuracy of the grounding current measurement.

[0045] It is not difficult to understand that in the transformer grounding current measurement system provided by this embodiment, the transformer grounding current sampling circuit related structure of the aforementioned embodiment is used to sample and process the transformer grounding current, and can sample induced current signals of different ranges at the same time to obtain multiple sampling voltage signals that can be used for grounding current calculation of different ranges; the obtained multiple sampling voltage signals, after being processed by the analog-to-digital conversion module, provide the data processing module with a variety of signal range selections, so that the data processing module can select the signal of the corresponding range for harmonic analysis according to actual needs, without the need to reuse a single sampling resistor for sampling after the range is switched, and can improve the current measurement efficiency while taking into account the multi-range measurement requirements of the transformer grounding current.

[0046] Furthermore, the present application also proposes a transformer grounding current measurement method, which can be used in the transformer grounding current measurement device as described in the above embodiment. Figure 6 , Figure 6 This is a flow chart of the first embodiment of the transformer grounding current measurement method of the present application.

[0047] In this embodiment, the transformer grounding current measurement method may include steps S100 to S300: Step S100 : sampling ground current signals of different ranges through a current sampling module.

[0048] In step S200 , the sampled voltage signals at both ends of each sampling resistor are converted into corresponding digital signals by an analog-to-digital conversion module.

[0049] Step S300: performing harmonic calculation on a plurality of digital signals by a data processing module to obtain a ground current measurement result.

[0050] Specifically, the current sensor can generate an induced current signal based on the ground current of the transformer to be measured, and simultaneously sample the current through multiple sampling resistors of different resistance values in the current sampling module to obtain multiple sampled voltage signals. The analog-to-digital conversion module then converts the sampled voltage signals across each sampling resistor into corresponding digital signals, and the data processing module further performs harmonic calculation on the multiple digital signals to obtain the ground current measurement results. Specific implementation details can be found in the aforementioned embodiments of the transformer ground current sampling circuit and transformer ground current measurement system, and will not be repeated here.

[0051] In a feasible implementation, step S300 may specifically include steps S310 to S350 to achieve accurate analysis and measurement of the ground current.

[0052] Step S310: Determine a first target digital signal from a plurality of digital signals.

[0053] Step S320 , performing harmonic calculation on the first target digital signal to obtain a first initial current measurement result.

[0054] In step S330, when the first initial current measurement result is within a preset range, harmonic calculation is performed multiple times on the first target digital signal of a fundamental wave cycle length to obtain multiple first current measurement results; the preset range is the range corresponding to the first target digital signal.

[0055] Step S340: determining a ground current measurement result based on an average value of the plurality of first current measurement results.

[0056] Step S350, when the first initial current measurement result is not within the preset range, re-determine the first target digital signal from the remaining digital signals, and return to the step of performing harmonic calculation on the first target digital signal to obtain the first initial current measurement result until the first initial current measurement result is within the range corresponding to the first target digital signal.

[0057] It is understandable that multiple sampling resistors can output multiple sampling voltage signals. After the multiple sampling voltage signals are processed by the analog-to-digital conversion module, multiple digital signals corresponding to the multiple sampling resistors can be obtained. The data processing module selects a first target digital signal from the digital signals corresponding to the multiple sampling resistors. The data processing module is usually set with an initial preset range by default. The first target digital signal is the digital signal obtained by the sampling resistor corresponding to the preset range. The first target digital signal is initially harmonically calculated using the harmonic method on the first target digital signal to obtain a first initial current measurement result. If the first initial current measurement result is within the selected range (i.e., the preset range), it indicates that the digital signal used in the current measurement meets the range selection. Further accurate calculation can be performed based on the first target digital signal: the harmonic calculation is repeated multiple times on the first target digital signal with a fundamental wave period length to obtain multiple first current measurement results. The multiple first current measurement results are then averaged to obtain the final ground current measurement result. If the initial current measurement result is not within the selected range (i.e., the preset range), it indicates that the digital signal used for the current measurement does not meet the range requirement, and it is necessary to reselect the first target digital signal from the remaining digital signals and return to the aforementioned step of performing harmonic calculation on the first target digital signal to obtain the first initial current measurement result until the first initial current measurement result is within the range corresponding to the first target digital signal.

[0058] In the above method, a signal with a fundamental wave cycle length is used for harmonic analysis, which can eliminate the current calculation error caused by the fundamental wave frequency fluctuation to the greatest extent. At the same time, it can realize automatic switching of the range. The optimal range selection and the output of the effective value of the ground current measurement can be achieved within one signal acquisition, ensuring the real-time and efficiency of current monitoring. For example, the first sampling resistor corresponds to the first digital signal, which is used for small-scale current measurement; the second sampling resistor corresponds to the second digital signal, which is used for large-scale current measurement; the data processing module is provided with an initial preset range (the default is small range), and at this time the data processing module selects the first target digital signal (i.e., the first digital signal) corresponding to the small range from the digital signals corresponding to multiple sampling resistors, and uses the first digital signal to perform harmonic calculation, and calculates the effective value of the fundamental and higher harmonic currents by the harmonic method to obtain the first initial current measurement result; then judge whether the first initial current measurement result is within the small range. If it is within the small range, it indicates that the current measurement range selection is correct, and multiple harmonic calculations can be performed on the first digital signal with a fundamental wave cycle length to obtain multiple first current measurement results; and the average value of these multiple first current measurement results is used as the final ground current measurement result. If the first initial current measurement result is not within the small range, it indicates that the ground current may be in the large range. At this time, the large range can be switched, that is, the data processing module automatically selects another digital signal (i.e., the second digital signal) as the new first target digital signal, and uses the second digital signal to perform harmonic calculation to obtain the first initial current measurement result corresponding to the second digital signal; then it is determined whether the first initial current measurement result is within the large range. If it is within the large range, multiple harmonic calculations are performed on the second digital signal with a fundamental wave cycle length and the calculation results are averaged to obtain the ground current measurement result.

[0059] Alternatively, in another feasible implementation, step S300 may specifically include steps S360 to S390: Step S360 , performing harmonic calculation on the multiple digital signals to obtain multiple second initial current measurement results corresponding to the multiple digital signals.

[0060] Step S370 : determining a second target digital signal from the plurality of digital signals based on the plurality of second initial current measurement results.

[0061] Step S380 , performing harmonic calculation on the second target digital signal having a fundamental wave cycle length multiple times to obtain multiple second current measurement results.

[0062] Step S390: determining a ground current measurement result based on an average value of the plurality of second current measurement results.

[0063] When the computing performance of the data processing module is high, preliminary harmonic calculations can be performed on multiple digital signals obtained from the analog-to-digital conversion module at the same time to obtain multiple second initial current measurement results corresponding to the multiple digital signals. Since each digital signal corresponds to a sampling resistor, and sampling resistors with different resistance values correspond to different measuring ranges, the measuring range corresponding to each digital signal can be compared with the second initial current measurement result calculated based on the digital signal. If the second initial current measurement result of a digital signal is within its corresponding measuring range, it indicates that this digital signal is the most suitable signal for calculating the ground current, and the digital signal can be used as the second target digital signal. Then, similar to the aforementioned embodiment, further precise calculations can be performed based on the second target digital signal: harmonic calculations are performed multiple times on the second target digital signal with a fundamental wave period length to obtain multiple second current measurement results. The average of these multiple second current measurement results is then taken to obtain the final ground current measurement result.

[0064] It is not difficult to understand that in the transformer grounding current measurement method provided in this embodiment, the grounding current signal can be sampled simultaneously through sampling resistors with different resistance values to obtain multiple sampled voltage signals; wherein, the sampled voltage signals corresponding to different sampling resistors can be used for grounding current calculations of different ranges respectively, and are converted into corresponding digital signals through the analog-to-digital conversion module, thereby providing the data processing module with a variety of signal range selections, making it convenient for the data processing module to select the corresponding range signal for harmonic analysis according to actual needs, without having to reuse a single sampling resistor for sampling after the range is switched, and can improve the current measurement efficiency while taking into account the multi-range measurement requirements of the transformer grounding current.

[0065] For example, to help understand the implementation process of the first embodiment of the transformer grounding current measurement method of the present application, please refer to Figure 7 , Figure 7A simplified flowchart of a transformer grounding current measurement method is provided. The transformer grounding current sampling circuit involved in this example is a dual-range sampling circuit consisting of a first sampling resistor, a second sampling resistor, and a current sensor. The dual ranges are a small range of 0 to 100 mA and a large range of 0 to 10 A. The current sensor uses a current transformer with a transformation ratio of 200:1. The maximum output induced current signals of the current sensor in the two ranges are 0.5 mA and 50 mA. The first sampling resistor has a resistance of 470 Ω and is used for sampling the small-range current signal. The second sampling resistor has a resistance of 4.7 Ω and is used for sampling the large-range current signal. The maximum amplitude of the sampled voltage signals corresponding to the two ranges is 235 mV. The amplitude limiters of the amplitude limiters corresponding to the first and second sampling resistors are both set at 2.5 V. The gain of the conditioning circuit is set to 30, resulting in a maximum output signal amplitude of 7.05 V and a bandwidth of 200 Hz. The sampling rate of the analog-to-digital conversion module is set to 1000 Hz. A single acquisition data point is one fundamental wave cycle (20 points in total). The fundamental wave frequency is 50 Hz. In the harmonic analysis, the effective values of the 50 Hz fundamental current and the 150 Hz third harmonic current are calculated to determine the ground current measurement result.

[0066] If the transformer generates an 8A ground current signal at this time, the ground current signal outputs a 40mA induced current signal after passing through the above-mentioned current sensor. The 40mA induced current signal generates a first sampling voltage signal of 40mA×470Ω=18.8V on the first sampling resistor, and a second sampling voltage signal of 40mA×4.7Ω=188mV on the second sampling resistor. The first sampling voltage signal is limited to 2.5V by the limiting circuit, and after being processed by the conditioning circuit, the obtained signal is 2.5V×30=75V (small-scale signal). The second sampling voltage signal is processed by the conditioning circuit to 5.64V (large-scale signal). Figure 7As shown, the analog-to-digital conversion module can simultaneously collect the output signals of the two conditioning circuits for subsequent processing. The data processing module selects the corresponding range signal for calculation based on the currently selected range (preset range). In the initial state, the preset range of the data processing module generally defaults to the small range, that is, the 75V small range signal is selected for harmonic analysis, and the effective value of the 50Hz fundamental current and the 150Hz third harmonic current is calculated. The calculated current measurement result (i.e., the calculated current value) will exceed the preset range (i.e., the selected range of 0-100mA), indicating that the range selected by the data processing module at this time does not match the actual measurement. At this time, the data processing module will select another range (i.e., the large range) as the new preset range and select the 5.64V large range signal corresponding to the large range for harmonic analysis. The calculated current should be within the selected range of 0-10A. Therefore, further harmonic analysis can be performed on the 5.64V large range signal with the length of one fundamental cycle multiple times. The statistical average of the recent current calculation values is accumulated and used as the final ground current measurement result.

[0067] It should be noted that the above examples are only used to understand the present application and do not constitute a limitation on the transformer grounding current measurement method of the present application. More simple transformations based on this technical concept are all within the scope of protection of the present application.

[0068] The above descriptions are only some embodiments of the present application and do not limit the scope of protection. All equivalent structural transformations made using the contents of the present application specification and drawings under the technical concept of the present application, or direct / indirect application in other related technical fields are included in the scope of protection.

Claims

1. A transformer ground current sampling circuit, characterized in that: The transformer ground current sampling circuit includes: A current sensor, configured to generate an induced current signal according to a ground current of a transformer to be measured; A plurality of sampling resistors with different resistance values are sequentially connected in series with the current sensor, and the plurality of sampling resistors are used to simultaneously sample the induced current signal to obtain a plurality of sampled voltage signals; the sampled voltage signals corresponding to different sampling resistors are respectively used for calculating ground currents of different ranges.

2. The transformer ground current sampling circuit according to claim 1, wherein: The plurality of sampling resistors include a first sampling resistor and a second sampling resistor, and the resistance of the first sampling resistor is greater than the resistance of the second sampling resistor.

3. The transformer ground current sampling circuit according to claim 1, wherein: The transformer ground current sampling circuit further includes a plurality of conditioning circuits connected in a one-to-one correspondence with the plurality of sampling resistors; The conditioning circuit is used to amplify and filter the sampling voltage signals at both ends of the corresponding sampling resistor.

4. The transformer ground current sampling circuit according to claim 1, wherein: The transformer ground current sampling circuit further includes a plurality of amplitude limiting circuits connected in parallel with the plurality of sampling resistors in a one-to-one correspondence; The amplitude limiting circuit is used to perform amplitude limiting processing on the sampling voltage signal at both ends of the corresponding sampling resistor.

5. A transformer grounding current measuring device, characterized in that: The transformer grounding current measuring device comprises: A current sampling module, comprising a plurality of sampling resistors with different resistance values, a plurality of conditioning circuits and a plurality of amplitude limiting circuits; The plurality of sampling resistors are used to simultaneously sample the induced current signal to obtain a plurality of sampled voltage signals; the sampled voltage signals corresponding to different sampling resistors are respectively used to calculate ground currents of different ranges; the plurality of conditioning circuits are connected to the plurality of sampling resistors in a one-to-one correspondence, and the conditioning circuits are used to amplify and filter the sampled voltage signals across the corresponding sampling resistors; the plurality of limiting circuits are connected to the plurality of sampling resistors in a one-to-one correspondence in parallel, and the limiting circuits are used to limit the sampled voltage signals across the corresponding sampling resistors; an analog-to-digital conversion module connected to the plurality of conditioning circuits, and configured to convert the processed plurality of sampled voltage signals into corresponding digital signals; The data processing module is connected to the analog-to-digital conversion module and is used to perform harmonic calculation on the multiple digital signals to obtain ground current measurement results.

6. A transformer grounding current measurement system, characterized in that: The transformer grounding current measurement system comprises: The transformer grounding current measuring device according to claim 5; and The current sensor is connected to the current sampling module of the transformer grounding current measuring device through a two-core wire, and is used to generate an induced current signal according to the grounding current of the transformer to be measured and transmit the induced current signal to the current sampling module.

7. The transformer grounding current measurement system according to claim 6, wherein: The transformer grounding current measurement system comprises: a first current sensor, the first current sensor being configured as a core current sensor, the core current sensor being disposed at a core grounding wire of the transformer to be measured, and being configured to generate a first induced current signal according to a core grounding current of the transformer to be measured; a second current sensor, the second current sensor being configured as a clamp current sensor, the clamp current sensor being disposed on a clamp grounding wire of the transformer to be measured, and being configured to generate a second induced current signal according to a clamp grounding current of the transformer to be measured; a first current sampling module connected to the first current sensor; The second current sampling module is connected to the second current sensor.

8. A transformer grounding current measurement method, characterized in that: For the transformer grounding current measuring device according to claim 5, the transformer grounding current measuring method comprises: The ground current signals of different ranges are sampled through the current sampling module; The sampling voltage signals at both ends of each sampling resistor are converted into corresponding digital signals through the analog-to-digital conversion module; The data processing module performs harmonic calculation on the plurality of digital signals to obtain a ground current measurement result.

9. The transformer grounding current measurement method according to claim 8, wherein: The step of performing harmonic calculation on the plurality of digital signals by a data processing module to obtain a ground current measurement result comprises: Determine a first target digital signal from the plurality of digital signals; performing harmonic calculation on the first target digital signal to obtain a first initial current measurement result; When the first initial current measurement result is within a preset range, performing harmonic calculation on the first target digital signal having a fundamental wave cycle length multiple times to obtain multiple first current measurement results; the preset range is the range corresponding to the first target digital signal; determining the ground current measurement result based on an average of a plurality of the first current measurement results; If the first initial current measurement result is not within the preset range, a first target digital signal is re-determined from the remaining digital signals, and the process returns to the step of performing harmonic calculation on the first target digital signal to obtain the first initial current measurement result until the first initial current measurement result is within the range corresponding to the first target digital signal.

10. The transformer grounding current measurement method according to claim 8, wherein: The step of performing harmonic calculation on the plurality of digital signals by a data processing module to obtain a ground current measurement result comprises: Performing harmonic calculation on the plurality of digital signals to obtain a plurality of second initial current measurement results respectively corresponding to the plurality of digital signals; determining a second target digital signal from the plurality of digital signals based on the plurality of second initial current measurement results; performing harmonic calculations on the second target digital signal having a fundamental wave cycle length multiple times to obtain multiple second current measurement results; The ground current measurement is determined based on an average of a plurality of the second current measurements.

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