Hde brings a rich history of innovation, reliability and customer focus and will allow greenlee to offer a more complete product solution to power utility and electrical professionals. Tettex ttr 2796 three phase transformer turns ratio meter provides better transformer excitation due to higher test voltage of 250v. Cast resin transformer crt history cast resin transformers first appeared in germany during the 1960s. The user should then select the proper operating frequency, either 60 hz or 400 hz, and press the voltage. In this test we confirm the ct secondary connection. It also fulfils a mechanical function by supporting the windings, and contributes to better thermal health of the transformer by creating cooling ducts for the oil. The ctt5 burden test injects a current into the secondary loop to verify the integrity of the current circuit and to determine its impedance and va. In europe and parts of asia, they are using 220 volts ac, but the transformers still convert the power to about 17 volts dc on the output, and then this voltage is regulated to 5 volts, the voltage that most microchips use. How to test a stepdown transformer using a dmm sciencing. As a reliable longterm partner, we offer stateoftheart testing solutions which are continuously being developed and maintained to help you to keep pace with the increasingly complex requirements of your systems. Considering it is in operation 7 days a week, incorrect billing due to an inaccuracy of just one.
Colorcoded wires or multipleconductor cable, according to n. Customer load testing is readily performed on electric meters, cts, pts, and transducers. Check voltage across the top center tap and either of the two top taps. Test equipment used and traceability of test equipment. Transformer rated meters safety a line c line n line a load c load n load 4s voltage transformers should never be shorted. Transformer turn ratio ttr atec advanced test equipment. Value at 60 seconds after application of the test voltage is referred to as the insulation resistance of the transformer at the test temperature. Standard for acceptance testing specifications for electrical. Ct analyzer the number one in current transformer testing.
It can test transformers and rotating machine windings and perform lowcurrent resistance measurements on connections, contacts and control circuits. Testing power transformers highvoltage transformers are some of the most important and expensive pieces of. Basics, maintenance, and diagnostics xi contents continued page 9. Routine tests and type tests of transformers electrical4u. Transformers experience power loss due to load resistance, which you can test with an ohmmeter by touching the meters red and black pins to opposite ends of the transformers wiring. Mto210 transformer ohmmeter electrical test equipment. The vector group of transformer is an essential property for successful parallel operation of transformers. The megger insulation tester is a small, portable instrument that gives you a direct reading of insulation resistance in ohms or megohms. Page 3 of 9 standard work practice sp0507 ver 5 ergon energy corporation limited abn 50 087 646 062 ergon energy queensland pty ltd abn 11 121 177 802 rated knee point voltage 950 volts, maximum secondary winding resistance 3 ohms.
To reduce any physical hazards while conducting the test, low voltages are applied through the high voltage winding so that the induced voltage is lower. Twowinding transformers have terminals designated by h and x e. This new style of dry type transformer was developed with hv windings cast under vacuum in an epoxy resin. It evolved from the simple gonogo verdict into a sophisticated segment within transformer manufacturing. The losses are calculated using measured voltage and current. Current transformer metering accuracy woodmead energy services. With electronic meters, utility test labs add little value because these devices cannot be adjusted. Instrument transformer testing instrument transformers for metering purposes must have a high degree of accuracy up to class 0. How do you test a power transformer that is disconnected from. The device evaluates the current transformer as per the iec or.
Current transformers cts provide a simple, inexpensive and yet accurate means of sensing current flow in power conductors. Properly designed and constructed toroid transformers are not lossey on the test bench with a 52 ohm source and a 450 ohm load the transformer shows a loss of no more than 0. Current transformer tester model ctt5 testing applications design features. Job safety analysis power transformer testing check this is the latest process zone version before use. Twrh is a handheld, batterypowered device intended for turns ratio and winding resistance measurement of singlephase and. Voltage links are designed into meters for the sole purpose of testing the meters in the laboratory. The ideal test method is to make resistance readings at one minute intervals as the hot winding is cooling, using a unit like a megger dlro10hd 10 amp digital low resistance ohmmeter. New meter test equipment and current transformer test. By using the latest proven sfra test techniques, it is possible to accurately assess transformer condition without dismantling it.
How to use an ohmmeter to test an ac transformer sciencing. Transformer oil is used in oilfilled electrical power transformers to insulate, stop arcing and corona discharge, and to dissipate the heat of the transformer i. The working of a transformer largely depends on this turns ratio. With the meter you should be able to read 240 or 208 volts ac on the outer two wires at the bottom of the transformer. The mto210 transformer ohmmeter is a lineoperated, fieldportable instrument designed specifically to measure the dc resistance of all types of magnetic windings safely and accurately. Instrument transformer basic technical information and. Offline meters, or meter simulators, are used on your windows pc to emulate the meter hardware platform for the development and testing of meter application logic a. Hence every electrical power transformer must undergo through vector group test of transformer at factory site for ensuring the customer specified vector group of transformer. 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. Testing of power transformers seems like a similar experience. Megger makes electrical test equipment to help you install, improve efficiency and extend the life of assets and cable networks at high, medium and low voltage. Current transformer testers vanguard instruments company. If you do not have any voltage at the heater winding of the power transformer when it is in the circuit but it measured ok when it was out of the circuit, something is loading and pulling down the voltage.
Designed specifically for ct testing, the ezct2000c has the following outstanding features that can greatly increase productivity and save time during the commissioning stage. The dc resistance of a transformer winding can indicate the internal temperature of the winding when the resistance at ambient is compared to the hot resistance. Cts for metering purposes must have a high degree of accuracy to ensure accurate billing while those used for protection must react quickly and correctly in the event of a fault. If the meter or transducer uses an external potential transformer, it must be inserted between the 1040c voltage output leads and the input voltage leads of the unit under test see figure 2b, 2d. Quality test meters, test equipment and electrical testers from megger, metrel, seaward, kewtech and flir. Use small jumper to short the ct secondary from ct box, the measurement will be gone at panel. The transformer testing method is very simple and it requires only a multimeter to test the transformer.
A presentation ontransformer testing using dpatt3bi 2. Back to the basics current transformer testing ct as test equipment becomes more sophisticated with better features and accuracy, we risk turning our field personnel into test set operators instead of skilled field service technicians. The ezct2000c is vanguards thirdgeneration microprocessorbased current transformer test set. The automatic meter test system has an overall accuracy. The transformer neutral bushing is to be disconnected from earth during the test. I will also explain how to identify primary and secondary winding of a isolation step up or. Because of this, the flux in the core is so small in the short circuit test that the iron losses can be ignored. Cts are instrument transformers used for converting primary current into a reduced secondary current for use with meters, relays, control equipment and other instruments the importance of instrument transformer tests is often underestimated. Clampon ground resistance testers can be used in multigrounded systems without disconnecting or deenergizing the ground system under test. Testing will commence only after the equipment is completely installed as per approved method statement for the installation of the transformer and released for testing commissioning. Information on recommended measurement standards, installation requirements, test. Nov 25, 2016 the form 9s meter is perhaps one of the most popular meter forms used in metering. Testing a form 9s transformer rated installation learn metering. The model 505 transformer analyzer is designed for testing current transformers ct and potential transformers pt without interruption of the customers service.
The requirement of an open protocol for energy metering was necessary for bringing in homogeneity among various makes of meters. A fault leading to an open secondary could cause the primary current to overwhelm the insulation, causing the winding to short circuit. Instrument transformers cts and pts have wide application in metering and protecting the power system. Testing a form 9s transformer rated installation learn. Testing and commissioning procedure for electrical installation 1. Metering current transformers have to accurately transfer system currents to electricity meters. You can add the mta15z accessory to facilitate ansi c12 meter testing on selfcontained meters at the customers site or in the lab. Mamp metering asset management plan mdp meter data provider mpa meter provider category a. Greenlee is excited to expand the test and measurement portfolio with the hde high voltage line. Electrical test equipment power station to plug megger. Test meter are suppliers of electrical test equipment. Indigenously manufactured transformers have a wide range of ratings. Direct access standards for metering and meter data. The purpose of the test switch is explained, and the connection of test equipment to a test switch is demonstrated.
For good insulation, the resistance usually reads in the megohm range. Feb 24, 2011 metering current transformers have to accurately transfer system currents to electricity meters. Testing of singlephase meters with closed ip links using. All models, except trt03 series, have a builtin true threephase power source, which is necessary for testing turns ratio of transformers with special. Also mte has delivered and installed at different aimak in mongolia seven 5 position poly phase automatic meter test systems for the simultaneous testing of 5 electricity meters. The unit will then measure the transformer resistance value for each of the phases without the need to disconnect and reconnect cables for each phase. There are two isolated test voltages, 120v12v, which enable testing of both power transformers 120v and current transformers 12v. The latest sfra test sets make these techniques more accessible, more convenient and. The megger insulation tester is essentially a highrange resistance meter ohmmeter with a builtin directcurrent generator. Size ranges are found from in a cell phone charger up to one the size of a house at the end of a high voltage transmission line. The ground resistance tester model 6418 measures ground rod, busbar, and grid resistance and impedance without the use of auxiliary rods. Testing metering current transformers with ct analyzer. The importance of current transformer tests is often underestimated. The device language message specification dlms and companion specification for energy metering cosem form together the dlmscosem application layer communication protocol and an interface model for metering applications.
Our test equipment is ideal for each of these lifecycle phases and for any environment. Transformer winding resistance measurement is carried out to calculate the i 2 r losses and to calculate winding temperature at the end of a temperature rise test. We offer electrical maintenance which complies with the neta acceptance standards for testing and maintenance. Introduction the procedures stated in this document cover the activities in preliminary tests and inspections, functional performance tests and the commissioning of newly completed installations and existing ones after major alteration. Transformer losses can be viewed as the power consumed used by the transformer when performing work. Testing singlephase transformerrated meters instant video. Using this test correctly can help to identify tap changer performance, shorted turns, open windings, incorrect winding connections and other faults inside transformers. One current transformer test system for the testing of current transformers up to a. The need for a comprehensive current transformer testing regime is evident when the alternative is considered. The project involved driver development, vb based software development and ms sql database configuration for online data collection from eight speciality measuring test instruments and automatic complex calculations for various reports and its printing for testing 4 transfomers at same time. When shorting the cts ensure that the meter registers a decrease in the meter.
This testing can be done by a transformer turn ratio ttr meter. The transformer losses can be looked at as if the transformer was a variable load connected to the load side of the meter. Purpose and scope the purpose of this standard work practice swp is to provide guidelines for testing methods for capacitive and inductive voltage transformers. Potential transformers consist of two separate windings on a. With modern meters, some meter forms may be used to correctly meter more than one service configuration. Inspect transformer and parts for shipping damage and moisture. How to test a transformer using digital multimeter youtube. Transformer testing with handheld tester twrh dv power. The core of a transformer is made of iron whereas thewinding which is wrapped over the iron core is made up ofcopper.
When testing a form 9s transformer rated installation you will be looking at a few different things. Electricity ct metering accuracy during the commissioning of a ground source heat pump it became evident that the current transformer ct metering was only recording about 75% of the energy, compared with instantaneous readings taken from a recently calibrated multimeter. A high accuracy standard for electricity meters watthour meters, demand meters, demand registers, pulse devices, instrument transformers, and auxiliary devices. Two selectable test voltages, 4vac and 40vac, offer flexibility in testing different types of transformers.
Vector group test of power transformer electrical4u. Standard for acceptance testing specifications for. The above load loss test is normally run on power transformers having low or normal impedance less than 10%. May 10, 20 transformer manufacturers perform two main types of transformer testing type test of transformer and routine test of transformer. Nata accredited mamp information for each class of vt. Transformer turns ratio testers trt series dv power. The complete guide to electrical insulation testing. Foremost, it acts as a dielectric by storing electrical charge when the transformer is energised and, thereby, isolates transformer components that exist at different voltages. Electrical test equipment application solutions from megger. Energy metering routine testing of voltage transformers. Testing metering current transformers with ct analyzer youtube. Transformer testing with a megger dlro10hd jm test systems.
Performs ct excitation, currentratio, polarity, and phase angle tests. Ideally these windings would have zero resistance, but in reality, transformers experience power loss due to load resistance, which can easily be tested with an ohmmeter. Then, observation of meter deflections determines transformerwinding polarity. The trm403 is a three phase transformer winding resistance meter that allow the user to connect all test cables to the transformer bushings. Stepdown transformers are found in electric power company systems and in a multitude of appliances for household and industrial uses.
The term electrical maintenance refers to a program of regular inspection and service of equipment to detect potential problems and to take proper corrective measures through the approved work process controls. Losses of transformersthe transformers are made of 2 types of materials. Ring core cts are available for measuring currents from 50 to 5000 amps, with windows power conductor opening size from 1 to 8. The leads that are supplied allow for a true four terminal measurement which eliminates errors caused by lead length and. Figure 2 shows how a new meter trolley, specially designed for the testing of single phase meters with closed ip links, is connected to the upgraded test system. In this book we have laid down important aspects on transformer. Summary this 32minute dvd shows how singlephase transformer rated meters can be tested on the customers property. Similarly, current transformers take a high current and reduce it to typically 5 amps on the secondary winding so that it can be used with a watthour meter, ammeter, or protection relay. Transformer testing has developed considerably over the past years.
Transformer turns ratio meters vanguard instruments company, inc. The following sections of the ansineta standard for acceptance testing specifications for. If two conduits per meter are used, the current transformer secondary wiring shall be in one conduit and the potential transformer secondary wiring shall be in the other conduit. Aemc portable digital transformer ratiometers are designed for onsite testing of power, potential, and current transformers.
The model 6418 simply clamps around the grounding electrode or. Mar 16, 2018 the ct analyzer automatically determines all relevant current transformer values and compares the results with the selected standard. The resistance of an alternating current ac transformer is held within the wires wound around its core. Diagnose a range of problems with these testers including turn ratio, phase deviation, excitation current and winding resistance of single and three phase transformers. The working of transformer is based on the simple principle of mutual induction between the primary and secondary windings which is otherwise known as coils, which helps for to transform the energy from one circuit to another. To ensure that a transformer works efficiently, it has to be put through a number of testing procedures. This instrument measures ct admittance, ct ratio, ct primarytosecondary phase angle. Transformer loss compensation information provided by mike.
Heres a summary of the current transformer testing paper. The transformer turns ratio test, or ttr test, confirms that the transformer has the correct ratio of primary turns to secondary turns. Also, verify meter terminal markings by measuring a dry cell prior to testing. Voltage transformer testing swp page 1 of 19 standard work practice sp0508 ver 7 ergon energy corporation limited abn 50 087 646 062 1. The same form designation is usually applicable to equivalent meters of all manufacturers. Current transformers are used for measuring currents of high magnitude, whereas voltage transformers potential transformers step down voltages of high magnitudes to a lower voltage. For standard household transformer testing a digital multimeter dmm makes a good. More than one meter form could be used with a particular service depending on the connection of the instrument transformers.
The harder the transformer works, the more power consumed by the transformer and the larger the losses. Acceptable inservice performance levels for meters and devices used in revenue metering are stated. All materials and relevant documentation to this testing works shall be checked by the responsible personnel prior to the commencement of testing activities. Conditioning circuitry on the interior of the transformer then converts the 17 volts ac into a clean 5 volts dc. Current transformer testing swp check this is the latest process zone version before use. Current transformers must always be shorted when not in use.
It is carried out as a type test as well as routine test. Terminal marking of power transformers is determined by ansi standards. Set your digital multimeter to ac volts, the next setting higher than 240 volts ac on a lot of meters this is 600. Neil dwyer, manager technical services ergon energy corporation limited abn 50 087 646 062 ergon energy queensland pty ltd abn 11 121 177 802 risk score task no. Play now summary this 32minute video shows how singlephase transformer rated meters can be tested on the customers property. Hence, it is essential to inspect and calibrate those instrument transformers at regular intervals. Sfra testing on transformers dismantling a power transformer to determine its condition is hardly ever a practical possibility. Transformer oil also known as insulating oil is a special type of oil which has excellent electrical insulating properties and is stable at high temperatures.
Electrical metering equipment meter testing equipment. H 1, h 2, x 1, x 2, where h is the higher voltagerated winding and x is the lower voltage winding. Following is an approximate sequence for transformer testing. So in general the primary coil of the transformer receives the. This information is required to insure the ct will perform under all circumstances. Page 3 of 8 reference sp0504r01 ver 1 reference owner. Just be certain to disconnect the transformer from the circuit before testing to avoid the risk of serious injury. It is a versatile meter that can be used to meter either a 120208 three phase four wire wye service or a 277480 three phase four wire wye service. It is also done at site to ensure healthiness of a transformer that is to check loose connections, broken strands of conductor, high contact resistance in tap changers, high. This allows the meter to continue registering kwh, kvarh and kvah unaffected by compensation.
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