Transformer Condition Monitoring – Hedging Your Business

Transformer condition monitoring is a necessary function with multiple benefits.
Published: Thu 15 Jan 2015

Transformers are a large, costly asset and fundamental to the safe and reliable delivery of power. So when a transformer fails the consequences can be significant, from sudden loss of power to consumers to loss of revenue to the transmission operator.

But that needn’t happen with transformer condition monitoring, says Anton Wiedenbauer, Product Lifecycle Manager at Siemens AG, who will be discussing the topic in a forthcoming Engerati webinar, Transformer Condition Monitoring – A dashboard for your most important Transmission & Distribution assets.

“If we know when a transformer is failing or about to fail, then the outage can be planned and money saved,” says Wiedenbauer. “Thus it is important to know the condition of transformers, especially in the changing transmission environment.”

Joining Wiedenbauer in the January 22 webinar will be colleagues Dr.-Ing. Rüdiger Kutzner, head of Global Technology Center at Siemens Transformer Lifecycle Management, and Stefan Ettl, head of R&D for Transformer Condition Monitoring at Siemens.

Ageing transformers

Wiedenbauer explains that transformers are robust assets and the probability of failure is very low at less than 1%, or a fraction of a percent of the installed base. However, the probability is increasing for two reasons. One is that with the shift to a smart grid, generation is becoming more decentralized and grids are carrying more load and so transformers are becoming more stressed. The second is that the global transformer fleet is ageing, with many transformers now older than their 30-year expected lifetime.

Traditionally transformer maintenance is based on biannual or even annual inspections, Wiedenbauer continues. However, with such a regime the transformer owner is “blind” for the remainder of the year. “Our experience is that a dramatic change in condition can evolve very quickly,” he says. “If one made an assessment one day the transformer could appear fine, but within a few days it could have failed.”

Transformer failure

Wiedenbauer says that most transformer failures occur in the winding, for example from a high resistance, or from a partial discharge. Most of these failures also manifest in the transformer oil, with for example an increase in the dissolved gases or a typical ratio of these gases, and so assessment of a transformer’s condition normally involves analysis of its oil.