Earth loop impedance testing is essential since if a live conductor is accidentally connected to an earth conductor in a faulty appliance or circuit, the resulting short-circuit current to earth can easily be high enough to cause electric shock or generate enough heat to start a fire.
Another method is to measure the earth loop impedance with a loop test instrument that supplies a test current suﬃciently low not to trip the RCD, such as 15 mA. Determining earth loop impedance by calculation. Regulation 612.9 permits earth loop impedance to be determined by means other than measurement.
Zs - earth fault loop impedance of the circuit tested Ze - earth fault loop impedance external to the supply (R1+R2) - Sum of the resistance of Line and Earth for the tested circuit. The Earth Fault Loop test sequence: This is a live test so extra care is advised! Step 1.
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earth resistance testing The word ‘Megger’ is a registered trademark. Getting Down to Earth 1 Introduction Nothing is quite so common or abundantly available throughout the world as the earth’s soil. We are more apt to think of earth as something to be
An earth loop impedance test is conducted to make sure that, if a fault occurs in an electrical circuit, the fault current will strong be enough to set off the circuit protection. If a fault current is left undetected, circuits can overheat and catch on fire. Electricity takes the path of least resistance to the ground.
Earth Resistance for Electrical Grounding Systems. The simplest and somewhat misleading idea of a good ground for an electrical system is a section of iron pipe driven into the earth with a wire conductor connected from the pipe to the electrical circuit (Figure 1).. A Practical Guide To Earth Resistance Testing – Megger (on photo: Four-terminal earth/ground resistance and soil resistivity ...
Measuring earth resistance with fall of potential method (photo credit: eblogbd.com) This method is generally not suited to large earthing installations, as the stake separations needed to ensure an accurate measurement can be excessive, requiring the use of very long test leads (refer to Table 1).. Normally, the outer test electrode, or current test stake, is driven into the ground 30 to 50 ...
The three-point method is the most thorough and reliable test method; used for measuring resistance to earth of an installed grounding electrode. The standard used as a reference for fall-of-potential testing is IEEE Standard 81 : Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Grounding System.
Loop testing demystified. Of all the tests that contractors routinely perform on electrical installations, earth loop impedance testing creates the most confusion and uncertainty. Why is the test needed and which test method is it best to use? Simon Wood of Megger answers these and other frequently asked questions.