Operational Telecoms

Operational telecoms is the dedicated telecommunications network that transmission and distribution operators build and maintain to carry their own operational traffic — SCADA telemetry, protection signalling, inter-trip commands, and operational voice — between substations, switching stations, and control centres.

Physical infrastructure

The backbone of most transmission operational telecoms networks is OPGW (Optical Ground Wire) — a composite cable that serves double duty as the lightning earth conductor strung along the top of transmission pylons and as a fibre-optic data carrier. The fibres sit inside a steel and aluminium sheath that is earthed at each tower, so the cable protects the power conductors below from lightning strikes while simultaneously carrying gigabits of operational data between substations.

Where OPGW is not feasible — older routes where the earth wire cannot be replaced, or distribution circuits on wooden poles — operators use:

• ADSS (All-Dielectric Self-Supporting) fibre cable, lashed below the power conductors.
• Microwave radio links, typically as redundant paths or for remote sites without fibre access.
• Leased circuits from commercial carriers (e.g., carrier MPLS), though the trend is to bring critical operational traffic back onto owned infrastructure.

Why it matters

The operational telecoms network is the physical transport layer underneath everything else in the digital substation. The DNP3 or IEC 60870-5-104 traffic between an RTU and the control-centre EMS, the inter-substation protection signalling that coordinates tripping across a transmission line, and the operational voice circuits that control-room operators use during switching — all of it rides on the operational telecoms network.

Owning the transport layer gives the operator control over latency, bandwidth, and — critically — the security boundary. Traffic on an OPGW fibre inside the earth wire of a 400 kV pylon is physically difficult to tap without being noticed. That physical security is part of the defence-in-depth argument for why some operators have historically run SCADA protocols in plain text — the network itself was treated as the security control.

Refresh cycles

Operational telecoms infrastructure is refreshed through the same regulatory price controls that fund substation equipment. OPGW has a design life broadly aligned with the pylons and overhead line conductors it is strung on (40–60 years), but the active telecommunications equipment at each end — multiplexers, routers, SDH/MPLS nodes — refreshes on a 10–15 year cycle, similar to SCADA and RTU hardware.