TRAN-203: the multifunctional transformer tester that measures everything in one

Turns Ratio measurement to ANSI/IEEE C57.12.90

The TRAN-203 performs ratio tests in accordance with the ANSI/IEEE C57.12.90 standard. With a measurement range from 0.8 to 50,000 and an accuracy of 0.08%, the instrument covers both small distribution transformers and large power transformers in high-voltage substations.

The instrument operates in two modes:

• CT Mode – for current transformers, test voltages 1V and 4V
• PT Mode – for voltage transformers, test voltages 1, 4, 10, 40, 100, 250V AC

Alongside the ratio, the TRAN-203 also measures in a single test:

• Phase angle measurement (0–360°, accuracy ±0.2°)
• Polarity and ratio deviation (%)
• Core excitation current (up to 2A, accuracy ±0.1 mA)
• Magnetic balance between the three phases
• Vector group detection – fully automatic, no manual setting required

The 3-phase cable configuration allows simultaneous measurement on all three phases. This saves time and removes the measurement errors caused by intermediate switching steps.

Winding Resistance – primary and secondary simultaneously, up to 20A DC

By injecting up to 20 amperes DC, the TRAN-203 measures the resistance of primary and secondary windings at the same time. The measurement range runs from 0.1 µΩ to 100,000 Ω.

The 5-digit resolution and stabilized current control give repeatable results, also on transformers with high inductance where the current takes long to stabilize. When a fault occurs in the current loop, the software automatically reduces the current to prevent damage to the instrument and the transformer.

Dynamic resistance of the OLTC

The TRAN-203 can measure the dynamic resistance of on-load tap changers (OLTCs) – on all three phases simultaneously or per phase individually. A weakened contact in the tap changer causes heat development and, if left unchecked, leads to a transformer failure.

Heat Run Test / Temperature Rise Test

With the heat run function, the TRAN-203 simulates the full nominal load of a transformer and records the resistance change caused by heating. The full load resistance R₀ is measured at up to 20A DC, in accordance with the IEC/IEEE standards for thermal performance tests.

An optional temperature sensor enables direct temperature correction of the measurement results, so the resistance reading holds regardless of the ambient or winding temperature at the time of testing.

Demagnetization – automatic after every measurement

After a resistance measurement or ratio test, residual magnetism may remain in the core. The TRAN-203 automatically demagnetizes the transformer via its voltage channels, so the next measurement is not affected by residual magnetism from the previous test.

Who is the TRAN-203 designed for?

The TRAN-203 is intended for technicians and test engineers working in or for:

• Grid operators and energy companies – periodic inspections of distribution and transmission transformers
• High-voltage substations – acceptance tests, OLTC inspection, fault diagnosis
• Installation companies and service providers – commissioning of new transformers (FAT and SAT)
• Test laboratories – verification after overhaul or rewinding work

The instrument is designed for both indoor and outdoor use. The housing is certified to IP67 (lid closed), so dust and temporary submersion in water will not damage the instrument. The operating temperature ranges from -10°C to +60°C.

Available models

The B models have an internal Li-ion battery for field use at locations without mains power. The BLUE models add wireless communication via Bluetooth for connection with the DMP software on a laptop or tablet.

Technical specifications

Renting the TRAN-203 from IONIO

The TRAN-203 is available for rental at IONIO, including a valid calibration certificate, the complete original cable set (H and X test leads, extension cables, tap changer cable) and the DMP software. Our specialists can help with commissioning and the interpretation of measurement results.

Renting makes sense when you need the TRAN-203 once or only occasionally: for a commissioning, an annual inspection or a fault investigation. You get a calibrated, complete instrument without the cost of acquisition.

Browse all test and measurement systems available for rental or go directly to the TRAN-203 product page for the full specifications.

View our transformer test products.