Kalpana Kalpana (Editor)

Distribution Transformer Monitor

Updated on
Share on FacebookTweet on TwitterShare on LinkedInShare on Reddit

A Distribution Transformer Monitor (DTM) is a specialized hardware device that collects and measures information relative to electricity passing into and through a distribution transformer. The DTM is typically retrofit onto pole top and pad mount transformers. A pole top (above ground) or pad mount (below ground) transformer commonly powers anywhere from 5-8 homes in the US and is the last voltage transition in stepping down voltage before it gets to the home or business. Standard positioning of DTM devices occurs at the transformer bushings, but sometimes they are attached directly onto the secondary electricity lines. DTM devices commonly consist of highly accurate non-piercing or piercing sensors, onboard communications modules to transmit information, and a power supply provision. The DTM device reports to a collection engine, and/or existing SCADA/MDM system where relevant transformer data is stored and presented to the user; analytics platforms are oftentimes employed to interpret the information being captured and reported by the DTM.



Given its unique location within the interior of the distribution grid, the DTM – commonly referred to as an intra-grid sensor – may present real-time and/or historical information about the transformer upon which it is hosted, in addition to creating a vital ongoing information access point within the grid architecture. A series of DTM devices deployed within a distribution grid provides multiple information points that can serve merely as bellwether measurement sources for the electric utility operator, or when deployed with increased density will provide the operator with a more robust view of grid status and performance.

DTM deployments may be surgical in nature (i.e., strategically and sparingly positioned within the grid), or comprehensively positioned to reveal critical data for extended grid areas such as line segments, specific feeders, and entire substations. DTM placement and deployment density is driven by the targeted needs of the respective utility.

Remote Over-The-Air (OTA) updates / upgrades are supported by certain DTM device offerings. This OTA capability, when supported, allows the operator to perform remote configuration and / or executable code (i.e., Firmware) updates of the DTM device(s) without the need for costly truck rolls or unit replacement. By supporting OTA Firmware updates / upgrades, providers can progressively broaden and deepen the suite of data points captured by the DTM device, making it reasonably future proof, thus escalating value and relevance to the utility operator.


DTM sensors transmit timely, accurate intra-grid readings for Voltage, Energy, Current and Temperature, thus empowering a long list of derived performance and power quality understandings for operations personnel. These fundamental data points provide direct relevance to electric utility operators. Additionally, these data points can be extrapolated to reveal enhanced grid performance and asset health information. Given the physical location of the DTM within the heart of the distribution grid, in addition to the DTM reporting frequency capability, the versatility of this intra-grid sensor is expansive.

Utilities across the U.S. are beginning to turn to transformer technologies to improve distribution reliability and efficiency, as well as customer service and operating costs.

Examples of applications derived from direct and/or indirect information presented by the DTM include:

  • Asset Management and Condition Monitoring (AMCM)
  • Preventive Maintenance Recognition
  • Power Theft Identification
  • Demand Response Assistance
  • Voltage Optimization
  • Outage Notification/Restoration Enhancement
  • Distributed Generation Monitoring (i.e., bi-directional energy monitoring)
  • Transformer Under/Over-sizing Recognition (e.g., Electric Vehicle charging station impacts,etc.)
  • Abnormal Transformer Voltage Characteristics
  • Transformer-related Temperature Monitoring
  • Transformer life expectancy estimation
  • Health Concerns

    Given the physical deployment position of the DTM (i.e., on the distribution transformer), there are no known health concerns related to this family of intra-grid sensors. DTM devices are created with user/installer safety in mind, and otherwise bear no known measurable environmental impact.

    Business Case Justification

    Utility spending on asset management and grid monitoring technology is to hit almost $50 billion by 2023, according to a new study from Navigant Research. Given the pioneering stage of the DTM technology, significant business case information is limited in availability for public review. Arguments against DTM deployment commonly assert that the secondary transformer value of $1000.00 to $2000.00 US (average) does not justify applying a retrofit DTM to monitor the transformer assets’ performance. However, the DTM value is based upon a combination of features/benefits that include not only the transformer condition monitoring importance, but also a series of data visibility and reconciliation features from within the heart of the distribution grid that are otherwise unavailable to the electric operator (see Applications). In essence, while the Advanced Metering Infrastructure (AMI) or smart meter providers supply a series of data points to utilities, the DTM offers an entirely new dimension of real-time and historical data access for the grid operator, and is capable of detecting information that AMI assets cannot capture and/or report with the necessary frequency to the operator. Thus, each utility must evaluate, among other things, their unique grid management needs, their levels of unidentifiable losses that can be remediated/mitigated by DTM deployment, their Demand Response savings potential through Volt/VAR and CVR related practices supported by DTM devices, and their need for real-time and/or historic data from within the heart of the distribution grid when formulating their business case justification. Investment decisions relating to DTM deployments involve a collection of monetary benefits that include direct savings for the utility through decreased operations costs, reduced power outages, lessened power outage durations, reduced peak demand costs, and recoverable power theft losses; and indirect financial benefits associated with improved power delivery and quality to rate payers, reduced truck rolls which lessen service costs in addition to yielding decreased environmental impacts, improvement of the utility’s Key Performance Indicators (e.g., SAIDI, SAIFI, CAIDI, etc.), and improved stakeholder/shareholder value through enhanced bottom line fiscal performance by the utility.

    Relevance to the Smart Grid Revolution

    DTM devices introduce a necessary solution to the smart grid revolution. GTM Research (a division of Greentech Media) expects strong growth from the U.S. market for transformer monitoring hardware, increasing its current valuation of $112 million annually to $755 million by 2020. To date, smart grid providers have presented electric utility operators with significant management and control tools for substations, and have introduced Advanced Metering Infrastructure (AMI, or smart meters) to improve data access at the beginning and endpoints within the distribution grid. However, the expansive, and arguably most vulnerable segment of the grid remains the section between substations and endpoint meters—comprising 2.2 million line miles (US grid), and 50 million distribution transformers (US grid) -- which is now collectively coined the "heart of the grid". Presently, the “heart of the grid” area is somewhat devoid of a sufficient density of versatile, cost effective sensors thereby leaving operators with limited visibility into this critical area. To further evolve from a traditional reactionary management and problem resolution state within the “heart of the grid” space, to a more proactive posture which is congruent with the purpose and value of a ‘smart grid’, the emergence of the DTM is timely. While efforts have been made to leverage substation and endpoint meter data, along with supporting algorithms to speculate and postulate occurrences and needs within the “heart of the grid”, it is evident that grid operators require precision-accurate, timely information from within this expansive segment of the grid in order to proactively and efficiently manage its performance. The need for effectively combining all three critical points of measure (i.e., substations, endpoint meters, and DTM data from within the “heart of the grid”) may be collectively required to advance a comprehensive smart grid experience.


    Distribution Transformer Monitor Wikipedia

    Similar Topics
    Just Another Romantic Wrestling Comedy
    Peter Brackley
    Jane Comerford