Table 2 Comparison of action behavior between twin protection and actual protection device

Internal and external metal attribute fault

K1AN

9.5 ms cut off I

11.3–14.3 ms cut off bus I

–

K4ABN

–

–

–

Busbar-tie dead-zone fault

K6AN

9.3 ms cut off bus II,

228.8 ms cut off bus I

10.5 ~ 17.8 ms cut off bus II,

225.0 ~ 226.0 ms cut off bus I

Bus coupler 1 CB closed

K6ABN

9.3 ms cut off bus I

10.5 ~ 12.8 ms cut off bus I

Bus coupler 1 CB tripped, input bus coupler 1 split pressing plate

K6AB

9.8 ms cut off bus II,

168.3 ms cut off bus I

11.0 ~ 12.0 ms cut off bus II,

166.3 ~ 167.5 ms cut off bus I

Bus coupler 1 CB tripped, but there is current

Developmental and transformational fault

K1AN-0.01-K1ABN

11.0 ms cut off bus I

11.5 ~ 16.5 ms cut off bus I

–

K4BN-0.1-K2AN

109.8 ms cut off bus II

126.8 ~ 127.5 ms cut off bus II

–

K2AN-0.2-K4BN

9.3 ms cut off bus II

10.5 ~ 14.8 ms cut off bus II

–

K1AN-0.01-K2AN

9.3 ms cut off bus I,

31.3 ms cut off bus II

11.3 ~ 12.5 ms cut off bus I,

33.3 ~ 34.0 ms cut off bus II

–

K1BN-0-K2AN

9.5 ms cut off bus I,

10.0 ms cut off bus II

11.0 ~ 11.3 ms cut off bus I,

12.0 ~ 12.8 ms cut off bus II

–

Short circuit through the resistance

K1AN

11.0 ms cut off bus I

11.8 ~ 35.0 ms cut off bus I

–

K2AB

8.8 ms cut off bus II

11.3 ~ 14.5 ms cut off bus II

–

K4ABC

–

–

–

Bus coupler CB failure

K1AN

309.3 ms cut off bus II

295.5 ~ 296.3 ms cut off bus II

–

System oscillation and failure during oscillation

Oscillation period 300 ms

–

–

–

K1AN

8.3 ms cut off bus I

26.3 ~ 27.3 ms cut off bus I

Oscillation period 500 ms

K4CAN

–

–

Oscillation period 500 ms

PT break

Bus I PT single-phase break

–

–

–

Bus I PT three-phase break

–

–

–

K1AN

9.0 ms cut off bus I

10.8–11.8 ms cut off bus I

Bus I PT single-phase break

CT break

CT3 break

–

–

–

K1AN

9.0 ms trip bus coupler 1 CB, 159.0 ms cut off bus I

22.5 ms trip bus coupler 1 CB, 173.5 ms cut off bus I

CT3 break