byjuvc
09-13-2006, 10:45 AM
Sir,
Can anyone give me a clear picture regarding Earth resistance measurement. I have been following the following procedure :
My aim is to measure the earth resistance at a 11 kv Distribution Sub station . I disconnect the earth connection wires from the transformer Neutral. The earth resistance measurement kit consists of a meter and four electrodes(for Wenners 4 electrode method) but we are using only two electrodes. Each electrode is 2 feet long. The first electrode is connected to the C1( current terminal) of the Meter and is usually driven into a ground at a distance of 10 meters from the main earth electrode of the station. The second electrode is connected to P1 (Voltage) measurement terminal of the meter and is driven into the ground at a distance of approximately 6 meters from the main earth electrode of the station. Now the other two terminals of the meter namely C2 and P2 are shorted and connected to the Earth wire connected to the main earth electrode of the station. All the three electrodes are in a straight line. I understand that one electrode is used to inject current and the second electrode is for voltage measurement. So we get V/I = R i.e the earth resistance. But I am unable to understand why the voltage measurement is done at a distance of 0.62 d . Is the above method correct or something is wrong because at times we are getting earth resistance as high as 9 ohms? if anyone can tell me any site where this is explained in detail that would also be helpful.
Thanks
Byju
Can anyone give me a clear picture regarding Earth resistance measurement. I have been following the following procedure :
My aim is to measure the earth resistance at a 11 kv Distribution Sub station . I disconnect the earth connection wires from the transformer Neutral. The earth resistance measurement kit consists of a meter and four electrodes(for Wenners 4 electrode method) but we are using only two electrodes. Each electrode is 2 feet long. The first electrode is connected to the C1( current terminal) of the Meter and is usually driven into a ground at a distance of 10 meters from the main earth electrode of the station. The second electrode is connected to P1 (Voltage) measurement terminal of the meter and is driven into the ground at a distance of approximately 6 meters from the main earth electrode of the station. Now the other two terminals of the meter namely C2 and P2 are shorted and connected to the Earth wire connected to the main earth electrode of the station. All the three electrodes are in a straight line. I understand that one electrode is used to inject current and the second electrode is for voltage measurement. So we get V/I = R i.e the earth resistance. But I am unable to understand why the voltage measurement is done at a distance of 0.62 d . Is the above method correct or something is wrong because at times we are getting earth resistance as high as 9 ohms? if anyone can tell me any site where this is explained in detail that would also be helpful.
Thanks
Byju