The megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. These days, megger offers topend systems for design and soil surveys as well as tough, easytouse testers for field engineers. This method is the most commonly used for measuring soil resistivity, which is important for designing electrical grounding systems. All of the new megger earth testers can perform this test and unlike some instruments, no external linking on the instrument is required. Fault current from a grounded electrical system can be dissipated effectively once it has cleared the immediate hurdle of transferring from the electrode into the surrounding soil and to infinite earth.
It is stiff near the zero end of the coil and becomes very weak near the infinity end of the spring. It is powered by an internal rechargeable battery which has a long usage period. If the resistance of the insulation is high, the pointer of the moving coil deflects towards the infinity, and if it is low, then the pointer indicates zero resistance. The det23 can be used on large or more complex earth systems, which include communications earth systems and difficult test environments. Suitable applications where there is doubt about a particular application, reference should be made to the advice and guidance contained in the publication, getting down to earth which is available from megger, part number 21500 072.
Page there is an inherent safety problem in earth resistance. Megger makes electrical test equipment to help you install, improve efficiency and extend the life of assets and cable networks at high, medium and low voltage. Bureau of standards now nist developed the theory behind this test in 1915 see reference pg. 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. The megger det family of test instruments offers a unique solution to the measurement of earth or ground electrode rod resistance and soil resistivity.
Getting down to earth 9 8 getting down to earth equipment can also be damaged similarly by overvoltages caused by highresistance ground systems. 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. Buy megger det3td earth ground resistance tester ireland. These instruments induce a test current into earth systems and measure ground resistance in multi ground installations without needing to disconnect the ground. Megger has published a book titled getting down to earth, a practical guide to earth resistance testing. For good insulation, the resistance usually reads in the megohm range. A practical guide to earth resistance testing getting down to earth. Factors influencing requirements for a good grounding system in an industrial plant or other facility that requires a grounding system, one or more of the following must be carefully considered see fig. Understanding insulation resistance testing pdf 0206 rev. Getting down to earth a practical guide to earth resistance testing earth testing and resistivity measuring requires sensitive equipment and sophisticated calculations. The det3ta provides 2 and 3wire measurements and offers an analogue display. Benefits simple to use, one touch operation auto switch off to save battery power rugged, weatherproof case large, clear lcd indicators show if reading may be. Two nos of wire leads for connecting megger with electrical external system to be tested.
The empirical relation as below gives the recommended minimum value for ir, its unit being mega ohm m. The det23 can be used on large or more complex earth systems. A digital display to show ir value in digital form. Guide to clampon ground testing 3 clampon testing versus fall of potential testing fall of potential testing as mentioned, clampon, or stakeless, ground testing is a relatively. Det62d threeterminal ground resistance tester det62d. The megger det3td ground tester is used to test for inherant dangers and potential cost implications of disconection of the earth spike. Megger leads are connected to lv bushing studs and transformer tank earth point to measure insulation resistance ir value in between the lv windings and earth. Function up scroll down enter ir port on off 00k 0 0m g v 0g t 00g t k m 00m m 000v 500v 2500v to ground 5 k, 5 w resistor insulation step voltage test figure 37. Electrical test equipment power station to plug megger.
The det3tc will perform the traditional 3pole measurements like other earth testers. Please refer to meggers booklet getting down to earth for further information on fall of potential tests and soil resistivity tests. Fourterminal earthground resistance and soil resistivity tester. Convert the 4 ft to centimeters to obtain a in the formula. The family has seven variants supporting 2, 3 and 4wire measurements. An insulation step voltage test is a test that creates electrical stress on internal insulation cracks to reveal aging or damage not found during other motor insulation tests. We would be pleased to have a representative call on you to discuss your application. Please refer to meggers booklet getting down to earth for further information. Getting down to earth is available, covering many other test techniques. The resistance of the earth can be measured with the help of megger earth tester or earth megger earth tester working principle. When the test switch is closed to the left, the current passing through the electrode under test from the testing generator and the voltage drop between the electrode under test and the potential spike are used as inputs to the log ratio computer. D e t 3 2 digital earth tester test equipment depot.
The det range of instruments can be used in agricultural locations as per iec 615575. The megger det3td ground tester features a large selector switch makes selection of 2 pole or 3 pole test easy with gloved hands. Getting to know the mto product overview 300330 the megger transformer ohmmeter is a lineoperated, fieldportable instrument designed specifically to measure the dc resistance of all types of magnetic windings safely and accurately. Megger working principle types history uses of megger. Alternatively visit the megger earth testing website. The earth megger is essentially a direct reading ohmmeter and it has a hand driven generator which supplies the testing current. D e t 3 2 digital earth tester description the megger det32 digital earth tester is a compact instrument designed to measure earth electrode resistance and soil resistivity. A practical guide to earth resistance testing pdf free download. This technique is done with an earth resistance tester, often called a megger. Switches use to select electrical parameters ranges. The result will cause either be the clamp low symbol appearing or an unexpectedly high reading. Earth testing kits including suitable test spikes and leads and a book describing several testing techniques entitled getting down to earth are also available. These days, megger offers topend systems for design and soil surveys as well as tough, easy to use testers for field engineers.
Stakeless earth ground testing new det14c and det24c clamps getting around any challenge introduction megger has been designing, manufacturing and selling earth ground testers for well over 50 years. In megger, the combined action of both the voltage coils v 1 and v 2 are considered. The spring compresses the low resistance portion and opens the high resistance of the spring, which is the. Fourterminal earth ground resistance and soil resistivity. Meggers det4tc2 is a portable, lightweight instrument used for easy measurements of earthing. From years of experience in supplying instruments for the tests involved, megger can provide advice to help you make specific tests.
A megger should be used the same way that a hipot or a power factor set would be used with the red positive lead being the hot and the black negative lead being the return. Thank you for purchasing the megger earth ground tester. The instrument is suitable for the testing of earth electrodes and measuring earth resistivity. Det3td digital ground tester det3td digital ground tester. Getting down to earth a megger guide to earth testing 21500072 ordering information electrical specifications ingress protection. Getting down to earth manual avtm25ta det62d threeterminal ground resistance tester ordering information test equipment depot 800. How to test three phase ac motors learning electrical. It was dr george tagg who pioneered earth testing at megger, and since megger has been at the forefront of innovative development and design. Getting down to earth 3 table of figures safety fig. Insulation resistance failure of an electric motor is one of the first signs that the motor is about to fail. A practical guide to earth resistance testing megger on photo. Voltage source ammeter 17 basic test methods for earth resistance megger instruments for earthresistance tests in clude.
The megger insulation tester is essentially a highrange resistance meter ohmmeter with a builtin directcurrent generator. The megger is the instrument uses for measuring the resistance of the insulation. But the advantage of the earth that is, the planet itself, or the immediate portion of it is simply that there is so much of it. The megger det14c and det24c ground resistance clamp testers represent a new generation of earthground clampon resistance testers. The complete guide to electrical insulation testing. In this method, four smallsized electrodes are driven into the earth at the same depth and equal distance apart in a straight line and a measurement is taken. Getting down to earth 11 added salt percent by weight of moisture resistivity, ohmcm 0. For a three phase motor, insulation resistance is usually measured between each motor winding or phase and between each motor phase and motor frame earth using an insulation tester or megger. There is an inherent safety problem in earth resistance testing that requires care and planning by the user of the test set. 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.
The megger det3td design makes the fitting of shorting links to perform 2 pole tests a thing of the past. It can be used to test in accordance with bs 7430 earthing, bsen62305. The resistance of the earth can be measured with the help of megger earth tester or earth megger. Digital ground testers det4td2 and det4tr2 digital ground. Hi friends, in this article, i am going to describe the earth tester working principle and method of earth resistance measurement by it. It is capable of performing 2, 3 and 4 point testing with variable frequency, attached rod technique via optional clamp sold separately, stakeless testing again via optional clamp, leakage current and ground noise voltage measurements. Earth testing det14c and det24c technical getting down to earth a practical guide to earth resistance testing. The instrument uses the fourterminal method of measurement, in which the resistance of the current circuit does not affect the reading. This guide makes these processes easier to understand for both large and small ground systems, with detailed studies of various relevant testing methods. The device is being used since 1889, popularity raised during 1920s since the long back device is same in its uses and purpose of testing, few real improvements appeared in recent years with its design and quality of tester. The return lead senses the current that is being carried by the device under test and compares it to the voltage being applied to calculate a resistance.
Megger clamp on ground testing guide pdf instrumart. The megger det14c and det24c ground resistance clamp testers represent a new generation of earth ground clampon resistance testers. Timeresistance testing method this method is fairly independent of temperature and often. A practical guide to earth resistance testing the word megger is a registered trademark. Instruction manual for transformer ohmmeter dc winding. Its predominant use is the measurement of the dc resistance of all types of. Troubleshooting with insulation resistance test instruments. If you are unclear as to the meaning of sphere of influence, more information can be found in the megger publication getting down to earth, part number 21500 072. Earth tester working principle your electrical guide. In other words, if the distance a between the electrodes is 4 ft, you obtain the average earth resistivity to a depth of 4 ft as follows. The det23 automatic earth test instrument is designed to measure earth electrode resistance and soil resistivity, with highly accurate results. Megger det23 digital ground resistance tester manual pdf. Fourterminal earthground resistance and soil resistivity.
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