A neutral line abnormal fault diagnosis method and system in a current transformer

Abstract

The application discloses a current transformer neutral line abnormal fault diagnosis method and system, and relates to the technical field of power system relay protection, which comprises the following steps: obtaining three-phase current information of each interval of a power system; calculating three-phase differential current sample values and three-phase braking current sample values based on the three-phase current information of each interval; judging whether a differential protection device satisfies a multi-phase starting condition based on the three-phase differential current sample values; judging whether the three-phase differential current sample values and the three-phase braking current sample values satisfy a preset proportional relationship; if yes, determining that a current transformer has a neutral line abnormal fault, and calculating a three-phase differential current phase relationship; judging an in-zone and out-zone fault of a differential protection based on the three-phase differential current phase relationship; and determining a neutral line abnormal interval of the current transformer based on the amplitude and phase relationship of the three-phase current information of each interval and the three-phase differential current sample values. The application alleviates the technical problem of difficulty in diagnosing the neutral line abnormal fault of the current transformer in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power system relay protection, in particular to a current transformer neutral line abnormal fault diagnosis method and system. BACKGROUND

[0002] Differential protection as the main protection of relay protection, its reliability depends on the correct transformation of the primary current by the current transformer circuit, if the secondary circuit of the current transformer neutral line is abnormal, such as improper measures, it may cause incorrect action of the differential protection. There have been many cases of differential protection misoperation caused by current transformer neutral line abnormality (resistance increases or completely broken line). Since the current transformer neutral line abnormality cannot be detected during normal operation of the power system, the influence of this abnormality on the differential protection is more serious.

[0003] The most obvious feature of the current transformer neutral line abnormality is that when the power system fails, the secondary side of the non-fault phase appears an abnormal current with waveform deviating to one side of the time axis, which is characterized by large amplitude and short duration. The influencing factors mainly include neutral line impedance value (the greater the impedance, the more obvious the shunt), load current, non-periodic component in short-circuit current, and transformer residual magnetism level.

[0004] For current transformer neutral line abnormality, most scholars currently mainly study the following two points:

[0005] (1) Since the abnormal current of the non-fault phase is caused by shunt of the fault phase, the sum of the abnormal currents of the non-fault phase must be not greater than the fault phase current. Therefore, for the non-fault phase, the fault phase current can be introduced as a braking quantity, and this criterion will be mislocked when the internal and external faults exist at the same time, especially for high resistance faults.

[0006] (2) Detect the second harmonic content of the three-phase fault current, and according to the size of the second harmonic content, different ratio braking coefficients are adopted, or when the second harmonic content is large, the differential protection is directly locked out. Since the second harmonic content in the three-phase fault current is very low when the current transformer neutral line is completely broken, this method will fail. SUMMARY

[0007] The purpose of the present application is to provide a current transformer neutral line abnormal fault diagnosis method and system to solve at least one of the above technical problems.

[0008] In a first aspect, an embodiment of the present application provides a neutral line abnormal fault diagnosis method for a current transformer, which is applied to a differential protection device of a power system, the differential protection device being connected with a current transformer of the power system; the method comprises: obtaining three-phase current information of each interval of the power system; calculating three-phase differential current sample values and three-phase braking current sample values based on the three-phase current information of each interval; judging whether the differential protection device satisfies a multi-phase starting condition based on the three-phase differential current sample values; if yes, judging whether the three-phase differential current sample values and the three-phase braking current sample values satisfy a preset proportional relationship; if yes, determining that the current transformer has a neutral line abnormal fault, and calculating a three-phase differential current phase relationship; performing differential protection in-zone and out-zone fault judgment based on the three-phase differential current phase relationship; and determining a neutral line abnormal interval of the current transformer based on an amplitude and phase relationship between the three-phase current information of each interval and the three-phase differential current sample values.

[0009] Further, the calculation formula of the three-phase differential current sample values comprises: In the formula, I nAK is an A-phase current sample value of the nth interval and the Kth sampling point; I nBK is a B-phase current sample value of the nth interval and the Kth sampling point; I nCK is a C-phase current sample value of the nth interval and the Kth sampling point; I dAK , I dBK , and I dCK are differential current sample values formed by differential protection of the Kth sampling point A, B and C respectively, and n is the number of intervals to which the differential protection is connected. In the formula, I fAK , I fBK , and I fCK are braking current sample values formed by differential protection of the Kth sampling point A, B and C respectively.

[0010] Further, the multi-phase starting condition comprises: there are continuous n1 sampling points satisfying at least two of the following inequalities: |I dAK | > K1I set1 , |I dBK | > K1I set1 , |I dCK | > K1I set1 , wherein I set1 is a differential protection setting value, K1 is a first proportional coefficient, and n1 is a positive integer.

[0011] Further, the judging whether the three-phase differential current sampling value and the three-phase braking current sampling value satisfy a preset proportional relationship comprises: judging whether the three-phase differential current sampling value and the three-phase braking current sampling value satisfy at least one of the following preset proportional relationships: I fBK >K2I fAK or I fCK >K2I fAK ; I fAK >K2I fBK or I fCK >K2I fBK ; I fAK >K2I fCK or I fBK >K2I fCK ; wherein K2 is a second proportional coefficient.

[0012] Further, the calculating the three-phase differential current phase relationship comprises: if any of the following relationships is satisfied for continuous n2 sampling points, determining that the three-phase differential current phase relationship is that the differential current phases are the same: I dAK >0 and I dBK >0 and I dCK >0; I dAK <0 and I dBK <0 and I dCK <0; wherein n2 is a positive integer.

[0013] Further, the judging whether the three-phase differential current sampling value and the three-phase braking current sampling value satisfy a preset proportional relationship comprises: judging whether the three-phase differential current sampling value and the three-phase braking current sampling value satisfy at least one of the following preset proportional relationships: I dAK >0 and I dBK >0 and I dCK >0; I dAK <0 and I dBK <0 and I dCK <0; wherein n2 is a positive integer.

[0014] Further, the determining the neutral abnormal interval of the current transformer based on the amplitude and phase relationship between the three-phase current information of each interval and the three-phase differential current sampling value comprises: determining, based on the three-phase current information of each interval and the three-phase differential current sampling value, an interval in which the current amplitude is the same as the differential current amplitude and an interval in which the three-phase current phase is the same as the differential current phase; and determining, as the neutral abnormal interval of the current transformer, an interval in which the current amplitude is the same as the differential current amplitude and the three-phase current phase is the same as the differential current phase.

[0015] Further, the method further comprises: if the multi-phase starting condition is not satisfied by the differential protection device, or the three-phase differential current sampling value and the three-phase braking current sampling value do not satisfy the preset proportional relationship, the differential protection device is processed according to normal logic.

[0016] In a second aspect, the embodiments of the present application further provide a neutral line abnormal fault diagnosis system of a current transformer, which is applied to a differential protection device of a power system, and the differential protection device is connected with a current transformer of the power system; the system comprises an acquisition module, a first calculation module, a first judgment module, a second judgment module, a second calculation module, a third judgment module and a determination module; the acquisition module is configured to acquire three-phase current information of each interval of the power system; the first calculation module is configured to calculate three-phase differential current sample values and three-phase braking current sample values based on the three-phase current information of each interval; the first judgment module is configured to judge whether the differential protection device satisfies a multi-phase starting condition based on the three-phase differential current sample values; the second judgment module is configured to judge whether the three-phase differential current sample values and the three-phase braking current sample values satisfy a preset proportional relationship if the differential protection device satisfies the multi-phase starting condition; the second calculation module is configured to determine that the current transformer has a neutral line abnormal fault and calculate a three-phase differential current phase relationship if the three-phase differential current sample values and the three-phase braking current sample values satisfy the preset proportional relationship; the third judgment module is configured to perform differential protection in-zone and out-zone fault judgment based on the three-phase differential current phase relationship; and the determination module is configured to determine a neutral line abnormal interval of the current transformer based on an amplitude-phase relationship of the three-phase current information of each interval and the three-phase differential current sample values.

[0017] In a third aspect, the embodiments of the present application further provide an electronic device, which comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, and the processor implements the method of the first aspect when executing the computer program.

[0018] The present application provides a neutral line abnormal fault diagnosis method and system of a current transformer, which is based on real-time acquisition of current information of each interval by differential protection, calculation of three-phase differential current values and three-phase braking current values of differential protection, and determination of a neutral line abnormality of a current transformer when three-phase differential current and braking current satisfy a certain proportional relationship under multi-phase starting of differential protection; then, when the neutral line abnormality of the current transformer is determined, in-zone and out-zone faults are distinguished based on a three-phase differential current phase relationship; finally, a neutral line abnormal branch of the current transformer is distinguished based on a differential current and an amplitude-phase relationship of each interval. The present application can identify various abnormalities such as a large neutral line resistance and complete disconnection of a current transformer, and after the abnormalities occur, differential protection in-zone faults act quickly and differential protection out-zone faults are reliable and inaction, thereby solving the technical problem of the existing neutral line abnormality of a current transformer and ensuring safe and reliable operation of a power system. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or prior art description. Obviously, the drawings described below are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor under the premise of the drawings.

[0020] Figure 1 A flow chart of a neutral line abnormal fault diagnosis method of a current transformer is provided for the embodiments of the present application.

[0021] Figure 2 A neutral line abnormal logic diagram of a current transformer is provided for the embodiments of the present application.

[0022] Figure 3 A neutral line abnormal branch logic diagram of a current transformer is provided for the embodiments of the present application.

[0023] Figure 4 An in-zone fault diagram under a neutral line abnormal condition of a current transformer is provided for the embodiments of the present application.

[0024] Figure 5 An out-zone fault diagram under a neutral line abnormal condition of a current transformer is provided for the embodiments of the present application.

[0025] Figure 6 A schematic diagram of a neutral line abnormal fault diagnosis system of a current transformer is provided for the embodiments of the present application. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] Embodiment one

[0028] Figure 1 A flow chart of a neutral line abnormal fault diagnosis method of a current transformer is provided for the embodiments of the present application. The method is applied to a differential protection device of a power system, and the differential protection device is connected with a current transformer of the power system. As shown in the figure, Figure 1 the method specifically includes the following steps:

[0029] Step S102, acquiring three-phase current information of each interval of the power system.

[0030] Step S104, based on the three-phase current information of each interval, calculating three-phase differential current sample values and three-phase braking current sample values.

[0031] Step S106, based on the three-phase differential current sample values, judging whether the differential protection device meets the multi-phase starting condition; if yes, executing step S108; if no, executing step S116.

[0032] Step S108, judging whether the three-phase differential current sample values and the three-phase braking current sample values meet a preset proportional relationship; if yes, executing step S110; if no, executing step S116.

[0033] Step S110, determining that the current transformer has a neutral line abnormal fault, and calculating a three-phase differential current phase relationship.

[0034] Step S112, based on the three-phase differential current phase relationship, judging the in-zone and out-zone faults of the differential protection.

[0035] Step S114, based on the amplitude and phase relationship of the three-phase current information of each interval and the three-phase differential current sample values, determining the neutral line abnormal interval of the current transformer.

[0036] Step S116, the differential protection device is processed according to the normal logic.

[0037] Specifically, the calculation formula of the three-phase differential current sample values includes:

[0038]

[0039] In the formula, I nAK is the A-phase current sample value of the Kth sampling point of the nth interval; I nBK is the B-phase current sample value of the Kth sampling point of the nth interval; I nCK is the C-phase current sample value of the Kth sampling point of the nth interval; I dAK , I dBK , I dCK are respectively the differential current sample values formed by the A-phase, B-phase and C-phase of the Kth sampling point of the differential protection, and n is the interval number accessed by the differential protection.

[0040] Specifically, the calculation formula of the three-phase braking current sample values includes:

[0041]

[0042] In the formula, I fAK , I fBK , I fCK are respectively the braking current sample values formed by the A-phase, B-phase and C-phase of the Kth sampling point of the differential protection.

[0043] Specifically, the multi-phase starting condition comprises: there are continuous n1 sampling points satisfying at least two of the following inequalities:

[0044] |I dAK |>K1I set1 ,|I dBK |>K1I set1 ,|I dCK |>K1I set1 (3)

[0045] wherein, I set1 is a differential protection setting value, K1 is a first proportional coefficient, and n1 is a positive integer. Preferably, K1 is 0.3-0.5, and n1 is 1-3.

[0046] Specifically, if there are continuous n1 sampling points satisfying any of the inequalities in formula (3) at the same time, the differential protection is started for the corresponding phase; if the differential protection is started for more than one phase, it is determined that the multi-phase starting condition is met.

[0047] Specifically, step S108 further comprises the following steps:

[0048] whether the three-phase differential current sampling values and the three-phase braking current sampling values satisfy at least one preset proportional relationship; the preset proportional relationship comprises:

[0049] I fBK >K2I fAK or I fCK >K2I fAK (4)

[0050] I fAK >K2I fBK or I fCK >K2I fBK (5)

[0051] I fAK >K2I fCK or I fBK >K2I fCK (6)

[0052] wherein, K2 is a second proportional coefficient. Preferably, K2 is 2-4.

[0053] Specifically, if any of the above preset proportional relationships (4), (5) and (6) is met, it is determined that the neutral line abnormal fault exists in the current transformer.

[0054] Specifically, the calculation of the three-phase differential current phase relationship in step S110 comprises:

[0055] if any of the following relationships is satisfied by continuous n2 sampling points, it is determined that the three-phase differential current phase relationship is the same differential current phase:

[0056] I dAK >0 and I dBK >0 and I dCK >0(7)

[0057] I dAK <0 and I dBK <0 and I dCK <0(8)

[0058] Wherein, n2 is a positive integer. Preferably, n2 is 1 to 3.

[0059] Specifically, step S112 further includes:

[0060] If the three-phase differential current phase relationship is the same, it is determined to be a fault outside the differential protection zone;

[0061] If the three-phase differential current phase relationship is that the differential current phases are different, it is determined to be a fault within the differential protection zone.

[0062] Specifically, step S114 further includes the following steps:

[0063] Step S1141, based on the three-phase current information of each interval and the three-phase differential current sampling value, determining the intervals where the interval current amplitude is the same as the differential current amplitude, and determining the intervals where the interval three-phase current phase is the same as the differential current phase;

[0064] Step S1142 , determining the interval where the interval current amplitude is the same as the differential current amplitude and the interval three-phase current phase is the same as the differential current phase as the neutral line abnormal interval of the current transformer.

[0065] Specifically, the relationship between the interval three-phase current amplitude and the differential current amplitude is calculated based on the following formula:

[0066] |I dAK -I mAK |<K3|I dAK | (9)

[0067] |I dBK -I mBK |<K3|I dBK | (10)

[0068] |I dCK -I mCK |<K3|I dCK | (11)

[0069] Where, I mAK is the current sampling value of phase A at the Kth sampling point in the mth interval; I mBK is the B-phase current sampling value at the K-th sampling point in the m-th interval; I mCKis the current sampling value of phase C at the Kth sampling point in the mth interval, and K3 is the proportional coefficient. If n3 consecutive sampling points satisfy any of the inequalities in equations (9), (10), and (11), then the phase and differential current amplitudes are determined to be equal; if n3 consecutive sampling points satisfy all three phases simultaneously, that is, if equations (9), (10), and (11) are satisfied simultaneously, then the branch (i.e., the interval) and differential current amplitudes are determined to be equal.

[0070] Specifically, the relationship between the phase of the three-phase current and the phase of the differential current is calculated based on the following formula:

[0071] I dAK *I mAK >0 (12)

[0072] I dBK *I mBK >0 (13)

[0073] I dCK *I mCK >0 (14)

[0074] If n4 consecutive sampling points satisfy any inequality in equations (12), (13), and (14), then it is judged that the phase is the same as the differential current phase; if n4 consecutive sampling points satisfy all three phases at the same time, that is, they satisfy equations (12), (13), and (14) at the same time, then it is judged that the branch (that is, the interval) is the same as the differential current phase.

[0075] Preferably, n3 takes a value of 1 to 3, and n4 takes a value of 1 to 3.

[0076] Specifically, if the mth interval has the same amplitude and phase as the differential current, the mth interval is selected as the abnormal interval of the neutral line of the current transformer.

[0077] Figure 2 FIG. 1 is a logic diagram of a current transformer neutral line abnormality provided by an embodiment of the present invention. Figure 2 As shown, taking phase A fault as an example, when phase A fails, if phase B or C differential starts, and the braking current of phase A is greater than I fAK >K2I fBK , or I fAK >K2I fCK , it is judged that the neutral line of the current transformer is abnormal and the current of phase A is diverted to phase B or phase C.

[0078] Figure 3 FIG. 1 is a logic diagram of an abnormal branch of a current transformer neutral line provided by an embodiment of the present invention. Figure 3 As shown, taking bay 1 as an example, when the neutral line of the current transformer is abnormal, if the three-phase current of bay 1 and the three-phase differential current have the same amplitude and phase, it is determined that the neutral line of the current transformer in bay 1 is abnormal.

[0079] Figure 4 is a schematic diagram of an in-zone fault under a neutral line abnormal condition of a current transformer according to an embodiment of the present application. As shown in Figure 4 , under the neutral line abnormal condition of the current transformer, the phases of three-phase differential currents are opposite, and then it is determined that the fault is an in-zone fault of differential protection.

[0080] Figure 5 is a schematic diagram of an out-zone fault under a neutral line abnormal condition of a current transformer according to an embodiment of the present application. As shown in Figure 5 , under the neutral line abnormal condition of the current transformer, the phases of three-phase differential currents are the same, and then it is determined that the fault is an out-zone fault of differential protection.

[0081] As can be seen from the above description, the embodiment of the present application provides a neutral line abnormal fault diagnosis method of a current transformer. Firstly, the differential protection device collects the currents of each interval in real time, calculates the three-phase differential current values of differential protection, and the three-phase braking current values. When the three-phase differential current and the braking current satisfy a certain proportional relationship under the multi-phase starting condition of differential protection, it is determined that the neutral line of the current transformer is abnormal. Secondly, when it is determined that the neutral line of the current transformer is abnormal, the in-zone and out-zone faults are distinguished based on the phase relationship of the three-phase differential current. Finally, the abnormal branch of the neutral line of the current transformer is distinguished based on the amplitude and phase relationship of the differential current and each interval. The present application can identify various abnormalities such as the increase of the neutral line resistance of the current transformer and the complete breakage. After the abnormality occurs, the differential protection in-zone fault operates quickly, and the out-zone fault is reliable and does not move, which solves the technical problem of the existing neutral line abnormality of the current transformer and ensures the safe and reliable operation of the power system.

[0082] Embodiment two

[0083] Figure 6 is a schematic diagram of a neutral line abnormal fault diagnosis system of a current transformer according to an embodiment of the present application. The system is applied to a differential protection device of a power system, and the differential protection device is connected with a current transformer of the power system. As shown in Figure 6 , the system comprises an acquisition module 10, a first calculation module 20, a first judgment module 30, a second judgment module 40, a second calculation module 50, a third judgment module 60 and a determination module 70.

[0084] Specifically, the acquisition module 10 is used to acquire the three-phase current information of each interval of the power system.

[0085] The first calculation module 20 is used to calculate the three-phase differential current sampling value and the three-phase braking current sampling value based on the three-phase current information of each interval.

[0086] The first judgment module 30 is used to judge whether the differential protection device satisfies the multi-phase starting condition based on the three-phase differential current sampling value.

[0087] The second judging module 40 is configured to judge whether the three-phase differential current sampling values and the three-phase braking current sampling values meet a preset proportional relationship if the differential protection device meets the multi-phase starting condition.

[0088] The second calculating module 50 is configured to determine that the current transformer has the neutral line abnormal fault and calculate the three-phase differential current phase relationship if the three-phase differential current sampling values and the three-phase braking current sampling values meet the preset proportional relationship.

[0089] The third judging module 60 is configured to judge the in-zone and out-zone faults of the differential protection based on the three-phase differential current phase relationship.

[0090] The determining module 70 is configured to determine the neutral line abnormal interval of the current transformer based on the amplitude and phase relationship of the three-phase current information of each interval and the three-phase differential current sampling values.

[0091] Specifically, the third judging module 60 is further configured to:

[0092] If the three-phase differential current phase relationship is the same differential current phase, it is judged as the out-zone fault of the differential protection.

[0093] If the three-phase differential current phase relationship is not the same differential current phase, it is judged as the in-zone fault of the differential protection.

[0094] Specifically, the determining module 70 is further configured to:

[0095] Determine the interval with the same current amplitude and differential current amplitude and the interval with the same current phase and differential current phase based on the three-phase current information of each interval and the three-phase differential current sampling values.

[0096] Determine the interval with the same current amplitude and differential current amplitude and the interval with the same current phase and differential current phase as the neutral line abnormal interval of the current transformer.

[0097] The embodiment of the present application also provides an electronic device, which comprises a memory, a processor and a computer program stored in the memory and capable of running on the processor, and the processor implements the method in the above embodiment one when executing the computer program.

[0098] It is apparent for those skilled in the art that the present application is not limited to the details of the above exemplary embodiments, and the present application can be implemented in other concrete forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present application is defined by the appended claims rather than the above description, and all changes falling within the meaning and range of the equivalent elements of the claims are intended to be included in the present application. Any reference signs in the claims should not be regarded as limiting the involved claims.

[0099] Furthermore, it should be understood that although the specification is described in terms of embodiments, the specification as a whole, and each embodiment individually, does not contain only one independent technical solution, and the specification is described in this way only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A method for diagnosing abnormal faults in the neutral line of a current transformer, characterized in that: A differential protection device applied to an electric power system, wherein the differential protection device is connected to a current transformer of the electric power system; the method comprising: Obtaining three-phase current information of each interval of the power system; Calculating three-phase differential current sampling values ​​and three-phase braking current sampling values ​​based on the three-phase current information of each interval; Based on the three-phase differential current sampling values, determining whether the differential protection device meets the multi-phase starting condition; If yes, determining whether the three-phase differential current sampling value and the three-phase braking current sampling value meet a preset proportional relationship; If yes, it is determined that there is an abnormal neutral line fault in the current transformer, and the phase relationship of the three-phase differential current is calculated; Performing fault judgment inside and outside the differential protection zone based on the phase relationship of the three-phase differential current; Determining an abnormal neutral line interval of the current transformer based on the amplitude and phase relationship of the three-phase current information of each interval and the three-phase differential current sampling value; The calculation formula of the three-phase differential current sampling value includes: ， ， ； Where, is the current sampling value of phase A at the Kth sampling point in the nth interval; is the B-phase current sampling value at the K-th sampling point in the n-th interval; is the C-phase current sampling value at the K-th sampling point in the n-th interval; 、 、 The differential current sampling values ​​formed by the K-th sampling point of differential protection phases A, B, and C respectively, where n is the number of intervals connected to the differential protection; The calculation formula of the three-phase braking current sampling value includes: ， ， ； Where, 、 、 are the braking current sampling values ​​formed by phases A, B, and C of the Kth sampling point of the differential protection respectively; Determining whether the three-phase differential current sampling value and the three-phase braking current sampling value meet a preset proportional relationship includes: Whether the three-phase differential current sampling value and the three-phase braking current sampling value satisfy at least one of the following preset proportional relationships; the preset proportional relationship includes: or ; or ; or ; in, is the second proportional coefficient; Calculate the three-phase differential current phase relationship, including: If any of the following relationships is satisfied by n2 consecutive sampling points, it is determined that the three-phase differential current phase relationship is the same: and and ; and and ; Wherein, n2 is a positive integer; Determining the abnormal neutral line interval of the current transformer based on the amplitude and phase relationship of the three-phase current information of each interval and the three-phase differential current sampling value includes: Based on the three-phase current information of each interval and the three-phase differential current sampling values, determining the intervals where the interval current amplitude is the same as the differential current amplitude, and determining the intervals where the interval three-phase current phase is the same as the differential current phase; Determine the interval where the interval current amplitude is the same as the differential current amplitude and the interval three-phase current phase is the same as the differential current phase as the neutral line abnormal interval of the current transformer; Determining the abnormal neutral line interval of the current transformer based on the amplitude and phase relationship of the three-phase current information of each interval and the three-phase differential current sampling value, further comprising: Based on the three-phase current information of each interval and the three-phase differential current sampling value, determine the intervals where the interval current amplitude is the same as the differential current amplitude, and determine the intervals where the interval three-phase current phase is the same as the differential current phase; The interval where the interval current amplitude is the same as the differential current amplitude and the interval three-phase current phase is the same as the differential current phase is determined as the neutral line abnormal interval of the current transformer; The relationship between the interval three-phase current amplitude and the differential current amplitude is calculated based on the following formula: ； ； ； Where, is the sampling value of phase A current at the Kth sampling point in the mth interval; is the B-phase current sampling value at the K-th sampling point in the m-th interval; is the C-phase current sampling value at the K-th sampling point in the m-th interval, is the proportional coefficient; if n3 consecutive sampling points satisfy any of the three inequalities in the above three formulas, it is judged that the phase is equal to the differential current amplitude; if n3 consecutive sampling points and the three phases satisfy the three formulas at the same time, it is judged that the interval is equal to the differential current amplitude; The relationship between the phase of the three-phase current and the phase of the differential current is calculated based on the following formula: ； ； ； If n4 consecutive sampling points satisfy any of the above three inequalities, it is judged that the phase is the same as the differential current phase; if n4 consecutive sampling points satisfy the above three inequalities at the same time, it is judged that the interval is the same as the differential current phase.

2. The method according to claim 1, wherein: The multi-phase starting condition includes: there are n1 consecutive sampling points that satisfy at least two of the following inequalities: ， ， ； in, is the differential protection setting, is the first proportional coefficient, and n1 is a positive integer.

3. The method according to claim 1, wherein: The fault judgment inside and outside the differential protection zone is performed based on the phase relationship of the three-phase differential current, including: If the three-phase differential current phase relationship is that the differential current phases are the same, it is determined to be a fault outside the differential protection zone; If the three-phase differential current phase relationship is that the differential current phases are different, it is determined to be a fault within the differential protection zone.

4. The method according to claim 1, wherein: The method further includes: if the differential protection device does not meet the multi-phase starting condition, or the three-phase differential current sampling value and the three-phase braking current sampling value do not meet the preset proportional relationship, the differential protection device processes according to normal logic.

5. A current transformer neutral line abnormal fault diagnosis system, characterized in that: Used to implement the current transformer neutral line abnormal fault diagnosis method according to any one of claims 1 to 4; applied to a differential protection device of an electric power system, the differential protection device is connected to the current transformer of the electric power system; the system comprises: an acquisition module, a first calculation module, a first judgment module, a second judgment module, a second calculation module, a third judgment module and a determination module; wherein, The acquisition module is used to acquire the three-phase current information of each interval of the power system; The first calculation module is used to calculate the three-phase differential current sampling value and the three-phase braking current sampling value based on the three-phase current information of each interval; The first judgment module is configured to judge whether the differential protection device meets the multi-phase starting condition based on the three-phase differential current sampling value; The second judgment module is configured to judge whether the three-phase differential current sampling value and the three-phase braking current sampling value satisfy a preset proportional relationship if the differential protection device satisfies the multi-phase starting condition; The second calculation module is configured to determine that a neutral line abnormal fault exists in the current transformer if the three-phase differential current sampling value and the three-phase braking current sampling value satisfy the preset proportional relationship, and calculate the phase relationship of the three-phase differential current; The third judgment module is used to judge the internal and external faults of the differential protection zone based on the phase relationship of the three-phase differential current; The determination module is configured to determine an abnormal neutral line interval of the current transformer based on the amplitude-phase relationship between the three-phase current information of each interval and the three-phase differential current sampling value.

6. An electronic device, characterized in that: include: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the method according to any one of claims 1 to 4 when executing the computer program.

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