Application ScenariosA 780 MW combined-cycle plant running Bailey INFI 90 on the balance-of-plant had a chronic headache: during a grid-disturbance event, the gas-turbine breaker, the generator breaker, and the unit-transformer secondary breaker would all trip within a 50 ms window, but the plant’s existing NRDI02+RDI nodes (10 ms SOE at 125 V DC) couldn’t resolve the sequence — the SOE log showed all three “OPEN” events in the same 10 ms bucket. The root-cause debate between the turbine OEM and the utility dragged on for three months. The retrofit added an ABB NTST01​ + IMSTM01 SOE node dedicated to the trip-chain: landed the GT-breaker 125 V DC aux (NO+NC), the generator-breaker 125 V DC aux, and the unit-xformer secondary 125 V DC aux on the NTST01‘s 16 CH (filled 6 CH, left 10 spare for future protection relays). The IMSTM01 timestamped at 1 ms resolution using the INFI-Net’s time-broadcast from the GPS-synced NTP node. Next grid event: the SOE showed GT-breaker opened at T+0 ms, gen-breaker at T+18 ms, xformer-secondary at T+34 ms — definitive proof the GT tripped first (exciter upset), cascading to gen then xformer. The three-month debate ended in one morning. The plant now specs NTST01+IMSTM01 for every new breaker/trip chain instead of reusing NRDI02 bandwidth.

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Technical Principles and Innovative Values

• Innovation Point 1: 1 ms Forensic Edge-Capture via IMSTM01 + NTST01 Split.​ The NTST01​ itself doesn’t timestamp — the IMSTM01 SOE Master does, using the INFI-Net broadcast time (synced to GPS/NTP at the plant level). But the NTST01‘s role is critical: its 98 V ON / 91 V OFF hysteresis at 125 V DC, combined with 1500 V channel isolation, ensures the IMSTM01 sees a single clean rising/falling edge per contact event — no bounce, no induced glitch from the 6 kV switchyard. That clean edge is what lets the IMSTM01 lock 1 ms resolution instead of smearing across a 10 ms bucket (which is what happens if you try to do forensics on a plain NRDI02 node).
• Innovation Point 2: Same 125 V DC / 120 V AC Wetting World as NRDI02, But Dedicated to SOE.​ The NTST01​ speaks the same field language as the NRDI02 we covered earlier (125 V DC breaker aux, 120 V AC MCC run-status), but it’s wired to a different smart card(IMSTM01 instead of RDI). This lets plants partition: put the “routine” 125 V DC DI on NRDI02+RDI (10 ms SOE is fine for routine alarms), and put the “forensic” trip-chain on NTST01+IMSTM01 (1 ms for root-cause). Both TUs can sit in the same satellite termination cabinet, fed from the same 125 V DC yard UPS.
• Innovation Point 3: NKST Ribbon + Per-Channel LED for Commissioning Speed.​ The NTST01​ fronts a status LED per channel (ON = wetting current flowing = contact closed). During commissioning of a 16-channel trip-chain node, a technician can stand at the termination cabinet, trip a breaker at the switchyard, and watch CH-3 LED flip — confirm the ribbon to IMSTM01 is alive without walking back to the MFP rack with a PG laptop. The NKST ribbon keys the same way as NKDI/NKDS — forcing wrong-way bends pins, so train staff on the latch.