During an internal fault, the rate at which the pressure rises is at
least one thousand times faster than any other pressure rise that might
occur. as a result of normal operating or external causes. This rapid
pressure rise then becomes a reliable means to detect internal
transformer faults.
When the internal fault occurs, the IFD releases a highly visible orange signal that crews can see from 60 feet (20 meters) away from the pole, even at night. The signal alerts crews that the transformer should not be re-energized, preventing a potential catastrophic failure and enhancing their safety.
The IFD reacts to a rapid pressure change of at least 0.5 psi over 5-7 milliseconds. The rapid pressure occurs only when the transformer has experienced an internal fault or short-circuit.
