Manufacturers and users should be aware, however, that. Example of the variation of insulation resistance over a period of years. Thermal insulation is an important part of commercial roofing assemblies, with polyisocyanurate foam, or polyiso, being the most common form today. Pdf measurement of winding resistance and insulation. This recommended practice describes the theory, procedure, and interpretation of the insulation resistance test. 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. This article provides a table of insulation values and properties for various insulation materials useful in procedures to measure or calculate heat loss in a building, defines thermal terms like btu and calorie, provides measures of heat transmission in materials, building insulation design data, and heat loss in a building. If the ohms values are below the values in the table above, either the windings are damaged or down to earth or the motor lead is damaged or is faulty. Time resistance testing method this method is fairly independent of temperature and often. The conductors are usually made of copper or aluminum.
Sound insulation performance of aerated concrete walls. Significant if application is outdoors and high intensity indoors. Insulation resistance of dielectric materials under environmental testing c. When performing insulation resistance testing, you must maintain consistency. Resistance values must be temperature compensated when ir is tracked over time. The measurement of insulation resistance constitutes a directvoltage test and must be restricted to a value appropriate to the voltage rating of the winding and the basic insulation condition. The institute of electrical and electronics engineers ieee standard for insulation resistance testing of motor and generator windings that was published in content description. This is particularly important in the case of small, lowvoltage machines, or wet windings. The test measures the insu lation resistance between the phases andor between phase and ground. The test method is determined by the type of equipment being tested.
Its scale unit is megaohm, which itself has a high voltage power supply. Insulation resistance of dielectric materials under. Understanding insulation resistance testing pdf 0712. Sound insulation performance of aerated concrete walls barbara szudrowicz1, genowefa zapotoczna sytek2, piotr g barowski2 1 building research institute in warsaw 2 the institute of ceramics and building materials concrete research center cebet in warsaw abstract. Damaged or contaminated insulation will will mask absorption with current leakage, keeping resistance low, identifying a potential problem. Recommended test voltages and minimum insulation values.
Insulation resistance testing of low voltage cables in the. You can also determine the r value of the material in conjunction. Insulation resistance testing test equipment depot. All motors motor maintenance insulation resistance readings the values below are for copper conductors. 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. Insulation resistance testing is a nondestructive test procedure. The insulation resistance meter is a special instrument for measuring the maximum resistance value, insulation resistance, absorption ratio and polarization index. Heltzel 2 1estecesa keplerlaan 1, po box 299, nl2201az noordwijk zh, netherlands.
The insulation resistance is considered adequate if each circuit reaches the required value without electrical loads connected. Measured ir values are functions of insulation dryness. By injecting a known dc voltage lower than the voltage for dielectric testing and then measuring the current flowing, it is very simple to determine the value of the resistance. Hipot tester with insulation resistance test diverse functions memory function up to 100 test conditions used in ac and dc hipot testing and insulation resistance testing, such as the test voltage, judgment value and test time, can be stored with a speci. Longer runs will result in lower insulation resistance values. International electrical testing association neta provides recommended representative test. It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs. The same material measured at a lower temperature can exhibit significantly higher resistance, and vice versa. At c, the insulation resistance value after the motor has been rewound. Hipot test current, leakage current and insulation resistance. Recently, there was a discussion in the ieee email safety forum about the relationship between the hipot test current, leakage current, and insulation resistance. This value reflects the electrical resistance of the insulation layer surrounding each conductor and is a direct reflection of the cables electrical condition and. Insulation resistance testing guide chauvin arnoux.
The insulation resistance test is an electrical test which uses a. Ieee recommended practice for testing insulation resistance of rotating machinery 1. The value of insulation resistance ir is strongly affected by the temperature of the material. Secondly measure insulation resistance between low voltage windings and high voltage windings. If connected to a drop cable, the check the drop cable for damage andor the splice for damage of poor connections. For instance, you can store the name of an applied safety standard and the. Larger insulation systems will show a steady decrease. Understanding insulation resistance testing pdf 0206 rev.
These values must be considered tentative and relative, subject to experience with the time resistance method over a period of time. C2 values should compare well with the nameplate or amongst similar bushings. The insulation resistance test is the second test required by the electrical safety testing standards. In particular, the question was whether the hipot test and the insulation resistance test could be combined into a single measurement. Consult the insulation resistance test equipment manual or manufacturer for insulation resistance testing procedures and recommended safety guidelines. Pdf insulation resistance testing of low voltage cables.
Insulation resistance is defined as the resistance to current leakage through and over the surface of the insulation material surrounding a conductor. Good insulation allows for an increase of resistance ohms over time, showing the charge effect over a time period longer than the capacitance of the insulation. Insulation resistance of new transformer should be greater than 1 giga ohm and old transformer should greater than 300 mega ohm. Currently the attic is insulated with fiberglass insulation having an r value of 8 r8 question. Individuals or organizations who manufacture rotating machines. Insulation and evaporative resistance of clothing for. Ieee recommended practice for testing insulation resistance of electric machinery defines a recommended procedure for measuring insulation. Higher temperature leads to lower insulation resistance.
Diagnostic insulation testing at voltages above 1 kv is an area that is less familiar to many electrical maintenance personnel. Understanding the value of electrical testing for power. Insulation resistance test insulation tester electrom. Pdf this paper consist the specification of transformer and its procedure of. These results would be satisfactory for equipment with. It recommends minimum acceptable values of insulation resistance for. The test measures the insulation resistance between the phases andor between phase and ground. Understanding insulation resistance testing pdf0712 technical assistance 800 34391. Use these values in the absence of consensus standards dealing with insulation resistance tests. Insulation resistance testing of low voltage cables in the field. Section 2 insulation materials and properties mp4 l. With a little recordkeeping and common sense, however, you can get a good picture of the insulation condition from values that are only relative.
Megger mit1020 10kv insulation resistance testers are all. At b, the sharp drop indicates an insulation failure. For good insulation, the resistance usually reads in the megohm range. The megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. Measurement of winding resistance and insulation resistance of 3 phase 11 kv 433 v, 16kva oil cooled type transformer conference paper pdf available august 20 with 5,441 reads how we. Listing of conditions of insulation as indicated by dielectric absorption ratios. A 1954 camera is ideal for all applications in the building, electrical maintenance and. Insulation resistance measurement is based on ohms law. Large values may cause inaccuracy by heating the winding and.
Megger guide to electrical insulation testing pdf instrumart. In principle, the value of the insulation resistance is very high but not infinite, so by. 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. Curve b shows same values corrected to 20c see page. Motor electrical insulation testing page 1 introduction insulating material with high electrical resistance is used to confine electrical current to a desired path through conductors and to isolate the conductors from ground and from each other. Use these values in the absence of consensus standards dealing with insulationresistance tests. The complete guide to electrical insulation testing. The temperature must also be above the dew point for accurate comparisons of results. Cable insulation resistance measurements made during. Flame spread and smoke developed ratings are of vital importance. R value is the measure of thermal resistance used in the building and construction industries. Understanding insulation resistance testing aemc instruments.
If aluminum conductor drop cable is used, the resistance will be higher. Autoclaved aerated concrete aac has been universally applicable in the construction of internal and external walls. Hipot tester with insulation resistance test tos9200series. The measurement of insulation resistance is a common routine test performed on all types of electrical wires and cables. The hot collar results are analyzed from watts loss. As energy costs have risen, understanding the exact insulation value of this material i. 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. Rvalues for concrete masonry walls exposed both sides. What is the insulation resistance meter and how to test it. Because the conductors adjacent to the ground conductor only have one layer of insulation, those conductors will have lower insulation resistance and the megger values will be lower. R value measures the ratio of the temperature difference across an insulator concrete masonry wall and the heat flux heat transfer per unit area per unit time. The following sections of the ansineta standard for acceptance testing specifications for.
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