603 results about "Earthing system" patented technology

The invention provides a multi-dimensional electrical equipment insulation analysis and evaluation method, and relates to the technical field of electrical equipment insulation online detection and intelligent diagnosis. According to the method, an electrically isolated direct current detection channel is constructed in a neutral point small resistance grounding system, controllable direct current detection signals are injected, micro direct current leakage response signals are collected, and after zero drift correction, temperature compensation and power frequency ripple suppression are carried out, layered attribution is carried out in combination with primary system topology and an equipment ledger, and a multi-dimensional response matrix is formed. According to the method, environment and working condition normalization is realized through factor rejection and robust pull-back, a mechanism model containing leakage channel equivalent parameters and path constraints is established, multi-working-condition data is fused to calculate equivalent insulation parameters and credibility indication quantity, and a multi-dimensional insulation representation vector is generated. And performing time sequence analysis on the representation vector, extracting degradation and abrupt change characteristics, outputting a health index and a risk level, and realizing quantitative evaluation and intelligent early warning of the insulation state.

The invention particularly relates to a discharge machining simulation control system for a nuclear power plant in a high-radiation boron-containing water environment, which belongs to the technical field of special maintenance in the high-radiation environment of the nuclear power plant and comprises a man-machine interaction system, a discharge machining control system and subsystems. Each subsystem comprises a pulse power supply system, a servo power system, a washing system, a purification system, a grounding system and a tool system; the man-machine interaction system is used for man-machine interaction and displaying the discharge machining implementation data fed back by the subsystems; the electric discharge machining control system is used for generating an electric discharge machining instruction according to the man-machine interaction information and controlling the subsystems to cooperate to perform electric discharge machining work; and each subsystem is used for implementing electric discharge machining work according to the electric discharge machining instruction and feeding back electric discharge machining implementation data. According to the invention, simulation control of discharge processing in the high-radiation boron-containing water environment of the nuclear power plant is realized.

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 belongs to the field of single-phase earth fault line selection, and provides a small-current grounding system single-phase earth fault line selection method and system. The method comprises the following steps: acquiring fault current information of a small current grounding system; extracting fault features in the fault current information; the fault characteristics at least comprise a zero-sequence current amplitude, a zero-sequence current phase angle, a fifth harmonic current amplitude, a fifth harmonic current phase angle and a transient zero-sequence current amplitude; the extracted fault features are parallelly and correspondingly input to a first neural network model, and single-phase earth fault line selection initial results corresponding to the fault features are obtained; the number of parallel fault classifiers contained in the first neural network model is the same as the number of fault features; and inputting all the initial line selection results into the second neural network model to obtain a final single-phase earth fault line selection result.

The invention discloses a method for carrying out zero sequence loop impedance calculation by using a frequency conversion signal, the calculation method is applied to a power distribution network arc suppression coil grounding system, and the power distribution network arc suppression coil grounding system comprises a control device, a grounding transformer, an injection transformer and a variable signal source; according to the method, the signal source is adopted to inject signals with different frequencies to calculate the capacitive current, the impedance parameter of the arc suppression coil and the capacitive current of the system during parallel operation are calculated by establishing a loop equation according to different system zero sequence loop impedances under different frequencies, and then the capacitive current needing to be compensated by the system is accurately calculated. The method solves the problems of the calculation of the capacitance current of the system and the automatic tracking of the arc suppression coil during the parallel operation of the two machines, is not affected by the unbalance of the system, and provides a reliable basis for the precise control of the parallel operation of the two machines of the arc suppression coil.

The invention provides a grounding system of a long-wave transmitting antenna, and relates to the technical field of grounding systems. The system comprises a top wire ground screen, a high-voltage feeder ground screen, a tuning pavilion ground screen, an iron tower ground screen, a grounding well and a ground screen outer edge bus bar, the loss resistance of a high-voltage and high-intensity magnetic field in a grounding system is reduced aiming at the problem of the density of current borne by a top line, a high-voltage feeder line and a tuning booth, so that the grounding loss resistance is reduced to a great extent. In addition, aiming at the problem of large current density of the tuning booth, the ground net of the tuning booth is arranged by utilizing a plurality of dense and radially laid wires, so that the loss of the ground net is improved. The problem that grounding loss resistance is large due to the fact that a grounding system is designed through a large-scale dense ground net at present is solved.

A dynamo-electric rotary machine includes a rotor defining an axis, a stator, and a can designed for arrangement in an air gap between the rotor and the stator in order to seal the stator and the rotor in relation to each other. The can has at least one section of average electrical conductivity in a range from 1 S / m to 10000 S / m in an axial and / or a tangential direction. The can is electrically conductively incorporated in an earthing system of the dynamo-electric machine.

A method and system for measuring distribution network system parameters based on harmonic injection, for use in a low-current grounding system containing an arc suppression coil. The system injects currents of multiple frequencies into the neutral point of the low-current grounding system through an injection source and measures the neutral point voltage. The system uses formulas to calculate and obtain the line capacitance, arc suppression coil inductance, and damping resistance parameter values ​​in the distribution network system. This application can accurately measure line capacitance, arc suppression coil damping resistance, and reactance by injecting only two frequencies of current. This method has little impact on grid operation, high measurement accuracy, and broad application prospects.

The invention discloses a grounding fault judgment method and system of a distribution line grounding system, a storage medium, electronic equipment and a computer program product. According to the ground fault judgment method, the ground fault judgment system determines a zero-sequence voltage abrupt change value and a zero-sequence voltage amplitude according to the collected zero-sequence voltage of the distribution line; under the condition that the zero-sequence voltage abrupt change value meets a preset zero-sequence voltage abrupt change value condition, determining a transient grounding judgment result and a zero-sequence admittance value according to the collected zero-sequence current and zero-sequence voltage of the distribution line; determining the classification condition of the zero-sequence admittance value according to the transient grounding judgment result; under the condition that the zero-sequence voltage amplitude meets a preset zero-sequence voltage amplitude condition, determining a zero-sequence admittance judgment result according to the classification condition of the zero-sequence admittance value and the zero-sequence admittance value; determining a grounding comprehensive result according to the transient grounding judgment result and the zero-sequence admittance judgment result; and determining a grounding fault condition of the distribution line according to the grounding comprehensive result and a preset grounding result condition.

The invention discloses a construction method of an earth system coupling device and the earth system coupling device, and the construction method comprises the steps: a first component module construction step: constructing a plurality of first component modules of a global climate system based on full coupling, the plurality of first component modules comprise an atmospheric component module, a land component module, a sea ice component module, a ground ice component module, a river component module, a first ocean component module and a sea wave component module; a second component module construction step: constructing a second component module based on the ocean circulation simulation system, wherein the second component module is a second ocean component module; a replacement step: replacing the first ocean component module with the second ocean component module; and a coupling step: reconstructing a coupling application interface of the coupler of the global climate system based on full coupling, and carrying out data exchange and interaction among different component modules through the coupling application interface.

The invention discloses a full-power variable-speed pumped storage unit stator winding insulation state online monitoring method, and provides a high-capacity generator unit stator winding insulation state online monitoring method which can be applied to a network side transformer neutral point ungrounded system. According to the method, an effective common-mode monitoring loop can be established, and monitoring is carried out by utilizing the third harmonic of the motor stator winding and is not interfered by the high-frequency switch harmonic of the frequency converter. In order to solve the problem that a full-power variable-speed pumped storage unit generally has large capacity and is not easy to realize online measurement, the invention provides a method for measuring on a neutral point outgoing line, which can realize online measurement of the insulation state of a stator winding when the load current is relatively large. The method is suitable for a full-power variable-speed pumped storage high-capacity unit, leakage current measurement can be carried out under the condition of large load current, and stator insulation information online monitoring is achieved.

The invention discloses a ground resistance comprehensive test system and method, and belongs to the field of ground test, and the ground resistance comprehensive test method comprises the steps: determining a test monitoring area of ground resistance, drawing a power grid distribution three-dimensional model on the test monitoring area, and marking each ground point in the test monitoring area; detecting a grounding resistance value on the grounding point, and evaluating whether the grounding resistance value of the grounding end on the grounding point is abnormal or not; and for the grounding point with the abnormal grounding resistance value, calculating the equivalent grounding resistance value of the grounding point according to the soil parameters on the grounding point, and evaluating whether the grounding system on the grounding point is damaged or not. The test system comprises a grounding resistance tester, a wireless data module, a soil parameter acquisition module and a far-end monitoring center. According to the invention, the grounding resistance of the grounding end is tested by using the multi-frequency alternating-current electric signal, so that the test requirements of different grounding systems under various working conditions can be met, and the universality and the practicability are ensured.

The utility model relates to the technical field of enterprise power grid operation and maintenance, in particular to a rapid isolation protection device for a grounding fault of a power grid neutral point ungrounded system, and aims to solve the problems that when the grounding fault of the power grid neutral point ungrounded system is processed at present, grounding is relieved by generally adopting an arc-extinguishing and resonance-eliminating mode of manually resetting a rapid switch; and a large-area power failure accident is caused by breakdown and short circuit of an insulation weak point of equipment in a system due to too long processing time. According to the device, a fault point is isolated through zero-sequence power direction protection action tripping, closing of the vacuum circuit breaker is converted into metal grounding through action of the quick switch arc-extinguishing and resonance-eliminating circuit, and quick fault isolation is effectively realized through automatic resetting and delay setting functions of the arc-extinguishing and resonance-eliminating circuit. Therefore, the repeated action of the rapid switch arc-extinguishing and resonance-eliminating circuit caused by intermittent arc grounding is avoided, the occurrence rate of large-area power failure accidents caused by arc grounding is greatly reduced, and the safe and stable operation of an enterprise power grid is further ensured.

The invention discloses a GIL grounding device and a design method thereof. The method comprises the following steps: obtaining structure parameters and operation parameters of a gas insulated transmission line; calculating electrical parameter values of the gas insulated transmission line, wherein the electrical parameter values comprise capacitance, inductance and alternating-current resistance values of the gas insulated transmission line; according to experience and engineering practice, the number and positions of grounding points are selected, the grounding resistance value of each grounding point is determined, and a grounding system arrangement scheme is obtained; building an equivalent circuit of the gas insulated transmission line; performing electromagnetic transient simulation on the equivalent circuit, and determining the shell potential of each point on the shell of the gas insulated transmission line when the transmission line has a short-circuit fault; and verifying whether the maximum shell potential is lower than the critical value of the contact voltage, and if the shell potential is higher than the critical value of the contact voltage, performing design optimization of the grounding device. The condition that the potential of the shell is too high due to failure of a single means can be avoided, the reliability of a grounding system is improved, and a guarantee is provided for safe and stable operation of a gas insulated transmission line.

The invention discloses a pile foundation external application device, a grounding pile foundation and a grounding system, the pile foundation external application device is cylindrical and comprises a base body layer, a transition layer and an external coating layer, the transition layer is wrapped by the external coating layer, the base body layer is wrapped by the transition layer, and the resistance of the transition layer is in index attenuation distribution from the resistivity of the base body layer to the resistivity of the external coating layer. Therefore, the substrate layer, the transition layer and the outer coating layer form a gradient conductive structure, the resistivity of the pile foundation external application device is in gradient distribution, the interface potential barrier is effectively inhibited, and the pile foundation grounding resistance is effectively reduced after the pile foundation external application device is externally applied to a grounding pile foundation, so that the grounding resistance of a grounding system is reduced, and the diversion performance of the grounding system is improved.

The invention provides a resonant grounding system high-resistance grounding fault phase selection method based on frequency domain energy change, and belongs to the field of medium-voltage power distribution network fault detection. The invention provides a phase selection method based on frequency domain energy change in order to solve the problems that high-resistance grounding fault phase selection is difficult and power grid parameters are unbalanced in a resonant grounding system. The method comprises the following steps: firstly, acquiring a three-phase voltage signal of a fault line, and filtering the signal through a 4-order Butterworth low-pass filter to eliminate high-frequency noise interference; analyzing frequency domain energy change of the three-phase voltage before and after the fault by using fast Fourier transform, and extracting fault features; and finally, constructing a novel phase selection criterion based on the positive and negative values of the three-phase voltage frequency domain energy change, the frequency domain energy change vector and the projection thereof, and realizing fault phase selection. According to the method, the fault phase and the non-fault phase can be effectively distinguished, the method is particularly suitable for accurate phase selection of the high-resistance grounding fault, and the reliability and the safety of medium-voltage power distribution network fault diagnosis can be remarkably improved.

The invention discloses a submarine cable interlayer fault detection method and system for a submarine cable grounding system, and a medium. The method comprises the following steps: S1, pre-installing a power frequency current sensor, a power frequency voltage sensor and a traveling wave sensor on a sheath layer and an armor layer of landing sections at two sides of the high-voltage alternating-current submarine cable grounding system; the method comprises the following steps: extracting current and voltage signal data of a fault state through a power frequency current sensor, a power frequency voltage sensor and a traveling wave sensor, and carrying out data preprocessing including detection cleaning, data interpolation and data normalization on the current and voltage signal data; according to the method, fault codes are obtained through data collection, preprocessing, feature fusion, training learning and coding reconstruction and classification, and accurate fault detection is carried out on submarine cable interlayer faults through the fault codes.

The invention discloses an open-phase detection method and device suitable for a system with multiple starting standby transformers. The method comprises the following steps: measuring a three-phase current on an incoming line, measuring a neutral point zero sequence voltage of each starting standby transformer, and collecting a neutral point grounding knife switch position of each starting standby transformer; based on the three-phase current on the incoming line, calculating an incoming line positive sequence current and an incoming line zero sequence current by using a symmetric component method; and according to the incoming line zero-sequence current, the neutral point zero-sequence voltage of each starting standby transformer and the position of a neutral point grounding knife switch, judging whether an open-phase fault occurs and positioning a fault interval. The method is suitable for a parallel connection mode of a plurality of starting and standby transformers, is also suitable for a transformer neutral point grounding or non-grounding system, and can effectively identify open-phase faults on a high-voltage side and a line of the starting and standby transformer under no-load and light-load working conditions.

The invention discloses a high-voltage cable defect identification method and system based on cross-connected grounding circulating current, and the method comprises the steps: constructing a sheath circulating current equivalent model of a three-phase cable cross-connected grounding system for a single-core cable model in a cross-connected grounding mode, and calculating a sheath circulating current value; based on a field-circuit coupling model of a multi-physical field, metal sheath loss and cable internal temperature of different types of typical defects are obtained, and a typical defect mode classification table of the cross interconnection system is constructed; establishing an integrated learning model based on a LightGBM algorithm, and training the integrated learning model to obtain a trained integrated learning model; and calculating circulation data of the target high-voltage cable, obtaining a target defect characteristic quantity of the target high-voltage cable, and classifying the target high-voltage cable based on the trained integrated learning model to obtain a defect type of the target high-voltage cable. According to the method, the system circulation calculation precision and the high-voltage cable defect identification precision and accuracy are remarkably improved.

The invention relates to the field of power systems, in particular to a power cable cross interconnection grounding system live-line maintenance method and system. The method comprises the following steps: firstly, synchronously acquiring cable line load current, three-phase grounding ring current and grounding resistance at the head end and the tail end of a metal sheath of a crossed interconnection unit with ring current abnormity, and generating a real-time data set with a timestamp; extracting cable structure parameters based on a preset cable topology database, and dynamically associating the cable structure parameters with the real-time data set; constructing a multi-conductor transmission line equation model, calculating a theoretical circulation distribution value of each section of sheath, and generating a theoretical circulation map; carrying out matching analysis on the theoretical circulation map and actually measured circulation data, and determining defect types and positions; and finally, according to a defect positioning result, the maintenance operation is executed in an electrified state through the insulating mechanical arm, and the stability of the grounding impedance of the system is maintained through the bypass grounding device. The problems that in the prior art, the live detection function is incomplete, and defects cannot be rapidly and accurately positioned are solved.

An enclosure to protect people and instruments from the effects of an electromagnetic pulse (EMP) is provided. The enclosure includes a floor assembly; walls extending upward on a first, second, third, and fourth side of the floor assembly; a roof; and a ceiling. On the interior of the enclosure, a shield layer is provided such that the enclosure forms a six-sided Faraday cage. Fasteners and other conductive securement materials such as copper tape help achieve the conductivity of the shield layer. Extending through the walls of the enclosure may be secure points of entry allowing for people, air, and conductors to securely enter and exit the enclosure. The enclosure contains a grounding system to assist with protecting the contents of the enclosure from the effects of the EMP.

The invention discloses a grounding system of a high-voltage switch cabinet, relates to the technical field of power systems, and solves the problems of poor resistance stability and poor safety in a grounding system of an existing high-voltage switch cabinet. The system comprises a real-time detection module, a self-adaptive grounding resistance adjusting module, a high-frequency transient suppression module, a fault detection and isolation module, a grounding current control module and a remote measurement module. The multi-section controllable resistor is connected with the grounding path in series, the resistance value is automatically adjusted by combining the environment compensation model, it is ensured that the grounding resistor is kept stable under different environment conditions, arc light reignition is detected and rapidly responded through the high-frequency transient suppression module, and generation of overvoltage is effectively suppressed; grounding current is monitored in real time through the fault detection and isolation module, further diffusion of faults is prevented, and reliability and safety of the system are improved; according to the invention, the resistance stability and safety of the existing grounding system are greatly improved.

The invention discloses a task collaborative unloading method and device for a space-air-ground integrated scene and a simulation system, and relates to the technical field of edge computing collaborative unloading. According to the task collaborative unloading method for the space-air-ground integrated scene, unloading of a target task is achieved through two stages; in the first stage, a matched execution end is selected according to task information of a target task; when the execution end is a satellite cluster end, second-stage unloading is carried out, and in the second-stage unloading, the matched execution satellite is selected to execute the target task according to the satellite information of the satellites. According to the method, the effectiveness of task collaborative unloading in a space-air-ground integrated system composed of the user side, the satellite cluster side and the cloud server side is improved.

The invention discloses a fault current calculation method and system for a high-voltage alternating-current submarine cable grounding system and a storage medium, and the method comprises the following steps: enabling a power supply device and an electric device to be equivalent to an impedance and series voltage source combination and a load impedance based on the Thevenin equivalence theorem; in combination with the double-end grounding characteristic, a submarine cable loop is equivalent according to a pi type, and a three-phase equivalent circuit is constructed; determining a fault phase, and dividing the submarine cable as a left side and a right side by a fault point; a voltage loop equation is listed based on the Kirchhoff theorem, and a matrix recursion rule is deduced in combination with a double-side elimination principle. And establishing an analytic relationship between the main sections of the submarine cables at the power side and the short-circuit side and the fault circulating current according to a recursion rule. And with a fault point current equation as a boundary condition, left sheath fault circulation distribution is solved simultaneously. And repeating the steps on the right side to obtain right side distribution so as to obtain fault phase whole-line distribution. According to the method, the circulation distribution can be accurately calculated, the fault analysis accuracy and efficiency are improved, and support is provided for submarine cable operation and maintenance and the like.

The invention discloses a grounding resistance thermal-electric coupling prediction method and system suitable for various soil scenes. The method comprises the following steps: acquiring an electrode parameter, a soil parameter, a grounding fault parameter and initial temperatures of an electrode and soil; calculating an electrode current and a soil leakage current of the time step based on the electrode and soil resistivity of the time step; based on the electrode current and the soil leakage current of the time step, calculating the electrode temperature, the soil radial temperature distribution and the grounding potential rise of the time step by adopting a finite difference method; based on the electrode temperature and soil radial temperature distribution of the time step, updating the electrode resistivity and the soil resistivity of the time step + 1; if the end of the fault time is not reached, returning to continuously calculate the temperature of the electrode and the soil at the time step + 1; otherwise, outputting the electrode temperature and soil radial temperature distribution of each time step. According to the invention, thermal-electric dynamic coupling is considered, and accurate evaluation of the performance of the grounding system is realized.

The invention provides a fault positioning method and device for a power distribution network, a storage medium and electronic equipment, and the method comprises the steps: obtaining the zero-sequence voltage of a bus of the power distribution network, and determining a fault occurrence moment according to the zero-sequence voltage of the bus; obtaining the zero-sequence current of each measurement node on the feeder line of the power distribution network, and determining the fundamental frequency zero-sequence current corresponding to each measurement node according to the fault occurrence time and the zero-sequence current of each measurement node; calculating to obtain a similarity matrix according to the fundamental frequency zero sequence current of the measurement node at the head end of each feeder line; and according to the similarity matrix, determining the fault type of the power distribution network, including a bus fault or a feeder fault, and when the fault type is the feeder fault, determining the fault position according to the fundamental frequency zero sequence current of each measurement node on the fault feeder. According to the method, the fault position can be accurately positioned in a plurality of grounding systems, the anti-interference capability is relatively high, the adaptability to a low sampling rate is relatively good, and meanwhile, the economic cost can be greatly reduced.

The invention belongs to the technical field of fire-fighting alarm system construction, and discloses a construction technology for a fire-fighting automatic alarm system, and the technology comprises the following steps: S1, cable laying and protection; s2, accurately positioning and installing the detector; s3, system grounding and electromagnetic protection; s4, dynamic parameter adjustment and linkage test; and S5, performing three-dimensional shape scanning and compensation correction. A stable charge release path is formed through an independent grounding system and a multi-level shielding technology, external electromagnetic interference is effectively isolated, and real-time performance and accuracy of fire alarm signal transmission are guaranteed. The spatial layout optimization of the detector is combined with a laser calibration mechanism, the influence of structural shielding and airflow disturbance on sensitivity is broken through, and millisecond-level capture and positioning of fire characteristic signals are realized. A dynamic parameter closed-loop control and multi-system linkage verification technology ensures the cooperative response efficiency of emergency equipment under extreme working conditions, and constructs a whole-process security closed loop from early warning to disposal.

The invention discloses a grounding system safety monitoring method and device. The method comprises the following steps: acquiring target frequency domain characteristic data, including target frequency spectrum data and target phase deviation data, of a target grounding system; determining a target similarity between the target frequency domain characteristic data and preset reference frequency domain characteristic data, wherein the reference frequency domain characteristic data comprises reference frequency spectrum data and reference phase deviation data which are acquired under the condition that the grounding impedance is normal; if the target similarity is lower than a preset threshold value, determining that the target grounding system has a fault; analyzing the target frequency domain feature data by using a pre-trained fault classification model to obtain a fault reason and a fault level; and if the fault level exceeds the preset alarm level, generating fault alarm information, and generating a fault processing work order. According to the invention, the technical problem that the safety of the grounding system is difficult to control efficiently in real time due to the complex grounding impedance measurement process in the related scheme is solved.

The invention relates to the technical field of railway comprehensive grounding, in particular to an equipotential connection method for electrical equipment of a comprehensive grounding system of an interval trackless circuit. The method comprises the following steps that in railway bridge and tunnel sections, a steel rail replaces a through ground wire to serve as a common ground wire, a grounding device is electrically connected with the steel rail in a single-point mode according to a preset distance, and electrical equipment is electrically connected with the grounding device. The invention provides an equipotential connection method for an electrical equipment facility and an integrated grounding system in order to meet the requirements of integrated grounding specifications under the condition that a track-free circuit is arranged in an interval and a through ground wire is replaced by a steel rail. The problems that interference is generated due to uneven ground potential between electrical equipment facilities in the same system and dangerous contact voltage exists on the electrical equipment facilities are solved.

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.