Protection Engineering Basics and Schemes Protection Engineering | Page 142

I PFL = 341. 1715A At secondary of 500 / 1 CT it will be;

341. 1715 I PFLCT =

500 1

I PFLCT = 0. 68A

I primary fault = I PFC =

MVA ∗ 1000 1.732 ∗ % Z ∗ V HT

1000 I PFL = 65 ∗

1.732 ∗ 20.33 % ∗ 110 I PFC = 1678. 168A

At secondary of 500 / 1 CT it will be; 1678. 168

I PFCCT =

500 1

I PFCCT = 3. 356336A

Relay Pick up if we select 1, and our desired tripping timing for this relay is 1.60, then we need to find TMS for this setting, our TCC is SI.

I PFC

PSM =

100 % of I PFL 1678. 168

PSM = 341.175 pg. 142