This Standard specifies energy efficiencies for liquid-filled distribution transformers. The Total Ownership Cost (TOC) methodology is recommended as the means for achieving these energy efficiencies, particularly for use by electric utilities. This Standard also specifies an optimal method for non utility users, based on a modified TOC methodology that meets the conditions of energy cost.
Note: Table 1 in this Standard provides minimum efficiency values derived from those shown for liquid-filled distribution transformers in NEMA Standard TP 1. It was found that efficiencies so obtained approximate the results of a survey conducted nationally among Canadian users and manufacturers.
The transformers to which this Standard applies are single-phase and three-phase, 60 Hz, liquid-filled distribution transformers, rated at 10#833 kVA for single-phase and at 15-3000 kVA for three-phase insulation class 34.5 kV and less. Minimum low voltage ratings are shown in Table 1.
This Standard describes special features that influence efficiency, and provides for the necessary modifications to the tabulated efficiency values.
This Standard addresses the test methods and procedures for determining the transformer efficiencies.
This Standard does not apply to autotransformers, testing transformers, welding transformers, furnace transformers, rectifier transformers, network transformers, or grounding transformers. Also excluded are transformers with special core/coil designs required by dimensional constraints, transformers with tap ranges greater than 15%, transformers with frequencies other than 60 Hz, and step-voltage regulators.