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Padmount Transformer Fault Withstand
An important function of DSTAR
investigations is determining the ability of typical equipment to withstand real-world
duties not addressed by the existing standards. A prime example is the fault-energy
withstand of padmount transformers, which has become an important issue for utilities
confronted with high short-circuit current levels on their feeders. Although the standards
specify poletop transformer lid retention requirements, there are no standards which
specify the mechanical integrity of padmount transformers for internal faults.
Based on DSTAR testing, the fault withstand
capabilities of typical designs have been identified. Definitive maximum current and
time-current withstand capabilities have been determined which are being implemented by
DSTAR members in their transformer protection strategies. An example is shown below.
The results have provided the members a great opportunity for cost reduction through the
elimination of unnecessary current-limiting fuse application.
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