Enhanced relay benefits

Schweitzer Engineering Laboratories Inc. has made a number of improvements to its SEL-300G generator relay in order to make it more flexible for application on any size generator.

Enhanced features include acceptance of open delta- connected potential transformers, increased system backup protection flexibility, addition of a ground differential element and also an optional synchronism checking function.

The SEL-300G is a complete package for generator protection regardless of machine size. The addition of the two-zone phase mho distance element to the existing voltage controlled and voltage restrained phase time overcurrent elements enables the user to select from any of the three most popular methods of system backup protection. A load encroachment function provides security for backing up long lines with heavy lines.

Availability of phase distance elements makes the SEL-300G more applicable to generators connected at higher system voltages. Additional cost savings and performance enhancements are brought by the optional synchronism checking function. This function supervises the issue of the close signal to the generator breaker based on generator and bus voltage, voltage percentage difference, slip frequency, phase angle and breaker close time.