arXiv:2610.28324v1 Announce Type: new Abstract: Deterministic industrial networks often present an operational trade-off between maintaining microsecond timing of primary control loops and capturing security telemetry. This work investigates the engineering feasibility of the Operational Technology Supervisor (OTSV), a three-tier passive monitoring framework designed to resolve this visibility challenge within timing-sensitive grid-edge infrastructure. By utilizing a Layer-3-unconfigured passive ingestion mode on bare-metal hardware via a physical switched port analyzer (SPAN) loop, the deep packet inspection engine is isolated from the production network, implementing a software-enforced unidirectional export policy. Performance validation conducted over a continuous audit comprising 32,927 active-monitoring round-trip time (RTT) samples yielded stable latency distributions across a laboratory power-monitoring loop running Modbus TCP and IEC 61850 MMS protocols. The measured latency delta between the unmonitored baseline and the active monitoring state was less than 0.12 milliseconds, supporting the feasibility of continuous high-fidelity security observation alongside stringent grid-edge metering timing bounds without measurably degrading the monitored reporting path.