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Smart Grid - Transformer Load Management


The main concept for TLM is to estimate load profile of transformer based on the derived monthly data of kWh of each customer and detailed description of customers taken from database of billing system.

ETAP Transformer load management assesses typical load profiles based on customer classes, number of customers, electric power demand history and the relative load demands placed on current and future transformers in the system.

The Transformer load management application can be used to realize direct equipment, labor and materials efficiency. The cost of electric transformers can be viewed as a function of load capacity over time, and the resulting effect on equipment life span. An under loaded transformer is a capital loss; the same transformer could be used to serve higher customer concentrations and therefore make for better utilization of that particular piece of equipment. Alternatively, an overloaded transformer would be expected to have a shorter usable equipment life.

By combining the ETAP GIS / Distribution View with transformer load management an operator will be able to make more intelligent decisions regarding the continuing use of certain transformers in certain situations. Decisions might then be made to switch out a particular transformer for a higher or lower load capacity unit.

Transformer Load Management | ETAP
The transformer load management system also has the ability to allow a designer or operator to test proposed load situations. For example, customer load growth may be planned for an existing transformer location. A designer, using the transformer load management application could examine the current and historical loads occurring on a transformer.

The operator may add any number of "new" customers onto the transformer, basing the proposed energy consumption typically seen within the neighborhood or on any other amount determined suitable for the analysis. This additional proposed customer loading is added to the transformer load management analysis in an interactive process using a graphical user interface. No artificial data is added permanently to the GIS or customer information system database. The resulting load flow analysis would allow the designer/operator to make a more informed decision concerning where new load can be reasonably added, and when new transformer capacity must be included in the design.


ETAP transformer load management application accomplishes multiple goals


  • Allow for field validation of the transformer to customer link.
  • Provided loading analysis that takes into account environmental and equipment factors, as well as statistically determined load profiles.
  • Allow for an efficient yet complete reporting of the resulting load analysis.
  • Cost of ownership feature allows for the analysis of relative costs associated with transformer selection and the decision to replace existing transformers. It takes into account the cost difference between various transformers, estimated labor and replacement expenses, and the relative cost of load and no-load transformer losses.

ETAP currently has a load profile and load sector library that can be used to import customer billing data.
Transformer Load Management - Load Sector Library | ETAP
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Estimated data includes Peak kVA, Utilization Factor, Balance Phase, Overload, Under-Utilization and Average Loading.

If the purpose of the transformer load analysis is to determine as closely as possible the maximum demand on a distribution transformer, then neither the Demand Factor method nor the transformer load management method should be used. i.e. neither of these methods are best when the analysis of the total feeder is to be performed. Using these methods will result in a much larger maximum diversified demand at the substation than actuals. When the total feeder is to be analyzed, the method that gives good overall results is to allocate the load based on transformer ratings.

In addition to the traditional transformer load management technique, ETAP also includes Load Allocation Based on Transformer Ratings. When only the ratings of the distribution transformers are known, the feeder can be allocated based upon the metered demand and the transformer kVA ratings. In addition this method is also advantageous when a database that relates transformers and served customers is not available and hence requires least amount of data. An Allocation Factor (AF) is determined based upon the metered three phase or single phase kW or kVA demand (at substation) and the total connected distribution transformer kVA.