Improved Methods and Accuracy for Transformer Load Calculations

The general subject of distribution transformer load management has been covered by papers in the past. However, several significant advancements are being utilized by the Cleveland Electric Illuminating Company which should be of interest to the power industry. These include the following: (1) transformer and secondary loads are determined from individual customer usage, considering monthly usage for an entire year, and not just for one specific month; (2) transformer capability is determined for both thermal and voltage limitations; and (3) secondary voltage drop is calculated for each distribution. In addition, multiple correlation techniques have been used to determine the relationship between kilowatt-hours and kilowatt demand. As a result of this statistical analysis, three formulas have been derived, one for residential use, one for commercial use, and one for mixed use. This new approach adds accuracy, while still keeping the formulas simple.