Check Synchronisation Relay STS7041
Verifies the synchronism between two sources. 
High precision and stability based on the analysis of signals by analogue and digital systems. 
ANSI function code: 25 
Other functions: 
- Absolute values of the voltages 
- Voltage difference 
- Angle difference 
- Frequency difference 
- Reconnection as alternative

See the homepage for Static relays for the full brochure.