Which type of relay operation is based on a direct proportion of the distance to the location of the fault?

Impedance relays operate based on a direct correlation between the distance to a fault and the measured impedance in a power system. When a fault occurs, such as a short circuit, the impedance decreases because the fault creates a path of lower resistance. The impedance relay measures this decrease in impedance to calculate how far the fault is from the point of measurement.

As the distance to the fault decreases, the impedance value drops, which triggers the relay to activate. This principle of operation makes impedance relays particularly effective for protecting transmission lines, as they can quickly and accurately determine the location of faults and isolate affected sections of the system.

Time relays are based on predetermined time intervals for operation rather than distance. Voltage relays respond to changes in voltage levels rather than distance to a fault. Current relays operate on the principle of current levels reacting to fault conditions but do not inherently measure distance in relation to the fault. Therefore, the unique functionality of impedance relays in measuring and responding to distance-related fault conditions makes them the correct answer in this context.