Protection Engineering Basics and Schemes Protection Engineering | Page 140

I SFL is 2803.16A and CTR is 4000 1

Pick up = 130 % of 2803.16A

Pick up = 3644.108 A

I SSC

PSM =

130 % of I SFL 9508. 683

PSM =

3644.108 PSM = 2. 6

If TCC is SI, and our desired tripping is t = 0.3sec after incorporating all grading margin and others values, then

TMS t = 0.14 ∗

PSM 0. 02 − 1 TMS = 0.3 ∗ 2. 60. 02 − 1

0.14 TMS = 0. 0413sec

Our Setting is, TCC = SI Pick up = 1. 184335A PSM = 2. 6 TMS = 0. 04sec pg. 140