The energy transition and ongoing industrialization are placing extreme demands on power grids. Whether it’s fluctuating feed-in from wind and solar, the rise of electric vehicles and data centers, or massive load changes in heavy industry: power transformers are under constant pressure.
At the heart of it all, one key component ensures the necessary stability: the on-load tap changer (OLTC). As an electromechanical control device, it adjusts the turns ratio of the windings during operation and under full load. It ensures that the line voltage remains within a narrow tolerance range despite maximum dynamics.
A tap changer is one of the few moving parts in an otherwise static transformer. The mechanical, thermal, and electrical stresses in the hot insulating oil are extreme. If a switching operation goes wrong, disaster looms: a phase short circuit that can lead to arc explosions, total loss of the transformer, and widespread blackouts.
To prevent these nightmare scenarios, test engineers rely on dynamic resistance measurement (DRM). It provides the electrical “fingerprint” of the switching operation.
Why standard measurement systems fail here
A typical switching operation often takes less than 100 milliseconds in total. But the truly critical sequences—the opening and closing of the auxiliary contacts, as well as the notorious contact bounce—take place in the range of just a few microseconds!
- Conventional data loggers with sampling rates of 10 or 20 kHz are simply blind to these transient phase changes.
- In addition, extreme electromagnetic fields prevail in the test facility and at the substation. Severe EMC interference and transient overvoltages distort the signals from unshielded measurement cards or completely destroy the hardware.
So if you want to reliably identify faulty tap changers before they later bring entire transformers to a standstill, you need top-of-the-line measurement technology.
LTTsmart precision measuring instrument: The benchmark for tap changer testing
This is exactly where we bridge the gap between laboratory precision and extreme field conditions. The LTTsmart precision measuring instrument was developed specifically for applications where speed, resolution, and immunity to interference leave no room for compromise.
Why the LTTsmart is the ideal tool for modern tap changer testing:
- True 24-bit resolution at up to 4 MHz: Captures the finest transient voltage changes and extremely fast contact bounce simultaneously on all channels—without aliasing effects.
- Uncompromising galvanic isolation: Each channel is strictly isolated (channel-to-channel & channel-to-enclosure). High levels of electromagnetic interference in the test environment therefore do not skew the results.
- Absolutely synchronous sampling: Perfect for three-phase tests. Currents, voltages, and high-frequency structure-borne noise (acoustic emissions) are correlated with each other without any time delay. Mechanical misalignments become immediately apparent.
- Smart trigger architecture: Thanks to flexible pre- and post-trigger memory, the exact critical switching moment is recorded in maximum depth, rather than producing mountains of useless data during idle periods.
With the LTTsmart, you’re investing in the long-term reliability of your systems, as the measurement system ensures the most precise analytical data during tests in test environments. Taking transformers as an example, this ensures maximum grid reliability and minimizes risks over the long term.
Do you have similar measurement requirements as those for tap changer tests? Contact us, and together we’ll discuss the best solution for your measurement challenge! Simply fill out the contact form: