Testing and calibrating instrument transformers often requires standard burdens of reliable accuracy and stability, and burdens that are immune to stray fields and harmonics. The burden sets described below have been carefully designed to meet these requirements. They provide the standard burdens required for the testing of current and voltage transformers for metering service, and for the testing (within the current rating provided by the sets) of current transformers for relaying applications, all as called for by ANSI/IEEE C57.13-2016.
One burden set, the Type BSC-5, provides in one unit three of the ANSI standard burdens for current transformers for metering service, i.e., B-0.1, B-0.2, and B-0.5. The BSC-24 set includes B-0.9 and B-1.8, while the BSC-25 includes all metering burdens (B-0.1 through B-1.8). The heavier burdens are provided by two sets. The Type BSC-8 covers the ANSI burdens B-1, B-2, and B-4 for current transformers for relaying applications; the Type BSC-9A includes the ANSI B-4 and B-8 burdens.
All the current burden sets are designed to be used with external leads consisting of a 5-foot pair of #8 copper conductors. This becomes very significant at the lower burden values, since the external leads constitute a significant part of the total burden.
The standard burdens for voltage transformers (120 volt secondaries) are covered by three sets. Three of the burdens, i.e., W, X, and Y, are combined in one unit, the Type BSP-6 burden set. The burdens in this set are independent of each other, each with its own pair of binding posts. The standard burden Z is supplied in a separate unit, the Type BSP-7. Two of these BSP-7 burden sets can be used in parallel to obtain ANSI burden ZZ. The ANSI M burden is contained in the BSP-20 unit. The burden sets are of the portable type, supplied in beige finished metal housings with engraved bakelite terminal boards. Extensive design and development work in perfecting these burden sets, and the quality material and skillful workmanship employed assure excellent performance and quality throughout.