1564 results about "Grounding resistance" patented technology

A high speed cable to carry signals according to the High-Definition Multimedia Interface and Universal Serial Bus 3.0 standards is disclosed. The cable includes a raw cable, having a conductive braid, a ground wire, signal lines; and two terminating assemblies at each end of the raw cable. The conductive braid is coupled to the ground wire in each of the terminating assemblies through a respective inductor to reduce the ground resistance of the cable, thus permitting construction of a thinner, lighter, and more flexible cable.

A permanently mounted AC powered control/display unit and a remote sensor for use in measuring ground resistance. The sensor is permanently mounted around the earth grounding cable. The control display unit generates a 1953 Hz, 5 Vac sine wave which is sent via a cable to a 100:1 ratio drive transformer in the remote sensor. The transformer induces a 0.05 Vac sine wave in the ground cable. The resulting current is detected by a 100:1 turns ratio sense transformer. The current is returned via the cable to the control display unit and converted to a voltage, filtered, amplified and rectified by a synchronous rectifier. The rectified voltage is again filtered and presented to an analog to digital converter. A microprocessor reads the output of the analog to digital converter and the ground resistance is computed by using Ohm's Law (R=E/I), the result being shown on a display.

In accordance with the present invention, a method is provided whereby the transient voltages presented at the input to a watt-hour meter are suppressed to prevent damage to the watt-hour meter and to the electronic devices that are powered through the watt-hour meter. In addition to transient voltage protection, the method of the present invention also provides monitoring of the earth ground resistance, voltage and current of the earth ground conductor associated with the watt-hour meter. As such, voltage transients are suppressed when presented at the watt-hour meter through the power line input, ground resistance of the earth ground conductor in continuously monitored and the current and voltage conditions existing on the ground conductor are continuously monitored. Visual and audible indicators are provided to indicate quality issues with the grounding system and the effectiveness of the surge suppressor/arrestor.

There is a ground-fault resistance measurement circuit which measures a ground-fault resistance between a conductive frame body of electrical equipment and a charge section insulated from the frame body. This ground-fault resistance measurement circuit includes: a capacity which is connected between the charge section and the frame body; a switch which opens and closes a connection path between the charge section and the capacity; a charging unit which charges the capacity to a predetermined voltage; a voltage measurement section which measures a charging voltage of the capacity; a discharge control section which connects the capacity and the charge section after the capacity is charged, and discharges the capacity; and a calculation section which calculates a resistance between the charge section and the frame body, based on a change in the charging voltage of the capacity.

Voltage-activated and accurate current sink, and method of providing same. In one aspect, a circuit for accurately sinking current includes a zener diode coupled to a power source at the cathode of the zener diode, and first and second transistors, where the first transistor has its collector coupled to the power source and its base coupled to the cathode of the zener diode, and the second transistor has its base coupled to the anode of the zener diode and its emitter coupled to ground. A resistor is coupled between the emitter of the first transistor and the collector of the second transistor.

The invention relates to a traveling wave analysis and recognition method for distinguishing lightning shielding failure from lightning counterattack of direct current transmission line. The lightning shielding failure of line is that lightning avoids the lightning shield line and directly strokes on the transmission line, while lightning counterattack of line is that lightning directly strokes on the lightning shield line or the tower. Because the earth resistance of tower exists, the potential on tower top suddenly increases and causes insulation flashover. The electromagnetic transient component generation mechanism of the high voltage direct current transmission line and the propagation path of lightning electromagnetic transient of the line in the lightning shielding failure are different from those in the lightning counterattack, the size and polarity of the initial surge voltage and the second surge voltage of the voltage transient signal exist significant difference. The traveling wave analysis and recognition method of the invention analyzes zero mode voltage using wavelet and distinguishes the lightning shielding failure and lightning counterattack failure according to the size and polarity of the initial surge voltage and the second surge voltage of the zero mode voltage in the traveling wave analysis and high-speed acquisition system of the protection zone. A lot of simulation results show that the method is reliable and effect. The physical concept of the invention is visible and clear, the method is easy to achieve and wide to use in the direct current system protector, also provides accurate initial data for researching lightning characteristics, analyzing lightning accident, discussing lightning protection countermeasure of transmission line and designing insulation coordination in the power system.

Wherein, with embed-meter method, applying split-core current transformer (PT) and split-core current transformer (CT) with same wire number as the tower ground wire to clamp all tower ground wires; or applying strip-shape PT and CT to enclose whole tower; filtering and analyzing the measured data to obtain the real and imaginary parts of fundamental wave component of voltage and current signals; calculating with special voltage-drop algorithm to obtain the target resistance. This invention improves efficiency, and reduces cost.

The invention discloses a ground fault fully compensated controllable voltage source output voltage computing method, comprising the steps of obtaining circuit ground capacitance, leakage resistance,fault ground resistance, arc suppression coil inductance, resistance and controllable voltage source internal resistance when a ground fault occurs; computing parallel impedance of a circuit ground parameter and a compensation inductance parameter according to the arc suppression coil inductance, the resistance, the leakage resistance and the circuit ground capacitance; and computing a controllable voltage source output voltage according to the fault ground resistance, the controllable voltage source internal resistance and the parallel impedance of the circuit ground parameter and the compensation inductance parameter. According to the method, in a voltage source access mode, the state problem that an arc suppression coil inductance parameter and the circuit ground capacitance approximateto power frequency resonance does not need to be taken into consideration; control is relatively easy; a fault current can be effectively compensated; and arc quenching is carried out on a fault point. According to the method, phase and amplitude of the output voltage are obtained through computing, the current at the fault point is quenched through control over the phase and amplitude of a controllable voltage source, and safe and stable operation of a power grid is ensured.

The invention relates to the technology of photovoltaic grid-connected inverter, in particular to an online detection method of insulating resistance to ground of a photovoltaic grid-connected inverter. The method comprises the following steps of: by sampling an output voltage VPV of a photovoltaic cell and enabling a switch S1 in a resistance switch circuit to be in opening or closing state, disconnecting or connecting a resistor R5 from or to an upper bridge arm, and then sampling a voltage signal of a dividing voltage output end of a lower bridge arm to obtain a voltage ratio equation of anode to ground of photovoltaic cell and cathode to ground of the photovoltaic cell, thereby online calculating a insulating resistance R+ of anode to ground of the photovoltaic cell and an insulating resistance R- of cathode to ground of the photovoltaic cell in real-time and accurately. The method has simple calculation process and high detecting precision; by adopting the method, the online and real-time detection of anode-to-ground resistance of the photovoltaic cell and the cathode-to-ground resistance of the photovoltaic cell is achieved, the photovoltaic grid-connected inverter is guaranteed to work safely and reliably.

An electrostatic-conducted epoxy-resin terrace coating and its coating process are disclosed. The coating consists of finish and primer, finish uses conductive short-staple slurry with excellent conductive and dispersing performances, and surface and volume resistances reach to 5*10(4)-1*10(6)omega, furthermore, finish utilizes composite accessory system with disperser, leveling agent, antifoaming agent and rheological agent; primer uses conductive graphite powder, and surface and volume resistances reach to 10(3)-10(4)omega. The process is carried out by pasting conductive copper foil at an interval 1m*2m, building an electrostatic dissipative leakage layer, connecting a grounding device by1000m2 with grounding resistance<4omega and composing complete electrostatic leakage system. It's simple, convenient and has excellent and long-acting electrostatic-conducting effect.

A single-phase-to-earth fault processing device for a neutral non-effectively grounded distribution network includes a split-phase arc quenching device connected between earth and a three-phase bus of the distribution network, and a controller with an input end connected with a single-phase-to-earth phase selection device of the distribution network. The split-phase arc quenching device includes a multiphase switching device which operates independently for each phase, and a fuse connected in series with the multiphase switching device. The controller is for controlling opening and closing of three single-phase switches, in the multiphase switching device. A single-phase-to-earth fault processing method firstly controls the split-phase arc quenching device to preprocess the fault. If the fault still exists, through a ground resistor a zero-sequence current is generated on a fault line. After delaying to wait for a line to isolate a fault section, a ground connection of the neutral is cut, to restore the distribution network.

Provided is a measuring method using a spark coefficient for correcting low-amplitude value impact resistance of a tower grounding device. A portable impulse current generator is used as a signal output source, a three-level measuring mode is adopted to arrange the grounding device, an UPS is used for supplying power to inject impulse currents from a grounding electrode, a spark coefficient alpha of soil where the grounding device located is calculated, and initial impulse grounding resistance Rc obtained through convolution calculation is corrected according to the spark coefficient alpha obtained through calculation. According to the measuring method using the spark coefficient for correcting the low-amplitude value impact resistance of the tower grounding device, standard impulse grounding resistance under lightning currents is obtained by adopting the convolution calculation and a spark coefficient modification method, the inductive effect of the grounding device and spark discharge of the soil can be taken into consideration effectively, the corrected impulse grounding resistance is more similar to practical situations when electric transmission lines are struck by lightning. The measuring method using the spark coefficient for correcting the low-amplitude value impact resistance of the tower grounding device solves the problems that only power frequency grounding resistance can be adopted to carry out approximate estimation and field measurement cannot be carried out in the prior art are solved.

The invention relates to an alternative current electric crosstalk and insulation fault monitoring line selection method of a direct current system. The direct current system is formed by an upper computer, a monitoring device, a sampling system and a current sensor. The alternative current electric crosstalk and insulation fault monitoring line selection method includes the steps of extracting a ripple crest value in the direct current system through extracting of an alternating component effective value, adopting the alternative current and direct current component separation digital filtering technology, the direct current leakage current detection technology, the recommend standard 485 (RS485) isolation communication technology and the fast fourier transform algorithm (FFT) conversion technology to monitor system bus over-the-ground alternative and direct current voltage and a ripple voltage peak value in real time to give an alarm, receiving loop leakage current information uploaded by a data collector, carrying out intelligent analysis through mode matching technology, calculating grounding resistance, carrying out artificial intelligence mode matching on feature status information of each loop and configured feature rules in the system, enabling the alternative current electric crosstalk faults, ripple voltage peak value monitoring data, grounding fault and insulation fault loop status information, loop information and the like which to be displayed on a liquid crystal display, assisting operation and maintenance workers to accurately know the current status to rapidly remove the faults.

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 discloses a lightning stroke characteristic assessment method which includes the following steps of: (1) determining a lightning stroke model; (2) determining a tower model and impulse grounding resistance; (3) determining an insulator model and flashover criteria of the insulator model; (4) selecting a line model and a matched load; (5) changing the neutral point grounding modes; (6) measuring zero sequence current values and neutral point potentials in different grounding modes. The lightning stroke characteristic assessment method has the advantage of being capable of being used for accurately assessing the effect of difference of the neutral point grounding modes in a 10kV lightning stroke characteristic on the lightning stroke characteristic.

The invention relates to a method and an instrument for measuring the shock ground resistance of a transmission line tower. The method comprises the following steps: generating incident current by a shock current generator and filling the incident current into the ground; collecting the grounding voltage and the current of the tower by a data collecting device; carrying out treatment and linear amplification on the collected data by an MCU control panel to solve the voltage response of a grounding body under the action of standard lightning current and obtain an equivalent voltage um and a current peak im; and finally, obtaining the shock ground resistance of the tower according to a formula of Rch=um/im. The instrument comprises a current pole lead connecting plug, a grounding device connecting plug, controlled silicon, a charging board, a voltage-multiplying generator, a voltage collecting board, a current collecting board, a battery and a main control board, wherein the current polelead connecting plug is connected with the charging board and the voltage-multiplying generator and then connected to the main control board; the controlled silicon is connected to a circuit in series; the voltage collecting board is connected with a voltage pole lead connecting plug, the grounding device connecting plug and the main control board; the current collecting board is connected with the current pole lead connecting plug, the grounding device connecting plug and the main control device; and the battery is directly connected to the main control board.

The invention relates to a method for identifying properties of lightning faults of an overhead line on the basis of the interval distribution of lightning current amplitude and belongs to the technical field of a high voltage. After the overhead line has a lightning tripping fault, fault information such as a grounding resistance of a fault tower, characteristic parameters of a tower rod, positioning information of a lightning monitoring system, topographic parameters and the like are collected; according to a circuit lightning protection performance algorithm and a shielding failure electrical geometric model principle, the counterattack lightning withstand level of the circuit suffering from lightning stroke and the amplitude distribution interval of the shielding failure critical lightning current are calculated by integrating a statistics rule of structural parameters of the tower and the line; and finally, the occurrence probabilities corresponding different lightning fault types of the line are obtained by utilizing a line lightning fault property judgment probabilistic algorithm model. According to the invention, the objective and reliable lightning fault type occurrence probabilities are obtained by utilizing the lightning fault property judgment probabilistic algorithm model; a judging result contains a certain fault-tolerant margin; the aims that information amount required by the lightning fault property judgment is small and the fault information is easy to acquire by operation and maintenance personnel of the line are fulfilled; and the judgment method is simple and rapid and has strong practicality.

The invention relates to a simulation test method for testing the lightning protection performance of a pole and tower grounding device of high-voltage power transmission line. The existing impulse grounding test process has the problem that a test model is simple and small in comparison with a real grounding device, or the problem that the simulation experiment has large gap from the real condition resulting from the large difference between a test power supply and the real lightning current. The simulation test method provided by the invention comprises the following steps: measuring soil resistivity of the test field; determining the position of a voltage reference point during the impulse grounding test according to the power frequency ground resistance measurement result of the grounding device; arranging voltage and current leads during the impulse grounding test; carrying out large-current impulse grounding measurement of the grounding device; measuring the power frequency ground resistance of the grounding device again in such a manner that all electrodes are located in the same positions as in the previous measurement; and analyzing the impulse test result. The simulation test method provided by the invention can narrow the gap between the simulation test and the real condition, and can be used for resistance reduction scheme optimization and impulse performance evaluation of the pole and tower grounding device of the high-voltage power transmission line.

The invention relates to a method for recognizing the shielding failure and the counterattack of a high-voltage DC transmission line. The shielding failure of the line means that the thunderbolt directly strikes on the transmission line by steering clear of a ground wire; the counterattack means that the thunderbolt directly strikes on the ground wire or a pole tower, the electric potential on the top of the tower increases instantaneously, which causes the insulation flashover due to the existence of a pole tower earth resistor. The different theories generated by the electromagnetic transient component of the shielding failure and the counterattack of the high-voltage DC transmission line and different paths of transmission of the thunderbolt electromagnetic transient component on the circuit cause that the energy distribution of different frequency bands of the generated voltage transient state signals are different greatly. In a travelling wave analysis and high-speed acquisition system at the protective installation position, the small wave analysis is adopted to extract the energy of the zero modulus voltage in different frequency bands. The shielding failure and the counterattack are differentiated according to the property of the energy distribution. A large amount of emulations show that the method is reliable and effective. The method has intuitive and clear physical concepts, is easy to implement, can be widely applied to a high-voltage DC system protective device, provides important data for the lightening protection design of the line and provides reference for the operation and maintenance of the line.

The invention discloses an insulation resistance and grounding resistance comprehensive tester based on a programmable power supply. The tester comprises the programmable power supply, a signal acquisition and analog/digital converter, a microcontroller, a keyboard and display circuit and an alarm and control circuit, wherein state switchover control software is arranged in the microcontroller. The tester has a basic operating principle that: the microcontroller switches an operating state of the tester, namely an insulation resistance testing state or a grounding resistance testing state, through the state switchover control software, and controls the programmable power supply to output direct current high voltage or alternating current high current serving as a testing power supply of electrical equipment to be tested according to the operating state of the tester; and the testing power supply is input into the microcontroller through the signal acquisition and analog/digital conversion circuit to perform closed-loop control and resistance measurement. The tester works stably, has high testing accuracy and integrates measurement, control and display; and moreover, parameters and alarm points can be independently set, function switch can be realized in an insulation resistance test and a grounding resistance test, and the safety of the electrical equipment is convenient to detect.

In the present invention, the universal serial bus connection detecting circuit system includes one transmission circuit and one detection circuit, and the detection circuit includes one set of differential signals wires, one set of earthed resistor assembly and one set of potential resistor, assembly, with each earthed resistor assembly and each potential resistor assembly being connected to thesame differential signal wire via one switch assembly. The transmission circuit is used to receive one current relative signal from power source to the differential signal wire and each current relative signal is earthed via the earthed resistor. The detection circuit is used to detect the change in current flowing through each differential signal wire.

The invention relates to an overvoltage protection device and method for the alternating current side of a voltage source converter high voltage direct current transmission system. The overvoltage protective device is connected to two ends of a ground resistor of the converter transformer valve side in parallel and used for acting to lead failure current away, restraining the level of overvoltage of an alternating current circuit I (4) and protecting a converter valve body (9) when overvoltage of a direct current circuit (8) exists due to a fault of the alternating current circuit I (4) or a fault of the direct current circuit (8) or a valve base controller detects the phenomenon that the alternating current circuit I (4) breaks down. The protective device is rapid in action, strong in through-flow capacity, large in absorbed energy, and capable of rapidly protecting the valve body. A control protective device with a complicated structure and complicated functions is not needed. The overvoltage protective device is simple in structure, low in cost and easy to implement, reduces the cost of the alternating current and insulation cost of a converter valve, guarantees safety of the alternating current circuit and the converter valve, improves fault-resistance ability of a converter station, and guarantees safe and stable operation of the voltage source converter high voltage direct current transmission system.

The invention discloses a high-accuracy implement method of an element for measuring a grounding distance unrelated to the loading current and the grounding resistance. When a high-voltage/ ultra-high-voltage/extra-high-voltage has a single-phase grounding fault, the current in a relay location is IPhi, and the voltage is UPhi; the distance from the fault point to the relay location is x; the voltage at the fault point is UPhif; the grounding current is IPhif; and the break current DeltaIPhin of positive sequence and negative sequence in the relay location is measured. Since the grounding is ohmic, UPhif is in the same phase with IPhif; and since DeltaIPhin has the same phase angle as IPhif, UPhif has the same phase angle as the DeltaIPhin, thereby further obtaining a fault distance formula which is unrelated to the loading current and the grounding resistance, wherein Phi is equal to a, b or c, and n is equal to 1 or 2. Since the formula itself is unrelated to the loading current and the grounding resistance, and DeltaIPhin and IPhif have the same phase angle, as a distance protective impedance measuring element, the element has high measuring accuracy, and is not affected by the loading current or the high resistance grounding fault. Theoretical analyses and simulation results show that the proposed principle has very high practicability and computational accuracy.