A method for measuring a grounding resistance

Abstract

The application provides a grounding resistance measuring device and a method thereof, which comprises a grounding resistance measuring meter and two test lines; the grounding resistance measuring meter is provided with an output pole and an input pole, one end of one of the two test lines is connected with the output pole, and the other end is connected with a grounding pole inserted into the ground; one end of the other of the two test lines is connected with the input pole, and the other end is connected with a measuring pole inserted into the ground, so as to form a test loop; the grounding resistance measuring meter obtains the resistivity in a unit distance, and the resistivity is used to calculate the grounding resistance value in combination with the distance between the grounding pole and the measuring pole. The test is a two-point test method, which can shorten the length of the test line, reduce the weight of the test equipment and facilitate the detection and carrying, compared with a three-point or four-point test method.

Description

Technical Field

[0001] This invention relates to the field of power technology, and in particular to a method for measuring grounding resistance. Background Technology

[0002] Grounding is the precise connection of a part of equipment to the earth through a grounding device. In power networks, grounding is one of the most widely used electrical safety measures. Whether it is high-voltage or low-voltage power grids, AC or DC, transmission and distribution equipment, or users, different grounding measures are used for different purposes. The main functions of grounding are to prevent electric shock to people, damage to equipment and lines, fire prevention, lightning strike prevention, static electricity damage prevention, and to ensure the normal operation of the power system. Among them, grounding resistance is the resistance encountered when current flows from the grounding device into the earth and then through the earth to another grounding body or diffuses to a distance. The grounding resistance value reflects the degree of good contact between the electrical device and the "earth" and reflects the scale of the grounding network. The grounding resistance value must meet the standard requirements to play a protective role and prevent accidents.

[0003] Currently, two types of grounding resistance testers are used: megohmmeters and digital ones. Most employ a three-point connection method to measure grounding resistance. This method requires three test leads of 5 meters, 20 meters, and 40 meters respectively, and the resistance value is measured by applying voltage. This method is inconvenient due to the excessively long leads, time-consuming operation, and difficulty in transporting such long cables. Furthermore, during megohmmeter testing, the voltage is unstable, and the output voltage is related to the hand cranking speed, resulting in less accurate measurement results. Summary of the Invention

[0004] The purpose of this invention is to provide a grounding resistance measurement method to solve the technical problem of how to conveniently measure grounding resistance and improve the accuracy of measurement results.

[0005] The present invention provides a method for measuring grounding resistance, comprising a grounding resistance measuring meter and two test leads;

[0006] The grounding resistance measuring meter is equipped with an output pole and an input pole. One end of one of the two test lines is connected to the output pole, and the other end is connected to the grounding electrode inserted into the ground. One end of the other test line is connected to the input pole, and the other end is connected to the measuring electrode inserted into the ground, forming a test circuit.

[0007] The grounding resistance meter includes a battery, a constant voltage circuit, a switching circuit, a resistor, a control chip, a voltage sampling module, and a display screen. The battery provides operating power, the constant voltage circuit outputs voltage U, and the control chip controls the switching circuit to turn the test circuit on or off. The voltage sampling module samples the voltage across the resistor when the test circuit is on. The control chip also calculates the resistivity per unit distance based on the voltage sampling results from the voltage sampling module. The display screen shows the resistivity, which is used to calculate the grounding resistance value in conjunction with the actual distance between the two grounding electrodes.

[0008] Preferably, the control chip is specifically used to control the switching circuit to periodically turn the test circuit on or off;

[0009] The voltage sampling module is specifically used to sample the voltage across the output terminal and the input terminal multiple times during each conduction cycle of the test circuit to obtain voltage sampling results for multiple conduction cycles. The voltage sampling result for each conduction cycle includes multiple sampled voltage values.

[0010] The control chip is also used to calculate the average voltage value U based on the voltage sampling results of multiple conduction cycles of the voltage sampling module. L According to I L =U 平 / R L and the average voltage value U L and the resistance R of the resistor L Calculate I L And according to R=UU 平 / I L And the resistivity R obtained per unit distance.

[0011] This invention also proposes a grounding resistance measurement method, implemented based on the aforementioned grounding resistance measurement device, the method comprising the following steps:

[0012] Connect one end of one of the two test lines to the output electrode and the other end to the grounding electrode inserted into the ground. Connect one end of the other test line to the input electrode and the other end to the measuring electrode inserted into the ground to form a test circuit.

[0013] Start the grounding resistance meter to perform the measurement;

[0014] The grounding resistance value is calculated based on the resistivity R per unit distance displayed by the grounding resistance meter, combined with the actual distance between the two grounding electrodes.

[0015] Preferably, the step of calculating the grounding resistance value based on the resistivity R per unit distance displayed by the grounding resistance meter, combined with the actual distance between the two grounding electrodes, includes:

[0016] Calculate the multiple of the distance between the grounding electrode and the measuring electrode to the unit distance;

[0017] The grounding resistance value is obtained by multiplying the resistivity R per unit distance by the specified factor.

[0018] Preferably, the method further includes:

[0019] With the grounding electrode as the center, the measuring electrode moves in a circle around the center for a certain distance to one or more other positions, and the measurement is repeated to obtain one or more corresponding grounding resistivity.

[0020] Implementing this invention has the following beneficial effects:

[0021] (1) The testing method was changed from the four-point method and the three-point method to the two-point testing method;

[0022] (2) Shorten the test line length. The test line consists of two 5-10 meter long wires.

[0023] (3) A constant voltage circuit is used to maintain a constant applied voltage and ensure measurement accuracy;

[0024] (4) Based on the resistivity within the measurement distance, the grounding resistance at a greater distance, such as 20 meters, can be calculated;

[0025] (5) Within a short distance, the resistivity is tested from multiple angles to better understand the soil resistivity around the grounding electrode, which can guide the grounding device to be installed more reasonably to meet the construction specifications.

[0026] (6) Reduce the weight of the testing equipment and make it easier to carry and test. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the structure of a grounding resistance measuring device according to an embodiment of the present invention.

[0029] Figure 2 This is an equivalent circuit diagram of a grounding resistance measuring device in an embodiment of the present invention. Detailed Implementation

[0030] See Figure 1-2 One embodiment of the present invention provides a grounding resistance measuring device, including a grounding resistance measuring meter and two test leads;

[0031] The grounding resistance measuring meter is equipped with an output pole and an input pole. One end of one of the two test lines is connected to the output pole, and the other end is connected to the grounding electrode inserted into the ground. One end of the other test line is connected to the input pole, and the other end is connected to the measuring electrode inserted into the ground, forming a test circuit.

[0032] The grounding resistance meter includes a battery, a constant voltage circuit, a switching circuit, a resistor, a control chip, a voltage sampling module, and a display screen. The battery provides operating power, the constant voltage circuit outputs voltage U, and the control chip controls the switching circuit to turn the test circuit on or off. The voltage sampling module samples the voltage across the resistor when the test circuit is on. The control chip also calculates the resistivity per unit distance based on the voltage sampling results from the voltage sampling module. The display screen shows the resistivity, which is used to calculate the grounding resistance value in conjunction with the actual distance between the two grounding electrodes.

[0033] Preferably, the control chip is specifically used to control the switching circuit to periodically turn the test circuit on or off;

[0034] The voltage sampling module is specifically used to sample the voltage across the output terminal and the input terminal multiple times during each conduction cycle of the test circuit to obtain voltage sampling results for multiple conduction cycles. The voltage sampling result for each conduction cycle includes multiple sampled voltage values.

[0035] See Figure 2 The equivalent circuit has two parts of resistance in the entire conduction loop: one part is the resistance R of the resistor. L The other part is the resistance R per unit measurement distance, also known as resistivity. The control chip is also used to calculate the average voltage value U based on the voltage sampling results of multiple conduction cycles of the voltage sampling module. L According to I L =U 平 / R L and the average voltage value U L and the resistance R of the resistor L Calculate I L And according to R = (UU 平 ) / I L And the resistivity R obtained per unit distance.

[0036] Specifically, the switching circuit is composed of MOSFETs, and the control chip controls their on / off states at a frequency of 250Hz. Therefore, in this embodiment, one major cycle consists of 250 on-time cycles. The average voltage value U calculated at the end of this embodiment is... L It is calculated based on the voltage sampling results of 250 conduction cycles in one large cycle, with 4 voltage samplings performed in one conduction cycle.

[0037] Another embodiment of the present invention also proposes a grounding resistance measurement method, implemented based on the above-described grounding resistance measurement device, the method comprising the following steps:

[0038] Step S1: Connect one end of one of the two test lines to the output electrode and the other end to the grounding electrode inserted into the ground. Connect one end of the other test line to the input electrode and the other end to the measuring electrode inserted into the ground to form a test circuit.

[0039] Step S2: Start the grounding resistance measuring meter to perform the measurement;

[0040] Step S3: Calculate the grounding resistance value based on the resistivity R per unit distance displayed by the grounding resistance meter and the actual distance between the two grounding electrodes.

[0041] Preferably, step S3 includes:

[0042] Calculate the multiple of the distance between the grounding electrode and the measuring electrode to the unit distance;

[0043] The grounding resistance value is obtained by multiplying the resistivity R per unit distance by the specified factor.

[0044] Preferably, the method further includes:

[0045] With the grounding electrode as the center, the measuring electrode moves in a circle around the center for a certain distance to one or more other positions, and the measurement is repeated to obtain one or more corresponding grounding resistivity.

[0046] Specifically, in this embodiment, by moving another measuring electrode to the center of the grounding electrode, the soil resistivity around the grounding electrode can be quickly measured. For grounding points with poor resistivity consistency, other technical measures are required to prevent the grounding resistance from failing to meet the specifications.

[0047] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A grounding resistance measuring device, characterized in that, Includes a grounding resistance meter and two test leads; The grounding resistance measuring meter is equipped with an output pole and an input pole. One end of one of the two test lines is connected to the output pole, and the other end is connected to the grounding electrode inserted into the ground. One end of the other test line is connected to the input pole, and the other end is connected to the measuring electrode inserted into the ground, forming a test circuit. The grounding resistance meter includes a battery, a constant voltage circuit, a switching circuit, a resistor, a control chip, a voltage sampling module, and a display screen. The battery provides operating power, the constant voltage circuit outputs voltage U, and the control chip controls the switching circuit to turn the test circuit on or off. The voltage sampling module samples the voltage across the resistor when the test circuit is on. The control chip also calculates the resistivity per unit distance based on the voltage sampling results from the voltage sampling module. The display screen shows the resistivity, which is used to calculate the grounding resistance value in conjunction with the actual distance between the two grounding electrodes. The control chip is specifically used to control the switching circuit to periodically turn the test circuit on or off; The voltage sampling module is specifically used to sample the voltage across the output terminal and the input terminal multiple times during each conduction cycle of the test circuit to obtain voltage sampling results for multiple conduction cycles. The voltage sampling result for each conduction cycle includes multiple sampled voltage values. The control chip is also used to calculate the average voltage value U based on the voltage sampling results of multiple conduction cycles of the voltage sampling module. L According to I L =U 平 / R L and the average voltage value U L and the resistance R of the resistor L Calculate I L And according to R=UU 平 / I L And the resistivity R obtained per unit distance.

2. A method for measuring grounding resistance, characterized in that, Based on the grounding resistance measuring device of claim 1, the method includes the following steps: Connect one end of one of the two test lines to the output electrode and the other end to the grounding electrode inserted into the ground. Connect one end of the other test line to the input electrode and the other end to the measuring electrode inserted into the ground to form a test circuit. Start the grounding resistance meter to perform the measurement; The grounding resistance value is calculated based on the resistivity R per unit distance displayed by the grounding resistance meter, combined with the actual distance between the two grounding electrodes. The calculation of the grounding resistance value based on the resistivity R per unit distance displayed by the grounding resistance meter, combined with the actual distance between the two grounding electrodes, includes: Calculate the multiple of the distance between the grounding electrode and the measuring electrode to the unit distance; The grounding resistance value is obtained by multiplying the resistivity R per unit distance by the specified factor.

3. The grounding resistance measurement method according to claim 2, characterized in that, The method further includes: With the grounding electrode as the center, the measuring electrode moves in a circle around the center for a certain distance to one or more other positions, and the measurement is repeated to obtain one or more corresponding grounding resistivity.

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