Current transformer polarity detection method of multi-terminal branch differential protection device, storage medium, electronic equipment and computer program product

Abstract

The invention discloses a current transformer polarity detection method of a multi-terminal branch differential protection device, a storage medium, electronic equipment and a computer program product. The method comprises the following steps: determining the maximum branch current and differential current of a multi-terminal branch; judging a first state of the differential current according to the maximum branch current and the differential current; determining a differential current variation and a current variation of each branch according to the current of each branch, the differential current and the first state; if it is judged that the differential current variable quantity is two times of the current variable quantity of one and only one branch in the multi-end branches, one branch is determined to be an abnormal branch; grouping the multi-terminal branches according to the current of the multi-terminal branches and the current of the abnormal branch; determining the vector and absolute value of the current and the vector and absolute value variation of the current of the branches of each group after grouping; judging a second state of the abnormal branch according to the vector and the absolute value variation of the current; and verifying the abnormal branch according to the second state.

Description

Technical Field

[0001] The present application relates to the technical field of line relay protection, and in particular to a current transformer polarity detection method, storage medium, electronic equipment and computer program product for a multi-terminal branch differential protection device. Background Art

[0002] A multi-terminal differential protection device is usually set on a line containing multi-terminal branches to protect the multi-branch transmission and distribution lines. A current transformer (CT) is usually set on the branch line to convert the primary current on the line into a secondary current that can be used by the protection device. If the polarity of the current transformer is reversed, it will cause deviations in the calculation of the differential current and affect the fault identification on the multi-terminal branch line, causing the multi-terminal branch differential protection device to malfunction or refuse to operate.

[0003] For a double-terminal line, when the polarity of the current transformer of a branch is reversed, the polarity error of the current transformer can be simply identified through the relationship between the differential current and the branch current.

[0004] For multi-terminal branches, a single differential current alarm is usually used to identify possible current transformer polarity errors.

[0005] However, the inventors have found that the technical solution of using a single differential current alarm to identify possible polarity errors of current transformers has the following problems:

[0006] 1. In order to avoid false alarms of reverse polarity of current transformers, the differential current alarm threshold is often set conservatively. For light-load lines, this will reduce the sensitivity of detecting current transformer polarity errors.

[0007] 2. In order to locate the branch with incorrect polarity of the current transformer, after the alarm device reports the differential current alarm, it is necessary to manually check whether each branch is a load branch or a power supply branch, and check the current polarity in combination with the current flow direction of the power grid. This makes it complicated to check the polarity errors of the current transformers in multi-terminal branches. Summary of the invention

[0008] According to one aspect of the present application, a current transformer polarity detection method for a multi-terminal branch differential protection device is provided. The multi-terminal branch includes at least three branches, and current transformers are arranged on at least three branches. The method includes: determining the maximum branch current information and differential current information of the multi-terminal branch; judging the first state of the differential current information according to the maximum branch current information and the differential current information; determining the differential current information change amount and the current information change amount of each branch according to the current information, differential current information and the first state of each branch; determining that the differential current information change amount is twice the current information change amount of one and only one branch in the multi-terminal branch, then determining that one branch is an abnormal branch; grouping the multi-terminal branches according to the current information of the multi-terminal branches and the current information of the abnormal branches; determining the vector and absolute value of the current information of the branches in each group after grouping and the vector and absolute value change amount of the current information; judging the second state of the abnormal branch according to the vector and absolute value change amount of the current information; and verifying the abnormal branch according to the second state.

[0009] According to some embodiments of one aspect of the present application, the maximum branch current information is the maximum value of the effective value of the current information of each branch in the multi-terminal branch; the differential current information is the vector and absolute value of the current information of each branch.

[0010] According to some embodiments of one aspect of the present application, the above-mentioned step of determining the first state of the differential current information based on the maximum branch current information and the differential current information may include: when the differential current information is greater than a preset condition of the differential current, determining that the first state is that the differential current information meets the preset condition.

[0011] The preset condition of the differential current information is determined according to the following formula:

[0012] I d_ystj =K 1 max(I N ,I max ),

[0013] I d_ystj is the precondition of differential current information, K 1 is the ratio coefficient, I max is the maximum branch current information, I N It is the maximum rated primary current information of the current transformer.

[0014] According to some embodiments of one aspect of the present application, the above-mentioned step of determining the differential current information change amount and the current information change amount of each branch according to the current information of each branch, the differential current information and the first state may include: determining that the differential current information change amount is t when it is judged that the first state is that the differential current information meets the preset condition 2 The differential current information at time t1 The difference of the differential current information at time |t 2 -t 1 | is an integer multiple of the fundamental wave period of the current information;

[0015] The current information change of each branch is determined according to the following formula:

[0016]

[0017] Where i is the i-th branch in the multi-terminal branch, t 1 The scalar current information of the i-th branch at time, t 2 The scalar current information of the i-th branch at time, ΔI i is the current information change of the i-th branch in the multi-terminal branch, |t 2 -t 1 | is an integer multiple of the fundamental wave period of the current information.

[0018] According to some embodiments of one aspect of the present application, the above-mentioned step of grouping the multi-terminal branches according to the current information of the multi-terminal branches and the current information of the abnormal branch may include: determining the current relative angle between the current information of other branches and the current information of the abnormal branch, the other branches are the branches of the multi-terminal branches excluding the abnormal branch; grouping the other branches according to the current relative angle, taking the phase of the current information of the abnormal branch as the reference 0°; determining the branches in the other branches that satisfy -90°≤θ≤90° as the first group of branches; determining the branches in the other branches that satisfy 90°<θ<270° as the second group of branches; the abnormal branches are the third group of branches; wherein θ is the relative angle between the phase of the current information of the other branches and the phase of the current information of the abnormal branch, taking the phase of the current information of the abnormal branch as the reference 0°.

[0019] According to some embodiments of one aspect of the present application, the above-mentioned step of determining the vector sum absolute value of the current information of the branches of each group after grouping and the vector sum absolute value of the change amount of the current information may include: determining the vector sum absolute value of the current information of the branches in the first group of branches; calculating the vector sum absolute value change amount of the current information of the first group of branches according to the following formula:

[0020] ΔI A =I A (t 2 )-I A (t 1 );

[0021] Among them, when the first group of branches does not exist, ΔI A is 0;

[0022] Determine the vector sum absolute value of the current information of the branches in the second group of branches; calculate the vector sum absolute value change of the current information of the second group of branches according to the following formula:

[0023] ΔI B =I B (t 2 )-I B (t 1 );

[0024] In the absence of the second set of branches, ΔI B is 0;

[0025] Determine the vector absolute value of the current information of the branches in the third group of branches; calculate the vector absolute value change of the current information of the third group of branches according to the following formula:

[0026] ΔI k =I k (t 2 )-I k (t 1 );

[0027] Among them, ΔI A is the vector and absolute value change of the current information of the first group of branches, I A (t 1 ) is t 1 The vector and absolute value of the current information of the first group of branches at time , I A (t 2 ) is t 2 The vector and absolute value of the current information of the first group of branches at time |t 2 -t 1 | is an integer multiple of the fundamental wave period of the current information.

[0028] ΔI B is the vector and absolute value change of the current information of the second group of branches, I B (t 1 ) is t 1 The vector and absolute value of the current information of the second group of branches at time , I B (t 2 ) is t 2 The vector and absolute values ​​of the current information of the second group of branches at time instant.

[0029] ΔI k is the vector absolute value change of the current information of the third group of branches, I k (t 1 ) is t 1 The vector absolute value of the current information of the third group of branches at time t, I k (t 2 ) is t2 The vector absolute value of the current information of the third group of branches at time instant.

[0030] According to some embodiments of one aspect of the present application, the step of judging the second state of the abnormal branch according to the vector and absolute value changes of the current information may include: judging that the second state is that the abnormal branch is in an abnormal state when the vector and absolute value changes of the current information of each group meet a preset judgment condition;

[0031] Among them, the preset judgment conditions are:

[0032] (1-K 2 )(ΔI k +ΔI B )<ΔI A <(1+K 2 )(ΔI k +ΔI B )

[0033] ΔI A ΔI K >0

[0034] Among them, K 2 is the proportionality coefficient, and 0<K 2 ≤0.2.

[0035] According to some embodiments of one aspect of the present application, the step of verifying the abnormal branch according to the second state may include: when the second state is that the abnormal branch is in an abnormal state, verifying the differential current information according to the following formula:

[0036]

[0037] Among them, I d_yz To verify the differential current information, is the vector current information of the i-th branch, is the vector current information of the third group of branches; according to the verified differential current information, when the verified differential current information is less than the differential current information, it is determined that the abnormal branch in the third group of branches is abnormal.

[0038] According to one aspect of the present application, a non-volatile computer-readable storage medium is also provided, on which a computer program is stored. When the computer program is executed by a processor, the current transformer polarity detection method of the multi-terminal branch differential protection device as described above can be implemented.

[0039] According to one aspect of the present application, an electronic device is also provided, comprising: one or more processors; a storage device for storing one or more programs, which, when the one or more programs are executed by the one or more processors, enables the one or more processors to implement the design method for the current transformer polarity detection method of the multi-terminal branch differential protection device as described above.

[0040] According to one aspect of the present application, a computer program product is also provided, comprising: a computer program stored on a computer-readable storage medium; the computer program comprises program instructions, which, when executed by a computer, enable the computer to execute the current transformer polarity detection method for a multi-terminal branch differential protection device as described above.

[0041] The technical solution of the present application preliminarily determines whether there is an abnormal situation in the multi-terminal branches by determining the differential current information of the multi-terminal branches and the current information of each branch, and preliminarily determines the abnormal branch by judging the relationship between the differential current information of the multi-terminal branches and the current information of each branch. After determining the abnormal branch, the abnormal situation of the abnormal branch is further determined by grouping the multi-terminal branches. After further determining the abnormal situation, the abnormal branch is verified, and finally the abnormal situation of the multi-terminal branch is determined, thereby detecting the polarity of the current transformer of the differential protection device of the multi-terminal branch.

[0042] The technical solution of the present application has a high sensitivity to the abnormal polarity of the current transformer of the differential protection device of the multi-terminal branches of the power system, and can accurately locate the device with incorrect polarity of the current transformer, thereby avoiding serious problems such as false operation or refusal to operate of the differential protection device due to incorrect polarity of the current transformer, and improving the power supply reliability.

[0043] The technical solution of the present application can monitor the polarity of the protected current transformer in real time after the multi-terminal branch differential protection device is put into operation. If the polarity of the current transformer is reversed, the position of the current transformer with reverse polarity can be quickly located without knowing the flow conditions of each branch in the multi-terminal branch and without manual judgment. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 A schematic diagram showing a multi-terminal branch;

[0046] Figure 2A schematic flow chart showing a method 1000 for detecting polarity of a current transformer of a multi-terminal branch differential protection device according to an exemplary embodiment of the present application;

[0047] Figure 3 A flow chart of step S1600 in method 1000 according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0048] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be comprehensive and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted.

[0049] The described features, structures or characteristics may be combined in one or more embodiments in any suitable manner. In the following description, many specific details are provided to provide a full understanding of the embodiments of the present disclosure. However, those skilled in the art will appreciate that the technical solutions of the present disclosure may be practiced without one or more of these specific details, or other modes, components, materials, devices, etc. may be adopted. In these cases, known structures, methods, devices, implementations, materials or operations will not be shown or described in detail.

[0050] In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units that are not listed, or may optionally include other steps or units that are inherent to these processes, methods, products or devices.

[0051] The terms "first", "second" and the like in the specification and claims of this application and the above drawings are used to distinguish different objects rather than to describe a specific order.

[0052] The following is a clear and complete description of the technical solution of the present application in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0053] Figure 1 A schematic diagram of a multi-terminal branch is shown, and the multi-terminal branch includes at least three branches. Figure 1As shown, the multi-terminal branch includes at least one load branch and at least one power supply branch. A current transformer is provided on each of the multiple branches of the multi-terminal branch. CT is a current transformer, L is a load, and D is a circuit breaker provided on each branch.

[0054] According to one aspect of the present application, a current transformer polarity detection method for a multi-terminal branch differential protection device is provided. Figure 2 FIG. 1 is a flow chart showing a method 1000 for detecting polarity of a current transformer of a multi-terminal branch differential protection device according to an exemplary embodiment of the present application. Figure 2 The current transformer polarity detection method 1000 for a multi-terminal branch differential protection device includes steps S1100 to S1800. Exemplarily, the current transformer polarity detection method 1000 for a multi-terminal branch differential protection device can be executed by a detection device.

[0055] In step S1100, maximum branch current information and differential current information of a multi-terminal branch are determined.

[0056] According to an exemplary embodiment, in step S1100, the detection device determines the maximum branch current information and differential current information of the multi-terminal branch according to the current information of the multiple branches. The maximum branch current information is the scalar sum of the current information of each branch in the multi-terminal branch; the maximum branch current information is the vector sum absolute value of the current information of each branch.

[0057] Optionally, the detection device calculates the maximum branch current information as the scalar sum of the current information of each branch in the multi-terminal branch, and calculates the maximum branch current information as the vector sum and absolute value of the current information of each branch.

[0058] For example, the detection device calculates the maximum branch current information according to the following formula:

[0059] I max =max(|I 1 |,|I 2 |,…,|I n |);

[0060] The detection device calculates the differential current information according to the following formula:

[0061]

[0062] Where i is the i-th branch in the multi-terminal branch, n is the total number of branches in the multi-terminal branch, |I i | is the scalar current information of the i-th branch, I max is the maximum branch current information, is the vector current information of the i-th branch, I d is the differential current information.

[0063] For example, Figure 1 The multi-terminal branch shown includes 7 branches, all of which are equipped with current transformers. The 7 branches include 4 load branches and 3 power supply branches. The current transformers on the 4 load branches are CT2, CT3, CT4 and CT6. L1 is the load of the 2nd branch, L2 is the load of the 3rd branch, L3 is the load of the 4th branch, and L4 is the load of the 6th branch. The current transformers on the 3 power supply branches are CT1, CT5 and CT7. D1 to D7 are circuit breakers set on the 1st branch to the 7th branch respectively.

[0064] For example, the current information of each branch may include the primary current and phase. The current transformer ratio of the seven branches is 600 / 5, and the parameter is 5P20. 1 , the primary current and phase of the 1st branch to the 7th branch are as follows:

[0065] t 1 The primary current and phase of the first branch at this moment are:

[0066] t 1 At this moment, the primary current and phase of the second branch are:

[0067] t 1 The primary current and phase of the third branch at this moment are:

[0068] t 1 At this moment, the primary current and phase of the fourth branch are:

[0069] t 1 At this moment, the primary current and phase of the fifth branch are:

[0070] t 1 At this moment, the primary current and phase of the sixth branch are:

[0071] t 1 The primary current and phase of the 7th branch at this moment are:

[0072] The detection device calculates the differential current information as:

[0073] I d =I d (t 1 )=800A;

[0074] The detection device calculates the maximum branch current information as:

[0075] I max =I max (t 1 )=1000A.

[0076] In step S1200, a first state of the differential current information is determined according to the maximum branch current information and the differential current information.

[0077] According to an exemplary embodiment, in step S1200, the detection device determines a first state of the differential current information based on the maximum branch current information and the differential current information. The first state is when the detection device preliminarily determines that the differential current information is abnormal.

[0078] Optionally, the detection device determines the first state of the differential current according to a preset condition of the differential current information, and when the differential current information is greater than the preset condition of the differential current, the detection device determines that the first state is that the differential current information meets the preset condition.

[0079] The detection device determines the preset condition of the differential current information according to the following formula:

[0080] I d_ystj =K 1 max(I N ,I max ),

[0081] Among them, I d_ystj is the precondition of differential current information, I max is the maximum branch current information, I N is the maximum rated primary current information of the current transformer, I N Depends on the type of current transformer installed. K 1 is a ratio coefficient, preferably twice the error coefficient of the current transformer, and the error coefficient of the current transformer is related to the type of the current transformer provided.

[0082] For example, K 1 It is necessary to consider both the accuracy of the current transformer and the accuracy of the sampling circuit of the differential protection device itself. The sampling circuit of the differential protection device itself includes the accuracy error of the built-in small transformer, the error caused by the filter circuit, the accuracy of the A / D analog-to-digital conversion chip, the calculation error of the protection, etc., which will affect the accuracy of the final protection action. Usually, the sampling error requirement for the differential protection device itself is less than 5%. If the accuracy of the external current transformer is also less than 5%, then the maximum superimposed deviation may reach 10%.

[0083] For example, the maximum rated primary current I of the current transformer set above is N The linear range error is less than 5%, K 1If it is determined to be 0.1, the preset condition of the differential current information calculated by the detection device is:

[0084] I d_ystj =0.1×max(600,1000)=100A.

[0085] According to an example embodiment, when the detection device determines that the differential current information is less than or equal to the preset condition of the differential current information, the detection device determines that the first state is that the differential current information does not meet the preset condition, then the detection device determines that there is no abnormality in the differential current information and the current transformer in the multi-terminal branch is not connected in reverse.

[0086] According to an example embodiment, when the detection device determines that the differential current information is greater than the preset condition of the differential current information, the detection device determines that the first state is that the differential current information meets the preset condition, and the detection device preliminarily determines that there is an abnormality in the differential current information and that the current transformer in the multi-terminal branch is connected in reverse.

[0087] For example, the detection device calculates I d =800A, I d_ystj =100A, the detection device determines that I d >I d_ystj , the detection device determines that at t 1 At time t, the first state is that the differential current information meets the preset conditions, then the detection device preliminarily determines that at t 1 There are abnormalities in the differential current information at all times, and the current transformers in the seven branches are connected in reverse.

[0088] The technical solution of the present application can preliminarily determine whether there is an abnormality in the current transformer in the multi-terminal branch by setting the preset conditions of the differential current information.

[0089] In step S1300, the differential current information change amount and the current information change amount of each branch are determined according to the current information of each branch, the differential current information and the first state.

[0090] According to an example embodiment, in step S1300, the detection device determines the differential current information change amount and the current information change amount of each branch according to the current information of each branch, the differential current information and the first state.

[0091] Optionally, when the detection device determines that the differential current information satisfies the preset conditions of the differential current, the inspection device determines that the first state of the differential current information is that the differential current information satisfies the preset conditions, and the detection device calculates the change in the differential current information and the change in the current information of each branch.

[0092] According to an example embodiment, the detection device determines that the differential current information change amount is t 2 The differential current information at time t 1 For example, the detection device calculates the change in differential current information according to the following formula:

[0093] ΔI d =I d (t 2 )-I d (t 1 );

[0094] According to an exemplary embodiment, the detection device calculates the current information change of each branch according to the following formula:

[0095]

[0096] Among them, I d (t 1 ) is t 1 The differential current information at the time, I d (t 2 ) is t 2 The differential current information at the time, ΔI d is the differential current information change, i is the i-th branch in the multi-terminal branch, t 1 The scalar current information of the i-th branch at time, t 2 The scalar current information of the i-th branch at the time, ΔI i is the current information change of the i-th branch in the multi-terminal branch. |t 2 -t 1 | is an integer multiple of the fundamental period of the current information. For example, the rated frequency of the current information of a multi-terminal branch is 50 Hz, and its fundamental period is 20 ms. 2 -t 1 | is an integer multiple of the fundamental period, so that t 2 The current information of the i-th branch at time t 1 The phase of the current information of the i-th branch at the moment is the same.

[0097] For example, the detection device takes |t 2 -t 1 | is 40ms, determine at another time t 2 The primary current and phase of the 1st to 7th branches are as follows:

[0098] t 2 The primary current and phase of the first branch at this moment are:

[0099] t 2 At this moment, the primary current and phase of the second branch are:

[0100] t 2 The primary current and phase of the third branch at this moment are:

[0101] t 2 At this moment, the primary current and phase of the fourth branch are:

[0102] t 2 At this moment, the primary current and phase of the fifth branch are:

[0103] t 2 At this moment, the primary current and phase of the sixth branch are:

[0104] t 2 The primary current and phase of the 7th branch at this moment are:

[0105] The detection device calculates t 2 The differential current information at the moment is:

[0106] I d (t 2 )=1200A.

[0107] Then the detection device calculates the primary current change and the differential current change in the current information change of each branch as follows:

[0108] The change in primary current of the first branch is: ΔI 1 =100A;

[0109] The change in primary current of the second branch is: ΔI 2 =50A;

[0110] The primary current change of the third branch is: ΔI 3 =200A;

[0111] The change in primary current of the fourth branch is: ΔI 4 =50A;

[0112] The primary current change of the fifth branch is: ΔI 5 =100A;

[0113] The primary current change of the sixth branch is: ΔI 6 =-50A;

[0114] The change in primary current of the seventh branch is: ΔI 7 =100A;

[0115] The change in differential circuit information is ΔI d =400A.

[0116] In step S1400, if it is determined that the differential current information change is twice the current information change of one and only one branch in the multi-terminal branch, then one branch is determined to be an abnormal branch.

[0117] According to an example embodiment, in step S1400, the detection device determines that the differential current information change is twice the current information change of one and only one branch in the multi-terminal branch, and then determines that one branch is an abnormal branch.

[0118] Preferably, the change in differential current information is twice the change in current information of one and only one branch in the multi-terminal branch. However, in actual applications, there may be some interference factors in the multi-terminal branch. For example, the sampling circuit of the differential protection device itself includes the accuracy error of the built-in small mutual inductor, the error caused by the filter circuit, the accuracy of the A / D analog-to-digital conversion chip, the calculation error of the protection, etc., which makes the error set by the detection device 20%. The detection device determines that the change in differential current information is 160%-240% of the change in current information of one and only one branch in the multi-terminal branch based on the change in current information of each branch and the change in differential current information, and then determines that one branch is an abnormal branch.

[0119] For example, the inspection device compares the differential current information change with the current information change of each branch to determine the differential current information change (ΔI d =400A) Figure 1 The current information change (ΔI 3 =200A), the detection device preliminarily determines that the polarity of the current transformer of the third branch may be reversed.

[0120] The technical solution of the present application can preliminarily determine that there is only one abnormal branch in a multi-terminal branch by comparing the change in differential current information with the change in current information of each branch.

[0121] In step S1500, the multi-terminal branches are grouped according to the current information of the multi-terminal branches and the current information of the abnormal branches.

[0122] According to an example embodiment, in step S1500, the detection apparatus groups the multi-terminal branches according to the current information of the multi-terminal branches and the current information of the abnormal branches.

[0123] Optionally, the detection device determines a relative current angle between current information of other branches and current information of the abnormal branch, wherein the other branches are branches of the multi-terminal branch excluding the abnormal branch.

[0124] For example, the detection device can use but is not limited to discrete Fourier transform (DFT) to calculate the phase value of the fundamental current of each branch. Taking discrete Fourier transform as an example, the detection device samples M points of the AC signal of the current information at equal intervals within the power frequency cycle, and the detection device can calculate the real part of the fundamental component of the current information by the following formula:

[0125]

[0126] The detection device can calculate the imaginary part of the fundamental component of the current information by the following formula:

[0127]

[0128] Where 1≤m≤M-1, and m is an integer, i(m) is the current sampling value of the mth sampling point, and a 1 is the real part of the fundamental component of the current information, b 1 It is the imaginary part of the fundamental component of the current information.

[0129] The detection device can calculate the phase value of the fundamental wave of the current information of each branch by the following formula:

[0130]

[0131] in, is the phase value of the fundamental wave of the current information, The value of is provided based on actual experimental data and is not given as an example in this application.

[0132] The detection device calculates the phases of the fundamental current information of the 1st branch to the 7th branch respectively: and

[0133] According to the relative angle of the current, the other branches are grouped based on the abnormal branch.

[0134] The branches satisfying -90°≤θ≤90° in other branches are determined as the first group of branches. The branches satisfying 90°<θ<270° in other branches are determined as the second group of branches. The abnormal branches are the third group of branches. Wherein, θ is the current relative angle between the phase of the current information of the abnormal branch and the phase of the current information of the abnormal branch, with the phase of the current information of the abnormal branch as the reference 0°.

[0135] For example, the detection device determines that the third branch is an abnormal branch, and determines that the other branches are the first branch, the second branch, the fourth branch, the fifth branch, the sixth branch and the seventh branch.

[0136] The phase of the third branch With 0° as the reference, the detection device calculates the current relative angle of the phase of the current information of the 1st branch, the 2nd branch, the 4th branch, the 5th branch, the 6th branch and the 7th branch and the phase of the current information of the 3rd branch according to the following formula:

[0137]

[0138] Among them, i is the i-th branch, θ i is the relative angle of the current in the i-th branch, is the phase of the fundamental current information of the i-th branch.

[0139] The detection device calculates the relative angles of the currents of the 1st branch, the 2nd branch, the 4th branch, the 5th branch, the 6th branch and the 7th branch as follows:

[0140] The current relative angle θ of the first branch 1 =0°;

[0141] The relative angle θ of the current in the second branch 2 =240°;

[0142] The current relative angle θ of the 4th branch 4 =120°;

[0143] The relative angle θ of the current in the 5th branch 5 =60°;

[0144] The current relative angle θ of the 6th branch 6 =180°;

[0145] The current relative angle θ of the 7th branch 7 =-60°.

[0146] See also Figure 1 , the current flows from the three switch stations into the distribution network lines respectively, and flows to the load side of the 2nd branch, the 3rd branch, the 4th branch, and the 6th branch. According to the relative angle of the current, the measuring device determines that the 1st branch, the 5th branch, and the 7th branch are determined as the first group of branches, the 2nd branch, the 4th branch, and the 6th branch are determined as the second group of branches, and the 3rd branch is determined as the third group of branches.

[0147] In step S1600, the vector and absolute values ​​of the current information of the branches in each group after grouping and the vector and absolute value changes of the current information are determined.

[0148] According to an example embodiment, in step S1600, the detection apparatus determines the vector and absolute values ​​of the current information of the branches of each group after grouping and the vector and absolute value changes of the current information.

[0149] Optionally, Figure 3 FIG. 1 shows a flow chart of step S1600 in method 1000 according to an embodiment of the present application, see Figure 3 , step S1600 may include steps S1610-S1630.

[0150] In step S1610, the detection device determines the vector and absolute values ​​of the current information of the first group of branches and the vector and absolute value changes of the current information.

[0151] For example, the detection device can calculate the vector and absolute value of the current information of the first group of branches according to the following formula:

[0152]

[0153] The detection device can calculate the vector and absolute value changes of the current information of the first group of branches according to the following formula:

[0154] ΔI A =I A (t 2 )-I A (t 1 );

[0155] Among them, I A is the vector and absolute value of the current information of the first group of branches, is the vector current information of the first group of branches, ΔI A is the vector and absolute value change of the current information of the first group of branches, I A (t 1 ) is t 1 The vector and absolute value of the current information of the first group of branches at time , I A (t 2 ) is t 2 The vector and absolute value of the current information of the first group of branches at time |t 2 -t 1 | is an integer multiple of the fundamental wave period of the current information.

[0156] In step S1620, the detection device determines the vector and absolute values ​​of the current information of the second group of branches and the vector and absolute value changes of the current information.

[0157] For example, the detection device can calculate the vector and absolute value of the current information of the second group of branches according to the following formula:

[0158]

[0159] The detection device can calculate the vector and absolute value changes of the current information of the second group of branches according to the following formula:

[0160] ΔI B =I B (t 2 )-I B (t 1 );

[0161] I B is the vector and absolute value of the current information of the second group of branches, is the vector current information of the second group of branches, ΔI B is the vector and absolute value change of the current information of the second group of branches, I B (t 1 ) is t 1 The vector and absolute value of the current information of the second group of branches at time , I B (t 2 ) is t 2 The vector and absolute value of the current information of the second group of branches at time |t 2 -t 1 | is an integer multiple of the fundamental wave period of the current information.

[0162] In step S1630, the detection device determines the vector absolute value of the current information of the third group of branches and the vector absolute value change of the current information.

[0163] For example, the detection device can calculate the vector and absolute value of the current information of the third group of branches according to the following formula:

[0164]

[0165] The detection device can calculate the vector and absolute value changes of the current information of the third group of branches according to the following formula:

[0166] ΔI k =I k (t 2 )-I k (t 1 );

[0167] I k is the vector and absolute value of the current information of the third group of branches, is the vector current information of the third group of branches, ΔI kis the vector and absolute value change of the current information of the third group of branches, I k (t 1 ) is t 1 The vector and absolute value of the current information of the third group of branches at time t, I k (t 2 ) is t 2 The vector and absolute value of the current information of the third group of branches at time |t 2 -t 1 | is an integer multiple of the fundamental wave period of the current information.

[0168] For example, the detection device determines that the 1st branch, the 5th branch and the 7th branch are determined as the first group of branches. The detection device calculates the vector and absolute value of the current information of the first group of branches and the vector and absolute value changes of the current information are respectively:

[0169]

[0170] ΔI A =200A.

[0171] For example, the detection device determines that the 2nd branch, the 4th branch and the 6th branch are determined as the second group of branches. The detection device calculates the vector and absolute value of the current information of the second group of branches and the vector and absolute value changes of the current information as follows:

[0172]

[0173] ΔI B =0A.

[0174] For example, the detection device determines that the third branch is a third group of branches. The detection device calculates the vector absolute value of the current information of the third group of branches and the vector absolute value change of the current information as follows:

[0175]

[0176]

[0177] ΔI k =200A.

[0178] In step S1700, the second state of the abnormal branch is determined based on the vector and absolute value changes of the current information.

[0179] According to an example embodiment, in step S1700, the detection device determines the second state of the abnormal branch according to the vector and absolute value change of the current information. The second state detection device determines the abnormal state of the abnormal branch.

[0180] Optionally, after determining the vector and absolute values ​​of the current information of each group of branches and the vector and absolute value change of the current information, the detection device judges that the second state is an abnormal branch and that the branch is in an abnormal state if the vector and absolute values ​​of the current information of each group of branches and the vector and absolute value change of the current information meet preset judgment conditions.

[0181] Among them, the preset judgment conditions are:

[0182] (1-K 2 )(ΔI k +ΔI B )<ΔI A <(1+K 2 )(ΔI k +ΔI B ),

[0183] ΔI A ΔI K >0;

[0184] Among them, K 2 is the proportionality coefficient, and 0<K 2 ≤0.2. ΔI A is the vector and absolute value change of the current information of the first group of branches, ΔI B is the vector and absolute value change of the current information of the second group of branches, ΔI k is the vector and absolute value change of the current information of the third group of branches. In the case where the first group of branches does not exist, ΔI A is 0; when the second group of branches does not exist, ΔI B is 0.

[0185] When the detection device determines that the vector and absolute value of the current information of the first group of branches, the second group of branches and the third group of branches and the vector and absolute value changes of the current information do not meet the preset judgment conditions, the detection device determines that the second state of the abnormal branch is that there is no abnormality in the abnormal branch, and the current transformer of the multi-terminal branch is not reversely connected, and the detection device continues monitoring from step S1100.

[0186] When the detection device determines that the vector and absolute values ​​of the current information of the first group of branches, the second group of branches and the third group of branches and the vector and absolute value changes of the current information meet the preset judgment conditions, the detection device determines that the second state of the abnormal branch is that the abnormal branch is in an abnormal state, and the current transformer of the multi-terminal branch is connected in reverse.

[0187] For example, the detection device determines ΔI A =200A, ΔI B =0A, ΔI k =200A, K2 =0.2. Then the detection device calculates the preset judgment condition as:

[0188] 0.8×200A<200A<1.2×200A,

[0189] 200A×200A>0.

[0190] The detection device determines that the vector and absolute values ​​of the current information of the first group of branches, the second group of branches and the third group of branches and the vector and absolute value changes of the current information meet the preset judgment conditions, then the detection device determines that the second state of the third branch is that there is an abnormality in the third branch and the current transformer of the multi-terminal branch is connected in reverse.

[0191] The technical solution of the present application can further determine the abnormal situation of the abnormal branch by preliminarily determining the abnormal branch of the multi-terminal branch and then further determining whether the abnormal branch has an abnormal situation.

[0192] In step S1800, the abnormal branch is verified according to the second state.

[0193] According to an example embodiment, in step S1800, the detection device verifies the abnormal branch according to the second state. When determining that the second state of the abnormal branch is an abnormal state of the abnormal branch and the current transformer of the multi-terminal branch is reversely connected, the detection device verifies the abnormal branch.

[0194] Optionally, when the detection device determines that the second state of the abnormal branch is that the abnormal branch is abnormal, the detection device calculates and verifies the differential current information according to the following formula:

[0195]

[0196] Among them, I d_yz To verify the differential current information, is the vector current information of the i-th branch, is the vector current information of the third group of branches;

[0197] According to the verification of the differential current information, when the verification differential current information is greater than or equal to the differential current information, it is determined that the abnormal branch in the third group of branches has no abnormality.

[0198] According to the verified differential current information, when the verified differential current information is less than the differential current information, it is determined that the abnormal branch in the third group of branches is abnormal, and the polarity of the current transformer of the abnormal branch in the third group of branches is reversed.

[0199] For example, when the detection device determines that the second state of the third branch is that the third branch is abnormal, the differential current information is calculated and verified as:

[0200]

[0201] The detection device determines I d_yz =0A, I d =800A, determine I d_yz d , it is determined that there is an abnormality in the third branch and the polarity of the current transformer in the third branch is reversed.

[0202] The technical solution of the present application preliminarily determines whether there is an abnormal situation in the multi-terminal branches by determining the differential current information of the multi-terminal branches and the current information of each branch, and preliminarily determines the abnormal branch by judging the relationship between the differential current information of the multi-terminal branches and the current information of each branch. After determining the abnormal branch, the abnormal situation of the abnormal branch is further determined by grouping the multi-terminal branches. After further determining the abnormal situation, the abnormal branch is verified, and finally the abnormal situation of the multi-terminal branch is determined, thereby detecting the polarity of the current transformer of the differential protection device of the multi-terminal branch.

[0203] The technical solution of the present application has a high sensitivity to the abnormal polarity of the current transformer of the differential protection device of the multi-terminal branches of the power system, and can accurately locate the device with incorrect polarity of the current transformer, thereby avoiding serious problems such as false operation or refusal to operate of the differential protection device due to incorrect polarity of the current transformer, and improving the power supply reliability.

[0204] The technical solution of the present application can monitor the polarity of the protected current transformer in real time after the multi-terminal branch differential protection device is put into operation. If the polarity of the current transformer is reversed, the position of the current transformer with reverse polarity can be quickly located without knowing the flow conditions of each branch in the multi-terminal branch and without manual judgment.

[0205] According to one aspect of the present application, a non-volatile computer-readable storage medium is also provided, on which a computer program is stored. When the computer program is executed by a processor, the current transformer polarity detection method of the multi-terminal branch differential protection device as described above can be implemented.

[0206] According to one aspect of the present application, an electronic device is also provided, comprising: one or more processors; a storage device for storing one or more programs, which, when the one or more programs are executed by the one or more processors, enables the one or more processors to implement the design method for the current transformer polarity detection method of the multi-terminal branch differential protection device as described above.

[0207] ​According to one aspect of the present application, a computer program product is also provided, comprising: a computer program stored on a computer-readable storage medium; the computer program comprises program instructions, which, when executed by a computer, enable the computer to execute the current transformer polarity detection method for a multi-terminal branch differential protection device as described above.

[0208] Finally, it should be noted that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Although the present application is described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions of the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for detecting polarity of a current transformer of a multi-terminal branch differential protection device, wherein the multi-terminal branch comprises at least three branches, and current transformers are arranged on the at least three branches, characterized in that: The method comprises: Determining maximum branch current information and differential current information of the multi-terminal branch; Determining a first state of the differential current information according to the maximum branch current information and the differential current information; Determine the differential current information change amount and the current information change amount of each branch according to the current information of each branch, the differential current information and the first state; If it is determined that the amount of change in the differential current information is twice the amount of change in the current information of one and only one branch in the multi-terminal branch, then the branch is determined to be an abnormal branch; According to the current information of the multi-terminal branches and the current information of the abnormal branches, the multi-terminal branches are grouped; Determine the vector and absolute value of the current information of the branches of each group after grouping and the vector and absolute value change of the current information; Determining a second state of the abnormal branch according to the vector and absolute value changes of the current information; According to the second state, the abnormal branch is verified.

2. The method according to claim 1, characterized in that The maximum branch current information is the maximum value of the effective value of the current information of each branch in the multi-terminal branch; The differential current information is the vector and absolute value of the current information of each branch.

3. The method according to claim 2, characterized in that The determining, according to the maximum branch current information and the differential current information, the first state of the differential current information comprises: In a case where the differential current information is greater than a preset condition of the differential current, determining that the first state is that the differential current information satisfies the preset condition; The preset condition of the differential current information is determined according to the following formula: I d_ystj =K1max(I N ,I max ), I d_ystj is the preset condition of the differential current information, K1 is the ratio coefficient, I max is the maximum branch current information, I N It is the maximum rated primary current information of the current transformer.

4. The method according to claim 3, characterized in that The step of determining the differential current information change amount and the current information change amount of each branch according to the current information of each branch, the differential current information and the first state comprises: When it is determined that the first state is that the differential current information satisfies the preset condition, the change amount of the differential current information is determined to be the difference between the differential current information at time t2 and the differential current information at time t1, wherein |t2-t1| is an integer multiple of the fundamental wave period of the current information; The current information change of each branch is determined according to the following formula: Wherein, i is the i-th branch in the multi-terminal branch, is the scalar current information of the i-th branch at time t1, is the scalar current information of the i-th branch at time t2, ΔI i is the change in current information of the i-th branch in the multi-terminal branch.

5. The method according to claim 4, characterized in that The grouping of the multi-terminal branches according to the current information of the multi-terminal branches and the current information of the abnormal branches comprises: Determine a current relative angle between current information of other branches and current information of the abnormal branch, wherein the other branches are branches of the multi-terminal branches excluding the abnormal branch; According to the current relative angle, the other branches are grouped with the phase of the current information of the abnormal branch as a reference 0°; Determine the branches satisfying -90°≤θ≤90° among the other branches as the first group of branches; Determine the branches satisfying 90°<θ<270° among the other branches as the second group of branches; The abnormal branch is a third group of branches; Wherein, θ is the current relative angle between the phase of the current information of the other branches and the phase of the current information of the abnormal branch, with the phase of the current information of the abnormal branch as a reference of 0°.

6. The method according to claim 5, characterized in that The determining of the vector sum absolute value of the current information of the branches of each group after grouping and the vector sum absolute value of the change amount of the current information comprises: determining vector sums of absolute values ​​of the current information of branches in the first group of branches; The vector and absolute value changes of the current information of the first group of branches are calculated according to the following formula: ΔI A =I A (t2)-I A (t1), Wherein, when the first group of branches does not exist, ΔI A is 0; determining vector sums of absolute values ​​of the current information of branches in the second group of branches; The vector and absolute value changes of the current information of the second group of branches are calculated according to the following formula: ΔI B =I B (t2)-I B (t1), Wherein, when the second group of branches does not exist, ΔI B is 0; Determining vector absolute values ​​of the current information of branches in the third group of branches; The vector absolute value change of the current information of the third group of branches is calculated according to the following formula: ΔI k =I k (t2)-I k (t1), Among them, ΔI A is the vector and absolute value change of the current information of the first group of branches, I A (t1) is the vector sum absolute value of the current information of the first group of branches at time t1, I A (t2) is the vector sum absolute value of the current information of the first group of branches at time t2, and |t2-t1| is an integer multiple of the fundamental wave period of the current information; ΔI B is the vector and absolute value change of the current information of the second group of branches, I B (t1) is the vector sum absolute value of the current information of the second group of branches at time t1, I B (t2) is the vector sum absolute value of the current information of the second group of branches at time t2; ΔI k is the vector absolute value change of the current information of the third group of branches, I k (t1) is the vector absolute value of the current information of the third group of branches at time t1, I k (t2) is the vector absolute value of the current information of the third group of branches at time t2.

7. The method according to claim 6, characterized in that The determining the second state of the abnormal branch according to the vector and absolute value change of the current information comprises: When the vector and absolute value changes of the current information of each group meet the preset determination conditions, determining that the second state is that the abnormal branch is in an abnormal state; Wherein, the preset determination condition is: (1-K2)(ΔI k +ΔI B )<ΔI A <(1+K2)(ΔI k +ΔI B ), ΔI A ΔI K >0, Wherein, K2 is the proportionality coefficient, and 0<K2≤0.

2.

8. The method according to claim 7, characterized in that The verifying the abnormal branch according to the second state includes: When the second state is that the abnormal branch is in an abnormal state, the differential current information is calculated and verified according to the following formula: Among them, I d_yz To verify the differential current information, is the vector current information of the i-th branch, is the vector current information of the third group of branches; According to the verified differential current information, when the verified differential current information is smaller than the differential current information, it is determined that the abnormal branch in the third group of branches is abnormal.

9. A non-volatile computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the current transformer polarity detection method of the multi-terminal branch differential protection device as described in any one of claims 1-8 is implemented.

10. An electronic device, characterized in that: include: one or more processors; A storage device for storing one or more programs; When the one or more programs are executed by the one or more processors, the one or more processors implement the current transformer polarity detection method for the multi-terminal branch differential protection device as described in any one of claims 1-8.

11. A computer program product, characterized in that It comprises a computer program stored on a computer-readable storage medium, wherein the computer program comprises program instructions, and when the program instructions are executed by a computer, the computer is caused to execute the current transformer polarity detection method of a multi-terminal branch differential protection device as described in any one of claims 1-8.

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