North American Study of Network Transformer Use and Plans in Progress through August 2020.
Preliminary Findings Suggest Increased Use of Network Transformers Likely as Underground Distribution
Increases in Dense Urban Centers and on Large Commercial and Industrial Campuses
August 18, 2020. Ellicott City, Maryland. The Newton-Evans Research Company is conducting a major study of usage trends and plans for network transformers used to supply power to grid-type secondary distribution networks and systems in areas of high load density, typical of large urban areas, and are designed for use in vault type or subway type applications, in scores of cities and some suburban areas and large C&I campus-like settings across the North American grid.
Network transformers may be oil-type or dry-type units, and of either single-phase or 3-phase design. Underground submersible units being purchased currently are likely to comply with IEEE standards requirements approved in 2016 (C.57.12-24) and for 3-phase units <2500kva (C.57.12-40) as approved in 2017. Usage of network transformers is limited to underground networks found in major metropolitan areas served by IOUs, large municipal utilities and in a few high-density suburban areas served by distribution cooperatives
Product distribution channels used include purchasing direct from the manufacturer, distributors, and occasionally, manufacturer representatives or sales agents. Major IOUs serving large cities having underground distribution networks tend to use blanket purchasing arrangements with selected manufacturers.
Most currently installed units across North America utilities are oil type units. About three-quarters of respondents to date prefer to purchase network transformers paying a higher initial cost and minimal service requirements, while one-quarter prefer a lower initial cost with an ongoing service agreement.
Product safety has been ranked as the most important feature of network transformers among the initial group of respondents, followed closely by operating life expectancy. Product efficiency of operation and prior field experience with equipment manufacturers were also important among this group.
Significant volume users of network transformers were unanimous in reporting that new underground, submersible transformers must meet current IEEE requirements and all network transformers are expected to comply with IEEE C57.12-40.2017.
When asked to indicate whether network transformers were being used in conjunction with other devices, network protectors and protective relays were especially prominent as noted by respondents. A few also noted use of surge arresters on the high voltage side of the transformer and some have also reported including network transformers in their utility transformer asset management software.
For utility engineering and operations personnel who may wish to participate in the study, please send an email request to cnewton@newton-evans.com and a survey link will be forwarded. A report of findings will be shared with participants. All submissions are held in confidence. Only aggregated information is used in report preparation. Generous stipends/donations are available. The field work will be completed in August, 2020.
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summary reviews and highlights from completed studies
