316 results about "Ground impedance" patented technology

A high-gain and low-noise low noise amplifier (LNA) includes a differential amplifier, a pre-amplifier and an impedance matching network. The differential amplifier includes a first input end and a second input end coupled to a grounded impedance. The pre-amplifier includes an input end and an output end. The impedance matching network is coupled between the first input end of the differential amplifier and the output end of the pre-amplifier for matching an input impedance of the differential amplifier with an output impedance of the pre-amplifier. The present invention provides a LNA structure with low noise, high gain and easy design.

The invention discloses a battery panel ground insulation impedance detection circuit which comprises a partial pressure subcircuit and a voltage detection unit (11), wherein the partial pressure subcircuit is used for connecting between a positive electrode (PV+) of a battery panel and a negative electrode (PV-) of the battery panel. The partial pressure subcircuit comprises a first resistor (R1), a fourth resistor (R4) and a second control switch, the first resistor (R1), the fourth resistor (R4) and the second control switch are connected in series, the second control switch enables a to-be-detected electrode to be connected or disconnected with planet earth (PE) through opening and closing states, and forms a plurality of various connection combinations according to connection between the to-be-detected electrode and the planet earth, and the voltage detection unit (11) is used for sequentially outputting a plurality of sampling voltages according to each various connection combination. The partial pressure subcircuit is formed by respectively connecting resistors on a positive electrode impedance and a negative electrode impedance, the various connection combinations are formed under the control of the second control switch, the plurality of sampling voltages are output, positive electrode ground insulation impedance and negative electrode ground insulation impedance can be calculated, and the problem that when one electrode of a battery is infinite in ground impedance, ground impedance of the other electrode of the battery can not be calculated.

The invention provides an impact grounding impedance measuring system which comprises a high-voltage direct current source, a high-voltage pulse capacitor, a discharging loop, a high-voltage charging switch, a high-voltage discharging switch, a resistance current divider, a water resistance voltage divider, a high-voltage pulse source control table, a digital oscilloscope and an optical fiber signal transmitting system, wherein the resistance current divider is connected with the high-voltage pulse capacitor and the discharging loop in series; the water resistance voltage divider is connected with a reference grounding electrode of the discharging loop; the optical fiber signal transmitting system comprises an optical transmitter, an optical fiber and an optical receiver; the voltage divider and the current divider are respectively connected with the digital oscilloscope through the optical fiber signal transmitting system; and the high-voltage discharging switch is a motion ball gap switch. The invention has the advantages of compact structure, small volume, convenient carrying, simple operation, accurate and stable measuring value, reduction of electromagnetic interference and reduction of measuring error.

A pile foundation tower footing impedance measuring device and method thereof, relate to an overhead transmission line tower footing impedance measuring device and method thereof. The device comprises an auxiliary electrode, a high accuracy flexible Roche coil current sensor, a tower footing impedance measuring device or the like. The footing impedance of the pile foundation tower is measured by program. The invention has features: simple structure, low cost, easy operation, wide measuring current range, strong antijamming capability, high measuring accuracy and low measuring cost, therefore the invention can be widely used for measuring the overhead transmission line tower footing impedance, especially for measuring the tower footing impedance without down lead, incapable or inconvenient of unfastening the down lead, avoiding unfastening the down lead.

The invention provides a frequency sweeping test method for measuring the power frequency ground resistance of a grounding device and a test instrument for the frequency sweeping test method, which are used for solving the problems that in the conventional measurement, wires are inconveniently laid, measurement is interfered and the like. The measuring method comprises the following steps of: arranging a voltage electrode, a current electrode and a lead according to a preset ground resistance test way; selecting a frequency with a small interference signal as a test frequency; measuring ground impedance at the selected test frequency; and computing the power frequency ground resistance according to the measured ground impedance. The adopted test instrument comprises a variable-frequency alternating current power supply, a current sensor, a voltage divider, an isolating transformer, a signal acquisition device, an analog/digital (A/D) convertor and a portable personal computer (PC). The frequency sweeping test method for measuring the power frequency ground resistance of the grounding device and the test instrument for the frequency sweeping test method can effectively avoid each interference frequency and acquire a reliable test result.

The invention relates to a method and a system for evaluating a corrosion state of a transformer substation grounding grid. The system comprises a field impact current generation module, a transient current and voltage recording module of all grounding down leads, an impact grounding impedance calculating and impact response curve drawing module, a testing result storing and recording module and a grounding grid state evaluation and analysis module, wherein the field impact current generation module is used for generating impact current; the transient current and voltage recording module of all the grounding down leads is used for collecting the impact current, transient response voltage waveforms of input grounding down leads and impact response voltage waveforms of output grounding down leads in different positions; the impact grounding impedance calculating and impact response curve drawing module is used for processing current and voltage data to obtain the grounding grid impact impedance and an impact response curve of different positions; the grounding grid state evaluation and analysis module is used for evaluating the corrosion state of the transformer substation grounding grid. Compared with the prior art, the method and the system, disclosed by the invention, have the advantages of simplicity, accuracy and capacity of being not limited by a field running condition.

The invention provides a verification method and an experimental device for grid impedance recognition. The experimental device comprises a voltage source inverter (10), a grid impedance unit (20) and a grid impedance recognition unit (30). The specific operation process for verifying grid impedance recognition by the experimental device comprises the following steps: a disturbing signal injection unit (301) injects disturbing signals into an inverter control system, current response signals iga, igb and igc and voltage response signals uga, ugb and ugc of a PCC (point of common coupling) are acquired respectively by a current sensor Hig and a voltage sensor Hug on a grid-connected side, acquired signals are input into a grid impedance calculation unit (305), and grid impedance is obtained through calculation. A grid impedance recognition method can be verified accurately and reliably by the experimental device, and adverse effect on power quality is avoided.

The invention discloses a method for measuring the ground impedance of a large grounding grid, and relates to the technical field of the measurement of grounding characteristics of large grounding grids such as grounding grids in power stations or transformer substations. Based on the phase difference measurement of a reference vector of test current, module values and phase difference of an outlet overhead ground wire and a power cable outer sheath of a power station or a transformer substation to shunts of the test current are obtained; and through a vector of each shunt and calculation, the actual diffused current vector of the test current passing the grounding grid is accurately solved, so that the ground impedance of the grounding grid is accurately measured. According to the conventional method for measuring the ground impedance of the grounding grid under the condition that the running power station or transformer substation is provided with an outlet ground wire, the shunts of the overhead ground wire and the cable outer sheath are not measured, or the vector of each shunt is only measured, the phase difference from the vector of the test current is not measured, a result that the shunt module value is subtracted from the test current is only obtained, and the simple treatment method is changed. The accuracy for measuring the ground impedance is improved, serious systematic errors are avoided, and the state of the grounding grid is accurately evaluated.

The invention discloses a six-phase-sequence-impedance-based distance protection measurement method of double-circuit lines on the same pole. Two circuit lines are viewed as a whole body. Six single-phase ground impedance measuring elements, six interphase impedance measuring elements and six interline impedance measuring elements are formed by three voltages and six currents in the two circuit lines on the side of the whole body. Totally eighteen measuring impedances are formed. The measurement equation of the distance protection measuring method is as shown as the accompanying drawing, wherein UIAu, UIBu, UICu, UIIAu, UIIBu and UIICu respectively denote voltage drops of A, B and C on the unit length of a circuit line I and a circuit line II, ZS denotes line self-impedance, Zp denotes interphase mutual impedance of the same line, ZM denotes interline mutual impedance, L denotes line length, iIA, iIB, iIC, iIIA, iIIB and iIIC respectively denote A, B and C phase currents, and delta denotes interline zero-sequence mutual inductance compensation coefficient.

The invention provides a method for measuring impact earthing impedance of an electric transmission overhead line structure earthing device with a lightning conductor. According to the method, a lightning conductor or an overhead ground wire of other type are erected on an electric transmission overhead line structure; the earthing device of the overhead line structure is connected with the overhead line structure or the lightning conductor or the overhead ground wire through a downlead; the downlead is connected with the earthing device through bolts; the downlead and the earthing device are electrically connected and can be detached. According to the method, the impact earthing impedance of the electric transmission overhead line structure earthing electrode can be directly measured, errors in measurement caused by uneven soil structure and measuring electrode position deviation are avoided, the wiring manner is simpler and the measurement result is more accurate; through the adoption of the methods such as increasing the amplitude value of the output voltage waveform or the current waveform of the power supply or multiplying spark discharging coefficient, the impact earthing impedance of the electric transmission overhead line structure earthing device after the spark discharge can be further gained.

During operation, the DC converter and a DC battery charger controller in a charger circuit transitions from a first error signal to a second error signal for use in charging a battery, wherein the first error signal and the second error signal, respectively, correspond to feedback sources in a plurality of feedback sources with a plurality of feedback sources. Then, the DC converter and a DC battery charger controller selects a gain and an impedance to ground of a damping circuit based on the selected second error signal, where the damping circuit applies the gain and the impedance to ground to the second error signal. Moreover, the DC converter and a DC battery charger controller selects one or more clamping voltages of a voltage-clamping circuit based on the selected second error signal, where the voltage-clamping circuit applies the one or more clamping voltages to an output from the damping circuit.

The invention discloses a power leakage protection method which comprises the following steps: S1) obtaining the instantaneous parameter of the remaining current from a main circuit; S2) according to the instantaneous parameter, calculating the phase angle of the remaining current; determining whether the phase angle jumps from the previous cycle or not; S3) if the phase angle jumps from the previous cycle, determining whether the phase angle is within the capacitive phase angle range or within the resistive phase angle range; if the phase angle is within the capacitive phase angle range, returning to the step S1; if the phase angle is within the resistive phase angle range, then proceed to step 4; S4) determining whether grounding impedance is reduced or not in a preset duration; S5) if the grounding impedance is reduced, starting protection to the remaining current; if the grounding impedance stays unchanged, then executing the step 6; and S6) determining whether the sudden change amount of the remaining current exceeds the set value or not; if the answer is yes, starting protection to the remaining current; and if the answer is no, returning to the step 1. In addition, the invention further discloses a power leakage protection system and a remaining current protection breaker which could achieve the same technical effects as the above.

The invention discloses a large earth screen shunt vector quantity measurement method based on wireless transmission, and relates to the technical field of grounding character measurement of large grounding grid of substations, electric power plants, and the like. When grounding impedance measurement of running power station and substation grounding grids is carried out, the wireless transmission technique is adopted, wireless transmission phase information is tested between current injection points and outgoing line frameworks and between the current injection points and outgoing line cable shunt measuring points, a phase between each shunt vector quantity and each test current vector quantity is obtained in real time, a pilot frequency shunted vector quantity flowing through metal frameworks and outgoing line cable outer sheaths is obtained through mathematical treatment, the metal frameworks and the outgoing line cable outer sheaths are connected with outgoing line overhead ground wires, and the pilot frequency shunted vector quantity comprises the size of a module value and a phase difference. The measurement method solves the problem that a shunt vector quantity cannot be measured on site in the past, and provides technical support for refined calculation of shunt coefficients of the running substation overhead ground wires and the cable outer sheaths.

The invention discloses a method for measuring impact grounding impedance on a site based on large impact current. The method comprises the following steps: wiring a current electrode, wiring an impact current generator, wiring an injection point voltage signal measuring wire, and wiring an injection point current signal measuring wire. By the method provided by the invention, a dispersing property of the impact current in soil can be really reflected, actual measurement on an impact grounding property of impedance under the large impact current can be achieved, the impact grounding impedance can be accurately measured, an impact property of a grounding body can be easily mastered, design, construction and running of lightning protection engineering can be instructed and inspected, the integral safety and the integral reliability of the engineering are improved, and the operability is good.

The invention provides a thin film transistor liquid crystal display which comprises a first polarizer, an array substrate, a colored filter substrate, a second polarizer and conductive glue. The array substrate is located above the first polarizer, the colored filter substrate is opposite to the array substrate, a liquid crystal layer is clamped between the colored filter substrate and the array substrate, the second polarizer is located above the colored filter substrate, the side edge of the second polarizer is cut into a special shape, and the conductive glue is arranged between the second polarizer and the colored filter substrate in a coating mode. The side edge of the second polarizer, the side edge of the conductive glue and the side edge of the colored filter substrate further comprise silver glue which is electrically coupled with the second polarizer. Compared with the prior art, the side edge of the second polarizer is cut into the special shape such as a corrugated shape, so that the contact area of the conductive silver glue and the second polarizer is increased along with increasing of the length of a curve on the side edge of the second polarizer, smaller grounded impedance is obtained, and a more reliable electrostatic discharge path is formed.

The invention discloses a neutral point grounding impedance device of a transformer and a multipurpose direct current magnetic bias protection method of the impedance device. The impedance device is arranged between neutral points of all main transformers in a transformer substation and the ground, and comprises an impedor Z, a lightning arrester A and a by-pass switch K; one end of the impedor is connected with a neutral point of the transformer; and the other end of the impedor is grounded. The impedance device has the benefits that the device is mainly used for the transformer substation; the neutral points of the main transformers in the transformer substation are grounded by the impedance device; direct current magnetic bias current can be effectively inhibited; the short-circuit resistance capacity of the transformer is improved; and damage of ground overvoltage to insulation of the neutral point of the transformer is avoided.

The invention provides a method for measuring a strength index of interaction between converter stations of a multi-feed direct current system. The method comprises the following steps that (1)a multi-feed alternating current and direct current power grid receiving end system is taken as a research focus, direct current converter stations to be researched are determined, and it is assumed that the number of the direct current converter stations to be researched is N, and the direct current converter stations to be researched have three phases of A, B and C; (2) electromechanical transient simulation calculation is conducted on the power grid with electromechanical transient simulation software, a single-phase grounded short circuit with certain resistance is arranged at the phase A at a converter bus i, i=1, 2, ...N, the change of the voltage of the phase A at the converter bus i is observed, the grounded resistance of the short circuit is adjusted constantly, the voltage of the phase A at the converter bus i drops by 1% after the short circuit, the variation delta UAj of the voltage of the phase A at the converter bus j is recorded, j=1, 2, ..., i-1, i+1, ...N, and the calculation of the phase B and the calculation of the phase C are identical with that of the phase A; (3) a single-phase multi-feed interaction factor SMIIFij between the converter station i and the converter station j is calculated. By means of the method, references are provided for evaluating the strength of the interaction between all converter stations in the multi-feed direct current system in asymmetrical faults.

The invention relates to a method and a system for eliminating mutual inductance between leads in ground resistance measurement. By synchronously measuring measurement voltage and current waveform and analyzing the amplitude ratio of voltage to current and the phase angle difference between the voltage and the current, ground impedance under a given frequency and an impedance angle of the ground impedance can be obtained, the mutual inductance between the leads of a voltage electrode and a current electrode in measurement is obtained by calculation, and a true value of the ground impedance can be obtained by subtracting a part generated by the mutual inductance from the ground impedance on the basis. According to a testing method, the influence caused by various background interference signals is effectively avoided, and an accurate measurement result can be obtained even if the output current is very low. According to the method for eliminating the mutual inductance between the leads in the ground resistance measurement, the test pay-off workload is small, and a voltage lead and a current lead can be paved abreast. Test data can be acquired and analyzed under the automatic control of a portable system without manual intervention, and the characteristic of simplicity in operation is achieved. The data are directly analyzed on the scene by virtue of the portable system, the visualization is high, and industrial frequency ground resistance can be immediately given.

The invention discloses a device for grounding protection and fault monitoring. According to the device for grounding protection and fault monitoring, the voltage to ground of the positive electrode and the voltage to ground of the negative electrode of a monopole grounding system are sampled in real time through a fault monitoring device and are converted into corresponding ground impedance values, when the continuouly cumulative frequency that the ground impedance value of a certain electrode of the monopole grounding system is smaller than a preset impedance value exceeds a preset frequency, it is judged that faulty grounding points exist on the electrode, and an alarm is given. According to the device for grounding protection and fault monitoring, online detection of the two electrodes of the monopole grounding system can be conducted in real time when the system operates, detection can be conducted even when the system is not stopped, and the problem of low safety performance in the prior art is solved.

The invention discloses a small-current lightning impulse grounding impedance testing method and device. The device comprises an impulse signal generation unit, an impulse signal sampling unit, a signal processing unit and a power supply unit. The testing method comprises the steps that a small-current impulse signal is generated through the impulse signal generation unit, injected into a grounding device and flows into the ground through the grounding device in a scattered mode; the impulse signal sampling unit collects an impulse current and impulse voltage passing through the grounding device; then, the impulse current and impulse voltage are compared through the signal processing unit, and an impulse current peak Im and an impulse voltage peak Um are obtained; finally, operation is performed on Im and Um in combination with the engineering definition of impulse grounding impedance, and then an impulse grounding resistance value is obtained. The device can output various impulse current signals with the amplitude capable of reaching the Ampere level so that impulse characteristics of the grounding device under the action of different types of lightning can be effectively simulated and analyzed. Besides, the device has the advantages of being small in size, portable in structure, high in safety and good in practicability, thereby being high in applicability.

The invention discloses earth impedance detecting circuit and method of a photovoltaic inverter. The earth impedance detecting method of the photovoltaic inverter comprises the following steps: respectively inserting a ground connecting resistor between positive electrode of every path of a solar cell panel and the ground, inserting a resistor R 4 and a resistor R 5 in series connection between public negative electrode of every path of the solar cell panel and the ground; obtaining detection voltage of public end of the resistor R 4 and the resistor R 5; calculating positive electrode ground impedance or negative ground impedance of the solar cell pane according to detection voltage and equivalent circuit of the solar cell panel inserting photovoltaic inverter; comparing the positive electrode ground impedance or the negative ground impedance with preset threshold, sending out alarm information when the positive electrode ground impedance or negative ground impedance is smaller than the preset threshold. The earth impedance detecting circuit and method of the photovoltaic inverter have the advantages of being simple in structure, low in achievement cost, reliable, accurate in detection and the like.

An electrostatic capacitance detection circuit 10 comprises an AC voltage generator 11, an operational amplifier 14 of which non-inverting input terminal is connected to specific potential (a ground in this example), an impedance converter 16, a resistance (R1) 12 connected between the AC voltage generator 11 and an inverting input terminal of the operational amplifier 14, a resistance (R2) 13 connected between the inverting input terminal of the operational amplifier 14 and an output terminal of the impedance converter 16, and an impedance element (a capacitor) 15 connected between an output terminal of the operational amplifier 14 and an input terminal of the impedance converter 16. A capacitor to be detected 17 is connected between the input terminal of the impedance converter 16 and the specific potential.

The invention discloses a circuit single-phase earth fault impedance distance protection method based on additional impedance actual measurement correction. Additional impedance caused by transition resistance is calculated by means of protection for measured fault phase electricity amount, correction for a computed result of fault impedance of traditional earth impedance distance protection is carried out through the measured additional impedance, the fault impedance zrelay which reflects a real fault distance is obtained, a protection device judges whether a movement equation /zrelay-0.5*(zset1+zset2) /</0.5*(zset1-zset2) /is right, if the equation is right, the protection device sends out movement trip signals, and the zset1 and the zset 2 are respectively forward setting impedance and reverse setting impedance. According to the method, precise measurement for the additional impedance caused by the transition resistance is achieved, the correction for the computed result of the fault impedance of the traditional earth impedance distance protection is carried out through the measured additional impedance, the fault impedance which reflects the real fault distance is obtained, influences of the additional impedance caused by the transition resistance on impedance distance protection movement performance are eliminated, and the method is suitable for the power transmission circuit single-phase earth fault impedance distance protection.