What type of relaying operates by comparing incoming and outgoing currents within a protected zone?

Differential relaying is designed to protect equipment by comparing the incoming and outgoing currents within a defined protection zone. The fundamental principle behind this type of relaying is based on Kirchhoff's Current Law, which states that the sum of currents entering a junction must equal the sum of currents leaving that junction.

In the context of a protected zone, typically around transformers or generators, differential relaying continuously monitors the currents before and after the equipment. When the system is functioning normally, these currents will match, and the differential relay will remain inactive. However, if there is a fault or abnormal condition, such as a short circuit or equipment failure, the outgoing current will differ from the incoming current. This discrepancy triggers the relay to activate, leading to system isolation and protection of the equipment from damage.

This method is highly effective in providing sensitive and reliable protection, as it can detect even small differences in current that may indicate an internal fault. Moreover, it is less susceptible to external electrical disturbances compared to other forms of protection.

The other types of relays mentioned serve different purposes: distance relaying focuses on the distance to a fault along a transmission line, lockout relaying is used to disconnect equipment in case of a severe fault, and carrier rel