What type of current is used during a loop impedance test?

During a loop impedance test, alternating current (AC) is used primarily because this type of current can simulate the conditions under which the electrical system normally operates. AC current is appropriate in this context as it matches the characteristics of the electricity supplied in most residential and commercial buildings, which is typically alternating current.

Using AC current provides a more accurate assessment of the loop impedance in relation to actual fault conditions and circuit behavior, as it allows for the direct measurement of the impedance within the specific frequency range that the system operates. This ensures that the test results more accurately reflect how the circuit will perform during an actual fault situation, ultimately helping to ensure the safety and reliability of the electrical system.

In contrast, options like DC current or pulse current would not emulate real-world conditions effectively for this specific testing scenario, potentially leading to misleading results about the system's impedance and its ability to clear faults. Therefore, utilizing AC current aligns with best practices for conducting loop impedance tests.