The SA-1 relay is a solid state, three-phase, high-speed type used for differential protection of ac generators, motors, and shunt reactors.
When equal current flow into and out of the protected apparatus, differential current doesn't flow into the operating circuit of the relay unless it is "error" current due to unequal current transformer performance. However, the relay has a variable percentage operating characteristic, and requires a larger amount of operating current at higher values of restraint, or through current, than during light internal faults, thus accommodating increased amounts of current transformer error during heavy external faults.
- Long product life
- Ease of application
- Reliable protection
- High-quality design