Summary of IEEE Guide for the Protection of Network Transformers

A summary is given of C37.108-198X, a new IEEE Guide. The summary describes the equipment used in a typical network transformer system. The performance of this equipment is described during fault and nonfault system conditions. The limitations of the present protection are addressed, most importantly, for low-voltage, low-current arcing faults. Protective devices that can be added to the existing network transformer protection are listed. Some of these devices sense conventional input quantities such as phase current, ground current, impedance, and transformer rate-of-pressure rise, whereas others sense heat, ultraviolet light, and smoke. The application of interrupting devices such as circuit breakers, vacuum interrupters, fuses, and current-limiting fuses including an electronic fuse are discussed with special application considerations identified. An example demonstrating how a protective system can be designed utilizing the devices described within the guide is included as an appendix to the guide