Utility & industrial automation · Case 04
Automating protection-system monitoring on an SEL RTAC
A protection scheme is only as good as its weakest un-checked relay. This engagement moved settings verification and device-health monitoring off a maintenance clipboard and onto an SEL Real-Time Automation Controller that watches every intelligent electronic device continuously.
The problem
Protective relays drift. Settings get changed during a maintenance window and not changed back; a communications card degrades; a relay quietly stops seeing one phase. In most plants none of that surfaces until a fault arrives and the protection either misoperates or fails to operate — the most expensive possible time to learn about it. Manual setting audits catch it eventually, but "eventually" is measured in months.
The approach
I built controller logic on an SEL RTAC that polls each IED on a fixed interval, issues the read commands the device understands, and computes a rolling CRC over the returned settings so any change is flagged the moment it happens. The same logic watches device self-diagnostics and channel status, and speaks the three protocols the plant actually runs on — DNP3 to SCADA, Modbus to third-party equipment, and IEC 61850 GOOSE for the sub-cycle interlocking between relays. Where the standard and the configuration tooling disagreed, the reference notes in the vault document how the mapping was resolved.
The result
Continuous, automatic verification of relay settings and health, with misoperation-prone conditions surfaced as they appear rather than discovered after a trip. One screen shows the state of the protection system; a setting change raises a flag the same day, not the next audit.
Client identity withheld. Drawings, configurations, and deliverables are available under mutual NDA. Configurations reference published SEL guidance, credited on the notes page.
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