Characteristic current sampling circuit for topology identification of low-voltage transformer area
By designing a feature current sampling circuit in the low-voltage table topology recognition system, and sampling the feature current using RCL parallel circuit, the problems of feature current attenuation and high transmission power are solved, the recognition rate and continuous working time are improved, and the cooling time and heat dissipation are reduced. Require.
Patent Information
- Application Number
- CN202411607006.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-12
- Publication Date
- 2025-02-14
AI Technical Summary
In the low-voltage table topological identification system, the attenuation of characteristic current and high transmit power lead to difficulty in receiving, low recognition rate and overheating of the transmission circuit, which requires a long time to cool.
A characteristic current sampling circuit for topology recognition of low-voltage table area is designed, using current transformer, characteristic current filter and sampling resistor. The characteristic current filter is an RCL parallel circuit. The characteristic current is sampled through the parallel resonant circuit to increase the RCL parallel circuit. the resistance value in order to reduce the characteristic current.
It improves the sensitivity of characteristic current sampling, reduces characteristic current value and transmission power, shortens cooling time, extends continuous working time, and reduces the geometric size and heat dissipation requirements of the transmission equipment.
Smart Images
Figure CN119438678A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the field of electric power technology, and in particular relates to a characteristic current sampling circuit for low-voltage station area topology identification. Background Art
[0002] Figure 2 This is a schematic diagram of the low-voltage substation topology identification system. The measurement switch current specification on the substation transformer side is large, and the current transformer ratio used is also large. At this time, the characteristic current emitted by the sending device is attenuated by the current transformer, which makes it difficult for the low-voltage substation transformer side with larger capacity to receive the characteristic current, reducing the identification rate.
[0003] On the other hand, the effective value of the phase voltage of the power line in the low-voltage substation is 220V. Even if the effective value of the characteristic current is below the required value, the power of the characteristic current transmitting circuit ranges from tens of watts to hundreds of watts. The transmitting circuit generates a lot of heat when transmitting the characteristic current. Under the conditions of a modulation frequency of 833.3Hz, a bit width of 600ms, and a duty cycle of 1 / 3, the effective value of the characteristic current when the characteristic code bit is 1 is 0.21A. After transmitting the characteristic current (transmission duration 9.6 seconds), it takes at least 3 minutes of cooling time before the characteristic current can be sent again. Summary of the invention
[0004] Purpose of the invention: The technical problem to be solved by the present invention is to provide a characteristic current sampling circuit for low-voltage station area topology identification in view of the deficiencies in the prior art.
[0005] In order to solve the above technical problems, in the first aspect, a characteristic current sampling circuit for low-voltage substation topology identification is disclosed, including a current transformer, a characteristic current filter and a sampling resistor, the primary side of the current transformer receives the current sent by the transmitting device, and the secondary side is connected to the characteristic current filter and the sampling resistor, the current includes the characteristic current and the power frequency current; the characteristic current filter is used to collect the characteristic current, and the sampling resistor is used to collect the characteristic current or the power frequency current; the characteristic current is converted into a sampling voltage after passing through the characteristic current filter and the sampling resistor, which is used for low-voltage substation topology identification.
[0006] Furthermore, the characteristic current filter is an RCL parallel circuit. Using a parallel resonant circuit to sample the characteristic current takes into account both the metering function, the power frequency current sampling, and the topology identification function. The characteristic current sampling requires different sampling resistors.
[0007] Furthermore, the impedance of the RCL parallel circuit is calculated as follows:
[0008] The admittance Y of the RCL parallel circuit is:
[0009] Y=G R +jB C-jB L
[0010] in: B C =2πfC, R, C and L represent the resistance, capacitance and inductance in the RCL parallel circuit respectively, and f represents the characteristic current signal frequency;
[0011] Then the impedance Z of the RCL parallel circuit is:
[0012]
[0013] When B C =B L ,Right now When , the impedance Z of the RCL parallel circuit is the resistance value in the RCL parallel circuit.
[0014] Further, in an optional implementation, the characteristic current filter is connected in series with a sampling resistor.
[0015] Further, in another optional implementation, the current transformer includes a first current transformer and a second current transformer, the secondary side of the first current transformer is connected to a current filter, and the secondary side of the second current transformer is connected to a sampling resistor.
[0016] Furthermore, when the characteristic current filter is connected in series with the sampling resistor, the sampling voltage The calculation is as follows:
[0017]
[0018] in, Indicates the characteristic current sent by the sending device, Represents the characteristic current after passing through the current transformer, R S represents the sampling resistance value, and n represents the current transformer ratio.
[0019] Further, when the current transformer includes a first current transformer and a second current transformer, the sampled voltage is calculated as follows:
[0020]
[0021] in, Represents the sampling voltage of the characteristic current passing through the first current transformer and the RCL parallel circuit, Indicates the characteristic current sent by the sending device, represents the characteristic current after passing through the first current transformer, and n1 represents the transformation ratio of the first current transformer. When there are multiple sampling channels, one sampling channel can be used alone to collect the characteristic current.
[0022] Furthermore, when When the resistance value in the RCL parallel circuit is increased, the characteristic current sent by the transmitting device can be reduced. This improves the characteristic current receiving sensitivity, reduces the characteristic current sending power, shortens the cooling time of the transmitting circuit, and prolongs the continuous working time of the transmitting circuit.
[0023] In a second aspect, a low-voltage substation topology identification system is disclosed, including a sending device and an identification device, wherein the sending device and the identification device are connected via a power line, and the identification device includes a characteristic current sampling circuit for low-voltage substation topology identification.
[0024] In a third aspect, a low-voltage area topology identification method is disclosed, and the low-voltage area topology identification system is applied, including the following steps:
[0025] The sending device generates a characteristic current containing a characteristic code and feeds it into the power line;
[0026] The identification equipment on the power line samples the current signal to obtain the characteristic current, and calculates and extracts the characteristic code at the characteristic current frequency point;
[0027] The sending device and the identifying device are matched according to the time of sending and identifying the characteristic current and the characteristic code information, and the topological relationship between the sending device and the identifying device is determined.
[0028] Beneficial effects: Improve the sensitivity of characteristic current sampling in low-voltage area topology identification, reduce characteristic current, reduce characteristic current transmission power, and reduce the temperature rise of the sending module. The reduction of characteristic current transmission power can shorten the cooling time of the sending circuit, extend the continuous transmission time, and increase the transmission of characteristic codes per unit time. At the same time, the geometric size and heat dissipation requirements of the sending equipment are also reduced accordingly. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more clear.
[0030] Figure 1 It is a system model for low voltage area topology identification.
[0031] Figure 2 This is a schematic diagram of the low-voltage area topology identification system.
[0032] Figure 3 It is the characteristic current waveform of constant resistance load.
[0033] Figure 4 It is the characteristic current waveform of constant current load.
[0034] Figure 5This is a schematic diagram of the current sampling circuit.
[0035] Figure 6 Schematic diagram of characteristic current signal spectrum.
[0036] Figure 7 It is an RCL parallel circuit.
[0037] Figure 8 Schematic diagram of characteristic current sampling circuit Figure 1 .
[0038] Fig. 9 Schematic diagram of characteristic current sampling circuit Figure 2 . DETAILED DESCRIPTION
[0039] The embodiments of the present invention will be described below in conjunction with the accompanying drawings.
[0040] Relevant standards such as "General Technical Specifications for Intelligent Fusion Terminals in Substations 2022", "Technical Specifications for Intelligent Measuring Switches 2022", and "General Technical Specifications for Type I Concentrators 2022" all have technical requirements for identifying substation electrical topology, namely: the terminal aggregates node data or characteristic signals on the substation side, line side, and user side to identify the electrical connection relationship of equipment at all levels in the substation, and form a topological relationship covering all electrical equipment in the substation.
[0041] The low voltage area topology identification system model is as follows Figure 1 As shown, it includes a sending device and an identification device, and performs the following steps:
[0042] B-1. The transmitting device (including the device integrating the transmitting and identifying functions) generates a characteristic current containing a characteristic code and feeds it into the power line.
[0043] B-2. The identification equipment on the power line (including equipment with integrated transmission and identification functions) samples the current signal and calculates and extracts the characteristic code at a specific frequency point.
[0044] B-3. Match the sending device and the identifying device according to the time of sending and identifying the characteristic current and the characteristic code information, and determine the topological relationship between the sending device and the identifying device.
[0045] Low voltage area topology identification system Figure 2 As shown,
[0046] Typical characteristic current signal parameters are shown in Table 1, where the constant resistance load characteristic current waveform is as follows: Figure 3 As shown, the characteristic current waveform of the constant current load is as follows Figure 4 shown.
[0047] Table 1 Characteristic current signal parameters
[0048]
[0049] Characteristic current sampling circuit such as Figure 5 As shown, a differential input method is adopted, and a current transformer is used for current sampling. The characteristic current sent by the sending device is recorded as The characteristic current after passing through the current transformer is Through the sampling resistor R S After that, it is converted into a differential AC sampling voltage signal and
[0050] The current transformer ratio is defined as but The sampling voltage of the metering chip is:
[0051]
[0052] right Perform harmonic analysis and calculate and extract characteristic codes at specific frequency points. Figure 6 is the characteristic current signal spectrum.
[0053] The measurement switch (circuit breaker or branch switch) current transformer ratio is shown in Table 2:
[0054] Table 2 Transformer parameters
[0055]
[0056] like Figure 2 As shown, the current specification of the measuring switch (branch switch) on the transformer side of the substation is large. According to Table 2, the current transformer ratio used in the switch is also large. From formula ①, it can be seen that the characteristic current sent by the sending device is attenuated by the current transformer. This makes it difficult for the low-voltage transformer side with a larger capacity to receive the characteristic current, reducing the recognition rate.
[0057] On the other hand, the effective value of the phase voltage of the power line in the low-voltage substation is 220V. Even if the effective value of the characteristic current is below 0.21A (Table 1), the power of the characteristic current transmitting circuit ranges from tens of watts to hundreds of watts. The transmitting circuit generates a lot of heat when transmitting the characteristic current. According to the parameters shown in Table 1, after transmitting the characteristic current (transmission duration 9.6 seconds), at least 3 minutes of cooling time is required before it can be transmitted again.
[0058] The embodiment of the present invention provides a characteristic current sampling circuit for low-voltage area topology identification, which can improve the sensitivity of characteristic current sampling, thereby reducing the characteristic current value, reducing the transmission time, shortening the cooling time, and sending more information under the same energy condition. It can be applied to application scenarios such as type I concentrators and measuring switches (such as molded case circuit breakers) that require low-voltage area topology identification functions.
[0059] The first embodiment of the present application discloses a characteristic current sampling circuit for low-voltage substation topology identification, including a current transformer, a characteristic current filter and a sampling resistor. The primary side of the current transformer receives the current sent by the transmitting device, and the secondary side is connected to the characteristic current filter and the sampling resistor. The current includes a characteristic current and an industrial frequency current; the characteristic current filter is used to collect the characteristic current, and the sampling resistor is used to collect the characteristic current or the industrial frequency current; the characteristic current is converted into a sampling voltage after passing through the characteristic current filter and the sampling resistor, which is used for low-voltage substation topology identification.
[0060] The characteristic current filter is an RCL parallel circuit.
[0061] like Figure 7 As shown, the admittance of the RCL parallel circuit is:
[0062] Y=G R +jB C -jB L
[0063] in: B C =2πfC, R, C and L represent the resistance, capacitance and inductance in the RCL parallel circuit respectively, and f represents the characteristic current signal frequency;
[0064] Then the impedance of the RCL parallel circuit is:
[0065]
[0066] When B C =B L ,Right now When , the impedance Z of the RCL parallel circuit is the resistance value in the RCL parallel circuit.
[0067] In an optional implementation, Figure 8 As shown, the characteristic current filter is connected in series with the sampling resistor.
[0068] The sampling voltage The calculation is as follows:
[0069]
[0070] Where: Z S It represents the sum of the impedance of the RCL parallel circuit and the impedance of the sampling resistor.
[0071] In another optional implementation, such as Fig. 9As shown, the current transformer includes a first current transformer and a second current transformer, the secondary side of the first current transformer is connected to a current filter, and the secondary side of the second current transformer is connected to a sampling resistor. The channel of the secondary side of the first current transformer connected to the current filter is used to receive the characteristic current, and the channel of the secondary side of the second current transformer connected to the sampling resistor is used to receive the power frequency circuit.
[0072] The characteristic current is converted into a sampling voltage after passing through the characteristic current filter and the sampling resistor. The sampling voltage is calculated as follows:
[0073]
[0074] in, Represents the sampling voltage of the characteristic current passing through the first current transformer and the RCL parallel circuit, Indicates the characteristic current sent by the sending device, represents the characteristic current after passing through the first current transformer, and n1 represents the transformation ratio of the first current transformer
[0075] The sampling voltage of the power frequency current passing through the second current transformer and the sampling resistor The calculation is as follows:
[0076]
[0077] in, Represents the power frequency current after passing through the second current transformer, Indicates the power frequency current sent by the sending device, R S represents the sampling resistance value, and n2 represents the transformation ratio of the second current transformer.
[0078] According to formula ② or ③, when B C =B L ,Right now When , the amplitude of the sampling voltage is the largest. Increasing the resistance value in the RCL parallel circuit can reduce the characteristic current sent by the sending device.
[0079] The second embodiment of the present application discloses a low-voltage substation topology identification system, including a sending device and an identification device, wherein the sending device and the identification device are connected via a power line, and the identification device includes the characteristic current sampling circuit for low-voltage substation topology identification.
[0080] The third embodiment of the present application discloses a low-voltage area topology identification method, which is applied to a low-voltage area topology identification system, and includes the following steps:
[0081] The sending device generates a characteristic current containing a characteristic code and feeds it into the power line;
[0082] The identification equipment on the power line samples the current signal to obtain the characteristic current, and calculates and extracts the characteristic code at the characteristic current frequency point;
[0083] The sending device and the identifying device are matched according to the time of sending and identifying the characteristic current and the characteristic code information, and the topological relationship between the sending device and the identifying device is determined.
[0084] In a specific implementation, the present application provides a computer storage medium and a corresponding data processing unit, wherein the computer storage medium can store a computer program, and when the computer program is executed by the data processing unit, the invention content of a low-voltage area topology identification method provided by the present invention and some or all of the steps in each embodiment can be run. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.
[0085] Those skilled in the art can clearly understand that the technical solutions in the embodiments of the present invention can be implemented by means of computer programs and their corresponding general hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention are essentially or partly contributed to the prior art can be embodied in the form of a computer program, i.e., a software product, which can be stored in a storage medium and includes several instructions for enabling a device including a data processing unit (which can be a personal computer, a server, a single-chip microcomputer, a MUU or a network device, etc.) to execute the methods described in various embodiments of the present invention or certain parts of the embodiments.
[0086] The present invention provides a method and idea of a characteristic current sampling circuit for low-voltage station topology identification. There are many methods and ways to implement the technical solution. The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention. All components not specified in this embodiment can be implemented using existing technologies.
Claims
1. A characteristic current sampling circuit for low voltage station area topology identification, characterized in that: It includes a current transformer, a characteristic current filter and a sampling resistor, wherein the primary side of the current transformer receives the current sent by the transmitting device, and the secondary side is connected to the characteristic current filter and the sampling resistor, and the current includes the characteristic current and the power frequency current; The characteristic current filter is used to collect characteristic current, and the sampling resistor is used to collect characteristic current or power frequency current; The characteristic current is converted into a sampling voltage after passing through a characteristic current filter and a sampling resistor, and is used for low-voltage station area topology identification.
2. A characteristic current sampling circuit for low voltage area topology identification according to claim 1, characterized in that: The characteristic current filter is an RCL parallel circuit.
3. A characteristic current sampling circuit for low voltage station area topology identification according to claim 2, characterized in that: The impedance of the RCL parallel circuit is calculated as follows: The admittance Y of the RCL parallel circuit is: Y=G R +jB C -jB L in: B C =2πfC, R, C and L represent the resistance, capacitance and inductance in the RCL parallel circuit respectively, and f represents the characteristic current signal frequency; Then the impedance Z of the RCL parallel circuit is: When B C =B L ,Right now When , the impedance Z of the RCL parallel circuit is the resistance value in the RCL parallel circuit.
4. A characteristic current sampling circuit for low voltage area topology identification according to claim 3, characterized in that: The characteristic current filter is connected in series with the sampling resistor.
5. The characteristic current sampling circuit for low voltage area topology identification according to claim 3 is characterized in that: The current transformer comprises a first current transformer and a second current transformer, the secondary side of the first current transformer is connected to a current filter, and the secondary side of the second current transformer is connected to a sampling resistor.
6. A characteristic current sampling circuit for low voltage area topology identification according to claim 4, characterized in that: The characteristic current is converted into a sampling voltage after passing through a characteristic current filter and a sampling resistor. The calculation is as follows: in, Indicates the characteristic current sent by the sending device, Represents the characteristic current after passing through the current transformer, R S represents the sampling resistance value, and n represents the current transformer ratio.
7. The characteristic current sampling circuit for low voltage area topology identification according to claim 5, characterized in that: The characteristic current is converted into a sampling voltage after passing through the characteristic current filter and the sampling resistor. The sampling voltage is calculated as follows: in, Represents the sampling voltage of the characteristic current passing through the first current transformer and the RCL parallel circuit, Indicates the characteristic current sent by the sending device, represents the characteristic current after passing through the first current transformer, and n1 represents the transformation ratio of the first current transformer.
8. A characteristic current sampling circuit for low voltage station area topology identification according to claim 6 or 7, characterized in that: when When increasing the resistance value in the RCL parallel circuit, the characteristic current sent by the sending device can be reduced.
9. A low voltage area topology identification system, characterized in that: It comprises a sending device and an identification device, wherein the sending device and the identification device are connected via a power line, and the identification device comprises a characteristic current sampling circuit for low-voltage area topology identification as claimed in any one of claims 1 to 8.
10. A low voltage area topology identification method, applied to the low voltage area topology identification system according to claim 9, characterized in that: The following steps are involved: The sending device generates a characteristic current containing a characteristic code and feeds it into the power line; The identification equipment on the power line samples the current signal to obtain the characteristic current, and calculates and extracts the characteristic code at the characteristic current frequency point; The sending device and the identifying device are matched according to the time of sending and identifying the characteristic current and the characteristic code information, and the topological relationship between the sending device and the identifying device is determined.