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Must all Transformers be Smart?

July 22, 2020
Transformers are one of the most ubiquitous and critical assets on our T&D systems. Must they all be replaced to meet the demands of a modern grid?

Electric utilities are spending hundreds of millions of dollars per year to replace aging infrastructure. Those following the industry know the principal reasons: many grid assets are well past their service life, there is a growing need for greater reliability and resiliency, goals related to higher system efficiency and the need for more flexible performance in a more complex grid environment. Transformers are one of the most ubiquitous and critical assets on our T&D systems. Must they all be replaced to meet the demands of a modern grid? What are the options for the millions of transformers that have a remaining useful life and for the applications where it is time for a replacement?   

Research and Markets recently reported that the global market for power transformers would reach a compound annual growth rate (CAGR) of 1.4% by 2023. That does not sound all that impressive, although the spending level in 2023 is projected at $12.84B annually. Another study made available by Market Research Future projected that the smart transformer market would achieve a CAGR of 11.5% by 2023. Given similar geographic coverage and timeframe, these reports imply there is a modest, but growing preference for smart transformers.

Smart transformers have built-in intelligent electronic device (IED) components and sensors that facilitate the collection, storage, analysis and communication of key grid and transformer parameters. The built-in communications may be wired ethernet, a cellular connection or Wi-Fi with encryption to help ensure cybersecurity.  Utilities have monitored power transformer operation for ages, but smart transformers can do much more in terms of monitoring and self-diagnostics. For example, system operators can remotely monitor critical components in real-time including the core, tap changers, bushings, windings and oil. ABB even provides built-in modeling that calculates hot-spot temperatures according to IEC and IEEE standards and models complete thermal behavior.

These enhanced capabilities can also be built into distribution transformers. Modernizing utilities face a number of potential challenges at the distribution level: a higher percentage of aging infrastructure;  higher network losses; and growing numbers of of distributed energy resources (DERs) that are altering design flow patterns. Smart distribution transformers can monitor their condition in the face of greater load variability and provide dynamic control of real and reactive power.  The result is improved efficiency,  better power quality and longer equipment life.

Despite the expected growth in smart transformer deployment, the reality is most utilities will probably take years, or even decades, to replace all of their aging transformers with modern smart transformers, particularly on the sub-transmission and distribution side. There are a number of interim paths towards greater asset awareness and performance that won’t bust the budget. One such approach is to buy add-on components with digital outputs for key transformers, including electronic oil level indicators, pressure release devices, Buchholz relays and self-dehydrating air breathers. This equipment can be connected to a utility’s developing smart grid or integrated into a single system using a central control module.

Utilities that are not equipped to add many (potentially 1,000’s ) of additional data streams from new transformer IEDs and sensors to their SCADA or other operating networks can use innovative open-access infrastructure data management programs. For example, OSIsoft’s PI system can be set up to collect, analyze and present data from a handful of key transformers or across an entire utility enterprise. According to OSIsoft, one utility used the PI System to implement a condition-based maintenance (CBM) asset management program for its organization.

Another example of a company focused on realizing high real-time visibility across its transformer fleet was highlighted in the story “Terna Transforms Its Maintenance Strategy” which appeared in the December 2019 issue of T&D World. Terna, an Italian transmission system operator, developed a high-voltage monitoring system to continuously track through-fault currents (TFCs) on the majority of its high voltage transformers. Terna has found that measuring TFCs and their effects on equipment is taking its condition-based maintenance program to the next level.

Utilities that wish to get as much mileage as possible from their existing transformer fleet both during and after their transition to smart transformers have another option: a comprehensive, prepackaged enterprise asset health management (AHM) system. Terna took years to develop its transformer monitoring program. AHM systems can accelerate this process by providing the programming and tools for combining historical asset records with current sensor and other smart grid data to create a comprehensive management program. While not an overnight endeavor, an operational AHM program can provide real-time asset operational and performance intelligence as well as modeling and analytics to support repair and replacement decision-making, manage conditions that may impact operations, determine what maintenance needs to be done and then prioritize required work. AHM systems can also be set up to generate work orders, order inventory, document work completed and develop regulatory compliance reports.

Transformers are among the most important and costly assets on our T&D systems. As the functionality required for our grids becomes more complex, we are beginning to see a preference for smart transformers when it is time for an upgrade or replacement. However, utilities have options for gaining many of the advantages associated with intelligent transformers during the potentially decades-long transformer fleet upgrade process.Sensors, add on IEDs, monitoring programs and AHM systems can help utilities extend transformer lives, improve O&M productivity, reduce unplanned outages, improve grid performance/reliability and achieve other cost savings.Yes, we will be buying more intelligent transformers,but there are other smart moves we can make as well.

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