Ieee recommended guide for measuring ground resistance and. Practical test methods and techniques are presented for measuring the electrical characteristics of grounding systems. This method is derived from the 4point method which is used for soil resistivity measurements the 3point method, called the fall of potential method, comprises the earth electrode to be measured and two other electrically independent test. 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.
Earth tester working principle your electrical guide. The contact resistance test is performed using two current connections for the injection, and two potential leads. To connect the metallic conductive parts of an electric appliance or installations to the earth ground is called earthing or grounding. It is essential that the probe be placed outside the sphere of influence of the ground electrode under test and the auxiliary earth to achieve the highest degree of accuracy when performing a 3pole ground resistance test or the effective areas of resistance will overlap and invalidate any measurements.
Getting down to earth 5 4 getting down to earth safety there is an inherent safety problem in earth resistance testing that requires care and planning by the user of the test set. Principles and testing methods of earth ground resistance. The resistance offered by the earth electrode to the flow of current into the ground is known as the earth resistance or resistance to earth. Pdf analysis of methods for measuring earth resistance and soil. If the current and potential probes both are far enough away from the electrode, that is, outside the influence of the electrode, the reading corresponds to the resistance of the. Fourterminal earth ground resistance and soil resistivity. Heavyduty clamp jaw stays in alignment and in calibration even in every day, onthejob industrial environments. And that the ground electrode is in firm contact with the earth. Topics addressed include safety considerations, measuring earth resistivity, measuring the power system frequency resistance or impedance of the ground system to remote earth, measuring the transient or surge impedance of the ground system to remote earth. Measurement of earth resistance by potential fall method.
Earth checking electrical earthing test proper practical. The resistance of the surrounding body of earth the ground electrode is surrounded by earth which conceptually is made up of concentric shells all having the same thickness. Figure 1 displays the fluke 1625 earthground tester. The most commonly used method of measuring the earth resistance of an earth electrode is the 3point measuring technique shown in figure 1. Measurement of the resistance of large earthelectrode systems. Normally, the voltage drop on the power feed side and ground side wires, connectors, and connections should not exceed 0. Ra r r earth ground resistance 300k ac resistance 300k dc low resistance 3k change item select start test display menu hc2 sp2 esp1 ec1 4 pole 3 pole 4 pole 2 pole 2 4 off 3 pole 1625earth ground tester st edw001. Test and measurement power catalogue the word megger is a registered trademark toil and trouble. This practical guide to earth ground resistance testing contains procedures commonly practiced by electrical contractors, electricians and maintenance workers of power utilities.
Simplified earth resistance measurement method this method is recommended where an earth resistance higher than 10 ohms is measured or where it is not possible to drive auxiliary earth bars. Hi friends, in this article, i am going to describe the earth tester working principle and method of earth resistance measurement by it. Numerically, it is equal to the ratio of the potential of the earth electrode to the current dissipated by it. A ground electrode provides the contact between the electrical system and the earth. Checking ground electrode impedance for commercial, industrial and residential buildings most facilities have grounded electrical systems, so that in the event of a lightning strike or utility overvoltage, current will find a safe path to earth. Megger det4t2 series 4terminal earth resistance and. Seasonal variation of earth resistance with an electrode of. Earth resistance value can be read directly from the scale. The resistance of the earth can be measured with the help of megger earth tester or earth megger earth tester working principle construction.
The information given uses simple language for easy understanding by the users and it is intended to be an educational tool. Actually, the earth is a relatively poor conductor of electricity compared to normal conductors like copper wire. Browse our top selling 16232 geo earth ground resistance meter, 16252 geo earth ground tester and the 1630 ground resistance meter today. Earth ground testers digital earth resistance testers. Microprocessor controlled universal earth resistance meter with fully auto mated measuring frequency selection process as well as automatic testing of probe and. It is the most accurate method but is limited by the fact that the ground tested is a single unit. The earth resistivity test ert of soil was carried out at site for studies work for andhrapradesh medtech zone amtz, vishakhapatnam, andhrapradesh. Circuits with high current draw cannot tolerate high resistance. Do not touch circuit connections and exposed metalwork of an installation or equipment under test. The fourwire kelvin dc voltage drop is the typical method used by microohmmeters for the contact resistance test, which ensures more accurate measurements by eliminating the own contact resistance and resistance of test leads. The measurement of earth resistance is made by the potential fall method. The fluke 16302 fc stakeless earth ground clamp is the kind of highquality, rugged tool you expect from fluke. Bureau of standards now nist developed the theory behind this test in 1915 see reference pg. The earth resistance mainly implies the resistance between the electrode and the point of zero potential.
It is the purpose of this guide to describe and discuss the present state of the technique of measuring ground resistance and impedance, earth resistivity, and potential gradients resulting from currents in the earth and the prediction of the magnitudes of ground resistance and potential gradients from scale model tests. The lower the earth resistance, the smaller the voltage funnels. Simple earth pit resistance test how to test it duration. The most common methods of measuring the resistance of an. An earth electrode and earth electrode resistance are defined in bs 7671 as. The next steps in insulation diagnostics details inside getting down to earth your complete guide to ground earth testing cable fault test vans, mobile and portable solutions local in more. At this level it is important to use test equipment that will minimize errors introduced by the test lead resistance andor contact resistance between the probe and the material being tested. Substation earth system injection testing swp page 3 of 14 standard work practice sp0510 ver 4 ergon energy corporation limited abn 50 087 646 062 sun protection to be used when working outdoors. In the figure shown below e is the earth electrode under rest, and a is an auxiliary earth electrode positioned so that two. Analysis of methods for measuring earth resistance and soil. Ground resistance depends on grounding electrode selection, soil resistivity, soil contact, and other factors. Built to withstand an entire spectrum of ground testing methods, flukes family of earth ground testers have been designed to be accurate, safe and easy to use. Broadly speaking, earth resistance is the resistance of soil to the passage of electric current.
Kc series test leads ground resistance testing covers the testing of earth electrodes and the measurement of soil resistivity. This paper first describes the general procedure for a single earth grounding point, and then describes a modified approach using a current probe for testing. Earth test and ground resistance testers for electricians. It is essential that the probe be placed outside the sphere of influence of the ground electrode under test and the auxiliary earth to achieve the highest degree of accuracy when performing a 3pole ground resistance test or the effective areas of resistance. Ensuring an effective earth system is essential in a telecommunications system, and megger is expert in earth testing having been there right from the start. The resistance area of the earth electrode is the area of the soil around which a voltage gradient is measured with a commercial instrument. Ground resistance is a measurement of the conducting connection between a grounding system and earth. Earth test and ground resistance testers for electricians ensuring an effective earth system is essential in a telecommunications system, and megger is expert in earth testing having been there right from the start. Test the grounding components of equipment in hardtoreach spaces, including areas that are indoors or fully paved and. The measuring procedure described below uses the universally. Do not leave the instrument connected to the system under test when not in use. Earth electrode conductive part, which may be embedded in the soil or in a specific conductive medium, e.
These days, megger offers topend systems for design and soil surveys as well as tough, easytouse testers for field engineers. An approximate value of earth resistance can be obtained by the two wire system which utilizes existing earthed equipment as shown in fig. The principles and methods of earth resistance testing covered in this section apply to. The latest circuit design permits the instrument to operate with the minimum of influence from earth. A practical guide to earth resistance testing weschler instruments. The resistance indicated by the test set is the resistance between the earth electrode and the potential probe.
Megger offers top end systems for design and soil surveys as well as tough easy to use testers for field engineers. Measuring resistance of g r ound electrodes 62% method the 62% method has been adopted after graphical consideration and after actual test. But, if the area of a path for current is large enough, resistance can be quite low and the earth can be a good conductor. This guide provides a general overview of the regulatory framework and approval process and explores the specific manufacturing responsibilities and test procedures associated with electrical safety testing. When determining the earth resistance, the voltage drop is measured which has been generated by a known and constant current applied to the earth resistance to be measured. Checking ground electrode impedance for commercial. A low resistance measurement is typically a measurement below 1.
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