How does a differential protection relay work?

A differential protection relay operates by continuously comparing the current entering and leaving a specific device, such as a transformer or generator. The core principle behind this is that under normal operating conditions, the current entering the device should equal the current exiting it. If there's an imbalance due to a fault—such as a short circuit or an internal failure—the current levels will differ, prompting the relay to detect this discrepancy.

In the case of a fault, the relay will trip the associated protection device (like a circuit breaker) to isolate the affected section of the circuit, thereby preventing damage and maintaining system safety. This method is particularly effective because it provides sensitive and selective protection, allowing only the faulty section to be disconnected while the rest of the system continues to operate normally.

Monitoring voltage fluctuations, measuring temperature changes, or assessing insulation conditions, while all important aspects of electrical systems, do not directly relate to the primary function of a differential protection relay. These are handled by other protective devices or monitoring systems that serve different purposes within the electrical protective scheme.