The OMICRON TESTRANO 600 is a portable three-phase system for power and distribution transformers: it delivers 3 x 33 A DC or 400 V AC, measures all three phases at once and, with the same wiring, chains ratio, winding resistance, demagnetization and tap changer measurements. The manufacturer states that it cuts test time to a third compared with single-phase systems.
What the TESTRANO 600 is
The OMICRON TESTRANO 600 is a portable, three-phase test system of about 20 kg, which the manufacturer presents as the first of its kind for electrical testing of power and distribution transformers, single-phase and three-phase. It is used in the field, in commissioning and diagnostics, and also in factory acceptance tests (FAT).
Its central idea is to measure the three phases at the same time and use the same wiring for several tests. On a large power transformer, each climb up to the bushing to reconnect costs time and carries a risk; reducing reconnections is the practical benefit the manufacturer highlights.
What it delivers
| Feature | Manufacturer data |
|---|---|
| Source | 3 x 33 A DC or 400 V AC |
| Measurements | all three phases simultaneously |
| Discharge | active and controlled |
| Connection | two main eight-wire cables (high and low voltage) and one cable to the tap changer |
| Operation | 10.6” touch screen or PTM software on a laptop |
| Weight | 20 kg |
| Supply | mains of 85 to 264 V and 45 to 65 Hz |
Tests it can run
The manufacturer states that, once the connections are made, ratio, winding resistance and demagnetization are chained without changing the cables:
- Transformation ratio. All three phases at once. It detects shorted turns, open circuits and ratios that do not match the nameplate. What it measures and its criterion are explained in ratio, polarity and vector group test.
- Winding resistance with direct current. It assesses poor contacts in windings, terminals and the tap changer. See winding resistance test.
- Discharge and demagnetization. Active discharge dissipates the winding energy in seconds; demagnetization brings the core to a known state before excitation tests and before energizing.
- Tap changer. A control cable raises and lowers the taps from the set, which automates the measurements by position, and the set can measure the tap changer motor voltage and current with a clamp. The VAM1 accessory, from the same manufacturer, measures the vibro-acoustic pattern of the on-load tap changer. For what dynamic measurement is used, see tap changer dynamic resistance.
- Tan delta and excitation current. With the CP TD accessories, which the set powers from an auxiliary output of up to 230 V. The fundamentals are in power factor and tan delta.
Set safety
The manufacturer presents it as a system with interlocks. The safety circuit must be closed to start a test, and an emergency stop button cuts all outputs. Two signal lights indicate whether there is dangerous current (more than 3 mA) or dangerous voltage (more than 42 V) on the cables. It also requires a low-impedance protective earth to the site earthing system; operating it without one is not allowed. The SAA2 warning lamp makes it visible to everyone in the yard that a test is active.
When it makes sense to measure in three phases
Simultaneous three-phase measurement adds the most when the transformer is large, access to the bushings is difficult or the outage window is short. On small distribution transformers, the time difference is smaller and the choice of equipment is decided by other factors. What does not change is the underlying question: which tests that transformer needs, in commissioning or diagnostics. To build that list, see power transformer commissioning and how to quote tests on a power transformer.
Standards and criteria
Ratio and resistance tests follow IEC 60076-1 and IEEE C57.12.90, and IEEE C57.152 is the field diagnostic testing guide for liquid-filled transformers. Acceptance criteria depend on the factory report and on the standard that applies to the unit, and are set by the test plan. This is complemented by transformer turns ratio out of tolerance.
Reports
With the Primary Test Manager (PTM) software the set generates a record per transformer with the results of all tests, useful for comparing with the factory report and with future measurements. That comparison over time is what gives the diagnosis its value.
Variants and accessories
Around the set there are accessories that extend its scope. The CP TD modules are used for tan delta and excitation current. The VAM1 accessory measures the vibro-acoustic pattern of the tap changer. There are also the SAA2 signaling lamp and the current clamp for the tap changer motor. It can be operated from the set’s own screen or from a laptop with the Primary Test Manager software, and from a phone with the manufacturer’s companion app.
For smaller distribution and power transformers, a three-phase set is not always necessary; for large units and for series of identical transformers, the difference is noticeable. What decides it is the number of transformers, their size and the outage window.
Transformer tests on request
Do you need this test? We do it for you, in Colombia or elsewhere on request: depending on your case we recommend the right test and equipment and include them in the quotation. That way you get the test your case really needs, without paying for extra tests.
Learn the scope in power transformer testing and request your quotation through the form.
Related guides
- Testing of primary substation equipment
- Short-circuit (Z) test on power transformers
- Insulation resistance and polarization index test
- Transformer factory tests
- Transformation ratio out of tolerance
- Transformer Turns Ratio Out of Tolerance: Causes
References
- OMICRON electronics, TESTRANO 600 product datasheet (omicronenergy.com/en/products/testrano-600).
- IEC 60076-1, Power transformers – Part 1: General.
- IEEE Std C57.12.90, Standard Test Code for Liquid-Immersed Distribution, Power, and Regulating Transformers.
- IEEE Std C57.152-2025, Guide for Diagnostic Field Testing of Liquid-Filled Power Transformers, Regulators, and Reactors.
Frequently asked questions
What is the advantage of testing all three phases at once?
It reduces time and reconnections. The manufacturer states that test time drops to a third compared with a conventional single-phase system and that, with fewer climbs up and down the transformer, work safety increases. What does not change is the need for a test plan that defines what to measure and with what criterion.
How is the TESTRANO 600 connected to the transformer?
With two main eight-wire cables to the high- and low-voltage terminals, and a third cable to the tap changer control. The manufacturer designed this connection so that the same wiring serves most of the tests.
Why does the set have active discharge?
After injecting direct current, the windings are left with energy stored in their inductance. Controlled discharge dissipates it in seconds instead of letting it dissipate on its own, which reduces the risk for whoever disconnects the cables and protects the following measurements.