Design method of broadband electronic current transformer suitable for traveling wave positioning type primary and secondary fusion switch

Abstract

The invention relates to a broadband electronic current transformer design method suitable for a traveling wave positioning type primary and secondary fusion switch. The method comprises the following steps: determining Rogowski coil parameters according to to-be-tested wire parameters; detecting an electromotive force signal of the wire to be detected through a Rogowski coil; amplifying the electromotive force signal by using an amplifying circuit; extracting a low-frequency power frequency voltage signal and a high-frequency traveling wave voltage signal in the amplified electromotive force signal; respectively restoring the digitized power frequency voltage signal and the digitized traveling wave voltage signal into a power frequency current signal and a traveling wave current signal through a digital integrator; switching measurement and various fault protection are carried out by using a power frequency current signal; and fault accurate positioning and small current grounding protection are carried out by using the traveling wave current signal. The electronic transformer with the broadband response characteristic is used for a primary and secondary fusion switch, the problem that the precision is reduced when high-frequency signals are measured is solved, traveling wave signals can be collected for accurate positioning, and the positioning cost is reduced.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a design method for a broadband electronic current transformer suitable for a traveling wave positioning type primary and secondary fusion switch. Background Art

[0002] The distribution network is the weak link of the power system, and 60% of the power system faults are distribution network faults. With the development of distribution automation, the installation of primary and secondary fusion switches on the distribution line can effectively judge the fault section, isolate and restore the fault. This method has been widely used in the State Grid and the Southern Grid. However, due to the terminal layout and monitoring range of distribution automation, only the kilometer-level fault location can be achieved. After the section is successfully determined, there are still a large number of fault inspection tasks, which has not fundamentally reduced the workload of traditional fault inspection. Therefore, traveling wave positioning technology came into being. Traveling waves are a high-frequency transient signal generated immediately after a fault occurs in the power system. They contain characteristics such as direction, amplitude, and frequency. By extracting the characteristics of voltage traveling waves or current traveling waves, fault information can be obtained, thereby realizing fault ranging. The distribution network traveling wave ranging device can achieve positioning accuracy of hundreds of meters or even meters, but traveling waves have the characteristics of high frequency, fast speed, fast attenuation, and short duration, so the accurate collection of traveling waves is difficult. Summary of the invention

[0003] The technical problem to be solved by the present invention is to provide a design method for a wide-band electronic current transformer suitable for a traveling wave positioning type primary and secondary fusion switch, so as to overcome the deficiencies in the above-mentioned prior art.

[0004] The technical solution of the present invention to solve the above technical problems is as follows: A design method for a wide-band electronic current transformer suitable for a traveling wave positioning type primary and secondary fusion switch comprises the following steps:

[0005] Step S01: determining the Rogowski coil parameters according to the parameters of the conductor to be tested;

[0006] Step S02: detecting the electromotive force signal of the conductor to be tested by means of a Rogowski coil;

[0007] Step S03: amplifying the electromotive force signal using an amplifier circuit;

[0008] Step S04: extracting a low-frequency power frequency voltage signal and a high-frequency traveling wave voltage signal from the amplified electromotive force signal;

[0009] Step S05: converting the power frequency voltage signal and the traveling wave voltage signal from analog signals into digital signals through an A / D converter;

[0010] Step S06: Restore the digitized power frequency voltage signal and the traveling wave voltage signal into a power frequency current signal and a traveling wave current signal respectively through a digital integrator;

[0011] Step S07: Use the power frequency current signal to perform switch measurement and various fault protections; use the traveling wave current signal to perform accurate fault location and small current grounding protection.

[0012] The beneficial effects of the present invention are as follows: when the measured current passes along the axis of the Rogowski coil, a changing magnetic field will be generated around it. According to Faraday's law of electromagnetic induction, this changing magnetic field will induce an electromotive force in the Rogowski coil; the original induced electromotive force signal is usually very weak and needs to be amplified by an amplifier circuit first; the amplified signal may contain noise and unnecessary frequency components, which need to be removed by a filter; after amplification and filtering, the analog signal is converted into a digital signal for digital processing; the voltage signal is restored to a current signal by a digital integrator; the present invention further incorporates the traveling wave monitoring function on the basis of the protection of the original primary and secondary fusion switch. The electronic mutual inductor with a wide-band response characteristic of the present invention is used for the primary and secondary fusion switch, which not only solves the problem of decreased accuracy when measuring high-frequency signals, but also can collect traveling wave signals for precise positioning, thereby reducing the positioning cost.

[0013] Based on the above technical solution, the present invention can also be improved as follows.

[0014] Furthermore, the Rogowski coil in step S01 adopts a multi-layer reverse stacking series design of a PCB board, the winding directions of two adjacent Rogowski coils are opposite, and multiple Rogowski coils of the same model and the same parameters are connected in series.

[0015] Furthermore, the mutual inductance coefficient of n Rogowski coils connected in series is:

[0016]

[0017] Among them, R b is the inner diameter of the frame, R a is the outer diameter of the frame, N is the number of winding turns, h is the frame height, and μ0 is the vacuum permeability, which is 4π×10 -7 H / m;

[0018] The self-inductance coefficient is:

[0019]

[0020] The distributed capacitance is:

[0021]

[0022] Further, step S04 specifically includes the following steps:

[0023] The amplified electromotive force signal passes through a 50Hz notch filter to remove the power frequency interference in the power system; after the 50Hz notch, a high-pass filter is applied to further filter out the low-frequency components to obtain the traveling wave voltage signal;

[0024] The amplified electromotive force signal is conditioned by a voltage follower, and then the conditioned signal is sent to a low-pass filter to filter out high-frequency noise and obtain an industrial frequency voltage signal.

[0025] Further, the digital integrator in step S05 includes an active integrator for the power frequency voltage signal and a composite integrator for the traveling wave voltage signal;

[0026] The transfer function of the active integrator is:

[0027]

[0028]

[0029] Where T2 is the active integration time constant, limited to 3dB, the upper limit frequency f of the integration circuit H1 and the lower frequency f L1 They are:

[0030]

[0031] The transfer function of the composite integrator is:

[0032]

[0033] Ti is the time constant of the composite integrator, limited to 3dB, and the upper limit frequency f of the integration circuit H2 and the lower frequency f L2 for:

[0034]

[0035] Further, step S01 specifically includes the following steps:

[0036] Step S11: constraining the skeleton diameter of the Rogowski coil according to the wire diameter of the wire to be tested;

[0037] Step S12: constraining the number of turns of the Rogowski coil according to the primary and secondary current transformation ratio of the conductor to be tested and the skeleton diameter of the Rogowski coil;

[0038] Step S13: determining the cut-off frequency according to the current frequency range of the conductor to be tested as the objective function for optimizing the skeleton diameter and the number of winding turns;

[0039] Step S14: using numerical optimization analysis and calculation software to obtain the optimal skeleton diameter and number of winding turns of the Rogowski coil. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a signal processing flow chart of the present invention;

[0041] Figure 2 It is a schematic diagram of the series structure of the Rogowski coils of the present invention;

[0042] Figure 3 is a circuit diagram of an active integrator of the present invention;

[0043] Figure 4 This is a circuit diagram of the composite integrator of the present invention. DETAILED DESCRIPTION

[0044] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0045] like Figure 1 to Figure 4 As shown, in Embodiment 1, a design method of a wide-band electronic current transformer suitable for a traveling wave positioning type primary and secondary fusion switch comprises the following steps:

[0046] Step S01: determining the Rogowski coil parameters according to the parameters of the conductor to be tested;

[0047] Step S02: detecting the electromotive force signal of the conductor to be tested by means of a Rogowski coil;

[0048] Step S03: amplifying the electromotive force signal using an amplifier circuit;

[0049] Step S04: extracting a low-frequency power frequency voltage signal and a high-frequency traveling wave voltage signal from the amplified electromotive force signal;

[0050] Step S05: converting the power frequency voltage signal and the traveling wave voltage signal from analog signals into digital signals through an A / D converter;

[0051] Step S06: Restore the digitized power frequency voltage signal and the traveling wave voltage signal into a power frequency current signal and a traveling wave current signal respectively through a digital integrator;

[0052] Step S07: Use the power frequency current signal to perform switch measurement and various fault protections; use the traveling wave current signal to perform accurate fault location and small current grounding protection.

[0053] When the measured current passes along the axis of the Rogowski coil, a changing magnetic field will be generated around it. According to Faraday's law of electromagnetic induction, this changing magnetic field will induce an electromotive force in the Rogowski coil. The original induced electromotive force signal is usually very weak and needs to be amplified by an amplifier circuit first. The amplified signal may contain noise and unnecessary frequency components, which need to be removed by a filter. After amplification and filtering, the analog signal is converted into a digital signal for digital processing. The voltage signal is restored to a current signal through a digital integrator.

[0054] The present invention further incorporates the traveling wave monitoring function on the basis of the protection of the original primary and secondary fusion switch. The electronic mutual inductor with wide-frequency response characteristics of the present invention is used for the primary and secondary fusion switch, which not only solves the problem of reduced accuracy when measuring high-frequency signals, but also can collect traveling wave signals for precise positioning, thereby reducing the positioning cost.

[0055] Embodiment 2: This embodiment is a further improvement on the basis of embodiment 1, and its details are as follows:

[0056] The Rogowski coil in step S01 adopts a multi-layer reverse stacking series design on a PCB board, the winding directions of two adjacent Rogowski coils are opposite, and multiple Rogowski coils of the same model and with the same parameters are connected in series. Figure 3 As shown, its advantages are to eliminate external magnetic field interference perpendicular to the coil plane, increase the coil mutual inductance, reduce stray capacitance, and improve the coil sensitivity and measurement range.

[0057] Embodiment 3, this embodiment is a further improvement on the basis of embodiment 2, and its details are as follows:

[0058] The mutual inductance coefficient of n Rogowski coils connected in series is:

[0059]

[0060] Among them, R b is the inner diameter of the frame, R a is the outer diameter of the frame, N is the number of winding turns, h is the frame height, and μ0 is the vacuum permeability, which is 4π×10 -7 H / m;

[0061] The self-inductance coefficient is:

[0062]

[0063] The distributed capacitance is:

[0064]

[0065] Embodiment 4: This embodiment is a further improvement on the basis of embodiment 1, and its details are as follows:

[0066] Step S04 specifically includes the following steps:

[0067] The amplified electromotive force signal passes through a 50Hz notch filter to remove the power frequency interference in the power system, that is, 50Hz noise, thereby purifying the signal; after the 50Hz notch, a high-pass filter is applied to further filter out the low-frequency components, allowing only signals above a specific cutoff frequency to pass through, and obtaining the traveling wave voltage signal; combining notch filtering and high-pass filtering, the traveling wave current can be effectively extracted from the signal containing power frequency interference;

[0068] The amplified electromotive force signal is conditioned by a voltage follower to improve its driving ability while maintaining the integrity of the signal. The conditioned signal is then sent to a low-pass filter to filter out high-frequency noise, retaining only the power frequency and its nearby low-frequency components to obtain the power frequency voltage signal. Combining the voltage follower and the low-pass filter effectively extracts a clean power frequency current signal from the original signal containing noise.

[0069] The main frequency band of the fault transient signal is distributed between 300 and 1000 Hz, and the traveling wave frequency is mostly concentrated between 10 kHz and 2000 kHz. Therefore, the cutoff frequency of the high-pass filter and the low-pass filter is selected to be 5000 Hz.

[0070] Embodiment 5, this embodiment is a further improvement on the basis of embodiment 1, and its details are as follows:

[0071] The digital integrator in step S05 includes an active integrator for the power frequency voltage signal and a composite integrator for the traveling wave voltage signal;

[0072] The transfer function of the active integrator is:

[0073]

[0074]

[0075] Where T2 is the active integration time constant, limited to 3dB, the upper limit frequency f of the integration circuit H1 and the lower frequency f L1 They are:

[0076]

[0077] The circuit diagram of the active integrator is as follows Figure 3 As shown, the circuit structure is simple, with feedback resistor Rf, which can suppress low-frequency noise to a certain extent, has fast response and avoids signal pre-shooting;

[0078] The transfer function of the composite integrator is:

[0079]

[0080] Ti is the time constant of the composite integrator, limited to 3dB, and the upper limit frequency f of the integration circuit H2 and the lower frequency f L2 for:

[0081]

[0082] The circuit diagram of the composite integrator is as follows Figure 4 As shown, it is a combination of passive integration and active integration, and its purpose is to use the characteristics of passive integration to increase the upper cut-off frequency.

[0083] Embodiment 6: This embodiment is a further improvement on the basis of embodiment 1, and its details are as follows:

[0084] The relevant parameters that affect the sensor's acquisition of broadband signals include the number of turns of the Rogowski coil, the self-inductance coefficient, the mutual inductance coefficient and the distributed capacitance;

[0085] Step S01 specifically includes the following steps:

[0086] Step S11: constraining the skeleton diameter of the Rogowski coil according to the wire diameter of the wire to be tested;

[0087] Step S12: constraining the number of turns of the Rogowski coil according to the primary and secondary current transformation ratio of the conductor to be tested and the skeleton diameter of the Rogowski coil;

[0088] Step S13: determining the cut-off frequency according to the current frequency range of the conductor to be tested as the objective function for optimizing the skeleton diameter and the number of winding turns;

[0089] Step S14: using numerical optimization analysis and calculation software to obtain the optimal skeleton diameter and number of winding turns of the Rogowski coil.

[0090] In the specific implementation, the optimal parameters of the Rogowski coil are selected using numerical optimization analysis and calculation software; based on the application scenario of the primary and secondary fusion switch with traveling wave measurement function, through the above parameter selection process, the constraint conditions for parameter selection of the present invention are determined as follows: (1) the diameter range of 10 kV overhead conductor is about 8.4 mm to 17.48 mm; (2) the primary and secondary current transformation ratio is 600 / 1; (3) the current measurement frequency range is 10 Hz to 10 MHz.

[0091] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A design method for a broadband electronic current transformer suitable for a traveling wave positioning type primary and secondary fusion switch, characterized in that: The steps include: Step S01: determining the Rogowski coil parameters according to the parameters of the conductor to be tested; Step S02: detecting the electromotive force signal of the conductor to be tested by the Rogowski coil; Step S03: amplifying the electromotive force signal using an amplifier circuit; Step S04: extracting a low-frequency power frequency voltage signal and a high-frequency traveling wave voltage signal from the amplified electromotive force signal; Step S05: converting the power frequency voltage signal and the traveling wave voltage signal from analog signals into digital signals through an A / D converter; Step S06: Restore the digitized power frequency voltage signal and the traveling wave voltage signal into a power frequency current signal and a traveling wave current signal respectively through a digital integrator; Step S07: using the power frequency current signal to perform switch measurement and various fault protections; using the traveling wave current signal to perform accurate fault location and small current grounding protection.

2. A design method for a wideband electronic current transformer suitable for a traveling wave positioning type primary and secondary fusion switch according to claim 1, characterized in that: The Rogowski coil in step S01 adopts a multi-layer reverse stacking series design of a PCB board, the winding directions of two adjacent Rogowski coils are opposite, and multiple Rogowski coils of the same model and the same parameters are connected in series.

3. A design method for a wideband electronic current transformer suitable for a traveling wave positioning type primary and secondary fusion switch according to claim 2, characterized in that: The mutual inductance coefficient of n Rogowski coils connected in series is: Among them, R b is the inner diameter of the frame, R a is the outer diameter of the frame, N is the number of winding turns, h is the frame height, and μ0 is the vacuum permeability, which is 4π×10 -7 H / m; The self-inductance coefficient is: The distributed capacitance is:

4. The method for designing a wideband electronic current transformer suitable for a traveling wave positioning type primary and secondary fusion switch according to claim 1, characterized in that: The step S04 specifically includes the following steps: The amplified electromotive force signal passes through a 50Hz notch filter to remove the power frequency interference in the power system; after the 50Hz notch, a high-pass filter is applied to further filter out the low-frequency components to obtain the traveling wave voltage signal; The amplified electromotive force signal is conditioned by a voltage follower, and then the conditioned signal is sent to a low-pass filter to filter out high-frequency noise to obtain the industrial frequency voltage signal.

5. The method for designing a wideband electronic current transformer suitable for a traveling wave positioning type primary and secondary fusion switch according to claim 1, characterized in that: The digital integrator in step S05 includes an active integrator for the power frequency voltage signal and a composite integrator for the traveling wave voltage signal; The transfer function of the active integrator is: When the circuit is in the integrating state, that is, at this time: Where T2 is the active integration time constant, limited to 3dB, the upper limit frequency f of the integration circuit H1 and the lower frequency f L1 They are: The transfer function of the composite integrator is: Ti is the time constant of the composite integrator, limited to 3dB, and the upper limit frequency f of the integration circuit H2 and the lower frequency f L2 for:

6. The method for designing a wideband electronic current transformer suitable for a traveling wave positioning type primary and secondary fusion switch according to claim 1, characterized in that: The step S01 specifically includes the following steps: Step S11: constraining the skeleton diameter of the Rogowski coil according to the wire diameter of the wire to be tested; Step S12: constraining the number of turns of the Rogowski coil according to the primary and secondary current transformation ratio of the conductor to be tested and the skeleton diameter of the Rogowski coil; Step S13: determining a cut-off frequency according to the current frequency range of the conductor to be tested as an objective function for optimizing the skeleton diameter and the number of winding turns; Step S14: using numerical optimization analysis and calculation software to obtain the optimal skeleton diameter and the number of winding turns of the Rogowski coil.

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