A new approach to switching, fault protection, and overloadmonitoring of distribution transformers

The major current monitoring and control functions for distribution transformers include: switching transformers in and out of the distribution system; sensing and interrupting secondary faults; sensing and interrupting primary faults; and monitoring transformer loading with indication and isolation capability. A novel primary switch and overcurrent protector device for handling all these requirements is presented. The device's sensor element and magnet latch are described, and its testing and application are discussed. Although it is designed specifically for use in overhead, completely-self-protected transformers, it could be modified for use in pad-mounted transformers