217 results about "Pulse test" patented technology

A control scheme for reducing current imbalance between parallel bridge circuits in a power converter system is provided. The power converter can include a plurality of bridge circuits coupled in parallel to increase the output power capability of the power system. The parallel bridge circuits can be controlled pursuant to a control scheme for reducing current imbalance between the parallel bridge circuits. In particular, a pulse test can be performed in which a pulse is applied to each of the plurality of bridge circuits. The switch timing of the switching elements responsive to the pulse can be measured and analyzed to determine a timing difference adjustment for one or more of the switching elements of the plurality of bridge circuits. The timing difference adjustment can be stored and used to adjust all subsequent switching events in the parallel bridge circuits.

The invention relates to a method for enhancing the screening consistency of lithium-ion power batteries. The method comprises the steps of (1) screening single batteries produced under the same condition; (2) carrying out full-charging full-discharging test for N times on the single batteries, and screening the single batteries with constant current ratio more than 90%, platform time being 45 minutes and capacity difference values less than 50mAh; (3) standing at high temperature of 45 DEG C for 10 days under an uncharged condition; (4) standing at normal temperature for 4-6 hours, and screening the single batteries with inner resistance difference of 2-3m omega and uncharged open-circuit voltage difference less than 100 mV; (5) respectively discharging for 10 seconds through 3-5C current in a 10%-20% SOC state and charging for 10 seconds through 2-3C under a 80%-90% SOC condition, acquiring transient dynamic voltage of charging and discharging at the 10th second, and screening the single batteries with dynamic voltage difference values of charging and discharging within 10mV. Compared with the prior art, the method disclosed by the invention has the advantages that the polarization difference of the single batteries can be increased, so that the state difference inside the batteries can be represented, and the batteries subjected to a pulse test have very high consistency.

The invention is applicable to the technical field of computers and provides a method and a device for measuring the human body pulse. The method comprises the following steps that: multiple frames of light transmission finger bitmaps are continuously collected according to the preset time intervals; the red value saturation of the pixel points in the pulse measurement region in each frame of finger bitmap is obtained; a red value saturation rectangular coordinate system adopting the horizontal axis for representing pixel point sequence numbers and adopting the vertical axis for representing pixel points is respectively built for each finger bitmap, in addition, dotting is carried out in the rectangular coordinate system according to the red value saturation in the finger bitmaps, and thedotted points are connected for forming a red value saturation curve; the area of shapes circulated by the horizontal axis and the vertical axis in each coordinate and the red value saturation curve is respectively calculated; a plurality of shape area peak values are obtained, and in addition, the human body pulse frequency is calculated according to the time difference of the shape area peak values. The human body pulse frequency can be calculated only through electronic equipment, such as computers with cameras, mobile phones and the like, users can conveniently measure the pulse, and the development cost of special pulse test devices is reduced.

The invention belongs to the field of power electronic device measuring techniques and particularly relates to a circuit and method for quickly obtaining dynamic parameters of a power electronic device. The circuit mainly comprises a direct-current power supply, a bus capacitor, a multi-pulse signal driver board, a diode, the power electronic device, a load inductor, a current transformer and an oscilloscope. The method is mainly used for changing dipulse testing in national standards into multi-pulse testing with pulse widths, high-low level duration and the number of pulses adjustable. By measuring voltage, currents and multi-pulse signal waveforms of the two ends of the power electronic device, multiple turn-on and turn-off process waveforms and the dynamic parameters under different currents are obtained at a time, and human adjustment can be carried out according to simulated testing currents.

The invention relates to a device for searching fault points of a cable or a pipeline. The device for searching fault points of the cable or the pipeline comprises a transmitter and a receiver, wherein the transmitter is composed of a control system, a signal producing circuit, a signal amplification circuit, a gear shifting circuit or a voltage limiting circuit for alternating current or direct current output, a power detection circuit, a power regulating circuit, a impedance measurement circuit, an analogue / digital (A / D) sampling circuit, a keyboard and a display device. The device for searching fault points of the cable or the pipeline comprises four detection circuiting methods: low-frequency alternating current detection method, high-frequency alternating current detection method, pulse detection method and impedance detection method. The four detection methods are used and provide evidence for each other, and thus fault points are determined reliably. When the cable or the pipeline is detected, cable or pipeline condition changes, cable line-breaking fault condition, cable insulation condition relative to the ground and the like are considered, and then fault points are found out.

A component interface module (CIM) arbitrates through priority logic component command signals from redundant systems and integrates the selected priority command signal with component feedback signals in component logic to generate a control signal for a component in a complex plant. The non-software based CIM is programmable for use with a variety of plant components. The component logic includes blocking logic that prevents or terminates generation of the control signal such as when component activation has been completed. Diagnostics incorporated into the CIM include: an input port interface test, a pulse test that continuously checks for proper propagation of test pulses through the priority and component logic, and a test of the functioning of the CIM output device such as a relay.

The invention discloses an IGBT device test circuit and test method. The test circuit comprises a double-pulse test module used for testing on and off performance of an IGBT, a current endurance capability test module used for testing the current endurance capability of the IGBT under the condition of simulating the bipolar short circuit of a converter valve, an acquisition module used for acquiring the collector voltage and the emitter current of the IGBT, and a protection module used for cutting off the connection between the double-pulse test module and the IGBT when the collector voltage and / or emitter current of the IGBT exceed / exceeds a corresponding preset threshold(s). According to the invention, the switching-on and switching-off performance of the IGBT is tested by using the double-pulse test module, and the situation that the surge current impacts the IGBT under the bipolar short circuit condition of the converter valve is simulated by using the square wave current continuously output by a current source, so that the comprehensiveness and diversity of the IGBT performance test are further improved.

The invention belongs to the technical field of electric power, and particularly relates to an IGBT junction temperature estimation method based on an IGBT thermoelectric coupling model, which is characterized in that an experimental platform based on a thermosensitive parameter method and a double-pulse test principle, a cross thermal coupling model and a power loss model are established; a two-dimensional coupling thermal resistance network model is created by using a thermosensitive parameter method to extract transient thermal impedance parameters, and a cross thermal coupling model is created ; iGBT switching characteristics are tested based on a double-pulse test principle, power loss model parameters are obtained, and a power loss model is built; and the IGBT thermoelectric couplingmodel is coupled based on the cross thermal coupling model and the power loss model, and estimating the IGBT junction temperature. The reliability of IGBT of the inverter is improved, the service life of the IGBT of the inverter is prolonged, the defects that thermosensitive parameters are inapplicable under the condition of large current and a temperature rise curve is not easy to measure are overcome, the solving process is simplified, an offline model is established, and the calculation speed is high.

An A / D converting device comprises; a plurality of A / D converters connected in parallel with each other, for carrying out a converting operation a plurality of numbers of times, in which an analog signal is converted into a digital data, a selecting circuit for selecting each A / D converter from the plurality of A / D converters at each sampling timing during the converting operation to sample the converted digital data, a selecting circuit controlling unit for controlling the selecting circuit so that when one A / D converter is selected at one sampling timing during the Nth converting operation, another A / D converter is selected at the one sampling timing during the (N+1)th converting operation, an adding circuit for integrating the digital data sampled at the one sampling timing during each converting operation, and a processing unit for processing the integrated digital data.

The invention relates to a photoelectric trigger and test system of a multimode optical fiber. It comprises a photoelectric trigger unit and a photoelectric test unit. The photoelectric trigger unit comprises: a trigger logic module, AB phase, BC phase, CA phase optical driving module and optical fiber. The photoelectric test unit comprises: six valve test module, AB+íóAB-íóBC+íóBC-íóCA+íóCA- optical receiving module and optical fiber. The photoelectric trigger unit and the photoelectric test unit have auto encoding optical pulse trigger transistor; the optical pulse feedback intelligently test the transistor running condition, the electric trigger pulse test and the PT off test and the master-slave mode distribution serial communication of the upper position machine.

In order to improve a measuring precision in case of measuring properties of the optical fiber to be measured, in accordance with returned lights which have wavelengths different from each other, detection is carried out with respect to the returned lights of the wavelengths different from each other, at a timing based on difference of propagation rates between the returned lights in the optical fiber to be measured, and error between the returning points is compensated with respect to each returned light, in the optical pulse testing device for inputting the optical pulse to the optical fiber to be measured, to detect returned lights which have wavelengths different from each other and which are returned back from passing points in the optical fiber to be measured, respectively, in order to measure the properties of the optical fiber to be measured, in accordance with detection results of the returned lights.

The invention provides an FPGA-based addition carry chain delay measurement method and system. The measurement method comprises steps: pulse test signals trigger the carry chain of a multi-bit adder,and according to the change condition of the current pulse test signals, the operation position value of the carry chain is acquired; with the clock cycle for generating the pulse test signals as an interval, the pulse test signals are translated sequentially, and after each time of pulse test signal translation, the operation position value can be triggered and acquired again until the operationposition values corresponding to all operation positions in the carry chain are acquired; and the relationship data between each operation position value of the carry chain and the corresponding position of each pulse test signal are acquired, and according to the relationship data, the delay time at each operation position of the carry chain is obtained. The delay time between different carry chains can be measured in real time, influences of temperature and voltage fluctuations can be avoided, and FPGA-based TDC module high-precision timing can be realized.

The invention discloses the pulse test circuit and the method of a flying capacitor three-level DCDC power component. The test circuit comprises a three-level power module, an adjustable direct current source, a discharge branch and a freewheeling inductor. The three-level power module comprises a supporting capacitor, a flying capacitor, an absorbing capacitor, and first to fourth IGBTs which areconnected in series. Each IGBT is connected with a voltage equalizing resistor and a reverse freewheeling diode in parallel. The adjustable direct current source and the discharge branch are connected in parallel with the supporting capacitor, the absorbing capacitor and a switching conversion circuit. When the three-level power module is operated in a Buck work mode, the freewheeling inductor isconnected between the third IGBT and the fourth IGBT in parallel. When the three-level power module is operated in a Boost work mode, the freewheeling inductor is connected between the first IGBT andthe second IGBT which are connected in series in parallel. In the invention, through controlling different switch conversion modes, each IGBT is subjected to a turn-on-turn-off-turn-on-turn-off process, and the ability of the power component to bear overcurrent and turn-on and turn-off characteristics are examined. The stray inductance of a converter circuit and a caused overvoltage condition areanalyzed and a system design is improved.

An integrated circuit device performs a delay test using scan path technique, including a pulse generator circuit generating a delay test clock pulse of a number according to an input pulse number control signal; and a scan path test circuit tested with the delay test clock pulse.

The invention relates to a device and method for utilizing plasma generated by an electric propeller to induce the charge-discharge effect, and belongs to the field of testing. The device for utilizing the plasma generated by the electric propeller to induce the charge-discharge effect comprises an electronic gun, an ion engine, a neutralizer, a first non-contact surface potential probe, a first potentiometer, a discharge pulse test probe, an oscilloscope, a specimen stage, material samples, a vacuum-pumping system, an insulation pad, an insulation supporting frame, a second non-contact surface potential probe, a second potentiometer and a vacuum chamber. The method for utilizing the plasma generated by the electric propeller to induce the charge-discharge effect comprises the steps that a space electrification environment is simulated by electron and the plasma generated by the electronic gun and the electric propeller, charge accumulates on the surfaces of the material samples under comprehensive irradiation of the electron and the plasma, the surface electrification effect is generated, a non-contact surface potential tester is utilized to test potential of the material samples, a discharge pulse tester is utilized to obtain discharge pulses of the material samples, and therefore a test for utilizing the plasma generated by the electric propeller to induce the charge-discharge effect is achieved.

The invention discloses an automobile radiator pressure pulse test platform comprising a hydraulic pump station, a high temperature oil pump station, a test controller, an upper computer and a test platform body, wherein the test platform body comprises a hydraulic loading device and a high temperature oil loading device; the hydraulic pump station is connected with the hydraulic loading device to form a hydraulic loading mechanism; and the high temperature oil pump station is connected with the high temperature oil loading device to form a high temperature oil loading mechanism. With the adoption of the automobile radiator pressure pulse test platform, a fatigue performance test at the room temperature can be carried out on a radiator test piece, and a simulated condition fatigue test at high temperature can be carried out on radiators at the same time by additionally installing a heating device and utilizing servo hydraulic cylinders and drive hydraulic cylinders to realize single cylinder loading and multiple cylinder loading to the test piece. The automobile radiator pressure pulse test platform can be used for the fatigue test of the radiator test piece and can be also used for the fatigue test of parts such as an automobile heat exchanger, and function diversification is realized.

The invention provides a test device for testing the direct current and even harmonic influence quantity of an electric energy meter. The test device is characterized by comprising the electric energy meter, an electric energy meter calibrating device for testing the electric energy metering precision of the electric energy meter and a direct-current current source for outputting direct-current current from a current loop of the electric energy meter, wherein a voltage loop and the current loop of the electric energy meter are connected with a voltage loop and a current loop of the electric energy meter calibrating device, the electric energy pulse output of the electric energy meter is connected to the electric energy pulse test input end of the electric energy meter calibrating device, the output positive end of the direct-current current source is connected to the current leading-out wire end of the current loop of the electric energy meter, the output negative end of the direct-current current source is connected to the current incoming wire end of the current loop of the electric energy meter, and the test of the direct current and even harmonic influence quantity of the electric energy meter can be finished without dividing the current test loop into two current branches. Two diodes and one balanced impeder in the current test loop are omitted.

The invention discloses a method for extracting stray parameters of a laminated bus bar based on frequency characteristics of a SiC MOSFET. The method comprises the following steps of firstly settingup a SiC MOSFET double-pulse test platform, and externally connecting the section under test of the laminated bus bar to the test platform; connecting multiple sets of additional capacitors in parallel at both ends of the SiC MOSFET, using the frequency information of oscillation in the off-voltage waveform of the SiC MOSFET before and after the additional capacitors are connected in parallel to obtain the resonance angular frequencies of multiple sets of equivalent circuit models, and further calculating the stray inductance and parasitic capacitance of the laminated bus bar to achieve the extraction of stray parameters of the laminated bus bar. The invention utilizes the high switching speed characteristics of the SiC MOSFET to excite obvious off-voltage oscillations. Compared with the traditional indirect measurement method, the measurement deviation caused by human factors is reduced. In addition, the invention can measure the stray inductance and parasitic capacitance in any section of the laminated bus bar, and the measurement is more flexible and comprehensive.

The invention relates to a high-pressure flexible tube pulse test bench, and also relates to a pressurizer which is specially used in the high-pressure flexible tube pulse test bench. The purpose of the invention is to provide a pulse test bench which can really imitate a real fluid and can realize a sine wave and a high frequency. A technical scheme for realizing the purpose of the invention is characterized in that: the pulse test bench comprises an electric control cabinet, a cold liquid storage device, a cold liquid pumping device, an energy storage device, a conversion valve and a pressurizer; hydraulic oil which is pumped from the cold liquid storage device to the energy storage device by the cold liquid pumping device enters the pressurizer through the conversion valve; and the hydraulic oil which is pressurized is accessed to a pulse test port. The pulse test bench is characterized in that: the pulse test bench which is between a primary energy storage device and the conversion valve is connected with a secondary energy storage device through a flexible tube, and the conversion valve is a servo flow valve; the cylindrical oil is mixed with a heated liquid from a heated liquid pumping device before the outlet end of the pulse test port; the oil return port of the pressurizer is connected to the cold liquid storage device; and the electric control cabinet controls the opening and the closure of all valves according to program requirements.

The invention provides a method for obtaining engineering machinery tyre vertical characteristic parameters based on a pulse test. The method includes the steps that by building a tyre-road surface coupling three-dimensional finite element model and pulse working condition virtual dynamic simulation, the tyre center point vertical acceleration corresponding to multiple sets of estimation material parameters is obtained; secondly, data are obtained through a real vehicle road pulse test, and the material parameters of all components of a tyre are distinguished out through a neural network; finally, a vertical rigidity damping parameter of an oversized tyre is obtained through a vertical static load test and a free vibration attenuation test based on a virtual test rig. According to the method, a simulation method is combined with the real vehicle test, a tyre acceleration feature curve is obtained, accordingly the tyre vertical rigidity damping parameter is obtained, restraints of the tyre size and load are avoided, a bench test is not needed, and test cost is low; the obtained tyre material parameters are more close to reality compared with component material parameters measured by a separated material performance test; the method is suitable for obtaining mechanical feature parameters of the oversized tyre.

The invention discloses a junction temperature test method of an AlGaN / GaN high electron mobility transistor and mainly solves a problem of the relatively low measured junction temperature existing ina method in the prior art. The method comprises steps that a pulse test method is utilized to test schottky positive characteristics of a device, the change relationship between gate source resistance RS0 and Schottky series resistance RT0 along with the temperature is extracted, and the change relationship of Schottky contact resistance RB0 along with the temperature is acquired as a calibrationcurve through combining the above two factors; secondly, a bias point is selected under the room temperature condition, the pulse test method is utilized to test the Schottky forward characteristicsof the device, Schottky series resistance RT is further extracted, output characteristics of a detected device are measured, gate source resistance RS is extracted, the change relationship of Schottkycontact resistance RB under different powers is acquired, through comparing with a calibration curve, the device junction temperature is extracted. The method is advantaged in that accuracy of the junction temperature test is improved, the measurement error is reduced, and the method can be used for measurement and analysis of high electron mobility transistor devices.

An optical pulse testing apparatus incorporating an optical pulse generator composed of low cost components. The optical pulse testing apparatus comprises: a ring optical path including an optical fiber 30 with a rare earth element added to; an excitation light source 32 which enters excitation optical pulses into the optical fiber 30; an optical branching filter 38 for branching the circulating optical pulses circulating through the ring optical path to emit output optical pulses; and a photodetector 40 for detecting the circulating optical pulses circulating through the ring optical path to obtain signals indicative of a light intensity and a generation timing of the circulating optical pulses. Thus, the optical pulse generator, and the optical pulse testing apparatus and method using the optical pulse generator require no expensive optical parts and complicated device control.

Methods and apparatus are provided for testing a magnetoresistive random access memory (MRAM). A magnetoresistive tunnel junction (MTJ) has a first terminal, a second terminal, and a third terminal. A source measuring unit is coupled to a first terminal of a MTJ to provide DC biasing. A current preamp has an input coupled to a third terminal of the MTJ for receiving current corresponding to a resistance of the MTJ. A pulse generator is AC coupled to the MTJ for programming the MTJ. A method of insitu testing a MTJ in a manufacturing environment uses a probe station coupled to the MTJ. A probe station couples to the MTJ. The MTJ is DC biased for generating a current corresponding to the logic level stored in the MTJ. A pulse for programming the MTJ is AC coupled to the MTJ.

Calibration method for calibrating transient behaviour of a TLP test system. The system comprises a TLP generator, probe needles, nominally impedance matched transmission lines and measurement equipment, connected between the transmission lines and the TLP generator, for detecting transient behaviour of a device under test by simultaneously capturing voltage and current waveforms as a result of generated pulses. The calibration method comprises (a) applying the TLP test system on an open and capturing first voltage and current waveforms; (b) applying the TLP test system on a calibration element having a known finite impedance and a known transient response and capturing second voltage and current waveforms; (c) transforming the captured first and second current and voltage waveforms to the frequency domain, and (d) determining calibration data for the transient behaviour of the TLP test system on the basis of the transformed first and second voltage and current waveforms.

The invention relates to hydraulic technology, in particular to a constant temperature controlled hydraulic hose pulse test bench, which includes an electric control system, a pulse loading system, an oil replenishment system, and a hydraulic hose connection valve block to be tested. The hydraulic hose under test communicates with the high-temperature fuel tank of the oil supply system through the hydraulic control check valve, the hydraulic control check valve opens and closes according to the oil temperature in the tested hose, and the B port of the booster cylinder of the pulse loading system directly connects with the main fuel tank . The oil temperature control adopts the closed-loop control method of the hydraulic control check valve combined with the temperature sensor, which ensures the stability of the oil temperature during the pulse test, and the hydraulic control check valve only increases the oil temperature beyond the test requirements after multiple pulse impacts It is opened from time to time, which reduces the frequency of opening and closing and improves its service life. The test bench has the characteristics of simple structure, low energy consumption, reliable performance and long service life.

The invention belongs to the technical field of rubber detection, and particularly relates to a pressure pulse test hydraulic pressure system for rubber hose test. The system is characterized by comprising a fuel tank, a hydraulic pressure pulse generating device and a fuel feeding device. A fuel supply port and a fuel return port of the fuel tank are respectively connected with a fuel supply device and a fuel return port the hydraulic pulse generating device; a fuel feeding tube inlet of the fuel feeding device is connected to the fuel supply port of the fuel tank; the hydraulic pressure pulse generating device is directly connected with a test piece; and the fuel feeding tube outlet of the fuel feeding device is connected to the test piece. The invention has the beneficial effects of further improvement of the performance and stability of high-voltage pulse, more accurate test results, improved safety of rubber hose, and simplified system structure, and has important significance to the technical development of domestic hydraulic pressure pulse test bench.

The invention relates to an active MOSFET voltage clamping circuit, a clamping method and a double-pulse test circuit. The voltage clamping circuit comprises a device under test, a drain electrode ofthe device under test is connected with a drain electrode of an active clamping tube, a source electrode of the active clamping tube is connected with a clamping end X node, a source electrode of thedevice under test is connected with a Y node of a clamping end, a capacitor C1, a resistor R1 and a Zener diode D2 are connected in parallel between the X node and the Y node by a diode D1. A capacitor C2, a resistor Rg and a power supply (Vcc) are connected in parallel between a grid electrode of the active clamping tube and the common end of the source electrode of the device under test and theY node of the clamping end; a fixed gate bias (Vcc) is applied to the grid electrode of the active clamping tube, when the device under test is in an off state, a voltage VXY between the clamping endnode X and the clamping end node Y is clamped near Vcc-VTH and MT, and when the device under test is in an on state, the voltage VXY follows a conduction voltage VDSON.

The invention belongs to the field of fluid mechanical experiments, and relates to a performance test device under a swing condition of a marine pump. The performance test device mainly comprises a swing table, the marine pump, a hydrophone, a pressure sensor, an acceleration sensor, a data acquisition instrument and a variable-frequency control cabinet, wherein the swing table comprises a swing frame, a drive motor, a speed reducer, a fly wheel, a bracket, a supporting plate, a positioning scale plate and a swing table base; the marine pump is fixed to the swing table through a foot bolt; the swing table is fixed to a cement base; and the variable-frequency control cabinet is utilized to control the drive motor, so that the swing table can be driven to operate. The performance test device can carry out external characteristic, vibration, noise and pressure pulse test under multiple working conditions, multiple angles of inclination and multiple swing periods and amplitudes of the marine pump. The performance test device is simple in structure, is convenient to mount, is wide in scope of application, is easy to operate, and is relatively high in precision, can carry out synchronous test for external characteristics, vibrations, noises and pressure pulse signals, so that effective means are provided for carrying out performance test under the inclination and swing conditions of the marine pump.

The invention relates to a vehicle high-pressure power steering rubber tube and a preparation method thereof. The rubber pipe is specifically in a five-layer structure, wherein the inner layer is ECO (Epichlorohydrin) or AEM (Alpha-Ethyl Mescaline) rubber with the thickness of 0.5-4 mm; the middle layer is NBR (Nitrile-Butadiene Rubber) with the thickness of 0.1-2 mm; the outer layer is AEM rubber with the thickness of 0.2-3mm; and nylon between the inner layer and the middle layer and between the outer layer and the middle layer is used as a reinforcing layer. The invention can ensure that the rubber pipe can reach the burst pressure of above 54 MPa, the inner rubber can resist hydraulic oil by adopting ECO or AEM, the outer rubber can resist the high temperature of 150 DEG C by adopting AEM, and the mode of water-coated distributed vulcanization is adopted, thereby the adhesive force exceeding 2.5 N / mm of the standard requirement is greatly increased; and the appearance is beautiful and regular cloth marks so that the rubber pipe can not have the phenomenon of ugly line ridges. The rubber pipe is subjected to a pulse test after being buckled so that the rubber pipe is not broken at 225000 times under the conditions that the pressure is 0-10.3 MPa, the inside and the outside temperatures are 135 DEG C, and the inner part of the rubber pipe is filled with circulated hydraulic oil.

The invention discloses an earth fault positioning method for an electric power circuit, and particularly relates to the technical field of electric power system fault positioning. The method specifically comprises the following steps that: S1: inquiring and obtaining the transformer substation position of a power supply circuit, and utilizing a discharging rod to enable each phase line of a cable to fully discharge to the earth; S2: connecting the plug of a low-voltage pulse test line with a low-voltage pulse socket of a test device, and connecting two clamp forceps of the test line with two fault phase lines; and S3: according to the type of the cable, setting proper wave velocity, and through the low-voltage pulse test line, injecting a low-voltage pulse into a test cable. A fault distance and fault positioning obtained by the method can be more accurate, a deviation with a practical fault point can be lowered to improve fault positioning accuracy, the property of the fault can be judged through the identification of the polarity of a reflected pulse, the workload of a user when electric power circuit fault detection is carried out can be lowered, and in addition, the method is simple in operation and high in accuracy.