Turning a testing roadblock into innovation: How Wirtek used AI to validate IEC 62351-5 in IEC 60870-5-104

When implementing security standards in critical infrastructure, theory is never enough. You need real-world testing conditions to prove that what you build actually works.

That was exactly the challenge Wirtek faced during a recent project involving the implementation of IEC 62351-5 security extensions in an IEC 60870-5-104 (IEC 104) protocol gateway for a client in the energy sector.

The challenge

No RTU, no simulator, no way forward

The task was clear: implement IEC 62351-5 to secure IEC 104 communication. The problem was less obvious, but critical.

There was no physical RTU available for testing. And unlike more mainstream protocols, there was no off-the-shelf simulation tool capable of properly emulating an IEC 104 RTU with IEC 62351-5 security behavior.

"As engineers, we rely heavily on realistic test counterparts", explains Filipe Fernandes, Engineering Lead at Wirtek. "When you're dealing with security protocols in the energy sector, assumptions are dangerous. We needed a way to test real behavior, not just validate code against a specification".

Waiting for hardware or tooling was not an option. The project needed a different approach.

If the RTU doesn't exist, build one

Instead of blocking progress, the team reframed the problem: What if we could create the missing RTU?

Using AI-assisted development with ChatGPT, Wirtek engineers designed and implemented a virtual RTU capable of:

• Speaking IEC 60870-5-104

• Implementing the relevant IEC 62351-5 security mechanisms

• Acting as a realistic communication peer for the gateway under development

"The goal was never to create a mock or a simplified simulator" comments Fernandes. "We wanted something that behaved like a real RTU from a protocol and security perspective, so that our gateway was tested under realistic conditions".

AI as an engineering partner, not a shortcut

AI was not used to "auto-generate" a solution, but as a collaborative engineering tool:

• Accelerating protocol logic design

• Exploring edge cases in secure communication flows

• Iterating quickly on message handling and validation scenarios

"AI helped us move faster, but it didn't replace engineering thinking", Filipe Fernandes notes. "It acted as a sounding board and accelerator, especially when reasoning about protocol sequences and error cases. The final responsibility, and validation, was always ours".

Human expertise remained central. AI helped compress time, not replace judgment.

The outcome

Secure testing without physical constraints

By creating a virtual IEC 62351-5 enabled RTU, Wirtek was able to:

• Fully test and validate its IEC 104 gateway implementation

• Reduce dependency on scarce hardware and external tooling

• Deliver with confidence despite infrastructure limitations

"What started as a workaround quickly became a strength", says Filipe. "We now have a reusable asset that can support future projects and reduce risk in early development phases".

Why this matters for the energy sector

As power grids and critical infrastructure become more secure, and more complex, testing environments are increasingly the bottleneck, not standards or specifications.

"This is a good example of how AI can be applied responsibly in critical systems", Filipe Fernandes adds.
"It's not about replacing systems or bypassing standards, it's about enabling better testing, better validation, and ultimately more reliable solutions".

Looking ahead

At Wirtek, this project reinforced a simple principle: Innovation doesn't always mean new standards or new protocols, sometimes it means new ways of solving very practical problems.

By combining deep protocol knowledge with AI-assisted development, Wirtek continues to help clients navigate the evolving demands of secure, standards-based energy systems.