Protection Engineering Basics and Schemes Protection Engineering | Page 143

PSM = 4.918789 0. 14 ∗ TMS t =

I 0. 02 − 1 TMS = 1. 60 ∗( 4. 9187890. 02 − 1)

0.14 TMS = 0.37sec

So our setting will be,

TCC = SI t = 1. 60sec TMS = 0. 37sec PSM = 4. 918789

Now Let suppose, I said overload factor is 1.46, so our Pick up = 1.46 times of 0.68A Pick up = 0. 9928A

1678.168

PSM =( 1.46 times of 341.175) PSM = 3. 369 Our desired tripping time is 1.60sec, and as there is over loading factor and we already discusses Extreme inverse time current characteristics which is best for load with over loading factor. t = 80TMS PSM 2 − 1 pg. 143