CN110456164B - Grounding resistance measuring device and method - Google Patents
Grounding resistance measuring device and method Download PDFInfo
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- CN110456164B CN110456164B CN201910952276.2A CN201910952276A CN110456164B CN 110456164 B CN110456164 B CN 110456164B CN 201910952276 A CN201910952276 A CN 201910952276A CN 110456164 B CN110456164 B CN 110456164B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/20—Measuring earth resistance; Measuring contact resistance, e.g. of earth connections, e.g. plates
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Abstract
The invention discloses a ground resistance measuring device, which comprises an MCU (microprogrammed control Unit) main control module, an alternating current generating module, a power frequency interference shunt module, a ground resistance testing module and a collecting module, wherein the ground resistance testing module is used for testing the ground resistance through an internal relayThe on-off of the ground resistor testing module forms three working modes, namely a reference checking mode, a standard checking mode and a ground resistance testing mode, the voltage values of the ground resistor testing module without load, the additional standard resistor and the ground resistance are respectively detected, and then the result is sent to the MCU main control module to be calculated to obtain the measured ground resistance value; the invention also discloses a measuring method of the grounding resistance measuring device, which respectively carries out three times of measurement according to U = IR + U0And respectively obtaining the deviation voltage and the actual current so as to obtain the measured earth resistance value. The method and the device firstly pass the reference verification and the standard verification when the ground resistance measurement is carried out, thereby effectively avoiding the influence of temperature change on the measurement result.
Description
Technical Field
The invention relates to the technical field of lightning protection, in particular to a device and a method for measuring ground resistance.
Technical Field
For lightning protection devices, it is very important that the ground resistance is acceptable or not. The measurement of the grounding resistance is strictly carried out under the condition that the grounding body is isolated from the load, but most of the existing equipment runs for 24 hours, and cannot be disconnected from the grounding body for safety, so that the interference of power frequency current and voltage on the grounding body in the actual measurement process when the load exists, and the interference error can be caused on the measurement result; in addition, measurement personnel technical factors can cause measurement errors. The difficulty of the on-line measurement of the grounding resistance is also existed at present. The grounding resistance on-line measuring device carries out filtering and equipotential processing on an interference source at an input and output circuit part; in addition, the grounding resistance changes along with the change of the soil temperature (the change is small), meanwhile, the change of the ground surface temperature can cause the change of parameters of a semiconductor device of a measuring instrument (the change is relatively large), so that the measurement error is caused, the condition is called temperature drift, the temperature drift can cause inaccurate actual measurement of the grounding resistance, the current solution of the temperature drift is to adopt a compensation circuit in a constant current source power supply mode on the power supply of an electric bridge, but due to the reasons of manufacturing process and the like, the resistances in the electric bridge are unequal, and zero position output exists. Therefore, even if the power supply method of the constant current source is adopted, a certain temperature error still exists. The grounding resistance on-line measuring device solves the problem of temperature drift by adopting a standard resistance matching mode; moreover, the grounding resistance on-line measuring device standardizes the installation requirements from the use and installation specifications, and avoids the measurement error of technical factors. In conclusion, the grounding resistance online measuring device solves the online measurement problem and the measurement error from three aspects.
Disclosure of Invention
In order to solve the above technical problems, the present invention provides a ground resistance measuring device capable of avoiding the influence of temperature drift on the actual measured value of the ground resistance, the specific content of which is as follows:
a grounding resistance measuring device comprises an MCU main control module, an alternating current generating module, a power frequency interference shunting module, a grounding resistance testing module and an acquisition module; the grounding resistance inspection module comprises a P pole, a C pole, an E pole, a P1 pole, a C1 level pole and an E1 pole, wherein the P1 pole and the C1 pole are respectively inserted into the ground through metal probes, the E1 pole is connected to the leading-out end of a grounding grid to be inspected, the P pole is connected with the power frequency interference shunt module, the C pole is connected with the alternating current generation module, the E pole is connected with the ground wire, a first switch is connected between the P pole and the P1 pole, a second switch is connected between the C pole and the C1 pole, a third switch is connected between the E pole and the E1 pole, a standard resistance is connected between the C pole and the E pole, a fourth switch is connected between the P pole and the C pole, a fifth switch is connected between the C pole and the E pole, the standard resistance inspection module is connected between the E pole and the C pole through a series-connection sixth switch, and the grounding resistance inspection module respectively forms a reference check mode through the on-off of each switch, The ground resistance detection system comprises three working modes, namely a standard verification mode and a ground resistance detection mode, wherein the voltage value of a ground resistance detection module under the condition of no load is measured in the standard verification mode, the voltage value of the ground resistance detection module is measured when a standard resistance is added in the standard verification mode, and the voltage value of the ground resistance detection module is measured when the ground resistance is detected in the ground resistance detection mode; the alternating current generating module is connected with the MCU main control module and provides constant high-frequency alternating current for the grounding resistance testing module, the power frequency interference shunting module is connected with the collecting module and filters power frequency interference, the collecting module is connected with the MCU main control module, and the collecting module sends the measuring result to the MCU main control module to be processed to obtain the resistance value of the measuring ground resistance.
Further, when the ground resistance inspection module is in the reference verification mode, the first switch, the second switch, the third switch and the sixth switch are all turned off, and the fourth switch and the fifth switch are turned on.
Further, when the ground resistance inspection module is in the standard verification mode, the first switch, the second switch, the third switch and the fifth switch are all turned off, and the fourth switch and the sixth switch are turned on and off.
Further, when the grounding resistance inspection module is in a grounding detection mode, the first switch, the second switch and the third switch are all closed, and the fourth switch, the fifth switch and the sixth switch are opened.
Further, the first switch, the second switch, the third switch, the fourth switch, the fifth switch and the sixth switch are all relays.
Furthermore, the alternating current generation module comprises a comparator and a voltage-current converter, the comparator is connected with the voltage-current converter, the comparator converts the pulse signals generated by the MCU main control module into alternating voltage signals and transmits the alternating voltage signals to the voltage-current converter, and the voltage-current converter converts the alternating voltage signals into alternating current signals.
Further, the power frequency interference shunt module comprises a filter circuit, and the filter circuit filters a signal of power frequency 50 HZ.
In addition, the invention also provides a measuring method of the grounding resistance measuring device, which comprises the following steps:
providing constant high-frequency alternating current for a grounding resistance inspection module through an alternating current generation module;
step two, the grounding resistance inspection module is switched to a reference inspection mode, and the collection module obtains the deviation voltage value U of the grounding resistance inspection module in a no-load state0；
Step three, switching the grounding resistance inspection module to a standard calibration mode, and acquiring the additional standard resistance R by the acquisition module1Standard voltage value U of grounding resistance inspection module under state1；
Switching the grounding resistance detection module to a grounding detection mode, and acquiring an actual voltage value U of the grounding resistance detection module in a grounding state by the acquisition module;
and step five, the acquisition module transmits the voltage values obtained in the step two, the step three and the step four to the MCU main control module, and the MCU main control module calculates the resistance value of the measured earth resistance R according to the voltage values and the standard resistance value.
Further, the resistance value of the ground resistor R measured in the fifth step is calculated as follows:
s1, according to ohm' S law, under the condition that the current is constant, the voltage and the resistance in the circuit are in a linear relation, and an equation U is established0；
S2, substituting the resistance value of the standard resistor in the step three and the standard voltage value measured in the standard verification mode into the equation in the step S1 to obtain U1＝I*R1+U0The actual current value in the circuit is obtained, I ═ U1-U0)/R1；
And S3, substituting the actual voltage value measured in the step four and the actual current value obtained in the step S2 into the equation of S1 to obtain the resistance value of the measured ground resistance R, wherein R is (U-U)0)*R1/(U1-U0)。
Further, before the acquisition module acquires the voltage in the second step, the third step and the fourth step, the power frequency signal of 50HZ is filtered through the power frequency interference shunt module.
Has the advantages that: according to the ground resistance detection method, the ground resistance detection module is divided into a reference verification mode, a standard verification mode and a ground resistance detection mode, before the ground resistance value is detected, the interference of deviation voltage is eliminated through the reference verification mode, and then the actual current is obtained through calculation of a measured value of the standard verification mode, so that the ground resistance value is calculated. The ground resistance measurement of the invention needs to be carried out three times of measurement, the deviation voltage and the actual current at the current time are obtained every time, and the time interval between the three times of measurement is short, so the influence of temperature drift on the measurement can be effectively eliminated, the obtained ground resistance measurement value is more accurate, the three modes of the ground resistance detection module of the invention are simple to switch, and the power frequency interference shunt module is utilized to filter the power frequency and the second harmonic, thereby realizing the on-line monitoring of the ground resistance, and being easy to be used in production practice.
Drawings
FIG. 1 is a block diagram of a ground resistance measuring device according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a ground resistance verification module in a baseline verification mode in accordance with an embodiment of the present invention;
FIG. 3 is a schematic diagram of a ground resistance verification module in a standard verification mode in accordance with an embodiment of the present invention;
fig. 4 is a schematic diagram of the ground resistance verification module in the ground detection mode in an embodiment of the present invention.
Reference numerals: 1-a first switch; 2-a second switch; 3-a third switch; 4-a fourth switch; 5-a fifth switch; 6-sixth switch.
Detailed Description
The invention is further illustrated with reference to the accompanying drawings and specific examples.
According to fig. 1, a ground resistance measuring device comprises an MCU main control module, an alternating current generating module, a power frequency interference shunt module, a ground resistance testing module and a collecting module, wherein the alternating current generating module is respectively connected with the MCU main control module and the ground resistance testing module, the MCU main control module provides constant high-frequency alternating current for the ground resistance testing module, the alternating current generating module comprises a comparator and a voltage-current converter, the comparator is connected with the voltage-current converter, the comparator converts pulse signals generated by the MCU main control module into alternating voltage signals and transmits the alternating voltage signals to the voltage-current converter, and the voltage-current converter converts the alternating voltage signals into alternating current signals. The power frequency interference shunt module is respectively connected with the acquisition module and the grounding resistance inspection module, and comprises a filter circuit for filtering low-frequency signals with the frequency of 50-150 HZ in the circuit. Because the interference of low-frequency signals can exist in the actual ground resistance detection environment, the high-frequency current is introduced into the detection circuit, the low-frequency signals are filtered through the power frequency interference shunt module, and the obtained detection data are more accurate.
The ground resistance measuring device disclosed by the invention adopts a three-level method to measure ground resistance, as shown in fig. 2-4, the ground resistance inspection module comprises a P pole, a C pole, an E pole, a P1 pole, a C1 pole and an E1 pole, a first switch 1 is connected between the P pole and the P1 pole, a second switch 2 is connected between the C pole and the C1 pole, a third switch 3 is connected between the E pole and the E1 pole, a standard resistor is connected between the C pole and the E pole, a fourth switch 4 is connected between the P pole and the C pole, a fifth switch 5 is connected between the C pole and the E pole, the standard resistor is connected between the E pole and the C pole through a sixth switch 6 in series, and the switches all adopt relays. In the process of ground resistance detection, the P1 pole and the C1 pole are respectively inserted on the ground through metal probes, and the E1 pole is connected to the leading-out end of the to-be-detected ground screen; the P electrode is a voltage electrode and is connected with the power frequency interference shunt module, a voltage signal generated by the ground resistance inspection module is transmitted to the power frequency interference shunt module, the C electrode is a current electrode and is connected with the alternating current generation module to receive the current provided by the alternating current generation module, the E electrode is a grounding electrode, and the E electrode is connected with a ground wire.
The ground resistance testing module is divided into three working modes, namely a reference testing mode, a standard testing mode and a ground resistance testing mode, by the on-off state of the relay, when the ground resistance testing module is in the reference testing mode, as shown in fig. 2, the first switch 1, the second switch 2, the third switch 3 and the sixth switch 6 are all switched off, the fourth switch 4 and the fifth switch 5 are switched on, a loop is formed between the C pole and the E pole, and the result measured by the acquisition module is the voltage value without external load. When the ground resistance inspection module is in the standard inspection mode, as shown in fig. 3, the first switch 1, the second switch 2, the third switch 3 and the fifth switch 5 are all turned off, the fourth switch 4 and the sixth switch 6 are turned on, a loop is formed between the C pole and the E pole, and the result measured by the acquisition module is a voltage value when the standard resistor is used as an external load. When the grounding resistance inspection module is in the grounding detection mode, as shown in fig. 4, the first switch 1, the second switch 2 and the third switch 3 are all closed, the fourth switch 4, the fifth switch 5 and the sixth switch 6 are opened, a loop is formed between the C pole and the ground to the E pole, and the result measured by the acquisition module is the voltage value when the grounding is performed. The MCU main control module further comprises a communication interface, the MCU main control module is connected with a remote communication device through the communication interface, the acquisition module is connected with the MCU main control module, the acquisition module sends the measurement result to the MCU main control module to be processed to obtain the resistance value of the measuring ground resistance, and the MCU main control module sends the result to the remote communication device.
The invention also provides a measuring method of the grounding resistance measuring device, which comprises the following steps:
providing constant high-frequency alternating current for a grounding resistance inspection module through an alternating current generation module;
step two, the grounding resistance inspection module is switched to a reference inspection mode, and the collection module obtains the deviation voltage value U of the grounding resistance inspection module in a no-load state0；
Step three, switching the grounding resistance inspection module to a standard calibration mode, and acquiring the additional standard resistance R by the acquisition module1Standard voltage value U of grounding resistance inspection module under state1；
Switching the grounding resistance detection module to a grounding detection mode, and acquiring an actual voltage value U of the grounding resistance detection module in a grounding state by the acquisition module;
and step five, the acquisition module transmits the voltage values obtained in the step two, the step three and the step four to the MCU main control module, and the MCU main control module calculates the resistance value of the measured earth resistance R according to the voltage values and the standard resistance value.
The voltage drop produced by adding a standard circuit to the external resistor according to ohm's law is a value that is directly proportional to the value of the resistor. When the external resistance is 0, the theoretically measured voltage value should be 0V, but since the circuit has a certain discrete type, it is impossible to reach the absolute 0V, and there is a fixed voltage deviation U when the external resistance is 00When the reference verification is adopted, the voltage is measured after the external resistor is short-circuited, and the value isU0Here, we refer to the reference deviation, then the voltage and the resistance of the whole measuring circuit are in a linear relationship no matter what external resistance type load is applied, so the calculation process for measuring the resistance value of the ground resistor R in the step five is as follows:
s1, according to ohm' S law, under the condition that the current is constant, the voltage and the resistance in the circuit are in a linear relation, and an equation U is established0；
S2, substituting the resistance value of the standard resistor in the step three and the standard voltage value measured in the standard verification mode into the equation in the step S1 to obtain U1＝I*R1+U0The actual current value in the circuit is obtained, I ═ U1-U0)/R1；
And S3, substituting the actual voltage value measured in the step four and the actual current value obtained in the step S2 into the equation of S1 to obtain the resistance value of the measured ground resistance R, wherein R is (U-U)0)*R1/(U1-U0)。
Further, before the acquisition module acquires voltage in the second step, the third step and the fourth step, the power frequency signal of 50-150 HZ is filtered through the power frequency interference shunt module.
The grounding resistance measuring device and the grounding resistance measuring method disclosed by the invention have the advantages that when the grounding resistance is measured, the influence of temperature change on the measuring result is effectively avoided through the reference calibration mode and the standard calibration mode, and the three modes of the grounding resistance testing module in the grounding resistance measuring device are skillfully switched, so that the grounding resistance measuring device and the grounding resistance measuring method are easy to apply to production practice.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (9)
1. A grounding resistance measuring device comprises an MCU main control module, an alternating current generating module, a power frequency interference shunting module, a grounding resistance testing module and an acquisition module; the grounding resistance detection module is characterized by comprising a P pole, a C pole, an E pole, a P1 pole, a C1 level pole and an E1 pole, wherein the P1 pole and the C1 pole are respectively inserted on the ground through metal probes, the E1 pole is connected to the leading-out end of a grounding grid to be detected, the P pole is connected with a power frequency interference shunt module, the C pole is connected with an alternating current generation module, the E pole is connected with the ground wire, a first switch is connected between the P pole and the P1 pole, a second switch is connected between the C pole and the C1 pole, a third switch is connected between the E pole and the E1 pole, a standard resistor is connected between the C pole and the E pole, a fourth switch is connected between the P pole and the C pole, a fifth switch is connected between the C pole and the E pole, the standard resistor is connected between the C pole and the E pole through a sixth switch in series, and the grounding resistance detection module respectively forms a reference check mode through the on-off of the switches, The ground resistance detection system comprises three working modes, namely a standard verification mode and a ground resistance detection mode, wherein the voltage value of a ground resistance detection module under the condition of no load is measured in the standard verification mode, the voltage value of the ground resistance detection module is measured when a standard resistance is added in the standard verification mode, and the voltage value of the ground resistance detection module is measured when the ground resistance is detected in the ground resistance detection mode; the alternating current generating module is connected with the MCU main control module and provides constant high-frequency alternating current for the grounding resistance testing module, the power frequency interference shunting module is connected with the collecting module and filters power frequency interference, the collecting module is connected with the MCU main control module, and the collecting module sends the measuring result to the MCU main control module to be processed to obtain the resistance value of the measuring ground resistance.
2. The grounding resistance measuring device according to claim 1, wherein when the grounding resistance checking module is in the reference checking mode, the first switch, the second switch, the third switch and the sixth switch are all open, and the fourth switch and the fifth switch are closed.
3. The ground resistance measuring device according to claim 1, wherein when the ground resistance checking module is in the standard verification mode, the first switch, the second switch, the third switch and the fifth switch are all turned off, and the fourth switch and the sixth switch are turned on.
4. The ground resistance measuring device according to claim 1, wherein when the ground resistance checking module is in the ground resistance detection mode, the first switch, the second switch and the third switch are all closed, and the fourth switch, the fifth switch and the sixth switch are open.
5. The earth resistance measuring device of claim 1, wherein the ac current generating module comprises a comparator and a voltage-current converter, the comparator is connected to the voltage-current converter, the comparator converts the pulse signal generated by the MCU master control module into an ac voltage signal and transmits the ac voltage signal to the voltage-current converter, and the voltage-current converter converts the ac voltage signal into an ac current signal.
6. The earth resistance measuring device of claim 1, wherein the power frequency interference shunt module comprises a filter circuit, and the filter circuit filters a power frequency 50HZ signal.
7. A measuring method using the ground resistance measuring device according to any one of claims 1 to 6, comprising the steps of:
providing constant high-frequency alternating current for a grounding resistance inspection module through an alternating current generation module;
step two, the grounding resistance inspection module is switched to a reference inspection mode, and the collection module obtains the deviation voltage value U of the grounding resistance inspection module in a no-load state0；
Step three, switching the grounding resistance inspection module to a standard calibration mode, and acquiring the additional standard resistance R by the acquisition module1Standard voltage value U of grounding resistance inspection module under state1；
Switching the grounding resistance detection module to a grounding detection mode, and acquiring an actual voltage value U of the grounding resistance detection module in a grounding state by the acquisition module;
and step five, the acquisition module transmits the voltage values obtained in the step two, the step three and the step four to the MCU main control module, and the MCU main control module calculates the resistance value of the measured earth resistance R according to the voltage values and the standard resistance value.
8. The method for measuring a ground resistance measuring device according to claim 7, wherein the step of calculating the resistance value of the ground resistance R measured in the step five is as follows:
s1, according to ohm' S law, under the condition that the current is constant, the voltage and the resistance in the circuit are in a linear relation, and an equation U is established0；
S2, substituting the resistance value of the standard resistor in the step three and the standard voltage value measured in the standard verification mode into the equation in the step S1 to obtain U1＝I*R1+U0The actual current value in the circuit is obtained, I ═ U1-U0)/R1；
And S3, substituting the actual voltage value measured in the step four and the actual current value obtained in the step S2 into the equation of S1 to obtain the resistance value of the measured ground resistance R, wherein R is (U-U)0)*R1/(U1-U0)。
9. The method of claim 7, wherein a power frequency signal of 50HZ is filtered by a power frequency interference shunt module before the voltage is collected by the collection module in the second step, the third step and the fourth step.
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| JP4652236B2 (en) * | 2005-01-25 | 2011-03-16 | 長谷川電機工業株式会社 | Ground resistance measuring device |
| JP2011226983A (en) * | 2010-04-22 | 2011-11-10 | Hioki Ee Corp | Grounding resistance meter and grounding state discrimination method |
| CN203572883U (en) * | 2013-05-13 | 2014-04-30 | 上海大帆电气设备有限公司 | Novel intelligent frequency-conversion large-current grounding impedance measuring instrument |
| CN206348391U (en) * | 2016-12-19 | 2017-07-21 | 深圳远征技术有限公司 | A kind of earth resistance device |
| CN107831369B (en) * | 2017-12-19 | 2020-07-03 | 成都信息工程大学 | Grounding resistance monitor with self-checking and correcting functions |
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