Method and device for judging loose connections in the secondary circuit terminals of power grid current transformers

Abstract

This invention relates to the field of electrical performance testing technology, specifically disclosing a method and device for judging the loose connection of the secondary circuit terminals of a power grid current transformer. The judgment method includes: repeatedly collecting current data from the secondary circuit within a set time period, calculating the average value of the collected current data and comparing it with an average reference value to determine whether the terminals of the secondary circuit are in a loose connection state. When the values ​​do not match, the dispersion of the collected current data is calculated again and compared with a dispersion reference value. The two results are then used to determine whether the terminals are loose or oxidized. This allows for the determination of whether the terminals are loose and the type of loose connection to be determined with a single data acquisition. This solves the problem in existing technologies that require collecting multiple sets of data for loose connection judgment and cannot determine the type of loose connection.

Description

Technical Field

[0001] This invention relates to the field of electrical performance testing technology, and in particular to a method and device for judging the loose connection of the secondary circuit terminals of a power grid current transformer. Background Technology

[0002] A current transformer is an instrument that measures a large primary current by converting a small secondary current into a large primary current based on the principle of electromagnetic induction. A current transformer consists of a closed iron core and windings. Its primary winding has very few turns and is connected in series with the circuit whose current needs to be measured. Therefore, it often carries the entire current of the circuit. The secondary winding has more turns and is connected in series with the measuring instrument and protection circuit. When the current transformer is working, its secondary circuit is always closed. Therefore, the impedance of the series coil of the measuring instrument and protection circuit is very small, and the operating state of the current transformer is close to a short circuit.

[0003] For example, Chinese patent CN115267621A discloses a method and device for judging the loose connection of the secondary circuit terminals of a power grid current transformer. The method includes: measuring and protecting the device to monitor the analog current of the secondary circuit of the power grid current transformer in real time; calculating the current surge and current harmonic quantity based on the analog current; determining that the terminals of the power grid current transformer are in the initial stage of loose connection when the current surge meets the preset current surge condition; and determining that the terminals of the power grid current transformer are in the later stage of loose connection when the current harmonic quantity meets the preset current harmonic condition.

[0004] However, the above solution has the following shortcomings: The patent above determines the loose connection status of the secondary circuit by calculating the voltage waveform periodicity and the current harmonic quantity in two ways. This means that after the secondary circuit of the current transformer is installed, the two calculation methods need to collect and calculate the data of the secondary circuit separately to determine whether the terminal is loose. It is impossible to determine whether the secondary circuit is loose and the type of loose connection by collecting data only once. Therefore, we have introduced a method and device for judging the loose connection of the terminal of the secondary circuit of the power grid current transformer. Summary of the Invention

[0005] The purpose of this invention is to provide a method and device for judging the loose connection of the secondary circuit terminals of a power grid current transformer, so as to solve the problems that the existing judgment of the loose connection of the secondary circuit terminals of a power grid current transformer cannot be judged by a single data acquisition and cannot determine the type of loose connection.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for judging the loose connection of the secondary circuit terminals of a power grid current transformer includes:

[0008] Step S1: Collect η sets of current data in the secondary circuit within 1 second, and calculate the average value of the collected η sets of current data.

[0009] Step S2: Compare the calculated average value with the set average reference value, and determine whether the secondary circuit wiring is in a loose connection state by comparing the two sets of values;

[0010] Step S3: When it is determined that there is a loose connection in the secondary circuit wiring, the type of loose connection in the secondary circuit is determined by calculating the dispersion of the collected current data.

[0011] Furthermore, in step S1, after collecting η sets of current data, η sets of current data will be collected again after an interval of 3-6 seconds, and the average value will be calculated. The formula for calculating the average value is:

[0012]

[0013] in, , These are the current data collected from the secondary circuit wiring, where η is the total number of current data sets collected.

[0014] Furthermore, η is 10.

[0015] Furthermore, in step S2, the average reference value is the current data collected for the first time after the secondary circuit wiring is installed and in a normal state. The collected current data is then calculated and set as the average reference value.

[0016] Furthermore, in step S3, after the secondary circuit wiring is installed and in normal condition, the initial current data is collected for the secondary circuit wiring. Several sets of current data collected are then used as a reference value for dispersion after dispersion calculation. The required connection type is determined by further calculating the dispersion of the collected current data and comparing it with the reference value. The formula for calculating the dispersion is:

[0017] S 2 = +

[0018] In the formula, , These are the current data collected from the secondary circuit wiring. It is the average of several sets of current data.

[0019] Furthermore, the specific steps for determining the type of virtual connection based on the degree of dispersion include:

[0020] After the secondary circuit wiring is installed and in normal condition, the current data of the secondary circuit wiring is collected for the first time. The dispersion of the collected current data is calculated and set as the dispersion reference value.

[0021] The dispersion reference value is compared with the dispersion of the collected current data. If the dispersion of the collected current data is greater than the dispersion reference value, it is determined that the terminal is not tightly connected. If the dispersion of the collected current data is less than or equal to the dispersion reference value, it is determined that the terminal is in a state of oxidation and loose connection.

[0022] Another technical solution of this application: a device for judging the loose connection of the secondary circuit terminals of a power grid current transformer, applied to the method for judging the loose connection of the secondary circuit terminals of a power grid current transformer described in any one of the above claims, comprising:

[0023] The data acquisition module is used to collect the current in the secondary circuit wiring multiple times over a period of time and store several sets of collected current data.

[0024] The data calculation unit is used to calculate the average value and the dispersion of several sets of current data collected. At the same time, when the secondary circuit wiring is installed and in normal condition, the unit performs the first current data collection on the secondary circuit wiring and calculates the average reference value and the dispersion reference value.

[0025] The comparison module is used to compare the calculated average with the average reference value, or to compare and judge the calculated dispersion with the dispersion reference value.

[0026] Furthermore, the data calculation unit includes an average quantity calculation module and a dispersion calculation module. The average quantity calculation module is used to calculate the average quantity and the average quantity reference value of several sets of current data collected. The dispersion calculation module is used to calculate the dispersion and the dispersion reference value of several sets of current data collected.

[0027] The beneficial effects of this invention are as follows: by collecting current in the secondary circuit multiple times within a set time period, and calculating the average value of several sets of current data after collection and comparing it with the average reference value, it can be determined whether the wiring terminal of the secondary circuit is in a loose connection state. When the values ​​do not correspond, the dispersion of several sets of current data collected will be calculated again and compared with the dispersion reference value. Based on the two results after comparison, it can be determined whether the wiring terminal is loose or oxidized. This allows for the determination of whether the wiring terminal is loose and the type of loose connection caused by a single data collection. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the judgment method of the present invention;

[0029] Figure 2 This is a schematic diagram of the process of the judgment device of the present invention;

[0030] Figure 3 This is a schematic diagram illustrating the connection relationship between the data calculation unit and the comparison module of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] It should be understood that, when used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0033] It should also be understood that the terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise.

[0034] It should also be further understood that the term "and / or" as used in this specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0035] Example 1

[0036] Please see Figure 1-3 The present invention provides a technical solution:

[0037] A method for judging the loose connection of the secondary circuit terminals of a power grid current transformer includes:

[0038] S1. Collect 10 sets of current data in the secondary circuit within 1 second, and calculate the average value of the 10 sets of current data.

[0039] S2. Compare the calculated average value with the set average reference value, and determine whether the secondary circuit wiring is in a loose connection state by comparing the two sets of values.

[0040] S3. When it is determined that there is a loose connection in the secondary circuit wiring, the type of loose connection in the secondary circuit is determined by calculating the dispersion of the collected current data.

[0041] In step S1, 10 sets of current data are collected within 1 second in the secondary circuit, and the average value of the 10 sets of current data is calculated. After collecting the 10 sets of current data, another 10 sets of current data are collected and the average value is calculated after an interval of 3-6 seconds. The specific collection time can be selected within the range of 3-6 seconds according to the actual situation. The preferred time for collecting the second 10 sets of current data is 5 seconds to reduce errors. The formula for calculating the average value is:

[0042]

[0043] in, These are the current data collected from the secondary circuit wiring. In this embodiment, the total number of current data sets collected is [number]. Take 10.

[0044] In step S2, the average reference value is set after the secondary circuit wiring is installed and in a normal state. The first current data acquisition is performed on the secondary circuit wiring. Several sets of current data are collected, and after averaging, they are set as the average reference value. After the secondary circuit wiring is connected, the data acquisition module will collect data on the current passing through the secondary circuit wiring several times over a period of time. The collected data sets are temporarily stored in the data acquisition module to ensure that a single set of data is used when calculating the average and dispersion. After collecting several sets of current data, the data acquisition module transmits them to the calculation module. The calculation module calculates the average value after receiving the current data sets. The calculated average value is transmitted to the comparison module and compared with the average reference value calculated in the normal state. When the average value does not correspond to the average reference value, it can be determined that the secondary circuit wiring is in a loose connection state.

[0045] In step S3, when a loose connection is determined in the secondary circuit wiring, the dispersion of the collected current data is calculated to determine the type of loose connection. After the secondary circuit wiring is installed and in a normal state, the initial current data is collected. Several sets of current data collected are set as dispersion reference values ​​after dispersion calculation. By calculating the dispersion of several sets of current data again and comparing them with the dispersion reference values, the type of connection required is determined. The formula for calculating the dispersion is:

[0046] S 2 = +

[0047] In the formula, , These are the current data collected from the secondary circuit wiring. It is the average of several sets of current data.

[0048] When a loose connection is detected in the secondary circuit wiring, the discreteness calculation module located in the calculation module will calculate the discreteness of several sets of current data collected. The calculated discreteness value will be transmitted to the comparison module and compared with the discreteness reference value to determine the type of loose connection of the secondary circuit wiring terminal.

[0049] For example:

[0050]

[0051] In the figure, ① represents the first six sets of current data collected under normal conditions, ② represents the current data collected when the wiring terminals became loose, and ③ represents the current data collected when the wiring terminals became oxidized. The average value of several sets of current data, The degree of dispersion;

[0052] When the secondary circuit is connected for the first time, the data acquisition module will collect data on the secondary circuit wiring multiple times over a period of time. The collected current data will be transmitted to the data calculation module for the first calculation of the average and dispersion, and set as the average reference value and dispersion reference value. When the wiring terminal becomes loose, the current data detected by the data acquisition module will be intermittent. At this time, the difference between the two sets of current data will increase, and the total dispersion calculated by the data calculation module will be much greater than the dispersion reference value. At this time, it can be determined that the wiring terminal is loose.

[0053] When the terminals are oxidized, the resistance increases and the current decreases. The current data detected at this time will be less than the current data detected under normal conditions, but the difference in the degree of dispersion between the two sets of current data remains unchanged. At this time, the total degree of dispersion calculated by the data calculation module is less than or equal to the degree of dispersion reference value, and it can be determined that the terminals are oxidized.

[0054] Preferably, the specific steps for determining the type of virtual connection based on the degree of dispersion include:

[0055] After the secondary circuit wiring is installed and in normal condition, the current data of the secondary circuit wiring is collected for the first time. The dispersion of the collected current data is calculated and set as the dispersion reference value.

[0056] The dispersion reference value is compared with the dispersion of the collected current data. If the dispersion of the collected current data is greater than the dispersion reference value, it is determined that the terminal is not tightly connected. If the dispersion of the collected current data is less than or equal to the dispersion reference value, it is determined that the terminal is in a state of oxidation and loose connection.

[0057] Example 2

[0058] A device for judging the loose connection of the secondary circuit terminals of a power grid current transformer, applied to a method for judging the loose connection of the secondary circuit terminals of a power grid current transformer including any one of the above, comprising:

[0059] The data acquisition module is used to collect the current in the secondary circuit wiring multiple times over a period of time and store several sets of collected current data.

[0060] The data calculation unit is used to calculate the average value and the dispersion of several sets of current data collected. At the same time, when the secondary circuit wiring is installed and in normal condition, the unit performs the first current data collection on the secondary circuit wiring and calculates the average reference value and the dispersion reference value.

[0061] The comparison module is used to compare the calculated average with the average reference value, or to compare and judge the calculated dispersion with the dispersion reference value.

[0062] Preferably, the data calculation unit includes an average quantity calculation module and a dispersion calculation module. The average quantity calculation module can calculate the average quantity and the average quantity reference value for several sets of current data collected. The dispersion calculation module can calculate the dispersion and the dispersion reference value for several sets of current data collected.

[0063] In summary, this invention collects current data from the secondary circuit multiple times within a set time period, calculates the average value of the collected current data, and compares it with an average reference value. This allows the system to determine whether the terminals in the secondary circuit are in a loose connection state. If the values ​​do not match, the system calculates the dispersion of the collected current data again and compares it with a dispersion reference value. The results of the comparison determine whether the terminals are loose or oxidized. This allows the system to determine whether the terminals are in a loose connection and the type of loose connection caused by a single data collection.

[0064] Those skilled in the art will recognize that the units of the various examples described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0065] In the embodiments provided in this application, it should be understood that the division of units is only a logical functional division. In actual implementation, there may be other division methods, such as multiple units can be combined into one unit, one unit can be split into multiple units, or some features can be ignored.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A method for judging the loose connection of the secondary circuit terminals of a power grid current transformer, characterized in that, include: Step S1: Collect η sets of current data in the secondary circuit within 1 second, and calculate the average value of the collected η sets of current data. Step S2: Compare the calculated average value with the set average reference value, and determine whether the secondary circuit wiring is in a loose connection state by comparing the two sets of values; Step S3: When it is determined that there is a loose connection in the secondary circuit wiring, the type of loose connection in the secondary circuit is determined by calculating the dispersion of the collected current data.

2. The method for judging the loose connection of the secondary circuit terminals of a power grid current transformer according to claim 1, characterized in that, In step S1, after collecting η sets of current data, η sets of current data will be collected again after an interval of 3-6 seconds, and the average value will be calculated. The formula for calculating the average value is: in, , These are the current data collected from the secondary circuit wiring, where η is the total number of current data sets collected.

3. The method for judging the loose connection of the secondary circuit terminals of a power grid current transformer according to claim 1, characterized in that, The value of η is 10.

4. The method for judging the loose connection of the secondary circuit terminals of a power grid current transformer according to claim 1, characterized in that, In step S2, the average reference value is the first current data acquisition of the secondary circuit wiring after it is installed and in normal condition. The collected current data is then averaged and set as the average reference value.

5. The method for judging the loose connection of the secondary circuit terminals of a power grid current transformer according to claim 1, characterized in that, In step S3, after the secondary circuit wiring is installed and in normal condition, the initial current data is collected for the secondary circuit wiring. Several sets of current data collected are then used as a reference value for dispersion after dispersion calculation. The required connection type is determined by further calculating the dispersion of the collected current data and comparing it with the reference value. The formula for calculating the dispersion is: S 2 = + In the formula, , These are the current data collected from the secondary circuit wiring. It is the average of several sets of current data.

6. The method for judging the loose connection of the secondary circuit terminals of a power grid current transformer according to claim 1, characterized in that, The specific steps for determining the type of virtual connection based on the degree of dispersion include: After the secondary circuit wiring is installed and in normal condition, the current data of the secondary circuit wiring is collected for the first time. The dispersion of the collected current data is calculated and set as the dispersion reference value. The dispersion reference value is compared with the dispersion of the collected current data. If the dispersion of the collected current data is greater than the dispersion reference value, it is determined that the terminal is not tightly connected. If the dispersion of the collected current data is less than or equal to the dispersion reference value, it is determined that the terminal is in a state of oxidation and loose connection.

7. A device for judging the loose connection of the secondary circuit terminals of a power grid current transformer, applied to the method for judging the loose connection of the secondary circuit terminals of a power grid current transformer as described in any one of claims 1-5, characterized in that, include: The data acquisition module is used to collect the current in the secondary circuit wiring multiple times over a period of time and store several sets of collected current data. The data calculation unit is used to calculate the average value and the dispersion of several sets of current data collected. At the same time, when the secondary circuit wiring is installed and in normal condition, the unit performs the first current data collection on the secondary circuit wiring and calculates the average reference value and the dispersion reference value. The comparison module is used to compare the calculated average with the average reference value, or to compare and judge the calculated dispersion with the dispersion reference value.

8. The device for judging the loose connection of the secondary circuit terminals of a power grid current transformer according to claim 7, characterized in that: The data calculation unit includes an average quantity calculation module and a dispersion calculation module. The average quantity calculation module is used to calculate the average quantity and the average quantity reference value of several sets of current data collected. The dispersion calculation module is used to calculate the dispersion and the dispersion reference value of several sets of current data collected.

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