High-voltage cable broadband impedance on-line test signal coupling device and cable plug

Abstract

The invention discloses a high-voltage cable broadband impedance online test signal coupling device and a cable plug. The high-voltage cable broadband impedance online test signal coupling device comprises a signal coupling module and a protection control module. The protection control module is connected with the signal coupling module and comprises a control unit and a controlled switch unit; the control unit is used for generating and outputting a turn-off instruction when monitoring that the voltage of the high-voltage cable is changed from a non-voltage state to a voltage state; and the control module is used for delaying preset time after the turn-off instruction is generated, and generating and outputting a turn-on instruction after the voltage of the high-voltage cable is confirmed to be maintained in the voltage state again. According to the invention, a test signal channel can be automatically cut off at the moment of power-on of the cable, the impact of operation overvoltage on a rear-end broadband impedance spectroscopy analyzer is avoided, the reliability and safety of the whole test system are improved, and long-term and continuous online state monitoring becomes possible.

Description

Technical Field

[0001] This invention relates to the field of power equipment condition monitoring technology, and in particular to a signal coupling device and cable plug for online testing of broadband impedance of high-voltage cables. Background Technology

[0002] High-voltage power cables are key equipment in urban power grids, and reliable monitoring of their operating status is crucial for ensuring power supply security. Wideband impedance spectroscopy, by analyzing the impedance frequency characteristics of cables, can effectively diagnose early defects such as aging and moisture absorption, and has become an important development direction for cable condition monitoring in recent years.

[0003] Currently, existing technologies offer solutions for online broadband impedance testing of cables. These solutions typically employ a coupling circuit composed of passive components, connected between the energized cable and the impedance analyzer. The design goal of this coupling circuit is to isolate the high-frequency power voltage of the cable while allowing the high-frequency signals required for testing to pass through, thus enabling impedance spectrum measurement without power interruption. However, because the coupling circuit is always connected, the high-amplitude transient voltage generated when the cable system is energized can be directly conducted to the broadband impedance analyzer via the coupling path. This unpredictable surge voltage can easily exceed the tolerance range of the broadband impedance analyzer, leading to permanent damage to its internal components. This not only poses a significant risk of equipment damage and economic loss to online testing operations but also fundamentally restricts the large-scale application of broadband impedance monitoring technology in high-voltage cable systems. Summary of the Invention

[0004] This invention provides a signal coupling device and cable plug for online testing of broadband impedance of high-voltage cables. It can automatically cut off the test signal path the moment the cable is powered on, avoiding the impact of operational overvoltage on the downstream broadband impedance spectrum analyzer, improving the reliability and safety of the entire testing system, and making long-term, continuous online status monitoring possible.

[0005] In a first aspect, embodiments of the present invention provide a signal coupling device for online testing of broadband impedance of high-voltage cables, characterized in that it comprises: a signal coupling module and a protection control module; the signal coupling module is connected between the high-voltage cable and a broadband impedance spectrum analyzer, and is used to attenuate and suppress the high-voltage low-frequency signal from the high-voltage cable, while coupling and conducting the low-voltage high-frequency signal used for broadband impedance spectrum testing; the protection control module is connected to the signal coupling module, and includes a control unit and a controlled switch unit; the control unit is connected to the controlled switch unit, and is used to generate and output a shutdown command when the voltage of the high-voltage cable changes from an unvoltageed state to a voltaged state; and is used to generate and output a conduction command after delaying a preset time after generating the shutdown command and confirming again that the voltage of the high-voltage cable remains in a voltaged state; the controlled switch unit is connected in series in the output path of the signal coupling module and connected to the control unit, and is used to respond to the shutdown command to cut off the signal path from the signal coupling module to the broadband impedance spectrum analyzer, or respond to the conduction command to conduct the signal path.

[0006] Optionally, the signal coupling module includes a first capacitor, a first resistor, a second capacitor, and a second resistor; the first end of the first capacitor is connected to a high-voltage cable, the second end of the first capacitor is connected to the first end of the first resistor, and the second end of the first resistor is grounded; the first end of the second capacitor is connected to the second end of the first capacitor, the second end of the second capacitor is connected to the first end of the second resistor and a broadband impedance spectrum analyzer, and the second end of the second resistor is grounded.

[0007] Optionally, the controlled switch unit includes a selector switch; the selector switch has a common terminal, a normally closed contact, and a normally open contact; the normally open contact of the selector switch is connected to the first terminal of the second capacitor; the common terminal of the selector switch is connected to the second terminal of the first capacitor; the normally closed contact of the selector switch is either floating or grounded.

[0008] Optionally, the controlled switch unit further includes a control coil connected to the control unit for receiving a shutdown command or a turn-on command; wherein, when the control unit outputs a shutdown command, the control coil is de-energized, and its common terminal is connected to a normally closed contact to cut off the signal path; when the control unit outputs a turn-on command, the control coil is energized, and its common terminal is connected to a normally open contact to turn on the signal path.

[0009] Optionally, the protection control module also includes a high-voltage power extraction unit; the input terminal of the high-voltage power extraction unit is connected to the high-voltage cable, and the output terminal of the high-voltage power extraction unit is connected to the control unit and the controlled switch unit, for converting the AC voltage of the high-voltage cable into DC voltage to power the controlled switch unit; and for monitoring the voltage status of the high-voltage cable.

[0010] Secondly, embodiments of the present invention provide a cable plug, including a high-voltage cable broadband impedance online test signal coupling device provided in any embodiment of the present invention; the cable plug includes an insulating body and a metal connector disposed within the insulating body; a first end of the metal connector is used to connect to a high-voltage cable, and a second end is connected to the first end of a first capacitor in the high-voltage cable broadband impedance online test signal coupling device.

[0011] Optionally, the metal connector is a metal stud extending from the insulating body; the first end of the first capacitor is connected to the high-voltage cable through the metal stud.

[0012] Optionally, the protection and control module in the high-voltage cable broadband impedance online test signal coupling device is encapsulated in a modular housing, which is connected to the second end of the first capacitor via a bolt structure.

[0013] Optionally, the modular housing is provided with a signal output interface for connecting a broadband impedance spectrum analyzer; and / or, the modular housing is encapsulated with insulating encapsulation material.

[0014] Optionally, the cable plug may also include a removable sealing cap for sealing the cavity housing the protection control module.

[0015] The high-voltage cable broadband impedance online testing signal coupling device provided in this invention includes a signal coupling module and a protection control module. By monitoring the voltage status of the high-voltage cable in real time, when the voltage changes from an unvoltaged state to a voltaged state, the control unit outputs a shutdown command, causing the controlled switch unit to cut off the signal path from the signal coupling module to the broadband impedance spectrum analyzer. After a preset delay time and confirmation of sustained voltage stability, the control unit outputs a conduction command to restore the signal path to the controlled switch unit. This intelligent delay protection mechanism based on state monitoring can automatically cut off the test signal path the moment the cable is powered on, effectively blocking the impact of operational overvoltage on the downstream broadband impedance spectrum analyzer, and solving the problem of fragile precision instruments in online testing. Compared to existing solutions where the coupling circuit is always in a connected state, leading to the risk of surge voltage on the testing instrument, this solution achieves reliable online monitoring through the intelligent judgment and delayed conduction mechanism of the protection control module, ensuring the long-term stable operation of the testing equipment.

[0016] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of a high-voltage cable broadband impedance online testing signal coupling device provided in an embodiment of the present invention;

[0019] Figure 2 This is a Bode plot of the amplitude attenuation characteristics of an RC high-pass filter circuit near the cutoff frequency, provided in an embodiment of the present invention.

[0020] Figure 3 This is a Bode plot of the amplitude attenuation characteristic of an RC high-pass filter circuit under the frequency of a low-voltage high-frequency signal for measurement, provided in an embodiment of the present invention.

[0021] Figure 4 This is a voltage waveform diagram of the voltage divider node after the high-voltage low-frequency signal is divided by the first capacitor and the first resistor in Embodiment 1 of the present invention.

[0022] Figure 5 This is the output waveform diagram of the high-voltage low-frequency signal after passing through the RC high-pass filter circuit in Embodiment 1 of the present invention;

[0023] Figure 6 The Bode plot shows the amplitude attenuation characteristics of the 50Hz high-voltage low-frequency signal in Embodiment 1 of the present invention.

[0024] Figure 7 This is a comparison diagram of the dual-channel waveforms when a low-voltage, high-frequency signal is input in Embodiment 2 of the present invention;

[0025] Figure 8 This is a comparison diagram of the dual-channel waveforms of the reverse low-voltage high-frequency signal in Embodiment 3 of the present invention;

[0026] Figure 9 This is an embodiment of the present invention that provides an impedance spectrum and phase waveform diagram for measurement without connection to a selection switch;

[0027] Figure 10 This is an example of an impedance spectrum and phase waveform diagram obtained from an access selection switch measurement according to an embodiment of the present invention;

[0028] Figure 11 This is a schematic diagram of the structure of a cable plug provided in an embodiment of the present invention;

[0029] Figure 12 This is a schematic diagram of the insulation body of a high-voltage cable testing device provided in an embodiment of the present invention;

[0030] Figure 13 This is a cross-sectional view of the internal structure of an insulating body receiving chamber provided in an embodiment of the present invention;

[0031] Figure 14 This is a three-dimensional structural diagram of the connection end face of a modular shell provided in an embodiment of the present invention;

[0032] Figure 15 This is a three-dimensional structural diagram of the functional interface end face of a modular shell provided in an embodiment of the present invention;

[0033] Figure 16 This is a schematic diagram of the connection end face structure of a first capacitor provided in an embodiment of the present invention;

[0034] Figure 17 This is a schematic diagram of the threaded connection end face structure of a sealing cap provided in an embodiment of the present invention;

[0035] Figure 18 This is a schematic diagram of the sealing end face structure of a sealing cap provided in an embodiment of the present invention. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0037] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0038] Figure 1 This is a schematic diagram of a signal coupling device for online testing of broadband impedance of high-voltage cables provided in an embodiment of the present invention. Figure 1 As shown, the coupling device includes: a signal coupling module 11 and a protection control module 12;

[0039] The signal coupling module 11 is connected between the high-voltage cable 10 and the broadband impedance spectrum tester 20. The signal coupling module 11 is used to attenuate and suppress the high-voltage low-frequency signal from the high-voltage cable 10, and at the same time to couple and conduct the low-voltage high-frequency signal used for broadband impedance spectrum testing.

[0040] The protection control module 12 is connected to the signal coupling module 11. The protection control module 12 includes a control unit 121 and a controlled switch unit 122.

[0041] The control unit 121 is connected to the controlled switch unit 122 and is used to generate and output a shutdown command when the voltage of the high-voltage cable 10 changes from an unvoltageed state to a voltaged state; and to generate and output a conduction command after delaying a preset time after generating the shutdown command and confirming again that the voltage of the high-voltage cable 10 remains in a voltaged state.

[0042] The controlled switch unit 122 is connected in series in the output path of the signal coupling module 11 and connected to the control unit 11. It is used to respond to the shutdown command to cut off the signal path from the signal coupling module 12 to the broadband impedance spectrum tester 20, or to respond to the conduction command to conduct the signal path.

[0043] Specifically, high-voltage cable 10 refers to power cables with an operating voltage level of 1kV and above, used for transmitting electrical energy. In this invention, it specifically refers to the cable body that needs to be subjected to broadband impedance spectrum online testing.

[0044] A broadband impedance spectrum analyzer 20 refers to an instrument that can apply a series of test signals of different frequencies to the object under test and measure its response, thereby calculating the impedance-frequency curve (i.e., impedance spectrum).

[0045] "No-voltage state" or "Voltage state" is the logical judgment made by control unit 121 regarding the operating status of high-voltage cable 10. "No-voltage state" means that the voltage on the cable conductor is lower than a certain set threshold, which can be regarded as a power outage or no energization; "Voltage state" means that the voltage on the cable conductor is higher than the set threshold, indicating that the cable is energized.

[0046] The shutdown / on command is a logic signal output by the control unit to control the operation of the controlled switch unit. The "shutdown command" is used to instruct the controlled switch unit to cut off the signal path; the "on command" is used to instruct the controlled switch unit to connect the signal path.

[0047] The signal path refers to the complete electrical connection path starting from the output of the signal coupling module 11, passing through the controlled switch unit 122, and finally reaching the input of the broadband impedance spectrum analyzer 20. The on / off state of this path directly determines whether the test can be performed.

[0048] The signal coupling module 11 may include a passive network. Optionally, the signal coupling module 11 may include a resistor-capacitor network, or an inductor-capacitor (LC) network, or a resistor-capacitor-inductor (RCL) composite network. The passive network may include a voltage divider unit for attenuating high-voltage signals and a filter unit for frequency selection. Optionally, the voltage divider unit may include a capacitor voltage divider circuit, or a resistor voltage divider circuit, or a hybrid resistor-capacitor voltage divider circuit; the filter unit may include a high-pass filter circuit, or a band-pass filter circuit, or a band-stop filter circuit.

[0049] The control unit 121 may include a microcontroller. Optionally, the control unit 121 may include a microcontroller, or a digital signal processor (DSP) or a field-programmable gate array (FPGA).

[0050] The controlled switch unit 122 may include an electrically controlled switching device. Optionally, the controlled switch unit 122 may include an electromagnetic relay, a solid-state relay, or a semiconductor switching device. The electrically controlled switching device may include a single-channel switch or a multi-channel selector switch. Optionally, the controlled switch unit 122 may also include a switch driving circuit; the switch driving circuit may include a transistor driving circuit, an optocoupler driving circuit, or a relay driving chip.

[0051] Continue to refer to Figure 1 The operation process of the signal coupling device provided in this embodiment of the invention is as follows:

[0052] When the high-voltage cable 10 is de-energized or de-energized, the control unit 121 detects a de-energized signal. At this time, the control unit 121 ensures that no drive power is supplied to the controlled switch unit 122, which remains in a safe off state due to its de-energization, thereby physically disconnecting the entire signal path from the signal coupling module 11 to the broadband impedance spectrum analyzer 20.

[0053] When power is restored to the high-voltage cable 10 and the voltage changes from off-state to on-state, the control unit 121, upon detecting this on-state signal, will immediately output a shutdown command (or maintain its no-output state) based on its preset safety logic. This ensures that even if the controlled switch unit 122 has operating voltage, it remains off-state because it has not received a valid turn-on command. Therefore, the extremely high amplitude transient surge voltage generated at the moment of closing is completely blocked inside the signal coupling module 11 and cannot be conducted to the downstream broadband impedance spectrum analyzer 20.

[0054] Upon detecting a power-on event, the control unit 121 initiates a preset delay timer (e.g., 5 minutes). This delay is designed to avoid the inevitable operational overvoltage and transient oscillations after the system is switched on, allowing the system to enter a stable operating state.

[0055] After the delay period, the control unit 121 will sample again to confirm whether the voltage of the high-voltage cable 10 is stable and maintained in a voltage state. Only after confirming that the system is completely stable will the control unit 121 output a conduction command. The controlled switch unit 122 responds to this conduction command to connect the signal path. At this time, the broadband impedance spectrum analyzer 20 can begin normal online monitoring.

[0056] When the signal coupling device encounters a sudden loss of voltage in the line during monitoring, the controlled switch unit 122 will return to the off state due to the power loss, immediately cutting off the signal path. At the same time, the control unit 121 records this voltage loss signal and maintains its internal logic in the off state, preparing for the next possible power-on surge.

[0057] The high-voltage cable broadband impedance online testing signal coupling device provided in this invention includes a signal coupling module and a protection control module. By monitoring the voltage status of the high-voltage cable in real time, when the voltage changes from an unvoltaged state to a voltaged state, the control unit outputs a shutdown command, causing the controlled switch unit to cut off the signal path from the signal coupling module to the broadband impedance spectrum analyzer. After a preset delay time and confirmation of sustained voltage stability, the control unit outputs a conduction command to restore the signal path to the controlled switch unit. This intelligent delay protection mechanism based on state monitoring can automatically cut off the test signal path the moment the cable is powered on, effectively blocking the impact of operational overvoltage on the downstream broadband impedance spectrum analyzer, and solving the problem of fragile precision instruments in online testing. Compared to existing solutions where the coupling circuit is always in a connected state, leading to the risk of surge voltage on the testing instrument, this solution achieves reliable online monitoring through the intelligent judgment and delayed conduction mechanism of the protection control module, ensuring the long-term stable operation of the testing equipment.

[0058] Optionally, continue to refer to Figure 1 The signal coupling module 11 includes a first capacitor C1, a first resistor R1, a second capacitor C2, and a second resistor R2.

[0059] The first terminal of the first capacitor C1 is connected to the high-voltage cable 10, the second terminal of the first capacitor C1 is connected to the first terminal of the first resistor R1, and the second terminal of the first resistor R1 is grounded.

[0060] The first terminal of the second capacitor C2 is connected to the second terminal of the first capacitor C1. The second terminal of the second capacitor C2 is connected to the first terminal of the second resistor R2 and the broadband impedance spectrum tester 20. The second terminal of the second resistor R2 is grounded.

[0061] Specifically, the voltage divider unit consists of a first capacitor C1 and a first resistor R1 connected in series. The connection relationship is as follows: the first end of the first capacitor C1 is directly connected to the conductor of the high-voltage cable 10, which undertakes the function of withstanding high voltage and providing capacitive reactance; its second end is connected to the first end of the first resistor R1, forming voltage divider node A; and the second end of the first resistor R1 is reliably grounded.

[0062] For high-voltage, low-frequency signals (such as 50Hz power frequency), the first capacitor C1 exhibits extremely high capacitive reactance, forming a resistive-capacitive voltage divider with the first resistor R1. The vast majority of the power frequency high voltage is applied to the first capacitor C1, resulting in only a significantly reduced voltage at voltage divider node A. By appropriately selecting the parameters of the first capacitor C1 and the first resistor R1, the voltage at voltage divider node A can be safely limited to a range that the downstream circuit can withstand (e.g., below 20V), thereby achieving attenuation and safe isolation of the high-voltage signal.

[0063] The high-pass filter unit consists of a second capacitor C2 and a second resistor R2, and its input terminal is connected to node A of the voltage divider unit.

[0064] This high-pass filter unit, as an RC high-pass filter, has a cutoff frequency much higher than the power frequency (e.g., designed in the hundreds of kHz range). For extremely low-frequency power frequency signals and their harmonics, the filter exhibits high attenuation characteristics, further suppressing them to the millivolt level, almost completely filtering them out. For high-frequency signals used in wideband impedance testing (typically above 1 MHz), the filter's attenuation is minimal, allowing the signal to pass through with almost no loss. The second resistor R2 simultaneously serves as impedance matching and current limiting.

[0065] For example, for a 10kV high-voltage signal, its single-phase voltage is 5.77kV and the frequency is 50Hz. The first capacitor C1 and the first resistor R1 serve to reduce the voltage of the high-voltage low-frequency signal.

[0066] The formula for calculating capacitive reactance is:

[0067] ;

[0068] To keep the voltage at voltage divider node A below 20V, when C1 = 50nF and R1 = 200 ohms:

[0069] ;

[0070] The voltage VA at voltage divider node A is:

[0071] VA=200 / (63662+200)×5770=18.07V

[0072] The high-voltage signal has a frequency of 50Hz, while the minimum frequency of the incident signal being measured is 1MHz. Therefore, a high-pass filter is needed to filter out the 50Hz low-frequency signal. The second capacitor C2 and the second resistor R2 together form an RC high-pass filter circuit.

[0073] According to the cutoff frequency calculation formula, when C2 = 10nf and R1 = 100 ohms, the frequency f is:

[0074] ;

[0075] Therefore, with the RC high-pass filter circuit, the attenuation is 3dB at frequencies up to 159KHz, and there is almost no attenuation at frequencies up to 1MHz.

[0076] Figure 2 This is a Bode plot of the amplitude attenuation characteristics of an RC high-pass filter circuit near the cutoff frequency, provided in an embodiment of the present invention. Figure 2 When the displayed frequency is approximately 156.152kHz, the signal attenuation is -3.094dB, which is close to the theoretically calculated cutoff frequency (approximately 159kHz). The attenuation value also conforms to the characteristic of a high-pass filter attenuating by 3dB at the cutoff frequency.

[0077] Figure 3 This is a Bode plot of the amplitude attenuation characteristics of an RC high-pass filter circuit under the frequency of a low-voltage high-frequency signal for measurement, provided in an embodiment of the present invention. Figure 3 When the frequency displayed is approximately 1.08MHz, the signal attenuation is only -0.094dB, which is extremely small and almost negligible.

[0078] This indicates that for low-voltage, high-frequency signals (minimum frequency 1MHz) used for measurement, the RC high-pass filter circuit produces almost no attenuation, ensuring that the incident signal is transmitted completely to the broadband impedance spectrum analyzer, thus meeting the technical requirement of no attenuation for low-voltage, high-frequency signals.

[0079] This indicates that the RC high-pass filter circuit can significantly attenuate low-frequency signals close to the cutoff frequency, effectively filtering out 50Hz high-voltage low-frequency interference signals and achieving the goal of step-down filtering of high-voltage low-frequency signals.

[0080] The effect of the step-down circuit composed of the first capacitor C1 and the first resistor R1 on low-voltage high-frequency signals

[0081] When a low-voltage, high-frequency signal (minimum frequency 1MHz, 5V) passes through the first capacitor C1,

[0082]

[0083] The voltage at voltage divider node A is:

[0084] VA = 200 / (3.18 + 200) × 5 = 4.92V

[0085] Therefore, the step-down circuit has little effect on the voltage at voltage divider node A, and the first capacitor C1 is equivalent to a short circuit.

[0086] Continue to refer to Figure 1 Optionally, the controlled switch unit 122 includes a selector switch K1; the selector switch K1 has a common terminal, a normally closed contact, and a normally open contact;

[0087] The normally open contact of the selector switch K1 is connected to the first terminal of the second capacitor C2;

[0088] The common terminal of the selector switch K1 is connected to the second terminal of the first capacitor C1;

[0089] Select the normally closed contact of switch K1 to either be left floating or grounded.

[0090] Continue to refer to Figure 1 Optionally, the controlled switch unit 122 further includes a control coil L1, which is connected to the control unit 121 and is used to receive a turn-off command or a turn-on command. When the control unit 121 outputs a turn-off command, the control coil L1 is de-energized, and its common terminal is connected to a normally closed contact to cut off the signal path. When the control unit 121 outputs a turn-on command, the control coil L1 is energized, and its common terminal is connected to a normally open contact to conduct the signal path.

[0091] Specifically, the common terminal serves as the signal input terminal, directly connected to the second terminal (i.e., voltage divider node A) of the first capacitor C1, to receive the original signal from the signal coupling module 11.

[0092] Normally open contact: This serves as a measurement channel, connected to the first terminal of the second capacitor C2. When this channel is open, the signal can flow to subsequent circuitry and the test instrument.

[0093] Normally closed contact: As a safety channel, it is set to be floating or grounded. When this channel is closed, the signal is conducted to ground, thus being completely blocked.

[0094] Control coil L1 is the driving component of selector switch K1, and its on / off state directly determines the position of the contacts:

[0095] Control coil L1 receives commands from control unit 121. When control unit 121 outputs a shutdown command (such as a low-level signal), control coil L1 is de-energized and loses its magnetism. At this time, selector switch K1, under the action of an internal mechanical spring, automatically connects its common terminal to the normally closed contact. Since the normally closed contact is either floating or grounded, the signal from voltage divider node A is interrupted here and cannot continue to be transmitted, thus physically cutting off the entire measurement signal path and ensuring that the device automatically enters the safest disconnect state in the event of power failure or malfunction.

[0096] When the control unit 121 outputs a conduction command (such as a high-level signal), the control coil L1 is energized and generates a magnetic field. This magnetic field drives the internal mechanical structure of the selector switch K1 to move, overcoming the spring force and causing the common terminal to switch to connection with the normally open contact. At this time, the signal from the voltage divider node A can be transmitted to the second capacitor C2 through the normally open contact, the signal path is fully opened, and the system enters the normal measurement state.

[0097] Continue to refer to Figure 1 Optionally, the protection control module 12 also includes a high-voltage power take-off unit 123;

[0098] The input terminal of the high-voltage power extraction unit 123 is connected to the high-voltage cable 10, and the output terminal of the high-voltage power extraction unit 123 is connected to the control unit 121 and the controlled switch unit 122. It is used to convert the AC voltage of the high-voltage cable 10 into DC voltage to power the controlled switch unit 122; and to monitor the voltage status of the high-voltage cable 10.

[0099] Specifically, the input terminal of the high-voltage power extraction unit 123 is directly connected to the conductor of the high-voltage cable 10 and withstands high voltage. Its output terminal is divided into two paths: one is a power output, which provides a stable DC operating voltage (such as 12V) to the control coil and other actuators of the controlled switch unit 122; the other is a signal output, which sends a signal reflecting the cable voltage status to the control unit 121.

[0100] The high-voltage power extraction unit 123 safely extracts a small portion of energy from the high-voltage cable 10 through an internal high-voltage divider circuit (e.g., composed of a high-voltage resistor and a voltage regulator). This energy is converted into pulsating DC by a rectifier bridge, smoothed by a filter capacitor, and finally output as a stable, low-voltage DC power supply through a voltage regulator chip. This power supply is specifically designed to drive loads such as the control coils in the controlled switching unit, achieving energy self-sufficiency for the device without the need for an external auxiliary power supply, greatly enhancing its independence in field applications.

[0101] Another function of the high-voltage power extraction unit 123 is to monitor the voltage status of the high-voltage cable in real time. Its monitoring mechanism is based on the fact that the amplitude of the output voltage of the high-voltage power extraction unit 123 (whether it is the intermediate pulsating DC or the final stable DC) has a direct causal relationship with the voltage of the high-voltage cable at the input end. When the cable is energized (voltaged state), the high-voltage power extraction unit 123 can output electrical energy and the corresponding DC voltage signal normally; when the high-voltage cable 10 is de-energized (de-voltaged state), the high-voltage power extraction unit 123 stops outputting. The control unit 121 determines whether the high-voltage cable 10 is in a energized or de-energized state by continuously sampling the presence or absence of this DC voltage signal. Utilizing the state of the power supply itself to reflect the input side status eliminates the need for a separate voltage sensor, simplifying the system structure.

[0102] The effectiveness of the technical solution of the present invention will be further verified through specific test examples below:

[0103] Example 1: High-voltage low-frequency signal input test

[0104] In this embodiment, the input signal is a high-voltage, low-frequency signal with parameters set as follows: voltage 5770V, frequency 50Hz, corresponding to the single-phase power frequency signal of a 10kV high-voltage cable. In the signal coupling module, the first capacitor C1 = 50nF, the first resistor R1 = 200Ω, the second capacitor C2 = 10nF, and the second resistor R2 = 100Ω.

[0105] The high-voltage, low-frequency signal is connected to the input terminal of the signal coupling module (the first terminal of the first capacitor C1), and the output voltage waveform of the voltage divider node A (the connection point between the second terminal of the first capacitor C1 and the first terminal of the first resistor R1) is monitored using an oscilloscope. Figure 4 This is a voltage waveform diagram of voltage divider node A after the high-voltage, low-frequency signal is divided by the first capacitor and the first resistor in Embodiment 1 of the present invention. Figure 4 As shown in the waveform diagram, the output voltage of voltage divider node A has dropped to below 20V, achieving effective voltage reduction for high-voltage, low-frequency signals.

[0106] The stepped-down signal is then filtered by an RC high-pass filter circuit consisting of the second capacitor C2 and the second resistor R2, and the filtered output signal is monitored again by an oscilloscope. Figure 5 This is the output waveform diagram of the high-voltage low-frequency signal after passing through the RC high-pass filter circuit in Embodiment 1 of the present invention. Figure 5 As shown, the filtered output voltage drops to less than 10mV, and the high-voltage low-frequency signal is almost completely filtered out.

[0107] Meanwhile, the attenuation of the 50Hz high-voltage low-frequency signal was detected using a Bode tester. Figure 6 This is a Bode plot of the amplitude attenuation characteristics of the 50Hz high-voltage low-frequency signal in Embodiment 1 of the present invention. From... Figure 6 The Bode curve can be read, and the attenuation of the 50Hz signal reaches 68dB, further proving that the signal coupling module of the present invention can effectively suppress high-voltage low-frequency interference signals and meet the technical requirements of high-voltage isolation and interference filtering.

[0108] Example 2: Low-voltage high-frequency signal input test

[0109] In this embodiment, the input signal is a low-voltage, high-frequency signal with parameters set to 5V and 1MHz, corresponding to the incident signal used in broadband impedance spectroscopy testing. The parameters of the signal coupling module are consistent with those in Embodiment 1 (C1=50nF, R1=200Ω, C2=10nF, R2=100Ω).

[0110] The aforementioned low-voltage, high-frequency signal is connected to the input terminal of the signal coupling module, and the signal waveforms at the input terminal (channel A) and output terminal (channel B, i.e., the second terminal of the second capacitor C2) of the signal coupling module are monitored using an oscilloscope. Figure 7 This is a comparison diagram of the dual-channel waveforms when a low-voltage, high-frequency signal is input in Embodiment 2 of the present invention. From... Figure 7 The waveform comparison shows that the output waveforms of channel A and channel B are almost completely overlapping, indicating that the step-down circuit composed of the first capacitor C1 and the first resistor R1 has almost no effect on the transmission of low-voltage high-frequency signals, and the signal attenuation is minimal (the voltage of the step-down node A is calculated to be 4.92V), ensuring the integrity of the test signal.

[0111] Example 3: Reverse Low-Voltage High-Frequency Signal Input Test

[0112] In this embodiment, the input signal is a reversed low-voltage high-frequency signal, and its parameter settings are the same as in Embodiment 2, namely, voltage 5V and frequency 1MHz, only the signal transmission direction is reversed (input from the output end of the signal coupling module in reverse, and output from the input end (the first end of the first capacitor C1)).

[0113] The reverse low-voltage high-frequency signal is connected to the output of the signal coupling module and monitored synchronously by an oscilloscope: Channel A acquires the reverse input signal (the second end of the second capacitor C2), and Channel B acquires the reverse output signal (the first end of the first capacitor C1). Figure 8 This is a comparison diagram of the dual-channel waveforms of the reverse low-voltage high-frequency signal in Embodiment 3 of the present invention. From... Figure 8 The waveform comparison shows that the amplitude error of the waveform of channel A and the waveform of channel B is less than 0.03V, the phase difference is less than 1°, and the waveforms almost completely overlap. This proves that the signal coupling module 11 of the present invention has no significant attenuation for the low-voltage high-frequency signal transmitted in the reverse direction, and has bidirectional signal transmission stability. It can adapt to the bidirectional transmission requirements of incident and reflected signals in broadband impedance spectrum testing.

[0114] Example 4: Test of the effect of the access selection switch on the impedance spectrum

[0115] This embodiment verifies the impact of selecting switch K1 in the controlled switch unit 121 on the cable broadband impedance spectrum measurement results through comparative experiments. During the test, the measurement frequency range of the broadband impedance spectrum analyzer was 1MHz-10MHz, and the parameters of the signal coupling module 11 and the protection control module 12 were consistent with those in the previous embodiment.

[0116] First set of experiments: Without connecting the selector switch, directly connect the signal coupling module to the broadband impedance spectrum tester, measure the broadband impedance spectrum and phase of the cable, and obtain the impedance spectrum curve as shown below. Figure 9 As shown. Figure 9This is an embodiment of the present invention that provides an impedance spectrum and phase waveform diagram for measurement without the selection switch connected.

[0117] The second set of tests: Connect the selector switch (with the selector switch in the ON state, common terminal connected to normally open contact), keep other test conditions unchanged, and measure the broadband impedance spectrum and phase of the cable to obtain the impedance spectrum curve as shown below. Figure 10 As shown. Figure 10 This is an example of an impedance spectrum and phase waveform diagram obtained from measuring an access selection switch, provided by an embodiment of the present invention.

[0118] Comparing the impedance spectrum curves of the two sets of experiments reveals that, within the entire measurement frequency band of 1MHz-10MHz, the amplitude and phase changes of the impedance spectrum are minimal after connecting the selector switch, and the influence of the selector switch on the measurement results is negligible. Further compensation processing of the measurement data using software algorithms (such as linear compensation and phase calibration) can completely eliminate the minor errors introduced by the selector switch, ensuring that the measurement accuracy is unaffected, while also providing protection for the test instrument upon power-on.

[0119] The above specific embodiments demonstrate that the high-voltage cable broadband impedance online test signal coupling device of the present invention can effectively attenuate and suppress high-voltage low-frequency interference signals, and ensure the complete transmission of low-voltage high-frequency test signals (including reverse signals). Furthermore, the access of the selection switch does not affect the measurement accuracy. It successfully solves the problems of high-voltage impact damaging instruments and interference signals affecting test accuracy in the prior art, and significantly improves the safety and reliability of the online test system.

[0120] Based on the same inventive concept, this invention also provides a cable plug. Figure 11 This is a schematic diagram of a cable plug provided in an embodiment of the present invention. Figure 11 As shown, the cable plug includes the high-voltage cable broadband impedance online test signal coupling device provided in any embodiment of the present invention; the cable plug 3 includes an insulating body 30 and a metal connector 31 disposed within the insulating body 30;

[0121] The first end of the metal connector 30 is used to connect to the high-voltage cable 10, and the second end is connected to the first end of the first capacitor C1 in the high-voltage cable broadband impedance online test signal coupling device.

[0122] Optionally, continue to refer to Figure 11 The metal connector 31 is a metal stud extending from the insulating body 30; the first end of the first capacitor C1 is connected to the high-voltage cable 10 through the metal stud.

[0123] Figure 12 This is a schematic diagram of the insulation body of a high-voltage cable testing device provided in an embodiment of the present invention. Figure 12As shown, the insulating body is made of a polymer material (such as epoxy resin or cross-linked polyethylene), and has a cylindrical structure. One end is used to connect to the high-voltage cable, and the other end extends away from the high-voltage cable. It is integrally molded to form a sealed housing chamber. Its outer surface is smooth and has high-voltage insulation characteristics, and can withstand power frequency voltages above 10kV. The first capacitor C1 and the protection control module 12 are both disposed within the housing chamber. Optionally, the first capacitor C1 is a ceramic capacitor.

[0124] Figure 13 This is a cross-sectional view of the internal structure of an insulating body accommodating chamber provided in an embodiment of the present invention. For example... Figure 13 As shown, the first capacitor C1 is close to the high-voltage cable side and is coupled to the high-voltage cable conductor through metal pins; the protection control module 12 is close to the chamber opening side and is electrically connected to the SMA (SubMiniature version A) wiring interface OUT1 and the ground wire wiring outlet OUT2; both are encapsulated in the receiving chamber formed by the polymer insulating body 30, and the chamber is filled with insulating potting material, which not only fixes the position of the components, but also further improves the high-voltage isolation and anti-interference performance.

[0125] The protection and control module in the high-voltage cable broadband impedance online test signal coupling device is encapsulated within a modular housing 32. The modular housing 32 is connected to the second end of the first capacitor C1 via a bolt structure 321. The modular housing 32 is provided with a signal output interface SMA for connecting to a broadband impedance spectrum analyzer; and / or, the interior of the modular housing 32 is encapsulated with insulating encapsulation material.

[0126] Figure 14 This is a three-dimensional structural diagram of the connection end face of a modular shell provided in an embodiment of the present invention. Figure 15 This is a three-dimensional structural diagram of the functional interface end face of a modular shell provided in an embodiment of the present invention. Figure 14 and 15 As shown, the connection end face is provided with a bolt structure 321, which is used to achieve mechanical connection and electrical conduction with the second end of the first capacitor through the bolt structure. It is the connection interface between the modular housing 32 and the signal coupling module 11, ensuring the stability and continuity of the signal transmission path.

[0127] The functional interface faceplate integrates three key interfaces: the signal output interface SMA1 is used to connect to a broadband impedance spectrum analyzer to output low-voltage, high-frequency test signals; the small handle 322 features a symmetrically distributed operating structure, facilitating the installation, disassembly, and positioning of the modular housing; and the grounding interface GND is used to connect to the ground wire, achieving electrical grounding to suppress electromagnetic interference and ensure equipment safety. Simultaneously, the modular housing 32 is internally encapsulated with insulating encapsulation material (such as epoxy resin) to provide insulation protection and structural fixation for the internal protection and control modules.

[0128] Figure 16 This is a schematic diagram of the connection end face structure of a first capacitor provided in an embodiment of the present invention, as shown below. Figure 16 As shown, the countersunk hole 33 in the center of the first capacitor is used to achieve precise positioning and mechanical fastening with the modular housing and the high-voltage cable side components through a bolt structure, ensuring the coaxiality of the first capacitor in the signal coupling device and ensuring the stability of the voltage reduction of high-voltage low-frequency signals and the coupling and transmission of low-voltage high-frequency signals.

[0129] Continue to refer to Figure 11 The cable plug also includes a removable sealing cap 34 for sealing the cavity containing the protection control module 12.

[0130] Figure 17 This is a schematic diagram of the threaded connection end face structure of a sealing cap provided in an embodiment of the present invention. Figure 17 As shown, its inner side is provided with an internal thread for engaging with the external thread of the modular housing 32 to achieve detachable screw-on installation and provide a mechanical seal interface for the cavity that houses the protection control module 12.

[0131] Figure 18 This is a schematic diagram of the sealing end face structure of a sealing cap provided in an embodiment of the present invention. Figure 18 As shown, the sealing cover 34 is a circular flat plate structure made of insulating sealing material. After installation, it can seal the cavity that contains the protection and control module, achieving dustproof, moisture-proof and high-voltage insulation protection.

[0132] Based on the structural design of the high-voltage cable broadband impedance online test signal coupling device and cable plug described above, the specific installation process is as follows:

[0133] ①Use a square wrench that matches the size of the cable plug bolt to mechanically connect the insulating body of the cable plug to the high-voltage cable terminal head, and tighten it until the plug fits tightly against the cable sheath without any loose gaps.

[0134] ② Connect the first capacitor in the signal coupling module to the protection control module 12 through the middle bolt structure.

[0135] ③ Using the small handle on the protection control module, align the connected first capacitor and the protection control module together with the opening of the receiving chamber of the cable plug insulation body, and secure them to the metal connector (metal stud) inside the plug through the bolt structure, so that the first end of the first capacitor is in reliable contact with the metal stud.

[0136] ④ Pass the connecting wire through the SMA terminal outlet of the cable plug and finally connect it to the broadband impedance spectrum analyzer.

[0137] ⑤ Connect the ground wire by passing the connecting wire out of the ground wire terminal outlet of the cable plug and finally connecting it to the ground wire.

[0138] ⑥ Close the cover. Tighten the sealing cover using the threads.

[0139] After completing the above installation steps, the high-voltage cable broadband impedance online test signal coupling device and the cable plug form an integrated structure, which not only ensures the mechanical stability and electrical reliability of each component, but also meets the safe operation requirements of the high-voltage site through sealing, grounding and other designs, and can be directly put into the online testing of high-voltage cable broadband impedance.

[0140] The measurement process for the broadband impedance spectrum of a cable is as follows:

[0141] The high-voltage cable is de-energized and the residual voltage is released.

[0142] A small-amplitude AC sinusoidal signal and an incident signal of different frequencies are applied to the high-voltage cable using a broadband impedance spectrum analyzer.

[0143] For each measurement point within the measurement frequency range, the reflected signal after the incident signal passes through the high-voltage cable is detected.

[0144] By calculating and processing the incident and reflected signals, the impedance at each frequency measurement point can be obtained, thus forming an impedance spectrum.

[0145] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A signal coupling device for online testing of broadband impedance of high-voltage cables, characterized in that, include: Signal coupling module and protection control module; The signal coupling module is connected between the high-voltage cable and the broadband impedance spectrum tester. The signal coupling module is used to attenuate and suppress the high-voltage low-frequency signal from the high-voltage cable, and at the same time to couple and conduct the low-voltage high-frequency signal used in the broadband impedance spectrum test. The protection control module is connected to the signal coupling module, and the protection control module includes a control unit and a controlled switch unit; The control unit is connected to the controlled switch unit and is used to generate and output a shutdown command when the voltage of the high-voltage cable changes from an unvoltageed state to a voltaged state; and to generate and output a conduction command after delaying a preset time and confirming that the voltage of the high-voltage cable remains in the voltaged state after generating the shutdown command. The controlled switch unit is connected in series in the output path of the signal coupling module and connected to the control unit. It is used to respond to the shutdown command to cut off the signal path from the signal coupling module to the broadband impedance spectrum tester, or to respond to the turn-on command to turn on the signal path.

2. The high-voltage cable broadband impedance online test signal coupling device according to claim 1, characterized in that, The signal coupling module includes a first capacitor, a first resistor, a second capacitor, and a second resistor; The first terminal of the first capacitor is connected to the high-voltage cable, the second terminal of the first capacitor is connected to the first terminal of the first resistor, and the second terminal of the first resistor is grounded. The first terminal of the second capacitor is connected to the second terminal of the first capacitor, the second terminal of the second capacitor is connected to the first terminal of the second resistor and the broadband impedance spectrum analyzer, and the second terminal of the second resistor is grounded.

3. The high-voltage cable broadband impedance online test signal coupling device according to claim 2, characterized in that, The controlled switch unit includes a selector switch; the selector switch has a common terminal, a normally closed contact, and a normally open contact; The normally open contact of the selector switch is connected to the first terminal of the second capacitor; The common terminal of the selection switch is connected to the second terminal of the first capacitor; The normally closed contact of the selector switch is either left floating or grounded.

4. The high-voltage cable broadband impedance online test signal coupling device according to claim 3, characterized in that, The controlled switch unit further includes a control coil, which is connected to the control unit and is used to receive the off command or the on command. When the control unit outputs the shutdown command, the control coil is de-energized, and the common terminal is connected to the normally closed contact to cut off the signal path. When the control unit outputs the conduction command, the control coil is energized, and the common terminal is connected to the normally open contact to conduct the signal path.

5. The high-voltage cable broadband impedance online test signal coupling device according to claim 1, characterized in that, The protection and control module also includes a high-voltage power supply unit; The input terminal of the high-voltage power extraction unit is connected to the high-voltage cable, and the output terminal of the high-voltage power extraction unit is connected to the control unit and the controlled switch unit. It is used to convert the AC voltage of the high-voltage cable into DC voltage to power the controlled switch unit and to monitor the voltage status of the high-voltage cable.

6. A cable plug, characterized in that, Includes the high-voltage cable broadband impedance online test signal coupling device as described in any one of claims 1-5; The cable plug includes an insulating body and a metal connector disposed within the insulating body; The first end of the metal connector is used to connect to the high-voltage cable, and the second end is connected to the first end of the first capacitor in the high-voltage cable broadband impedance online test signal coupling device.

7. The cable plug according to claim 6, characterized in that, The metal connector is a metal stud extending from the insulating body; The first terminal of the first capacitor is connected to the high-voltage cable via the metal stud.

8. The cable plug according to claim 7, characterized in that, The protection and control module in the high-voltage cable broadband impedance online test signal coupling device is encapsulated in a modular housing, which is connected to the second end of the first capacitor via a bolt structure.

9. The cable plug according to claim 8, characterized in that, The modular housing is equipped with a signal output interface for connecting a broadband impedance spectrum analyzer. And / or, the modular housing is internally encapsulated with insulating encapsulation material.

10. The cable plug according to claim 8, characterized in that, The cable plug also includes a removable sealing cap for sealing the cavity containing the protection control module.

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