128 results about "Electrical resistance meter" patented technology

The invention discloses an anti-interference measurement method for Josephson junction resistance, and belongs to the technical field of quantum chips. According to the method, n * m resistance measurement values are obtained by applying n alternating-current electric signals with different frequencies to a Josephson junction and performing m times of measurement under the action of each alternating-current electric signal; determining a weight corresponding to each numerical value based on the occurrence frequency of the numerical value of each resistance measurement value in the n * m resistance measurement values; and determining a resistance calculation value of the Josephson junction by using each numerical value and the corresponding weight. According to the method, multiple times of measurement are carried out under the alternating current signals with different frequencies, the proportion of the resistance measurement values with errors caused by noise coupling in the environment to all the resistance measurement values is reduced, and the accuracy of Josephson junction resistance measurement can be effectively improved.

The invention discloses an electric energy quality loss test method, system and device and a medium. The method comprises the following steps: acquiring three-phase voltage data and three-phase current data; calculating the equivalent total loss power in the power distribution network line through the apparent power value, the voltage and the resistance based on the collected voltage and current data; and based on the equivalent total loss power, in combination with the power factors of different line losses, carrying out line loss subentry decoupling to obtain additional line losses caused by different electric energy quality problems. According to the invention, extra loss of the line caused by electric energy quality can be accurately measured, and line resistance does not need to be measured.

The invention provides a resistor and capacitor measuring circuit and method, and relates to the technical field of resistor and capacitor measurement, and the resistor and capacitor measuring circuit comprises a switch S1, a switch S2, a switch S3, a switch S4, a switch S5, a switch S6, a reference capacitor CREF, a capacitor CTEST to be measured, a reference resistor RREF, a resistor RTEST to be measured, a Schmitt trigger u1, a time-to-digital converter TDC and a microprocessor muC. And the Schmitt trigger u1, the time-to-digital converter TDC and the microprocessor muC are sequentially connected in series. According to the resistor-capacitor measuring circuit and method, the discharge time of the reference resistor-capacitor and the discharge time of the resistor-capacitor to be measured are respectively measured through the time-to-digital converter, the time proportion is calculated, and the parameters of the resistor-capacitor to be measured and the resistor-capacitor to be measured are calculated and reversely deduced by combining the known reference capacitor and the resistor. The correction compensation amount is obtained through an additional measurement state, and then the measurement result is corrected, so that the influence of the conduction loss of the switch on the measurement result is greatly reduced.

The invention discloses a contact network insulation resistance online monitoring system, method, device and medium, the contact network insulation resistance online monitoring system comprises a plurality of detection branches, each detection branch comprises a detection resistor and a contactor which are connected in series, and the detection branches are connected with a feeder cabinet in parallel; the incoming line cabinet control module is used for acquiring power supply voltage; the feeder cabinet control module is used for acquiring the voltage of the overhead line system and calculating the insulation resistance of the overhead line system according to the power supply voltage, the voltage of the overhead line system and the detection resistance; and the upper computer is used for storing and displaying the real-time insulation resistance of the overhead line system and the historical insulation resistance of the overhead line system. According to the invention, high-frequency accurate detection and environmental parameter acquisition of the ground (steel rail) insulation resistance of the overhead line system can be realized, and insulation abnormity can be found and early warning can be given out in time before the insulation decline of the overhead line system is developed into a short-circuit fault.

The invention relates to the technical field of intelligent monitoring, in particular to an intelligent monitoring system and device for a box transformer substation, and the system comprises a data collection module which collects the initial sensing data in the box transformer substation in real time, and the initial sensing data comprises electrical parameters and environmental parameters; the communication network and data processing module cleans the initial sensing data and transmits the initial sensing data to a data terminal in real time to obtain terminal cleaning data; the performance temperature power analysis module analyzes the insulation performance and the mapping relation between the temperature and the output power to obtain an insulation temperature formula; the control module judges whether the output power exceeds a threshold value or not, if yes, the equivalent resistance of the optimal insulation performance and the optimal temperature is calculated, and the optimal insulation performance and the optimal temperature are calculated according to the equivalent resistance of the optimal insulation performance and the optimal temperature. By analyzing and optimizing the insulation performance and the temperature, unnecessary energy waste is reduced, the energy utilization efficiency is improved, and potential fault hidden dangers are found and processed in time.

The invention discloses a method and a system for determining reactive compensation capacity of a transformer area and a voltage out-of-limit governance device, which are applied to voltage reactive compensation of rural transformer areas, and the method comprises the following steps: obtaining the daytime maximum reverse power, the nighttime maximum load power, the line basic parameters, the maximum voltage threshold value and the minimum voltage threshold value of the transformer area; calculating line reactance and real-time line resistance by combining the basic parameters of the line; and respectively comparing respective threshold values through the maximum voltage and the minimum voltage, and calculating the reactive compensation capacity of the transformer area by combining the daytime maximum reverse power of the transformer area, the nighttime maximum load power, the line reactance and the real-time line resistance. In the working process, reactive compensation capacity calculation is conducted on the capacitor and the reactor according to relevant information of the transformer area, the relatively accurate reactive compensation capacity is obtained, then the capacity configuration of the voltage out-of-limit treatment device is conducted, the reactive voltage regulation effect can adapt to the actual situation requirement of the transformer area, and daytime and nighttime bidirectional out-of-limit of the voltage of the transformer area is effectively treated.

The invention belongs to the technical field of glass industry, and relates to a method for calculating distribution of electrical parameters of molten glass in an advanced-generation substrate glass gas-electric kiln. Comprising the following steps: setting process boundary conditions of kiln operation; simulating an operation state of the kiln under a set boundary condition by adopting simulation software, equally dividing molten glass in the kiln into a plurality of layers along a vertical height direction, and acquiring temperature distribution data of each layer; based on the temperature distribution data of each layer, determining the resistivity corresponding to each layer of molten glass according to a temperature-resistivity fitting relationship; calculating the resistance of each layer of molten glass based on the resistivity corresponding to each layer of molten glass and in combination with the electrode spacing and sectional area corresponding to each layer of molten glass; and constructing each layer of molten glass into a parallel circuit model, and calculating the current and power of each layer of molten glass according to the loading voltage and resistance. According to the method, accurate quantification and optimal control of the electric heating parameters of the molten glass in the kiln are realized, and the method is suitable for production process optimization of high-generation large-size substrate glass.

The application discloses a high-voltage vacuum arc-extinguishing chamber contact resistance and equivalent thermal analysis method, comprising the following steps: three-dimensional equivalent modeling of the high-voltage vacuum arc-extinguishing chamber; determining the number and position of the contact piece contact points; experimentally measuring the high-voltage vacuum arc-extinguishing chamber loop resistance and calculating the contact radius; establishing a conductive bridge, and obtaining a simulation loop resistance by an electromagnetic simulation software; adjusting the contact radius so that the simulation loop resistance is consistent with the experimental measurement result, and obtaining an adjusted conductive bridge; performing electromagnetic field-thermal field-airflow field two-way coupling simulation analysis based on the high-voltage vacuum arc-extinguishing chamber equivalent model of the adjusted conductive bridge, and obtaining the high-voltage vacuum arc-extinguishing chamber temperature rise distribution. The application can more accurately simulate the current constriction effect on the large-size high-voltage vacuum contact piece and more accurately simulate the high-voltage vacuum contact piece contact resistance.

The invention discloses a method and device for determining voltage and current of an IGBT of a flexible direct current transmission engineering submodule, and a method for determining voltage and current of an IGBT of a flexible direct current transmission engineering submodule, by obtaining the topological structure and system parameters of a converter to be analyzed, based on the differential equation of a capacitor element, a discretized adjoint model of a capacitor in a half-bridge submodule is obtained; according to the number of submodules currently put into use, the Thevenin model equivalent resistance of the half-bridge submodule in the converter to be analyzed is calculated, and a controlled voltage source is calculated using the voltage value at the last moment, the current value at the last moment, and the Thevenin model equivalent resistance; based on the discretized adjoint model, a Thevenin equivalent model of a bridge arm is obtained, and according to the topological structure and system parameters, the Thevenin equivalent model of the bridge arm is simulated to obtain the voltage stress and current stress of the IGBT in a normal state. By building an accurate transient model equivalent to MMC, the accuracy of the voltage and current stress of the actual working condition of the IGBT of a single submodule obtained is improved.

The present application discloses a charging pile insulation detection system and method. The system uses a charging pile insulation detection circuit to perform insulation detection on the charging pile. The system includes: a bus voltage measurement module, which is used to measure the positive bus voltage to ground, the negative bus voltage to ground and the voltage between the positive and negative buses of the charging pile insulation detection circuit; an insulation resistance calculation module, which is used to calculate the positive bus insulation resistance to ground and the negative bus insulation resistance to ground in the charging pile insulation detection circuit according to the positive bus voltage to ground, the negative bus voltage to ground and the voltage between the positive and negative buses; and an insulation state determination module, which is used to determine the insulation state of the charging pile according to the positive bus insulation resistance to ground and the negative bus insulation resistance to ground. The present application solves the technical problem of insulation detection of charging modules of charging piles in related technologies.

The invention discloses a wire harness testing device, method and equipment and a storage medium. The device comprises a signal generation module, a current source, a plurality of measuring circuits, a signal comparison module and a resistance calculation comparison module, and each measuring circuit comprises a test signal selection circuit, a to-be-tested cable, a signal acquisition module and a voltage acquisition module. The signal generation module is used for outputting a first signal to a target to-be-detected cable; the current source is used for outputting test current to a target to-be-tested cable; the signal comparison module is used for determining whether the actual input / output end of the target to-be-detected cable is a theoretical input / output end according to the first signal, the second signal and the theoretical input / output end of the target to-be-detected cable; and the resistance calculation and comparison module is used for determining the actual resistance of the target to-be-detected cable according to the first voltage, the second voltage and the first current, and determining whether virtual connection exists in the target to-be-detected cable according to the actual resistance and the designed resistance. The unmanned aerial vehicle wire harness testing efficiency can be improved.

The invention relates to the technical field of fire sensing, and discloses an electrical fire state sensing system and method for a low-voltage distribution line, and the method comprises the steps: setting a first monitoring point at a wire inlet end of a distribution loop, setting a second monitoring point at a load access end, setting a differential protection region, and calculating a first on-resistance; performing moving average processing on the first on-resistance to obtain a second on-resistance, calculating a first reference on-resistance according to the second on-resistance, and performing temperature correction on the first reference on-resistance to obtain a second reference on-resistance; according to the method, the on-resistance deviation rate, the on-resistance growth rate and the on-resistance fluctuation coefficient are calculated, whether the on-resistance is in an early warning state, an alarm state or a dangerous state is judged, the on-resistance of the section is calculated in real time according to the ratio of the differential voltage drop to the current, and the technical problem that a fault section cannot be accurately positioned through traditional whole-line monitoring is solved.

A resistance calculation device includes: a characteristic calculation portion configured to calculate a shrinkage rate for each single electrode based on a capacity shift amount of a positive electrode of a deteriorated secondary battery, a capacity shift amount of a negative electrode of the deteriorated secondary battery, a deterioration amount of the positive electrode, and a deterioration amount of the negative electrode, and to calculate a curve representing characteristics of a state of charge and an open circuit voltage of an equivalent circuit of the deteriorated secondary battery by deforming an opening end potential curve for each single electrode before deterioration of the deteriorated secondary battery by the shrinkage rate for each single electrode based on a fixed point; a change amount calculation portion configured to calculate an amount of change in the open circuit voltage of the equivalent circuit based on a difference between the opening end potential curve for each single electrode before the deterioration and the curve representing the characteristics of the state of charge and the open circuit voltage of the equivalent circuit; and a resistance calculation portion configured to calculate a DC resistance of the equivalent circuit by dividing a result of addition of an amount of change in a DC voltage of the equivalent circuit to which a pulse current is applied and the amount of change in the open circuit voltage of the equivalent circuit by a current value when the pulse current is applied to the equivalent circuit.

The application belongs to the technical field of thermal field measurement under high temperature environment, and particularly relates to a high-temperature thermal field direct measurement sensor array. In use, thermal radiation is irradiated on a heat-absorbing layer, the heat-absorbing layer absorbs the thermal radiation and transmits the heat to a high-conductivity micro region, so that a transverse thermoelectric voltage is generated between a first electrode and a second electrode, and the heat flux density at the high-conductivity micro region is calculated according to the transverse thermoelectric voltage; the temperature at the high-conductivity micro region is calculated according to the resistance between a third electrode and a fourth electrode, the heat flux density at the high-conductivity micro region is calibrated through the temperature at the high-conductivity micro region, and the spatial distribution characteristics of the heat flux are inversed by comprehensively considering the heat flux and the temperature at multiple high-conductivity micro regions. The high-temperature thermal field direct measurement sensor array can output the spatial distribution of two modes of heat flux density and temperature, and realize high-precision spatial distribution measurement of the thermal field.

The application discloses a precision hardware fatigue damage detection method and system, and relates to the field of precision mechanical detection.The method comprises the following steps: coupling a flexible impedance sensing array with a precision hardware to be detected; the array substrate is made of polydimethylsiloxane, and the surface array groove is filled with a conductive hydrophilic composite gel formed by in-situ polymerization of acrylamide monomer, sodium alginate and nanometer carbon fibers, thereby forming a plurality of miniaturized impedance units; a constant pressure is applied through a pressure feedback control system, so that the gel produces elastic deformation to cover and compensate the micron-level roughness of the surface of the detection area; a micro-amplitude sinusoidal voltage excitation is applied, current response data in the swept frequency band is collected, complex impedance information is extracted and fitted to a randall equivalent circuit model, and charge transfer resistance and interface capacitance values are obtained; and the parameter deviation degree is calculated according to the charge transfer resistance of the current detection period and historical reference, so as to determine the fatigue damage condition of the local area.

The present application belongs to the field of oil exploitation equipment monitoring, and relates to a sensor-free temperature measurement method and system for a downhole motor of an electric submersible pump, which comprises the following steps: collecting a reference resistance and a reference temperature of a winding of the motor of the electric submersible pump; collecting voltage and current data and working condition parameters of the motor of the electric submersible pump in real time; adaptively selecting a resistance calculation method according to the collected motor working condition parameters to calculate a total loop real-time resistance containing a power cable resistance; calculating a cable resistance component under a current working condition according to well temperature gradient data of the oil well and in combination with power cable parameters; calculating a temperature value of the downhole motor of the electric submersible pump under the current working condition; setting a safe running temperature threshold of the motor of the electric submersible pump, and performing a protection action when the temperature value is detected to exceed a preset threshold. The method has the beneficial effect that sensors and electronic elements do not need to be arranged downhole, and temperature monitoring of the electric submersible pump can be realized only by using the electric submersible pump unit and the power cable, and important reference can also be provided for oil well regulation and control.

The invention discloses a transformer area theoretical line loss calculation method and system, and the method comprises the steps: obtaining the voltage of a user of each phase, the voltage of a low-voltage side of a distribution transformer, and the current of each phase of the low-voltage side of the distribution transformer under the selected target time granularity of a transformer area; based on the voltage of each phase user, each phase voltage of the low-voltage side of the distribution transformer and each phase current of the low-voltage side of the distribution transformer, virtual equivalent resistance of the transformer area under the target time granularity is calculated, and based on each phase current of the low-voltage side of the distribution transformer, a three-phase imbalance correction coefficient is calculated; the theoretical line loss of the transformer area under the target time granularity is calculated based on the three-phase imbalance correction coefficient and the virtual equivalent resistance, complex data difficult to obtain do not need to be depended on, and zero line loss caused by the three-phase imbalance phenomenon existing in the actual transformer area is considered by introducing the three-phase imbalance correction coefficient. The theoretical line loss calculated based on the three-phase imbalance correction coefficient and the virtual equivalent resistance is more accurate and efficient, so that the theoretical line loss calculation efficiency and accuracy are improved.

The invention provides a dry-type hollow shunt reactor winding inter-strand short circuit fault identification method, and relates to the technical field of power equipment fault diagnosis. The method comprises the following steps: acquiring current and voltage waveforms of a reactor; calculating a current effective value and a voltage effective value in the latest n periods, and an average phase difference between the voltage and the current in the n periods; the average equivalent resistance in the latest n current periods is calculated; calculating an average power factor in the latest n current periods; calculating the average active power loss in the latest n current periods; calculating an average power factor angle in the latest n current periods; judging whether the reactor has an inter-strand short-circuit fault or not; judging whether the reactor has a same-turn inter-strand short-circuit fault or not; judging whether the reactor has a short-circuit fault between different turns and the like; according to the method, the difference between the set parameter change rate threshold values is multiple orders of magnitude, so that the identification accuracy of the same-strand and different-turn inter-strand short-circuit faults of the dry-type shunt reactor is greatly improved.

This invention relates to the field of power electronics, specifically to an online parameter identification model predictive control method for grid-connected inverters: The method involves measuring the grid-side current and voltage at the start of the current switching cycle; applying a control signal to the grid-connected inverter; calculating the reference current for future switching cycles; identifying the real-time inductance and resistance of the line through online parameters; calculating the grid-side current at the start of the next switching cycle based on the real-time inductance and resistance, and compensating for the current prediction error of the predicted grid-side current in the cycle after that; constructing a reserve set of action vectors based on the current error vector quadrant between the compensated reference current for future switching cycles and the grid-side current at the start of the next switching cycle; and selecting the optimal voltage vector from the reserve set according to a value function for use in the next switching cycle. Compared with existing technologies, this invention addresses the shortcomings of fixed parameters, corrects prediction deviations caused by fixed parameters, and achieves more accurate voltage vector selection.

The present invention relates to the field of electronic information engineering technology, and discloses a PCB planar transformer DC resistance design method, including the following steps: S1 calculates the winding DC resistance through a formula based on conventional resistance; S2 calculates the conductor cross-sectional area S and etching factor of the PCB product through a formula; S3 derives the PCB DC resistance through a formula; S4 determines the DCR design range; S5 determines whether the winding DCR of the above design meets the requirements; S6 calculates the line width and copper thickness design values ​​using a reverse calculation formula; S7 develops DCR design calculation software through the above derivation steps. In the present invention, based on the resistance calculation formula, combined with the process copper thickness tolerance, line width tolerance, etching factor manufacturing capability and PCB conductor specification shape, an effective calculation formula for the PCB planar transformer DC resistance (DCR) is output, the control range of copper thickness and line width, the influencing factors related to DC resistance, is accurately defined, and the DCR design calculation software is developed using this derivation formula to improve accuracy and work efficiency.

The application discloses a kind of transformer area reactive power compensation capacity determination method, system and voltage out-of-limit management device, it is applied to rural transformer area voltage reactive power compensation, this method includes: obtaining transformer area daytime maximum reverse sending power, nighttime maximum load power and line basic parameters, and maximum voltage threshold, minimum voltage threshold;Line reactance and real-time line resistance are calculated in combination with line basic parameters;By maximum voltage and minimum voltage respectively compared with respective threshold, in combination with transformer area daytime maximum reverse sending power, nighttime maximum load power, line reactance and real-time line resistance, the reactive power compensation capacity of transformer area is calculated.The application is in work, according to transformer area relevant information, capacitor and reactor reactive power compensation capacity calculation is carried out, and relatively accurate reactive power compensation capacity is obtained, then voltage out-of-limit management device capacity is configured, so that reactive power voltage regulating effect can adapt to the actual situation requirement of transformer area, effectively governs transformer area voltage daytime and nighttime bidirectional out-of-limit.

The internal resistance calculating device of the embodiment is provided with a current acquisition section, a voltage acquisition section, a charge amount calculation section, and an internal resistance calculation section. The current acquisition section acquires a battery current flowing in a battery. The voltage acquisition section acquires a battery voltage applied to the battery. The charge amount calculation section integrates the battery current acquired by the current acquisition section with respect to time, and calculates a charge amount moved to the battery. The internal resistance calculation section calculates an internal resistance of the battery based on a change amount of each of the battery current and the battery voltage until the charge amount calculated by the charge amount calculation section becomes equal to or greater than a threshold value set in advance.

The application relates to the technical field of power electronic device state monitoring, in particular to a SiC MOSFET junction temperature monitoring method, device, equipment and medium, which comprises the following steps: obtaining a through-state current and a through-state voltage of a measured silicon carbide metal oxide semiconductor field effect transistor (SiC MOSFET); calculating a through-state resistance of the SiC MOSFET according to the through-state current and the through-state voltage; and calculating a junction temperature of the SiC MOSFET according to the measured through-state resistance based on a mapping relationship between the through-state resistance and the junction temperature established in advance. Thus, the problems in the prior art that the junction temperature monitoring method can only be applied to a relatively narrow switching frequency range and the precision is seriously affected by device aging are solved, the working frequency is improved, the cost is reduced, and the influence of device aging on the junction temperature monitoring is reduced by proposing a novel through-state voltage drop online measurement circuit and a SiC MOSFET junction temperature monitoring strategy considering aging.

A controller for a substrate processing system includes a resistance calculation module configured to: receive a first current and a second current corresponding to a first heater element and a second heater element of a substrate support, respectively; receive a first voltage and a second voltage corresponding to the first heater element and the second heater element, respectively; calculate a first resistance of the first heater element based on the first voltage and the first current; and calculate a second resistance of the second heater element based on the second voltage and the second current. A temperature control module is configured to separately control the power provided to the first heater element and the second heater element based on the first resistance and the second resistance, respectively, and the corresponding relationship between the first resistance and the second resistance and the first temperature and the second temperature of the substrate support.

The invention discloses a high-voltage direct-current support capacitor insulation resistance measuring device and method, and the device comprises a direct-current charging test loop, a test loop, a discharging test loop, and a control system. The direct-current charging test loop comprises a power supply, a first switch, a voltage regulator, a boosting transformer, a high-voltage silicon stack, a current-limiting resistor and a second switch, the test loop comprises a third switch, a first discharging resistor, a voltmeter and a high-voltage direct-current support capacitor to be tested, and the discharging test loop comprises a fourth switch, a second discharging resistor, a fifth switch and a voltage divider. The control system comprises a signal acquisition unit, a control output unit and a controller; the measurement method comprises the steps of capacitance measurement, voltage measurement and insulation resistance calculation. The device is simple in structure and convenient to operate, and can meet the insulation resistance measurement test requirements of the high-voltage and high-capacity direct-current support container.

The invention relates to the technical field of rail transit, and provides a rail transit direct current traction power supply equivalent resistance calculation method and system, and the method comprises the steps: determining feeder voltage values and feeder current values of two sides of a power supply arm of a train at different operation times; calculating and inputting the feeder voltage values and the feeder current values at different operation times to an equivalent circuit model of a preset rail transit direct current traction power supply to obtain equivalent resistance of a power supply arm output by the equivalent circuit model; wherein the equivalent circuit model is used for determining an equivalent circuit equation set; the equivalent circuit equation set comprises equivalent circuit equations of the train at different running time; the equivalent circuit equation is used for representing that the feeder voltage difference value on the two sides of the power supply arm is equal to the voltage drop difference value generated when feeder current on the two sides of the power supply arm passes through the equivalent resistance and the line resistance of the power supply arm. The equivalent resistance of the power supply arm can be accurately calculated, and the accuracy of fault distance measurement and the accuracy of fault positioning are improved.

The invention discloses an ultra-high voltage shunt reactor turn-to-turn fault detection method based on equivalent resistance variation, which comprises the following steps: dividing a fault phase winding into a grid-connected side non-short-circuit section, a short-circuit turn section and a neutral point side non-short-circuit section, and defining the number of turns, resistance, self-inductance and mutual inductance parameters of each section; constructing a Kirchhoff voltage and current equation set based on the electrical parameters of each section of winding, and deducing a phasor relationship between a fault phase head end current and a turn current in combination with a short-circuit current relational expression; the terminal voltage of the shunt reactor is expressed as a function of head end current, and an equivalent impedance analytical expression containing the short-circuit turn ratio and the transition resistance is obtained; setting a minimum identification threshold of a short-circuit turn ratio and a maximum tolerance threshold of a transition resistor, traversing all equivalent resistance calculation values in the range of the two thresholds, and multiplying the minimum value by a reliable coefficient to serve as a fault criterion setting value; three-phase voltage and current data are collected in real time, a fundamental wave phasor is extracted to calculate an equivalent resistance measurement value, and if any phase measurement value exceeds a setting value, the turn-to-turn fault is determined.

The present invention discloses a method for measuring the grounding resistance of a transmission tower. The method comprises: short-circuiting the grounding down conductors corresponding to the pole legs of the tower under test, retaining the connection between the grounding down conductor and one of the pole legs, and disconnecting the grounding down conductor from the remaining pole legs to build a test model; measuring the down conductor current value and the current value of each grounding body under a first working condition and a second working condition, and calculating the branch current of the remote multi-level grounding body; calculating the grounding resistance of the tower under test based on the down conductor current value and the current value of each grounding body under the first working condition and the second working condition, the branch current of the remote multi-level grounding body, and the preset parallel equivalent resistance of the remote multi-level grounding body. The present invention builds a test model, measures the current value of each loop of the equivalent circuit under the first working condition and the second working condition, and calculates the grounding resistance of the tower under test in combination with the preset parallel equivalent resistance of the remote multi-level grounding body; thereby improving the accuracy of the grounding resistance measurement.

The invention relates to the technical field of hydropower stations, discloses an impedance-based generator self-excitation protection method and device, and aims to solve the problems of high cost and easy electric quantity loss in the existing method. The scheme mainly comprises the following steps: acquiring the generator end voltage and the generator end current of a generator in real time; calculating terminal impedance according to the terminal voltage and the terminal current, and calculating system capacitive reactance according to the terminal impedance and equivalent resistance of an external system side of the generator; and judging whether self-excitation occurs or not according to the system capacitive reactance and the direct-axis synchronous reactance of the generator, and determining whether to split the generator or not according to a judgment result. According to the invention, the self-excitation protection cost is reduced, the electric quantity loss is avoided, and the method is particularly suitable for a small hydropower station connected with a grid through a large hydropower station.

Devices and methods for insulation detection are provided. The device includes a voltage acquisition unit, a calculation unit and at least two resistance units. Each resistance unit is electrically connected to a ground terminal and a target output wire. The voltage acquisition unit acquires a positive bus-to-ground voltage, a negative bus-to-ground voltage and a neutral-to-ground voltage after a target resistance unit connects a path between target output wire and ground terminal. The calculation unit calculates first current corresponding to target output wire based on voltage corresponding to the target output wire and the resistance of the target resistance unit; calculates a positive insulation resistance to ground, a negative insulation resistance to ground and a neutral-wire insulation resistance to ground based on first current, positive bus-to-ground voltage, negative bus-to-ground voltage and neutral-to-ground voltage; and determines whether insulation failure occurs in three-wire HVDC system.