Learn how insulation resistance test is done developed early in the 20th century, the insulation resistance ir test is the oldest and most widely used test for assessing the quality of insulation. Understanding insulation resistance testing pdf 0712 technical assistance 800 34391. Proof test, spot test, time resistance testing, step level voltage test, polarization index pi test, dielectric absorption ratio dar test. Pdf measurement of winding resistance and insulation. Typically, they offer facilities for polarisation index pi, dielectric absorption ratio dar, dielectric displacement dd. Apr 25, 2016 insulation resistance testing is used as a quality control measurement. The measurement of insulation resistance is a common routine test performed on all types of electrical wires and cables. A guide to low resistance testing test equipment depot. Test results are dependent on the temperature of the insulating material and the humidity of the surrounding environment at the time of the test. Megger guide to electrical insulation testing pdf instrumart. The test method is determined by the type of equipment being tested and the reason for testing.
Insulation resistance tester et600 klein tools for. Insulation resistance testing is used as a quality control measurement. Whichever test you choose, we recommend you measure resistance both phasetophase and phasetoframe if possible. Today megger offers the finest line of 5 kv, 10 kv and 15 kv dc insulation resistance testers available anywhere. The measured resistance indicates the condition of the insulation between two conductive parts. Insulation resistance testing applied technical services. When measuring the insulation resistance of a solar panel that is generating electricity, remember not to apply the standard method for measuring the circuits insulation resistance andbear in mind that the photovoltaic cell voltage affects the test voltage and that there is the risk of damaging other equipment if the array is grounded. Section 7 of the ansineta standard for acceptance testing specifications for electrical power equipment and systems may be reproduced and used on a cut and paste basis for the particular type of equipment to be tested. To avoid dangerous electrical hazards, we offer insulation resistance testing in our certified labs.
Regular insulation resistance testing is one of the most cost effective, nondestructive methods of identifying ageing in electrical equipment. The test measures the insulation resistance between the phases andor between phase and ground. Also, acceptable values of insulation resistance depend upon the equipment youre testing. A megger testing device is shown in the figure below. Megger is also called as a megaohmmeter and is a device used for the testing of insulation resistance of a cable. The complete guide to electrical insulation testing. The test method is determined by the type of equipment being tested. For good insulation, the resistance usually reads in the megohm range.
Threephase dualvoltage motor insulation resistance testing. The international electrical testing association neta specification maintenance testing specifications for electrical power distribution equipment and. At a, the insulation resistance decreases due to aging and dust accumulation. Understanding insulation resistance testing jm test systems. Apr 12, 2014 good insulation shows this charge effect over a time period much longer than the time required to charge the capacitance of the insulation. The megger insulation tester is essentially a highrange resistance meter ohmmeter with a builtin directcurrent generator. Insulation resistance test values for electrical distribution.
Standard for acceptance testing specifications for electrical. Insulation resistance measurement is based on ohms. A guide to diagnostic insulation testing above 1 kv. On the other hand, when the resistance level drops as the voltage level increases, its usually an indication that the insulation is aging. Record the insulation resistance, temperature, humidity, and equipment designation. Pdf insulation resistance testing introduction robert. It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs. The insulation resistance meter is also called megger, shaker, and tramegger.
If resistance values decrease substantially when tested at higher voltage levels, this shouldserve as a warning that insulation quality may be deteriorating due to dirt, moisture. With a little recordkeeping and common sense, however, you can get a good picture of the insulation condition from values that are only relative. This procedure must be continued for subsequent tests to accurately determine if the rate of insulation breakdown is occurring at an abnormal rate. It is also has more types of currents than some users realize. Insulation resistance testing is carried out by applying a constant voltage to the equipment under test while measuring the flowing current. The insulation resistance meter is mainly composed by three parts. As your insulation starts to age and is exposed to environmental hazards such as extreme temperatures, humidity, and chemical compounds, you may experience unexpected deterioration. Insulation that is thoroughly dry, clean, and without physical damage should provide roughly the same resistance values despite changes in test voltage levels. Insulation resistance testing methods there are several types of insulation resistance test in use today. Insulation resistance testing is a nondestructive test procedure. It involves applying the test voltage for a short time 30 or 60 seconds and noting the insulation resistance reading at.
Typically, they offer facilities for polarisation index pi, dielectric absorption ratio dar, dielectric displacement dd, step voltage sv and ramp tests. Test performed so performed to know the insulation resistance value is known as megger test. Insulation resistance testing guide chauvin arnoux. Timeresistance testing method this method is fairly independent of temperature and often. The sharp fall at b indicates there was an insulation fault. The first is a dc high voltage generator to generate a constant current high voltage. High power test and diagnostics combination for medium voltage cables. The megger technical library provides access to a range of additional content and resources such as technical guides, application notes and more. Insulation resistance ir is among the most common motor test. Understanding insulation resistance testing pdf 0206 rev. Insulation resistance testing of low voltage cables in the field.
A step voltage test involves testing the insulation at two or more voltages and comparing the results. Most can be classified as spot reading shorttime tests, timeresistance tests, or step voltage tests. Insulation resistance is used to verify the integrity of the insulation material, whether cable insulation or motorgenerator winding insulation. Performing time resistance tests on large switchgear, transformers, bushings, motors, and cables especially at higher voltages require high insulation resistance ranges and clean, consistent test voltages. Other ieee standards that include information on insulation resistance measurement are listed in clause 2. Pdf insulation resistance testing of low voltage cables in. A low resistance measurement is typically a measurement below 1. Its multiple test voltages make it the ideal tool for many troubleshooting, commissioning, and preventative maintenance applications.
Regular insulation resistance testing is one of the most cost effective, nondestructive methods of identifying ageing in. At c, the fault has been repaired rewinding of the motor so the insulation resistance has returned to. Monitor the insulation resistance during the test to ensure that reading is not linear and does not increase exponentially as the test voltage increases. The summary is that if the insulation resistance test of transformer between high voltage windings and the transformer body is less than 300 mega ohm indicates on the weakness of insulation that means contact between.
Insulation resistance of new transformer should be greater than 1 giga ohm and old transformer should greater than 300 mega ohm. Fluke 1507 insulation resistance tester the fluke 1507 is a versatile, compact, handheld insulation tester for advanced industrial and electrical insulation testing. Pdf testing and simulation of motor insulation system under. As a production test, this test is often used as a customer acceptance test, with minimum insulation resistance per unit length often specified by the customer. 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. This type of test is a form of preventative maintenance. What is the insulation resistance meter and how to test it. Insulation resistance test and polarization index test. Most can be classified as spot reading shorttime tests, time resistance tests, or step voltage tests. The insulation resistance test consists in measuring the insulation resistance of a device under test, while phase and neutral are short circuited together. Standard test methods for dc resistance or conductance of.
Aug 01, 2019 megger is also called as a megaohmmeter and is a device used for the testing of insulation resistance of a cable. In hv machines and winding are likely to be affected by moisture and contamination. The following sections of the ansineta standard for acceptance testing specifications for. In its most basic form, an insulation resistance test is done with a handcrank meter that measures megohms. Either condition could indicate insulation failure, poor insulation, andor improper test connections. Insulation resistance testing applications and how they apply to your testing needs consider the equipment to be tested, test voltage requirements, the testing environment, other possible uses, the experience level of those using the tester and measurement safety. The insulation resistance test is the second test required by the electrical safety testing standards. If the insulation resistance falls below an accepted user dictated value, or falling rapidly over time, then cable.
Pdf this study deals with the effect of humidity and contamination of salt on insulation resistance and polarization index. A quick oneoff insulation resistance measurement can sometimes provide useful data, but modern insulation resistance test sets have much more to offer. Both insulation resistance test ir value test and polarization index test pi value test are conducted on hv machine to determine service condition of the insulation. With over 60% of equipment failures being ascribed to insulation breakdown, it is a key area to monitor. Ieee recommended practice for testing insulation resistance. Historically, many field electricians use the somewhat arbitrary standard of 1 megohm per kv. The measured resistance has to be higher than the indicated limit from the. Good insulation will show a relatively consistent resistance reading regardless of the voltage applied. Insulation resistance testing basics plant services. Insulation resistance test insulation tester electrom. The insulation resistance ir test also commonly known as a megger is a spot insulation test which uses an applied dc voltage typically either 250vdc, 500vdc or 1,000vdc for low voltage equipment. Insulation resistance testing applications and how they apply to your testing needs consider the equipment to be tested, test voltage requirements, the testing environment, other possible uses, the experience level of those using the tester and measurement safety features of the insulation resistance tester. The et600 is a multifunction megohmmeter capable of producing 125v, 250v, 500v, and v test voltages for insulation resistance measurements up to 4000m also tests acdc voltages up to v with automatic ranging true rms technology. After 1 min, you should read and record the resistance value.
Maintenance insulation resistance testing can be performed on a regular basis, and the collected data used to indicate if the conductor insulation is deteriorating over time. Standard for acceptance testing specifications for. Insulation resistance testing test equipment depot. The megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. Understanding insulation resistance testing pdf 0712. Troubleshooting with insulation resistance test instruments. When performing insulation resistance testing, you must maintain consistency. The insulation resistance test is an electrical test which uses a certain type and level of voltage 500v d. Insulation resistance testing is performed when troubleshooting electric motors and related equipment. Time resistance testing method this method is fairly independent of temperature and often. Insulation resistance testing introduction insulation resistance testers can be used to determine the integrity of windings or cables in motors, transformers, switchgear, and electrical installations.
Figure 2typical megger test instrument hookup to measure insulation resistance. Dielectric absorption test the dielectric absorption or timeresistance test is an extension of the insulation resistance test where instead of a spot test, the testing device is applied to the insulation for up to 10 minutes. Larger insulation systems will show a steady decrease. The test method is determined by the type of equipment being tested and the reason for test ing.
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