Function switching device for transformer testing and testing system thereof

Abstract

The application discloses a function switching device for transformer testing and a testing system thereof, relates to the technical field of transformer testing, and aims to solve the problem of low testing efficiency, set a switching time reference by acquiring transformer capacity information, detect the number of closed relays and loop resistance of a testing node, analyze resistance fluctuation index and loop harmonic characteristics in combination with historical loop resistance data, correct the switching time reference, detect three-phase winding current to generate a current balance index to evaluate a fault risk level, screen and mark the testing node according to the fault risk level, and test the marked testing node based on the corrected switching time reference after the current testing node completes the testing, so that the intelligent selection of the transformer testing sequence is realized, the testing efficiency is improved, and the electrical state stability and testing precision of each testing node are ensured.

Description

Technical Field

[0001] This invention relates to the field of transformer testing technology, and more specifically, to a function switching device and testing system for transformer testing. Background Technology

[0002] As a key piece of equipment in the power system, the operating status of transformers directly affects the stability and security of the power system. During the factory inspection, operation and maintenance, and condition assessment of transformers, various electrical performance tests are required, such as loop resistance testing, capacity matching testing, and three-phase current balance testing. Most existing transformer testing methods rely on fixed testing procedures, that is, testing each test node one by one according to a preset sequence, and then performing manual or semi-automatic analysis based on the test data.

[0003] The existing technology has the following shortcomings:

[0004] Currently, existing technologies use a fixed testing switching time base, which cannot comprehensively assess potential risks of node failures, optimize the node detection sequence in real time, or provide a dynamic switching mechanism based on capacity information and loop resistance characteristics. This results in low testing efficiency and insufficient testing safety. Therefore, a functional switching device and its testing system for transformer testing are proposed.

[0005] The information disclosed in the background section is only intended to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a function switching device and its testing system for transformer testing. By using dynamic adjustment of the switching time reference, assessing fault risk based on current balance and loop impedance analysis, and intelligently screening the nodes to be tested, the device achieves automatic optimization of the test sequence and efficient detection, thereby solving the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a function switching test system for transformer testing, comprising a data acquisition module, a benchmark correction module, a risk assessment module, and a node screening module, the functions of which are as follows:

[0008] The data acquisition module is used to obtain the transformer's capacity information, set the switching time reference based on the capacity information, detect the number of closed relays and the loop resistance of the current test node, and transmit them to the reference correction module.

[0009] The benchmark correction module is used to retrieve the loop resistance range from the historical test database, analyze the resistance fluctuation index in combination with the loop resistance, analyze the loop harmony characteristics by combining the resistance fluctuation index and the number of closed relays, correct the switching time benchmark based on the loop harmony characteristics, and then pass the corrected switching time benchmark into the node filtering module.

[0010] The risk assessment module detects the current signal of the three-phase winding of the transformer and generates a current balance index. The current balance index is used to assess the fault risk level of the transformer and then transmitted to the node screening module.

[0011] The node filtering module is used to filter and mark the nodes to be tested after receiving the fault risk level. After the current test node completes the test, the marked nodes to be tested are tested based on the corrected switching time base.

[0012] In a preferred embodiment, in the data acquisition module, the transformer capacity information is obtained through the transformer management database, and the capacity information is the rated capacity of the transformer.

[0013] Obtain capacity information for different transformers, group transformers with the same capacity information into the same group, and retrieve the switching time reference for different capacity information through the manufacturer's specification scheme.

[0014] In a preferred embodiment, the number of closed relays at the current test node is obtained in the data acquisition module through a relay status detection device.

[0015] The voltage and current of the current test node are obtained through a loop measurement device, and the ratio of voltage to current is used as the loop resistance.

[0016] In a preferred embodiment, the loop resistance range of the historical test database is retrieved in the reference correction module;

[0017] The upper and lower limits of the loop resistance range are used as the first and second resistance references, respectively.

[0018] The average value of the first and second resistor references is taken as the center value of the resistance interval, and the absolute value of the difference between the first and second resistor references is divided by 2 to obtain the radius of the resistance interval.

[0019] The resistance fluctuation index is obtained by taking the absolute value of the difference between the loop resistance and the center value of the resistance interval, and then dividing the result by the radius of the resistance interval.

[0020] In a preferred embodiment, in the benchmark correction module, the number of closed relays and the resistance fluctuation index are standardized respectively, and the loop harmony characteristics are calculated by combining the number of closed relays and the resistance fluctuation index.

[0021] The ratio of the loop harmonic feature to the preset loop feature threshold is used as the correction ratio;

[0022] The product of the correction ratio and the switching time base is used as the corrected switching time base.

[0023] In a preferred embodiment, in the risk assessment module, current signals of the three-phase windings of the transformer are collected by current sensors and defined sequentially as the first phase current, the second phase current, and the third phase current.

[0024] The average value of the three-phase current is obtained by averaging the three-phase current signals.

[0025] The deviation of each phase current from the average three-phase current is calculated based on the average three-phase current.

[0026] The deviation was normalized using the root mean square method to obtain the current balance index.

[0027] In a preferred embodiment, in the risk assessment module, when the current balance index is less than or equal to the first current balance threshold, the fault risk level of the transformer is determined to be low risk level.

[0028] When the current balance index is greater than the first current balance threshold and less than or equal to the second current balance threshold, the fault risk level of the transformer is determined to be medium risk level.

[0029] When the current balance index is greater than the second current balance threshold, the transformer's fault risk level is determined to be high risk level.

[0030] In a preferred embodiment, the node screening module filters and marks the nodes to be tested based on their fault risk level:

[0031] Each fault risk level is mapped to a node under test, with low-risk, medium-risk, and high-risk levels corresponding to different nodes under test.

[0032] By comparing the current fault risk level of the transformer with the preset mapping table, the nodes to be tested corresponding to the fault risk level are selected and marked.

[0033] In a preferred embodiment, in the node filtering module, the nodes to be tested are included in the test queue according to the marking order;

[0034] After the current test node completes the test, start the switching time base timing to ensure that the loop state reaches stability within the specified recovery time;

[0035] After the revised switching time base is completed, the nodes under test are triggered to enter the test process according to the marked order.

[0036] A function switching device for transformer testing includes a data acquisition device, a relay status detection device, a loop measurement device, a reference correction device, a current sensor device, a risk assessment device, a node screening device, and a switching control device.

[0037] The functions of each device are as follows:

[0038] Data acquisition device: acquires transformer capacity information, sets initial switching time reference, and acquires the number of closed relays and loop resistance data of the current test node;

[0039] Relay status detection device: detects the closed state of relays in the current test node and obtains the number of closed relays;

[0040] Loop measurement device: Connects to the measurement port of the test node, collects voltage and current signals, and calculates the loop resistance;

[0041] Reference correction device: retrieves the loop resistance range from the historical test database, calculates the resistance fluctuation index, generates loop harmony characteristics, and corrects the switching time reference;

[0042] Current sensor device: installed in the output circuit of the three-phase winding of the transformer to collect the current signal of each phase winding;

[0043] Risk assessment device: Calculates the current balance index to assess the failure risk level of the transformer;

[0044] Node screening device: Screens and marks nodes to be tested according to their fault risk level, and establishes a test queue;

[0045] Switching control device: Based on the modified switching time base, it controls the switching sequence of test nodes.

[0046] The technical effects and advantages of this invention are as follows:

[0047] This invention obtains transformer capacity information to set a switching time reference, detects the number of closed relays and loop resistance at the current test node, retrieves the loop resistance range from the historical test database, analyzes the resistance fluctuation index in combination with the loop resistance, analyzes the loop harmony characteristics by combining the resistance fluctuation index and the number of closed relays, corrects the switching time reference based on the loop harmony characteristics, detects the current signal of the transformer's three-phase windings and generates a current balance index to assess the transformer's fault risk level, filters and marks the test nodes according to the fault risk level, and performs test processing on the marked test nodes based on the corrected switching time reference after the current test node completes the test. This achieves intelligent selection of transformer test sequence, improves test efficiency, and ensures the electrical stability and test accuracy of each test node. Attached Figure Description

[0048] Figure 1 This is a flowchart illustrating the implementation of a function switching test system for transformer testing according to the present invention.

[0049] Figure 2 This is a schematic diagram of a function switching test system for transformer testing according to the present invention.

[0050] Figure 3 This is a schematic diagram of a function switching device for transformer testing according to the present invention. Detailed Implementation

[0051] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] This invention sets a switching time reference by acquiring transformer capacity information, detecting the number of closed relays and loop resistance at the current test node, retrieving the loop resistance range from the historical test database, analyzing the resistance fluctuation index in combination with the loop resistance, analyzing the loop harmony characteristics by combining the resistance fluctuation index and the number of closed relays, correcting the switching time reference based on the loop harmony characteristics, detecting the current signal of the transformer's three-phase windings and generating a current balance index to assess the transformer's fault risk level, screening and marking the test nodes according to the fault risk level, and performing test processing on the marked test nodes based on the corrected switching time reference after the current test node completes the test, thus realizing intelligent selection of transformer test sequence.

[0053] Example 1: A functional test system for transformer testing, such as... Figure 1 and Figure 2 As shown, it includes a data acquisition module, a benchmark correction module, a risk assessment module, and a node selection module, with each module connected by electrical signals.

[0054] The functions of each module are as follows:

[0055] The data acquisition module is used to obtain the transformer's capacity information, set the switching time reference based on the capacity information, detect the number of closed relays and the loop resistance of the current test node, and transmit them to the reference correction module.

[0056] The benchmark correction module is used to retrieve the loop resistance range from the historical test database, analyze the resistance fluctuation index in combination with the loop resistance, analyze the loop harmony characteristics by combining the resistance fluctuation index and the number of closed relays, correct the switching time benchmark based on the loop harmony characteristics, and then pass the corrected switching time benchmark into the node filtering module.

[0057] The risk assessment module detects the current signal of the three-phase winding of the transformer and generates a current balance index. The current balance index is used to assess the fault risk level of the transformer and then transmitted to the node screening module.

[0058] The node filtering module is used to filter and mark the nodes to be tested after receiving the fault risk level. After the current test node completes the test, the marked nodes to be tested are tested based on the corrected switching time base.

[0059] The specific implementation is as follows:

[0060] In the data acquisition module, the transformer capacity information is obtained through the transformer management database. The capacity information is the rated capacity of the transformer, which represents the power that the transformer can withstand under rated conditions.

[0061] It should be explained that the transformer management database is a database used to record and manage basic information, manufacturing specifications and historical operation and maintenance data of transformer equipment, and can obtain transformer capacity information.

[0062] The switching time reference refers to the time interval during which different nodes are tested to ensure the stability of the relay and circuit states;

[0063] The capacity information of different transformers is obtained through the transformer management database. Transformers with the same capacity information are grouped together. The switching time reference for different capacity information is retrieved through the manufacturer's specification scheme, and the corresponding switching time reference is set for each group of transformers.

[0064] It should be explained that the switching time reference refers to the waiting time required after the current test node is completed to ensure that the relay contact arc is extinguished and the current fluctuation returns to a stable state. It can be obtained through the manufacturer's specification plan. The manufacturer's specification plan refers to the technical documents provided by the transformer manufacturer, which contain the switching time reference corresponding to different capacity information.

[0065] The larger the rated capacity of a transformer, the higher the electrical energy impact that the internal windings and insulation structure of the transformer can withstand. In order to ensure the stability of relay switching and the safety of circuit status, the switching time reference is longer.

[0066] Test nodes refer to the test items performed during transformer testing. Each test node corresponds to an independent test item. For example, test nodes include winding DC resistance testing, no-load or low-load voltage testing, etc. By switching between different test nodes, a safety assessment of the transformer's electrical condition can be achieved.

[0067] The number of closed relays at the current test node is obtained through a relay status detection device. The number of closed relays refers to the number of relays in the current test node whose relay switches are in the closed state.

[0068] The voltage and current of the current test node are obtained through a loop measurement device, and the ratio of voltage to current is used as the loop resistance.

[0069] When the current test node is a DC test, the ratio of voltage to current is used as the loop resistance; when the current test node is an AC measurement node, the measured ratio of voltage to current is used as the total impedance, and the loop resistance is extracted from the real part of the total impedance.

[0070] It should be explained that the relay status detection device obtains the closed state of the relay switch in the current test node by detecting the relay switch status in real time; the loop measurement device obtains the voltage and current of the loop of the measurement node by collecting the voltage and current signals of the node through the measurement port connected to the test node, and uses it to calculate the loop resistance.

[0071] In the benchmark correction module, retrieve the loop resistance range from the historical test database.

[0072] It needs to be explained that the historical test database is a database used to store transformer test results and test information. It records the test parameters of each transformer at different test nodes, including loop resistance, voltage, current, etc. The obtained loop resistance range is a range obtained by statistically analyzing the loop resistance measured by transformers with the same capacity information at the same test node. For example, the upper and lower limits of the loop resistance range are calculated using the mean and standard deviation of the loop resistance in the historical test database.

[0073] The upper and lower limits of the circuit resistance range are used as the first and second resistance references, respectively. The average value of the first and second resistance references is taken as the center value of the resistance range. The absolute value of the difference between the first and second resistance references is divided by 2 to obtain the radius of the resistance range.

[0074] The absolute value of the difference between the loop resistance and the center value of the resistance interval, divided by the radius of the resistance interval, is used as the resistance fluctuation index.

[0075] The resistance fluctuation index is used to quantify the degree to which the loop resistance deviates from the loop resistance range. A resistance fluctuation index between 0 and 1 indicates that the loop resistance is within the loop resistance range. When the resistance fluctuation index is greater than 1, it indicates that the loop resistance is outside the loop resistance range. The larger the resistance fluctuation index, the more obvious the deviation of the electrical state of the current test node.

[0076] After standardizing the number of closed relays and the resistance fluctuation index separately, the loop harmonic characteristics are calculated by combining the number of closed relays and the resistance fluctuation index. ,in, This is the standardized value of the number of closed relays. This is the value after standardization of the resistance fluctuation index. For preset weighting coefficients, It is a harmonic loop characteristic;

[0077] The loop harmony characteristic ranges from 0 to 1. The more closed relays there are at the current test node, the longer each relay takes to switch, and the longer the switching time base. The larger the resistance fluctuation index, the more unstable the electrical state of the current test node, and the greater the loop harmony characteristic.

[0078] The ratio of the loop harmonic feature to the preset loop feature threshold is used as the correction ratio; the product of the correction ratio and the switching time reference is used as the corrected switching time reference.

[0079] The corrected switching time base is passed to the node filtering module.

[0080] When the correction ratio is greater than 1, it indicates that the current node circuit state deviates significantly and the switching time base needs to be extended. When the correction ratio is less than 1, it indicates that the current node circuit state is relatively stable and the switching time base can be shortened accordingly.

[0081] It should be explained that the standardization methods include, but are not limited to, standard linear transformation based on interval scaling, statistical Z-score standardization, or normalization based on nonlinear mapping functions. The specific methods of standardization will not be elaborated upon here. The preset weighting coefficients are used to control the contribution of the number of closed relays and the resistance fluctuation index to the loop harmony characteristics. Their values ​​range from 0 to 1 and can be set based on historical test data. For example, the preset weighting coefficients can be determined by analyzing the relay response time and resistance fluctuation index of different test nodes. The preset loop characteristic thresholds are used to determine whether the electrical state of the current test node deviates from the normal range. These thresholds are set based on historical test results or actual safety requirements. For example, they can be determined by statistical analysis. The circuit harmonic characteristics distribution of transformers with the same capacity information at each test node is calculated. The 90th percentile of the circuit harmonic characteristics is selected as the preset circuit characteristic threshold. The 90th percentile covers the circuit harmonic characteristics under 90% of the operating conditions (only 10% of the operating conditions will exceed this threshold). In specific implementation, the circuit harmonic characteristics of 100 transformers with the same capacity at the same test node are sorted, and the 90th sample value is taken as the circuit characteristic threshold. Based on the principles of mathematical statistics, the percentile method describes the dispersion and central tendency of the overall sample through distribution characteristics. While ensuring that most normal samples are covered, the low-probability extreme samples at the tail of the distribution are marked as anomalies, thus taking into account both reliability and sensitivity to anomaly detection in a statistical sense.

[0082] In the risk assessment module, the three-phase winding current signal of the transformer is detected, and a current balance index is generated based on the detection results. The current balance index is used to assess the fault risk level of the transformer, and the fault risk level is transmitted to the node screening module for further processing.

[0083] Current signals from the three-phase windings of the transformer are acquired using current sensors. These current signals are defined sequentially as the first-phase current, the second-phase current, and the third-phase current. All three-phase current signals are expressed in amperes, reflecting the actual current operating state of each phase winding at the current test node.

[0084] It should be noted that the current sensor is a detection unit installed on the output circuit of the three-phase winding of the transformer, used to collect and convert the actual current flowing through the winding circuit in real time.

[0085] The average value of the three-phase current is calculated by averaging the three-phase current signals. The average value of the three-phase current represents the overall numerical level of the three-phase current and serves as a reference benchmark for current balance analysis.

[0086] After obtaining the average value of the three-phase current, calculate the deviation of each phase current from the average value of the three-phase current;

[0087] To quantify the overall fluctuation of the three-phase current, the root mean square method is used to normalize the deviation, resulting in the current balance index, calculated as follows:

[0088] ;

[0089] in, The current balance index, , and These are the first-phase current, the second-phase current, and the third-phase current, respectively. The current balance index is the average value of the three-phase current. It is a dimensionless value that reflects the degree of imbalance of the three-phase current. The larger the current balance index, the more obvious the difference between the three-phase current and the worse the symmetry of the winding operation. Conversely, the smaller the current balance index, the more balanced the three-phase current.

[0090] It should be noted that the root mean square method is a mathematical method for measuring the degree of deviation of a set of values. Its basic principle is to square the difference between each value and the benchmark value to eliminate the offsetting effect of positive and negative differences, then sum and average all the square results, and finally take the square root as the representation of the overall deviation.

[0091] Based on the current balance index, the fault risk level of the transformer is further classified, and the specific classification logic is as follows:

[0092] When the current balance index is less than or equal to the first current balance threshold, it indicates that the three-phase current is basically balanced, the transformer is operating stably, and the transformer's fault risk level is determined to be low risk level.

[0093] When the current balance index is greater than the first current balance threshold and less than or equal to the second current balance threshold, it indicates that there is a certain deviation in the three-phase current, and the transformer may have slight asymmetry or improper wiring. The fault risk level of the transformer is judged to be medium risk level.

[0094] When the current balance index is greater than the second current balance threshold, it indicates that the three-phase current is seriously unbalanced, and the transformer may have inter-turn short circuit, core fault or serious wiring error. The transformer's fault risk level is judged to be high risk level.

[0095] It should be noted that the first and second current balance thresholds are set based on historical operating data and equipment standard requirements. By statistically analyzing the current imbalance characteristics of typical transformers under normal and fault conditions, the fluctuation range of the current balance index during normal operation and the typical intervals under mild and severe fault conditions are obtained. Based on these statistical results, the boundary between normal and abnormal conditions is used as the first current balance threshold for low and medium risk, and the boundary between mild and severe fault conditions is used as the second current balance threshold for medium and high risk. Specifically, the three-phase current signals of typical transformers under normal and confirmed fault conditions are retrieved to calculate the corresponding current balance index, forming a normal sample set and an abnormal sample set. The mean and standard deviation of the current balance index distribution of the normal sample set are calculated, and the mean plus the standard deviation is taken as the upper limit of the normal range. The mean and standard deviation of the abnormal sample set are calculated, and the standard deviation of the mean minus a preset coefficient is taken as the lower limit of the abnormal range, which can be adjusted according to the transformer's fault sensitivity. When the upper limit of the normal range overlaps with the lower limit of the abnormal range, the median of the overlapping area is taken as the dividing point. When the upper limit of the normal range does not overlap with the lower limit of the abnormal range, the safety gap method is used to calculate the dividing point. , Wherein, K is the safety factor, with a value ranging from 0.2 to 0.5, and is determined according to the dispersion of historical data. For example, when the upper limit of the normal range is 0.8 and the lower limit of the abnormal range is 1.2, K=0.3 is taken to obtain the dividing point of 0.92. The safety gap method is verified by statistics to ensure that the dividing point maintains a reasonable distance from the boundary of the two sets of data.

[0096] The risk assessment module outputs the fault risk level to the node screening module, which then uses this information to make a comprehensive judgment and select nodes based on parameters such as the switching time reference. This ensures that the entire test system can reasonably allocate the test sequence according to the current balance during multi-node scheduling, thereby improving the accuracy and scientific nature of the test.

[0097] In the node screening module, nodes under test are screened and marked based on their fault risk level:

[0098] Each fault risk level is mapped one-to-one with the node under test, that is, low risk level, medium risk level and high risk level correspond to different nodes under test.

[0099] By comparing the current fault risk level of the transformer with the preset mapping table, the nodes to be tested corresponding to the current fault risk level are selected and marked.

[0100] It should be noted that the mapping table is a pre-established database of correspondences between fault risk levels and test nodes, used to configure different fault risk levels with the test nodes that have the highest diagnostic value. Specifically, the test nodes corresponding to low-risk levels are mainly routine verification items, such as winding DC resistance testing or voltage ratio testing, used to confirm the normality of the equipment under basic electrical parameters; the test nodes corresponding to medium-risk levels are specialized testing items for minor anomalies, such as no-load loss testing and short-circuit impedance testing, used to identify potential asymmetrical operation or improper wiring hazards; the test nodes corresponding to high-risk levels are critical test items with the highest fault sensitivity, such as AC withstand voltage testing and partial discharge testing, used to quickly locate potential inter-turn short circuits, insulation defects, or core faults.

[0101] After screening and marking, the nodes under test are included in the test queue according to the marking order. After the current test node completes the test, the marked test nodes are scheduled based on the corrected switching time reference. Specifically, the switching time reference timing is first started to ensure that the loop state reaches stability within the specified recovery time, including conditions such as arc extinction, magnetic field recovery, and temperature equalization. After the corrected switching time reference ends, the test nodes are triggered to enter the test process according to the marking order to ensure that the test nodes operate in a predetermined order under safe and stable loop conditions.

[0102] Through the above process, the nodes to be tested corresponding to each fault risk level can be accurately screened and marked. At the same time, the scheduling is carried out in combination with the corrected switching time base to achieve orderly control of the test system. This optimizes the test sequence while ensuring system safety, thereby improving the efficiency and accuracy of the entire transformer test system.

[0103] Example 2

[0104] A function switching device for transformer testing, such as Figure 3 As shown, it includes a data acquisition device, a relay status detection device, a loop measurement device, a reference correction device, a current sensor device, a risk assessment device, a node screening device, and a switching control device.

[0105] The functions of each device are as follows:

[0106] Data acquisition device: used to acquire transformer capacity information, set the initial switching time reference based on the capacity information, and acquire the number of closed relays and loop resistance data of the current test node;

[0107] Relay status detection device: Real-time detection of the closed status of relays in the current test node, and acquisition of the number of closed relays;

[0108] Loop measurement device: Connects to the measurement port of the test node, collects voltage and current signals, and calculates the loop resistance;

[0109] Reference correction device: retrieves the loop resistance range from the historical test database, calculates the resistance fluctuation index in combination with the current loop resistance, comprehensively analyzes the number of closed relays and the resistance fluctuation index, generates loop harmony characteristics, and corrects the switching time reference.

[0110] Current sensor device: installed on the output circuit of the three-phase winding of the transformer to collect the current signal of each phase winding in real time;

[0111] Risk assessment device: Calculates the current balance index based on three-phase current signals to assess the fault risk level of the transformer;

[0112] Node screening device: Screens and marks nodes to be tested according to their fault risk level, and establishes a test queue;

[0113] Switching control device: Based on the revised switching time base, it controls the switching sequence of test nodes to ensure that the test process is carried out in a stable state.

[0114] Finally, it should be noted that in this paper, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0115] Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0116] In this document, the singular forms “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that terms such as “comprising / including” or “having” specify the presence of the stated features, integrals, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, integrals, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.

[0117] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The various embodiments can be combined as needed, and the same or similar parts can be referred to each other.

[0118] The above description of the disclosed embodiments will enable those skilled in the art to make or use various modifications to these embodiments. It will be readily apparent to those skilled in the art that the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A function switching test system for transformer testing, characterized in that: It includes a data acquisition module, a baseline correction module, a risk assessment module, and a node selection module. The functions of each module are as follows: The data acquisition module is used to obtain the transformer's capacity information, set the switching time reference based on the capacity information, detect the number of closed relays and the loop resistance of the current test node, and transmit them to the reference correction module. The benchmark correction module is used to retrieve the loop resistance range from the historical test database, analyze the resistance fluctuation index in combination with the loop resistance, analyze the loop harmony characteristics by combining the resistance fluctuation index and the number of closed relays, correct the switching time benchmark based on the loop harmony characteristics, and then pass the corrected switching time benchmark into the node filtering module. In the benchmark correction module, retrieve the loop resistance range from the historical test database; The upper and lower limits of the loop resistance range are used as the first and second resistance references, respectively. The average value of the first and second resistor references is taken as the center value of the resistance interval, and the absolute value of the difference between the first and second resistor references is divided by 2 to obtain the radius of the resistance interval. The absolute value of the difference between the loop resistance and the center value of the resistance interval, divided by the radius of the resistance interval, is used as the resistance fluctuation index. In the benchmark correction module, after standardizing the number of closed relays and the resistance fluctuation index respectively, the loop harmony characteristics are calculated by combining the number of closed relays and the resistance fluctuation index. The ratio of the loop harmonic feature to the preset loop feature threshold is used as the correction ratio; The product of the correction ratio and the switching time base is used as the corrected switching time base. The risk assessment module detects the current signal of the three-phase winding of the transformer and generates a current balance index. The current balance index is used to assess the fault risk level of the transformer and then transmitted to the node screening module. In the risk assessment module, current signals of the three-phase windings of the transformer are collected by current sensors and defined as the first phase current, the second phase current and the third phase current, respectively. The average value of the three-phase current is obtained by averaging the three-phase current signals. The deviation of each phase current from the average three-phase current is calculated based on the average three-phase current. The deviation was normalized using the root mean square method to obtain the current balance index; The node filtering module is used to filter and mark the nodes to be tested after receiving the fault risk level. After the current test node completes the test, the marked nodes to be tested are tested based on the corrected switching time base.

2. The function switching test system for transformer testing according to claim 1, characterized in that: In the data acquisition module, the transformer capacity information is obtained through the transformer management database. The capacity information is the rated capacity of the transformer. Obtain capacity information for different transformers, group transformers with the same capacity information into the same group, and retrieve the switching time reference for different capacity information through the manufacturer's specification scheme.

3. The function switching test system for transformer testing according to claim 2, characterized in that: In the data acquisition module, the number of closed relays at the current test node is obtained through the relay status detection device; The voltage and current of the current test node are obtained through a loop measurement device, and the ratio of voltage to current is used as the loop resistance.

4. The function switching test system for transformer testing according to claim 1, characterized in that: In the risk assessment module, when the current balance index is less than or equal to the first current balance threshold, the transformer's fault risk level is determined to be low risk level. When the current balance index is greater than the first current balance threshold and less than or equal to the second current balance threshold, the fault risk level of the transformer is determined to be medium risk level. When the current balance index is greater than the second current balance threshold, the transformer's fault risk level is determined to be high risk level.

5. The function switching test system for transformer testing according to claim 1, characterized in that: In the node screening module, nodes under test are screened and marked based on their fault risk level: Each fault risk level is mapped to a node under test, with low-risk, medium-risk, and high-risk levels corresponding to different nodes under test. By comparing the current fault risk level of the transformer with the preset mapping table, the nodes to be tested corresponding to the fault risk level are selected and marked.

6. A function switching test system for transformer testing according to claim 5, characterized in that: In the node filtering module, the nodes to be tested are included in the test queue according to the marked order; After the current test node completes the test, start the switching time base timing to ensure that the loop state reaches stability within the specified recovery time; After the revised switching time base is completed, the nodes under test are triggered to enter the test process according to the marked order.

7. A function switching device for transformer testing, used to implement the function switching test system for transformer testing as described in any one of claims 1-6, characterized in that: It includes data acquisition devices, relay status detection devices, loop measurement devices, reference correction devices, current sensor devices, risk assessment devices, node screening devices, and switching control devices. The functions of each device are as follows: Data acquisition device: acquires transformer capacity information, sets initial switching time reference, and acquires the number of closed relays and loop resistance data of the current test node; Relay status detection device: detects the closed state of relays in the current test node and obtains the number of closed relays; Loop measurement device: Connects to the measurement port of the test node, collects voltage and current signals, and calculates the loop resistance; Reference correction device: retrieves the loop resistance range from the historical test database, calculates the resistance fluctuation index, generates loop harmony characteristics, and corrects the switching time reference; Current sensor device: installed in the output circuit of the three-phase winding of the transformer to collect the current signal of each phase winding; Risk assessment device: Calculates the current balance index to assess the failure risk level of the transformer; Node screening device: Screens and marks nodes to be tested according to their fault risk level, and establishes a test queue; Switching control device: Based on the modified switching time base, it controls the switching sequence of test nodes.

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