Taming Transient Troubles

Transients can take out your data center transformer that lacks the right protection. In certain installations, the Transient Voltage Resistant Transformer provides 100% protection.

It’s not surprising that data center managers don’t always sleep well at night, considering the list of things that could go wrong. Faced with many reliability risks and almost impossible uptime expectations, managers are eager for ways to reduce the risks of interruption.

There’s always new technology coming along to improve power reliability. One new development that will interest some data center managers is the Transient Voltage Resistant™ Transformer (TVRTTM) which increases the reliability of data center power distribution transformers.

Transient Troubles

When a circuit breaker cycles, reignitions can create fast transient over-voltages inside the transformer. A single transient can be fatal but winding damage can also build over time.

The TVRT is useful in installations that include fast-switching (such as vacuum or gas-insulated) circuit breakers in line with a medium-voltage distribution transformer, with no other installed protection. The risk of transformer damage or failure is especially high when these breakers are close-coupled to the transformer. Other factors that increase the risk are lots of cables upstream from the circuit breaker or facilities that allow disconnection at load.

Beautifully Simple Solution

The technology is simple. Varistors are placed strategically along the windings in proprietary arrangements to limit transient over-voltages. Combined with advanced winding design, this technology provides total resistance against fast transients.

Our studies dispelled several assumptions about transient-voltage damage. For one, switching transients are different than lightning-strike surges. With switching transients, the transients are generated inside of the windings. We also found amplification of voltage due to resonance inside the transformer was not as large a factor as once thought  ̶  the major culprit being over-voltages caused by high frequency reignitions. Once we understood what was really going on, it was possible to address the real problem.

Other Protections

While the TVRT is a great solution to fast transients, the traditional solution is an RC (resistor-capacitor) snubber circuit installed as a standalone device or inside the transformer. If you use snubber circuits, your transformer is well protected; however, the TVRT is a good substitute for integrated transformer/snubber-circuit packages.

The TVRT isn’t appropriate as a retrofit, however, because part of the technology is the winding design. But for replacements, upgrades, or new installations, it makes sense to consider the TVRT for several reasons. The addition of varistors does not affect standard transformer enclosure sizes, which are more compact than transformers with integrated snubber circuits. This size reduction is valuable when replacing transformers that fall under new DOE efficiency requirements due to the increase in active assembly sizes. The TVRT is also much less expensive than snubber options.

The TVRT also eliminates the risk and maintenance that come with oil-filled capacitors in the snubber. Many data centers opt for dry-type transformers to lower their maintenance and reduce the fire risk. So why use protection devices with oil-filled capacitors?


Many data centers rely on fast circuit breakers to protect their systems. Without proper protection, transformers in these systems are at risk from fast transients.

Data centers are all about minimizing risk. For applications with vacuum or gas-insulated circuit breakers connected to medium-voltage transformers, the TVRT effectively eliminates the risk of failure due to switching transients, and that should help data center managers sleep better at night.

Learn more about the Transient Voltage Resistant Transformer.

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About the author

Joel Kern

Joel graduated from Virginia Polytechnic and State University (Virginia Tech) in 2006 with a B.S. in Mechanical Engineering. He was hired into ABB shortly after as an electrical and mechanical design engineer. He has spent over 10 years heavily involved in the research and development and marketing strategy for ABB’s dry-type transformer product footprint in North America. During that time, he developed key technologies for the marine, data center, commercial infrastructure and utility markets. In his current role of Global Product Manager, he investigates new ways to increase the safety of distribution systems for ABB’s global partners.
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