254 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 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 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 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 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 discloses a grounding resistance regular monitoring system and method, and belongs to the technical field of power equipment state monitoring. The system comprises a pulse generation module, a measurement module, a control module, a protection module and a communication module. The core lies in that a low-amplitude short-time-range direct-current pulse current is adopted to be injected into a grounding system, the pulse amplitude, width and frequency parameters are optimized to be always lower than the action threshold value of a relay protection device, and therefore accurate measurement is achieved on the premise that power is not cut off and misoperation is not caused. Meanwhile, historical data trend analysis and soil environment factors are fused, the deterioration trend of the grounding resistance is intelligently predicted, early warning is performed in advance, and a resistance reduction device can be linked for automatic adjustment. The method effectively solves the problems that a traditional measurement method needs power failure and is poor in interference resistance and an existing online monitoring technology is likely to trigger protection by mistake, and achieves safe, accurate, automatic and intelligent monitoring, operation and maintenance of the grounding resistance.

The invention provides a high-voltage cable sheath grounding fault diagnosis method and device and electronic equipment, and relates to the technical field of electrical fault diagnosis and detection. The method comprises the following steps: acquiring a multi-source state parameter, wherein the multi-source state parameter is used for representing a real-time operation state of a sheath grounding system corresponding to a high-voltage cable sheath; performing multi-source heterogeneous data processing on the multi-source state parameter to obtain a fundamental component and a harmonic component of the sheath current and a vibration energy value of the cable joint; determining a current fault type based on the multi-source state parameter, the fundamental component, the harmonic component and the vibration energy value; determining fault section position information based on the multi-source state parameters and the electric power topological graph of the high-voltage cable sheath; and determining a fault diagnosis result based on the current fault type and the fault section position information. The fault diagnosis method and device are used for improving the comprehensiveness and accuracy of fault diagnosis, reducing the possibility of misjudgment and missed judgment, and being convenient for maintenance personnel to quickly position and solve the fault problem so as to guarantee stable operation of a power system.

The invention provides an arc suppression coil grounding system zero-sequence overcurrent protection method based on zero-sequence voltage verification. The protection reliability is improved through multi-criterion fusion. The method specifically comprises the following steps: S1, arc suppression coil system fault starting criterion: monitoring a zero sequence voltage in real time, and triggering a protection algorithm when the amplitude of the zero sequence voltage exceeds a preset threshold value; s2, fault time calculation: calculating the duration time of a grounding fault based on the duration characteristic of the zero-sequence voltage; s3, fault position discrimination: in combination with the amplitude characteristics of the zero-sequence current, distinguishing an internal fault from an external fault; and S4, intelligent comprehensive decision making: fusing the transient and steady state characteristic quantities of the zero-sequence voltage and the zero-sequence current, and generating a protection action signal. According to the invention, by dynamically checking the correlation characteristics of the zero-sequence voltage and current, the problems of insufficient sensitivity and high maloperation rate of the traditional zero-sequence overcurrent protection in the arc suppression coil grounding system are effectively solved.

The invention relates to the field of grounding technology and electrical measurement, and discloses a grounding electrode current diffusion characteristic and environment correlation analysis method, which comprises the following steps: acquiring a ground electricity state vector representing soil electrochemical characteristics; constructing and calibrating a state phase space evolution model for describing time-space evolution of the vector; an adaptive dynamic analysis closed loop is executed, a state vector at the next moment and uncertainty are predicted through the model, an adaptive sensing protocol is generated based on the uncertainty to guide new data collection, a prediction result is corrected through new data, and a corrected state vector is obtained; and finally, based on the continuous corrected state vector, analyzing the causal association between the environment and the state, reconstructing three-dimensional complex conductivity distribution, and determining current diffusion characteristics such as grounding impedance through numerical calculation. According to the method, the limitation of static evaluation in the prior art is solved, and the dynamic prediction of the performance of the grounding system and the physical tracing of the abnormal cause are realized.

The embodiment of the invention provides a high-resistance grounding fault detection method and device, and the method comprises the steps: collecting the three-phase current of a preset monitoring point in real time, and enabling the preset monitoring point to be disposed at an incoming line of a multi-feeder line of a transformer substation; and according to the three-phase current and the three-phase current of the previous period, determining a three-phase current abrupt change composite quantity which represents the variable quantity of the unbalance degree of the three-phase current, and if the three-phase current abrupt change composite quantity is greater than a first preset threshold value, judging to start fault judgment. When fault judgment is started, whether a single-phase earth fault occurs in the multi-feeder line of the transformer substation or not is recognized according to the amplitude relation and / or the phase relation among the three-phase phase current break variables, and the three-phase phase current break variables represent the instantaneous variation of each phase current between adjacent periods. The method can effectively solve the problem that when the method is applied to a high-resistance grounding fault in a neutral point small-resistance grounding system, the detection precision is low due to the fact that the fault current is far lower than a conventional protection threshold value and other factors.

The invention discloses a neutral point ungrounded fault positioning device and method based on dynamic time window inversion, and belongs to the technical field of new energy power system fault detection. Aiming at the problems that most of the existing methods depend on single signal characteristics or fixed window length analysis and are difficult to adapt to time-varying characteristics and complexity of a fault transient process in a new energy current collection line, a sensor is used for sensing current generated between a transformer shell and a grounding point when a fault occurs, and dynamic time window selection and an integral inversion algorithm are combined, so that the time-varying characteristics of the fault transient process in the new energy current collection line are obtained. Processing and feature extraction are carried out on the voltage value, self-adaptive analysis of the fault transient waveform of the neutral ungrounded system is achieved, and fault features are accurately extracted. According to the method, the problems of fixed time window and insufficient feature extraction capability of a traditional method are solved, and the system fault positioning speed and precision are improved. In addition, the method can also realize real-time monitoring, fault positioning and data acquisition and storage of fault current, thereby improving the stability and operation and maintenance efficiency of the power system.

The invention provides a high-resistance grounding fault detection method, device and equipment and a storage medium, and the method comprises the steps: collecting a three-phase current and voltage signal of a small-resistance grounding system, and carrying out the processing of the three-phase current and voltage signal to obtain a zero-sequence current and a zero-sequence voltage; when the zero-sequence voltage energy characteristic meets a preset condition, calculating fault grounding resistance according to the zero-sequence current, the zero-sequence voltage and system electrical parameters; calculating a transient zero-sequence current characteristic value and a steady-state zero-sequence voltage characteristic value according to the fault grounding resistance, and comparing the characteristic values with a threshold value; and when the two characteristic values are both smaller than the corresponding threshold values, determining that the fault is a high-resistance grounding fault. According to the method, the fault grounding resistance is calculated, the transient state and steady state characteristic criteria are deduced based on the resistance, and the detection basis is converted from direct measurement of the fault current to analysis of the fault resistance characteristics, so that accurate identification of the low-current high-resistance grounding fault which is difficult to detect by a traditional method is realized.

The application discloses a method for simulating the parameters of a generator neutral point grounding system of an extended unit connection, which comprises an actual generator system and a simulated generator system in parallel operation, wherein the simulated generator system comprises a low zero sequence impedance transformer, a three-phase capacitor bank and a simulated generator neutral point grounding device; the parameter simulation test comprises the following steps: S1, relay protection configuration; S2, neutral point asymmetric voltage test of the generator neutral point grounding system of the extended unit connection; S3, neutral point displacement voltage test of the generator neutral point grounding system of the extended unit connection; S4, maximum capacitive current test of single-phase grounding of the generator neutral point grounding system of the extended unit connection; and S5, maximum fault current test of single-phase grounding of the generator neutral point grounding system of the extended unit connection. The application can effectively verify the grounding system performance of different grounding modes of the generator of the extended unit connection and determine whether the generator neutral point grounding mode meets the technical requirements.

A high-altitude double-grounding gas-filled cabinet gas tank structure comprises a gas tank formed by connecting a plurality of plates, the gas tank is filled with insulating gas, and the gas tank is divided into an upper gas tank, a middle gas tank and a lower gas tank along the height direction; the upper gas tank is internally provided with a first grounding system, the first grounding system is a two-station grounding switch and comprises a first guide sleeve and a first conducting rod, and one end of the first guide sleeve is provided with an insulation plugging structure, so that the first conducting rod can only move in a single direction; a second grounding system is arranged in the middle gas tank, the second grounding system is a three-station isolating switch, the three-station isolating switch comprises a second guide sleeve and a second conducting rod, and the two ends of the second guide sleeve are open, so that the second conducting rod can move in two opposite directions. Two sets of grounding systems are arranged, when one set of grounding system fails due to reasons, the other set of grounding system can still operate normally, and personal safety is guaranteed.

The application discloses a high-speed railway pantograph-catenary arc electromagnetic radiation interference modeling analysis method, constructs a pantograph-catenary arc-pantograph power supply system integrated model containing a traction substation model, a traction network model, a train traction transmission system model, a train-track return current grounding system model and a pantograph-catenary arc model; under a pantograph-off arc transient condition, arc current is obtained through simulation calculation; and based on the arc current, a relationship between arc radiation power and spatial equivalent electric field intensity is established to represent the influence of time-varying characteristics of traction network electrical parameters on pantograph-catenary arc electromagnetic radiation interference. Under the pantograph-off arc transient condition, the real-time changes of impedance and capacitive reactance parameters of the traction network are involved in the unified solution of arc current formation, radiation power evolution and spatial electric field intensity calculation, and meanwhile, key coupling factors of the train high-voltage system and the train-track grounding system are mainly considered, so that the accuracy and engineering applicability of pantograph-catenary arc electromagnetic radiation interference analysis are improved.

The utility model provides a GIS double grounding isolation knife switch, including base, mounting post, support device, support insulator, conductive system, grounding system, transmission system and operating mechanism, the base is equipped with the mounting post, the mounting post is equipped with the support device, the support device includes the support table and support rib plate, the support rib plate is equipped with the support insulator, the conductive system, the grounding system, the transmission system and the operating mechanism. The supporting rib plate is installed at the bottom of the supporting table, the supporting insulators are arranged on the two sides of the supporting table, the conductive system is located on the tops of the supporting insulators, and the conductive system is connected with the transmission system; the grounding system is mounted on the mounting column and is connected with the transmission system; the transmission system is located on the right side of the base, and the transmission system is connected with the operating mechanism; the operating mechanism comprises a hydraulic device and a control cabinet, the hydraulic device is arranged on the side face of the base, and the control cabinet is arranged in front of the base.

The invention belongs to the technical field of relay protection of a power distribution network of a power system, and provides a single-phase broken line grounding fault detection method for an ungrounded neutral system, which comprises the following steps of: 1, acquiring three-phase current signals of each feeder line; step 2, performing morphological filtering processing on the acquired negative sequence current signal; step 3, mapping the filtered negative sequence current signal to a time-frequency space with u as a variable; 4, searching an optimal twiddle factor according to the energy focusing characteristic of the time-frequency current signal; according to the method, the symmetric component method, the morphological filtering and the coordinate transformation technology are combined, so that the accuracy and the stability of single-phase broken line grounding fault feature extraction of the neutral ungrounded system are remarkably enhanced, and the precision and the reliability of fault detection are greatly improved; and meanwhile, the optimal twiddle factor is adaptively determined based on the feeder energy concentration ratio, so that the detection strategy can flexibly adapt to different fault conditions, and the fault detection efficiency and success rate under a complex power grid structure and variable operation conditions are effectively improved.

The invention discloses an electromagnetic compatibility design method for a low-orbit satellite system, and aims to solve the problems that the traditional design focuses on a single machine, measures are isolated, and complex electromagnetic interference of the low-orbit satellite system cannot be handled. The method comprises the following steps: S1, analyzing a system-level electromagnetic environment and requirements, determining parameters, and identifying an interference source and a coupling path; s2, providing a layered and graded electromagnetic compatibility framework including platform and load isolation, power supply interference suppression, satellite-borne cable network optimization and grounding system construction; s3, performing frequency resource and signal integrity management, planning a frequency spectrum, and optimizing a clock and a digital circuit; s4, providing a software anti-interference and fault-tolerant mechanism, and realizing data verification, instruction voting and state monitoring; s5, performing on-orbit electromagnetic compatibility prediction; and S6, carrying out ground test verification. According to the method, a full-link design system is formed, interference risks are avoided in advance, and the operation stability and data reliability of the satellite in a complex electromagnetic environment are improved.

The invention discloses a two-point grounding fault model analysis method in a neutral point non-effective grounding mode, and aims to solve the problem that a unified accurate mathematical model suitable for a neutral point non-grounding and arc suppression coil grounding system under an in-phase two-point grounding fault is lacked in the prior art. According to the method, a fault network topology is reconstructed, a multivariate function equation set containing a fault position, ground capacitance, arc suppression coil parameters and a power supply initial phase angle is established, explicit analytical expressions of zero-sequence voltage current and phase voltage current are deduced, and a transient process is modeled in combination with a state space method. And accurate description of a fault characteristic quantity spatio-temporal evolution rule is realized. By adopting the above technical scheme, the method can provide a modeling basis which can be directly called for high-fidelity simulation platforms such as RTDS, and supports intelligent protection algorithm development and fault diagnosis system optimization.

The utility model discloses a pulse modulation circuit of an ultra-wideband super-continuum fiber laser, belongs to the technical field of ultra-wideband super-continuum fiber lasers, and solves the problem that the phase noise floor of a clock circuit is directly lifted due to the fact that power supply ripple coupling and LDO filter network efficiency is insufficient, for example, the output capacitance ESR is too high or a pi-type filter is missing. Comprising an input filtering module, a low dropout linear regulator module, a pi-type filter module, a clock power supply distribution module and a grounding system module. According to the utility model, high-frequency ripple filtering, voltage ripple depth suppression and residual noise absorption are carried out on power supply output through a three-stage sequential filtering framework, and finally, super-stable power supply with a phase noise base lower than-152dBc / Hz and 1kHz offset is provided for the clock circuit, so that the time sequence precision of super-continuum spectrum laser pulses is ensured.

The application provides a kind of giant hydropower plant transformer temporary grounding system and method, belongs to transformer maintenance grounding technical field.System includes transformer, grounding device seat body, grounding device, transmission gear set, rotary locking device, grounding sliding base and state monitoring assembly;Grounding device can overturn switching state, through gear linkage drive grounding locking contact automatic plug-in completes grounding end installation, piston rod automatic extension realizes conductor end butt joint and locking, with mechanical locking and double-point redundant grounding.Installation follows first grounding end, then conductor end, removal first removes conductor end, then removes grounding end specification sequence, cooperate state switch to realize remote real-time monitoring and position identification.The application is easy to operate, without manual contact grounding body, high safety and reliability, can be single set commonly used in multiple transformers, greatly improves the safety management level and operation efficiency of giant hydropower transformer maintenance.

The utility model belongs to the technical field of lightning protection current transformers, and particularly relates to an energy storage current transformer with a lightning protection module, which comprises a current transformer shell, a connecting seat connected to the outer side of the current transformer shell, a lightning protection assembly connected to the current transformer shell, and a lightning protection device connected to the inner side of the current transformer shell, the surge protector and the lightning protection device are arranged on the inner side of the converter shell, the surge protector and the lightning protection device are connected with an external grounding system through a grounding wire, the movable ventilation part assists in air exhaust and heat dissipation of the interior of the converter shell, the lightning protection device is matched with the grounding wire, and when lightning stroke occurs, lightning impulse energy is absorbed and discharged by the grounding wire through the external grounding system. And meanwhile, the surge protector works, so that the possibility that other devices in the box body are damaged when the lightning protection device generates an arc spraying phenomenon is reduced.

The invention relates to the technical field of data processing, in particular to a high-voltage single-core cable intermediate joint grounding system which comprises an intermediate joint module, a grounding cable module, a grounding box module and a control device module. The intermediate joint module adopts a stepped silver-plated contact surface to embed a contact resistance monitoring unit; the control device module collects a resistance signal, a discharge current signal, a temperature rise signal and a surge frequency signal through a communication bus, calls pre-stored historical data and a fault mode library containing a fault mapping relation, and inputs the data into the genetic algorithm unit to generate a crimping adjustment instruction, a surge sensitivity instruction or a maintenance early warning instruction. And the system executes a crimping adjustment instruction to dynamically adjust the oil pressure of the hydraulic execution mechanism, executes a surge sensitivity instruction to modify the conduction threshold value of the surge protection unit, and executes a maintenance early warning instruction to push a grading maintenance notification. Through cooperation of structure optimization and closed-loop control, contact resistance rise, circulation accumulation and overvoltage impact are inhibited, and risks of grounding failure and cable sheath breakdown are reduced.

The application provides a small-current grounding system single-phase grounding fault line selection method, and relates to the technical field of power distribution network fault detection.The method calculates the capacitive current of the system according to the measured zero sequence current data, counts and sums the capacitive current of each line to obtain the total capacitive current of the system, calculates the compensation degree of the arc suppression coil, extracts the fault characteristics, identifies the fault line after data processing and correction, compares the corrected zero sequence current signals of the fault line and the non-fault line, determines the fault line according to the difference between the corrected zero sequence current signals, and has high practicability and wide application prospect.

The invention relates to the technical field of power system automation and relay protection, and discloses a low-current grounding system fault line selection and closed-loop control method and device, and the method comprises the steps: applying preset parameter disturbance to an arc suppression coil in a system after the system is detected to have a grounding fault; in the process of applying the parameter disturbance, synchronously collecting zero-sequence current of each outgoing line as a response signal; analyzing the response signal, and determining a fault line and a fault property; and executing a corresponding closed-loop control strategy according to the determined fault line and the fault property. After a fault is detected, an arc suppression coil is utilized to inject a high-frequency pseudo-random binary sequence as a disturbance signal, and a cross-correlation analysis algorithm is adopted to process the zero-sequence current response of each line, so that a fault feature component related to a disturbance source can be accurately extracted from strong background noise; therefore, high-precision selection of the fault line is realized.

The invention discloses an anti-electromagnetic interference design method for a wheel-foot humanoid robot in an industrial scene, and particularly relates to the technical field of robots, comprising: S1, constructing a dynamic following electromagnetic shielding structure; s2, establishing a hybrid drive isomeric map filtering system; s3, implementing cross-level electromagnetic compatibility collaborative design; and S4, whole machine cable wiring and grounding system optimization are carried out, layered bundling and directional wiring strategies are adopted, a hybrid grounding model is applied, a low-frequency circuit is in single-point grounding, a high-frequency circuit is in multi-point grounding, and subsystems are connected to a central grounding point through a low-impedance grounding bus. The electromagnetic leakage is avoided, the overall electromagnetic compatibility of the system is enhanced, and the common-mode interference and the ground loop influence are reduced, so that the control precision and the operation stability are ensured.

The invention discloses a power grid grounding simulation method and system based on multi-parameter coupling modeling. The method comprises the following steps: acquiring soil resistivity, lightning stroke current waveform data and morphological structure information of a grounding electrode at different depths and geographic positions; constructing a recursive coupling current equation based on time history feedback, and recursively calculating a local grounding current distribution function at the current moment and at the spatial position by adopting a multi-channel dynamic weighting mechanism based on the recursive coupling current equation; fractal dimensions are dynamically calculated according to the soil resistivity and the morphological structure information of the grounding electrode, and a fractal current distribution function is established based on the fractal dimensions and a local grounding current distribution function; the local current value and the fractal current distribution function are fused, the total grounding current is dynamically calculated in a time integration mode, and step voltage is calculated in combination with a current response function, the soil resistivity and the lightning stroke waveform; and determining the state of the grid grounding system based on the total grounding current and the step voltage.

The invention discloses a method for protecting and judging faults in a transformer area of a small-resistance grounding system, and relates to the technical field of relay protection of a power system, and the method is executed by a transformer protection device when the electrical quantity of the system meets the starting criterion of a starting element in the transformer protection device. Comprising the following steps: based on a small resistance grounding system single-phase grounding fault model, obtaining high-low voltage side three-phase current of a transformer when a single-phase grounding fault occurs; obtaining a high-low voltage side break variable current component of the transformer according to the high-low voltage side three-phase current of the transformer when the single-phase earth fault occurs, judging whether the high-low voltage side break variable current component of the transformer meets a pre-constructed internal fault break variable current criterion or not, if so, judging that the internal fault occurs, and executing a protection action; otherwise, determining that the fault is an external fault. The method is used under the condition of new energy access, when a transformer has a single-phase earth fault, accurate identification of a fault area is realized, an internal fault and an external fault are distinguished, and a protection action can be quickly performed.

The utility model provides a capacitance current measuring circuit of a grounding system through a phase-controlled arc suppression coil, which comprises a phase-controlled arc suppression coil and a voltage source circuit, and is characterized in that the voltage source circuit is connected in parallel with a filtering winding of the phase-controlled arc suppression coil and is used for injecting voltage into the phase-controlled arc suppression coil; the power supply circuit comprises a capacitor Xcx, a transformer T2, a solid-state switch and an alternating-current power supply; the capacitor Xcx is used for dividing voltage and limiting voltage applied to the two ends of the filter winding induction coil; the capacitor Xcx is connected in series to one side of the transformer T2, the other side of the transformer T2 is connected in series with the solid-state switch, and one side of the solid-state switch is externally connected with an alternating current power supply. The voltage source circuit is introduced to be connected with the filtering winding of the phase-controlled arc suppression coil in parallel, voltage is injected into the phase-controlled arc suppression coil, the capacitive current of a grounding system can be accurately measured, the capacitor Xcx not only plays a role in voltage division, but also effectively limits the voltage applied to the two ends of an induction coil of the filtering winding, and therefore the voltage of the grounding system can be accurately measured. And the safety and the stability of the circuit are improved.

The invention discloses a fault cause analysis method and system for a small-current grounding system, and the method comprises the steps: obtaining a topological structure of the small-current grounding fault system when a small-current grounding fault occurs; acquiring an equipment recorded wave of equipment closest to the physical distance of the fault point; zero-sequence voltage and zero-sequence current in equipment recording and the length of a single cyclic wave are extracted; according to the length of a single cyclic wave and a set step length, carrying out cyclic wave interception on the equipment recorded wave; the intercepted cyclic waves are processed; inputting the zero-sequence voltage, the zero-sequence current and the processed cyclic waves into a plurality of discriminators for different fault causes to obtain classification probabilities of different types of fault causes; wherein the discriminator comprises a feature module and a classifier; and based on the classification probabilities of different types of fault inducements, a final research and judgment result is selected according to actual requirements. According to the invention, research and judgment depend on the feature module and the classifier, and the real-time requirement of a modern power distribution network on rapid fault diagnosis and isolation can be met.