Tap Changer Analyzers & Winding Ohmmeters

Winding resistance test of inductive test objects, such as power transformers, is one of the most effective non-intrusive ways of checking its condition. Due to their advanced design, DV Power winding resistance meters provide high test currents (up to 100 A DC) and high accuracy (up to 0.1%) within light and portable test instruments. In addition to winding resistance measurement, it is also possible to perform simple, quick and reliable transformer on-load tap changer condition assessment by recording the test current during tap changer operation, also known as DVtest. Because of that, problems with a tap changer connection, contacts, and switching procedure can be detected.

DV Power winding ohmmeters consist of single-phase RMO-T and three-phase TWA series. Models from the TWA series are designed for six-winding resistance measurement of power and distribution transformers, with only one single-step cable setup. As a result of reducing the total test time, it enables significant saving of time and money.

Typical application areas of these instruments are high-voltage substations and industrial environments. They are intended to measure the resistance of:

Transformer windings
On-load tap changers
Generators
Electrical motors
High-current bus bar joints
Cable splices
Welding joints

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Transformer Test Equipment

IBEKO Power AB

DV Power test instruments perform various diagnostic tests on power and instrument transformers. Even more, a unique feature is a condition assessment of on-load tap changers. Performing a transformer test before their breakage can be crucial.Test instruments are portable and enclosed in durable metal cases. Also, the 19” rack-mounted version suitable for factories is available as well.Applications supported by DV Power transformer test equipment include:Winding resistance measurement (IEC 60076-1)Analysis of on-load tap changers (IEC 60214-1)Heat run test (IEC 60076-2)Automatic transformer demagnetizationTurns ratio measurement of power and instrument transformers (IEC 60076-1)Excitation current measurementPhase angle measurementTransformer vector group detectionDemagnetization status verificationAll of the above-mentioned measurements are performed with the highest accuracy.The advanced DV-Win PC software collects both numerical and graphical results. As a result of that, these features provide an easier and more efficient analysis. After the test, DV-Win software generates a test report with a single click. Furthermore, a user can easily customize the test report and save it in different formats, such as XLS or PDF.Finally, the analysis of on-load tap changers is performed by the new method called dynamic resistance measurement (DRM). This is a non-intrusive method. Therefore, it allows detecting problems in on-load tap changers without disassembling them.

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Handheld Turns Ratio & Winding Resistance Tester

TWR-H Series - IBEKO Power AB

Handheld TWR-H device is DV Power single-phase instrument designed for measuring transformer winding resistance and turns ratio.The instrument has two output DC sources for measuring transformer winding resistance. The first DC source can output up to 2 A DC and is used for injecting current to the transformer’s high voltage winding. The second DC source can output up to 10 A DC and is used for testing the transformer’s low voltage winding. This is especially useful when measuring winding resistance of distribution transformers. These transformers have large turns ratio and therefore a big difference between resistances of high voltage and low voltage windings. Upon the winding resistance test, it is also possible to demagnetize the transformer core. The demagnetization process is completely automatic and safe.Together with the turns ratio, the instrument also measures excitation current and phase shift. This enables detecting transformer core or winding turns failures which cannot be spotted by measuring turns ratio only. The instrument can output test voltage up to 40 V AC for this test, but it can also output a very low test voltage of 1 V AC which is necessary for turns ratio verification of the majority of current transformers.TWR-H is powered by an internal Li-Ion battery. Up to 100 tests can be performed with a fully charged battery.

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Transformer Turns Ratio Testers

IBEKO Power AB

Transformer turns ratio testers from TRT series are DV Power instruments mainly designed for the measurement of power transformer turns ratio. Also, they measure transformer excitation current and phase shift. Special tests, such as automatic vector group detection and magnetic balance, can be performed on three-phase transformers and three-phase autotransformers.All models, except TRT03 series, have a built-in true three-phase power source, which is necessary for testing turns ratio of transformers with special configurations, such as phase-shifting, rectifier, arc-furnace, traction transformers, etc.DV Power turns ratio testers can output various test voltages for different applications. From the extremely low test voltage of 1 V AC that enables turns ratio verification of the majority of current transformers, up to the highest test voltage of 500 V AC that provides the most accurate turns ratio testing of power transformers used in power generation and transmission. By using the external booster, test voltage increases up to 5 kV AC in order to successfully test capacitive voltage transformers.All DV Power turns ratio testers have a built-in tap changer control unit. Because of that, it is possible to control the on-load tap changer (OLTC) directly from the device. In order to make the most out of this feature, the instrument and included DV-Win software can be programmed to do everything automatically – running turns ratio tests, changing OLTC tap positions, and saving results. This option significantly facilitates and shortens the turns ratio testing time.TRT turns ratio testers use the same set of cables as three-phase winding ohmmeter & tap changer analyzers from the TWA series. Consequently, it enables one-time cable setup for performing eight tests:turns ratioexcitation currentphase anglemagnetic balancevector group detectionwinding resistanceon-load tap changer DVtestand demagnetization.

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Three-Phase Transformer Demagnetizer

DEM60C - IBEKO Power AB

After a DC current test, such as winding resistance measurement, the magnetic core of a power or instrument transformer may be magnetized (remnant magnetism). It can cause various problems such as wrong diagnostics, inaccurate measurements on a transformer, inrush current at the start-up of a power transformer, or incorrect operation of protective relays due to magnetized CT cores. The best way to eliminate this source of potential problems is to use demagnetizer on the power or instrument transformer.The DEM60C is a fully automatic test instrument which performs three-phase transformer demagnetization. Transformer magnetic core demagnetization requires the application of AC current with magnitude decreasing to zero. DEM60C provides this AC current by internally changing the polarity of a controlled DC current. During the demagnetization process, the instrument supplies the current at decreasing magnitude for each step, following a proprietary algorithm. It can demagnetize single-phase and three-phase power transformers.The instrument can be connected to all three phases of a power transformer to be demagnetized, on either the primary or the secondary side. If a user selects specific vector diagrams for different types of transformers, DEM60C will run a specific demagnetization procedure for each transformer type (i.e., single phase, delta, wye/star, zig-zag.) without switching the test leads.DEM60C enables safe and efficient power transformer demagnetization. The instrument automatically regulates the injection of current and discharging energy from the inductance. During and after the operation, an intrinsically safe discharge circuit with an indicator rapidly dissipates the stored magnetic energy. The discharging circuit is independent of the power supply, which improves its reliability in case of loss of power.Test currents of up to 60 A DC enable efficient demagnetization of even the largest power transformers. Using a DV Win software, it is possible to control DEM60C externally.

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Single-Phase Transformer Winding Resistance Meters

RMO-TW Series - IBEKO Power AB

RMO-TW series is perfect for winding resistance measurements of inductive objects. It is ideal for testing transformer windings (power transformers, distribution, autotransformers) and for on-load tap changer verification. In addition, any RMO-TW transformer ohmmeter & tap changer analyzer can also perform transformer demagnetization.The series contains 4 models, with maximal test currents from 10 A (RMO10TW) to 50 A (RMO50TW). They are fitted in a portable and lightweight metal housing.All transformer ohmmeters from RMO-TW series generate a true DC ripple-free current with automatically regulated measurement and discharging circuit. The injection of current and discharge of energy from the test object are automatically regulated.Three independent channels enable testing of three windings in series. Consequently, this enables measurements of winding resistance in every tap position of an on-load tap changer without discharging between the tests.DV-Win software enables control and observation of the test process, as well as saving and analyzing the results on a PC. It provides a test report, arranged in a selectable form as an Excel spreadsheet, PDF, Word, or ASCII format. Additionally, DV-Win measures and calculates the OLTC transition time, the ripple and the winding resistance for each tap changing operation. The software can also perform the calculations necessary for the “Heat Run” test. Finally, a user can export all results in the form of a report.

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Single-Phase Transformer Winding Resistance Meters

RMO-TD Series - IBEKO Power AB

Using the most advanced switch-mode technology available today, the RMO-TD series is ideal for winding resistance measurements of inductive objects. Transformer resistance meters and tap changer analyzers are perfect for testing:transformer windings (power transformers, distribution, autotransformers),all types of tap changers,generators,electrical motors,high-current busbar joints,cable splices,and welding joints.In addition, transformer demagnetization can also be done with all RMO-TD instruments.The RMO-TD series contains 3 models, with maximal test currents from 25 A (RMO25TD) to 60 A (RMO60TD).The three independent voltage sense channels enable testing of three windings in series. This enables measurements of winding resistance in every tap position of an on-load tap changer without discharging between the tests.All RMO-TD transformer resistance meters have a built-in tap changer control unit. It enables remote control of on-load tap changer (OLTC) directly from the device. In order to make the most out of this feature, DV-Win software is included which can be programmed to do everything automatically – running winding resistance tests and changing OLTC tap positions.The DV-Win software also enables control and observation of the test process, as well as saving and analyzing the results on a PC. It provides a test report, arranged in a selectable form as an Excel spreadsheet, PDF, Word, or ASCII format. Additionally, DV-Win measures and calculates the OLTC transition time, the ripple and the winding resistance for each tap changing operation. The software can also perform the calculations necessary for the “Heat Run” test.All results can be exported in the report format.

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Single-Phase Transformer Winding Resistance Meters

RMO-TT Series - IBEKO Power AB

RMO-TT series is perfect for measuring winding resistance of inductive objects such as power and distribution transformers or autotransformers. Additionally, every transformer resistance meter from RMO-TT series can analyze:tap changers,generators,electrical motors,high-current busbar joints,cable splices,and welding joints.Transformer demagnetization can also be performed with all RMO-TT instruments.The series is consisted of 3 models, with maximal test current from 40 A (RMO40TT) to 100 A (RMO100TT). RMO100TT is the only portable transformer resistance meter in the market with 100 A DC output current.The three independent channels enable testing of three windings in series. Consequently, a user can measure winding resistance in every tap position of an on-load tap changer without discharging between the tests.In addition to winding resistance measurement, a user can perform a detailed on-load tap changer analysis by analyzing recorded graphs (10 kHz sampling rate) and by measuring vibrations on an external tap changer tank.All RMO-TT instruments have a built-in tap changer control unit. Because of this, it is possible to remotely control on-load tap changer (OLTC) directly from the device. Also, a user can program DV-Win software to do everything automatically – running winding resistance tests and changing OLTC tap positions.The DV-Win software also enables control and observation of the test process, as well as saving and analyzing the results on a PC. It provides a test report, arranged in a selectable form as an Excel spreadsheet, PDF, Word, or ASCII format. Additionally, DV-Win measures and calculates the OLTC transition time, the ripple and the winding resistance for each tap changing operation. The software can also perform the calculations necessary for the “Heat Run” test.All results can be exported in the report format.

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Three-Phase Transformer Winding Resistance Meters

TWA Standard Series - IBEKO Power AB

When it comes to winding resistance measurement on three-phase power transformers and autotransformers, TWA Standard series offers some of the most technically advanced instruments with LCD display in the market. Both models are capable of testing six transformer windings with a one-time cable connection, as well as three-phase automatic transformer demagnetization. The stored magnetic energy is safely automatically discharged at the end of the test. The built-in tap changer control unit enables automated test mode, where the instrument operates the tap changer without operator input and records winding resistance results based on pre-selected stabilization criteria. This option makes the operator’s job significantly easier.Both models can output test currents from 5 mA to 25 A DC for the purpose of winding resistance measurement. TWA40D has a special test mode for checking the synchronization of on-load tap changers with three phases simultaneously tested in parallel, in which the total test current can rise to up to 40 A DC.TWA40D has additional advantages when it comes to non-intrusive tap changer analysis. The unique DVtest method enables checking the moving contacts of on-load tap changers during the transition, measuring the transition time, detecting open circuits, and many other types of faults. It is performed with 0.1 ms sampling rate, simultaneously with the measurement of tap changer motor current which helps with the detection of motor and mechanical issues. A special proprietary algorithm is used for testing tap changers connected through a built-in series (booster) transformer. The DVtest can be performed either on one phase or on three phases simultaneously. It can also be performed as an additional test simultaneously with the winding resistance test in all tap positions.An additional unique advantage of TWA40D is the capability of simultaneously testing the winding resistance of all three phases of a three-phase transformer (connected in a YN configuration). This can significantly shorten the total testing time – for example, it enables the operator to perform 33 measurements instead of 99 on a tap changer with 33 tap positions.The test leads for TWA three-phase transformer winding ohmmeters are interchangeable with the TRT turns ratio testers, which means that both sets of tests can be performed with a single test lead connection to the power transformer terminals.

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Three-Phase Transformer Winding Resistance Meters

TWA Advanced Series - IBEKO Power AB

TWA Advanced series is the latest DV Power solution for three-phase transformer winding resistance measurement and tap changer analysis. They are capable of testing six transformer windings with a single cable connection, as well as three-phase automatic transformer demagnetization. It has the option of the automated test mode, where the instrument operates the tap changer without operator input (minimizing the risk of human error) and records winding resistance results based on pre-selected stabilization criteria.The unique DVtest method of tap changer analysis enables checking the moving contacts of on-load tap changers during the transition, measuring the transition time, detecting open circuits, and many other types of faults. It is performed with 0.1 ms sampling rate, together with the measurement of tap changer motor current which detects motor and mechanical issues. A special proprietary algorithm is used for testing tap changers connected through a built-in series (booster) transformer. The DVtest can be performed either on one phase or simultaneously on three phases. It can also be performed together with the winding resistance test in all tap positions.A unique advantage of TWA Advanced instruments is the capability of simultaneously testing the winding resistance of all three phases of a three-phase transformer connected in a YN configuration. This can significantly speed up the testing– for example, it enables the operator to perform 33 measurements instead of 99 on a tap changer with 33 tap positions.TWA500 is equipped with a large 10.1” graphical touch-screen display, while TWA400 has a 7” graphical touch-screen display. Besides making the interface much more user-friendly compared to older winding ohmmeters, it also enables certain test options that were previously available only with DV-Win software. The most important among them are DVtest, tap changer motor current measurement, “Heat Run” test, test templates, and automatic test mode.

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Tap Changer Analyzers & Winding Ohmmeters

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