What type of current is referenced when measuring fault current duration for protective device settings?

Measuring fault current duration for protective device settings typically refers to alternating current (AC). This is because most electrical systems operate using AC, and fault conditions usually occur within these systems. The behavior of protective devices, such as circuit breakers and fuses, in response to fault conditions is fundamentally designed around the nature of AC currents due to their sinusoidal waveform and the way in which these devices operate to interrupt the flow of current.

In addition, factors like the symmetrical and asymmetrical components of AC also play a role in how these fault currents develop and how long they may last. Understanding AC fault currents is essential for setting parameters of protective devices, ensuring reliable operation during fault conditions, and thus preventing equipment damage or electrical fires.

While direct current and pulsating current are relevant types of electrical currents, they are not commonly referenced when discussing fault current duration in the context of typical protective device settings in AC systems. Fault current, while similar in name, is more of a description of the current occurring during a fault rather than a specific type referenced in the measurement context.