A test circuit for mutual inductance parameters of a double-circuit line with incomplete stop

Abstract

This invention discloses a test circuit for mutual inductance parameters of a double-circuit power line under partial outage conditions, belonging to the field of power system testing technology. It includes a signal excitation unit, a coupling simulation unit, a signal acquisition unit, and a signal processing unit. The signal excitation unit provides a different frequency test signal to the first line and a power frequency operating signal to the second line; the coupling simulation unit is connected between the first and second lines to simulate the electromagnetic coupling characteristics between the two lines; the signal acquisition unit synchronously acquires the voltage and current signals of the double-circuit power line; and the signal processing unit calculates the mutual inductance parameters. This invention achieves high-precision parameter testing of double-circuit power lines under partial outage conditions, with a measurement error of less than 1%, effectively solving the technical problem of requiring a complete power outage in traditional methods.

Description

Technical Field

[0001] This utility model relates to the field of power system testing technology, and in particular to a test circuit for mutual inductance parameters of a double-circuit line incomplete outage. Background Technology

[0002] In power systems, accurate measurement of mutual inductance parameters of double-circuit transmission lines is crucial for system safety and stable operation. Traditional testing methods require a complete power outage, affecting power supply reliability; in existing technologies, the power frequency interference method is susceptible to environmental interference, leading to large measurement errors. The solution described in this document achieves high-precision measurement under "partial power outage" conditions through the design of a dedicated test circuit, but existing publicly available technologies lack dedicated protection for this circuit structure. Based on the schematic diagram in this document, this utility model optimizes the circuit connection relationship and provides a test circuit with a clear structure and easy implementation, solving the efficiency and accuracy problems in field applications. Utility Model Content

[0003] The purpose of this invention is to provide a test circuit for mutual inductance parameters of a double-circuit line under partial power outage, which overcomes the drawback of traditional test circuits requiring power outage. This circuit has a simple connection structure and high reliability, and can accurately measure the mutual inductance parameters of a double-circuit line under partial power outage conditions.

[0004] To achieve the above objectives, this utility model provides a test circuit for mutual inductance parameters of a double-circuit line with incomplete outage, comprising: The signal excitation unit is used to provide a different frequency test signal to the first line and a power frequency operation signal to the second line; A coupling simulation unit is connected between the first line and the second line to simulate the electromagnetic coupling characteristics between the two lines. The signal acquisition unit is configured to synchronously acquire voltage and current signals on the first and second lines; A signal processing unit, connected to the signal acquisition unit, is used to calculate the mutual inductance parameters of the line based on the acquired voltage and current signals. The first line is configured as a power outage test line, and the second line is configured as a normal operation line. The two lines are electromagnetically coupled and electrically isolated through the coupling simulation unit.

[0005] Preferably, the signal excitation unit includes a variable frequency power supply S1 and a power frequency power supply. The output terminal of the variable frequency power supply S1 is connected to the first terminal node A of the first line, and the power frequency power supply is connected to the first terminal node C of the second line through a voltage transformer PT.

[0006] Preferably, the variable frequency power supply S1 is a vector control frequency converter with an adjustable output frequency range of 45Hz to 55Hz.

[0007] Preferably, the coupling simulation unit includes an isolation transformer, the primary winding of which is connected between the first end node A and the last end node B of the first line, and the secondary winding is connected between the first end node C and the last end node D of the second line.

[0008] Preferably, the signal acquisition unit includes: The current transformer CT1 is mounted on the conductor at the first terminal node A of the first line; The current transformer CT2 is mounted on the conductor at the first node C of the second line. The current transformer CT3 is mounted on the conductor at the end node B of the first line. The voltage measurement unit is located at node A, node B, and the secondary side of the voltage transformer PT.

[0009] Preferably, the current transformers CT1, CT2, and CT3 all have a transformation ratio of 600:5 and adopt a through-type structure.

[0010] Preferably, the voltage measurement unit uses a high-precision voltage transformer with a transformation ratio of 100V:5V.

[0011] Preferably, the terminal node B of the first line is grounded through a current-limiting resistor R, and the current-limiting resistor R is an adjustable resistor.

[0012] Preferably, the signal acquisition unit also includes a synchronization control module, which uses GPS timing technology to ensure synchronous acquisition of signals from each measurement point.

[0013] Therefore, the dual-circuit line incomplete stop mutual inductance parameter test circuit of the present invention, with the above-described structure, has the following beneficial effects: (1) This utility model adopts a circuit structure that combines different frequency excitation and power frequency operation, which realizes high-precision parameter testing of double-circuit lines under incomplete power outage conditions, with a measurement error of less than 1% and an angle error within ±0.2°. (2) This utility model simulates electromagnetic coupling between lines by using an isolation transformer and combines GPS synchronous acquisition technology to effectively eliminate power frequency interference and improve test reliability. (3) The circuit structure of this utility model is simple and the connection relationship is clear, which makes it easy to implement and promote its application on site and significantly improves the testing efficiency.

[0014] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of a test circuit for mutual inductance parameters of a double-circuit line with incomplete stop, according to this utility model. Detailed Implementation

[0016] The technical solution of this utility model will be further described below with reference to the accompanying drawings and embodiments.

[0017] Unless otherwise defined, the technical or scientific terms used in this utility model shall have the ordinary meaning understood by one of ordinary skill in the art to which this utility model pertains. The terms "first," "second," and similar terms used in this utility model do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0018] Example like Figure 1 As shown, this utility model provides a test circuit for mutual inductance parameters in a double-circuit line with incomplete outage, as detailed below: The signal excitation unit includes a variable frequency power supply S1 and a mains frequency power supply. The variable frequency power supply S1 is a vector control frequency converter (model VM06-1100), and its output is connected to the first terminal node A of the first line. The grounding terminal of the variable frequency power supply S1 is directly grounded. The mains frequency power supply is connected to the first terminal node C of the second line through a voltage transformer PT (turn ratio 10000:100) to simulate the normal operation of the second line.

[0019] The coupling simulation unit is implemented using an isolation transformer with a turns ratio of 1:1. The primary winding of the isolation transformer is connected between the first terminal node A and the last terminal node B of the first line, and the secondary winding is connected between the first terminal node C and the last terminal node D of the second line, to accurately simulate the electromagnetic coupling characteristics between the two circuits.

[0020] The signal acquisition unit includes three current transformers (CT1, CT2, and CT3) and a voltage measurement unit. Current transformer CT1 is mounted on the conductor at the beginning of the first line (node ​​A), CT2 is mounted on the conductor at the beginning of the second line (node ​​C), and CT3 is mounted on the conductor at the end of the first line (node ​​B), all with a transformation ratio of 600:5. The voltage measurement unit is located at nodes A and B and on the secondary side of the voltage transformer PT, employing a high-precision voltage transformer (model PT-X-2) with a transformation ratio of 100V:5V.

[0021] The terminal node B of the first line is grounded through a current-limiting resistor R. This current-limiting resistor is adjustable and is used to limit the grounding current and simulate actual line conditions. The signal acquisition unit is also equipped with a synchronization control module, which uses GPS timing technology to ensure synchronous acquisition of signals from each measurement point.

[0022] The variable-frequency power supply S1 generates an adjustable frequency signal of 45-55Hz through its internal inverter circuit. During operation, the control system automatically switches the output frequency (45Hz or 55Hz) according to the test requirements, effectively eliminating power frequency interference by comparing the measurement results at different frequencies. The power output is transmitted via cable to node A at the beginning of the first line to establish the variable-frequency test electric field.

[0023] The isolation transformer achieves electrical isolation and energy transfer in a double-circuit line through the principle of electromagnetic induction. When a different frequency signal is applied to the primary winding (first line), a corresponding signal is induced in the secondary winding (second line), accurately simulating the mutual inductance effect between actual transmission lines. The transformer's impedance characteristics (Z12=Z21=3.9126+j9.507) are precisely designed to match the parameters of the actual line.

[0024] Current transformers CT1, CT2, and CT3, based on the principle of electromagnetic induction, convert the large primary current into a small current signal at a transformation ratio of 600:5. The voltage measurement unit converts the high voltage signal into a low-voltage signal that can be acquired through a precision resistor voltage divider and signal conditioning circuit. The GPS synchronization module ensures that the time synchronization accuracy of each acquisition point reaches the microsecond level, eliminating measurement errors caused by differences in sampling time.

[0025] The current-limiting resistor R limits the grounding current, preventing overcurrent during testing. Furthermore, by adjusting the resistance value, the characteristics of transmission lines of different lengths can be simulated, improving the adaptability of the test circuit.

[0026] Working Principle: During testing, the variable frequency power supply S1 is first set to output a specified voltage (adjustable from 50-500V) and frequency (45Hz / 55Hz). The mains frequency power supply establishes a simulated operating voltage on the second line via a PT. The signal acquisition unit synchronously acquires the voltage and current signals of each node, and after signal conditioning, sends them to the processing unit. The processing unit is based on the impedance calculation formula: ; ; The zero-sequence impedance and mutual inductance parameters are calculated, and by comparing the measurement results at different frequencies, the parameters are automatically converted to the accurate parameters at the power frequency of 50Hz.

[0027] The test circuit in this embodiment has been verified in practice. Under the condition of 100V output from a different frequency power supply, the measured zero-sequence impedance Z11 = 1.0425Ω∠78.55° is only 0.11% different from the standard value, which fully meets the requirements of engineering applications.

[0028] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of this utility model and not to limit it. Although the utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solution of this utility model, and these modifications or equivalent substitutions cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of this utility model.

Claims

1. A test circuit for incomplete stop mutual inductance parameters in a double-circuit line, characterized in that, include: The signal excitation unit is used to provide a different frequency test signal to the first line and a power frequency operation signal to the second line; A coupling simulation unit is connected between the first line and the second line to simulate the electromagnetic coupling characteristics between the two lines. The signal acquisition unit is configured to synchronously acquire voltage and current signals on the first and second lines; A signal processing unit, connected to the signal acquisition unit, is used to calculate the mutual inductance parameters of the line based on the acquired voltage and current signals. The first line is configured as a power outage test line, and the second line is configured as a normal operation line. The two lines are electromagnetically coupled and electrically isolated through the coupling simulation unit.

2. The test circuit for incomplete shutdown mutual inductance parameters of a double-circuit line according to claim 1, characterized in that, The signal excitation unit includes a variable frequency power supply S1 and a power frequency power supply. The output terminal of the variable frequency power supply S1 is connected to the first terminal node A of the first line, and the power frequency power supply is connected to the first terminal node C of the second line through a voltage transformer PT.

3. The test circuit for incomplete shutdown mutual inductance parameters of a double-circuit line according to claim 2, characterized in that, The variable frequency power supply S1 is a vector control frequency converter with an adjustable output frequency range of 45Hz to 55Hz.

4. The test circuit for incomplete shutdown mutual inductance parameters of a double-circuit line according to claim 1, characterized in that, The coupling simulation unit includes an isolation transformer, the primary winding of which is connected between the first terminal node A and the last terminal node B of the first line, and the secondary winding is connected between the first terminal node C and the last terminal node D of the second line.

5. The test circuit for incomplete shutdown mutual inductance parameters of a double-circuit line according to claim 1, characterized in that, The signal acquisition unit includes: The current transformer CT1 is mounted on the conductor at the first terminal node A of the first line; The current transformer CT2 is mounted on the conductor at the first node C of the second line. The current transformer CT3 is mounted on the conductor at the end node B of the first line. The voltage measurement unit is located at node A, node B, and the secondary side of the voltage transformer PT.

6. The test circuit for incomplete shutdown mutual inductance parameters of a double-circuit line according to claim 5, characterized in that, The current transformers CT1, CT2, and CT3 all have a transformation ratio of 600:5 and adopt a through-type structure.

7. The test circuit for incomplete shutdown mutual inductance parameters of a double-circuit line according to claim 5, characterized in that, The voltage measurement unit uses a high-precision voltage transformer with a transformation ratio of 100V:5V.

8. The test circuit for incomplete shutdown mutual inductance parameters of a double-circuit line according to claim 1, characterized in that, The terminal node B of the first line is grounded through a current-limiting resistor R, which is an adjustable resistor.

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