684 results about "High-voltage direct current" patented technology

The present invention relates to the technical field of circuit control, and relates to a direct-current high-voltage generator regulation and control method and system based on intelligent feedback. A fuzzy control logic operation is performed on an output current flux value and an input voltage fluctuation factor of a load experimental object, so as to obtain the disturbance amplitude of a voltage fluctuation state for a current flux change trend; if a step-up transformer can execute a PID control technology by adjusting a transformation ratio, PID real-time adjustment parameters are calculated, and a crossover mutation operation of individuals is performed on the basis of a fitness function, so as to generate a first boost regulation and control scheme; and if the step-up transformer cannot execute the PID control technology by adjusting the transformation ratio, a calibrated state feedback controller is constructed on the basis of a state variable of the current step-up transformer and an adjustment signal output amplitude, so as to generate a second boost regulation and control scheme. The present invention achieves intelligent feedback regulation and control by independently analyzing components of direct-current high-voltage generators, improving the stability and accuracy of outputting high-voltage direct current.

The invention relates to a PFC-PWM (Pulse Width Modulation) dual-mode control method for a high-voltage direct-current power supply with a wide output voltage range. The output current of the high-voltage direct-current power supply is detected in real time, the critical threshold value of the load impedance is mapped into the hysteresis interval of the output current, the theoretical boundary of mode switching is obtained, and the control mode is dynamically adjusted. In order to further guarantee smooth switching of the two control modes, hysteresis control logic is designed, and undisturbed smooth switching of the PFM mode and the PWM mode is achieved. Based on an energy equivalence principle and a frequency consistency constraint of a critical load SWL working point, a current threshold criterion and a parameter pre-synchronization strategy are constructed, seamless connection of a mode switching process in a frequency domain and an energy domain is ensured, a transient oscillation risk is remarkably reduced, and a guarantee is provided for continuous and stable output of a full-range load working condition.

The invention relates to a controllable turn-off converter valve for a high voltage direct current (HVDC) system, each converter valve arm comprises a valve arm voltage-sharing device and a plurality of cascaded controllable turn-off converter modules, and each controllable turn-off converter module comprises an assembly voltage-sharing device and a plurality of cascaded controllable turn-off converter assemblies. Each controllable turn-off current conversion assembly is configured to comprise at least one voltage-sharing circuit and at least one controllable switching device, and two ends of each controllable switching device are provided with one voltage-sharing circuit in parallel. Therefore, the controllable turn-off converter valve can realize voltage sharing at each level, the requirement of the controllable turn-off converter valve on the consistency of controllable switching devices is reduced, a large number of controllable switching devices can be connected in series in the same converter valve arm, and reliable conversion of extra-high voltage direct current transmission at the voltage level of + / -800 kilovolts and above is realized. The problem of commutation failure of the extra-high-voltage direct-current type converter valve is solved, and safe and stable operation of a power system is ensured.

The invention discloses a high-voltage direct-current cable state online monitoring method and system based on MMC low-frequency injection. The method comprises the steps that an MMC controller injects a low-frequency three-phase alternating-current signal into a direct-current cable based on an MMC low-frequency injection control strategy; the MMC low-frequency injection control strategy comprises the steps that an MMC controller adopts a double-closed-loop control mode composed of an outer voltage loop and an inner current loop; a voltage error is calculated through an outer voltage loop, and a differential-mode voltage Udiffdq * and a common-mode voltage Ucomdq * are calculated through an inner current loop, so that the MMC outputs a target voltage Ugoal signal to a direct-current cable; according to the method, active injection of the low-frequency alternating-current signal with the specific frequency and amplitude is achieved by setting the specific MMC control strategy, a hardware structure of a main loop of an MMC system does not need to be modified, and implementation is safe, easy, convenient and flexible; and meanwhile, online quantitative evaluation of the insulation state of the direct-current cable is realized, and the monitoring process is high in precision, simple, convenient and efficient.

The invention discloses a polypropylene insulation high-voltage direct-current cable and a production method thereof, and relates to the technical field of cables, the polypropylene insulation high-voltage direct-current cable comprises an insulation layer, the insulation layer comprises an insulation part arranged between a conductor shielding layer and an insulation shielding layer, the insulation part is provided with a plurality of limiting holes communicated with the insulation shielding layer, the limiting holes are filled with phase change parts, and the phase change parts can transmit heat on the inner side of the insulation layer to the outer side of the insulation layer; and the cable can be converted between solid and liquid along with the temperature of the cable so as to fill an air gap between the insulating layer and the insulating shielding layer. The plurality of limiting holes are formed in the insulating part, the limiting holes are filled with the phase change parts capable of generating phase change at low temperature, and the temperature difference between the two sides of the insulating part is reduced through the heat conduction capability of the phase change parts, so that the problem of charge accumulation caused by the overlarge temperature difference between the two sides of the insulating part is avoided; and meanwhile, separation or air gaps between the insulating part and the insulating shielding layer are filled through phase change of the phase change part.

The invention relates to an electric engine, a power device and an aircraft, and belongs to the technical field of aircraft power equipment.The electric engine comprises a power motor and a liquid cooling flow path arranged in the power motor and comprises a stator support; the heat dissipation system comprises a fan, a radiator and a heat dissipation motor, an outlet of the radiator is connected with an inlet of the liquid cooling flow path, an inlet of the radiator is communicated with an outlet of the liquid cooling flow path, and the fan is used for cooling the radiator and / or the power motor; the motor rear cover is fixedly connected with the stator bracket; and the two direct-current converters are both mounted on the motor rear cover and are both electrically connected with the heat dissipation motor. The two direct-current converters convert high-voltage direct current accessed by the electric engine into low-voltage direct current capable of being used by the heat dissipation motor, and the electricity utilization requirement of the heat dissipation motor is met. Due to the redundancy design of the two direct-current converters, when one path of low-voltage power supply breaks down, the other path of low-voltage power supply can still supply power to the heat dissipation motor in a low-voltage mode, and enough fault handling time can be provided for the whole power supply system.

The invention discloses a machine learning-based ultra-high-voltage direct-current transmission locking fault diagnosis method and system, and the method comprises the steps: obtaining various electrical quantity change data of each network node before and after a fault, screening out feature electrical quantities and feature nodes from the electrical quantity change data, and forming fault feature data; extracting a fault occurrence time point and a frequency component from the fault feature data through wavelet transform, constructing a fault signal model, and judging a fault position by adopting an extreme point detection method; constructing an input sequence according to the extracted fault occurrence time point and frequency component, and constructing a convolutional neural network model; expanding the input sequence into a time feature matrix, redistributing the weight of each feature in the time feature matrix by adopting a channel attention mechanism, and performing weighted average on the input time sequence of each time step length in the time feature matrix by adopting a time attention mechanism to obtain an improved convolutional neural network model; and training the improved convolutional neural network model, and extracting fault features of extra-high voltage direct current locking to complete fault diagnosis.

The invention discloses a high-voltage direct-current cable electromagnetic transient frequency domain modeling and time domain solving method, system, medium and equipment, and the method comprises the steps: obtaining an initialization parameter of a high-voltage direct-current cable, calculating an internal impedance matrix [Zi] of a multi-layer cross-section cable body during frequency calculation, and calculating an admittance coefficient matrix of the multi-layer cross-section cable body during frequency calculation; calculating ground loop impedance [] and potential coefficient [] of the air laying cable or the direct burial laying cable, and obtaining a total impedance matrix [] and a total admittance matrix [] of the cable at the time of frequency: importing obtained multi-frequency [] and [] calculation results into a PSCAD TLine module, and realizing time domain solution of frequency domain calculation by using a vector fitting model.

The invention discloses an ion pump power supply circuit. The circuit comprises a voltage regulation output module, a control module and a current-voltage conversion module, the input end of the voltage regulation output module receives low-voltage direct-current input voltage; the high-voltage output end of the voltage regulation output module is connected with the anode of the ion pump; the ion pump shell is electrically connected with the input end of the current and voltage conversion module through the electron gun shell; the output end of the current-voltage conversion module is electrically connected with the control module; the grounding end of the current-voltage conversion module is connected with the signal ground; the voltage regulation output module converts the low-voltage direct-current input voltage and outputs high-voltage direct-current voltage to the anode of the ion pump, so that working current is generated in the cavity of the ion pump and returns to the current-voltage conversion module through the shell of the ion pump and the shell of the electron gun; the current and voltage conversion module detects working current in the ion pump cavity and converts the working current into a voltage signal; and the control module determines the vacuum degree in the ion pump cavity according to the voltage signal.

The invention relates to the technical field of high-voltage electric appliance detection, in particular to a device and method for detecting the vacuum degree of a vacuum arc-extinguishing chamber, and the method comprises the steps: arranging a field emission cathode on one metal end cover of the vacuum arc-extinguishing chamber; an anode is arranged on the metal shielding cover close to the field emission cathode in the vacuum arc-extinguishing chamber; the high-voltage direct-current power supply is connected to the field emission cathode and the anode and is used for applying voltage to the electrodes so as to drive the field emission cathode to emit electron beams to impact the anode; the X-ray energy spectrum detector directly faces the anode, the X-ray energy spectrum detector is used for measuring bremsstrahlung X-ray energy spectrum generated when the electron beam impacts the anode, an electron emission source is actively arranged in the arc extinguish chamber, and the distribution of the X-ray energy spectrum generated by the electron emission source is measured. And high signal-to-noise ratio, high-precision and high-sensitivity vacuum degree quantitative detection is realized by utilizing the strong correlation between the energy spectrum form and the internal gas pressure.

The utility model belongs to the technical field of new energy automobiles, and particularly discloses a new energy automobile high-pressure liquid heater which comprises a heater body, a thick film heating plate, a heat insulation plate, a cover plate and an overheating protection circuit which are sequentially installed from bottom to top. The overheating protection circuit comprises four thermistors Rt1, Rt2, Rt3 and Rt4, an N-type MOS tube, a relay KJ, a heating resistance wire Rh, a resistor R1, a resistor R2, a resistor R3, a low-voltage direct-current power supply and a high-voltage direct-current power supply. According to the thick film heating plate, the water-drop-shaped turbulent flow columns and the turbulent flow teeth are arranged, so that the heat conduction efficiency and the heat exchange efficiency of the thick film heating plate in liquid are improved, and better convective heat exchange is realized; and the overheating protection circuit is arranged, so that the reliability of the heater during over-temperature protection is improved, and the heater is not only controlled by software.

The invention discloses a surge current suppression method and a surge current suppression system for an electricity utilization and acquisition terminal power supply, and the method comprises the steps: designing a surge current suppression circuit which comprises a current input circuit, an EMI circuit, a rectification circuit, a low-power-consumption surge current suppression circuit, an energy storage capacitor and a flyback power conversion circuit; external alternating current is obtained through the current input circuit, and then the external alternating current is converted into first high-voltage direct current through the EMI circuit and the rectifying circuit; the first high-voltage direct current is limited to charge the energy storage capacitor through the low-power-consumption surge current suppression circuit; and the second high-voltage direct current in the energy storage capacitor is transmitted to the flyback power conversion circuit for voltage conversion, and the low-voltage direct current is acquired and transmitted to an acquisition terminal power supply. The low-power-consumption surge current suppression circuit can automatically switch working states, efficiently suppress surge current and reduce circuit power consumption, is high in portability, can adapt to different power supply products by adjusting elements, and meets various surge suppression requirements.

A non-isolated bidirectional high-voltage direct current battery charger is made compatible with a ground-fault circuit interrupter (GFCI) at the DC output by adapting the power converter to control, in response to voltage or current sensors, a net current difference between forward current and return current to remain below a threshold of the GFCI. This can be done without compromising safety in the case of actual ground faults.

The invention discloses a server power supply system, a server, a topological structure generation method and a storage medium, and relates to the technical field of power electronics. According to the invention, a high-voltage centralized conversion-medium and low-voltage distributed distribution two-stage architecture and a physical isolation design of the first direct-current bus and the second direct-current bus are adopted, and an adaptive mounting platform is provided for load nodes such as a super-capacitor node and an energy storage node depending on the second direct-current bus; the mounting number of the load nodes can be determined based on the power required by the load nodes and the voltage and through-flow level of the second direct current bus, and high-voltage power supply conversion and power supply of the load nodes are separated, so that physical isolation of high-voltage direct current of the first direct current bus and low-voltage direct current of the second direct current bus is realized. The high-voltage direct current input is ensured to be safely, efficiently and stably distributed to each load node in the server after being converted. The problems of potential safety hazard and reliability risk caused by direct access of the high-voltage direct current to the load node, poor mounting adaptability of the load node and the like in the prior art are solved.

The invention discloses a vehicle-mounted high-power power supply and distribution system and method, and the method comprises the steps: enabling one end of an engine to be provided with a transmission wheel train and a high-voltage generator during the running process of a vehicle, and enabling the output rotating speed of the engine to be improved to the rated rotating speed of the high-voltage generator through the transmission wheel train; high-voltage direct current output by the generator drives a high-voltage electric appliance to work after being subjected to voltage stabilization and filtering by the high-voltage distribution box; when an automobile is parked and a mains supply is used, alternating-current mains supply is inverted into direct-current power through the high-voltage distribution box to drive a high-voltage electric appliance to work. The defects that a traditional vehicle cannot run and cannot supply power in a high-power mode under the parking condition can be overcome, especially the technical problem of power supply under the parking condition is solved, software system adaptation development is carried out through the comprehensive technical scheme of a high-power high-voltage silicon generator, mains supply inversion, power supply filtering and the like in combination with post-stage power utilization characteristics, and the power supply efficiency is improved. And stable power supply of the air-conditioning system under running and parking conditions is ensured.

The invention belongs to the technical field of ultra-high voltage direct current power transmission, and discloses a test system and method of a converter valve thyristor voltage detection board card, and the test system comprises a test cabinet and a test tool. An industrial control system is integrated in the test cabinet to set test parameters and criteria, an electric control unit loads an excitation source, an acquisition display unit acquires test data and presents the test data in an oscillogram, and a test tool fixes a tested board card. The industrial control system outputs a control instruction to drive the electric control unit to apply system test excitation, the actual working condition of the thyristor is simulated, and meanwhile, the acquisition and display unit automatically captures multichannel signal data; data are transmitted to the industrial control system through the electric control unit, and the board card performance is automatically analyzed and a test report is generated in combination with a preset criterion. By adopting the system, the problems of insufficient function verification, low test efficiency, vulnerable equipment, poor data accuracy and large manpower occupation are solved, efficient and lossless automatic test is realized, the test reliability is improved, and the operation process is simplified.

The invention provides a battery charging control method, a battery management system and electronic equipment, and relates to the field of lithium batteries. Aiming at the problems that a lithium ion battery is easy to separate out lithium and the charging speed is limited when the lithium ion battery is charged in a low-temperature environment, when the temperature of the battery is lower than a low-temperature threshold value, high-voltage direct-current voltage pulses are applied to the battery, and Joule heat is generated by utilizing internal impedance of the battery, so that rapid self-heating of the battery is realized. In addition, in order to avoid lithium precipitation, it is ensured that the pulse voltage is higher than the open-circuit voltage of the battery and the pulse current is lower than a safety threshold value in the high-voltage direct-current voltage pulse. Therefore, the temperature of the battery can be quickly raised to the safe charging temperature window in the low-temperature environment, so that quick charging is realized while the risk of lithium precipitation is avoided, and the usability and the safety of the battery in the low-temperature environment are remarkably improved.

An energy storage system converts variable renewable electricity (VRE) to continuous heat at over 1000° C. Intermittent electrical energy heats a solid medium. Heat from the solid medium is delivered continuously on demand. An array of bricks incorporating internal radiation cavities is directly heated by thermal radiation. The cavities facilitate rapid, uniform heating via reradiation. Heat delivery via flowing gas establishes a thermocline which maintains high outlet temperature throughout discharge. Gas flows through structured pathways within the array, delivering heat which may be used for processes including calcination, hydrogen electrolysis, steam generation, and thermal power generation and cogeneration. Groups of thermal storage arrays may be controlled and operated at high temperatures without thermal runaway via deep-discharge sequencing. Forecast-based control enables continuous, year-round heat supply using current and advance information of weather and VRE availability. High-voltage DC power conversion and distribution circuitry improves the efficiency of VRE power transfer into the system.

The invention discloses a corner module assembly for an electric vehicle and the electric vehicle, and relates to the technical field of new energy automobiles. The angle module assembly comprises a wheel edge controller, a driving motor, a braking motor and a steering motor, the wheel edge controller comprises a shell, a control circuit and a driving circuit, and the control circuit is used for controlling the driving circuit to drive the driving motor, the braking motor and the steering motor; the surface of the shell comprises a plurality of communication interfaces, a power battery interface, a low-voltage battery interface and a plurality of current output interfaces. The driving circuit is used for receiving power supplied by a low-voltage battery through the low-voltage battery interface and supplying power to the steering motor and the brake motor through the plurality of current output interfaces; the driving circuit is further used for receiving high-voltage direct current output by the power battery through the power battery interface, converting the high-voltage direct current into first alternating current and then supplying power to the driving motor through the multiple current output interfaces. According to the scheme, the number of control chips is reduced, the unsprung mass is reduced, and the integration level and the economical efficiency are improved.

The invention discloses a multi-battery-pack charging management system and method and engineering machinery, and the system comprises a VCU which is configured to execute the starting control of a whole vehicle, the logic scheduling of a charging process, the cooperative management of high-voltage parts, and the processing of an abnormal state; the number of the battery packs is multiple, each battery pack is internally provided with an independent BMS, and the BMS is configured to monitor the running state of the battery packs in real time; the PDU relay is integrated with positive and negative pole contactors corresponding to the battery packs and a PDU auxiliary loop contactor connected in series with the DCDC high-voltage power supply loop; the DCDC is configured to convert the high-voltage direct current output by the battery pack into low-voltage direct current, and the working state of the DCDC is regulated and controlled by the VCU; the charging gun has an anti-misplug mechanical structure and a safe locking function. The multi-battery-pack parallel charging function of the vehicle under any working condition can be achieved, cooperative work and safe operation of all the battery packs and high-voltage components in the charging process are ensured, and the charging efficiency and the system reliability are effectively improved.

The invention discloses a direct-current power generation system and a control method thereof, which innovatively adopts a photovoltaic and energy storage double-cascade architecture and combines an intelligent protection and coordination control strategy. The system comprises N photovoltaic cascade subunits and M direct current energy storage modules, and each unit is provided with a bypass protection device. Each photovoltaic cascade subunit is integrated with an MPPT controller, an isolation converter and a bypass protector containing a piezoresistor and a diode; the energy storage module adopts a non-isolated DCDC conversion circuit, and a matched energy storage bypass protector is integrated with a bidirectional power electronic switch, a piezoresistor and a mechanical isolation switch. The technical problems of large voltage fluctuation, low system reliability, difficult maintenance and the like of a traditional direct current system are effectively solved, the service life of equipment is prolonged while the system stability is improved, and the system is particularly suitable for medium-high voltage direct current power supply scenes.

The invention discloses a polypropylene grafted copolymer self-reinforced polypropylene cable insulation material and a preparation method thereof, and relates to the field of high polymer materials. The preparation method of the material comprises the following steps: firstly, preparing a polypropylene grafted copolymer by a melt grafting method or an electron beam radiation grafting method; carrying out melt blending on the master batch and polypropylene to prepare a primary master batch; and finally, carrying out melt blending on the primary master batch, polypropylene, an antioxidant, a voltage stabilizer and a processing aid to obtain the cable insulating material. The polypropylene grafted copolymer induces the matrix polypropylene to generate a beta crystal form, and the beta crystal form and the polar vinyl monomer jointly realize self-enhancement independent of an elastomer, so that the toughness, the heat resistance and the direct-current dielectric property of the material are synchronously improved, and the problem of performance reduction caused by blending of traditional elastomers is solved; the method is suitable for the high-voltage direct-current cable insulation field.

A medical imaging system includes an X-ray source configured to emit X-rays. The medical imaging system also includes a high voltage generator configured to provide power to the X-ray source. The medical imaging system further includes a high efficiency power distribution unit configured to receive electrical power from an electrical grid and to store the electrical power, wherein the high efficiency power distribution unit includes an active rectifier configured to regulate a high voltage direct current outputted to components of the medical imaging system including the high voltage generator.

The invention discloses a rotary transformer testing device and method. The rotary transformer testing device comprises a motor, a motor controller, a high-voltage direct-current power supply, an upper computer, an oscilloscope and low-voltage electrical performance testing equipment, the motor drives the rotary transformer rotor to rotate; the high-voltage direct-current end of the motor controller is connected with a high-voltage direct-current power supply, and the output end of the low-voltage electricity performance test equipment is connected with the low-voltage power supply end of the motor controller to generate a low-voltage interference signal or provide stable low-voltage electricity to be input to the motor controller; the communication ends of the motor controller, the high-voltage direct-current power supply and the low-voltage electrical performance test equipment are connected with the upper computer; the excitation end and the acquisition end of the motor controller are respectively connected with the input end and the output end of the resolver stator, and the motor controller provides excitation signals for the resolver stator and acquires induction signals fed back by the resolver stator; the acquisition end of the oscilloscope is connected with the input end and the output end of the rotary transformer stator, and the oscilloscope acquires and displays waveforms of excitation signals and induction signals. According to the invention, the accurate resolver condition can be obtained, and misjudgment can be avoided.

The invention discloses a high-voltage direct-current power supply system and electronic equipment, and relates to the technical field of power supply, the high-voltage direct-current power supply system comprises a high-voltage direct-current main copper bar and a high-voltage direct-current standby copper bar which are connected to a high-voltage direct-current power supply in parallel, a physical-level redundant power supply path is formed, and electrical parameters of the high-voltage direct-current main copper bar are monitored through a state monitoring module; the control module quickly judges a fault based on the monitoring data and generates a first switching control signal, so that the driving power supply path switching module automatically switches a load power supply path from a high-voltage direct-current main copper bar to a high-voltage direct-current standby copper bar, and the problem of power supply interruption caused by the copper bar fault of the high-voltage direct-current system is solved; the beneficial effects of improving the continuity and reliability of the high-voltage direct-current power supply system and ensuring the uninterrupted operation of the data center in the high-voltage power supply environment are achieved.

The invention relates to the technical field of testing and application of power semiconductors, in particular to a SiC MOSFET gate oxide reliability testing device and method, and the device is provided with a high-voltage direct-current voltage power supply, an auxiliary direct-current voltage source, a signal generation device, a half-bridge testing circuit, a gate drive circuit, a load inductor, a load resistor and measuring equipment. According to the method, the stress time required for evaluating the reliability of the device can be remarkably shortened, meanwhile, the threshold voltage drift characteristics of the device under different drain-source voltage stresses can be more accurately described, compared with a traditional static bias and grid switch stress test method, the influence of dynamic drain-source voltage and current is effectively introduced, the accuracy of a model test result is improved, and the reliability of the device is improved. The method has a certain application value for evaluating the reliability of the gate oxide layer of the SiC MOSFET.

The utility model provides an active liquid cooling device for a high-voltage direct current charging gun, which relates to the technical field of charging guns and comprises a liquid cooling machine, a liquid storage tank is fixedly connected to the surface of one side of the liquid cooling machine, a pump machine is arranged at the bottom of the liquid storage tank, and a liquid outlet pipe is fixedly connected to the output end of the pump machine. The surface of the liquid cooling machine is fixedly connected with a fan, the surface of one side of the liquid cooling machine is fixedly connected with a heat exchanger, the surface of the liquid cooling machine is provided with a liquid return pipe, the surface of the liquid storage tank is provided with a filtering device, and the filtering device comprises a filtering tank. According to the liquid cooling machine, impurities in the cooling liquid can be timely and rapidly filtered, so that the purity and the effectiveness of the cooling liquid are ensured, the blockage of internal parts of the liquid cooling machine is not easily caused, the charging gun can be better cooled, and the use effect and the functionality of the liquid cooling machine are further improved.

This application relates to the field of insulated switch application technology, and particularly to a method and apparatus for characterizing partial discharge features in ultra-high voltage direct current (UHVDC) GIS. The method includes: generating a partial discharge pulse sequence based on the light signals generated by electroluminescence and gas ionization emission in the UHVDC gas-insulated switchgear; generating a spectrum of at least one parameter pair based on the amplitude and corresponding time of the partial discharge pulses; and generating a feature fingerprint map of at least one parameter pair based on the spectrum. The method also involves extracting at least one statistical feature from the kernel density sequence of the at least one parameter pair based on the feature fingerprint map, and generating a characterization result of the partial discharge feature based on the at least one statistical feature. This solves the problem that partial discharge detection is easily affected by electromagnetic interference, mechanical vibration, and environmental noise, making it difficult to effectively extract and accurately identify the actual partial discharge signal, thus affecting the accuracy and reliability of the detection results.

The application provides a non-unit two-section protection method for a high-voltage direct current power grid direct current transmission line, comprising the following steps: (1) in a normal state, real-time detection of current and voltage at the installation position of the non-unit protection is performed, and line mode voltage and zero mode voltage are obtained; when the current rate of change is greater than a threshold value, step (2) is performed; (2) fault polar selection is performed, and a pre-action instruction is then issued to a circuit breaker on a potential fault pole to perform first commutation; meanwhile, step (3) is performed; (3) a section I protection time window is started; if the voltage rate of change at the installation position of the non-unit protection meets section I protection criteria, a second commutation instruction is issued to a direct current circuit breaker to perform second commutation; otherwise, step (4) is performed; (4) a section II protection time window is started after a delay; if the line mode voltage rate of change at the installation position of the non-unit protection meets section II protection criteria, a second commutation instruction is issued to a direct current circuit breaker to perform second commutation; otherwise, a pre-action return instruction is issued to the direct current circuit breaker.

The application provides a plasma wall friction drag sensor, which is in a sheet shape as a whole and comprises a high-voltage electrode (10), a grounding electrode (20), a charge collecting electrode (30) and an insulating base (60). The application also provides a plasma wall friction drag sensor system, which comprises the above-mentioned sensor, a high-voltage direct-current power supply (701), a current-limiting resistor (702), a first discharge resistor (703), a grounding terminal (801), a first voltage amplifier (802) and a first output terminal (803). Furthermore, the working process of the above-mentioned plasma wall friction drag sensor system is given. The application also extends the above-mentioned sensor and sensor system to form a double sensor, a multiple sensor and a sensor system. The application can solve the technical problem of how to measure the airflow wall friction drag at low cost, high frequency response and robustness.