Megger is also called as a megaohmmeter and is a device used for the testing of insulation resistance of a cable. The generator has centrifugal clutch due to which the generator supplied the constant for the insulation test. How to do megger testinsulation resistance for transformer. However together, with each test contributing unique diagnostic value, the group provides a robust representation of that transformer components health. The generator can be handcranked or lineoperated to develop a high dc voltage which causes a small current through and over surfaces of the insulation being tested fig. Attach the test lead connectors to the megger testing instrument, then to the test item. Transformer testing type tests and routine tests of.
Transformers are an electrical component that transmit electrical energy between at least two circuits. Furthermore, measuring transformer winding insulation, including the connection of measuring leads, is. Understanding insulation resistance testing pdf 0206 rev. Correct procedure for demagnetizing transformer cores. Also, what would happen if a magnetized transformer was reenergized. Different configurations of neural networks have been.
Complete the test before disconnecting the test set. The next two will win a selection of megger goodies thats mugs and the like, not test equipment. Procedure of insulation resistance test of transformer. This test is performed at or above the rated voltage to determine if there are low resistance paths to the ground or between winding to winding as a result of winding insulation deterioration. Megger s comprehensive set of transformer testing tools provides a complete view of your transformer s health. Measuring a transformers dc resistance from one external terminal to another can reveal a. Meggering insulation resistance testing of drytype. For three phase transformers, we need to test winding l1,l2,l3 with substitute. For details, visit our transformer application page. If you fail to maintain your transformer with regular insulation resistance testing as can be carried out by the megger transformer ohmmeter mto series of transformer test equipment then its likely to fail before reaching its maximum operating life. Insulation resistance test and oil test of distribution transformer.
Megger makes electrical test equipment to help you install, improve efficiency and extend the life of electrical assets and cable networks at high, medium and low voltage. Working principle of megger 4 comments electrical measuring instruments the megger insulation tester is an instrument used for measuring high resistances of the order of megaohms and for testing the insulation resistance. The procedure of insulation resistance test or megger test are given below. Connections for testing insulation resistance of a transformer high voltage. Megger test is also called as insulation resistance testing irt or portable. Trax is a multifunction test system for transformer substation testing. Megger insulation resistance test device the insulation resistance test meggering is of value for future comparison and also for determining if the transformer is to be subjected to the applied voltage test. Without going into the theory, the way the test works is that a test electrode rod 2 in the diagram is. The test system replaces numerous individual testing devices which makes testing with trax a time saving and cost effective alternative to conventional measurements using separate instruments. Megger applies 700v to 5kv dc depending on the rating. M valley forge corporate center 2621 van buren avenue norristown, pa 194032329 u.
The test measures the insulation resistance from individual. Megger relay and current transformer test set the voltage present on the primary winding would be 1 volt. Megger measure the insulation resistance of the device. Their unique testing procedures and storage capability allows an operator to set up and test. Then connect the ttr20 test leads to the appropriate transformer winding terminals of phase a. Insulation resistance test or megger test of transformer. First we will disconnect all the line and neutral terminals of the transformer. Megohmmeter working principle megger working principle. In insulation resistance test, a high dc voltage is. The test measurement values are affected by variables such as temperature, humidity, test voltage, and size of the transformer. The working of megger insulation tester can be fully understood from the following steps. Figure 3typical scale on the megger insulation tester. The megger test or insulation test is carried out to ensure the healthiness of the overall insulation system of an electrical power transformer.
Trax transformer and substation test system youtube. The insulation resistance test consists in measuring the insulation resistance of a device under test. Reverse side of card at right is used to record the test data. Megger is passionate about and delivers on safety, accuracy, efficiency and usability of our transformer test instruments. The multiple protection function of todays protection relay systems requires a new level of sophisticated test hardware and software to completely analyse the operation of the unit in a real life situation. How do you connect a megger on a three phase transformer for testing. Long sleeves are highly recommended to protect skin from any exposed insulation. Insulation resistance test or megger test procedures with circuit diagram in this article we will go through megger test first of all i want to say both insulating resistance tests and megger test are same. Megohmmeter definition megger working principle megger working principle megohmmeter circuit diagram the megohmmeter or megger is an instrument for measuring very high resistances, such as the insulation resistance of electrical cables. The winding insulation resistance test is a dc high voltage test used to determine the dryness of winding insulation system.
More specifically, if 120 volts were applied to the secondary of a 600. To make a measurement on a threephase power transformer with ttr20 test set, match the vector diagram from the transformer nameplate to the corresponding winding connection diagram from table c2. We are persistent innovators with a deep understanding of transformers and their testing, striving to provide test solutions without concessions. Press the test button to activate the preset test voltage. Insulation resistance test for cable using megger is a continuity test, where the power of the circuit is off. The megger ttr201 is an automatic, handheld, battery operated transformer turns ratio test set. Procedure of megger testinsulation resistance test of transformer. The resistance under test is connected between test terminals l and g the generator handle is then steadily turned at a uniform speed till the pointer gives a steady reading. Release the test button after completing the reading. Difference between multi meter megger and series test lamp. So that we can note down the ir values ranges between lv hv. The megger test is a method of testing making use of an insulation tester resistance meter that will help to verify the condition of electrical insulation.
Test performed so performed to know the insulation resistance value is. Instruction manual for transformer ohmmeter dc winding resistance test set mto300 mto330 catalog number mto300 catalog number mto330 read this entire manual before operating. Megger relay and current transformer test set 2 ratio, polarity test ratio testing can be performed by using the mrct. There are 2 test can be performed on a transformer by a megger. Disconnect all the line and neutral terminals of the transformer. The trax multifunction transformer and substation test system has an intuitive appbased infrastructure that transforms the unit into whatever test set is required, including winding resistance. M 2621 van buren ave norristown, pa 19403 2329 6106768500. Insulation resistance test or megger test procedures with. This video shows the progression of power factor or dissipation factor over frequency. The method used by the mrct compares a voltage applied to the secondary winding to the resulting voltage produced on the primary winding. Transformer and substation test system q eighty united. Working, construction and safety measures elprocus. Transformer testing, oil testing, winding, transformer.
Transformers regulate the voltage in circuits, but in some cases these can go bad and cause a circuit to not. The transformer ratio test is used to confirm that the winding turns ratio is consistent with the voltage ratio as shown on the nameplate. For example, if the cable is of the capacity of 5amps, we can send current less than or equal to 5amps and not more than that. Insulation resistance tests megger test are carried out on all windings, core and core clamping bolts. For example, if 1 volt per turn is applied to the secondary winding. Ip test is conducted especially to determine the dryness and cleanliness of the insulation. Instruction manual for transformer ohmmeter dc winding. Earth resistance testing testing with euclid and da vinci. Samples of the measured values for both the megger test and transformer oil are shown in table 2.
Megger guide to electrical insulation testing pdf instrumart. Deterioration of the transformer insulation resistance is one of the most common. Furthermore, measuring transformer winding insulation. The proper life management of transformers requires a variety of information about the transformer s condition, which cannot be provided by one test alone. When the test terminals are open, the resistance to be measured is infinite. What is the megger test procedure for transformers. The megger 550005b handcranked transformer turns ratio test meter measures the turns ratio and excitation current of singlephase power, potential, and current transformers. Series test lamps are nothing but a 230 volts incandescent bulb the bulb specification is depending on the application is generally connected in series with the phase, load and neutral as shown in the figure. Megger leads are connected to lv and hv bushing studs to measure insulation resistance ir.
The complete guide to electrical insulation testing. Schematic diagram showing the measurement of electrical. A guide to transformer winding resistance measurements. Insulation resistance tests are made to determine insulation. View online or download megger ttr201 instruction manual. Connection between two terminals of megger and lv low voltage and hv high voltage bushing studs of the transformer are made. In addition to detecting problems associated with high resistance contacts and connectors, the megger winding tester will also detect open circuits dropout test. Megger 550005b single phase handcranked transformer turns. The standard megger testing equipment is used, the line terminal of which is connected to the winding or core bolt under test. To test an older megger model, use a working element, such as a washing machine or dishwasher electrical element, to ensure the megger is in good working order before you begin. Figure 4typical record of insulation resistance of a mill motor. Electrical test equipment application solutions from megger.
Ttr100 highvoltage equipment read the entire manual before operating. Megger relay and current transformer test set mrct. Electrical test equipment power station to plug megger. Figure 2 typical megger test instrument hookup to measure insulation resistance. Hence, it demands special consideration during routine maintenance. Ttr20 handheld ttr description the megger ttr20 is an automatic handheld battery operated transformer turns ratio test set. Always check the winding schematic on the nameplate, and trace the current paths through the. It is used to measure the turns ratio, excitation current and polarity of windings in single and threephase distribution and power transformers tested phase by phase, potential and current transformers, and tapped transformers. Firstly measure insulation resistance between low voltage windings and the main body of the transformer. In addition to the obvious faulted transformer winding i.
Demonstration on how to use trax to test winding resistance on power transformers including transformer discharge and transformer. Insulation resistance test of transformer is divided into three parts. This article discusses about an overview of what is megger test, working in a cable and transformer, safety measures and its. The standard megger testing equipment is used, the line. Each test in an individual components diagnosis test group has a characteristic strengths but also deficiencies. Transformer and substation test system postal address egger seden a ox 2 s182 1 dandrd swdn t 8 10 19 00 f 8 10 19 9. Transformer ratio test this is done primarily to check for shipping damage and to confirm that any tapchanger leads installed in the field have. Whats the cause of a magnetized transformer and whats the correct procedure for demagnetizing. Test objects can hold a lot of charge and, particularly when theyre being tested at high voltages, the stored charge can be lethal. Megger supplies graph paper which makes it easy to plot megohms of insulation.
This analog meter has manual range selection for flexibility and ease of use. The megger ttr300 threephase transformer turns ratio test set is designed to measure the turns ratio of power, instrument, and distribution transformers in a substation or manufacturing environment. Timeresistance testing method this method is fairly independent of temperature and often. Polarization index test pi value test along with insulation resistance test ir value test is conducted on hv electrical machine to determine service condition of the insulation.
Winding resistance test measures ct winding resistance with the injection of a test. Buy megger ttr300 threephase transformer turns ratio test. Insulation resistance is the ratio of applied voltage to the resulting current at a specified time after the. Do the same test on the secondary side of the coils. Program the selector switch to meet the test voltage requirement. If we send more than 5amps this may cause the failure of the.
Megger the transformer turns ratio test is used to determine the number of turns in one winding of a transformer in relation to the number of turns in the other windings of the same phase of the. Insulation resistance test of transformer is essential type test. Every facet of relay testing can be handled with the comprehensive line of relay test equipment from megger. Modern testers guard against this problem by safely discharging the test object when the test has run to completion or when it is terminated by the user. The turns ratio test is used as both an acceptance test and a maintenance test, while the polarity test is primarily an acceptance test. When making the test on the windings, so long as the phases are connected, together, either by the neutral lead in the case of the star connection or the interphase connections in the case of the delta, it is only necessary to make one connection between the megger and the windings. This current usually at an applied voltage of 500 volts or more is measured by the ohmmeter, which has. Visiting address egger seden a rinkebyvgen 19 s182 dandrd swdn registered to iso 001 and 1001 megger is a registered trademark printed matter. Ttr320, ttr32047 highvoltage equipment read this entire manual before operating.
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. We use megger test at low voltage side as shown in fig. This test is carried out to ensure the healthiness of the overall insulation system of an electrical power transformer. Instruction manual avtm ttr100 for singlephase handheld. Be sure to isolate the transformer before attaching the lead connectors. Always isolate the component that you intend to test. By measuring a transformers winding resistance from one hv transformer bushing to another, transformer resistance testing can reveal a great deal of information about the transformer. The megger ttr300 series are ideal for use by power transformer manufacturers. Insulation resistance quality of an electrical system degrades with time, environment condition i. Multifunction transformer and substation test system megger. In addition to these uses of this test, the working principle, operation procedure, types, and applications have also been discussed. The testing voltage is usually 500, or 2500 v which is generated by the hand driven generator.
How do you connect a megger on a three phase transformer. Ive been told you should demagnetize each phase after doing winding resistance but another tech told me you can get away with doing a demag on only one phase. Following are the steps for insulation testing the transformer, step 1. Testing recommendations vary through the life of a transformer and relate to the circumstances under which the testing is being performed.