Transformer Test Equipment
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 demagnetization
Turns ratio measurement of power and instrument transformers (IEC 60076-1)
Excitation current measurement
Phase angle measurement
Transformer vector group detection
Demagnetization status verification
All 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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Product
Handheld Turns Ratio & Winding Resistance Tester
TWR-H Series
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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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Product
Tap Changer Analyzers & Winding Ohmmeters
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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 windingsOn-load tap changersGeneratorsElectrical motorsHigh-current bus bar jointsCable splicesWelding joints
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Product
Transformer Turns Ratio Testers
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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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Product
Three-Phase Transformer Demagnetizer
DEM60C
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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.
