A method and device for phase-to-phase differential protection of a three-phase split transformer

Abstract

The application provides a phase-to-phase differential protection method and device for a three-phase split transformer, comprising: monitoring phase-to-phase amplitude differential and phase-to-phase phase differential of each voltage grade side of the three-phase split transformer to obtain a phase-to-phase amplitude and phase differential signal; if the duration of the phase-to-phase amplitude and phase differential signal exceeds a time threshold, judging the correlation between high-frequency current signals of two single-phase transformers that occur fault at the fault voltage grade according to fault phase-to-phase information; if the correlation is lower than a correlation threshold, outputting a voltage grade phase-to-phase differential signal; if any two voltage grade sides of the three voltage grade sides of the three-phase split transformer output the voltage grade phase-to-phase differential signal, starting phase-to-phase differential protection and controlling the three-phase split transformer to exit operation. The application can apply the method of single transformer differential protection to multiple single-phase transformers, and improve the response speed, sensitivity and reliability of the three-phase split transformer protection.

Description

Technical Field

[0001] This application relates to the field of power equipment maintenance, specifically a method and device for phase-to-phase differential protection of a three-phase split transformer. Background Technology

[0002] Transformers are crucial equipment in power systems, and their safe and stable operation is essential for the overall operation of the power system. Effective protection measures must be taken to prevent and reduce transformer failures. Current transformer protection systems consist mainly of differential protection and gas protection, which are limited to a single transformer and cannot provide timely protection for other components in a three-phase split-type transformer, thus hindering the improvement of the sensitivity of three-phase split-type transformer protection.

[0003] Three-phase split-type transformers typically feature high voltage levels and large capacities, and are widely used in ultra-high voltage and extra-high voltage substations, serving as key core equipment. A three-phase split-type transformer consists of three independent single-phase transformers, each with its own windings and core. This structure presents challenges in phase-to-phase differential protection, as it requires ensuring the correct operation of the differential protection for each single-phase transformer unit, along with proper coordination between them.

[0004] Currently, transformer differential protection is used to monitor internal faults in single-phase transformers and does not simultaneously protect other phases of three-phase split-type transformers. Existing transformer phase-to-phase protection focuses on dealing with external phase-to-phase short-circuit faults and is a backup protection measure, making it difficult to quickly respond to internal transformer faults. Therefore, how to utilize the phase-to-phase differences in electrical quantities of three-phase split-type transformers to propose a fast and effective protection method is an urgent problem to be solved.

[0005] This section is intended to provide background or context for the embodiments of the invention set forth in the claims. The description herein is not an admission that it is prior art simply because it is included in this section. Summary of the Invention

[0006] To address the problems in the prior art, this application provides a phase-to-phase differential protection method and device for a three-phase split transformer, which can apply the differential protection method for a single transformer to multiple single-phase transformers, thereby improving the response speed, sensitivity, and reliability of the protection for the three-phase split transformer.

[0007] To solve the above-mentioned technical problems, this application provides the following technical solution:

[0008] In a first aspect, this application provides a phase-to-phase differential protection method for a three-phase split-type transformer, comprising:

[0009] The phase-to-phase amplitude differential and phase-to-phase phase differential of each voltage level side of the three-phase split transformer are monitored to obtain the phase-to-phase amplitude-phase differential signal; wherein, the phase-to-phase amplitude-phase differential signal includes the fault voltage level and fault phase information;

[0010] If the duration of the phase-to-phase amplitude differential signal exceeds the duration threshold, the correlation between the high-frequency current signal spectra of the two single-phase transformers that have failed at the fault voltage level is determined based on the fault phase-to-phase information.

[0011] If the correlation is lower than the correlation threshold, output a phase-to-phase differential signal of the voltage level;

[0012] If it is detected that any two voltage level sides of the three-phase split transformer output the phase-to-phase differential signal of the voltage level, the phase-to-phase differential protection is activated, and the three-phase split transformer is controlled to take off the line of operation.

[0013] Furthermore, the monitoring of phase-to-phase amplitude differential and phase-to-phase phase differential on each voltage level side of the three-phase split transformer to obtain phase-to-phase amplitude and phase differential signals includes:

[0014] The phase-to-phase amplitude differential is monitored on each voltage level side of the three-phase split transformer to obtain the phase-to-phase amplitude differential signal;

[0015] The phase-to-phase differential signal is obtained by monitoring the phase-to-phase differential signal on each voltage level side of the three-phase split transformer.

[0016] For the same phase under the same fault voltage level, if both the phase-to-phase amplitude differential signal and the phase-to-phase phase differential signal are non-zero, the phase-to-phase amplitude differential signal is output as a non-zero value.

[0017] Furthermore, the phase-to-phase amplitude differential of the three-phase split transformer at each voltage level is monitored to obtain the phase-to-phase amplitude differential signal, including:

[0018] Monitor the high-frequency current amplitude of each phase under each voltage level;

[0019] Whether to output the phase-to-phase amplitude differential signal as a non-zero value is determined based on the mean amplitude of the white noise, the standard deviation of the white noise amplitude, and the amplitude of the high-frequency current.

[0020] Furthermore, the phase-to-phase differential of each voltage level side of the three-phase split transformer is monitored to obtain the phase-to-phase differential signal, including:

[0021] Monitor the high-frequency current phasors of each phase at each voltage level;

[0022] Whether to output the interphase phase differential signal as a non-zero value is determined based on the preset critical phase angle and the difference in phase angles of each high-frequency current phasor under the voltage level.

[0023] Furthermore, if the duration of the phase-to-phase amplitude differential signal exceeds a duration threshold, determining the correlation between the high-frequency current signal spectra of the two single-phase transformers that have failed at the fault voltage level based on the fault phase-to-phase information includes:

[0024] Get The time series of high-frequency current signals within a power frequency cycle; where... T It is an integer;

[0025] Perform a Fourier transform on the time series and calculate the spectral energy vectors corresponding to the fault at the fault voltage level; wherein the fault phase corresponds to the phase of the single-phase transformer;

[0026] The correlation between the high-frequency current signal spectra of the two single-phase transformers is calculated based on the corresponding spectral energy vectors of the two faults.

[0027] Furthermore, if it is detected that any two voltage level sides of the three-phase split transformer output the phase-to-phase differential signal of the voltage level, the phase-to-phase differential protection is activated, and the three-phase split transformer is controlled to take off operation, the following steps are included:

[0028] If the high-frequency current between any two phases on a certain voltage level side meets the output conditions of the phase-to-phase differential protection logic, the voltage level side outputs the voltage level phase-to-phase differential signal; wherein, the voltage level phase-to-phase differential signal includes a high-voltage side protection signal, a medium-voltage side protection signal, and a neutral point protection signal;

[0029] If at least two of the high-voltage side protection signal, medium-voltage side protection signal, and neutral point protection signal are detected to be non-zero, the phase-to-phase differential protection is activated, and the three-phase split transformer is controlled to exit operation.

[0030] Secondly, this application provides a phase-to-phase differential protection device for a three-phase split-type transformer, comprising:

[0031] The phase-to-phase differential signal generation unit is used to monitor the phase-to-phase amplitude differential and phase-to-phase phase differential on each voltage level side of the three-phase split transformer to obtain the phase-to-phase amplitude-phase differential signal; wherein, the phase-to-phase amplitude-phase differential signal includes the fault voltage level and fault phase information;

[0032] A differential signal generation unit is used to determine the correlation between the high-frequency current signal spectra of two single-phase transformers that have failed at the fault voltage level, based on the fault phase information, if the duration of the phase-to-phase amplitude-phase differential signal exceeds a duration threshold.

[0033] The correlation determination unit is used to output a voltage level phase differential signal if the correlation is lower than the correlation threshold.

[0034] The differential protection unit is used to activate the phase-to-phase differential protection and control the three-phase split transformer to take it out of operation if it detects that any two voltage level sides of the three voltage level sides of the three-phase split transformer output the phase-to-phase differential signal of the voltage level.

[0035] Furthermore, the phase-to-phase differential signal generation unit includes:

[0036] An amplitude signal generation module is used to monitor the phase-to-phase amplitude differential on each voltage level side of the three-phase split transformer and obtain the phase-to-phase amplitude differential signal.

[0037] The phase signal generation module is used to monitor the phase difference between phases on each voltage level side of the three-phase split transformer and obtain the phase difference signal between phases.

[0038] The phase-to-phase differential signal generation module is used to output a non-zero value for the phase-to-phase amplitude differential signal if both the phase-to-phase amplitude differential signal and the phase-to-phase phase differential signal are non-zero values ​​for the same phase under the same fault voltage level.

[0039] Furthermore, the amplitude signal generation module includes:

[0040] The current amplitude monitoring module is used to monitor the high-frequency current amplitude of each phase under each voltage level.

[0041] An amplitude signal output module is used to determine whether to output the phase-to-phase amplitude differential signal as a non-zero value based on the mean amplitude of the white noise, the standard deviation of the white noise amplitude, and the amplitude of the high-frequency current.

[0042] Furthermore, the phase signal generation module includes:

[0043] The current phasor monitoring module is used to monitor the high-frequency current phasors of each phase under each voltage level.

[0044] The phase signal output module is used to determine whether to output the interphase phase differential signal as a non-zero value based on the preset critical phase angle and the difference in phase angles of each high-frequency current phasor under the voltage level.

[0045] Furthermore, the differential signal generation unit includes:

[0046] The time series acquisition module is used to acquire... The time series of high-frequency current signals within a power frequency cycle; where... T It is an integer;

[0047] An energy vector generation module is used to perform a Fourier transform on the time series and calculate the spectral energy vectors corresponding to the fault at the fault voltage level; wherein the fault phase corresponds to the phase of the single-phase transformer.

[0048] The correlation calculation module is used to calculate the correlation between the high-frequency current signal spectra of the two single-phase transformers based on the corresponding spectral energy vectors of the two faults.

[0049] Furthermore, the differential protection unit includes:

[0050] Each phase differential signal output module is used to output the voltage level phase differential signal if the high-frequency current between any two phases on a certain voltage level side meets the phase differential protection logic output condition; wherein, the voltage level phase differential signal includes a high-voltage side protection signal, a medium-voltage side protection signal, and a neutral point protection signal;

[0051] The protection start-up module is used to activate the phase-to-phase differential protection and control the three-phase split transformer to take off operation if at least two of the high-voltage side protection signal, medium-voltage side protection signal and neutral point protection signal are detected to be non-zero.

[0052] Thirdly, this application provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the phase-to-phase differential protection method for the three-phase split transformer.

[0053] Fourthly, this application provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the phase-to-phase differential protection method for the three-phase split transformer.

[0054] Fifthly, this application provides a computer program product, including a computer program / instructions, which, when executed by a processor, implement the steps of the phase-to-phase differential protection method for the three-phase split transformer.

[0055] To address the problems in the prior art, the phase-to-phase differential protection method and device for three-phase split transformers provided in this application can compare the amplitude, phase, duration, and spectrum information of high-frequency currents on the same voltage level side of the three-phase split transformer, and determine whether there is an internal fault in each phase transformer based on the phase-to-phase imbalance degree of the monitored quantities and the protection action logic. It extends the scope of differential protection from a single transformer to a three-phase split transformer, and since the monitored high-frequency current signals are all located on the same voltage level side, it solves the problem of protection maloperation caused by unbalanced currents on both sides of the transformer. The criteria and logic for initiating phase-to-phase differential protection accurately distinguish between internal faults and external interference in three-phase split transformers by using the amplitude, phase, duration, and spectrum information of high-frequency current. Considering that three-phase split transformers do not share cores and windings, but the high-frequency current still maintains three-phase symmetry during normal operation, the monitoring scope of differential protection is expanded from a single transformer to all three-phase split transformers, which helps improve the response speed and sensitivity of the protection. By comparing high-frequency current differences only when the acquisition equipment is located on the same voltage level side, the unbalanced current problem caused by the inconsistency of current transformer characteristics in traditional differential protection methods is overcome, making the protection method more reliable. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 This is a flowchart of the phase-to-phase differential protection method for a three-phase split transformer in the embodiments of this application;

[0058] Figure 2 This is a flowchart illustrating the process of obtaining the phase-to-phase amplitude differential signal in the embodiments of this application;

[0059] Figure 3 This is a flowchart illustrating the process of obtaining the phase-to-phase amplitude differential signal in the embodiments of this application;

[0060] Figure 4 This is a flowchart illustrating the process of obtaining the phase differential signal between phases in this application embodiment;

[0061] Figure 5 This is a flowchart illustrating the correlation determination process in an embodiment of this application.

[0062] Figure 6 This is a flowchart illustrating the process of controlling the three-phase split transformer to exit operation in an embodiment of this application;

[0063] Figure 7 This is a structural diagram of the phase-to-phase differential protection device for a three-phase split transformer in an embodiment of this application;

[0064] Figure 8 This is a structural diagram of the phase-to-phase differential signal generation unit in an embodiment of this application;

[0065] Figure 9 This is a structural diagram of the amplitude signal generation module in an embodiment of this application;

[0066] Figure 10 This is a structural diagram of the phase signal generation module in an embodiment of this application;

[0067] Figure 11 This is a structural diagram of the differential signal generation unit in the embodiments of this application;

[0068] Figure 12 This is a structural diagram of the differential protection unit in the embodiments of this application;

[0069] Figure 13 This is a schematic diagram of the structure of the electronic device in the embodiments of this application;

[0070] Figure 14 This is a schematic diagram of the phase-to-phase differential protection logic in the embodiments of this application;

[0071] Figure 15 This is a vector diagram of the three-phase high-frequency current in the embodiments of this application;

[0072] Figure 16 This is a schematic diagram of the protection logic on the same voltage level side in the embodiments of this application (taking the high voltage side as an example);

[0073] Figure 17 This is the overall protection logic in the embodiments of this application;

[0074] Figure 18 This is a schematic diagram of the high-frequency current phase-to-phase differential protection wiring for a three-phase split transformer in this application embodiment (taking the high-voltage side as an example). Detailed Implementation

[0075] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but are not intended to limit the present invention.

[0076] The information collected in the technical solution of this application is information and data authorized by the user or fully authorized by all parties. The collection, storage, use, processing, transmission, provision, disclosure and application of the relevant data all comply with the relevant laws, regulations and standards of the relevant countries and regions, necessary confidentiality measures have been taken, and they do not violate public order and good morals. Corresponding operation portals are provided for users to choose to authorize or refuse.

[0077] Provide users with corresponding operation entry points, allowing them to choose to agree to or reject the automated decision results; if the user chooses to reject, the process will proceed to the expert decision-making process.

[0078] In one embodiment, see Figure 1 In order to apply the differential protection method for a single transformer to multiple single-phase transformers and improve the response speed, sensitivity, and reliability of protection for three-phase split transformers, this application proposes a phase-to-phase differential protection method for three-phase split transformers, including:

[0079] S101: Monitor the phase-to-phase amplitude differential and phase-to-phase phase differential on each voltage level side of the three-phase split transformer to obtain the phase-to-phase amplitude-phase differential signal; wherein, the phase-to-phase amplitude-phase differential signal includes the fault voltage level and fault phase information;

[0080] S102: If the duration of the phase-to-phase amplitude differential signal exceeds the duration threshold, the correlation between the high-frequency current signal spectra of the two single-phase transformers that have failed at the fault voltage level is determined based on the fault phase-to-phase information.

[0081] S103: If the correlation is lower than the correlation threshold, output a voltage level phase differential signal;

[0082] S104: If it is detected that any two voltage level sides of the three-phase split transformer output the phase-to-phase differential signal of the voltage level, the phase-to-phase differential protection is activated, and the three-phase split transformer is controlled to take off the operation.

[0083] It is understandable that differential protection is based on Kirchhoff's current law, which states that the sum of the currents flowing into a node equals the sum of the currents flowing out of the node. During normal operation of a transformer, the primary and secondary currents are balanced; however, when an internal short-circuit fault occurs, the fault current disrupts this balance. The differential protection device triggers its operation upon detecting this current imbalance. However, due to the non-uniform characteristics of current transformers, an unbalanced current will flow through the differential circuit. If this unbalanced current is too large, it may cause the differential protection to malfunction.

[0084] Transformer phase-to-phase protection refers to the maintenance of a balance between phase voltage and current within a certain range under normal transformer operation. If an internal anomaly occurs, it can lead to an imbalance in phase current and voltage. In this case, the phase-to-phase protection device will promptly disconnect the faulty phase to protect the safe operation of the transformer. Phase-to-phase protection features fast response, high sensitivity, and high reliability, and is suitable for protecting large power equipment such as three-phase split-type transformers.

[0085] To address the limitations of existing transformer differential protection methods, such as limited protection range and susceptibility to malfunction due to unbalanced current, this application proposes a phase-to-phase differential protection method for three-phase split-type transformers. This method applies the concept of single-transformer differential protection to multiple single-phase transformers, improving the response speed, sensitivity, and reliability of three-phase split-type transformer protection. In this embodiment, bushing current transformers and high-frequency current transformers are used to simultaneously acquire high-frequency current signals from the same voltage level side of the three-phase split-type transformer, within a frequency range of 1-100MHz. The method uses the significant differences in phase-to-phase characteristics of the signals during internal transformer faults, coupled with the generally similar impact of external interference on each single-phase transformer, as protection action criteria. Combined with protection logic, this achieves timely protection for the three-phase split-type transformer.

[0086] As can be seen from the above description, the phase-to-phase differential protection method for three-phase split transformers provided in this application can compare the amplitude, phase, duration, and spectrum information of high-frequency currents on the same voltage level side of the three-phase split transformer, and determine whether there is an internal fault in each phase transformer based on the phase-to-phase imbalance degree of the monitored quantities and the protection action logic. It extends the scope of differential protection from a single transformer to a three-phase split transformer. At the same time, since the monitored high-frequency current signals are all located on the same voltage level side, it solves the problem of protection maloperation caused by unbalanced currents on both sides of the transformer. The criteria and logic for initiating phase-to-phase differential protection accurately distinguish between internal faults and external interference in three-phase split transformers by using the amplitude, phase, duration, and spectrum information of high-frequency current. Considering that three-phase split transformers do not share cores and windings, but the high-frequency current still maintains three-phase symmetry during normal operation, the monitoring scope of differential protection is expanded from a single transformer to all three-phase split transformers, which helps improve the response speed and sensitivity of the protection. By comparing high-frequency current differences only when the acquisition equipment is located on the same voltage level side, the unbalanced current problem caused by the inconsistency of current transformer characteristics in traditional differential protection methods is overcome, making the protection method more reliable.

[0087] In one embodiment, see Figure 2 The monitoring of phase-to-phase amplitude differential and phase-to-phase differential on each voltage level side of the three-phase split transformer to obtain phase-to-phase amplitude and phase differential signals includes:

[0088] S201: Monitor the phase-to-phase amplitude differential on each voltage level side of the three-phase split transformer to obtain the phase-to-phase amplitude differential signal; specifically, see... Figure 3 The phase-to-phase amplitude differential of the three-phase split transformer at each voltage level is monitored to obtain the phase-to-phase amplitude differential signal, including: S301: monitoring the high-frequency current amplitude of each phase at each voltage level; S302: determining whether to output the phase-to-phase amplitude differential signal as a non-zero value based on the mean amplitude of white noise, the standard deviation of white noise amplitude and the high-frequency current amplitude.

[0089] It is understandable that the phase-to-phase differential protection logic is configured as follows: Figure 14 As shown, this includes phase-to-phase amplitude differential, phase-to-phase phase differential, duration judgment, and spectral correlation analysis. Among these, phase-to-phase amplitude differential and phase-to-phase phase differential are the basic conditions for phase-to-phase differential protection to take effect; duration judgment will only be initiated when both are simultaneously met. If the duration for which both phase-to-phase amplitude differential and phase-to-phase phase differential are simultaneously effective meets the duration judgment conditions, spectral correlation analysis is performed. If the correlation analysis passes, a phase-to-phase differential protection signal is issued.

[0090] The phase amplitude differential is implemented as follows:

[0091] Let the maximum high-frequency current of a three-phase split-type transformer at the same voltage level and at the same moment be denoted as . I A , I B , I C During normal transformer operation, the acquired signal has a small amplitude, known as background noise, which is usually maintained within a certain range and can be considered white noise. Assume this white noise follows a normal distribution with a mean of [value missing]. μ The standard deviation is σ Then according to "3" σ "Principles", amplitude and μ The deviation is in 3 σ The above conditions are considered abnormal. The prerequisites for activating phase-to-phase amplitude differential protection are:

[0092] | I i - μ | > 3 σ , i = A, B, C

[0093] When the transformer is operating normally or subjected to external interference I A , I B , I CThe values ​​should be relatively close, and the degree of phase imbalance should be low. When one of the transformers experiences an internal fault, a faulty branch is added to that transformer, and the high-frequency current amplitude will increase significantly, showing a clear difference from that of a normal transformer.

[0094] Therefore, taking phase A and phase B as an example, if the following conditions are met:

[0095] max{ I A , I B} > K m min{ I A , I B}

[0096] Then the phase-to-phase amplitude differential protection between phases A and B will be activated. In the formula... K m This is the amplitude coefficient, typically in the range of 1.1 to 1.2. The same principle applies to phases B and C, and phases C and A, and so on; further details will not be provided.

[0097] S202: Monitor the phase-to-phase differential on each voltage level side of the three-phase split transformer to obtain the phase-to-phase differential signal; specifically, see... Figure 4 The phase-to-phase differential of the three-phase split transformer at each voltage level is monitored to obtain the phase-to-phase differential signal, including: S401: monitoring the high-frequency current phasor of each phase at each voltage level; S402: determining whether to output the phase-to-phase differential signal as a non-zero value based on the preset critical phase angle and the difference in phase angle between the high-frequency current phasors at each voltage level.

[0098] It is understandable that the phase differential between phases is implemented as follows:

[0099] Let the phasors of the three-phase high-frequency currents A, B, and C be... When the transformer is operating normally or subjected to external interference, The phase relationship between them remains unchanged. If an internal fault occurs in the transformer, the phase of the high-frequency current phasor difference will change.

[0100] Taking phase A and phase B as examples, see Figure 15 As shown, with I A , I B Significant growth The phase angle will vary between 90° and 150°, corresponding to an advance. The angle range is 0° to 60°. The activation condition for interphase phase differential is:

[0101]

[0102] In the formula θ The critical angle for starting phase differential is typically in the range of 5° to 10°.

[0103] in, Figure 15 The left diagram corresponds to "normal conditions or external interference", the middle diagram corresponds to "internal fault of phase A transformer", and the right diagram corresponds to "internal fault of phase B transformer".

[0104] The same logic applies to phases B and C, C and A, and so on, without further explanation.

[0105] S203: For the same phase under the same fault voltage level, if both the phase-to-phase amplitude differential signal and the phase-to-phase phase differential signal are non-zero, the phase-to-phase amplitude differential signal is output as a non-zero value.

[0106] It is understandable that phase-to-phase amplitude differential and phase-to-phase phase differential are the basic conditions for phase-to-phase differential protection to take effect. Only when they are both established (both phase-to-phase amplitude differential signal and phase-to-phase phase differential signal are non-zero values) will the phase-to-phase amplitude differential signal be output as non-zero value, and the duration judgment will be initiated.

[0107] As can be seen from the above description, the phase-to-phase differential protection method for a three-phase split transformer provided in this application can monitor the phase-to-phase amplitude differential and phase-to-phase differential on each voltage level side of the three-phase split transformer, and obtain the phase-to-phase amplitude and phase differential signal.

[0108] In one embodiment, see Figure 5 If the duration of the phase-to-phase amplitude differential signal exceeds a duration threshold, the correlation between the high-frequency current signal spectra of the two single-phase transformers that have failed at the fault voltage level is determined based on the fault phase-to-phase information, including:

[0109] S501: Acquisition The time series of high-frequency current signals within a power frequency cycle; where... T It is an integer;

[0110] S502: Perform a Fourier transform on the time series and calculate the spectral energy vectors corresponding to the fault at the fault voltage level; wherein the fault phase corresponds to the phase of the single-phase transformer;

[0111] S503: Calculate the correlation between the high-frequency current signal spectra of the two single-phase transformers based on the corresponding spectral energy vectors of the two faults.

[0112] Understandably, the next step is to determine the duration. Due to the complexity of the operating environment, the data acquisition device frequently receives intermittent pulses with short durations and high amplitudes. Most of these intermittent pulses are external interference signals and will not seriously affect the transformer. Therefore, a duration determination step should be included to avoid frequent operation of the protection system and potential malfunctions.

[0113] The condition for triggering the duration judgment is: observation. T The number of power frequency cycles that simultaneously meet the start-up conditions for phase-to-phase amplitude differential and phase-to-phase differential within a given power frequency cycle. When more than 80% of the power frequency cycles are detected to meet the relevant requirements, it indicates that the fault has strong continuity, and signals should continue to be output to the protection system.

[0114] After determining the duration, a spectral correlation analysis is performed. The specific steps are as follows:

[0115] Fault current introduces numerous high-order harmonics, resulting in multiple peak intervals across the entire frequency band and altering the spectral composition of the high-frequency current signal. The presence of an abnormal fault can be determined by comparing the correlation between the spectra of the high-frequency current signals from two single-phase transformers.

[0116] Based on satisfying the duration judgment, record T The high-frequency current signal within one power frequency cycle is a time series. , This refers to the signal length. To improve processing speed, in... y [ t The trailing zeros of the symbol make the signal length a power of 2 or higher. ,in This is the floor function. In this case, the number of zeros padded is 2. p - N Let the zero-padding time series be . y 0[ t 0], t 0 = 1, 2, …, 2 p .

[0117] y 0[ t The Fast Fourier Transform of [0] is:

[0118]

[0119] in, ,for One of the secondary unit roots.

[0120] Due to the symmetry of the discrete Fourier transform, only... Y [ k The first half of the data, at this point the range of the sequence number is... .Will Divide into 2 equal parts in order. q share, Each of these data sets is... The sum of squares of all elements is calculated after taking the modulus of the above data to obtain the signal energy of this frequency band:

[0121]

[0122] Arranged in order E j This forms the spectral energy vector of the high-frequency current signal. .

[0123] Let the spectral energy vectors of the three-phase split transformer be respectively... E A , E B , E C Taking a transformer with phases A and B as an example, the correlation coefficient between the energy vector of phase A and the energy vector of phase B is... r AB :

[0124]

[0125] In the formula They are respectively E A , E B The average value of each element in the spectrum. The condition for spectral correlation analysis to hold is:

[0126]

[0127] In the formula, K r The correlation coefficient threshold is typically in the range of 0.3 to 0.5. At this threshold, the correlation and similarity between the spectral energy distribution characteristics of transformer A and transformer B are weak, suggesting that one of the transformers, A or B, has experienced an anomaly.

[0128] The same logic applies to phases B and C, C and A, and so on, without further explanation.

[0129] As can be seen from the above description, the phase-to-phase differential protection method for a three-phase split transformer provided in this application can determine the correlation between the high-frequency current signal spectra of two single-phase transformers that have failed at the fault voltage level based on the fault phase information if the duration of the phase-to-phase amplitude phase differential signal exceeds the duration threshold.

[0130] In one embodiment, see Figure 6If it is detected that any two voltage level sides of the three-phase split transformer output the phase-to-phase differential signal of the voltage level, the phase-to-phase differential protection is activated, and the three-phase split transformer is controlled to take off operation, including:

[0131] S601: If the high-frequency current between any two phases on a certain voltage level side meets the output condition of the phase-to-phase differential protection logic, the voltage level side outputs the voltage level phase-to-phase differential signal; wherein, the voltage level phase-to-phase differential signal includes a high-voltage side protection signal, a medium-voltage side protection signal, and a neutral point protection signal;

[0132] S602: If at least two of the high-voltage side protection signal, medium-voltage side protection signal and neutral point protection signal are detected to be non-zero, the phase-to-phase differential protection is activated and the three-phase split transformer is controlled to take off the line of operation.

[0133] Understandably, the protection logic on the same voltage level side is as follows:

[0134] When the high-frequency current between any two phases on a certain voltage level side meets the output condition of the phase-to-phase differential protection logic, the protection device for that voltage level issues a protection signal. For example, on the high-voltage side, see [link to relevant documentation]. Figure 16 As shown, any two phases AB, AC, or BC on the high-voltage side will send a phase-to-phase differential protection signal, causing the protection device on the high-voltage side to output a protection signal. In this invention, the protection device monitors the high-frequency current located on the high-voltage side, the medium-voltage side, and the neutral point (for a three-phase split transformer without a medium-voltage side, only the high-voltage side and the neutral point need to be monitored).

[0135] The overall protection logic of this application embodiment is as follows:

[0136] If protection devices on at least two voltage level sides issue protection signals (for three-phase split transformers without a medium-voltage side, protection devices on both the high-voltage side and the neutral point need to issue protection signals simultaneously), the protection system issues a protection trip command, causing the three-phase split transformer to be taken out of operation. See [link to relevant documentation]. Figure 17 As shown (taking a three-phase split transformer with a medium-voltage side as an example).

[0137] Taking the high-voltage side of a three-phase split-type double-winding non-autotransformer as an example, see the schematic diagram of the phase-to-phase differential protection wiring. Figure 18 As shown. Figure 18 In the diagram, TA1, TA2, and TA3 represent the high-frequency current acquisition devices on the high-voltage side of single-phase transformers A, B, and C, respectively. The differential relay protection device is connected to the output circuit of the two-phase high-frequency current acquisition device on the high-voltage side, recording information such as the amplitude, phase, and spectrum of the corresponding two-phase high-frequency current.

[0138] In summary, this invention proposes a phase-to-phase differential protection method for a three-phase split-type transformer. This method utilizes the differences in amplitude, phase, and spectrum of high-frequency current signals during internal faults to achieve full-range protection for the three-phase split-type transformer. It avoids potential unbalanced current problems caused by the characteristics of current transformers, thus helping to ensure the safe operation of the three-phase split-type transformer.

[0139] Based on the same inventive concept, this application also provides a phase-to-phase differential protection device for a three-phase split-type transformer, which can be used to implement the method described in the above embodiments, as described in the following embodiments. Since the principle of solving the problem using the phase-to-phase differential protection device for a three-phase split-type transformer is similar to that of the phase-to-phase differential protection method for a three-phase split-type transformer, the implementation of the phase-to-phase differential protection device for a three-phase split-type transformer can refer to the implementation of the method based on software performance benchmarks; repeated details will not be elaborated further. As used below, the terms "unit" or "module" can refer to a combination of software and / or hardware that performs a predetermined function. Although the system described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0140] In one embodiment, see Figure 7 In order to apply the differential protection method for a single transformer to multiple single-phase transformers and improve the response speed, sensitivity and reliability of the protection for three-phase split transformers, this application provides a phase-to-phase differential protection device for a three-phase split transformer, including: a phase-to-phase differential signal generation unit 701, a grade differential signal generation unit 702, a correlation judgment unit 703 and a differential protection unit 704.

[0141] The phase-to-phase differential signal generation unit 701 is used to monitor the phase-to-phase amplitude differential and phase-to-phase phase differential on each voltage level side of the three-phase split transformer to obtain the phase-to-phase amplitude-phase differential signal; wherein, the phase-to-phase amplitude-phase differential signal includes the fault voltage level and fault phase information;

[0142] The differential signal generation unit 702 is used to determine the correlation between the high-frequency current signal spectra of two single-phase transformers that have failed at the fault voltage level based on the fault phase information if the duration of the phase-to-phase amplitude differential signal exceeds the duration threshold.

[0143] The correlation determination unit 703 is used to output a voltage level phase differential signal if the correlation is lower than the correlation threshold.

[0144] The differential protection unit 704 is used to activate the phase-to-phase differential protection and control the three-phase split transformer to take it out of operation if it detects that any two voltage level sides of the three voltage level sides of the three-phase split transformer output the voltage level phase-to-phase differential signal.

[0145] In one embodiment, see Figure 8 The phase differential signal generation unit 701 includes: an amplitude signal generation module 801, a phase signal generation module 802, and a phase differential signal generation module 803.

[0146] The amplitude signal generation module 801 is used to monitor the phase-to-phase amplitude differential on each voltage level side of the three-phase split transformer and obtain the phase-to-phase amplitude differential signal.

[0147] The phase signal generation module 802 is used to monitor the phase difference between phases on each voltage level side of the three-phase split transformer and obtain the phase difference signal between phases.

[0148] The phase-to-phase differential signal generation module 803 is used to output a non-zero value for the phase-to-phase differential signal if both the phase-to-phase amplitude differential signal and the phase-to-phase phase differential signal are non-zero values ​​for the same phase under the same fault voltage level.

[0149] In one embodiment, see Figure 9 The amplitude signal generation module 801 includes a current amplitude monitoring module 901 and an amplitude signal output module 902.

[0150] The current amplitude monitoring module 901 is used to monitor the high-frequency current amplitude of each phase under each voltage level.

[0151] The amplitude signal output module 902 is used to determine whether to output the phase-to-phase amplitude differential signal as a non-zero value based on the mean amplitude of the white noise, the standard deviation of the white noise amplitude, and the amplitude of the high-frequency current.

[0152] In one embodiment, see Figure 10 The phase signal generation module 802 includes a current phasor monitoring module 1001 and a phase signal output module 1002.

[0153] The current phasor monitoring module 1001 is used to monitor the high-frequency current phasors of each phase under each voltage level.

[0154] The phase signal output module 1002 is used to determine whether to output the interphase phase differential signal as a non-zero value based on the preset critical phase angle and the difference in phase angles of each high-frequency current phasor under the voltage level.

[0155] In one embodiment, see Figure 11 The differential signal generation unit 702 includes: a time series acquisition module 1101, an energy vector generation module 1102, and a related calculation module 1103.

[0156] Time series acquisition module 1101 is used to acquire The time series of high-frequency current signals within a power frequency cycle; where... T It is an integer;

[0157] The energy vector generation module 1102 is used to perform Fourier transform on the time series and calculate the spectral energy vectors corresponding to the fault at the fault voltage level; wherein the fault phase corresponds to the phase of the single-phase transformer.

[0158] The correlation calculation module 1103 is used to calculate the correlation between the high-frequency current signal spectra of the two single-phase transformers based on the spectral energy vectors corresponding to the two faults.

[0159] In one embodiment, see Figure 12 The differential protection unit 704 includes: a phase differential signal output module 1201 and a protection start module 1202.

[0160] The phase differential signal output module 1201 is used to output the voltage level phase differential signal if the high-frequency current between any two phases on a certain voltage level side meets the phase differential protection logic output condition; wherein, the voltage level phase differential signal includes a high-voltage side protection signal, a medium-voltage side protection signal and a neutral point protection signal;

[0161] The protection start-up module 1202 is used to start the phase-to-phase differential protection and control the three-phase split transformer to take off operation if at least two of the high-voltage side protection signal, medium-voltage side protection signal and neutral point protection signal are detected to be non-zero.

[0162] From a hardware perspective, in order to apply the differential protection method for a single transformer to multiple single-phase transformers and improve the response speed, sensitivity, and reliability of protection for three-phase split transformers, this application provides an embodiment of an electronic device for implementing all or part of the phase-to-phase differential protection method for the three-phase split transformer. The electronic device specifically includes the following components:

[0163] The system comprises a processor, a memory, a communications interface, and a bus; wherein the processor, memory, and communications interface communicate with each other via the bus; the communications interface is used to realize information transmission between the phase-to-phase differential protection device of the three-phase split transformer and related equipment such as the core business system, user terminals, and related databases; the logic controller can be a desktop computer, tablet computer, or mobile terminal, etc., and this embodiment is not limited to these. In this embodiment, the logic controller can be implemented with reference to the embodiments of the phase-to-phase differential protection method for the three-phase split transformer and the embodiments of the phase-to-phase differential protection device for the three-phase split transformer, the contents of which are incorporated herein, and repeated details will not be described again.

[0164] It is understood that the user terminal may include smartphones, tablet computers, network set-top boxes, portable computers, desktop computers, personal digital assistants (PDAs), in-vehicle devices, smart wearable devices, etc. Among these, the smart wearable devices may include smart glasses, smartwatches, smart bracelets, etc.

[0165] In practical applications, some aspects of the phase-to-phase differential protection method for a three-phase split transformer can be executed on the electronic device side as described above, or all operations can be completed in the client device. The choice can be made based on the processing capabilities of the client device and the limitations of the user's usage scenario. This application does not impose any limitations on this. If all operations are completed in the client device, the client device may further include a processor.

[0166] The aforementioned client device may have a communication module (i.e., a communication unit) that can communicate with a remote server to achieve data transmission. The server may include a server on the task scheduling center side; in other implementation scenarios, it may also include a server on an intermediate platform, such as a server on a third-party server platform that has a communication link with the task scheduling center server. The server may include a single computer device, a server cluster consisting of multiple servers, or a distributed server structure.

[0167] Figure 13 This is a schematic block diagram illustrating the system configuration of the electronic device 9600 according to an embodiment of this application. Figure 13 As shown, the electronic device 9600 may include a central processing unit 9100 and a memory 9140; the memory 9140 is coupled to the central processing unit 9100. It is worth noting that... Figure 13 This is an example; other types of structures can also be used to supplement or replace this structure to achieve telecommunications functions or other functions.

[0168] In one embodiment, the phase-to-phase differential protection method function of the three-phase split transformer can be integrated into the central processing unit 9100. The central processing unit 9100 can be configured to perform the following control:

[0169] S101: Monitor the phase-to-phase amplitude differential and phase-to-phase phase differential on each voltage level side of the three-phase split transformer to obtain the phase-to-phase amplitude-phase differential signal; wherein, the phase-to-phase amplitude-phase differential signal includes the fault voltage level and fault phase information;

[0170] S102: If the duration of the phase-to-phase amplitude differential signal exceeds the duration threshold, the correlation between the high-frequency current signal spectra of the two single-phase transformers that have failed at the fault voltage level is determined based on the fault phase-to-phase information.

[0171] S103: If the correlation is lower than the correlation threshold, output a voltage level phase differential signal;

[0172] S104: If it is detected that any two voltage level sides of the three-phase split transformer output the phase-to-phase differential signal of the voltage level, the phase-to-phase differential protection is activated, and the three-phase split transformer is controlled to take off the operation.

[0173] As can be seen from the above description, the phase-to-phase differential protection method for three-phase split transformers provided in this application can compare the amplitude, phase, duration, and spectrum information of high-frequency currents on the same voltage level side of the three-phase split transformer, and determine whether there is an internal fault in each phase transformer based on the phase-to-phase imbalance degree of the monitored quantities and the protection action logic. It extends the scope of differential protection from a single transformer to a three-phase split transformer. At the same time, since the monitored high-frequency current signals are all located on the same voltage level side, it solves the problem of protection maloperation caused by unbalanced currents on both sides of the transformer. The criteria and logic for initiating phase-to-phase differential protection accurately distinguish between internal faults and external interference in three-phase split transformers by using the amplitude, phase, duration, and spectrum information of high-frequency current. Considering that three-phase split transformers do not share cores and windings, but the high-frequency current still maintains three-phase symmetry during normal operation, the monitoring scope of differential protection is expanded from a single transformer to all three-phase split transformers, which helps improve the response speed and sensitivity of the protection. By comparing high-frequency current differences only when the acquisition equipment is located on the same voltage level side, the unbalanced current problem caused by the inconsistency of current transformer characteristics in traditional differential protection methods is overcome, making the protection method more reliable.

[0174] In another embodiment, the phase-to-phase differential protection device of the three-phase split transformer can be configured separately from the central processing unit 9100. For example, the phase-to-phase differential protection device of the three-phase split transformer can be configured as a chip connected to the central processing unit 9100, and the function of the phase-to-phase differential protection method of the three-phase split transformer can be realized through the control of the central processing unit.

[0175] like Figure 13 As shown, the electronic device 9600 may further include: a communication module 9110, an input unit 9120, an audio processor 9130, a display 9160, and a power supply 9170. It is worth noting that the electronic device 9600 does not necessarily need to include these components. Figure 13 All components shown; in addition, the electronic device 9600 may also include Figure 13 For components not shown, please refer to existing technologies.

[0176] like Figure 13 As shown, the central processing unit 9100, sometimes also referred to as a controller or operating control, may include a microprocessor or other processor device and / or logic device, which receives inputs and controls the operation of various components of the electronic device 9600.

[0177] The memory 9140 may be, for example, one or more of a cache, flash memory, hard drive, removable media, volatile memory, non-volatile memory, or other suitable devices. It may store the aforementioned failure-related information, and also store a program for executing that information. The central processing unit 9100 may execute the program stored in the memory 9140 to perform information storage or processing, etc.

[0178] Input unit 9120 provides input to central processing unit 9100. Input unit 9120 may be, for example, a keypad or touch input device. Power supply 9170 provides power to electronic device 9600. Display 9160 displays images and text. Display may be, for example, an LCD display, but is not limited thereto.

[0179] The memory 9140 can be a solid-state memory, such as a read-only memory (ROM), random access memory (RAM), a SIM card, etc. It can also be a memory that retains information even when power is off, can be selectively erased, and contains more data; examples of this type of memory are sometimes referred to as EPROMs. The memory 9140 can also be some other type of device. The memory 9140 includes a buffer memory 9141 (sometimes referred to as a buffer). The memory 9140 may include an application / function storage unit 9142 for storing application programs and function programs or processes for executing the operation of the electronic device 9600 via the central processing unit 9100.

[0180] The memory 9140 may also include a data storage unit 9143 for storing data, such as contacts, digital data, pictures, sounds, and / or any other data used by the electronic device. The driver storage unit 9144 of the memory 9140 may include various drivers for the electronic device's communication functions and / or for performing other functions of the electronic device (such as messaging applications, address book applications, etc.).

[0181] The communication module 9110 is a transmitter / receiver that sends and receives signals via the antenna 9111. The communication module (transmitter / receiver) 9110 is coupled to the central processing unit 9100 to provide input signals and receive output signals, which is the same as in a conventional mobile communication terminal.

[0182] Based on different communication technologies, multiple communication modules 9110 can be configured in the same electronic device, such as cellular network modules, Bluetooth modules, and / or wireless LAN modules. The communication module (transmitter / receiver) 9110 is also coupled to a speaker 9131 and a microphone 9132 via an audio processor 9130 to provide audio output via the speaker 9131 and receive audio input from the microphone 9132, thereby realizing typical telecommunications functions. The audio processor 9130 may include any suitable buffer, decoder, amplifier, etc. Additionally, the audio processor 9130 is also coupled to a central processing unit 9100, enabling on-device recording via the microphone 9132 and on-device playback of stored sound via the speaker 9131.

[0183] Embodiments of this application also provide a computer-readable storage medium capable of implementing all steps of the phase-to-phase differential protection method for a three-phase split transformer with a server or client execution subject as described in the above embodiments. The computer-readable storage medium stores a computer program that, when executed by a processor, implements all steps of the phase-to-phase differential protection method for a three-phase split transformer with a server or client execution subject as described in the above embodiments. For example, when the processor executes the computer program, it implements the following steps:

[0184] S101: Monitor the phase-to-phase amplitude differential and phase-to-phase phase differential on each voltage level side of the three-phase split transformer to obtain the phase-to-phase amplitude-phase differential signal; wherein, the phase-to-phase amplitude-phase differential signal includes the fault voltage level and fault phase information;

[0185] S102: If the duration of the phase-to-phase amplitude differential signal exceeds the duration threshold, the correlation between the high-frequency current signal spectra of the two single-phase transformers that have failed at the fault voltage level is determined based on the fault phase-to-phase information.

[0186] S103: If the correlation is lower than the correlation threshold, output a voltage level phase differential signal;

[0187] S104: If it is detected that any two voltage level sides of the three-phase split transformer output the phase-to-phase differential signal of the voltage level, the phase-to-phase differential protection is activated, and the three-phase split transformer is controlled to take off the operation.

[0188] As can be seen from the above description, the phase-to-phase differential protection method for three-phase split transformers provided in this application can compare the amplitude, phase, duration, and spectrum information of high-frequency currents on the same voltage level side of the three-phase split transformer, and determine whether there is an internal fault in each phase transformer based on the phase-to-phase imbalance degree of the monitored quantities and the protection action logic. It extends the scope of differential protection from a single transformer to a three-phase split transformer. At the same time, since the monitored high-frequency current signals are all located on the same voltage level side, it solves the problem of protection maloperation caused by unbalanced currents on both sides of the transformer. The criteria and logic for initiating phase-to-phase differential protection accurately distinguish between internal faults and external interference in three-phase split transformers by using the amplitude, phase, duration, and spectrum information of high-frequency current. Considering that three-phase split transformers do not share cores and windings, but the high-frequency current still maintains three-phase symmetry during normal operation, the monitoring scope of differential protection is expanded from a single transformer to all three-phase split transformers, which helps improve the response speed and sensitivity of the protection. By comparing high-frequency current differences only when the acquisition equipment is located on the same voltage level side, the unbalanced current problem caused by the inconsistency of current transformer characteristics in traditional differential protection methods is overcome, making the protection method more reliable.

[0189] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, apparatus, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0190] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (devices), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0191] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0192] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0193] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A phase-to-phase differential protection method for a three-phase split-type transformer, characterized in that, include: The phase-to-phase amplitude differential and phase-to-phase phase differential of each voltage level side of a three-phase split transformer are monitored to obtain the phase-to-phase amplitude-phase differential signal; wherein, the phase-to-phase amplitude-phase differential signal includes the fault voltage level and fault phase information; If the duration of the phase-to-phase amplitude differential signal exceeds the duration threshold, the correlation between the high-frequency current signal spectra of the two single-phase transformers that have failed at the fault voltage level is determined based on the fault phase-to-phase information. If the correlation is lower than the correlation threshold, output a phase-to-phase differential signal of the voltage level; If it is detected that any two voltage level sides of the three-phase split transformer output the phase-to-phase differential signal of the voltage level, the phase-to-phase differential protection is activated, and the three-phase split transformer is controlled to take off the operation. If the duration of the phase-to-phase amplitude differential signal exceeds a duration threshold, the correlation between the high-frequency current signal spectra of the two single-phase transformers that have failed at the fault voltage level is determined based on the fault phase-to-phase information, including: Get The time series of high-frequency current signals within a power frequency cycle; where... T It is an integer; Perform a Fourier transform on the time series and calculate the spectral energy vectors corresponding to the fault at the fault voltage level; wherein the fault phase corresponds to the phase of the single-phase transformer; The correlation between the high-frequency current signal spectra of the two single-phase transformers is calculated based on the corresponding spectral energy vectors of the two faults.

2. The phase-to-phase differential protection method for a three-phase split-type transformer according to claim 1, characterized in that, The monitoring of phase-to-phase amplitude and phase differentials at each voltage level of the three-phase split transformer to obtain phase-to-phase amplitude and phase differential signals includes: The phase-to-phase amplitude differential is monitored on each voltage level side of the three-phase split transformer to obtain the phase-to-phase amplitude differential signal; The phase-to-phase differential signal is obtained by monitoring the phase-to-phase differential signal on each voltage level side of the three-phase split transformer. For the same phase under the same fault voltage level, if both the phase-to-phase amplitude differential signal and the phase-to-phase phase differential signal are non-zero, the phase-to-phase amplitude differential signal is output as a non-zero value.

3. The phase-to-phase differential protection method for a three-phase split-type transformer according to claim 2, characterized in that, The phase-to-phase amplitude differential is monitored on each voltage level side of the three-phase split transformer to obtain the phase-to-phase amplitude differential signal, including: Monitor the high-frequency current amplitude of each phase under each voltage level; Whether to output the phase-to-phase amplitude differential signal as a non-zero value is determined based on the mean amplitude of the white noise, the standard deviation of the white noise amplitude, and the amplitude of the high-frequency current.

4. The phase-to-phase differential protection method for a three-phase split-type transformer according to claim 2, characterized in that, The phase-to-phase differential is monitored on each voltage level side of the three-phase split transformer to obtain the phase-to-phase differential signal, including: Monitor the high-frequency current phasors of each phase at each voltage level; Whether to output the interphase phase differential signal as a non-zero value is determined based on the preset critical phase angle and the difference in phase angles of each high-frequency current phasor under the voltage level.

5. The phase-to-phase differential protection method for a three-phase split-type transformer according to claim 1, characterized in that, If it is detected that any two voltage level sides of the three-phase split transformer output the phase-to-phase differential signal of the voltage level, the phase-to-phase differential protection is activated, and the three-phase split transformer is controlled to take off operation, including: If the high-frequency current between any two phases on a certain voltage level side meets the output conditions of the phase-to-phase differential protection logic, the voltage level side outputs the voltage level phase-to-phase differential signal; wherein, the voltage level phase-to-phase differential signal includes a high-voltage side protection signal, a medium-voltage side protection signal, and a neutral point protection signal; If at least two of the high-voltage side protection signal, medium-voltage side protection signal, and neutral point protection signal are detected to be non-zero, the phase-to-phase differential protection is activated, and the three-phase split transformer is controlled to exit operation.

6. A phase-to-phase differential protection device for a three-phase split-type transformer, characterized in that, include: The phase-to-phase differential signal generation unit is used to monitor the phase-to-phase amplitude differential and phase-to-phase phase differential on each voltage level side of the three-phase split transformer to obtain the phase-to-phase amplitude-phase differential signal; wherein, the phase-to-phase amplitude-phase differential signal includes the fault voltage level and fault phase information; A differential signal generation unit is used to determine the correlation between the high-frequency current signal spectra of two single-phase transformers that have failed at the fault voltage level, based on the fault phase information, if the duration of the phase-to-phase amplitude-phase differential signal exceeds a duration threshold. The correlation determination unit is used to output a voltage level phase differential signal if the correlation is lower than the correlation threshold. The differential protection unit is used to activate the phase-to-phase differential protection and control the three-phase split transformer to take it out of operation if it detects that any two voltage level sides of the three voltage level sides of the three-phase split transformer output the phase-to-phase differential signal of the voltage level. The differential signal generation unit includes: The time series acquisition module is used to acquire... The time series of high-frequency current signals within a power frequency cycle; where... T It is an integer; An energy vector generation module is used to perform a Fourier transform on the time series and calculate the spectral energy vectors corresponding to the fault at the fault voltage level; wherein the fault phase corresponds to the phase of the single-phase transformer. The correlation calculation module is used to calculate the correlation between the high-frequency current signal spectra of the two single-phase transformers based on the corresponding spectral energy vectors of the two faults.

7. The phase-to-phase differential protection device for a three-phase split-type transformer according to claim 6, characterized in that, The phase-to-phase differential signal generation unit includes: An amplitude signal generation module is used to monitor the phase-to-phase amplitude differential on each voltage level side of the three-phase split transformer and obtain the phase-to-phase amplitude differential signal. The phase signal generation module is used to monitor the phase difference between phases on each voltage level side of the three-phase split transformer and obtain the phase difference signal between phases. The phase-to-phase differential signal generation module is used to output a non-zero value for the phase-to-phase amplitude differential signal if both the phase-to-phase amplitude differential signal and the phase-to-phase phase differential signal are non-zero values ​​for the same phase under the same fault voltage level.

8. The phase-to-phase differential protection device for a three-phase split-type transformer according to claim 7, characterized in that, The amplitude signal generation module includes: The current amplitude monitoring module is used to monitor the high-frequency current amplitude of each phase under each voltage level. An amplitude signal output module is used to determine whether to output the phase-to-phase amplitude differential signal as a non-zero value based on the mean amplitude of the white noise, the standard deviation of the white noise amplitude, and the amplitude of the high-frequency current.

9. The phase-to-phase differential protection device for a three-phase split-type transformer according to claim 7, characterized in that, The phase signal generation module includes: The current phasor monitoring module is used to monitor the high-frequency current phasors of each phase under each voltage level. The phase signal output module is used to determine whether to output the interphase phase differential signal as a non-zero value based on the preset critical phase angle and the difference in phase angles of each high-frequency current phasor under the voltage level.

10. The phase-to-phase differential protection device for a three-phase split-type transformer according to claim 6, characterized in that, The differential protection unit includes: Each phase differential signal output module is used to output the voltage level phase differential signal if the high-frequency current between any two phases on a certain voltage level side meets the phase differential protection logic output condition; wherein, the voltage level phase differential signal includes a high-voltage side protection signal, a medium-voltage side protection signal, and a neutral point protection signal; The protection start-up module is used to activate the phase-to-phase differential protection and control the three-phase split transformer to take off operation if at least two of the high-voltage side protection signal, medium-voltage side protection signal and neutral point protection signal are detected to be non-zero.

11. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps of the phase-to-phase differential protection method for a three-phase split transformer as described in any one of claims 1 to 5.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the phase-to-phase differential protection method for a three-phase split transformer as described in any one of claims 1 to 5.

13. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the steps of the phase-to-phase differential protection method for a three-phase split transformer as described in any one of claims 1 to 5.

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