Technical specification for startup and commissioning of. 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. In the absence of manufacturers published data, use table 100. Technical specification for startup and commissioning of new. 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.
Find here insulation testing and continuity, power protection, power transformer testing, power cable infrastructure, cable fault location, general electrical. Pdf this paper consist the specification of transformer and its procedure of. Perform electrical performance tests on potential transformer circuits. A third lead, which connects to a guard terminal, may or may not be available with your tester. 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. After 1 min, you should read and record the resistance value. Hence, it is recommended that the dc resistance be measured on all onload and offload taps prior to energizing.
The primary test methods used to assess the condition of the active insulation components in transformers and bushings, on site, include. The standard duration of voltage application are 1 minute or 10 minutes. It helps to detect deterioration of insulation in order to schedule repair work such as. This video will show you how to perform the megger test in a easy way. 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. 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. Mct1605 test set provides the flexibility of both automatic as well as manual testing.
The voltage, we apply for measurement of insulation resistance, is direct voltage. Aug 16, 2014 it is unnecessary to perform the insulation resistance test of transformer per phasewise in a threephase transformer. The winding insulation resistance test is a dc high voltage test used to determine the dryness of winding insulation system. Generally, you connect two leads positive and negative across an insulation barrier. Measurement of winding resistance and insulation resistance of 3 phase 11 kv 433 v, 16kva oil. Medium voltage electrical testing transworld electric. 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. Insulation resistance testing test equipment depot. Routine tests are carried out on every unit manufactured.
Transformer insulation temperature was determined by. If the transformer is new, the resistance test also serves as a verification of the manufacturers work. Because electrical insulation will exhibit dynamic behavior during the course of your test. Insulation resistance testing guide chauvin arnoux. This dielectric test is intended to check the the ability of main insulation to earth and between winding. Measure the winding temperature, where possible, and oil temperature at the time of the test. To test the insulation integrity you will need a megohmmeter or hipot rated to produce the specified maximum test voltage. Only the current through the insulation is measured, since any surface current will be returned on the guard lead. For three phase transformers, we need to test winding l1,l2,l3 with substitute earthing for delta transformer or winding l1,l2,l3 with. For good insulation, the resistance usually reads in the megohm range. Perform an insulation resistance test on each conductor in the cable. Three tests are performed to determine the condition of the insulation of the ct under test. Feb 08, 2015 a routine test of transformer is mainly for confirming operational performance of individual unit in a production lot.
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. How to perform insulation resistance megger test youtube. Moreover, for confirming operational performance of individual unit in a production lot routine test is done. 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. Perform electrical performance test on control power transformer circuits. 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. Select the megger range corresponding to the ratings of the equipment under test. When performing insulation resistance testing, you must maintain consistency. Transformer insulation testing electrical test equipment. The polarization index gives an indication of the buildup of dirt or moisture, the deterioration of insulation and the. The following tests are routinely conducted in the field on the transformer. Troubleshooting with insulation resistance test instruments. The goal was to perform pf test at different temperatures and compare itc and tcf against real measured. With proper installation, commissioning, protection and timely maintenance during operation, the users should. It is commonly used in the industry for acceptance testing prior to energizing the cable and for maintenance testing programs. Insulation resistance test ttr test polarity test ac or dc hipot test induced potential test frequency response analyzer dissolved gas analysis tests dc winding resistance transformer core ground test polarization recovery voltage test ac hipot test the ac hipot test is used to assess transformer windings condition. Standard for acceptance testing specifications for.
Understanding insulation resistance testing jm test systems. Verify insulation integrity due to the moisture and impurity contents of insulation. Recommended test voltages for routine maintenance insulation resistance tests of equipment rated to 4,160v and above. Perform resistance measurements through bolted connections with a lowresistance ohmmeter. The test method is determined by the type of equipment being tested. Understanding insulation resistance testing aemc instruments. Time and again, electrical workers tell us about the importance of testing insulation resistance. How is ir testing done, in view of the fact that at least 80% of electrical. 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. Meggering insulation resistance testing of drytype power. All transformers are subjected to the following routine tests.
Transformers are an electrical component that transmit electrical energy between at least two circuits. It utilizes the latest dsp technology for testing single and multiratio cts. 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. 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. Transformers regulate the voltage in circuits, but in some cases these can go bad and cause a circuit to not. This guard terminal acts as a shunt to remove the connected element.
It is the product of the test voltage, the test current and the cosine of theta. The test measures the insulation resistance from individual windings to. The polarization index pi is used to determine the fitness of a motor or generator for use. 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. Ieee recommended practice for testing insulation resistance of rotating machinery 1. Understanding insulation resistance testing pdf 0712.
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. Ir value will be usually high several hundred megaohms for a dry insulation system. 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. Ensure that no leakage paths between phases or transformer body.
Timeresistance testing method this method is fairly independent of temperature and often. 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. The test method is determined by the type of equipment being tested and the reason for test ing. The insulation between the current transformer windings and windings to ground should be checked for dielectric strength while performing a comprehensive ct test. It involves applying the test voltage for a short time 30 or 60 seconds and noting the insulation resistance reading at. The megger technical library provides access to a range of additional content and resources such as technical guides, application notes and more. Test value a bolt torque levels are checked in accordance with u. Primary voltage rating test voltage in kv dc up to 1kv 1. Insulation resistance tools are critical to a preventative maintenance program, and a staple for troubleshooting any number of utility, industrial and commercial applications. There are a multitude of checks and tests performed as a transformer is being assembled. Disconnect the electrical current from the transformer and grounding it. Meggers range of transformer test equipment will ensure the assessment of each transformer component, a varying suite of electrical field tests is recommended. 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. Before conducting a transformer winding resistance test, it is important to observe all safety warnings and take proper precautions.
Ieee recommended practice for testing insulation resistance. Standard for acceptance testing specifications for electrical. With a little recordkeeping and common sense, however, you can get a good picture of the insulation condition from values that are only relative. 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 0206 rev. 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.
This test is performed at or above rated voltage to determine if there are low resistance paths to ground or. Electrical transformer test equipment solutions from megger. Installation measurements should be filed for future reference 2. Pdf measurement of winding resistance and insulation. Various routine test of power transformerpart1 february 8. 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. Insulation resistance testing is a nondestructive test procedure. It is unnecessary to perform the insulation resistance test of transformer per phasewise in a threephase transformer. The following sections of the ansineta standard for acceptance testing specifications for. 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. The electrodes are long parallel traces printed interdigitated comb patterns on a standardized printed board or assembly.
Principle of insulation testing and influencing factors insulation resistance measurement is based on ohms law. 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. Megger guide to electrical insulation testing pdf instrumart. These tests are performed with the circuit deenergized.
Meanwhile, dielectric frequency response dfr testing delivers a very reliable and accurate moisture assessment of the insulation and the conductivity of the oil. The complete guide to electrical insulation testing. 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. 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. Insulation resistance the latest test tools from the testing experts. Insulation resistance test of transformer is performed on the transformer to. 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.
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. It is unnecessary to perform insulation resistance test of transformer per phase wise in three phase transformer. The insulation resistance test is the second test required by the electrical safety testing standards. Dos and donts when measuring insulation resistance of a transformer. 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. Excitation current test insulating fluid dielectric tests insulation pf test insulation resistance test ttr test.
Perform insulationresistance tests, windingtowinding and each windingtoground. Insulation resistance test and oil test of distribution transformer. Apr 08, 2018 perform an insulation resistance test on each conductor in the cable. The index is derived from calculating measurement of winding electrical insulation resistance. 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. Aemc instruments testing methods and interpretation of the results shorttime or spotreading measurement this is the simplest method. 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. Dos and donts when measuring insulation resistance of a. Insulation dielectric test of transformer electrical4u. Meggering insulation resistance testing of drytype. The test measures the insulation resistance between the phases andor between phase and ground. Jun 28, 2017 this video will show you how to perform the megger test in a easy way.
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