What is one of the key conditions monitored by a #25 relay?

The #25 relay is primarily associated with monitoring the phase angle difference between current and voltage in an electrical system. This device plays a crucial role in power system protection and stability, particularly in identifying conditions that might lead to unsatisfactory operation or faults.

The phase angle difference is significant because it helps in determining if there is an imbalance in the power flow or if there is a potential issue with the synchronization of interconnected networks. By monitoring this angle, operators can detect abnormalities that may indicate emerging problems, such as excessive reactive power, which could lead to system instability or harmonic distortion.

Understanding phase angle differences is essential for ensuring the reliability and safety of transmission systems, as they help maintain the desired operating conditions and can trigger protective actions when needed. Other monitoring aspects, such as voltage consistency, breaker position, and current flow, are important but are typically monitored by different types of protective devices or relays tailored to those specific functions.