Fig. 2 Tripping time and current direction settings
In this case, if short circuit is at SC1, then breaker “5” will trip in 0,8 s and breaker “6” will trip in 1,0 s. Breaker “4” will not trip as it has 1,0s (>0,8s) time setting and breaker “7” will not trip as well, as it has 1,2s (>1,0s) time setting for relevant short circuit current. Also, if short circuit is at SC2, breaker “4” will trip before breaker “5” and breaker “3” will trip before breaker “2”. We can see, that this kind of protection logic can ensure selectivity even in double – end – fed system.
Implementing directional overcurrent protections in EA-PSM
User can implement directional overcurrent protections in EA-PSM. In this article we will describe the whole process of implementing directional overcurrent protections:
- For directional protection system to work properly, breakers should be added to both ends of each line in a double – end – fed or non – radial network. This is because in case of short circuit, current will always flow from two different directions.
- When breakers are added, open one of them (by double clicking on it) and in the breaker properties window go to “Protection” tab. Here select “Add Protection” button and add two overcurrent protection functions “I >” – one for each direction.
- In order to implement directional protection logic, user should select “Direction” from the drop-down menu that is highlighted in the picture 3.