1039results about "Earth resistance measurements" patented technology

An instrument for PCR comprising an assembly, a heated cover, and a computer. The assembly can include a sample block, Peltier devices, and a heat sink, clamped together. The sample block temperature can be changed by controlling the Peltier devices with the computer. A perimeter heater can be used to in prove thermal uniformity. A heated platen can push down onto tube caps to apply a minimum force for seating the tubes. The force can be applied about the periphery of the tube caps to prevent distortion of the caps. The platen can be heated to provide thermal isolation and prevent evaporation from the surface of the sample. The software can include diagnostics to compensate for variation in thermoelectric coolers such that all instruments can perform identically.

An instrument for performing highly accurate PCR employing an assembly, a heated cover and an internal computer. The assembly is made up of a sample block, a number of Peltier thermal electric devices and heat sink, clamped together. The sample block temperature is changed exclusively by the thermoelectric devices controlled by the computer. The sample block is of low thermal mass and is constructed of silver. The Peltier devices are designed to provide fast temperature excursions over a wide range. The heat sink has a perimeter trench to minimize edge losses and is adjacent to a continuously variable fan. A perimeter heater is used to improve the thermal uniformity across the sample block to approximately ±0.2° C. A heated platen pushes down onto the tube caps to apply a minimum acceptable force for seating the tubes into the block, ensuring good thermal contact with the block. The force is applied about the periphery of the tube caps to prevent distortion of the caps during thermal cycling. The platen is heated to provided thermal isolation from ambient conditions and to prevent evaporation from the surface of the sample into the upper portion of the sample tube. A control algorithm manipulates the current supplied to the thermoelectric coolers such that the dynamic thermal performance of the block can be controlled so that pre-defined thermal profiles for the sample temperature can be executed. The sample temperature is calculated instead of measured using a design specific model and equations. The control software includes calibration diagnostics which permit variation in the performance of thermoelectric coolers from instrument to instrument to be compensated for such that all instruments perform identically. The block / heat sink assembly can be changed to another of the same or different design. The assembly carries the necessary information required to characterize its own performance in an on-board memory device, allowing the assembly to be interchangeable among instruments while retaining its precision operating characteristics. The instrument has a graphical user interface. The instrument monitors the thermoelectric devices and warns of changes in resistance that may result in failure.

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.

This invention discloses an on-line monitoring method of grounding net of power station and its device. The method includes following steps: bury state transmitter in soil where have station earthing net; survey electric resistance of transmitter electrode and self corrosion electric potential; add square wave signal to electrode of state transmitter, survey electric current; after smoothing surveyed data, deliver to microprocessor to compute corrosion rate of electrode, take it as corrosion rate of grounding electrode in corresponding area; use corrosion rate to compute corrosion deep and actual geometry size of grounding electrode of grounding net, and use computing method of grounding net numerus to compute electricity performance parameter of grounding net; compare computed electricity performance parameter and design value, judge safe performance of grounding net. This invention can do online monitoring to corrosion deep and electricity performance parameter of grounding net of power station. The invention provides a overall, effective, economic, real time solving method to survey and evaluate grounding net of power station.

The invention provides an insulation monitoring device which is used for monitoring ground insulation conditions of high voltage direct current power source direct current output voltage, judging insulation conditions through insulation resistance of monitoring bus-bar to the ground, and uploading values of the insulation resistance to an upper computer. The insulation monitoring device comprises a first additional delivering resistor R1, a second additional delivering resistor R2, a first delivering switch K1 and a second delivering switch K2. The R1 is in series connection with the K1. One end of the R1 is connected to a positive bus-bar. The other end of the R1 is connected to the ground. The R2 is in series connection with the K2. One end of the R2 is connected to a negative bus-bar. The other end of the R2 is connected to the ground. Equivalent ground insulation resistance of the positive bus-bar is R+. Equivalent ground insulation resistance of the negative bus-bar is R-. The R+ and the R- are obtained in a detected mode through an unbalanced bridge method. Due to adoption of the unbalanced bridge method, conditions of any insulation such as ground insulation of a bus-bar monopole, bus-bar twin poles, a monopole of the same branch, twin poles of the same branch, monopoles of different branches and twin poles of the different branches can be monitored, and any insulation condition can not be omitted. Due to build of a branch monitoring equation, insulation conditions can be timely and accurately monitored.

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 relates to a circuit and a method for detecting a direct-current power ground insulation resistor. The circuit comprises resistors R1 to R5 and switches S1 to S2, wherein the resistors R1 and R3 have the same resistance value; the resistors R2 and R4 have the same resistance value; one end of the resistor R2 is connected to an anode of a direct-current power supply through the resistor R1, and the other end of the resistor R2 is grounded through the switch S1; the resistors R1 and R2 and the switch S1 form a first detection branch circuit; one end of the resistor R4 is connected to a cathode of the direct-current power supply through the resistor R3, and the other end of the resistor R4 is grounded through the switch S2; the resistors R3 and R4 and the switch S2 form a second detection branch circuit; and the resistor R5 is connected with the first detection branch circuit or the second detection branch circuit in parallel. The circuit has the advantages as follows: when resistance values of positive and negative ground insulation resistors R+ and R- of the direct-current power supply are reduced in a uniform amplitude way or close to each other, the resistance values of the resistors R+ and R- can be still detected, and detection precision of the resistors R+ and R- can be also guaranteed.

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.

A resistance measuring apparatus includes: a voltage injector that injects an AC signal into a circuit by applying an AC voltage to an injection coil; a current measuring unit that measures an AC current produced in the circuit by the injection coil using a detection coil; a processing unit that calculates the circuit resistance from the AC signal voltage and the measured AC current; and a reference signal generator that outputs a binary reference signal that has a same period as the AC voltage and is synchronized to the clock. The voltage injector generates a stepped wave whose amplitude changes in synchronization with a clock, applies a signal based thereon as the AC voltage. The current measuring unit converts the current in the detection coil to a voltage signal, carries out synchronous detection using the reference signal, and measures the AC current based on the synchronous detection result.

This invention discloses a measuring and controlling method of the direct earth insulating parameter of the distribution network. It has such steps as setting a high inductive-value reactor at the neutral point of the distribution network and a capacity-adjusting ground fault neutralizer injecting the frequency-changing current signal to the distribution network via the reactor, real-time measuring the back current signal and computing the direct earth capacitance, resistance and damping ratio of the distribution network. It detects the single-phase ground fault according to the displacement voltage and the damping ratio and instantly shuts the switch of ground fault neutralizer when the single-phase ground fault occurs and inputting proper ground fault neutralizer, compensating the network capacitance current and accelerating the extinguishing of the fault voltaic arc. This measuring and controlling method has high measuring accuracy and good real time and specially being appropriate to the single-phase loading distribution network. It thoroughly settles the neutral-point displacement voltage of the high-symmetry distribution network, fault arc blowout and the on-line puzzle of the targeted insulating parameter which is good to improve the indices of the reliability of the distribution network.

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.

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.

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 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.

A test pad array and dummy lead array for measuring anisotropic conductive film bond contact resistance on a liquid crystal display panel. The test pad and dummy lead arrays are provided on a surface of the liquid crystal display panel. The test pad array is electrically connected to a group of terminal pads disposed on the surface of the panel, which are electrically connected to an electronic device with anisotropic conductive film bonds. The test pad array allows the contact resistance of one or more of the anisotropic conductive film bonds to be measured on the panel. The dummy lead array is provided for electrically connecting a second electronic device to the panel. The dummy lead array is electrically connected to the test pad array such that a contact resistance of at least one anisotropic conductive film bond associated with the second electronic device can be measured on the panel using portions of the test pad array electrically connected to the dummy lead array.

The invention provides an insulation monitoring method for a switching type direct current system. The insulation monitoring method for the switching type direct current system comprises measuring the bus voltage; measuring the voltage to the ground from a positive pole and a negative pole of a bus; measuring insulation resistance to the ground from the positive pole and the negative pole of the bus according to the voltage to the ground from the positive pole and the negative pole of the bus; judging whether the insulation resistance to the ground from the positive pole and the negative pole of the bus is less than an insulation alarm valve value or not; judging the bus to be free of insulation fault if not; outputting or storing information of bus insulation abnormal alarm and abnormal polarity insulation resistance if yes; starting measuring of the insulation resistance to the ground from a positive pole and a negative pole of a load shunt circuit. According to the insulation monitoring method for the switching type direct current system, the insulation resistance to the ground of the positive poles and the negative poles of the bus and the load shunt circuit can be accurately measured, the accuracy is less than 5%, and an HVDC (High Voltage Direct Current) requirement for outputting suspension cannot be damaged.

The embodiment of the invention discloses a method and circuit for detecting ground insulation impedance of a photovoltaic array. The circuit is composed of a positive voltage division circuit and a negative voltage division circuit, wherein the resistance ratio of the positive voltage division circuit to the negative voltage division circuit is at least N1, N2, N3 and N4; and N3 is greater than 1 / 5 but less than or equal to 1 / N4, N1 is greater than 1 / N4 but less than or equal to 1 / N2, and 1 / N2 is greater than or equal to N1 but less than 1. The method for detecting the ground insulation impedance of the photovoltaic array comprises the steps of: respectively connecting the positive voltage division circuit and the negative pressure division circuit between a positive bus and a ground line and between the ground line and the negative bus during the detection; when a bus voltage is not greater than the product of a maximum output voltage of the photovoltaic array and the N1, adjusting the positive voltage division circuit and / or the negative voltage division circuit to enable the resistance ratio to be respectively N1 and N2; calculating the ground insulation impedance value of the photovoltaic array based on a serial partial pressure principle; and when the bus voltage is greater than the product, selecting the N3 and the N4 for corresponding operation and calculation so as to obtain a ground insulation impedance value. According to the embodiment of the invention, the problem that the ground insulation impedance cannot be detected exactly within a full voltage range when the differential value of the ground insulation impedances of the positive bus and the negative bus is very great in the prior art is solved.

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.

The invention discloses a method and device for accurately measuring the grounding resistance of a pole, and the method comprises the steps: judging the burying orientation of a grounding body through employing a magnetic field method; measuring the resistivity of soil nearby the grounding body through employing a quadrupole method; selecting the frequency range of an injection current according to the resistivity of soil, obtaining a group of pole grounding resistance measurement values through measurement, correcting the measurement result, and obtaining the accurate measurement value of the pole grounding resistance. The device and method can achieve the accurate measurement of the grounding resistance of the pole without cutting off a grounding lead. Firstly, the method and device achieve the vertical arrangement of poles through the judgment of the burying orientation of the grounding body, and improve the measurement accuracy; secondly, the method and device select the frequency of the injection current through the measurement of the resistivity of soil nearby the grounding body, and improves the adaptability of the method to different pole soil environments; finally, the method and device do not need to cut off the ground lead, and improve the work efficiency of grounding resistance measurement. A mean method is employed for calculating the grounding resistance of the pole, enables the measurement error to be minimum, and improves the accuracy of the measurement 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.

A double-clamp earth tester device, having a voltage-inducing transformer (VT) (30), a current-sensing transformer (CT) (32), a voltage source adapted to supply a voltage across a primary winding (31) on the VT core (44) and a signal processing unit (35) adapted to measure a resultant signal output from a secondary winding (33) on the CT core (46), is susceptible to errors induced by electromagnetic interference between the cores (44, 46) of the two transformers. Previously, the effects of this interference have been mitigated by surrounding one or both cores (44, 46) with electromagnetic shielding (42). This had lead to devices having a bulky head portion and attendant difficulties in accessing sites having restricted access (52). These problems have been overcome by providing means to modify the signal output form the secondary winding (33). This may be achieved magnetically by nullifying the parasitic magnetic fields (66) at source in the core (46) of the current-sensing transformer, or electrically by the addition of a negative signal to the output signal prior to or during processing in the signal processing unit (35).

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 relates to a method for determining the position of a voltage electrode in the measurement of grounding resistance in a transformer substation by the short-distance method. The method comprises the method of calculating the distribution of drain current in a ground net conductor and the grounding resistance and the method of calculating the ground potential, and the test position of the voltage electrode is given out according to the principles of the compensation method based on the calculation results of the two methods. The method can suppress or eliminate the related interference factors during the field test process while realizing the short-distance measurement of the grounding resistance, greatly save manpower and material resources and have important engineering practical value.

Disclosed are a multi-frequency scanning type high-voltage tower grounding resistance measurement apparatus and method. Included are an on-site measuring device and a background data processing center; the on-site measuring device comprises a power supply module for supplying power, an automatic sweep excitation source module for injecting currents of different frequencies, a signal acquisition module, a central processor module for control, a liquid crystal display module, a GPRS wireless communication module and a serial data output module; and the power supply module, the automatic sweep excitation source module, the signal acquisition module, the liquid crystal display module, the GPRS wireless communication module and the serial data output module are respectively connected to the central processor module, and the automatic sweep excitation source module and the GPRS wireless communication module are respectively connected to the signal acquisition module. The measurement apparatus and method are simple in wiring, and require no need of disconnecting a ground lead; the efficiency of the ground resistance measurement is improved to a great extent; and the multi-frequency scanning measurement method can avoid the effects of tower grounding inductance on measurement.

There is provided an insulation resistance detecting apparatus that accurately calculates an insulation resistance value in real time. The insulation resistance detecting apparatus includes: pulse generator 10, comparator 11 to which reference voltage VREF is supplied as one input and an output from pulse generator 10 is supplied as the other input, comparator 11 that outputs a low-level signal when the level of the other input exceeds reference voltage VREF, and that outputs a high-level signal when the level of the other input is lower than reference voltage VREF; resistance R1 provided on the output line of pulse generator 10 in series; coupling capacitor C2 one end of which is connected to the other input line of comparator 11 and the other end of which is connected to the output line of high-voltage DC power supply 21; capacitor C1 one end of which is connected to the other input line of comparator 11 and the other end of which is connected to a ground; and pulse width measuring device 12 that calculates the value of insulation resistance on the output line of high-voltage DC power supply 21 from the duty ratio of an output waveform of comparator 11.

An earth clamp for testing contact voltage, comprising a measuring circuit formed of a voltage inducing transformer and a current measuring transformer, adapted to be mutually coupled by an earth conductor whose earth impedance is to be measured, a microcontroller to deliver an alternating voltage to the voltage inducing transformer and, in response, to receive a reference voltage generated in the earth conductor and an earth current iB+iF induced in the current measuring transformer, the microcontroller being configured to extract an amplitude E of the reference voltage, an amplitude IB and an amplitude IF of the earth current and a phase shift φ between the reference voltage and the loop current iB and to calculate the earth impedance Zb at a determined frequency, the microcontroller also computing the contact voltage Uc at said determined frequency by the product of the earth impedance times the amplitude IF.

The invention provides an online measurement method and device for a grounding resistor. By using a meter clamping method, four pairs of potential transformers PT and current transformers CT are respectively connected on two anti-lightning wires at the left end and the right end of a rod tower. Voltage signals are sensed to the anti-lightning wires through the potential transformers; current signals are collected and measured, and the current signals are subjected to signal processing steps such as filtering and amplifying to obtain relation of feedback current and inductive voltage; and finally, the resistance of the grounding resistor of the rod tower to be measured is obtained by a special calculation method. With the adoption of the online measurement method and device, data measurement is carried out on the top of the rod tower. The online measurement method and device can be suitable for the rod tower containing a plurality of down leads, so that the anti-theft problem can be solved, and the grounding resistor can be rapidly and accurately measured.