Multi-Vendor Interoperability: Lessons from Real Substation Projects

We still remember the Saturday morning phone call from a site manager on a 132 kV substation upgrade in the north of England. Two protection relays from different manufacturers were refusing to exchange GOOSE messages, and the commissioning team was staring at a deadline. Both devices carried IEC 61850 certification. Both had passed factory acceptance testing. Yet on site, in the cold, with real fibre and real network switches, they simply would not talk to each other. That weekend taught us more about multi-vendor interoperability than any specification document ever could — and it is the reason we now write about the practical lessons from real substation projects rather than the theory.

Why Multi-Vendor Interoperability Matters in IEC 61850

The UK’s transition to a smarter, more flexible grid depends on competition. If every substation were locked into a single vendor’s ecosystem, innovation would stall, prices would rise, and utilities would lose the flexibility to adopt best-in-class technology for each function. That is why National Grid, SSEN, and the UK’s distribution network operators have all moved towards multi-vendor environments in their substation automation strategies.

The Drive for Vendor Diversity in UK Smart Grids

Regulatory pressure has accelerated this shift. Ofgem’s RIIO framework rewards network operators who demonstrate efficiency and innovation, and vendor diversity is one route to both. SSEN’s RIIO-ED2 trials, for example, have explored how mixed vendor protection and control architectures can support active network management and faster fault restoration. National Grid’s Viking Link project, the 765 km interconnector between the UK and Denmark, relied on coordinated automation across multiple suppliers to manage cross-border power flows reliably. In each case, the goal was the same: avoid single-vendor dependency without sacrificing reliability.

IEC 61850 as the Interoperability Backbone

IEC 61850 was designed precisely for this world. Its object-oriented data model, standardised communication services, and Substation Configuration Language (SCL) were intended to let a protection relay from one manufacturer publish data that a bay controller from another could consume without custom protocol mapping. In theory, any compliant device should interoperate with any other. In practice, the standard defines the envelope, not the letter — and the gaps between vendor implementations are where projects get into trouble.

Common Pitfalls in Multi-Vendor IEC 61850 Deployments

After more than a decade of commissioning multi-vendor systems across the UK and Europe, we see the same categories of problem recurring. They rarely stem from a device being “broken”; they stem from assumptions that were never tested until the devices met on site.

SCL File and Configuration Inconsistencies

SCL files are the single biggest source of multi-vendor friction. Each vendor’s engineering tool generates and interprets SCL slightly differently. We have seen ABB, Siemens, and GE devices each produce valid-looking SCL that failed to import cleanly into another vendor’s tool, often because of differences in how private extensions, dataset naming, or control block attributes were handled. A £10m Ofgem-funded interoperability project highlighted exactly this issue: the technical barriers were less about the protocol itself and more about toolchain and configuration mismatches between suppliers.

GOOSE Messaging and Network Design Challenges

GOOSE messaging is unforgiving. It is a layer-2 multicast protocol with strict timing requirements, and small design decisions have large consequences. Common failures we have diagnosed include:

• Publisher and subscriber configured with mismatched GOOSE control block references (GoCB) or dataset ordering.
• VLAN and priority tagging inconsistencies between vendors, causing messages to be dropped or delayed under load.
• Network switches that were not configured for multicast filtering, flooding GOOSE traffic across the substation LAN.
• Retransmission timing parameters interpreted differently, leading to missed messages during fault conditions.

Timing problems are particularly insidious because they often only appear under transient conditions — exactly when protection functions must operate correctly.

Lessons Learned from UK Substation Projects

The projects that succeed are rarely the ones with the fewest problems. They are the ones where problems were found early, in a controlled environment, before anyone was standing in a cold switch room against a deadline.

Early Vendor Collaboration and FAT/SAT Testing

On National Grid’s Viking Link project and in SSEN’s RIIO-ED2 trials, the most valuable decision was bringing all vendors to the table during the design phase, not after. Joint factory acceptance testing (FAT) with devices from every supplier connected to the same network allowed configuration mismatches to be resolved before shipping. Site acceptance testing (SAT) then validated the same behaviour on the real installation. We now insist on a “multi-vendor FAT” as a contractual milestone — it costs a few days in the factory and saves weeks on site.

The Role of Independent Test Equipment

You cannot troubleshoot interoperability with the same vendor tools that created the problem. Independent test equipment is essential. Omicron’s CMC and DANEO platforms, for example, allow us to inject and analyse GOOSE traffic, measure latency, and verify SCL consistency without relying on any single vendor’s interpretation. This gives the commissioning team an unbiased view of what is actually happening on the wire.

Best Practices for Ensuring Interoperability

Based on what we have seen work, interoperability is not luck — it is a process. The following practices consistently reduce risk on multi-vendor IEC 61850 projects.

Unified Engineering and SCL Management

Treat the SCL file as a controlled engineering artefact, not a by-product of each vendor’s tool. Appoint a single system integrator or engineer to own the system-wide SCL, enforce naming conventions, and validate every import and export. UK Power Networks’ digital substation initiatives have demonstrated the value of this approach, using a centralised configuration management process to keep multiple vendors aligned across successive projects.

Network Redundancy and Cyber Security Considerations

Interoperability and resilience go hand in hand. We recommend:

1. Implementing PRP (Parallel Redundancy Protocol) or HSR (High-availability Seamless Redundancy) where protection criticality demands it.
2. Documenting VLAN, multicast, and QoS policies in a single network design that all vendors must follow.
3. Applying IEC 62351 security guidance to GOOSE and MMS traffic, and testing that security controls do not break timing.
4. Verifying compliance with UK grid codes and National Grid’s technical specifications before commissioning.

The Future of Multi-Vendor IEC 61850 in Europe

The direction of travel is clear: more vendors, more virtualisation, and more regulatory scrutiny. The question is whether the industry’s engineering practices can keep pace.

Digital Substations and Virtualisation

Digital substations replace copper wiring with fibre and merge units with process buses, which multiplies the number of interoperable interfaces in a single installation. Edge computing pushes analytics closer to the bay, introducing new software vendors into environments that were once purely hardware. Each of these trends increases the value of IEC 61850 — and the cost of getting interoperability wrong.

Regulatory and Standardisation Drivers

ENTSO-E’s work on grid connection codes and the European Commission’s push for a more integrated energy market both depend on standardised, vendor-neutral automation. In the UK, Net Zero targets are driving massive investment in offshore wind, interconnectors, and distribution flexibility — all of which rely on multi-vendor IEC 61850 systems working first time. The standards are evolving, but the engineering discipline has to evolve with them.

Multi-vendor interoperability in IEC 61850 is genuinely difficult, and anyone who claims otherwise has not commissioned a real substation. But it is not unmanageable. The projects that succeed — Viking Link, SSEN’s RIIO-ED2 trials, UK Power Networks’ digital substations — share common habits: early vendor engagement, rigorous multi-vendor FAT and SAT, independent test equipment such as Omicron, disciplined SCL management, and clear network design. Get those right, and vendor diversity becomes a strength rather than a risk.

FAQ

What is multi-vendor interoperability in IEC 61850?

It means devices from different manufacturers — for example, an ABB relay, a Siemens bay controller, and a GE gateway — exchanging data and control messages over the same IEC 61850 network without custom protocol conversion. The standard is supposed to make this possible, but real-world implementation still requires careful engineering.

Why do GOOSE messages fail between different vendors?

Most GOOSE failures come down to configuration, not protocol defects. Mismatched control block references, dataset ordering, VLAN tagging, or retransmission parameters are the usual culprits. Independent test tools like Omicron are the fastest way to identify which side is misconfigured.

How can we reduce SCL file problems on a multi-vendor project?

Appoint one party to own the system-wide SCL, enforce strict naming and version control, and validate every import and export against a reference model before site delivery. Running a joint factory acceptance test with all vendors connected is the single most effective safeguard.

Is PRP or HSR necessary for multi-vendor substations?

Not always, but for protection-critical GOOSE traffic we strongly recommend at least one redundancy mechanism. PRP is often simpler to deploy across mixed vendor environments, while HSR suits ring topologies within a single bay or panel.

What role does Ofgem play in UK interoperability projects?

Ofgem funds innovation through mechanisms such as the Network Innovation Competition and RIIO-ED2 allowances. A £10m Ofgem-funded project specifically examined interoperability barriers between vendors, and its findings continue to shape how UK DNOs specify and test IEC 61850 systems.