Distance Relay Testing Terms

1.It is the region coming after the outermost zone that is beyond forward zone Z3 or reverse zone Z4.We will define this zone.Any disturbance starting above this zone setting and traversing through our defined area is a powerswing.

2.the logic is different in different relays.For Eg;in areva if disturbance takes morethan 5 ms to travel through powerswing zone it is considered as power swing and it blocks distance function

3.SOTF is enabled from the time of closure of CB and will b active upto 250 ms.If relay detects a fault within 250msafter CB closure, then relay operates in SOTF to clear the fault

4.Undervoltage detection/VT MCB Trip is given to sense VT failure and to block distance relay

what is zone 4 and zone 5 in a distance relay?