For Current Transformer requirements (CT) for the differential function in Micom P64x(P642,P643,P645) , there are to equations for knee voltage (Vk) calculations. Which should be used ?

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Issue:
Two equations in the manual for the calculation of the knee voltage for the differential function

Environment:
Micom CT requirements
Software Version B4
Hardware suffix M.

Resolution:
The two equations are used to define the CT according to the tripping time you need on your stability study, if you need a tripping time guaranteed < 35ms, you need to use equation 1 (check below photo), and if you need a tripping time between 35 to 75 ms, you must use equation 2 (check below photo).
Below is an extract from the manual containing the CT requirements for the differential function.

Note:
-Care should be taken as there might be changes in the CT requirements depending on the software version being used.
- This manual extract is from manual P64x/EN M/E93, Software Version B4 and Hardware suffix M.