[Level 3] [NSEWL] Traction Power Trip bt ~~~~~ 675/676 Traction Power Trip btw BBT - JUR NB: L3 Traction power tripped btw BBT - JUR NB (on single feed). Standby for update. (sent at 09:05 14-Jul-2023) 675/676 was affected by power trip, pls check at depot. Down UPD 14/07/23. L3 675/676 line voltage dipped from 750vdc to 400vdc. Line voltage maintained at 400vdc, P4 commanded throughout. FC HBOL triggered on #1675,#2675 & #1676. Common FC propulsion fault & propulsion lost power for control triggeredfor all 4 M-cars. Line voltage decayed to zero for 10 seconds. From fault trace, motor torque , INV 1/2 input/output zero despite P4 commanded. Motor frequency decaying. Trian speed decreasing due to decreasing line voltage. Inverter no current due to upstream cut-out. HB not opened as commanded . HB feedback signal - Satis. Low DC input detected. Meggar all 4 M cars, TM 1-4 - Satis. No earth fault triggered. No abnormal spark during limited movement. ER showed Inverter did not cut-out, signifying downstream - OK. Fault trace, Inverter no current due to upstream cut-out. Meggar all cars filter reactors - Satis. limited movement, all HB/LB able to energise & contact tips condition - OK, no abnormal spark or burnt marks. No line voltage spiked, main/auxillary fuse - OK. Meggar all car surge arresters - satis. CCD shoes/fuses condition - OK. Postulate #2676 HB tripping mechanism faulty & contact unable to open during time of high current surge. Replaced #2676 HB. OPS 20 raised for M/L test to verify any power fault triggered & powering current abnormalities.  Lee JC 45130 Pending MLT. L3 675/676 M/L test - Passed. No occurrance of power fault.  Celine Tan 45131