A secondary harmonic-based main transformer CT polarity judgment method and device

Abstract

The application discloses a kind of based on secondary harmonic main transformer CT polarity determination method and device, based on secondary harmonic main transformer CT polarity determination method, comprising: in response to the start CT polarity discrimination function, and transformer high voltage side is equipped with voltage transformer, execute the CT polarity discrimination process of voltage transformer;In response to the start CT polarity discrimination function, and transformer high voltage side is not equipped with voltage transformer, execute the CT polarity discrimination process of voltage transformer without voltage transformer.The application improves the reliability and accuracy of CT polarity determination under the new energy scene such as pumped storage, nuclear power and offshore wind power, at the same time, reduces the complexity of CT polarity determination, improves the reliability of substation operation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of power system relay protection, and particularly relates to a main transformer CT polarity judgment method and device based on a second harmonic. BACKGROUND

[0002] The current loop is an important loop of relay protection, and is related to the correct action of the relay protection device and the safe and stable operation of the power system. The current transformer is an important device of the current loop, and mainly functions to convert a large current on a primary side into a small current on a secondary side according to the electromagnetic induction principle, for use by a loop device for measurement, protection and the like, and has the advantages of safety, standardization, rapidity and the like, and can timely and accurately reflect the current information of the primary side system, and plays an important role in rapidly cutting off a fault area and ensuring the reliable operation of the system. With the gradual increase of the proportion of clean energy such as wind power, photovoltaic power, nuclear power and pumped storage power stations in the power system. In the current nuclear power and other clean energy substation, pumped storage power station and offshore wind power application scenarios, when the generator set and the transformer are faulty and are removed, the standby transformer works, and if the CT polarity connection of the standby transformer branch is incorrect, the protection device will be refused or misoperated, which threatens the safe and stable operation of the substation.

[0003] In the prior art, for the conventional substation that has been put into operation, a load test is usually used to judge the correctness of the CT polarity. After each interval of the bus is put into operation, if the bus differential current is zero, the CT polarity of each interval is correct, and if the bus has a differential current, the CT polarity of the interval is incorrect. For the reconstructed and expanded substation, an independent power source is usually used to carry out a through-flow test on the primary side of the CT, and a phase table is used to test the current phase of the secondary loop, and the correctness of the CT polarity is judged according to the voltage and current angle difference displayed by the phase table. If the current phase of the secondary loop lags behind the voltage phase, and the angle difference is less than 90 degrees, it is considered that the CT polarity is correct, otherwise, it is considered that the CT polarity is incorrect. However, in the new energy scenarios such as pumped storage, nuclear power and offshore wind power, there may be no load, a very small secondary current and a long distance for the standby transformer, and therefore, the manual verification of the CT polarity of the standby transformer has low reliability and is complicated to operate, and there is a certain risk in operation, which endangers the safe and stable operation of the substation. SUMMARY

[0004] To solve the problems in the prior art, the application provides a main transformer CT polarity judgment method and device based on a second harmonic, which improves the reliability and accuracy of the CT polarity judgment in the new energy scenarios such as pumped storage, nuclear power and offshore wind power, reduces the complexity of the CT polarity judgment, and improves the reliability of the operation of the substation.

[0005] To achieve the above object, the technical scheme adopted by the present application is:

[0006] In a first aspect, a secondary harmonic-based CT polarity determination method is provided, comprising: in response to starting the CT polarity determination function and the transformer high-voltage side being configured with a voltage transformer, executing the CT polarity determination process with the voltage transformer; in response to starting the CT polarity determination function and the transformer high-voltage side not being configured with a voltage transformer, executing the CT polarity determination process without the voltage transformer.

[0007] Further, the CT polarity determination process with the voltage transformer comprises: calculating the fundamental wave and secondary harmonic content of the voltage and current of the transformer interval; in response to the secondary harmonic content being greater than a set harmonic content threshold, calculating the harmonic angle difference of the secondary harmonic voltage and the secondary harmonic current of the transformer branch; in response to the harmonic angle difference of two or more phases being less than a harmonic angle difference threshold, determining that the CT polarity of the transformer is correct; in response to the harmonic angle difference of two or more phases being greater than or equal to the harmonic angle difference threshold, determining that the CT polarity of the transformer is incorrect.

[0008] Further, in response to the secondary harmonic content being less than or equal to the set harmonic content threshold, calculating the fundamental wave angle difference of the fundamental wave voltage and the fundamental wave current of the transformer branch; in response to the fundamental wave angle difference of two or more phases being greater than a fundamental wave angle difference threshold, determining that the CT polarity of the transformer is correct; in response to the fundamental wave angle difference of two or more phases being less than or equal to the fundamental wave angle difference threshold, determining that the CT polarity of the transformer is incorrect.

[0009] Further, the harmonic content threshold is 15%; the harmonic angle difference threshold is 180°; and the fundamental wave angle difference threshold is 180°.

[0010] Further, the CT polarity determination process without the voltage transformer comprises: calculating the three-phase current fundamental wave value, three-phase current angle, and branch current angle difference of the charging branch and the transformer branch; in response to the branch current angle difference of two or more phases being greater than a branch current angle difference threshold, determining that the CT polarity of the transformer is correct; in response to the branch current angle difference of two or more phases being less than or equal to the branch current angle difference threshold, determining that the CT polarity of the transformer is incorrect.

[0011] Further, the branch current angle difference threshold is 180°.

[0012] Further, the conditions for starting the CT polarity determination function include: 1) the voltage at the high-voltage side of the transformer is normal; 2) the position of the circuit breaker at the high-voltage side of the transformer is changed from the transformer combined or the current of the transformer branch is changed from no flow to flow; wherein the determination condition for the voltage at the high-voltage side of the transformer being normal is:

[0013] ;

[0014] wherein, 、 、 V is the effective value of the A-phase, B-phase and C-phase voltage of the high-voltage side of the main transformer, V is the voltage secondary rated value, V is the zero sequence voltage of the high-voltage side of the main transformer, V is the negative sequence voltage of the high-voltage side of the main transformer;

[0015] The threshold value for changing the branch current of the main transformer from no current to current is 0.05 , V is the current secondary rated value.

[0016] In a second aspect, a main transformer CT polarity judgment device based on a secondary harmonic is provided, comprising: a CT polarity judgment module with a voltage transformer, configured to execute a CT polarity judgment process with a voltage transformer in response to starting the CT polarity judgment function, and the high-voltage side of the transformer is configured with a voltage transformer; a CT polarity judgment module without a voltage transformer, configured to execute a CT polarity judgment process without a voltage transformer in response to starting the CT polarity judgment function, and the high-voltage side of the transformer is not configured with a voltage transformer.

[0017] In a third aspect, a computer device is provided, comprising: a memory for storing instructions; and a processor for executing the instructions, so that the device executes the operations of the main transformer CT polarity judgment method based on a secondary harmonic as described in the first aspect.

[0018] In a fourth aspect, a computer readable storage medium is provided, having a computer program stored thereon, which, when executed by a processor, implements the main transformer CT polarity judgment method based on a secondary harmonic as described in the first aspect.

[0019] Compared with the prior art, the present application has the beneficial effects that: when starting the CT polarity judgment function, the present application executes the CT polarity judgment process with a voltage transformer when the high-voltage side of the transformer is configured with a voltage transformer, and executes the CT polarity judgment process without a voltage transformer when the high-voltage side of the transformer is not configured with a voltage transformer, thereby improving the reliability and accuracy of CT polarity judgment in new energy scenarios such as pumped storage, nuclear power and offshore wind power, while reducing the complexity of CT polarity judgment and improving the reliability of substation operation. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is the main flowchart of a main transformer CT polarity judgment method based on a secondary harmonic provided by the embodiments of the present application;

[0021] Figure 2 is a schematic diagram of a polarity check test in the embodiments of the present application;

[0022] Figure 3This is a schematic diagram of the CT polarity determination function of the main transformer branch 1 in an embodiment of the present invention, wherein (a) is the voltage condition, (b) is the current condition of the main transformer branch 1, and (c) is the CT polarity determination function condition.

[0023] Figure 4 These are the second harmonic waveforms of the voltage and the second harmonic waveforms of the current in the main transformer branch 1 in this embodiment of the invention (taking a 0-degree closing angle as an example); wherein, (a) is the voltage and main transformer branch current waveforms when the CT polarity is correct and the closing angle is 0 degrees; (b) is the voltage amplitude and phase angle when the CT polarity is correct and the closing angle is 0 degrees; (c) is the main transformer branch current amplitude and phase angle when the CT polarity is correct and the closing angle is 0 degrees.

[0024] Figure 5 These are the fundamental voltage and fundamental current waveforms of the main transformer branch 1 in this embodiment of the invention (taking a 60-degree closing angle as an example); where (a) is the voltage and main transformer branch current waveforms when the CT polarity is correct and the closing angle is 60 degrees; (b) is the voltage amplitude and phase angle when the CT polarity is correct and the closing angle is 60 degrees; and (c) is the main transformer branch current amplitude and phase angle when the CT polarity is correct and the closing angle is 60 degrees. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0026] Example 1

[0027] A method for determining the polarity of a transformer current transformer (CT) based on second harmonics includes: in response to activating the CT polarity determination function and a voltage transformer is configured on the high-voltage side of the transformer, executing a CT polarity determination process with a voltage transformer; in response to activating the CT polarity determination function and a voltage transformer is not configured on the high-voltage side of the transformer, executing a CT polarity determination process without a voltage transformer.

[0028] like Figures 1-5 As shown, the determination of the polarity of the main transformer CT based on the second harmonic includes the following steps.

[0029] Step 1: Obtain real-time current and voltage information for each bay and information on the high-voltage side circuit breaker of the main transformer based on the bus protection device.

[0030] Acquire current and voltage information for each interval and information about the high-voltage side circuit breakers of the main transformer. Specifically, sample the three-phase voltage and three-phase current of the main transformer branch at a constant sampling frequency to obtain the first... k Instantaneous three-phase voltage values ​​at each sampling point , , and instantaneous value of three-phase current , , The three-phase current of the charging branch is sampled at a constant sampling frequency to obtain the three-phase voltage instantaneous value and the three-phase current instantaneous value of the i-th sampling point k

[0031] Step two, determine whether the CT polarity discrimination function is started according to the position of the high-voltage side circuit breaker of the main transformer and the current and voltage information; if the CT polarity discrimination function condition is met, go to step three.

[0032] The CT polarity discrimination function, the specific starting conditions are: 1) the high-voltage side voltage of the main transformer is normal; 2) the position of the high-voltage side circuit breaker of the main transformer is changed from the substation to the main transformer, or the current of the main transformer branch is changed from no flow to flow, specifically:

[0033] (1) The high-voltage side voltage of the main transformer is normal, and the determination condition is:

[0034]

[0035] Among them, , , are the effective values of the A-phase, B-phase and C-phase voltages of the high-voltage side of the main transformer, is the voltage secondary rated value, is the zero sequence voltage of the high-voltage side of the main transformer, is the negative sequence voltage of the high-voltage side of the main transformer.

[0036] (2) The position of the high-voltage side circuit breaker of the main transformer is changed from the substation to the main transformer, or the current of the main transformer branch is changed from no flow to flow. The flow of the main transformer branch refers to:

[0037] I a > 0.05 I n , I b > 0.05 I n , I c > 0.05 I n

[0038] Among them, , , are the effective values of the A-phase, B-phase and C-phase currents of the high-voltage side of the main transformer, is the current secondary rated value. That is, the threshold value for the current of the main transformer branch to change from no flow to flow is 0.05 .

[0039] ​​​​​​Step 3: When a voltage transformer is configured on the high-voltage side of the transformer, proceed to Step 4 (i.e., in response to the activation of the CT polarity determination function and the presence of a voltage transformer on the high-voltage side of the transformer, execute the CT polarity determination process with a voltage transformer); otherwise, proceed to Step 5 (i.e., in response to the activation of the CT polarity determination function and the absence of a voltage transformer on the high-voltage side of the transformer, execute the CT polarity determination process without a voltage transformer).

[0040] Step 4: Calculate the fundamental voltage and current and second harmonic content of the main transformer interval; if the second harmonic content is greater than the harmonic content threshold (in this invention, the harmonic content threshold is set to 15%), proceed to step 6; otherwise, proceed to step 7.

[0041] The fundamental and second harmonic electrical quantities of voltage and current in the main transformer bay are calculated, and the fundamental phasor of the three-phase current is calculated using the Fourier algorithm. , , and second harmonic phasor , , and the second harmonic phasor of the three-phase current , , Specifically:

[0042] ;

[0043] ;

[0044] ;

[0045] In the formula, F 1() represents the Fourier algorithm for the fundamental frequency. F 2() is the Fourier algorithm for the second harmonic. , , These are the instantaneous current values ​​of phase A, phase B, and phase C at the k-th sampling point of the main transformer branch, respectively. , , These are the instantaneous voltage values ​​of phase A, phase B, and phase C at the kth sampling point of the main transformer branch, respectively.

[0046] The modulus of the phasor is taken to obtain the effective value of the fundamental frequency. , , and the effective value of the second harmonic , , ;

[0047] ;

[0048] The second harmonic content is calculated, specifically:

[0049] ;

[0050] Wherein, 、 、 The A-phase, B-phase, and C-phase second harmonic contents of the main transformer branch are represented by 、 、 When any of the values is greater than 0.15, the second harmonic method is used to verify the CT polarity. When 、 、 The values are all less than 0.15, the fundamental direction method is used to verify the CT polarity.

[0051] Step five: Calculate the three-phase current fundamental values and three-phase current angles of the charging branch and the main transformer branch, and use the phase comparison method to determine the CT polarity. If the two-phase and above branch current angle differences are greater than the branch current angle difference threshold value, the CT polarity of the main transformer interval is correct (i.e., in response to the two-phase and above branch current angle differences being greater than the branch current angle difference threshold value, it is determined that the main transformer CT polarity is correct). If the two-phase and above angle differences are less than or equal to the branch current angle difference threshold value, the CT polarity of the main transformer interval and the charging interval is opposite (i.e., in response to the two-phase and above branch current angle differences being less than or equal to the branch current angle difference threshold value, it is determined that the main transformer CT polarity is incorrect).

[0052] The three-phase current fundamental values and three-phase current angles of the charging branch and the main transformer branch are calculated, specifically:

[0053] The three-phase current fundamental values of the charging branch are:

[0054] ;

[0055] Wherein, 、 、 The A-phase, B-phase, and C-phase fundamental phase quantities of the charging interval are 、 、 The A-phase, B-phase, and C-phase current instantaneous values of the charging branch are

[0056] The three-phase current angles of the charging branch and the main transformer branch are:

[0057] ;

[0058] Wherein, 、 、 The A-phase, B-phase, and C-phase current angles of the main transformer interval are , , These represent the current angles of phases A, B, and C during the charging interval. This represents the phase angle calculation function.

[0059] The three-phase current angle difference between the charging branch and the main transformer branch is calculated as follows:

[0060] when Greater than , Greater than , Greater than At that time, the angle difference between the main transformer interval and the charging interval is:

[0061] ;

[0062] when Less than , Less than , Less than At that time, the angle difference between the main transformer interval and the charging interval is:

[0063] ;

[0064] in, The angle difference between the main transformer interval and the charging interval (phase A) The angle difference between the main transformer interval and the charging interval (phase B) The difference in phase C is the angle between the main transformer interval and the charging interval.

[0065] If the angle difference between the currents of two or more branches is greater than the corresponding threshold value (i.e., the branch current angle difference threshold value is set to 180° in this invention), that is... , , If at least two angle differences satisfy the following conditions, the CT polarity determination of the main variable interval is correct (i.e., the CT polarity of the main variable is correct).

[0066] ;

[0067] in, The constant is 180°. This is the threshold value for the angle difference.

[0068] If the angle difference between the currents in two or more branches is less than the corresponding threshold value, that is... , , If at least two angle differences satisfy the following conditions, the CT polarity determination of the main transformer interval and the charging interval is incorrect (i.e., the main transformer CT polarity is incorrect).

[0069] .

[0070] Step six: calculate the harmonic angle difference of the secondary harmonic voltage and the secondary harmonic current of the main transformer branch (i.e., calculate the harmonic angle difference of the secondary harmonic voltage and the secondary harmonic current of the main transformer branch in response to the secondary harmonic content being greater than the set harmonic content threshold value), if the harmonic angle difference of two or more phases is less than the corresponding harmonic angle difference threshold value, the main transformer interval CT polarity determination is correct (i.e., in response to the harmonic angle difference of two or more phases being less than the harmonic angle difference threshold value, it is determined that the main transformer CT polarity is correct). If the harmonic angle difference of two or more phases is greater than or equal to the harmonic angle difference threshold value, the CT polarity determination of the main transformer interval and the charging interval is opposite (i.e., in response to the harmonic angle difference of two or more phases being greater than or equal to the harmonic angle difference threshold value, it is determined that the main transformer CT polarity is incorrect).

[0071] The harmonic phase angle difference (i.e., harmonic angle difference) of the secondary harmonic voltage and the secondary harmonic current of the main transformer branch is calculated, which is specifically:

[0072] ;

[0073] wherein, represents the harmonic angle difference of the secondary harmonic voltage and the secondary harmonic current of the main transformer branch A phase, represents the harmonic angle difference of the secondary harmonic voltage and the secondary harmonic current of the main transformer branch B phase, represents the harmonic angle difference of the secondary harmonic voltage and the secondary harmonic current of the main transformer branch C phase.

[0074] If , , There are at least two harmonic angle differences less than 180 degrees (i.e., the harmonic angle difference threshold value is 180°), it is determined that the CT polarity of the main transformer branch is correct (i.e., the main transformer CT polarity is correct); if , , There are at least two angle differences greater than 180 degrees, it is determined that the CT polarity of the main transformer branch is incorrect (i.e., the main transformer CT polarity is incorrect).

[0075] Step 7: Calculate the fundamental angle difference between the fundamental voltage and fundamental current of the main transformer branch (i.e., in response to the second harmonic content being less than or equal to the set harmonic content threshold value, calculate the fundamental angle difference between the fundamental voltage and fundamental current of the main transformer branch). If the angle difference between two or more phases is greater than the fundamental angle difference threshold value, the polarity determination of the main transformer interval CT is correct (i.e., in response to the fundamental angle difference between two or more phases being greater than the fundamental angle difference threshold value, the determination is: the polarity of the main transformer CT is correct). If the angle difference between two or more phases is less than or equal to the fundamental angle difference threshold value, the polarity determination of the main transformer interval CT is reversed (i.e., in response to the fundamental angle difference between two or more phases being less than or equal to the fundamental angle difference threshold value, the determination is: the polarity of the main transformer CT is incorrect).

[0076] The fundamental phase angle difference between the fundamental voltage and fundamental current of the main transformer branch is calculated as follows:

[0077] ;

[0078] In the formula, This represents the fundamental angle difference between the fundamental current and the fundamental voltage of phase A in the main transformer branch. This represents the fundamental angle difference between the fundamental voltage and fundamental current of phase B in the main transformer branch. This represents the fundamental angle difference between the fundamental voltage and fundamental current of phase C in the main transformer branch.

[0079] like , , If at least two fundamental frequency angle differences are greater than 180 degrees (i.e., the fundamental frequency angle difference threshold is 180°), then the CT polarity of the main transformer branch is determined to be correct (i.e., the main transformer CT polarity is correct); if , , If there are at least two fundamental wave angle differences less than 180 degrees, it is determined that the CT polarity of the main transformer branch is incorrect (i.e., the main transformer CT polarity is incorrect).

[0080] Figure 3 for Figure 2 The logic diagram of the start conditions for the CT polarity discrimination function of the main transformer 1 bay is as follows: when the voltage of the main transformer 1 bay is normal, the circuit breaker position changes from open to closed, or the three-phase current changes from no current to current, the CT polarity discrimination function is started.

[0081] Figure 4 When the closing angle is 0°, Figure 2 According to the method of this invention, the second harmonic waveforms of the voltage and current in the first branch of the main transformer are such that the second harmonic content is greater than 0.15. The polarity of the transformer current transformer (CT) in the transformer branch is determined by the angular relationship between the second harmonic current and the second harmonic voltage. , , The angle difference is less than 180 degrees, and it is determined that the CT polarity of the main transformer branch is correct.

[0082] Figure 5 For the closing angle of 60 degrees, Figure 2 The secondary harmonic content of the main transformer 1 branch voltage secondary harmonic and the current secondary harmonic waveform is greater than 0.15 according to the method of the application, the secondary harmonic current and the secondary harmonic voltage angle relationship is used to determine the CT polarity of the transformer branch, 、 、 The angle difference is also less than 180 degrees, and it is determined that the CT polarity of the main transformer branch is correct.

[0083] The application first acquires the voltage and current information of each interval and the main transformer interval circuit breaker information in real time, calculates the secondary harmonic content of the main transformer interval current information, and judges whether the secondary harmonic content exceeds the threshold value. Secondly, based on the main transformer high voltage side circuit breaker position change information or current change characteristic, the main transformer branch voltage information is used to determine whether to start the CT polarity discrimination function; finally, based on the configuration of the voltage transformer on the high voltage side of the main transformer, the secondary harmonic content of the main transformer interval and the secondary harmonic and the base wave current and the corresponding voltage phase angle difference characteristic or the charging branch and the main transformer interval current angle difference characteristic are used to discriminate the CT polarity of the main transformer. Compared with the prior art, the application can effectively utilize the largest secondary harmonic component in the excitation inrush current, adapt to the secondary harmonic of the excitation inrush current and integrate the base wave CT polarity direction, solve the low reliability and complexity of artificial verification of the CT polarity of the standby transformer in the new energy scene such as pumped storage, nuclear power and offshore wind power, and improve the operation reliability of the transformer substation.

[0084] Embodiment two

[0085] Based on the secondary harmonic-based main transformer CT polarity judgment method of embodiment one, the application provides a secondary harmonic-based main transformer CT polarity judgment device, which comprises: a CT polarity discrimination module with a voltage transformer, which is used to respond to the start of the CT polarity discrimination function and execute the CT polarity discrimination process with the voltage transformer when the transformer high voltage side is configured with a voltage transformer; and a CT polarity discrimination module without a voltage transformer, which is used to respond to the start of the CT polarity discrimination function and execute the CT polarity discrimination process without a voltage transformer when the transformer high voltage side is not configured with a voltage transformer.

[0086] Embodiment three

[0087] Based on the secondary harmonic-based main transformer CT polarity judgment method of embodiment one, the application provides a computer device, which comprises: a memory for storing instructions; and a processor for executing the instructions, so that the device executes the operations of the secondary harmonic-based main transformer CT polarity judgment method of embodiment one.

[0088] Embodiment Four

[0089] Based on the secondary harmonic-based CT polarity judgment method of the transformer of embodiment one, the embodiment provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to realize the secondary harmonic-based CT polarity judgment method of the transformer of embodiment one.

[0090] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROMs, optical storage, etc.) containing computer-usable program code.

[0091] The present application is described with reference to flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing apparatus to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing apparatus produce a device that implements the flow Figure 1 one or more flows and / or blocks Figure 1 an apparatus with the function specified in one or more blocks.

[0092] These computer program instructions can also be stored in a computer-readable memory that can direct the computer or other programmable data processing apparatus to work in a specific manner, so that the instructions stored in the computer-readable memory produce a manufactured product including instruction apparatus, which implements the flow Figure 1 one or more flows and / or blocks Figure 1 an apparatus with the function specified in one or more blocks.

[0093] These computer program instructions can also be loaded into a computer or other programmable data processing apparatus, so that a series of operation steps are performed on the computer or other programmable data processing apparatus to produce a computer-implemented process, so that the instructions executed on the computer or other programmable data processing apparatus provide a process for implementing the flow Figure 1 one or more flows and / or blocks Figure 1 an apparatus with the function specified in one or more blocks.

[0094] The embodiments of the present application are described above with reference to the accompanying drawings, but the present application is not limited to the above-described specific embodiments, and the above-described specific embodiments are merely illustrative, but not restrictive, and a person of ordinary skill in the art can make many forms under the inspiration of the present application without departing from the purpose of the present application and the scope protected by the claims, and these all belong to the protection of the present application.

Claims

1. A method for determining the polarity of a main variable CT based on second harmonics, characterized in that, include: In response to the activation of the CT polarity determination function, and given that a voltage transformer is configured on the high-voltage side of the transformer, the CT polarity determination process with the voltage transformer is executed. In response to the activation of the CT polarity determination function, and since no voltage transformer is configured on the high-voltage side of the transformer, the CT polarity determination process without a voltage transformer is executed. The voltage transformer (CT) polarity determination process includes: Calculate the fundamental and second harmonic content of the voltage and current in the main transformer bay; In response to the second harmonic content exceeding the set harmonic content threshold, the harmonic angle difference between the second harmonic voltage and the second harmonic current of the main transformer branch is calculated. If the harmonic angle difference between two or more phases is less than the harmonic angle difference threshold, it is determined that the polarity of the main transformer CT is correct. If the harmonic angle difference between two or more phases is greater than or equal to the harmonic angle difference threshold, it is determined that the main transformer CT polarity is incorrect. In response to the second harmonic content being less than or equal to a set harmonic content threshold, the fundamental angle difference between the fundamental voltage and fundamental current of the main transformer branch is calculated. If the fundamental angle difference between two or more phases is greater than the fundamental angle difference threshold, it is determined that the polarity of the main transformer CT is correct. If the fundamental angle difference between two or more phases is less than or equal to the fundamental angle difference threshold, it is determined that the main transformer CT polarity is incorrect. The CT polarity determination process without voltage transformers includes: Calculate the fundamental values ​​of the three-phase currents, the three-phase current angles, and the branch current angle differences for the charging branch and the main transformer branch; If the angle difference between two or more phase branch currents is greater than the branch current angle difference threshold, it is determined that the polarity of the main transformer CT is correct. If the angle difference between the currents of two or more phases is less than or equal to the threshold value of the angle difference between the currents of the two phases, it is determined that the polarity of the main transformer CT is incorrect.

2. The method for determining the polarity of a main variable CT based on second harmonics according to claim 1, characterized in that, The threshold values ​​for harmonic content are 15%; the threshold values ​​for harmonic angle difference are 180°; and the threshold values ​​for fundamental frequency angle difference are 180°.

3. The method for determining the polarity of a main variable CT based on second harmonics according to claim 1, characterized in that, The threshold value for the branch current angle difference is 180°.

4. The method for determining the polarity of a main variable CT based on second harmonics according to claim 1, characterized in that, To activate the CT polarity determination function, the following conditions must be met: 1) The voltage on the high-voltage side of the main transformer is normal; 2) The position of the circuit breaker on the high-voltage side of the main transformer changes from open to closed, or the current in the main transformer branch changes from zero to current. The criteria for determining normal voltage on the high-voltage side of the main transformer are as follows: ； in, , , The effective values ​​of phase A, phase B, and phase C voltages on the high-voltage side of the main transformer. This is the secondary voltage rating. The zero-sequence voltage on the high-voltage side of the main transformer. The negative sequence voltage on the high-voltage side of the main transformer; The threshold value for the main transformer branch current to change from zero to current is 0.

05. , This is the secondary rated value of the current.

5. A polarity determination device for a main variable CT based on second harmonics, characterized in that, include: A CT polarity determination module with a voltage transformer is used to respond to the activation of the CT polarity determination function, and the high-voltage side of the transformer is equipped with a voltage transformer to execute the CT polarity determination process with the voltage transformer. The CT polarity determination module without voltage transformer is used to execute the CT polarity determination process in response to the activation of the CT polarity determination function and the absence of a voltage transformer on the high-voltage side of the transformer. The voltage transformer (CT) polarity determination process includes: Calculate the fundamental and second harmonic content of the voltage and current in the main transformer bay; In response to the second harmonic content exceeding the set harmonic content threshold, the harmonic angle difference between the second harmonic voltage and the second harmonic current of the main transformer branch is calculated. If the harmonic angle difference between two or more phases is less than the harmonic angle difference threshold, it is determined that the polarity of the main transformer CT is correct. If the harmonic angle difference between two or more phases is greater than or equal to the harmonic angle difference threshold, it is determined that the main transformer CT polarity is incorrect. In response to the second harmonic content being less than or equal to a set harmonic content threshold, the fundamental angle difference between the fundamental voltage and fundamental current of the main transformer branch is calculated. If the fundamental angle difference between two or more phases is greater than the fundamental angle difference threshold, it is determined that the polarity of the main transformer CT is correct. If the fundamental angle difference between two or more phases is less than or equal to the fundamental angle difference threshold, it is determined that the main transformer CT polarity is incorrect. The CT polarity determination process without voltage transformers includes: Calculate the fundamental values ​​of the three-phase currents, the three-phase current angles, and the branch current angle differences for the charging branch and the main transformer branch; If the angle difference between two or more phase branch currents is greater than the branch current angle difference threshold, it is determined that the polarity of the main transformer CT is correct. If the angle difference between the currents of two or more phases is less than or equal to the threshold value of the angle difference between the currents of the two phases, it is determined that the polarity of the main transformer CT is incorrect.

6. A computer device, characterized in that, include: Memory, used to store instructions; A processor is configured to execute the instructions, causing the device to perform operations that implement the second harmonic-based main transformer CT polarity determination method as described in any one of claims 1 to 4.

7. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the main variable CT polarity determination method based on second harmonics as described in any one of claims 1 to 4.

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