Precise Measurement of Ground Resistance



I. Precise Measurement Method of Ground Resistance



For precise measurement of ground resistance, use a three-wire connection. After connecting the auxiliary ground rods and test leads, switch the function to measure resistanceR mode. Press the "TEST" button to start measurement. During measurement, the LED indicator flashes, the LCD counts down, and after measurement, the indicator turns off and the LCD displays the measured value.



Starting from the object under test, insert auxiliary ground rods into the earth in a straight line every 5 to 10 meters. Connect the ground test leads (red, yellow, green) from the meter'sH,S,E terminals to the auxiliary current electrodeH, auxiliary voltage electrodeS, and the ground electrode under testE respectively. As shown in the figure:



II. Simple Method for Measuring Ground Resistance



This method is a simple measurement method that does not use auxiliary ground rods. It uses an existing ground electrode with the smallest ground resistance value as the auxiliary ground electrode, and uses 2 simple test leads for connection (i.e., theH andS terminals are short-circuited).



Metal water pipes, fire hydrants, and other metal buried objects, common grounding of commercial power systems, or lightning protection grounding electrodes of buildings can be used to replace the auxiliary ground rodsH andS. During measurement, pay attention to removing the oxide layer at the connection point of the selected metal auxiliary grounding body.



The wiring for simple ground resistance testing is shown in the figure below; other operations are the same as for precise measurement.In the simple method of measuring ground resistance, the meter reading is the sum of the ground resistance value of the tested ground electrode and the ground resistance value of the commercial grounding body, that is:



RE=RX＋re



Where: RE is the meter reading value;



RX is the ground resistance value of the tested ground electrode;



re is the ground resistance value of the common grounding body such as the commercial power system.



Then, the ground resistance value of the tested ground electrode is:



RX=RE－re



When using the simple method to measure ground resistance, try to choose a grounding body with a small re value as the auxiliary ground electrode, so that the meter reading is closer to the true value. During measurement, please give priority to metal water pipes and fire hydrants as auxiliary ground electrodes.




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