384 results about "Ground current" patented technology

The invention relates to the field of cable monitoring, in particular to a high-voltage cable running state comprehensive monitoring method based on a TMR magnetic sensor. According to the method, firstly, a TMR magnetic sensor is adopted to collect sheath current and partial discharge pulse signals of a cable joint grounding wire, then amplification, filtering and AD change are carried out, Fourier transform is carried out, and low-frequency signals and high-frequency signals are separated out; carrying out frequency spectrum analysis on the high-frequency signal, preliminarily judging whether a discharge defect exists or not, carrying out Fourier inversion on the low-frequency signal, evaluating a grounding state and an insulation health state of a cable sheath, carrying out Fourier inversion on the high-frequency signal, and carrying out partial discharge fault type analysis in combination with a time domain partial discharge pulse signal and a power frequency current phase; and finally, comprehensively evaluating the operation state of the high-voltage cable by analyzing the grounding current of the sheath and the related parameters of partial discharge. According to the invention, the hardware cost is reduced, the system design and installation complexity is simplified, and the accuracy of partial discharge fault type identification is improved.

The invention discloses a synchronous monitoring and early warning method for substation ground current micro-power consumption, and relates to the technical field of substation monitoring, and the method comprises the steps: obtaining a ground current data set; performing dynamic time warping on the ground current data set to obtain a time sequence synchronization data set; performing time sequence analysis based on the time sequence synchronization data set, and determining a plurality of ground current characteristics; traversing the time sequence synchronization data set to carry out current fluctuation learning, and generating a ground current prediction data set; and dynamically monitoring the grounding network of the transformer substation, and generating a plurality of feedback response signals to intelligently trigger the alarm of the transformer substation. The technical problems that in the prior art, ground current data of multiple ground points cannot be collected in real time, real-time abnormal fluctuation cannot be accurately captured, potential risks of ground current cannot be effectively recognized in advance, and the early warning instantaneity and accuracy are insufficient are solved, low-power-consumption continuous monitoring of the ground current is achieved, and the early warning efficiency is improved. The technical effect of improving the real-time performance and accuracy of monitoring and early warning is achieved.

The present invention discloses a transformer fault diagnosis technology based on knowledge mapping, which relates to the field of fault diagnosis technology and includes the following steps: S1, obtaining transformer multimodal data and performing data preprocessing; S2, establishing a memory-enhanced early warning model to predict transformer operation data; S3, transformer fault diagnosis. The present invention comprehensively considers online monitoring data or offline test data such as transformer oil dissolved gas data, oil temperature, partial discharge signal, core or clamp grounding current, DC current, infrared spectrum, winding deformation curve, ambient temperature and humidity, etc., performs fault diagnosis on the predicted multimodal data, and predicts possible future transformer faults.

The invention discloses a shielding layer current-based medium voltage cable early fault identification method. The method comprises the following steps of S1, obtaining monitoring data of a tail end shielding layer grounding current; s2, calculating an effective value and an instantaneous value of the grounding current of the tail end shielding layer; s3, whether fault early warning is triggered or not is detected, and if yes, a fault waveform is obtained; s4, calculating the fault duration and the number of fault continuous sampling points, and judging whether the fault is an early fault or not; s5, judging whether the early fault section is a fault downstream section or a non-trunk fault section; s6, calculating a cross correlation function of the tail end shielding layer current and the zero sequence current; and S7, distinguishing a fault section and a fault upstream section according to the optimal delay. According to the invention, the accuracy and efficiency of early fault identification of the medium-voltage cable are improved, and the transformation of protection from post protection to pre-warning is promoted.

The provided are a method, system, and medium for active arc-extinguishing voltage-current conversion in distribution networks. The method includes: detecting a single-phase-to-ground fault in the distribution network and identifying the target faulty phase; injecting compensating currents into the target faulty phase to reduce its voltage; measuring the residual current at the fault point during the injection of compensating currents and the zero-sequence voltage of the target faulty phase; determining a critical zero-sequence voltage threshold based on the residual current at the fault point and assessing whether this critical value exceeds the present zero-sequence voltage; if so, ceasing the injection of compensating currents into the target faulty phase and instead injecting active arc-extinguishing currents at the neutral point of the distribution network to mitigate ground currents at the grounding points of the distribution network. The objective is to enhance the applicability of arc-extinguishing methods for ground faults in distribution networks.

The invention relates to a power cable insulation state real-time monitoring and alarm device, and belongs to the technical field of power equipment state monitoring. Comprising a multi-source sensing unit which is installed at a cable body and a joint; the edge computing terminal is fixed in the cable well or the ring main unit; and the cloud early warning platform receives the processing data and outputs an alarm instruction. According to the invention, multi-parameter deep fusion is realized, four-dimensional monitoring of grounding current, temperature, partial discharge and humidity is initiated for the first time, and limitation of a single parameter is broken through; and an insulation health index IHI is proposed, and the insulation deterioration degree is quantitatively evaluated. According to the method, tan delta and IHI are calculated on site through an edge-cloud collaborative architecture edge terminal, so that the data transmission quantity is reduced; the cloud dynamic threshold value is adjusted, and the alarm accuracy is improved. According to the invention, intelligent early warning mechanism three-level alarm linkage protection equipment is arranged; and the self-calibration function ensures long-term reliability.

The invention discloses a power distribution network grounding fault research and judgment analysis method, relates to the technical field of power distribution network fault analysis, and solves the technical problem that fault analysis is not accurate and deep enough due to the fact that fault features in a neutral point grounding complex fault scene cannot be comprehensively considered. According to the method, single-phase grounding fault models of a neutral point ungrounded system, an arc suppression coil grounded system and a small resistor grounded system are respectively constructed, grounding current, phase voltage and neutral point voltage expressions under the models are detailedly deduced, and characteristics of voltage and current before and after a fault point in the steady-state and transient-state processes are deeply analyzed; the method comprehensively considers various complex fault scenes, can more accurately grasp essential characteristics of faults in different grounding modes, and provides a more comprehensive and accurate basis for fault diagnosis and processing.

The invention discloses a power transmission line tower grounding resistance measuring method and system, and relates to the technical field of high-voltage power transmission, and the measuring method comprises the following steps: transmitting a first electric signal to a coupling injection module, and enabling the coupling injection module to synchronously inject a same second electric signal to two lightning conductors of a power transmission line tower; acquiring voltage signals and current signals at the second electric signal injection positions of the two lightning conductors; and calculating the grounding resistance of the power transmission line tower according to the collected voltage signal and current signal. The same second electric signal is synchronously injected to the two lightning conductors through the coupling injection module, and the ring current between the two lightning conductors is greatly weakened, so that the ground current component can be better extracted, the ground resistance value can be quickly and accurately obtained, the measurement efficiency is improved, errors caused by manual operation are reduced, and the measurement accuracy is improved. The measurement mode does not need to insert an auxiliary grounding electrode and lay a long-distance lead, and is convenient to operate and wide in application range.

The invention discloses a multi-point grounding current limiting device, and relates to the technical field of power transmission line construction, the multi-point grounding current limiting device comprises a placement frame and further comprises a protection assembly, a grounding rod is fixedly installed at the bottom of the placement frame, a placement plate is fixedly installed on the inner wall of the placement frame, and a placement rod is fixedly installed at the top of the placement plate; lifting equipment is arranged on the circumferential surface of the placement rod, a signal receiver is fixedly mounted at the top of the lifting equipment, a current limiting assembly is arranged at the top of the placement plate, a fusing assembly is arranged at the top of the placement plate, a grounding connecting wire is arranged between the fusing assembly and the current limiting assembly, and a limiting frame is fixedly mounted at the top of the placement plate. According to the grounding current limiting device, the L-shaped plate moves downwards to drive the limiting plate to move downwards, the limiting plate moves downwards to make contact with the grounding connecting wire and extrude and fix the grounding connecting wire, the optimal state of the grounding connecting wire can be kept by avoiding bending or pulling, low grounding resistance is ensured, and therefore the efficiency and safety of the grounding current limiting device are improved.

The invention discloses a high-voltage cable grounding current abnormity monitoring system, which belongs to the technical field of electric power facilities and comprises an inspection acquisition module, an association analysis module, a collaborative reasoning module and a self-optimization module. The inspection acquisition module is used for synchronously acquiring multi-source monitoring parameters and acquiring position information so as to generate a grounding parameter matrix; the association analysis module is used for screening suspected defect types, dividing a local overheating area, performing overheating cause judgment, constructing a coupling association matrix of a multi-physical field, performing evolution stage judgment in combination with historical data, and generating a preliminary mechanism hypothesis in combination with credibility rating; the collaborative reasoning module is used for constructing a dynamic knowledge graph and a constraint prediction network, constructing a collaborative reasoning mechanism based on a two-way real-time interaction channel, performing preliminary reasoning, and dividing early warning levels in combination with comprehensive confidence so as to perform operation and maintenance feedback; and the self-optimization module is used for carrying out directional iteration on the double engines by utilizing manual feedback and carrying out cross-line migration optimization according to different lines.

The invention provides an on-line monitoring system and method for the grounding current of a transformer iron core, and belongs to the field of data processing, and the system comprises a magnetic adsorption type dual-channel current sensor which is used for synchronously collecting a transformer iron core grounding current channel signal and a transformer clamp grounding current channel signal; the self-adaptive signal preprocessing module is used for carrying out self-adaptive differential processing through a self-adaptive differential coefficient and carrying out variable gain adjustment and self-adaptive filtering; the multi-dimensional feature extraction module is used for performing multi-dimensional signal feature extraction on the purified grounding current signal to obtain a multi-dimensional feature parameter set; the feature fusion module is used for performing constraint fusion on the multi-dimensional feature parameter set based on the corrected iron core eddy current loss physical model, and generating a comprehensive health evaluation index through an adaptive weight adjustment mechanism; and the intelligent diagnosis module is used for carrying out transformer iron core fault type identification, health state evaluation and trend prediction according to the comprehensive health evaluation index and the multi-dimensional characteristic parameter set to obtain a transformer iron core state monitoring result.

The invention provides a power converter. A direct-current arc detection device arranged in the power converter comprises a first current induction device, a second current induction device and a controller. The first current sensing device is used for sensing the current change of the positive cable and outputting a first voltage signal, the second current sensing device is used for sensing the current change of the negative cable and outputting a second voltage signal, and the controller is used for adjusting the gain ratio between the first voltage signal and the second voltage signal. Therefore, the gain ratio of positive and negative cable sampling signals can be independently adjusted according to the asymmetric working condition of positive and negative cable loops, so that the optimal differential mode signal suppression effect is achieved, the interference of alternating current to ground current on direct current arc detection is reduced to the greatest extent, and the false alarm probability of direct current arc detection is reduced.

A method and apparatus for monitoring the current of grounding wires of armored and shielded cables in a strong electromagnetic environment. In the method, the sum current of armor layer grounding wires of M cables in a terminal box and the sum current of shield layer grounding wires are respectively collected, primary and secondary grounding copper bar potentials of the terminal box and the grounding current of an adjacent terminal box are collected; a potential difference alarm can be implemented; and on the basis of whether the potential difference alarm is implemented, different criteria are used to respectively implement an alarm for the circulating current of a cable loop in the terminal box.

The invention discloses a comprehensive monitoring and early warning method and system for a transformer, and relates to the field of transformer monitoring, and the method comprises the steps: collecting the state data of a target transformer in real time, the state data comprising oil chromatography data, a partial discharge signal, a grounding current, local temperature data and a local vibration signal; the current state data is preprocessed; performing multi-angle evaluation on the state of the target transformer according to the preprocessed current state data; if the state of the target transformer obtained through evaluation from at least one angle is abnormal, performing early warning on each abnormal state of the target transformer; accurate monitoring and early warning of the state of the target transformer are achieved, and the problems that an existing transformer monitoring method is low in monitoring precision and insufficient in fault early warning capacity are solved.

The invention relates to a ring main unit intelligent detection and fault early warning method and system. The method comprises the following steps: deploying an ultrahigh frequency sensor, an infrared thermal imager, an ultraviolet sensor and a high-frequency current transformer, and synchronously acquiring multi-modal data such as partial discharge, temperature distribution, corona discharge and grounding current of the ring main unit; carrying out feature extraction on the collected data, wherein the feature extraction comprises a time-frequency statistical feature and a temperature-load correlation feature of the partial discharge signal; the Dempster-Shafer evidence theory is utilized to carry out fusion calculation on the multi-source feature evidence, and confidence coefficients for insulation degradation, poor contact, arc faults and other fault types are obtained; arc fault prediction is carried out in combination with a long-short-term memory network model; and finally executing a grading early warning strategy according to the fault confidence. The problems of low detection reliability and fault early warning lag of a single sensor are solved, early accurate diagnosis and predictive maintenance of the insulation fault of the ring main unit are realized, and the operation safety and reliability of power equipment are remarkably improved.

The utility model discloses a grounding detection device for an auxiliary circuit of a railway locomotive. The grounding detection device comprises a plurality of loads, an A / D converter, a judging device and a plurality of current detectors, the input end of each current detector is connected with the shell of the corresponding load and is used for acquiring the grounding current leaked from the shell of the load; the input end of the A / D converter is connected with the output end of the current detector, and the A / D converter is used for converting the grounding current into a digital signal from an electric signal; the judger is connected with the output end of the A / D converter and comprises comparators in one-to-one correspondence with the A / D converter, each comparator is internally provided with a threshold value, the comparators are all compared with the corresponding digital signals, when the input digital signals are not larger than the threshold values, the comparators output first signals, and when the input digital signals are larger than the threshold values, the comparators output second signals. And the comparator outputs a second signal so as to simplify the process of ground fault detection and improve the easiness of load detection.

The invention provides a defected ground-based broadband high-isolation MIMO (Multiple Input Multiple Output) mobile phone antenna. Each face-to-face inverted-F antenna pair is connected with an inverted-L branch knot; lumped capacitors are arranged at the joints of the radiation arms and the vertical lines where the feeding points are located; 2N linear slots are formed in the feeding points of the N dual-port antenna pairs on the edge of the metal ground; a T-shaped gap is formed in the middle position of the two antennas of each dual-port antenna pair; an antenna pair gap is formed between the two dual-port antenna pairs on the same side; the feed branch knot is printed in the linear slot, and the tail end of the feed branch knot is provided with a lumped capacitor. According to the invention, the distribution of floor current is changed through the T-shaped gap, and the decoupling characteristic of the MIMO mobile phone antenna is realized. By loading the inverted L branches on the inverted F antenna, introducing the coplanar waveguide structure and loading the lumped capacitor, the working bandwidth of the MIMO mobile phone antenna is effectively widened.

The invention provides a fault isolation and restart method and system for a multi-terminal flexible DC power transmission system, and relates to the technical field of flexible DC power transmission. The fault isolation and restart method comprises the steps of determining a station grounding current first effective value of each converter in the multi-terminal direct current power transmission system under the condition that a single-phase grounding fault exists on a valve side or a bridge arm side of the multi-terminal direct current power transmission system; according to the first effective value of the station grounding current and the second effective value of the station grounding current of each current converter, determining a faulty current converter; the current converter with the fault is isolated; and unlocking a fault-free converter in the multi-terminal direct current power transmission system, and increasing the power of the fault-free converter to a set value. According to the method and the system, the problem of simultaneous locking of the whole multi-end flexible direct current power transmission system caused by single-phase grounding fault of a single converter valve side or a bridge arm side of the multi-end flexible direct current power transmission system can be solved, and the operation reliability of the multi-end flexible direct current power transmission system is improved.

The invention relates to the technical field of high-voltage direct-current power transmission, and discloses a grounding device in a converter station, which comprises a power conversion cabinet and an adjusting mechanism, the front surface of the power conversion cabinet is rotatably connected with a cabinet door through a hinge, a supporting mechanism is arranged in the power conversion cabinet, and the supporting mechanism comprises a supporting frame fixedly connected with the inner wall of the power conversion cabinet. A first groove is formed in the inner wall of the supporting frame, a first mounting rod is slidably connected to the inner wall of the first groove, a first through hole is formed in the outer surface of the first mounting rod, and a metal rail is fixedly connected to the inner wall of the first mounting rod; in the converter cabinet equipment, vibration generated by operation of electric equipment can be transmitted to the connecting shaft through the force block, the elastic guide piece can absorb the vibration on the connecting shaft, and meanwhile, due to the fact that the elastic guide piece is in sliding connection with the metal rail, grounding current can be further guided to the supporting frame through the metal rail along the connecting channel. And the grounding stability of the electric equipment is improved.

The invention belongs to the technical field of power protection, and particularly relates to a station transformer grounding current synchronous synthesis method and system, and the method comprises the steps: carrying out the grouping according to the number of a station transformer, synchronously collecting the grounding branch current of each station transformer to obtain an original signal, carrying out the double identification, and carrying out the homologous copying; generating two paths of independent signals of frequency detection and phase calibration; frequency detection signals are grouped according to double identifications, the independent actual frequency of each station transformer is obtained after frequency detection processing, and a same-frequency sine dynamic reference signal is generated based on the independent actual frequency; performing phase alignment and compensation on the phase calibration signal and the corresponding reference signal according to the double identifiers to obtain a calibrated signal; according to the method, the phase calibration reference of each station transformer is completely matched with the actual frequency of the station transformer, the reason of phase reference dislocation caused by frequency fluctuation is eliminated from the source, and the accuracy of synthesizing the total grounding current in the station is improved.

A method and insulation monitoring arrangement for insulation monitoring of an electric installation operated using a supply direct voltage and has a first insulation resistance between the positive active conductor and ground and a second insulation resistance between the negative active conductor and ground as well as a functional grounding between the negative active conductor and ground by a ground resistance. The method involves measuring a ground current, which flows in the path of the functional grounding, by means of a DC measuring device; measuring the supply direct voltage by means of a voltage measuring device; computing the first insulation resistance from the supply direct voltage divided by the ground current by means of a computing unit; the condition is valid during operation of the electric installation that the second insulation resistance being at least 100 times greater than the ground resistance.

The invention relates to the field of power system equipment detection, in particular to a residual magnetism measuring device and method for a large power transformer. The residual magnetism measuring device for the large-scale power transformer comprises the large-scale power transformer, a high-voltage bushing, a high-voltage neutral point bushing, a low-voltage bushing, an iron core outgoing line bushing, a first capacitor, a second capacitor, a detection impedor, a partial discharge instrument and a large-current generator, the capacitance of the first capacitor is 30pf-40pf and is matched with the capacitance of a transformer iron core, and the capacitance of the second capacitor is 300pf-400pf and is 10 times proportional to the capacitance of the first capacitor; the method comprises the following steps: carrying out a long-time induction withstand voltage and partial discharge test after a conventional test, measuring discharge amounts Q1, Q2 and Q3 at 0.5, 1 and 1.5 times of rated voltages, judging residual magnetism according to the difference value of the discharge amounts and an iron core grounding current, and if the residual magnetism exceeds the standard, magnetizing and demagnetizing by using a large current generator at the frequency of 150Hz. The method has the advantages that the residual magnetism is measured and evaluated in time, equipment faults are avoided, operation is easy and convenient, and adaptability is high.

The invention relates to the technical field of wind driven generators, in particular to a system for reducing generator shaft current damage and a working method.The system is characterized in that a generator spindle is connected with a generator shell through at least one insulating bearing, and at least one grounding ring is further arranged on the generator spindle; the grounding ring is grounded through a carbon brush and a grounding wire which are connected in sequence; the grounding wire is provided with a current transformer, and the current transformer is used for obtaining grounding current data and transmitting the grounding current data to the data processing end. And the data processing end is used for predicting working state data of the insulating bearing based on the grounding current data, the data of the environment where the fan is located, the fan operation data and the insulating bearing data, and evaluating whether a shaft current risk alarm is sent or not based on the working state data of the insulating bearing. By monitoring and evaluating the working state of the insulating bearing of the system, operation and maintenance personnel can master the working state of the insulating material of the insulating bearing at any time, and the situation that equipment is damaged by shaft current due to failure of the insulating material is avoided.

The invention relates to a double-sheath loop interphase short circuit defect detection method based on adjacent sheath current phasor difference, and the method comprises the following specific steps: 1, constructing a circuit network model of a high-voltage cable, and recognizing different types of grounding fault mechanisms; 2, performing simulation to obtain sheath grounding current data, and performing feature extraction on the sheath grounding current data to obtain the amplitude and the phase of the current; step 3, training and testing the extracted current features by adopting a proper machine learning algorithm, and improving the accuracy of fault detection by constructing a classification model; and 4, classifying the newly collected current data by using the trained model, and judging the fault category, thereby taking corresponding maintenance measures in time, and ensuring the safe and stable operation of the cable. The accuracy of fault detection is improved by constructing the classification model, and the efficiency of sheath interphase short circuit maintenance at the present stage is improved.

The invention discloses a cable dielectric loss monitoring method and system based on leakage current separation, and the method comprises the steps: collecting the grounding current and phase current of three phases of a cable, and collecting the space voltage of an intermediate phase; calculating lead angles of the grounding current and the phase current based on the grounding current, the phase current and the space voltage; in any period, separation of induced current is carried out based on the lead angles of the grounding current and the phase current at two different moments, and the phase angle of the leakage current is determined; and calculating a dielectric loss angle tangent value of each phase based on the phase angle of the leakage current. According to the method, the dielectric loss of the cable can be monitored in real time under the condition of normal operation of the cable, and the dielectric loss angle tangent value of the cable can be obtained more accurately by separating the induced current from the leakage current and calculating the phase difference between the leakage current and the space voltage, so that the aging state of the cable can be evaluated more accurately, and the service life of the cable is prolonged. And the safety and the reliability of the power system are improved.

The invention discloses a method and a system for diagnosing defects of a sheath grounding system under resonance voltage resistance of a power transmission cable. The method comprises the following steps: installing a sheath grounding current acquisition system; sequentially carrying out main insulation resonance voltage withstanding tests on three phases of the power transmission cable, and synchronously recording a grounding current waveform of a metal sheath by adopting a current acquisition system when each phase is subjected to voltage withstanding; processing the grounding current waveform by adopting a signal processing algorithm, and extracting a resonance component; and constructing a defect diagnosis matrix according to the resonance component, calculating a deviation between the defect diagnosis matrix and a standard matrix as a defect characterization value of the cable sheath grounding system, and obtaining a defect diagnosis conclusion of the sheath grounding system under the resonance withstand voltage of the power transmission cable. According to the method, the grounding current waveform of the metal sheath is synchronously acquired and analyzed in the main insulation resonance voltage withstand test of the three-phase cable, the resonance component is extracted, accurate identification of the defect is realized based on deviation calculation of the defect diagnosis matrix, and the detection sensitivity and the diagnosis reliability of the latent defect of the sheath grounding system before the cable is put into operation are improved.

The invention relates to a three-dimensional multi-source stray current interference characteristic analysis and identification method based on wavelet analysis. When a buried pipeline is subjected to electrical interference of different interference sources (such as high-voltage transmission line current, high-voltage direct-current grounding electrode grounding current, electrified railway and high-speed railway current, urban rail transit current and natural environment such as tidal interference current), the buried pipeline is subjected to electrical interference. And identifying and analyzing the pipe-to-ground potential and alternating current voltage fluctuation characteristics (amplitude characteristics and frequency characteristics) under stray current interference, judging the influence of interference sources on the safety and stability of the buried steel pipeline, solving the problems of analysis, identification and processing of multiple interference sources in the existing complex environment, improving the monitoring and treatment level of the interference sources of the buried steel pipeline, and improving the safety and reliability of the buried steel pipeline. Safe and reliable operation of the pipeline is ensured.

The invention discloses a cable fault monitoring and early warning method and system, and relates to the technical field of fault monitoring. The method comprises the steps that cable operation state parameters and environment parameters are collected in real time through a distributed sensor array, and the cable operation state parameters comprise cable temperature, three-phase current, partial discharge signals, insulation resistance, grounding current and mechanical vibration amplitude; the environment parameters at least comprise temperature and humidity corresponding to a cable laying environment; preprocessing the cable operation state parameters and the environment parameters, and generating a standardized feature matrix based on preprocessed multi-source data; inputting the standardized feature matrix into a pre-trained fault prediction model for processing to obtain a fault type and a fault risk index corresponding to the current operation state of the cable; and triggering an early warning mechanism according to the fault type and the fault risk index, and outputting corresponding fault position information.

The invention discloses a component separation calculation method, system and device for grounding current of a high-voltage alternating-current submarine cable and a medium. The component separation calculation method comprises the steps that current transformers are additionally arranged on submarine cable bodies at the head end and the tail end of an on-site high-voltage alternating-current submarine cable, a metal sheath grounding wire and an armored grounding wire; acquiring the current monitoring quantity flowing through the current transformer; performing vector calculation on the current monitoring quantity to obtain submarine cable core current vectors, metal sheath grounding current vectors and armor layer grounding current vectors at the head end and the tail end; vector calculation is carried out on the current vectors to obtain capacitance current components and electromagnetic induction current components of metal sheath grounding current and armoring grounding current, and the capacitance current leakage proportionality coefficient of the metal sheath and the armoring and the electromagnetic induction current proportionality coefficient of a grounding loop are calculated by further combining the submarine cable core current vectors; therefore, the grounding loop state of the metal sheath and the whole armored wire of the submarine cable and the main insulation and sheath external insulation state of the submarine cable are monitored.

The invention discloses a SiC MOSFET dual protection circuit based on di / dt detection, and the circuit comprises a current sampling module, the input end of the current sampling module is connected with the two ends of a parasitic inductor LSs, the auxiliary source electrode of a SiC MOSFET is grounded, the output end of the current sampling module is connected with the input end of a short-circuit fault judgment module and the input end of an overload fault judgment module, and the output end of the short-circuit fault judgment module is connected with the input end of the overload fault judgment module. The output end of the short circuit fault judgment module and the output end of the overload fault judgment module are connected with the input end of the fault signal latch module, the output end of the fault signal latch module is connected with the input end of the output stage and soft turn-off module, and the output end of the output stage and soft turn-off module is connected with the grid electrode of the SiC MOSFET. According to the SiC MOSFET dual protection circuit based on di / dt detection, reliable protection of hard switching faults, load short-circuit faults and overload faults of devices can be realized by using a single detection circuit, and the drive protection circuit has a soft turn-off function, so that the drive protection circuit is more comprehensive and effective, the service life of power devices is prolonged, and the reliability of a system is improved.