True 3-phase testing makes the difference in power transformer diagnostics

Power transformers are critical components in an electrical power network. Testing, diagnostics and reliable condition assessment of power transformers becomes increasingly relevant due to the...

byCornelius PLATH


Power transformers are critical components in an electrical power network. Testing, diagnostics and reliable condition assessment of power transformers becomes increasingly relevant due to the aging of transformer fleets around the globe. Performing a range of standard electrical tests on a regular basis has proven to be an effective way of gaining reliable insight into the operating condition of transformers. But, this has been a time- and cost-intensive job in the past. Different equipment needed to be used for each test, each phase had to be measured individually and the connections had to be changed between the tests. A true three phase test system can really make a difference.

One system – multiple tests

TESTRANO 600 is the only portable, three-phase test system which combines the most common electrical tests on power transformers for routine and diagnostic testing on site or during factory acceptance tests (FAT) in one system:

•    3-phase winding resistance with 33 A
•    3-phase transformer turns ratio with 400 V L-L
•    3-phase short-circuit impedance / leakage reactance
•    Exciting current
•    Frequency response of stray losses (FRSL) at 15 Hz – 400 Hz
•    Dynamic resistance measurement
•    Power / dissipation factor measurements at 15 Hz – 400 Hz
•    Fast demagnetization with up to 30 A

DC winding resistance measurement

DC winding resistance measurements are used to determine continuity problems in the winding connections and tap changer contacts. They are also used to check the on-load tap changer (OLTC) as they can indicate when to clean or replace OLTC contacts, or when to replace or refurbish the OLTC itself. Failures can be detected without opening the tap changer compartment. During the measurement the resistance of each subsequent tap position is investigated and compared with the reference measurement data of the manufacturer. Using TESTRANO 600 you can measure e.g. all three-phases of a wye-connected winding simultaneously. This makes testing three times faster than single-phase testing and reduces your average measurement time.

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