Synchronous Generator Protection

Generators represent one of the most important power system elements in an electric network. Power system networks typically consist of hundreds of geographically spread out and connected generators that operate in parallel. Most power system‐connected generators are of the synchronous machine type. Differential protection applied to generators is similar in concept to power transformers. Stator ground faults are the most common faults in generators. This type of fault occurs due to a breakdown of insulation of the stator winding to ground through the core of the stator. Under‐frequency protection is intended to prevent turbine blade damage, or loss of life due to the operation of the generator, which may be carrying a high load, during a low‐frequency system condition. Split‐phase protection unique to hydraulic generators only detects inter‐turn faults on the same phase winding. Loss of excitation is detected by a specially designed mho relay measuring voltage and current at the generator terminals.