A multi-sensor fusion-based direct current cable leakage current full-band detection method and device

Abstract

The application relates to the technical field of power equipment state monitoring, and discloses a DC cable leakage current full-band detection method and device based on multi-sensor fusion, which comprises the following steps: arranging a fluxgate sensor, a power frequency current transformer and a high-frequency current transformer in series, making the grounding wire of a DC cable pass through the centers of the annular magnetic cores of the three sensors in sequence to form a single series loop; collecting leakage current signals in a DC frequency band by using the fluxgate sensor, collecting leakage current signals in a 50Hz-1kHz frequency band by using the power frequency current transformer, collecting leakage current signals in a 1kHz-30MHz frequency band by using the high-frequency current transformer, and respectively performing low-pass filtering, band-pass filtering and high-pass filtering processing; realizing time domain alignment through a synchronous acquisition unit; and superimposing to generate a composite waveform of full-band leakage current. The application can accurately and non-destructively measure the full-band DC cable leakage current waveform.

Description

Technical Field

[0001] This application relates to the field of power equipment condition monitoring technology, and in particular to a method and device for detecting full-frequency leakage current of DC cables based on multi-sensor fusion. Background Technology

[0002] In modern high-voltage direct current (HVDC) transmission systems, DC cables serve as the core carriers of electrical energy transmission, and their insulation performance directly determines the safety and reliability of the power system. With the rapid development of technologies such as new energy power generation and inter-regional grid interconnection, the application scenarios for HVDC cables are increasing, voltage levels are continuously rising, and operating environments are becoming more complex. Against this backdrop, accurate detection of leakage current has become a crucial means of assessing cable insulation status and predicting potential faults.

[0003] The leakage current of a DC cable is typically composed of both DC and AC components. The dominant DC component is determined by the conductivity of the insulation, reflecting the aging or moisture content of the insulating medium. The AC component, on the other hand, includes power frequency harmonics, transient currents from impulse overvoltages, and high-frequency pulse signals generated by partial discharges, with a frequency range from 50Hz to MHz. Detecting these different components provides complementary value for insulation condition diagnosis. For example, abnormal DC components may indicate overall insulation degradation, while high-frequency AC components are closely related to localized defects such as partial discharges.

[0004] However, current traditional measurement methods mostly use microammeters connected in series in the circuit to measure the leakage current of DC cables. This not only makes it difficult to detect the high-frequency components of the leakage current, but also introduces additional grounding impedance, affecting the grounding structure of the DC cable. The industry urgently needs a detection method that can measure leakage current accurately while solving the problems of affecting the grounding system and the difficulty in measuring across the entire frequency band, in order to meet the needs of intelligent operation and maintenance of high-voltage DC cables. Summary of the Invention

[0005] The purpose of this application is to provide a method and device for full-band detection of leakage current in DC cables based on multi-sensor fusion, so as to develop an accurate, non-destructive, full-band measurement method that can simultaneously diagnose the overall deterioration and local defects of DC cables, thereby enabling timely repair and replacement, and providing an important guarantee for the stable operation of the power grid.

[0006] To achieve the above objectives, the following technical solution is adopted:

[0007] In a first aspect, this application provides a method for detecting the full-frequency band leakage current of DC cables based on multi-sensor fusion, comprising the following steps:

[0008] The fluxgate sensor, power frequency current transformer, and high frequency current transformer are arranged in series, so that the grounding wire of the DC cable passes through the center of the annular magnetic core of the three sensors in sequence, forming a single series circuit.

[0009] The leakage current signal in the DC frequency band is collected using the fluxgate sensor, the leakage current signal in the 50Hz to 1kHz frequency band is collected using the power frequency current transformer, and the leakage current signal in the 1kHz to 30MHz frequency band is collected using the high frequency current transformer.

[0010] The leakage current signal, leakage current signal and leakage current signal are respectively processed by low-pass filtering, band-pass filtering and high-pass filtering, and time-domain alignment is achieved through synchronous acquisition unit, and the composite waveform of leakage current in the whole frequency band is generated by superposition.

[0011] Furthermore, an electromagnetic shielding layer is provided between the fluxgate sensor and the power frequency current transformer, and an isolation layer is provided between the high frequency current transformer and the power frequency current transformer.

[0012] Furthermore, the signal output by the fluxgate sensor is processed by low-pass filtering and amplification with a cutoff frequency of 10Hz to extract the DC component; the signal output by the power frequency current transformer is processed by band-pass filtering and amplification from 50Hz to 1kHz to extract power frequency harmonics and transient overvoltage signals; the signal output by the high frequency current transformer is processed by high-pass filtering and amplification with a cutoff frequency of 1kHz to extract partial discharge signals and transient lightning overvoltage signals.

[0013] Furthermore, the synchronous acquisition unit adopts a multi-channel synchronous acquisition card, wherein the DC channel sampling rate is greater than 1kS / s, the power frequency channel sampling rate is greater than 10kS / s, and the high frequency channel sampling rate is greater than 10MS / s, so as to realize the synchronous time-domain acquisition of three signals.

[0014] Furthermore, when the grounding wire passes through the center of the annular magnetic core of the three sensors, it is fixed by a clamp to ensure that the coaxiality deviation of each sensor magnetic core is ≤0.1mm.

[0015] Secondly, this application provides a DC cable leakage current full-band detection device based on multi-sensor fusion, comprising:

[0016] The sensor group includes a fluxgate sensor, a power frequency current transformer and a high frequency current transformer arranged in series. The center of the annular magnetic core of the fluxgate sensor, the power frequency current transformer and the high frequency current transformer is used to run the grounding wire of the DC cable.

[0017] The electromagnetic compatibility optimization unit includes an electromagnetic shielding layer disposed between the fluxgate sensor and the power frequency current transformer, and an isolation layer disposed between the high frequency current transformer and the power frequency current transformer.

[0018] The signal processing module includes a low-pass filter circuit, a band-pass filter circuit, and a high-pass filter circuit, which are respectively connected to the fluxgate sensor, the power frequency current transformer, and the high frequency current transformer, as well as a synchronous acquisition unit for realizing time-domain alignment of the three signals.

[0019] Furthermore, the fluxgate sensor is installed at the beginning of the grounding wire to detect the DC component.

[0020] The power frequency current transformer is located downstream of the fluxgate sensor. It uses a toroidal ferrite core and covers a frequency band of 50Hz-1kHz. It is used to extract power frequency harmonics and transient signals of operating overvoltage.

[0021] The high-frequency current transformer is installed at the end of the grounding wire, covering a frequency band of 1kHz-30MHz, and is used to extract partial discharge signals and lightning overvoltage transient signals.

[0022] Furthermore, the cutoff frequency of the low-pass filter circuit is 10Hz;

[0023] The cutoff frequency of the bandpass filter circuit is 50Hz to 1kHz;

[0024] The cutoff frequency of the high-pass filter circuit is 1kHz.

[0025] Furthermore, the synchronous acquisition unit employs a multi-channel synchronous acquisition card, wherein the DC channel sampling rate is greater than 1 kS / s, the power frequency channel sampling rate is greater than 10 kS / s, and the high-frequency channel sampling rate is greater than 10 MS / s, to achieve synchronous time-domain acquisition of three signals; wherein, the DC channel is the channel connecting the multi-channel synchronous acquisition card to the fluxgate sensor, the power frequency channel is the channel connecting the multi-channel synchronous acquisition card to the power frequency current transformer, and the high-frequency channel is the channel connecting the multi-channel synchronous acquisition card to the high-frequency current transformer.

[0026] Furthermore, when the grounding wire passes through the center of the annular magnetic core of the three sensors, it is fixed by a clamp to ensure that the coaxiality deviation of each sensor core is ≤0.1mm.

[0027] This application enables accurate and non-destructive full-frequency measurement of leakage current in DC cables, and has the following significant technical advantages:

[0028] (1) Full-band coverage: One-time detection of DC to 30MHz full-band signals, enabling synchronous detection and analysis of DC leakage, power frequency harmonics and partial discharge.

[0029] (2) Simplified structure: Multiple sensors are connected in series with a common ground wire, reducing installation space and cost, eliminating positional errors and redundant layout.

[0030] (3) Non-destructive testing: The grounding wire is passed through the coil of the multi-sensor. Compared with the traditional measurement method of connecting the microammeter in series with the ground wire, this avoids the impact on the original grounding system of the cable.

[0031] (4) Anti-interference capability: By eliminating grounding impedance differences and using frequency division filtering and signal isolation technology, crosstalk between AC and DC components is suppressed. Attached Figure Description

[0032] Figure 1 A schematic diagram of the sensor group structure of a DC cable leakage current full-band detection device based on multi-sensor fusion according to an embodiment of this application is shown;

[0033] Figure 2 A structural diagram of the signal processing module of a DC cable leakage current full-band detection device based on multi-sensor fusion according to an embodiment of this application is shown;

[0034] Figure 3 The diagram shows a structural diagram of the signal processing module of a DC cable leakage current full-band detection device based on multi-sensor fusion according to an embodiment of this application, when an amplification circuit is provided.

[0035] Figure 4 A flowchart of a method for detecting full-band leakage current of DC cables based on multi-sensor fusion according to an embodiment of this application is shown;

[0036] Figure 5 Another flowchart of a method for detecting full-band leakage current of DC cables based on multi-sensor fusion according to an embodiment of this application is shown. Detailed Implementation

[0037] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0038] The specific implementation methods of this application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0039] Example 1:

[0040] This application provides a multi-sensor fusion-based full-frequency detection device for DC cable leakage current, enabling full-frequency detection of DC cable leakage current. It achieves synchronous high-precision detection of AC and DC components through a series common-ground configuration of a fluxgate sensor, a power frequency current transformer (CT), and a high-frequency current transformer (HFCT), combined with frequency division signal processing technology. The device includes a sensor group 100, an electromagnetic compatibility optimization unit 200, and a signal processing module 300.

[0041] like Figure 1 As shown, the sensor group 100 is installed inside an electromagnetic shielding housing 400. The sensor group 100 includes a fluxgate sensor 101, a power frequency current transformer 102, and a high frequency current transformer 103 arranged in series. The annular magnetic core center 104 of the fluxgate sensor 101, the power frequency current transformer 102, and the high frequency current transformer 103 is used to run the grounding wire of the DC cable. The electromagnetic compatibility optimization unit 200 includes an electromagnetic shielding layer 201 disposed between the fluxgate sensor and the power frequency current transformer, and an isolation layer 202 disposed between the high frequency current transformer and the power frequency current transformer.

[0042] like Figure 2 As shown, the signal processing module 300 includes a low-pass filter circuit 301, a band-pass filter circuit 302, and a high-pass filter circuit 303, which are respectively connected to the fluxgate sensor 101, the power frequency current transformer 102, and the high frequency current transformer 103, as well as a synchronous acquisition unit 304 for realizing time-domain alignment of the three signals.

[0043] This embodiment employs a series-connected multi-sensor fusion design of a fluxgate sensor 101, a power frequency current transformer 102, and a high-frequency current transformer 103. Combined with precise interlayer electromagnetic shielding / isolation and overall external shielding, it effectively solves the two core challenges of frequency band coverage and electromagnetic compatibility in broadband (DC-MHz) leakage current measurement. Furthermore, targeted frequency division filtering and rigorous synchronous acquisition achieve full-frequency, high-precision, low-noise, and time-synchronized measurement of leakage current in DC cable grounding wires. This provides a powerful technical means for comprehensively assessing cable insulation health, especially for the early detection of different types of defects such as electrochemical aging, moisture absorption, and partial discharge, significantly improving the level and reliability of power cable condition monitoring and fault early warning.

[0044] Specifically, sensor group 100 is used to achieve multi-band signal acquisition. Fluxgate sensor 101 is used to detect weak leakage current in the extremely low frequency band. It is highly sensitive to slowly varying currents in the DC and near-DC ranges, and can accurately measure the minute DC or ultra-low frequency components generated by the electrochemical aging of cable insulation materials. Power frequency current transformer 102 is used to detect leakage current components in the power frequency and its lower harmonics. This is the main frequency band for detecting significant increases in leakage current caused by overall insulation dampness, contamination, or concentrated defects (such as penetrating water trees). High-frequency current transformer 103 is used to detect high-frequency leakage current pulses, mainly corresponding to the steep pulse current signals generated by partial discharge (PD) in the cable, and is an important indicator of the presence of microscopic defects such as air gaps, impurities, and spikes within the insulation. The three sensors are connected in series on the same grounding wire of the DC cable. This structure ensures that they measure the exact same grounding wire current path, providing a physical basis for subsequent multi-source signal fusion.

[0045] The electromagnetic shielding layer 201 is used to prevent the strong alternating magnetic field generated by the power frequency CT from interfering with the fluxgate sensor, which is extremely sensitive to magnetic fields, ensuring that the fluxgate can accurately measure weak low-frequency / DC signals. The isolation layer 202 suppresses the interference of the strong high-frequency electromagnetic field generated during the operation of the high-frequency CT on the power frequency CT, and also reduces the potential saturation effect of the power frequency magnetic field on the high-frequency CT. This isolation layer typically has high-frequency absorption or reflection characteristics.

[0046] The electromagnetic shielding shell 400 encloses the entire sensor group, shielding it from external electromagnetic interference and also suppressing the magnetic field generated by the internal sensors from radiating outwards and interfering with other equipment.

[0047] The signal processing module 300 is used to achieve signal conditioning and fusion. The low-pass filter circuit 301 is connected to the fluxgate sensor 101, allowing only low-frequency / DC signals to pass through while filtering out high-frequency noise and interference. The band-pass filter circuit 302 is connected to the power frequency current transformer 102, with a center frequency near the power frequency and a bandwidth covering its key harmonics, filtering out stray signals outside the power frequency range. The high-pass filter circuit 303 is connected to the high-frequency current transformer 103, filtering out low-frequency and power frequency signals, retaining only high-frequency pulse components, and improving the signal-to-noise ratio.

[0048] The synchronous acquisition unit 304 is crucial for achieving full-band information fusion. It uses the same clock source to simultaneously and in phase sample three filtered signals at high speed, ensuring time-domain alignment and phase consistency. Time-domain alignment means that different frequency events occurring on the grounding wire at the same time can be accurately mapped to the same time point in the three signals. Phase consistency refers to maintaining the correct phase relationship for periodic signals.

[0049] In some embodiments, the fluxgate sensor 101 is installed at the beginning of the grounding wire and is used to detect the DC component. The power frequency current transformer 102, located downstream of the fluxgate sensor 101, uses a toroidal ferrite core and covers a frequency band of 50Hz-1kHz, and is used to extract power frequency harmonics and transient signals of operational overvoltage. The high-frequency current transformer 103 is installed at the end of the grounding wire and covers a frequency band of 1kHz-30MHz, and is used to extract partial discharge signals and transient signals of lightning overvoltage.

[0050] In some embodiments, the grounding wire of the DC cable passes sequentially through the center of the ring core of the three sensors to form a single series loop, eliminating the problem of different grounding impedances caused by the different installation positions of the multiple sensors.

[0051] In some embodiments, a shielding layer is provided between the fluxgate sensor 101 and the power frequency current transformer 102, and between the power frequency current transformer 102 and the high frequency current transformer 103, and a metal shield is provided outside the coil to suppress mutual influence between signals and interference from external signals.

[0052] In some embodiments, such as Figure 3 As shown, the output signal of fluxgate sensor 101 is filtered by a low-pass filter circuit 301 with a cutoff frequency of 10Hz and an integrating amplifier circuit 305 to extract the DC component. The output signal of power frequency current transformer 102 is filtered by a band-pass filter circuit 302 with a cutoff frequency of 50Hz-1kHz and a first amplifier 306 to extract the signal waveform. The output signal of high-frequency current transformer 103 is filtered by a high-pass filter circuit 303 with a cutoff frequency of 1kHz and then by a second amplifier 307 to extract the signal waveform.

[0053] In some embodiments, the synchronous acquisition unit 304 uses a multi-channel synchronous acquisition card (sampling rate: DC channel greater than 1kS / s, power frequency channel greater than 10kS / s, high frequency channel greater than 10MS / s) to achieve synchronous time-domain acquisition of three signals through continuous acquisition.

[0054] Example 2:

[0055] This application provides a method for detecting the full-frequency leakage current of DC cables based on multi-sensor fusion, which can be implemented using the detection device described in any of the embodiments in Example 1, such as... Figure 4 As shown, the detection method includes the following steps:

[0056] S10: The fluxgate sensor, the power frequency current transformer, and the high frequency current transformer are connected in series, so that the grounding wire of the DC cable passes through the center of the annular magnetic core of the three sensors in sequence, forming a single series circuit.

[0057] Step S10 is used to install the sensor and connect it in series with the grounding wire. In some embodiments, the specific implementation process of step S10 may be as follows: the grounding wire of the DC cable is passed sequentially through the center 104 of the annular magnetic core of the fluxgate sensor 101, the power frequency current transformer 102, and the high frequency current transformer 103, ensuring that the grounding wire has no branches or parallel paths. The grounding wire is fixed to each sensor by a clamp to ensure that the coaxiality deviation of each sensor core is ≤0.1mm, thereby reducing leakage magnetic interference.

[0058] S20: The leakage current signal in the DC frequency band is collected using the fluxgate sensor, the leakage current signal in the 50Hz to 1kHz frequency band is collected using the power frequency current transformer, and the leakage current signal in the 1kHz to 30MHz frequency band is collected using the high frequency current transformer.

[0059] S30: The leakage current signal, leakage current signal and leakage current signal are respectively processed by low-pass filtering, band-pass filtering and high-pass filtering, and time-domain alignment is achieved through synchronous acquisition unit, and the composite waveform of leakage current in the whole frequency band is generated by superposition.

[0060] In some embodiments, the fluxgate sensor 101 detects the DC leakage current in the grounding wire, and outputs it to the data recording unit after low-pass filtering to extract the DC component, which is the leakage current signal in the DC frequency band. The power frequency current transformer 102 captures AC signals from 50Hz to 1kHz, and separates the power frequency harmonics and operating overcurrent components through band-pass filtering to extract the power frequency component, which is the leakage current signal in the 50Hz to 1kHz frequency band. The high-frequency current transformer 103 acquires high-frequency transient signals from 1kHz to 30MHz, and separates the partial discharge and lightning impulse current components through high-pass filtering and waveform pattern recognition to extract the high-frequency component, which is the leakage current signal in the 1kHz to 30MHz frequency band. The synchronous acquisition unit 304 aligns the time axes of the three signals and superimposes them to generate a composite waveform of the full-frequency leakage current.

[0061] In some embodiments, such as Figure 5 As shown, another flowchart illustrates a method for detecting full-frequency leakage current in DC cables based on multi-sensor fusion. This detection method can be implemented through the following steps:

[0062] S1, Begin.

[0063] Start the detection system and initialize the sensors, signal processing module, and synchronous acquisition unit.

[0064] S2. Sensor assembly and installation are connected in series with the grounding wire.

[0065] Arrange the fluxgate sensor, power frequency current transformer (CT), and high frequency current transformer (HFCT) in series, so that the grounding wire of the DC cable passes through the center of the three toroidal magnetic cores in sequence; fix the grounding wire with a clamp, calibrate the coaxiality of the magnetic cores to ensure that the deviation is ≤0.1mm, and complete the mechanical connection and electrical circuit construction.

[0066] S3. Frequency division signal acquisition and processing.

[0067] In step 3, the three sensor signals are processed in parallel:

[0068] In the fluxgate sensor channel, a 0-10Hz low-pass filter is applied to the output signal to extract the DC component;

[0069] In the power frequency CT channel, a 50Hz-1kHz bandpass filter is applied to the output signal to extract power frequency harmonics (including transient signals of operating overvoltage);

[0070] The HFCT channel applies a 1kHz-30MHz high-pass filter to the output signal to capture high-frequency pulses (including partial discharge and lightning overvoltage signals).

[0071] S4. Synchronous acquisition and time domain alignment.

[0072] The multi-channel synchronous acquisition unit is started to synchronously acquire three filtered signals at a preset sampling rate, and time-domain waveform alignment is achieved through timestamp calibration; the preset sampling rate is ≥1kS / s for DC channel, ≥10kS / s for power frequency channel, and ≥10MS / s for high frequency channel.

[0073] S5, Data Fusion and Composite Waveform Generation.

[0074] The aligned DC component, power frequency harmonics, and high-frequency pulse signal are superimposed to generate a composite waveform of leakage current covering the entire frequency band from 0Hz to 30MHz.

[0075] S6. Fault Feature Extraction and Diagnosis.

[0076] Characteristic parameters (such as DC offset, harmonic distortion rate, high-frequency pulse amplitude / frequency, etc.) are extracted from the composite waveform and combined with preset fault models (such as partial discharge detection and insulation aging analysis) to diagnose the cable insulation condition.

[0077] S7, End.

[0078] Output a test report (including full-band waveforms, fault type, location results, etc.) to complete a single test process.

[0079] The above embodiments are only used to illustrate this application and are not intended to limit this application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this application. Therefore, all equivalent technical solutions also fall within the scope of this application, and the patent protection scope of this application should be defined by the claims.

Claims

1. A multi-sensor fusion-based full-band detection method for DC cable leakage current, characterized in that, The method comprises the following steps: The magnetic flux gate sensor, the power frequency current transformer and the high frequency current transformer are arranged in series, and the grounding wire of the DC cable passes through the center of the ring-shaped magnetic core of the three sensors in sequence to form a single series loop; The magnetic flux gate sensor is used to collect the leakage current signal in the DC frequency band, the power frequency current transformer is used to collect the leakage current signal in the 50Hz-1kHz frequency band, and the high frequency current transformer is used to collect the leakage current signal in the 1kHz-30MHz frequency band; The leakage current signals in the DC frequency band, the 50Hz-1kHz frequency band and the 1kHz-30MHz frequency band are respectively subjected to low-pass filtering, band-pass filtering and high-pass filtering, and time domain alignment is realized through a synchronous acquisition unit to generate a composite waveform of the leakage current in the full frequency band.

2. The detection method according to claim 1, characterized in that, An electromagnetic shielding layer is arranged between the magnetic flux gate sensor and the power frequency current transformer, and an isolation layer is arranged between the high frequency current transformer and the power frequency current transformer.

3. The method of claim 1, wherein, The signal output by the magnetic flux gate sensor is subjected to low-pass filtering with a cutoff frequency of 10Hz and amplification processing to extract the DC component; the signal output by the power frequency current transformer is subjected to band-pass filtering with a frequency band of 50Hz-1kHz and amplification processing to extract the power frequency harmonic and operating overvoltage transient signal; and the signal output by the high frequency current transformer is subjected to high-pass filtering with a cutoff frequency of 1kHz and amplification processing to extract the partial discharge signal and lightning overvoltage transient signal.

4. The method of claim 1, wherein, The synchronous acquisition unit adopts a multi-channel synchronous acquisition card, wherein the sampling rate of the DC channel is greater than 1kS / s, the sampling rate of the power frequency channel is greater than 10kS / s, and the sampling rate of the high frequency channel is greater than 10MS / s, so as to realize synchronous time domain acquisition of the three signals.

5. The method of claim 1, wherein, When the grounding wire passes through the center of the ring-shaped magnetic core of the three sensors, the clamps are used for fixation to ensure that the coaxiality deviation of the magnetic cores of the sensors is less than or equal to 0.1mm.

6. A multi-sensor fusion based full-band detection device for DC cable leakage current, characterized in that, The method comprises the following steps: A sensor group comprising a magnetic flux gate sensor, a power frequency current transformer and a high frequency current transformer arranged in series, the center of the ring-shaped magnetic core of the magnetic flux gate sensor, the power frequency current transformer and the high frequency current transformer being used for passing the grounding wire of a DC cable; An electromagnetic compatibility optimization unit comprising an electromagnetic shielding layer arranged between the magnetic flux gate sensor and the power frequency current transformer, and an isolation layer arranged between the high frequency current transformer and the power frequency current transformer; A signal processing module comprising a low-pass filter circuit, a band-pass filter circuit and a high-pass filter circuit respectively connected to the magnetic flux gate sensor, the power frequency current transformer and the high frequency current transformer, and a synchronous acquisition unit used for realizing time domain alignment of the three signals.

7. The detection device of claim 6, wherein, The magnetic flux gate sensor is installed at the first end of the grounding wire and used for detecting the DC component; The power frequency current transformer is arranged downstream of the magnetic flux gate sensor, adopts a ring-shaped ferrite magnetic core, covers a frequency band of 50Hz-1kHz, and is used for extracting the power frequency harmonic and operating overvoltage transient signal; The high frequency current transformer is installed at the end of the grounding wire, covers a frequency band of 1kHz-30MHz, and is used for extracting the partial discharge signal and lightning overvoltage transient signal.

8. The detection device of claim 6, wherein, The cutoff frequency of the low-pass filter circuit is 10Hz. The cutoff frequency of the band-pass filter circuit is 50Hz to 1kHz; The cutoff frequency of the high-pass filter circuit is 1kHz.

9. The detection device of claim 6, wherein, The synchronous acquisition unit adopts a multi-channel synchronous acquisition card, wherein the sampling rate of a direct current channel is greater than 1kS / s, the sampling rate of a power frequency channel is greater than 10kS / s, and the sampling rate of a high frequency channel is greater than 10MS / s, so as to realize the synchronous time domain acquisition of three signals; wherein the direct current channel is a channel connected between the multi-channel synchronous acquisition card and the fluxgate sensor, the power frequency channel is a channel connected between the multi-channel synchronous acquisition card and the power frequency current transformer, and the high frequency channel is a channel connected between the multi-channel synchronous acquisition card and the high frequency current transformer.

10. The detection device of claim 6, wherein, When the grounding wire passes through the center of the annular magnetic core of the three sensors, the clamps are used for fixation, so as to ensure that the coaxiality deviation of the magnetic cores of the sensors is less than or equal to 0.1mm.

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