Substation Automation - Apart from basic protection functions. Relay is continuously monitors different status flags.
There are two types of status flags :
1) Logical status such relay DPR operation, WPC operation, OCR, setting change etc. these are generated with in relay.
2) Similarly there are opto-coupler inputs which are connected to external contacts such as CB NO, CB NC AP/GP ALARM etc.
Any change in logical or physical status is recorded as event. Such events are kept in internal non-volatile memory along with time stamp. Up to 100 such event can be store in relay memory. After 100 event relay overlap oldest event. These events can download for detailed analysis of any operation.Ashida