Which of the following characteristics is associated with a distance relay used for fault protection?

Explanation:

Distance Relay for Fault Protection

Definition: A distance relay is a type of protective relay used in power systems to detect and isolate faults. It operates based on the impedance between the relay location and the fault location. The primary function of a distance relay is to protect transmission lines from faults by measuring the impedance, which is inversely proportional to the distance to the fault.

Distance relays measure the voltage and current at the relay location and calculate the impedance (Z = V/I). When a fault occurs, the impedance changes significantly. If the calculated impedance falls within a predetermined zone, the relay identifies the presence of a fault and triggers the protection mechanism to isolate the faulty section.

Correct Option Analysis:

The correct option is:

Option 1: It operates based on the impedance between the relay and the fault.

This option correctly describes the functioning of a distance relay. The relay measures the impedance between its location and the fault, and if the impedance falls within a predetermined range, it indicates a fault condition and initiates the protection mechanism.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 2: It is used only for short-circuit protection.

This option is incorrect because distance relays are used for various types of fault protection, not just short-circuit protection. They can detect phase-to-phase faults, phase-to-ground faults, and other abnormal conditions on the transmission line.

Option 3: It operates based on the current only.

This option is incorrect because a distance relay operates based on both voltage and current measurements to calculate the impedance. Relying on current alone would not provide the necessary information to determine the distance to the fault accurately.

Option 4: It operates based on the voltage at the fault location.

This option is incorrect because, although voltage measurement is part of the relay's operation, the primary basis for its operation is the impedance calculation, which involves both voltage and current. Voltage alone cannot determine the distance to the fault.