What type of relay is used for synchronizing purposes?

A synchronizing relay is specifically designed to ensure that the voltages and frequencies of two or more sources of alternating current (AC) are in phase before connecting them together. This type of relay measures parameters such as voltage magnitude, frequency, and phase angle and can either allow or prevent the connection based on this analysis.

When synchronizing multiple power sources, it is crucial to connect them only when they are aligned in terms of voltage and phase to avoid equipment damage and ensure stable operation. The relay intervenes by detecting conditions that would allow for a safe synchronization process, essentially validating that the two systems can be connected without adverse effects.

Other types of relays such as distance relays, time overcurrent relays, and AC reclosing relays serve different purposes. Distance relays protect transmission lines by measuring the impedance to detect faults, time overcurrent relays are used for overload protection by responding to current levels over time, and AC reclosing relays manage the automatic restoration of power after a fault. However, none of these fulfill the specific function of synchronizing AC systems, making the synchronizing relay the correct choice for this question.