Phase-to-phase differential protection method and device for three-phase split type transformer

Abstract

The invention provides an inter-phase differential protection method and device for a three-phase split type transformer. The inter-phase differential protection method comprises the steps that inter-phase amplitude differential motion and inter-phase phase differential motion of all voltage grade sides of the three-phase split type transformer are monitored, and inter-phase amplitude phase differential motion signals are obtained; if the duration of the phase-to-phase amplitude phase differential signal exceeds a duration threshold value, the correlation between high-frequency current signal frequency spectrums of the two single-phase transformers which break down under the fault voltage level is judged according to fault phase-to-phase information; if the correlation is lower than a correlation threshold value, outputting a voltage level inter-phase differential signal; if it is monitored that any two voltage class sides in the three voltage class sides of the three-phase split type transformer output voltage class inter-phase differential signals, inter-phase differential protection is started, and the three-phase split type transformer is controlled to exit operation. The differential protection method for the single transformer can be applied to multiple single-phase transformers, and the response speed, sensitivity and reliability of protection of the three-phase split type transformer are improved.

Description

Technical Field

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

[0002] Transformers are vital equipment in power systems. Their safe and stable operation is crucial to the overall operation of power systems. Effective protection measures must be taken to prevent and reduce transformer failures. The main protection of existing transformers is differential protection and gas protection. The protection range is limited to a single transformer and cannot protect other members of the three-phase split transformer in time, which is not conducive to improving the sensitivity of the three-phase split transformer protection.

[0003] Three-phase split transformers are usually characterized by high voltage level and large capacity. They are widely used in EHV and UHV substations and are key core equipment. Three-phase split transformers are composed of three independent single-phase transformers, each with its own winding and core. This structure brings challenges in phase differential protection, because it is necessary to ensure that the differential protection of each single-phase transformer unit can operate correctly and coordinate with each other properly.

[0004] At present, transformer differential protection is used to monitor the internal faults of single-phase transformers, but has not yet protected other phase transformers of three-phase split transformers. The existing transformer interphase protection focuses on dealing with external transformer interphase short-circuit faults, and is a backup protection, which is difficult to respond quickly to transformer internal faults. How to use the interphase difference of electrical quantities of three-phase split transformers to propose a fast and effective protection method has become an urgent problem to be solved.

[0005] This section is intended to provide a background or context to the embodiments of the invention recited in the claims. No admission is made that the description herein is prior art by inclusion in this section. Summary of the invention

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

[0007] In order to solve the above technical problems, this application provides the following technical solutions:

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

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

[0010] If the duration of the phase-to-phase amplitude phase 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 according to the fault phase-to-phase information;

[0011] If the correlation is lower than the correlation threshold, outputting a voltage level interphase differential signal;

[0012] If it is monitored that any two voltage level sides among the three voltage level sides of the three-phase split transformer output the voltage level phase differential signal, the phase differential protection is started and the three-phase split transformer is controlled to exit operation.

[0013] Furthermore, the phase-to-phase amplitude differential and phase-to-phase phase differential on each voltage level side of the three-phase split transformer are monitored to obtain the phase-to-phase amplitude-to-phase differential signal, including:

[0014] Monitoring the inter-phase amplitude differential on each voltage level side of the three-phase split transformer to obtain an inter-phase amplitude differential signal;

[0015] Monitoring the interphase phase difference at each voltage level side of the three-phase split transformer to obtain an interphase phase difference signal;

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

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

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

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

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

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

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

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

[0024] Obtaining a time series of high-frequency current signals within T power frequency cycles; wherein T is an integer;

[0025] Performing Fourier transformation on the time series, and calculating two corresponding frequency spectrum energy vectors of the fault under 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 according to the two corresponding spectrum energy vectors of the fault.

[0027] Furthermore, if it is monitored that any two voltage level sides of the three voltage level sides of the three-phase split transformer output the voltage level phase differential signal, the phase differential protection is started, and the three-phase split transformer is controlled to exit operation, including:

[0028] If the high-frequency current between any two phases on a certain voltage level side meets the phase differential protection logic output condition, the voltage level outputs the voltage level phase differential signal; 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;

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

[0030] In a second aspect, the present application provides a phase-to-phase differential protection device for a three-phase split transformer, comprising:

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

[0032] A level differential signal generating unit, configured to determine the correlation between the high-frequency current signal spectra of two single-phase transformers that have failed at the fault voltage level according to the fault phase information if the duration of the phase-to-phase amplitude phase differential signal exceeds a duration threshold;

[0033] A correlation judgment unit, configured to output a voltage level interphase differential signal if the correlation is lower than a correlation threshold;

[0034] The differential protection unit is used to start the phase-to-phase differential protection and control the three-phase split transformer to exit operation if it is monitored that any two voltage level sides among the three voltage level sides of the three-phase split transformer output the voltage level phase differential signal.

[0035] Furthermore, the inter-phase differential signal generating unit comprises:

[0036] An amplitude signal generating module, used for monitoring the inter-phase amplitude differential at each voltage level side of the three-phase split transformer to obtain an inter-phase amplitude differential signal;

[0037] A phase signal generating module, used for monitoring the inter-phase phase difference of each voltage level side of the three-phase split transformer to obtain an inter-phase phase difference signal;

[0038] The interphase differential signal generating module is used for outputting the interphase amplitude differential signal as a non-zero value for the same phase under the same fault voltage level if the interphase amplitude differential signal and the interphase phase differential signal are both non-zero values.

[0039] Furthermore, the amplitude signal generating module comprises:

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

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

[0042] Furthermore, the phase signal generating module comprises:

[0043] Current phasor monitoring module, used to monitor the high-frequency current phasor of each phase at each voltage level side;

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

[0045] Furthermore, the level differential signal generating unit includes:

[0046] A time series acquisition module is used to acquire the time series of high-frequency current signals within T power frequency cycles; wherein T is an integer;

[0047] An energy vector generation module, used for performing Fourier transform on the time series and calculating two corresponding frequency spectrum energy vectors of the fault under 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 two single-phase transformers according to the two corresponding spectrum energy vectors of the fault.

[0049] Furthermore, the differential protection unit comprises:

[0050] Each phase differential signal output module is used for outputting 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 start the phase-to-phase differential protection and control the three-phase split transformer to exit operation if at least two of the high-voltage side protection signal, the medium-voltage side protection signal and the neutral point protection signal are monitored to be non-zero values.

[0052] In a third aspect, the present application provides an electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the program, the steps of the phase-to-phase differential protection method of the three-phase split transformer are implemented.

[0053] In a fourth aspect, the present 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] In a fifth aspect, the present application provides a computer program product, comprising a computer program / instruction, which, when executed by a processor, implements the steps of the phase-to-phase differential protection method for the three-phase split transformer.

[0055] In response to the problems in the prior art, the phase-to-phase differential protection method and device for a three-phase split transformer provided in the present application can compare the amplitude, phase, duration and spectrum information of the high-frequency current 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 quantity and the protection action logic; it expands the scope of differential protection from a single transformer to a three-phase split transformer, and at the same time, since the monitored high-frequency current signals are all on the same voltage level side, the problem of false protection caused by unbalanced current on both sides of the transformer is solved. Among them, the judgment criterion and logic for the activation of phase-to-phase differential protection is to accurately distinguish the situation where the three-phase split transformer has an internal fault and is subject to external interference through the amplitude, phase, duration and spectrum information of the high-frequency current; in view of the fact that the three-phase split transformer does not share the core and winding, but the high-frequency current still satisfies the three-phase symmetry during normal operation, the monitoring object range of the differential protection is expanded from a single transformer to a three-phase split transformer, which helps to improve the response speed and sensitivity of the protection; the high-frequency current difference is compared only when the acquisition equipment is located on the same voltage level side, which overcomes the unbalanced current problem caused by the incomplete consistency of the current transformer characteristics in the traditional differential protection method, making the protection method more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0057] Figure 1 This is a flow chart of a phase-to-phase differential protection method for a three-phase split transformer in an embodiment of the present application;

[0058] Figure 2 This is a flow chart of obtaining the phase-to-phase amplitude phase differential signal in an embodiment of the present application;

[0059] Figure 3 A flow chart of obtaining an inter-phase amplitude differential signal in an embodiment of the present application;

[0060] Figure 4 This is a flow chart of obtaining the phase differential signal between phases in an embodiment of the present application;

[0061] Figure 5 This is a flowchart for determining correlation in an embodiment of the present application;

[0062] Figure 6 This is a flow chart of controlling the three-phase split transformer to exit operation in an embodiment of the present application;

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

[0064] Figure 8 This is a structural diagram of an inter-phase differential signal generating unit in an embodiment of the present application;

[0065] Fig. 9 This is a structural diagram of the amplitude signal generating module in an embodiment of the present application;

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

[0067] Fig.11 This is a structural diagram of a level differential signal generating unit in an embodiment of the present application;

[0068] Fig.12 This is a structural diagram of a differential protection unit in an embodiment of the present application;

[0069] Fig.13 A schematic diagram of the structure of an electronic device in an embodiment of the present application;

[0070] Fig.14 This is a logical diagram of phase-to-phase differential protection in an embodiment of the present application;

[0071] Fig.15 A three-phase high-frequency current vector diagram in an embodiment of the present application;

[0072] Fig.16 This is a logic diagram of protection of the same voltage level side in the embodiment of the present application (taking the high voltage side as an example);

[0073] Fig.17 It is the overall protection logic in the embodiment of this application;

[0074] Fig.18 This is a wiring diagram of high-frequency current phase-to-phase differential protection of a three-phase split transformer in an embodiment of the present application (taking the high-voltage side as an example). DETAILED DESCRIPTION

[0075] To make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. Here, the exemplary 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, and the collection, storage, use, processing, transmission, provision, disclosure and application of relevant data comply with the relevant laws, regulations and standards of relevant countries and regions, take necessary confidentiality measures, do not violate public order and good morals, and provide corresponding operation entrances for users to choose to authorize or refuse.

[0077] Provide users with corresponding operation entrances for them to choose to agree or reject the automated decision-making results; if the user chooses to reject, the expert decision-making process will be entered.

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

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

[0080] S102: If the duration of the phase-to-phase amplitude phase differential signal exceeds a duration threshold, determine the correlation between the high-frequency current signal spectra of two single-phase transformers that have failed at the fault voltage level according to the fault phase-to-phase information;

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

[0082] S104: If it is monitored that any two voltage level sides among the three voltage level sides of the three-phase split transformer output the voltage level phase differential signal, start the phase differential protection and control the three-phase split transformer to exit operation.

[0083] It is understandable that differential protection is based on Kirchhoff's current law, that is, the sum of the currents flowing into a node is equal to the sum of the currents flowing out of the node. When the transformer is operating normally, the currents on the primary and secondary sides are balanced; when an internal short circuit occurs, the fault current will break the balance. The differential protection device will trigger the protection action after detecting the current imbalance. However, due to the inconsistency of the characteristics of the current transformer, an unbalanced current will flow in the differential circuit. If this unbalanced current is too large, it may cause the differential protection to malfunction.

[0084] Transformer interphase protection means that the interphase voltage and current are balanced within a certain range under normal operation of the transformer. If an internal abnormality occurs, the interphase current and voltage will be unbalanced. At this time, the interphase protection device will promptly cut off the faulty phase to protect the safe operation of the transformer. Interphase protection has the characteristics of fast response, high sensitivity and high reliability, and is suitable for protecting large power equipment such as three-phase split transformers.

[0085] In view of the problem that the existing transformer differential protection has a limited protection range and is prone to false operation due to unbalanced current, this application proposes a phase-to-phase differential protection method for a three-phase split transformer, so that the concept of differential protection for a single transformer is simultaneously applicable to multiple single-phase transformers, thereby improving the response speed, sensitivity and reliability of the protection of the three-phase split transformer. The embodiment of the present application simultaneously collects high-frequency current signals of the three-phase split transformer located at the same voltage level side and in the frequency range of 1 to 100 MHz through equipment such as bushing current transformers and high-frequency current transformers. At the same time, the phase-to-phase characteristics of the signal are greatly different when an internal fault occurs in the transformer, and the impact of external interference on each single-phase transformer is basically the same as the protection action criterion, and combined with the protection logic, timely protection of the three-phase split transformer is achieved.

[0086] From the above description, it can be seen that the phase-to-phase differential protection method for the three-phase split transformer provided in the present application can compare the amplitude, phase, duration and spectrum information of the high-frequency current on the same voltage level side of the three-phase split transformer, and determine whether there is an internal fault in each phase transformer according to the phase-to-phase imbalance degree of the monitored quantity and the protection action logic; it expands the scope of differential protection from a single transformer to a three-phase split transformer, and at the same time, since the monitored high-frequency current signals are all on the same voltage level side, the problem of false protection caused by unbalanced current on both sides of the transformer is solved. Among them, the judgment criterion and logic for the activation of phase-to-phase differential protection is to accurately distinguish the situation where the three-phase split transformer has an internal fault and is subject to external interference through the amplitude, phase, duration and spectrum information of the high-frequency current; in view of the fact that the three-phase split transformer does not share the core and winding, but the high-frequency current still satisfies the three-phase symmetry during normal operation, the monitoring object range of the differential protection is expanded from a single transformer to a three-phase split transformer, which helps to improve the response speed and sensitivity of the protection; the high-frequency current difference is compared only when the acquisition equipment is located on the same voltage level side, which overcomes the unbalanced current problem caused by the incomplete consistency of the current transformer characteristics in the traditional differential protection method, making the protection method more reliable.

[0087] In one embodiment, see Figure 2 The monitoring of 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 includes:

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

[0089] It can be understood that the phase differential protection logic is as follows: Fig.14 As shown, it includes phase-to-phase amplitude differential, phase-to-phase phase differential, duration judgment and spectrum correlation analysis. Among them, phase-to-phase amplitude differential and phase-to-phase phase differential are the basic conditions for the effectiveness of phase-to-phase differential protection. Only when they are established at the same time, the duration judgment will be started. If the duration of the phase-to-phase amplitude differential and phase-to-phase phase differential taking effect at the same time meets the duration judgment condition, the spectrum correlation analysis is performed. After the correlation analysis passes, the phase-to-phase differential protection signal is issued.

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

[0091] The maximum value of the high-frequency current of the three-phase split transformer at the same voltage level and at the same time is I A ,I B ,I C When the transformer is operating normally, the collected signal has a small amplitude, which is called background noise. It is usually maintained within a certain range and can be regarded as white noise. Assuming that the white noise obeys a normal distribution, with a mean of μ and a standard deviation of σ, according to the "3σ principle", an abnormal situation occurs when the deviation between the amplitude and μ is more than 3σ. The prerequisite for the start of phase-to-phase amplitude differential protection is:

[0092] |I i -μ|>3σ, i=A,B,C

[0093] When the transformer is operating normally or is subject to external interference, I A ,I B ,I C The values ​​should be close, and the phase imbalance is low. When one of the transformers has an internal fault, the transformer adds a fault branch, and the high-frequency current amplitude will increase significantly, which is obviously different from 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 mmin{I A , I B}

[0096] Then the AB phase amplitude differential protection starts. m is the amplitude coefficient, which is usually in the range of 1.1 to 1.2. For phase B and phase C, phase C and phase A, and so on, no further explanation is given.

[0097] S202: Monitor the interphase phase difference of each voltage level side of the three-phase split transformer to obtain an interphase phase difference signal; specifically, see Figure 4 , monitor the phase difference between phases on each voltage level side of the three-phase split transformer to obtain a phase difference signal, including: S401: monitor the high-frequency current phasor of each phase on each voltage level side; S402: determine whether to output the phase difference signal as a non-zero value based on a preset critical phase angle and the difference between the phase angles of each high-frequency current phasor on the voltage level side.

[0098] It can be understood that the phase difference between phases is realized as follows:

[0099] The phase quantity of the three-phase high-frequency current of A, B, and C is I A ∠0°、I B ∠°-120°, I C ∠120°. When the transformer is operating normally or is subject to external interference, If an internal fault occurs in the transformer, the phase of the high-frequency current phasor difference will change.

[0100] Take phase A and phase B as an example, see Fig.15 As shown, with I A ,I B Significant growth, The phase angle will vary between 90° and 150°, corresponding to the leading The angle range is 0°~60°. The starting conditions for phase differential are:

[0101]

[0102] Where θ is the critical angle for phase differential starting, usually in the range of 5° to 10°.

[0103] in, Fig.15 The left diagram corresponds to "normal situation 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 applies to phase B and phase C, phase C and phase A, and so on, and no further details will be given.

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

[0106] It can be understood that the phase-to-phase amplitude differential and the phase-to-phase phase differential are the basic conditions for the effectiveness of the phase-to-phase differential protection. Only when they are established at the same time (the phase-to-phase amplitude differential signal and the phase-to-phase differential signal are both non-zero values), the phase-to-phase amplitude differential signal will be output as a non-zero value and the duration judgment will be started.

[0107] From the above description, it can be seen that the phase-to-phase differential protection method for the three-phase split transformer provided in the present application can 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 and phase differential signals.

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

[0109] S501: Obtain a time series of high-frequency current signals within T power frequency cycles; wherein T is an integer;

[0110] S502: Perform Fourier transform on the time series, and calculate two corresponding frequency spectrum energy vectors of the fault under 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 two single-phase transformers according to the two corresponding spectrum energy vectors of the fault.

[0112] It is understandable that the next step is to determine the duration. Due to the complexity of the operating environment, the acquisition device often receives occasional pulses with short duration and high amplitude. Most of these occasional pulses are external interference signals and will not cause serious impact on the transformer. Therefore, a duration determination step should be set to avoid frequent action of the protection system and cause false action.

[0113] The condition for judging the trigger duration is: observe the number of power frequency cycles that meet the phase-to-phase amplitude differential and phase-to-phase phase differential start conditions within T power frequency cycles. When it is detected that more than 80% of the power frequency cycles meet the relevant requirements, it indicates that the fault has a strong continuity and the signal should continue to be output to the protection system.

[0114] After judging the duration, perform spectrum correlation analysis. The specific steps are as follows:

[0115] The fault current will bring a large number of high-order harmonics, and there will be multiple peak intervals in the entire frequency band, which will change the spectrum components of the high-frequency current signal. The correlation between the high-frequency current signal spectra of two single-phase transformers can be compared to determine whether an abnormal fault has occurred.

[0116] On the basis of satisfying the duration judgment, the high-frequency current signal within T power frequency cycles is recorded as the time series y[t], t = 1, 2, ..., N, N is the signal length. To improve the operation speed, zero is added at the end of y[t] to make the signal length the next higher power of 2, let in is the rounding symbol. At this time, the number of zero padding is 2 p -N. The time series after zero filling is y0[t0], t0=1,2,…,2 p .

[0117] The fast Fourier transform of y0[t0] is:

[0118]

[0119] in, is one of the 2pth roots of unity.

[0120] Due to the symmetry of the discrete Fourier transform, only the first half of the data of Y[k] is retained. At this time, the range of the sequence number is k = 1, 2, ..., 2 p-1 . Divide Y[k] into 2 equal parts in order q Each piece of data is Y[k j ],k j =(j-1)·2 p-1-q +1,…,j·2 p-1-q ,j=1,2,…2 q After taking the modulus of the above data, the sum of the squares of all elements is calculated to obtain the signal energy of this frequency band:

[0121]

[0122] Arrange in order E j , forming the spectrum energy vector of the high-frequency current signal

[0123] The spectrum energy vectors of the three-phase split transformer are E A 、E B 、E C Taking the A-phase and B-phase transformers as an example, the correlation coefficient r between the A-phase spectrum energy vector and the B-phase spectrum energy vector is AB :

[0124]

[0125] In the formula E A 、E B The conditions for the spectral correlation analysis to be valid are:

[0126] r AB <K r

[0127] In the formula, K r is the correlation coefficient threshold, which is usually in the range of 0.3 to 0.5. At this time, the correlation between the spectrum energy distribution characteristics of the A-phase transformer and the B-phase transformer is weak, and the similarity is low. It can be considered that one of the A-phase and B-phase transformers has an abnormality.

[0128] The same applies to phase B and phase C, phase C and phase A, and so on, and no further details will be given.

[0129] From the above description, it can be seen that the phase-to-phase differential protection method for the three-phase split transformer provided in the present application can determine the correlation between the high-frequency current signal spectra of the two single-phase transformers that have faults under 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 6 If it is detected that any two voltage level sides of the three voltage level sides of the three-phase split transformer output the voltage level phase differential signal, the phase differential protection is started, and the three-phase split transformer is controlled to exit operation, including:

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

[0132] S602: If at least two of the high-voltage side protection signal, the medium-voltage side protection signal and the neutral point protection signal are monitored to be non-zero values, start the phase-to-phase differential protection and control the three-phase split transformer to exit operation.

[0133] It is understandable that the protection logic on the same voltage level side is as follows:

[0134] When the high-frequency current between any two phases on a voltage level side meets the phase differential protection logic output conditions, the protection device of this voltage level sends a protection signal. Fig.16As shown, any two phases AB, AC or BC on the high-voltage side send out a phase differential protection signal, which will cause the protection device on the high-voltage side to output a protection signal. In the present invention, the protection device monitors the high-frequency current 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 the embodiment of the present application is as follows:

[0136] If at least two protection devices on any two voltage level sides send out protection signals (a three-phase split transformer without a medium voltage side requires protection devices on the high voltage side and at the neutral point to send out protection signals at the same time), the protection system sends out a protection trip command to take the three-phase split transformer out of operation. Fig.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 double-winding non-autotransformer as an example, the wiring diagram of the phase-to-phase differential protection is shown in Fig.18 shown. Fig.18 TA1, TA2, and TA3 represent the high-frequency current collection devices on the high-voltage side of single-phase transformers A, B, and C, respectively. The differential relay protector is connected to the output circuit of the high-frequency current collection device on the high-voltage side of the two phases to record the amplitude, phase, and spectrum of the corresponding two-phase high-frequency current.

[0138] In summary, the present invention proposes a phase-to-phase differential protection method for a three-phase split transformer. The method utilizes the differences in phase amplitude, phase, and spectrum of high-frequency current signals during internal faults to achieve full-range protection of the three-phase split transformer, avoids the unbalanced current problem that may exist due to the influence of current transformer characteristics, and helps to ensure the safe operation of the three-phase split transformer.

[0139] Based on the same inventive concept, the embodiments of the present application also provide a phase-to-phase differential protection device for a three-phase split 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 by the phase-to-phase differential protection device for a three-phase split transformer is similar to the phase-to-phase differential protection method for a three-phase split transformer, the implementation of the phase-to-phase differential protection device for a three-phase split transformer can refer to the implementation of the method based on software performance benchmark determination, and the repeated parts will not be repeated. As used below, the terms "unit" or "module" can be a combination of software and / or hardware that implements a predetermined function. Although the system described in the following embodiments is preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceived.

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

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

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

[0143] The correlation judgment unit 703 is used to output a voltage level interphase differential signal if the correlation is lower than a correlation threshold;

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

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

[0146] The amplitude signal generating module 801 is used to monitor the inter-phase amplitude differential at each voltage level side of the three-phase split transformer to obtain an inter-phase amplitude differential signal;

[0147] The phase signal generating module 802 is used to monitor the inter-phase phase difference of each voltage level side of the three-phase split transformer to obtain an inter-phase phase difference signal;

[0148] The inter-phase differential signal generating module 803 is used for outputting the inter-phase amplitude differential signal as a non-zero value for the same phase under the same fault voltage level if the inter-phase amplitude differential signal and the inter-phase phase differential signal are both non-zero values.

[0149] In one embodiment, see Fig. 9 The amplitude signal generating 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 at each voltage level side;

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

[0152] In one embodiment, see Fig.10 The phase signal generating 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 phasor of each phase at each voltage level side;

[0154] The phase signal output module 1002 is used to determine whether to output the inter-phase phase differential signal as a non-zero value according to a preset critical phase angle and the difference between the phase angles of each high-frequency current phasor at the voltage level side.

[0155] In one embodiment, see Fig.11 The level differential signal generating unit 702 includes: a time series acquiring module 1101, an energy vector generating module 1102 and a related calculating module 1103.

[0156] The time series acquisition module 1101 is used to acquire the time series of the high-frequency current signal within T power frequency cycles; wherein T is an integer;

[0157] The energy vector generation module 1102 is used to perform Fourier transform on the time series and calculate the frequency spectrum energy vectors corresponding to the two faults under 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 two single-phase transformers according to the two corresponding spectrum energy vectors of the fault.

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

[0160] Each phase differential signal output module 1201 is used for outputting the voltage level phase differential signal if any two phase-to-phase high-frequency currents on a certain voltage level side meet the phase differential protection logic output conditions; 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 module 1202 is used to start the phase-to-phase differential protection and control the three-phase split transformer to exit operation if at least two of the high-voltage side protection signal, the medium-voltage side protection signal and the neutral point protection signal are monitored to be non-zero values.

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

[0163] Processor, memory, communication interface and bus; wherein the processor, memory and communication interface communicate with each other through the bus; the communication interface is used to realize information transmission between the phase differential protection device of the three-phase split transformer and related equipment such as the core business system, user terminal and related database; the logic controller can be a desktop computer, a tablet computer and a mobile terminal, etc., and the present embodiment is not limited thereto. In the present embodiment, the logic controller can be implemented with reference to the embodiment of the phase differential protection method of the three-phase split transformer and the embodiment of the phase differential protection device of the three-phase split transformer in the embodiment, and the contents thereof are incorporated herein, and the repeated parts are not repeated.

[0164] It is understandable that the user terminal may include a smart phone, a tablet electronic device, a network set-top box, a portable computer, a desktop computer, a personal digital assistant (PDA), a vehicle-mounted device, a smart wearable device, etc. Among them, the smart wearable device may include smart glasses, a smart watch, a smart bracelet, etc.

[0165] In practical applications, part of the phase-to-phase differential protection method of the 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 specific selection can be made based on the processing capability of the client device and the limitations of the user's usage scenario. This application does not limit this. If all operations are completed in the client device, the client device may also include a processor.

[0166] The client device may have a communication module (i.e., a communication unit) that can communicate with a remote server to achieve data transmission with the server. The server may include a server on the task scheduling center side, and other implementation scenarios 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, or a server cluster consisting of multiple servers, or a server structure of a distributed device.

[0167] Fig.13 FIG. 9 is a schematic block diagram of the system structure of the electronic device 9600 according to an embodiment of the present application. Fig.13 As shown, the electronic device 9600 may include a central processor 9100 and a memory 9140; the memory 9140 is coupled to the central processor 9100. It is worth noting that Fig.13 is exemplary; other types of structures may also be used to supplement or replace this structure to implement telecommunication 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 processor 9100. The central processor 9100 can be configured to perform the following control:

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

[0170] S102: If the duration of the phase-to-phase amplitude phase differential signal exceeds a duration threshold, determine the correlation between the high-frequency current signal spectra of two single-phase transformers that have failed at the fault voltage level according to the fault phase-to-phase information;

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

[0172] S104: If it is monitored that any two voltage level sides among the three voltage level sides of the three-phase split transformer output the voltage level phase differential signal, start the phase differential protection and control the three-phase split transformer to exit operation.

[0173] From the above description, it can be seen that the phase-to-phase differential protection method for the three-phase split transformer provided in the present application can compare the amplitude, phase, duration and spectrum information of the high-frequency current on the same voltage level side of the three-phase split transformer, and determine whether there is an internal fault in each phase transformer according to the phase-to-phase imbalance degree of the monitored quantity and the protection action logic; it expands the scope of differential protection from a single transformer to a three-phase split transformer, and at the same time, since the monitored high-frequency current signals are all on the same voltage level side, the problem of false protection caused by unbalanced current on both sides of the transformer is solved. Among them, the judgment criterion and logic for the activation of phase-to-phase differential protection is to accurately distinguish the situation where the three-phase split transformer has an internal fault and is subject to external interference through the amplitude, phase, duration and spectrum information of the high-frequency current; in view of the fact that the three-phase split transformer does not share the core and winding, but the high-frequency current still satisfies the three-phase symmetry during normal operation, the monitoring object range of the differential protection is expanded from a single transformer to a three-phase split transformer, which helps to improve the response speed and sensitivity of the protection; the high-frequency current difference is compared only when the acquisition equipment is located on the same voltage level side, which overcomes the unbalanced current problem caused by the incomplete consistency of the current transformer characteristics in the traditional differential protection method, 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 processor 9100. For example, the phase-to-phase differential protection device of the three-phase split transformer of the data composite transmission device can be configured as a chip connected to the central processor 9100, and the function of the phase-to-phase differential protection method of the three-phase split transformer is realized through the control of the central processor.

[0175] like Fig.13 As shown, the electronic device 9600 may also 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 have to include Fig.13 In addition, the electronic device 9600 may also include Fig.13 For components not shown, reference may be made to the prior art.

[0176] like Fig.13 As shown, the central processing unit 9100 is sometimes also referred to as a controller or an operation control, and may include a microprocessor or other processor device and / or logic device. The central processing unit 9100 receives input 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, a flash memory, a hard drive, a removable medium, a volatile memory, a non-volatile memory or other suitable devices. The above-mentioned information related to the failure may be stored, and a program for executing the relevant information may also be stored. The CPU 9100 may execute the program stored in the memory 9140 to implement information storage or processing, etc.

[0178] The input unit 9120 provides input to the central processing unit 9100. The input unit 9120 is, for example, a key or a touch input device. The power supply 9170 is used to provide power to the electronic device 9600. The display 9160 is used to display display objects such as images and texts. The display may be, for example, an LCD display, but is not limited thereto.

[0179] The memory 9140 may be a solid-state memory, such as a read-only memory (ROM), a random access memory (RAM), a SIM card, etc. It may also be a memory that saves information even when the power is off, can be selectively erased, and is provided with more data, examples of which are sometimes referred to as EPROMs, etc. The memory 9140 may 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, which is used to store application programs and function programs or processes for executing the operation of the electronic device 9600 through the central processor 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 communication functions of the electronic device and / or for executing 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 processor 9100 to provide input signals and receive output signals, which may be the same as the case of a conventional mobile communication terminal.

[0182] Based on different communication technologies, multiple communication modules 9110 may be provided in the same electronic device, such as a cellular network module, a Bluetooth module and / or a wireless LAN module. The communication module (transmitter / receiver) 9110 is also coupled to a speaker 9131 and a microphone 9132 via an audio processor 9130 to provide an audio output via the speaker 9131 and receive an audio input from the microphone 9132, thereby realizing a common telecommunication function. The audio processor 9130 may include any suitable buffer, decoder, amplifier, etc. In addition, the audio processor 9130 is also coupled to the central processor 9100, so that recording can be performed on the local machine through the microphone 9132, and the sound stored on the local machine can be played through the speaker 9131.

[0183] The embodiments of the present application also provide a computer-readable storage medium capable of implementing all steps of the interphase differential protection method for a three-phase split transformer in the above embodiment, where the execution subject is a server or a client. The computer-readable storage medium stores a computer program. When the computer program is executed by a processor, all steps of the interphase differential protection method for a three-phase split transformer in the above embodiment are implemented. For example, when the processor executes the computer program, the following steps are implemented:

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

[0185] S102: If the duration of the phase-to-phase amplitude phase differential signal exceeds a duration threshold, determine the correlation between the high-frequency current signal spectra of two single-phase transformers that have failed at the fault voltage level according to the fault phase-to-phase information;

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

[0187] S104: If it is monitored that any two voltage level sides among the three voltage level sides of the three-phase split transformer output the voltage level phase differential signal, start the phase differential protection and control the three-phase split transformer to exit operation.

[0188] From the above description, it can be seen that the phase-to-phase differential protection method for the three-phase split transformer provided in the present application can compare the amplitude, phase, duration and spectrum information of the high-frequency current on the same voltage level side of the three-phase split transformer, and determine whether there is an internal fault in each phase transformer according to the phase-to-phase imbalance degree of the monitored quantity and the protection action logic; it expands the scope of differential protection from a single transformer to a three-phase split transformer, and at the same time, since the monitored high-frequency current signals are all on the same voltage level side, the problem of false protection caused by unbalanced current on both sides of the transformer is solved. Among them, the judgment criterion and logic for the activation of phase-to-phase differential protection is to accurately distinguish the situation where the three-phase split transformer has an internal fault and is subject to external interference through the amplitude, phase, duration and spectrum information of the high-frequency current; in view of the fact that the three-phase split transformer does not share the core and winding, but the high-frequency current still satisfies the three-phase symmetry during normal operation, the monitoring object range of the differential protection is expanded from a single transformer to a three-phase split transformer, which helps to improve the response speed and sensitivity of the protection; the high-frequency current difference is compared only when the acquisition equipment is located on the same voltage level side, which overcomes the unbalanced current problem caused by the incomplete consistency of the current transformer characteristics in the traditional differential protection method, making the protection method more reliable.

[0189] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, devices, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented 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] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (apparatus), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0191] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0192] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0193] The present invention uses specific embodiments to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A phase differential protection method for a three-phase split transformer, characterized in that: include: The phase-to-phase amplitude differential and phase-to-phase phase differential on each voltage level side of the three-phase split transformer are monitored to obtain a phase-to-phase amplitude phase differential signal; wherein the phase-to-phase amplitude phase differential signal includes the fault voltage level and the fault phase information; If the duration of the phase-to-phase amplitude phase 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 according to the fault phase-to-phase information; If the correlation is lower than the correlation threshold, outputting a voltage level interphase differential signal; If it is monitored that any two voltage level sides among the three voltage level sides of the three-phase split transformer output the voltage level phase differential signal, the phase differential protection is started and the three-phase split transformer is controlled to exit operation.

2. The phase differential protection method of a three-phase split transformer according to claim 1, characterized in that: The monitoring of the inter-phase amplitude differential and the inter-phase phase differential on each voltage level side of the three-phase split transformer to obtain the inter-phase amplitude phase differential signal includes: Monitoring the inter-phase amplitude differential on each voltage level side of the three-phase split transformer to obtain an inter-phase amplitude differential signal; Monitoring the interphase phase difference at each voltage level side of the three-phase split transformer to obtain an interphase phase difference signal; For the same phase under the same fault voltage level, if the inter-phase amplitude differential signal and the inter-phase phase differential signal are both non-zero values, the output inter-phase amplitude differential signal is a non-zero value.

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

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

5. The phase-to-phase differential protection method for a three-phase split transformer according to claim 1, characterized in that: If the duration of the phase-to-phase amplitude phase differential signal exceeds a duration threshold, the correlation between the high-frequency current signal spectra of two single-phase transformers that have failed under the fault voltage level is determined according to the fault phase-to-phase information, including: Obtaining a time series of high-frequency current signals within T power frequency cycles; wherein T is an integer; Performing Fourier transformation on the time series, and calculating two corresponding frequency spectrum energy vectors of the fault under 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 according to the two corresponding spectrum energy vectors of the fault.

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

7. A phase differential protection device for a three-phase split transformer, characterized in that: include: The phase differential signal generating unit is used to monitor the phase amplitude differential and phase phase differential on each voltage level side of the three-phase split transformer to obtain the phase amplitude phase differential signal; wherein the phase amplitude phase differential signal includes the fault voltage level and the fault phase information; A level differential signal generating unit, configured to determine the correlation between the high-frequency current signal spectra of two single-phase transformers that have failed at the fault voltage level according to the fault phase information if the duration of the phase-to-phase amplitude phase differential signal exceeds a duration threshold; A correlation judgment unit, configured to output a voltage level interphase differential signal if the correlation is lower than a correlation threshold; The differential protection unit is used to start the phase-to-phase differential protection and control the three-phase split transformer to exit operation if it is monitored that any two voltage level sides among the three voltage level sides of the three-phase split transformer output the voltage level phase differential signal.

8. The interphase differential protection device for a three-phase split transformer according to claim 7, characterized in that: The inter-phase differential signal generating unit comprises: An amplitude signal generating module, used for monitoring the inter-phase amplitude differential at each voltage level side of the three-phase split transformer to obtain an inter-phase amplitude differential signal; A phase signal generating module, used for monitoring the inter-phase phase difference of each voltage level side of the three-phase split transformer to obtain an inter-phase phase difference signal; The interphase differential signal generating module is used for outputting the interphase amplitude differential signal as a non-zero value for the same phase under the same fault voltage level if the interphase amplitude differential signal and the interphase phase differential signal are both non-zero values.

9. The interphase differential protection device for a three-phase split transformer according to claim 8, characterized in that: The amplitude signal generating module comprises: The current amplitude monitoring module is used to monitor the high-frequency current amplitude of each phase at each voltage level side; The amplitude signal output module is used to determine whether to output the phase-to-phase amplitude differential signal as a non-zero value according to the white noise amplitude mean, the white noise amplitude standard deviation and the high-frequency current amplitude.

10. The interphase differential protection device for a three-phase split transformer according to claim 8, characterized in that: The phase signal generating module comprises: Current phasor monitoring module, used to monitor the high-frequency current phasor of each phase at each voltage level side; The phase signal output module is used to determine whether to output the inter-phase phase differential signal as a non-zero value based on a preset critical phase angle and the difference in phase angles of each high-frequency current phasor on the voltage level side.

11. The interphase differential protection device for a three-phase split transformer according to claim 7, characterized in that: The level differential signal generating unit comprises: A time series acquisition module is used to acquire the time series of high-frequency current signals within T power frequency cycles; wherein T is an integer; An energy vector generation module, used for performing Fourier transform on the time series and calculating two corresponding frequency spectrum energy vectors of the fault under 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 two single-phase transformers according to the two corresponding spectrum energy vectors of the fault.

12. The interphase differential protection device for a three-phase split transformer according to claim 7, characterized in that: The differential protection unit comprises: Each phase differential signal output module is used for outputting 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 start the phase-to-phase differential protection and control the three-phase split transformer to exit operation if at least two of the high-voltage side protection signal, the medium-voltage side protection signal and the neutral point protection signal are monitored to be non-zero values.

13. 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, the steps of the phase-to-phase differential protection method for a three-phase split transformer are implemented.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the phase-to-phase differential protection method for a three-phase split transformer are implemented.

15. A computer program product comprising a computer program / instructions, characterized in that When the computer program / instruction is executed by a processor, 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 6 are implemented.

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