Cable identification device and power operation and maintenance detection equipment

Abstract

This application discloses a cable identification device and a power system operation and maintenance testing equipment, relating to the field of power system testing technology. The device includes: a signal injection end comprising an isolation step-down unit and a simulated current-limiting unit; the isolation step-down unit is connected to a power frequency AC power supply and outputs a safe power frequency voltage; the simulated current-limiting unit injects a controlled detection signal with the same frequency as the power supply network into the cable to be identified based on this voltage; and a signal receiving end comprising a magnetic field induction unit, a filtering unit, and an amplitude recognition unit; the magnetic field induction unit converts the magnetic field into an induced electrical signal; the filtering unit performs same-frequency narrowband filtering; and the amplitude recognition unit identifies the filtered signal based on a preset amplitude and outputs the identification result. This application achieves same-frequency controlled signal injection and amplitude recognition through an analog architecture, enabling accurate identification of cables in complex energized environments.

Description

Technical Field

[0001] This application relates to the field of power system testing technology, and in particular to a cable identification device and power operation and maintenance testing equipment. Background Technology

[0002] Cable identification is a crucial step in the operation, maintenance, and upgrading of power distribution networks. With the expansion of low-voltage distribution networks, cable laying in the field is becoming increasingly dense, often accompanied by situations where non-target cables remain energized. Existing cable identification technologies typically employ a dedicated signal generator to inject a specific frequency or phase detection signal into the target cable, followed by matching and identification at the receiving end.

[0003] However, existing methods often rely on complex controllers, relay matrices, and frequency converters / phase shifters to achieve multi-channel switching and interference suppression, resulting in complex equipment structures and cumbersome operation. Furthermore, if a signal with the same frequency as the power grid is used for identification to reduce equipment complexity, it is highly susceptible to interference from strong power frequency currents in operating cables. Existing receiver circuits struggle to effectively distinguish between injected signals and high-intensity environmental interference signals under the same frequency conditions, leading to misjudgments or missed detections. Therefore, there is an urgent need for a cable identification device capable of safe and accurate identification in complex energized environments with a minimalist hardware architecture. Summary of the Invention

[0004] In view of the above problems, this application provides a cable identification device and power operation and maintenance testing equipment to achieve low-cost and accurate cable identification in complex energized environments. The specific solution is as follows:

[0005] The first aspect of this application provides a cable identification device, comprising:

[0006] Signal injection end and signal receiving end;

[0007] The signal injection terminal includes an isolation step-down unit and an analog current limiting unit. The input terminal of the isolation step-down unit is electrically connected to the power frequency AC power supply, and the output terminal of the isolation step-down unit is electrically connected to the input terminal of the analog current limiting unit.

[0008] The signal receiving end includes: a magnetic field sensing unit, a filtering unit, and an amplitude recognition unit. The output end of the magnetic field sensing unit is electrically connected to the input end of the filtering unit, and the output end of the filtering unit is electrically connected to the input end of the amplitude recognition unit.

[0009] In identification mode, the isolation step-down unit isolates and steps down the power frequency voltage of the power frequency AC power supply to output a safe power frequency voltage. The analog current limiting unit adjusts the impedance of the safe power frequency voltage and injects a controlled detection signal with the same frequency as the power supply network into the cable to be identified. The magnetic field sensing unit identifies the magnetic field signal of the cable to be identified and outputs it as an induced electrical signal. The filtering unit performs narrowband filtering on the induced electrical signal at the same frequency and inputs the obtained filtered signal into the amplitude identification unit. The amplitude identification unit identifies the amplitude of the filtered signal and outputs the identification result when the amplitude is not greater than a preset amplitude threshold, wherein the preset amplitude threshold is the maximum amplitude of the controlled detection signal.

[0010] In one possible implementation, the isolated buck unit includes:

[0011] An isolation transformer, wherein the primary winding of the isolation transformer is connected to the power frequency AC power supply, and the secondary winding of the isolation transformer is electrically connected to the input terminal of the simulated current limiting unit.

[0012] In one possible implementation, the simulated current limiting unit includes:

[0013] A multi-level impedance adjustment component is connected in series between the secondary winding of the isolation transformer and the cable to be identified. The multi-level impedance adjustment component is used to adjust the amplitude of the controlled detection signal by switching different impedance levels.

[0014] In one possible implementation, the multi-level impedance adjustment component includes:

[0015] Multiple fixed resistors and a range selector switch, each fixed resistor having a different resistance value;

[0016] One end of each of the fixed resistors is electrically connected to each other, and the other end of each of the fixed resistors is respectively connected to multiple stationary contacts of the gear shift switch. The moving contact of the gear shift switch is connected to the output terminal of the multi-gear impedance adjustment component.

[0017] In one possible implementation, the amplitude recognition unit includes:

[0018] Comparator, transistor and audio-visual prompt circuit;

[0019] The inverting input of the comparator is electrically connected to the output of the filter unit, and the non-inverting input of the comparator is electrically connected to the reference voltage input. The voltage amplitude output by the reference voltage input is the preset amplitude threshold.

[0020] The output of the comparator is connected to the base of the transistor;

[0021] The audible and visual prompt circuit is connected in series in the collector circuit of the transistor. The audible and visual prompt circuit is used to turn on when the comparator outputs a high-level signal and output an audible and visual prompt signal.

[0022] In one possible implementation, the filtering unit includes:

[0023] An inductor and a capacitor, wherein the inductor and the capacitor are connected in series to form a narrowband filter circuit;

[0024] The input terminal of the narrowband filter circuit is electrically connected to the output terminal of the magnetic field sensing unit, and the output terminal of the narrowband filter circuit is electrically connected to the input terminal of the amplitude recognition unit. The narrowband filter circuit is used to filter out non-power frequency stray electromagnetic interference in the induced electrical signal.

[0025] In one possible implementation, the magnetic field sensing unit includes:

[0026] Clamp-on current transformer and operational amplifier;

[0027] The input terminal of the operational amplifier is electrically connected to the output terminal of the clamp-on current transformer. The operational amplifier is used to amplify the weak electrical signal collected by the clamp-on current transformer with low noise and output the induced electrical signal.

[0028] In one possible implementation, the isolated buck unit further includes:

[0029] Overcurrent protection fuses, short-circuit protection miniature circuit breakers, current-limiting resistors, and overload indicator lights;

[0030] The overcurrent protection fuse and the short-circuit protection miniature circuit breaker are connected in series in the main circuit between the power frequency AC power supply and the primary winding;

[0031] The current-limiting resistor and the overload indicator light are connected in series to form an indicator branch. The indicator branch is connected in parallel between the output terminal of the short-circuit protection miniature circuit breaker and the grounding point. The indicator branch is used to provide a light alarm when the circuit is overloaded.

[0032] In one possible implementation, the simulated current limiting unit further includes:

[0033] A current discharge diode is connected in parallel between the output terminal of the multi-level impedance adjustment component and the grounding point. The current discharge diode is used to release residual charge when the multi-level impedance adjustment component is activated or the cable identification device is started or stopped.

[0034] The second aspect of this application provides a power operation and maintenance testing device, including: a cable identification device as described in the first aspect or any implementation thereof.

[0035] By employing the above technical solution, the cable identification device and power operation and maintenance testing equipment provided in this application isolate and step down the power frequency AC power supply through an isolation step-down unit and output a safe power frequency voltage. After impedance adjustment by an analog current limiting unit, a controlled detection signal with the same frequency as the power supply network is injected into the cable to be identified. At the receiving end, the magnetic field signal is converted into an induced electrical signal by a magnetic field induction unit. After being filtered by a filter unit, the amplitude identification unit identifies the cable based on a preset amplitude threshold and outputs the identification result. The above-mentioned pure analog hardware architecture eliminates the need for complex digital controllers and frequency conversion / phase shifting circuits. Electrical isolation is achieved by using isolation step-down to ensure operational safety. The use of a controlled detection signal with the same frequency as the power supply network simplifies the signal source design. Through the coordinated use of the same-frequency narrowband filter and the preset amplitude threshold, strong power frequency interference signals and environmental noise of the operating cable are effectively filtered out based on the interval screening of physical amplitude without relying on frequency or phase differences. This solves the problem of distinguishing between controlled detection signals and strong interference signals under the same frequency conditions, and realizes safe and accurate cable identification in complex live environments. Attached Figure Description

[0036] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. Throughout the drawings, the same or similar reference numerals denote the same or similar elements. It should be understood that the drawings are schematic, and the originals and elements are not necessarily drawn to scale.

[0037] Figure 1 A structural block diagram of a cable identification device provided in this application;

[0038] Figure 2 A circuit diagram of an isolation transformer provided in this application;

[0039] Figure 3 A circuit diagram of an analog current limiting circuit provided in this application;

[0040] Figure 4 A circuit diagram of an amplitude recognition unit provided in this application;

[0041] Figure 5 A circuit diagram of a magnetic field sensing unit provided in this application;

[0042] Figure 6 A circuit diagram of a cable identification device provided in this application. Detailed Implementation

[0043] The embodiments of this application are described below with reference to the accompanying drawings. The terminology used in the implementation section of this application is for explaining specific embodiments only and is not intended to limit the scope of this application.

[0044] As will be known to those skilled in the art, with the development of technology and the emergence of new scenarios, the technical solutions provided in the embodiments of this application are also applicable to similar technical problems.

[0045] The terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms are interchangeable where appropriate; this is merely a way of distinguishing objects with the same attributes in the embodiments of this application. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, so that a process, method, system, product, or apparatus that comprises a series of elements is not necessarily limited to those elements, but may include other elements not explicitly listed or inherent to those processes, methods, products, or apparatuses.

[0046] The first aspect of this application provides a cable identification device, the structural block diagram of which is shown below. Figure 1 As shown, the cable identification device includes:

[0047] Signal injection terminal 11 and signal receiving terminal 12;

[0048] The signal injection terminal 11 includes: an isolation step-down unit 111 and an analog current limiting unit 112. The input terminal of the isolation step-down unit 111 is electrically connected to the power frequency AC power supply, and the output terminal of the isolation step-down unit 111 is electrically connected to the input terminal of the analog current limiting unit 112.

[0049] The signal receiving end 12 includes: a magnetic field sensing unit 121, a filtering unit 122 and an amplitude recognition unit 123. The output end of the magnetic field sensing unit 121 is electrically connected to the input end of the filtering unit 122, and the output end of the filtering unit 122 is electrically connected to the input end of the amplitude recognition unit 123.

[0050] In the identification mode, the isolation step-down unit 111 isolates and steps down the power frequency voltage of the power frequency AC power supply to output a safe power frequency voltage. The analog current limiting unit 112 adjusts the impedance of the safe power frequency voltage and injects a controlled detection signal with the same frequency as the power supply network into the cable to be identified. The magnetic field induction unit 121 outputs the magnetic field signal of the identified cable as an induced electrical signal. The filtering unit 122 performs narrowband filtering on the induced electrical signal at the same frequency and inputs the obtained filtered signal into the amplitude identification unit 123. The amplitude identification unit 123 identifies the amplitude of the filtered signal and outputs the identification result when the amplitude is not greater than the preset amplitude threshold. The preset amplitude threshold is the maximum amplitude of the controlled detection signal.

[0051] It should be noted that in practical applications, the aforementioned power frequency AC power supply refers to an AC power supply with a frequency of 50Hz (or 60Hz) in the power system, such as the common 220V / 380V mains power. The aforementioned isolation step-down unit 111 is a device used to physically disconnect the direct electrical connection between the primary high-voltage side and the secondary low-voltage side, converting the mains power into a low-voltage power frequency signal that is safe for humans and equipment. This safe power frequency voltage amplitude is much lower than the mains voltage, for example, it can be reduced to the AC voltage within the safe extra-low voltage (SELV) range. Because the safe power frequency voltage is lower than the mains voltage, it eliminates the risk of electric shock during operation while preserving the signal's power frequency characteristics, allowing it to be stably transmitted in the cable without causing severe skin effect or radiation loss due to excessively high frequency.

[0052] It should be noted that in practical applications, the aforementioned power supply network frequency is the frequency of the aforementioned industrial frequency AC power supply (e.g., 50Hz). The aforementioned controlled detection signal refers to an industrial frequency current signal whose amplitude is actively controlled by the impedance adjustment of the analog current limiting unit 112, rather than a signal with a fixed amplitude. This application configures the analog current limiting unit 112 to perform impedance adjustment on the safe industrial frequency voltage, ensuring that the controlled detection signal is sufficient for effective detection by the signal receiver without damaging the cable insulation or interfering with the normal operation of the power grid. Furthermore, since the aforementioned controlled detection signal has the same frequency as the power supply network, identification interference from different frequency signal sources is avoided.

[0053] It should be noted that, in practical applications, the aforementioned magnetic field sensing unit 121 is a device used to convert the spatial magnetic field information generated by the controlled detection signal of the cable to be identified into a processable electrical signal. The aforementioned magnetic field sensing unit 121 adopts a non-contact structure to enable on-site detection without damaging the cable sheath, thereby improving detection safety.

[0054] It should be noted that, in practical applications, the aforementioned filtering unit 122 is a device for performing same-frequency narrowband filtering on the induced electrical signal. Same-frequency narrowband filtering refers to a filtering technique that only allows signals with the same frequency as the power frequency (e.g., 50Hz) to be output. Since the environment is filled with background noise signals such as ambient electromagnetic noise, residual voltage, and thermal noise from the circuit itself, and the amplitude of these background noise signals is usually smaller than the amplitude of the controlled detection signal, this application uses the filtering unit 122 to perform same-frequency narrowband filtering on the induced electrical signal, thereby removing background noise outside the power frequency and providing a clean signal base for subsequent identification.

[0055] It should be noted that, in practical applications, the amplitude recognition unit 123 is a device that identifies the amplitude of the filtered signal and outputs the recognition result. The preset amplitude threshold is the maximum amplitude of the controlled detection signal, used to filter out interference signals from operating cables with amplitudes greater than the controlled detection signal. The operating cable interference signal refers to the electrical signal induced at the receiving end by the power frequency magnetic field generated by the load current flowing through other operating cables not being identified. The load current of these operating cables is usually much greater than the injected controlled detection signal, and the amplitude of the induced interference signal is correspondingly much greater than the amplitude of the controlled detection signal. This application configures the filtering unit 122 to perform same-frequency narrowband filtering on the induced electrical signal to eliminate background noise, and configures the amplitude recognition unit 123 to identify the amplitude of the filtered signal. When the amplitude is not greater than the preset amplitude threshold, it outputs the recognition result, thereby achieving high signal-to-noise ratio recognition without changing the signal frequency. This avoids the shortcomings of traditional single-threshold schemes that cannot distinguish between strong and weak same-frequency signals, improving recognition accuracy.

[0056] This application improves operational safety during the identification process by isolating and stepping down the power frequency AC power supply through an isolation step-down unit to output a safe power frequency voltage. Subsequently, after impedance adjustment of the safe power frequency voltage by a simulated current limiting unit, a controlled detection signal with the same frequency as the power supply network is injected into the cable to be identified. This ensures that the controlled detection signal is sufficient for effective detection by the signal receiver without damaging the cable insulation or interfering with the normal operation of the power grid. Furthermore, by configuring a magnetic field induction unit to convert the magnetic field signal into an induced electrical signal, and then using a filtering unit to perform same-frequency narrowband filtering on the induced electrical signal, noise signals outside the power frequency are removed, providing a clean signal base for subsequent identification. Further, by configuring a filtering unit to perform same-frequency narrowband filtering on the induced electrical signal to eliminate background noise, and configuring an amplitude recognition unit to identify the amplitude of the filtered signal, the recognition result is output when the amplitude does not exceed a preset amplitude threshold. This achieves high signal-to-noise ratio identification without changing the signal frequency, avoiding the shortcomings of traditional single-threshold schemes that cannot distinguish between strong and weak same-frequency signals, thus improving identification accuracy. Therefore, this application achieves safe and accurate cable identification in complex energized environments.

[0057] In one possible implementation, the isolation buck unit 111 includes:

[0058] An isolation transformer is provided, with its primary winding connected to a power frequency AC power source and its secondary winding electrically connected to the input terminal of the analog current limiting unit 112.

[0059] It should be noted that in practical applications, the aforementioned isolation transformer not only performs voltage transformation but also achieves electrical isolation between the primary high-voltage side and the secondary low-voltage side. This isolates and cuts off the direct conductive path between the mains power and the detection circuit. Even if a person touches the circuit or a grounding fault occurs during operation, it can effectively prevent the formation of dangerous currents, thus ensuring detection safety. Furthermore, while converting the high-voltage mains power into a safe power frequency voltage suitable for subsequent circuit processing, the isolation transformer also retains the power frequency characteristics of the signal, enabling it to be transmitted without loss in the cable to be identified.

[0060] It should be noted that there are various deployment methods for the aforementioned isolation transformers in practical applications. One example is provided here: Figure 2 The diagram shows a circuit diagram of an isolation transformer. The first terminal of the primary side of the isolation transformer T1 is electrically connected to the positive terminal L of a power frequency AC power supply (e.g., 220V AC) via a fuse F1 and a switch QF1 with an indicator light. The second terminal of the primary side is electrically connected to the negative terminal N of the power frequency AC power supply. The first and second terminals of the secondary side of the isolation transformer T1 constitute the output terminals of the isolation step-down unit 111, outputting a safe power frequency voltage (e.g., 12V AC). To facilitate indication of the current energized state of the device, an indicator light branch can be provided. This branch includes a step-down resistor R1 connected in series and an indicator light LED1. The first terminal of the step-down resistor R1 is electrically connected to the switch QF1 when QF1 is open. The second terminal of the step-down resistor R1 is electrically connected to the first terminal of the indicator light LED1, and the second terminal of the indicator light LED1 is electrically connected to the negative terminal N of the power frequency AC power supply. For easy differentiation, the indicator light color of the switch QF1 is different from the color of the indicator light LED1. When switch QF1 is in the closed state, the indicator light of switch QF1 lights up, the isolation transformer T1 is powered on and running, and the indicator light LED1 turns off. When switch QF1 is in the open state, the indicator light of switch QF1 turns off, the isolation transformer T1 is powered off, and the indicator light LED1 lights up.

[0061] In one possible implementation, the simulated current limiting unit 112 includes:

[0062] A multi-stage impedance adjustment component is connected in series between the secondary winding of the isolation transformer and the cable to be identified. The multi-stage impedance adjustment component is used to adjust the amplitude of the controlled detection signal by switching different impedance stages.

[0063] It should be noted that in practical applications, existing technologies often use digital controllers in conjunction with relay matrices or power electronic devices for automatic adjustment. However, the aforementioned automatic adjustment relies on relatively complex control algorithms, resulting in high development costs. Furthermore, digital circuits are at risk of crashing or malfunctioning in environments with strong electromagnetic interference (such as cable wells). Therefore, this application, by configuring the aforementioned multi-level impedance adjustment component, adjusts the amplitude of the controlled detection signal based on Ohm's law by switching between different impedance levels. This eliminates the need to construct complex digital circuits with poor anti-interference capabilities, while still ensuring accurate adjustment of the controlled detection signal and preventing excessive current from damaging the cable insulation.

[0064] In one possible implementation, the multi-stage impedance adjustment component includes:

[0065] Multiple fixed resistors and a range selector switch, each with a different resistance value;

[0066] One end of each fixed resistor is electrically connected to the other end, and the other end of each fixed resistor is connected to multiple stationary contacts of the gear shift switch. The moving contact of the gear shift switch is connected to the output terminal of the multi-gear impedance adjustment component.

[0067] It should be noted that, in practical applications, the types of fixed resistors mentioned above can be varied, including but not limited to: high-power cement resistors (power levels not less than 30W), wire-wound resistors, and metal-cased resistors. The types of range switches mentioned above can also be varied, including but not limited to: rotary band switches, DIP switches, and rocker switches. Preferably, high-power cement resistors can be used as fixed resistors to leverage their adaptability to low-frequency, high-current, frequent load switching, and surge-impact conditions, thereby improving the operational reliability of the device. Rotary band switches can be selected as range switches to utilize their tactile feedback, multiple ranges, and ability to withstand large currents, thereby improving detection reliability in low-light environments (such as cable wells).

[0068] It should be noted that, in practical applications, the circuit structure of the above-mentioned analog current limiting unit 112 can be varied. Here, one example is provided:

[0069] like Figure 3The diagram shows a circuit diagram of a simulated current limiting circuit 112. The simulated current limiting unit includes: a first fixed resistor (10Ω), a second fixed resistor (100Ω), a third fixed resistor (1kΩ), a fourth fixed resistor (10kΩ), and a gear shift switch (S1). The first terminals of the first fixed resistor (10Ω), the second fixed resistor (100Ω), the third fixed resistor (1kΩ), and the fourth fixed resistor (10kΩ) are electrically connected to each other. The second terminals of the first fixed resistor (10Ω), the second fixed resistor (100Ω), the third fixed resistor (1kΩ), and the fourth fixed resistor (10kΩ) are respectively electrically connected to each stationary contact of the gear shift switch (S1). The moving contact lead of the gear shift switch (S1) serves as the output terminal of the multi-gear impedance adjustment component.

[0070] In one possible implementation, the moving contact of the aforementioned gear switching switch can also be electrically connected to the secondary winding of the isolation transformer, and one end of each fixed resistor electrically connected to the other end is electrically connected to the output terminal of the multi-gear impedance adjustment component.

[0071] It should be noted that, in practical applications, this application configures each fixed resistor to be electrically connected at one end, and the other end of each fixed resistor to be connected to multiple stationary contacts of a gear selector switch. The moving contact of the gear selector switch is connected to the output terminal of the multi-gear impedance adjustment component, making each gear independent of the others and avoiding potential contact problems or resistance jumps that may occur when switching multiple resistors in series and parallel. Furthermore, the purely mechanical contact closure method has extremely low on-resistance and extremely high withstand voltage. Compared to semiconductor switching devices commonly used in digital circuits, it has higher robustness in dealing with instantaneous overcurrent or surge impacts, thereby improving the operational reliability of the device.

[0072] In one possible implementation, the amplitude recognition unit 123 includes:

[0073] Comparator, transistor and audio-visual prompt circuit;

[0074] The inverting input of the comparator is electrically connected to the output of the filter unit 122, and the non-inverting input of the comparator is electrically connected to the reference voltage input. The voltage amplitude output from the reference voltage input is a preset amplitude threshold.

[0075] The comparator's output is connected to the transistor's base;

[0076] A sound and light prompt circuit is connected in series in the collector circuit of the transistor. The sound and light prompt circuit is used to turn on when the comparator outputs a high-level signal and outputs a sound and light prompt signal.

[0077] It should be noted that, in practical applications, the aforementioned comparator is a voltage comparator. In actual work environments, the load current carried by other operating cables besides the cable to be identified may reach hundreds of amperes, generating a power frequency magnetic field strength far exceeding the injected controlled detection signal. Therefore, this application configures the inverting input of the comparator to be electrically connected to the output of the filter unit 122, and the non-inverting input of the comparator to be electrically connected to the reference voltage input. The voltage amplitude output from the reference voltage input is set to a preset amplitude threshold, ensuring that the comparator outputs the identification result when the amplitude of the filtered signal is not greater than the voltage amplitude input to the reference voltage input. This utilizes purely analog hardware to achieve graded filtering of signal energy at the physical level, effectively avoiding the risk of misjudgment caused by insufficient sampling rate or algorithm delay in digital processing schemes, and ensuring the uniqueness and accuracy of the identification results in complex energized environments.

[0078] It should be noted that, in practical applications, the circuit structure of the amplitude recognition unit 123 described above can be varied. Here, one example is provided:

[0079] like Figure 4 The diagram shows a circuit diagram of an amplitude recognition unit, which includes a comparator (U2), a transistor (Q), and an audio-visual prompt circuit. The audio-visual prompt circuit includes a buzzer (BZ), a current-limiting resistor (R2), and a light-emitting diode (LED2). The inverting input (-) of the comparator (U2) is electrically connected to the output of the filter unit 122, and the non-inverting input (+) of the comparator (U2) is connected to the reference voltage input (V). th Electrical connection, the operating power receiving terminal of comparator (U2) is connected to the second power supply terminal (V). cc2 The comparator (U2) is electrically connected to the output of the transistor (Q). The collector circuit of the transistor (Q) is connected in series with the control terminal of the buzzer (BZ), the current-limiting resistor (R2), and the control terminal of the light-emitting diode (LED2). The power receiving terminals of the buzzer (BZ) and LED2 are connected to the third power supply terminal (V). cc3 Electrical connection. The amplitude of the filtered signal input to the inverting input (-) of comparator (U2) shall not exceed the amplitude of the reference voltage input (V). th When the preset amplitude threshold is input, the comparator (U2) outputs a high-level signal (i.e., the recognition result) to control the buzzer (BZ) and the light-emitting diode (LED2) to emit sound and light prompt signals.

[0080] In one possible implementation, the filtering unit 122 described above includes:

[0081] Inductors and capacitors, connected in series, form a narrowband filter circuit;

[0082] The input terminal of the narrowband filter circuit is electrically connected to the output terminal of the magnetic field induction unit 121, and the output terminal of the narrowband filter circuit is electrically connected to the input terminal of the amplitude recognition unit 123. The narrowband filter circuit is used to filter out non-power frequency stray electromagnetic interference in the induced electrical signal.

[0083] It should be noted that in practical applications, the induced electrical signal output by the magnetic field induction unit 121 contains background noise signals such as environmental electromagnetic noise, residual voltage, and thermal noise from the circuit itself. If these background noise signals are not filtered out beforehand, their superposition with the power frequency signal will cause abnormal fluctuations in the amplitude of the induced electrical signal, leading to a risk of misjudgment by the amplitude recognition unit 123. Therefore, this application uses a narrowband filter circuit (i.e., an LC series filter circuit) composed of an inductor and a capacitor in series to precisely tune the allowed resonant frequency or passband center to near the power frequency, thereby attenuating the out-of-band background noise signals. This, combined with the amplitude recognition unit, enables accurate identification of the controlled detection signal without relying on complex digital signal processing algorithms, and improves operational reliability under harsh conditions.

[0084] In one possible implementation, the magnetic field sensing unit 121 described above includes:

[0085] Clamp-on current transformer and operational amplifier;

[0086] The input terminal of the operational amplifier is electrically connected to the output terminal of the clamp-on current transformer. The operational amplifier is used to amplify the weak electrical signal collected by the clamp-on current transformer with low noise and output the induced electrical signal.

[0087] It should be noted that in practical applications, the cables to be identified are often densely laid and may carry operating voltage. Traditional closed-type current transformers require disconnecting the cable or separating the wiring harness for installation, which is not only difficult to operate in a live environment but also poses a significant safety risk. In contrast, the open-clamp type current transformer used in this application has a separable magnetic core structure. Operators do not need to disconnect the power or damage the cable insulation; they only need to press the handle with one hand to open the jaws and insert the cable to be identified. After releasing, the magnetic core automatically closes, forming a complete magnetic circuit. This non-contact sensing method not only simplifies the on-site operation process but also avoids power outage losses and safety risks caused by disassembling and installing equipment.

[0088] It should be noted that in practical applications, the aforementioned operational amplifiers can employ op-amp chips with high input impedance, low offset voltage, and low temperature drift characteristics to ensure that no significant additional noise or distortion is introduced when amplifying weak signals at high gain. Since clamp-on current transformers typically use a core made of soft magnetic material with high permeability, when a power frequency current (i.e., the controlled detection signal) flows through the cable to be identified, the alternating magnetic field generated around it passes through the core and induces a weak voltage signal in the secondary winding that is proportional to the primary current. Because the injected controlled detection signal itself has a small amplitude and is attenuated due to the transmission distance, the original electrical signal output by the clamp-on current transformer is often in the millivolt or even microvolt range, making it easily overwhelmed by background noise. Therefore, by configuring the input terminal of the operational amplifier to be electrically connected to the output terminal of the clamp-on current transformer, this application can reduce the signal strength attenuation caused by excessive transmission distance, reduce the parasitic capacitance and electromagnetic interference introduced by long leads, and at the same time, use the operational amplifier to amplify the weak electrical signal with low noise to increase the amplitude of the original electrical signal to the range that the amplitude recognition unit can recognize and process, thereby improving the recognition accuracy of the amplitude recognition unit.

[0089] It should be noted that, in practical applications, the circuit structure of the magnetic field sensing unit 121 can be varied. Here, one example is provided:

[0090] like Figure 5 The diagram shows the circuit of the magnetic field sensing unit 121. This unit includes: a clamp-on current transformer (CT1), a first stabilizing resistor (R3), a second stabilizing resistor (R4), a suppression resistor (R5), a grounding resistor (R6), and an operational amplifier (U1). The first terminal (i+) of the clamp-on current transformer (CT1) is electrically connected to the positive input terminal (+) of the operational amplifier (U1) through the first stabilizing resistor (R3). The second terminal (i-) of the clamp-on current transformer (CT1) is electrically connected to the inverting input terminal (-) of the operational amplifier (U1) through the second stabilizing resistor (R4). The suppression resistor (R5) is connected in series between the inverting input terminal (-) and the output terminal of the operational amplifier (U1). The grounding terminal between the first stabilizing resistor (R3) and the positive input terminal (+) of the operational amplifier (U1) is electrically connected to the first terminal of the grounding resistor (R6). The second terminal of the grounding resistor (R6) is grounded. The receiving terminal of the operational amplifier (U1) is connected to the first supply terminal (V). cc1The electrical connection is as follows: During the detection process, the jitter of the clamp-on current transformer (CT1) can cause voltage fluctuations in the acquired electrical signal. Therefore, the first stabilizing resistor (R3) and the second stabilizing resistor (R4) are used to limit the voltage fluctuations of the input electrical signal, thereby stabilizing the gain. The suppression resistor (R5) is used to suppress the phase lag formed by the output stage and parasitic capacitance, preventing high-frequency self-oscillation. The grounding resistor (R6) is used to match the DC equivalent resistance of the two input terminals to ground, offsetting the output offset voltage caused by the input bias current.

[0091] In one possible implementation, the isolation buck unit 111 further includes:

[0092] Overcurrent protection fuses, short-circuit protection miniature circuit breakers, current-limiting resistors, and overload indicator lights;

[0093] Overcurrent protection fuses and short-circuit protection miniature circuit breakers are connected in series in the main circuit between the power frequency AC power supply and the primary winding;

[0094] The current-limiting resistor and the overload indicator light are connected in series to form an indicator branch. The indicator branch is connected in parallel between the output terminal of the short-circuit protection miniature circuit breaker and the grounding point. The indicator branch is used to provide light alarm when the circuit is overloaded.

[0095] It should be noted that in practical applications, uncertainties such as voltage fluctuations, sudden load changes, or line aging may exist at the power supply point, and the internal components of the device may deteriorate after long-term operation, thus affecting the safety and reliability of the device operation. Therefore, this application implements overload protection by configuring an overcurrent protection fuse. When an overcurrent occurs in the circuit for a relatively long period but does not reach the short-circuit level, the fusible element inside the overcurrent protection fuse will melt due to heat accumulation, thereby cutting off the circuit to prevent insulation damage to the isolation transformer T1 due to prolonged overheating. Short-circuit protection is implemented by configuring a short-circuit protection miniature circuit breaker. Utilizing its electromagnetic tripping mechanism, which can respond to short-circuit faults with currents tens of times greater than the rated current within milliseconds, it achieves rapid circuit disconnection to suppress arc energy and prevent the spread of fire. Furthermore, by utilizing the complementary and cascaded cooperation of the two in terms of their operating characteristics, it avoids the risk of insufficient breaking capacity of a single fuse during a short circuit and overcomes the defect of a single circuit breaker's slow response to minor overloads, thus providing electrical safety assurance for downstream circuits and operators.

[0096] It should be noted that the aforementioned indicator branch is used to monitor the voltage status at the output terminal of the short-circuit protection miniature circuit breaker. When the device is operating normally, the short-circuit protection miniature circuit breaker closes, the two ends of the indicator branch receive the operating voltage, and the overload indicator light illuminates to show that the equipment is in a power-on ready state; if an overload or short circuit occurs, causing the short-circuit protection miniature circuit breaker to trip or the overcurrent protection fuse to blow, the indicator branch loses power, the overload indicator light goes out, thus providing a direct indication of the fault.

[0097] It should be noted that, in practical applications, the specific specifications of the aforementioned overcurrent protection fuses and short-circuit protection miniature circuit breakers can be selected based on the capacity of the isolation transformer and the on-site power supply conditions. For example, time-delay fuses can be used to withstand closing surges, or circuit breakers with leakage protection functions can be used to improve the level of personal safety protection. This application does not impose excessive limitations or elaborate on the specific specifications of the aforementioned overcurrent protection fuses and short-circuit protection miniature circuit breakers.

[0098] In one possible implementation, the analog current limiting unit 112 further includes:

[0099] The current discharge diode is connected in parallel between the output terminal of the multi-stage impedance adjustment component and the grounding point. The current discharge diode is used to release residual charge when the multi-stage impedance adjustment component is activated or when the cable identification device is started or stopped.

[0100] It should be noted that in practical applications, cables exhibit certain inductive load characteristics, and distributed capacitance and parasitic inductance exist in the circuit. When the cable identification device suddenly loses power or switches the range selector while energized, the energy storage element in the circuit releases energy, potentially inducing a reverse electromotive force or transient spike at the switch contacts or output terminal that is much higher than the normal operating voltage. Without an effective discharge path, these transient high voltages can easily cause arcing and erosion of the switch contacts, or even damage the secondary winding of the isolation transformer or other sensitive components. Therefore, this application configures a current-discharge diode connected in parallel between the output terminal of the multi-range impedance adjustment component and the grounding point. When an abnormal negative voltage or positive overshoot occurs at the output terminal, the current-discharge diode quickly conducts, guiding the residual charge to the grounding point, thereby limiting the voltage within a safe range and improving the equipment's lifespan and operational safety.

[0101] To facilitate understanding of the cable identification device provided in the embodiments of this application, a possible implementation of this application will be described below:

[0102] like Figure 6The diagram shown is a circuit diagram of a cable identification device, which includes: a fuse F1, a switch QF1 with an indicator light, a step-down resistor R1, an indicator light LED1, an isolation transformer T1, a first fixed resistor (10Ω), a second fixed resistor (100Ω), a third fixed resistor (1kΩ), a fourth fixed resistor (10kΩ), a gear shift switch (S1), a rectifier diode D1, a clamp-on current transformer (CT1), a first stabilizing resistor (R3), a second stabilizing resistor (R4), a suppression resistor (R5), a grounding resistor (R6), an operational amplifier (U1), an inductor (L1), a capacitor (C1), a comparator (U2), a transistor (Q), and an audio-visual prompting circuit. The audio-visual prompting circuit includes a buzzer (BZ), a current-limiting resistor (R2), and a light-emitting diode (LED2).

[0103] The first terminal of the primary side of isolation transformer T1 is electrically connected to the positive terminal L of the power frequency AC power supply (such as 220V AC) through fuse F1 and switch QF1 with indicator light. The second terminal of the primary side is electrically connected to the negative terminal N of the power frequency AC power supply. The first and second terminals of the secondary side of isolation transformer T1 constitute the output terminal of the isolation step-down unit, outputting a safe power frequency voltage (such as 12V AC). The first terminal of step-down resistor R1 is electrically connected to switch QF1 when switch QF1 is open, and the second terminal of step-down resistor R1 is electrically connected to the first terminal of indicator light LED1. The second terminal is electrically connected to the negative terminal N of the power frequency AC power supply. The moving contact lead of the gear shift switch (S1) serves as the input terminal of the multi-position impedance adjustment component. The input terminal of the multi-position impedance adjustment component is electrically connected to the first terminal of the secondary side of the isolation transformer T1. The first terminals of the first fixed resistor (10Ω), the second fixed resistor (100Ω), the third fixed resistor (1kΩ), and the fourth fixed resistor (10kΩ) are respectively electrically connected to each stationary contact of the gear shift switch (S1). The second terminals of the fixed resistor (1kΩ) and the fourth fixed resistor (10kΩ) are electrically connected to each other and lead out to the output terminal of the multi-stage impedance adjustment component. A rectifier diode D1 is connected in series between the output terminal of the multi-stage impedance adjustment component and the second terminal of the secondary side of the isolation transformer T1. The output terminal of the multi-stage impedance adjustment component and the second terminal of the secondary side of the isolation transformer T1 are connected to the two ends of the cable X to be identified through a clamp. The first terminal (i+) of the open-type clamp-on transformer (CT1) is electrically connected to the positive input terminal (+) of the operational amplifier (U1) through the first stabilizing resistor (R3). The second terminal (i-) of the clamp-on current transformer (CT1) is electrically connected to the inverting input terminal (-) of the operational amplifier (U1) via the second stabilizing resistor (R4). A suppression resistor (R5) is connected in series between the inverting input terminal (-) and the output terminal of the operational amplifier (U1). The grounding terminal between the first stabilizing resistor (R3) and the non-inverting input terminal (+) of the operational amplifier (U1) is electrically connected to the first terminal of the grounding resistor (R6). The second terminal of the grounding resistor (R6) is grounded. The receiving terminal of the operational amplifier (U1) is connected to the first supply terminal (V). cc1 The operational amplifier (U1) is electrically connected to ground via an inductor (L1) and a capacitor (C1) connected in series. The output of the inductor (L1) and capacitor (C1) is electrically connected to the inverting input (-) of the comparator (U2). The non-inverting input (+) of the comparator (U2) is electrically connected to the reference voltage input (V). th Electrical connection, the operating power receiving terminal of comparator (U2) is connected to the second power supply terminal (V). cc2The comparator (U2) is electrically connected to the output of the transistor (Q). The collector circuit of the transistor (Q) is connected in series with the control terminal of the buzzer (BZ), the current-limiting resistor (R2), and the control terminal of the light-emitting diode (LED2). The power receiving terminals of the buzzer (BZ) and LED2 are connected to the third power supply terminal (V). cc3 Electrical connection. This application also provides a power operation and maintenance testing device, including: the cable identification device as provided in this application embodiment. Wherein, the first fixed resistor (10Ω), the second fixed resistor (100Ω), the third fixed resistor (1kΩ), and the fourth fixed resistor (10kΩ) are labeled with their resistance values ​​in parentheses.

Claims

1. A cable identification device, characterized in that, include: Signal injection end and signal receiving end; The signal injection terminal includes an isolation step-down unit and an analog current limiting unit. The input terminal of the isolation step-down unit is electrically connected to the power frequency AC power supply, and the output terminal of the isolation step-down unit is electrically connected to the input terminal of the analog current limiting unit. The signal receiving end includes: a magnetic field sensing unit, a filtering unit, and an amplitude recognition unit. The output end of the magnetic field sensing unit is electrically connected to the input end of the filtering unit, and the output end of the filtering unit is electrically connected to the input end of the amplitude recognition unit. In identification mode, the isolation step-down unit isolates and steps down the power frequency voltage of the power frequency AC power supply to output a safe power frequency voltage. The analog current limiting unit adjusts the impedance of the safe power frequency voltage and injects a controlled detection signal with the same frequency as the power supply network into the cable to be identified. The magnetic field sensing unit identifies the magnetic field signal of the cable to be identified and outputs it as an induced electrical signal. The filtering unit performs narrowband filtering on the induced electrical signal at the same frequency and inputs the obtained filtered signal into the amplitude identification unit. The amplitude identification unit identifies the amplitude of the filtered signal and outputs the identification result when the amplitude is not greater than a preset amplitude threshold, wherein the preset amplitude threshold is the maximum amplitude of the controlled detection signal.

2. The cable identification device according to claim 1, characterized in that, The isolation step-down unit includes: An isolation transformer, wherein the primary winding of the isolation transformer is connected to the power frequency AC power supply, and the secondary winding of the isolation transformer is electrically connected to the input terminal of the simulated current limiting unit.

3. The cable identification device according to claim 2, characterized in that, The simulated current limiting unit includes: A multi-level impedance adjustment component is connected in series between the secondary winding of the isolation transformer and the cable to be identified. The multi-level impedance adjustment component is used to adjust the amplitude of the controlled detection signal by switching different impedance levels.

4. The cable identification device according to claim 3, characterized in that, The multi-level impedance adjustment component includes: Multiple fixed resistors and a range selector switch, each fixed resistor having a different resistance value; One end of each of the fixed resistors is electrically connected to each other, and the other end of each of the fixed resistors is respectively connected to multiple stationary contacts of the gear shift switch. The moving contact of the gear shift switch is connected to the output terminal of the multi-gear impedance adjustment component.

5. The cable identification device according to claim 1, characterized in that, The amplitude recognition unit includes: Comparator, transistor and audio-visual prompt circuit; The inverting input of the comparator is electrically connected to the output of the filter unit, and the non-inverting input of the comparator is electrically connected to the reference voltage input. The voltage amplitude output by the reference voltage input is the preset amplitude threshold. The output of the comparator is connected to the base of the transistor; The audible and visual prompt circuit is connected in series in the collector circuit of the transistor. The audible and visual prompt circuit is used to turn on when the comparator outputs a high-level signal and output an audible and visual prompt signal.

6. The cable identification device according to claim 1 or 5, characterized in that, The filtering unit includes: An inductor and a capacitor, wherein the inductor and the capacitor are connected in series to form a narrowband filter circuit; The input terminal of the narrowband filter circuit is electrically connected to the output terminal of the magnetic field sensing unit, and the output terminal of the narrowband filter circuit is electrically connected to the input terminal of the amplitude recognition unit. The narrowband filter circuit is used to filter out non-power frequency stray electromagnetic interference in the induced electrical signal.

7. The cable identification device according to claim 1, characterized in that, The magnetic field sensing unit includes: Clamp-on current transformer and operational amplifier; The input terminal of the operational amplifier is electrically connected to the output terminal of the clamp-on current transformer. The operational amplifier is used to amplify the weak electrical signal collected by the clamp-on current transformer with low noise and output the induced electrical signal.

8. The cable identification device according to claim 2, characterized in that, The isolation step-down unit further includes: Overcurrent protection fuses, short-circuit protection miniature circuit breakers, current-limiting resistors, and overload indicator lights; The overcurrent protection fuse and the short-circuit protection miniature circuit breaker are connected in series in the main circuit between the power frequency AC power supply and the primary winding; The current-limiting resistor and the overload indicator light are connected in series to form an indicator branch. The indicator branch is connected in parallel between the output terminal of the short-circuit protection miniature circuit breaker and the grounding point. The indicator branch is used to provide a light alarm when the circuit is overloaded.

9. The cable identification device according to claim 3, characterized in that, The simulated current limiting unit further includes: A current discharge diode is connected in parallel between the output terminal of the multi-level impedance adjustment component and the grounding point. The current discharge diode is used to release residual charge when the multi-level impedance adjustment component is activated or the cable identification device is started or stopped.

10. A power operation and maintenance testing device, characterized in that, include: The cable identification device as described in any one of claims 1 to 9.

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