Jun 28, 2017 this video will show you how to perform the megger test in a easy way. With proper installation, commissioning, protection and timely maintenance during operation, the users should. Insulation resistance testing test equipment depot. Medium voltage electrical testing transworld electric. Insulation resistance test of transformer is one of the most important transformer tests we can perform this test at factory or site this test can be classified under type test, routine test, precommissioning and commissioning tests, periodic maintenance transformer tests you can know more about transformer testing and its. Feb 08, 2015 a routine test of transformer is mainly for confirming operational performance of individual unit in a production lot. The goal was to perform pf test at different temperatures and compare itc and tcf against real measured. The following tests are routinely conducted in the field on the transformer. It helps to detect deterioration of insulation in order to schedule repair work such as. The insulation resistance test is the second test required by the electrical safety testing standards.
Standard for acceptance testing specifications for electrical. For three phase transformers, we need to test winding l1,l2,l3 with substitute earthing for delta transformer or winding l1,l2,l3 with. Insulation resistance testing guide chauvin arnoux. Measure the winding temperature, where possible, and oil temperature at the time of the test. The voltage, we apply for measurement of insulation resistance, is direct voltage. Troubleshooting with insulation resistance test instruments. All transformers are subjected to the following routine tests. After 1 min, you should read and record the resistance value.
Megger guide to electrical insulation testing pdf instrumart. Because of that, insulation resistance can also be referred as 1 minute insulation resistance or 10 minute insulation resistance depending upon the duration of the test. Generally, you connect two leads positive and negative across an insulation barrier. Basics, maintenance, and diagnostics vii contents continued page 4. The easytouse software interface, powerdb, minimizes time required to learn how to use the delta4000 and perform these tests correctly. Recommended test voltages for routine maintenance insulation resistance tests of equipment rated to 4,160v and above.
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 dielectric test of transformer electrical4u. The test measures the insulation resistance between the phases andor between phase and ground. It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs. In the absence of manufacturers published data, use table 100. The test method is determined by the type of equipment being tested and the reason for test ing. Nov 17, 2019 insulation dielectric test of transformer november 17, 2019 february 24, 2012 by electrical4u the dielectric test of transformer is generally performed in two different steps, likewise, separate source voltage withstand test and induced voltage withstand test of transformer, which we have discussed one by one below. For primary side, apply voltage depending on rating of voltage rating of vt. When performing insulation resistance testing, you must maintain consistency. Meanwhile, dielectric frequency response dfr testing delivers a very reliable and accurate moisture assessment of the insulation and the conductivity of the oil. Aug 16, 2014 it is unnecessary to perform the insulation resistance test of transformer per phasewise in a threephase transformer. Technical specification for startup and commissioning of. Home technical articles dos and donts when measuring insulation resistance of a transformer insulation resistance measurement this test is performed at or above rated voltage to determine if there are low resistance paths to ground or between winding.
These tests are performed with the circuit deenergized. Ieee recommended practice for testing insulation resistance. Before conducting a transformer winding resistance test, it is important to observe all safety warnings and take proper precautions. For good insulation, the resistance usually reads in the megohm range. Perform electrical performance tests on potential transformer circuits. Test value a bolt torque levels are checked in accordance with u. Excitation current test insulating fluid dielectric tests insulation pf test insulation resistance test ttr test. Recommended test voltages for routine maintenance insulationresistance tests of equipment rated to 4,160v and above. The test measures the insu lation resistance between the phases andor between phase and ground. The following sections of the ansineta standard for acceptance testing specifications for. If the transformer is new, the resistance test also serves as a verification of the manufacturers work. Transformer insulation temperature was determined by. Transformers regulate the voltage in circuits, but in some cases these can go bad and cause a circuit to not.
Insulation resistance the latest test tools from the testing experts. It is the product of the test voltage, the test current and the cosine of theta. Apply voltage in accordance with manufacturers published data. Insulation resistance tools are critical to a preventative maintenance program, and a staple for troubleshooting any number of utility, industrial and commercial applications. Because electrical insulation will exhibit dynamic behavior during the course of your test. Perform a high potential test on the vacuum bottles of each pole test each function of the digital relay insulation resistance test on a pole to pole, and pole to the ground contact resistance test on each poles contacts, and connections secondary test to. Aemc instruments testing methods and interpretation of the results shorttime or spotreading measurement this is the simplest method. Apply vdc for 1 min oneminute insulation resistance test to lowvoltage cables 1 kv or less and use a clampon ammeter, dmm, megohmmeter, or imm to measure the insulation resistance. Regular testing of the insulation on an installation or machine is therefore a useful way of monitoring this type of deterioration so you can act before total failure occurs. Principle of insulation testing and influencing factors insulation resistance measurement is based on ohms law.
Dos and donts when measuring insulation resistance of a transformer. Transformers are an electrical component that transmit electrical energy between at least two circuits. Dos and donts when measuring insulation resistance of a. Routine tests are carried out on every unit manufactured. The winding insulation resistance test is a dc high voltage test used to determine the dryness of winding insulation system. Electrical transformer test equipment solutions from megger.
The index is derived from calculating measurement of winding electrical insulation resistance. Find here insulation testing and continuity, power protection, power transformer testing, power cable infrastructure, cable fault location, general electrical. It is unnecessary to perform the insulation resistance test of transformer per phasewise in a threephase transformer. This test is performed at or above rated voltage to determine if there are low resistance paths to ground or. Hence, it is recommended that the dc resistance be measured on all onload and offload taps prior to energizing. Apr 08, 2018 perform an insulation resistance test on each conductor in the cable. Perform insulation resistance tests winding to winding and each winding to ground. Understanding insulation resistance testing aemc instruments. Ensure that all equipment to be tested is properly grounded and treat all highvoltage power equipment as energized until proven otherwise by using the proper lockouttagout procedures.
Meggering insulation resistance testing of drytype. Understanding insulation resistance testing jm test systems. The megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. Installation measurements should be filed for future reference 2.
Chapter 3 troubleshooting with insulation resistance test instruments 25 dielectric absorption test a dielectric absorption test is an insulation resistance test that checks the absorption characteristics of wet or contaminated insulation. The primary test methods used to assess the condition of the active insulation components in transformers and bushings, on site, include. Primary voltage rating test voltage in kv dc up to 1kv 1. Before removing test leads from the transformer winding and discharge the winding under test for minimum of 30 seconds or until the insulation resistance test set indicates no charge. The polarization index pi is used to determine the fitness of a motor or generator for use. Various routine test of power transformerpart1 february 8. The insulation resistance test is of value for future comparison and also for determining if the transformer is to be subjected to the applied voltage test. This dielectric test is intended to check the the ability of main insulation to earth and between winding.
Pdf measurement of winding resistance and insulation. Timeresistance testing method this method is fairly independent of temperature and often. Ensure that no leakage paths between phases or transformer body. The transformer was allowed to cool for hours to bring the oil and windings temperature closer winding resistance test was performed to determine the high and low side temperatures top oil temperature, top and bottom radiator and ambient temperature were monitored through out the test duration. With a little recordkeeping and common sense, however, you can get a good picture of the insulation condition from values that are only relative. Home technical articles dos and donts when measuring insulation resistance of a transformer insulation resistance measurement this test is performed at or above rated voltage to determine if there are low resistance paths to ground or between winding to winding as a result of winding insulation deterioration. The insulation between the current transformer windings and windings to ground should be checked for dielectric strength while performing a comprehensive ct test. Perform electrical performance test on control power transformer circuits. To test the insulation integrity you will need a megohmmeter or hipot rated to produce the specified maximum test voltage. Insulation resistance testing is a nondestructive test procedure. Pdf this paper consist the specification of transformer and its procedure of. Ir values are taken between the windings collectively as because all the windings on hv side are internally connected together to form either star or delta and also.
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. It is unnecessary to perform insulation resistance test of transformer per phase wise in three phase transformer. Disconnect the electrical current from the transformer and grounding it. Ir value will be usually high several hundred megaohms for a dry insulation system. Moreover, for confirming operational performance of individual unit in a production lot routine test is done. Surface leakage over test objects like bushings can greatly reduce their apparent insulation resistance and, as a result, there have been many cases of insulators being scrapped when all that was really necessary was to clean them. 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. The test method is determined by the type of equipment being tested. A regular program of testing insulation resistance is strongly recommended to prevent electrical shocks, assure safety of personnel and to reduce or eliminate down time. There are a multitude of checks and tests performed as a transformer is being assembled. The standard duration of voltage application are 1 minute or 10 minutes. This guard terminal acts as a shunt to remove the connected element. It involves applying the test voltage for a short time 30 or 60 seconds and noting the insulation resistance reading at.
How is ir testing done, in view of the fact that at least 80% of electrical. The transformer was allowed to cool for hours to bring the oil and windings temperature closer winding resistance test was performed to determine the high and low side temperatures. Transformer insulation testing electrical test equipment. The test measures the insulation resistance from individual windings to. Time and again, electrical workers tell us about the importance of testing insulation resistance. The complete guide to electrical insulation testing. Perform resistance measurements through bolted connections with a lowresistance ohmmeter. Standard for acceptance testing specifications for. The test set can also perform dc insulation resistance test on cts to verify the condition of winding to winding and winding to ground insulation. Meggering insulation resistance testing of drytype power. Insulation resistance values are taken between the windings collectively as because all the windings on the hv side are internally connected together to form either star or delta. Three tests are performed to determine the condition of the insulation of the ct under test. Insulation resistance test and oil test of distribution transformer.
Only the current through the insulation is measured, since any surface current will be returned on the guard lead. Measurement of winding resistance and insulation resistance of 3 phase 11 kv 433 v, 16kva oil. Mct1605 test set provides the flexibility of both automatic as well as manual testing. It utilizes the latest dsp technology for testing single and multiratio cts.
It is typically used for test specimen that have small capacitance and as a result the power factor tan delta of the test circuit is rather high. The polarization index gives an indication of the buildup of dirt or moisture, the deterioration of insulation and the. This video will show you how to perform the megger test in a easy way. Verify insulation integrity due to the moisture and impurity contents of insulation. Perform insulationresistance tests, windingtowinding and each windingtoground. Perform the operation described in the following insulation resistance test to obtain values as close as possible to the manufacturers specifications the insulators must be very clean.
Second, the range of a megohmmeter is in megohms, as its name implies, instead of ohms as in a multimeter. Ieee recommended practice for testing insulation resistance of rotating machinery 1. A third lead, which connects to a guard terminal, may or may not be available with your tester. Select the megger range corresponding to the ratings of the equipment under test. The electrodes are long parallel traces printed interdigitated comb patterns on a standardized printed board or assembly. Understanding insulation resistance testing pdf 0712. Technical specification for startup and commissioning of new. Insulation resistance or ir test is carried out by maintenance engineers to ensure the healthiness of the overall insulation system of electrical equipment it reflects the presence or absence of harmful contamination, dirt, moisture, and gross degradation. The dielectric test of transformer is generally performed in two different steps, likewise, separate source voltage withstand test and induced voltage withstand test of transformer, which we have discussed one by one below separate source voltage withstand test of transformer. Insulation resistance test of transformer is performed on the transformer to. How to perform insulation resistance megger test youtube.