The grounding resistance meter is a commonly used measuring instrument. It is widely used in the measurement of the grounding resistance of electrical equipment and transmission lines in the fields of power, lightning protection, communication, transportation, etc. It is an indispensable tool for electrical safety inspection and completion acceptance of grounding projects . With the continuous development of science, the measurement method of grounding resistance is also continuously improving. At the current stage, there are mainly three types of grounding resistance meters: ① Analog grounding resistance meter, which is a more traditional instrument, and its basic principle is The three-point voltage drop method is used. The measuring method is to insert two auxiliary test poles on the ground on the same side of the measured ground electrode. The three are on the same straight line. Turn the crank at a certain speed to make the motor inside the resistance meter generate electrical energy, generate current between the electrodes at both ends, and form a loop, thereby generating a voltage between the measured electrode and the auxiliary electrode, thereby calculating the measured ground electrode The resistance. Its disadvantage is that it is hand-cranked, and the output voltage is not stable enough to affect the measurement result. ②Digital grounding resistance tester, its measuring methods are two-wire method, three-wire method and four-wire method. The wiring method of the three-wire method is the same as the analog ground resistance meter, but its stability is far superior to the former. The two-wire method does not require auxiliary grounding piles. You can use the neutral line of the water pipe and AC outlet as auxiliary grounding. The four-wire method is improved on the basis of the three-wire method. In the case where low-value measurement and wiring have a great influence on the measurement result, the error can be effectively eliminated and the accuracy can be improved. ③Clamp earth resistance tester, its measurement method includes single clamp method and double clamp method, based on two-pole method measurement. The jaw part of the clamp meter contains voltage and current coils. The voltage coil provides an excitation signal, which induces a potential E on the circuit under test to generate a loop current I. Measure E and I to get R, which is simply a full circuit The embodiment of Ohm's law in practice. It is a novel measurement tool, convenient and fast, without the need for auxiliary test poles, just a clip to the geodesic line, you can get the results. In addition, it also has the advantage that the resistance of the device can be measured online, unlike traditional instruments where the power is cut or the ground is disconnected. However, it still has major limitations. Its measured value is actually the entire loop resistance including the tested ground resistance, and it is susceptible to interference from external electromagnetic fields. It cannot measure the resistivity of the soil and cannot completely replace the traditional ground. The resistance meter measures the grounding resistance of a single grounding body.
It can be seen that the grounding resistance test technology has developed to the present stage. The clamp-shaped grounding resistance meter and the traditional grounding resistance meter have their own advantages and disadvantages. In the actual measurement process, the user must select the best instrument according to the actual situation. There is still much room for development in the measurement method of grounding resistance.