As global energy systems accelerate toward digitalization with an increase in renewable energy and distributed energy resources (DERs), operating conditions for substation protection, automation, and control (PAC) are getting very complex. To address these challenges, utilities are seeking modern solutions that offer flexibility, scalability, ease of management, and cross-vendor integration, shinning a spotlight on the software-defined substations (SDS) architecture.

At its core, SDS is more than just substation software. It represents a fundamental paradigm shift in the design of PAC systems—moving away from hardware-centric intelligent electronic devices (IEDs) to a model defined by modular software components, platform-based architecture, and open standards.

Currently, the most significant substation transitions are occurring at two levels:

• Bay Level: Testing, control, and protection functions are being decoupled from hardware and re-implemented as virtual IEDs (vIEDs).
• Station Level: All services are being virtualized and hosted on centralized server platforms.

These two developments mutually reinforce each other, transforming virtualization from a mere technical choice to fundamental capabilities for streamlining substation architecture and enhancing operational efficiency.

International collaboration is further accelerating the realization of SDS. The Virtual Protection, Automation, and Control (vPAC) framework—driven by the vPAC Alliance and LF Energy’s Software Enabled Automation Platform and Architecture (SEAPATH) project—is being validated through proof-of-concept activities within the open energy ecosystem. Publicly available initiatives have involved organizations such as LF Energy and European grid operators, including RTE, TenneT, and Alliander.[1] Through open-source, real-time, and vendor-neutral virtualization platforms, these initiatives are shaping a new generation of substations built around platform-centric architectures.

The Core Drivers and Values Behind Practical SDS: Inside vPAC

The core philosophy of SDS is to consolidate functions, previously scattered across multiple physical IEDs, into a shared platform. This approach allows functions to be defined by software, deployed uniformly, and managed centrally, rather than being restricted by hardware.

Within this architectural shift, vPAC plays a pivotal role in the practical realization of the SDS vision. It transitions PAC from its legacy dependence on proprietary hardware to a software-defined framework characterized by centralized management, rapid deployment, and elastic scalability. Protection and control functions are no longer tethered to physical IED constraints; instead, they operate as vIEDs on a shared, redundant, and highly observable platform. This is far more than a simple change—it signifies PAC’s evolution into a new era of manageability, adaptability, and standardization.

For engineering and operations, vPAC delivers highly pragmatic values:

• Enhanced Resilience and Availability: vIEDs can automatically failover between cluster nodes and shared resources, providing redundancy that far exceeds traditional hot standby mode.
• Efficient Life Cycle Management: Functional updates and security patches can be deployed via automated software workflows, eliminating the need for manual, updates and ensuring consistent, scalable, and controlled maintenance.
• Extended Interoperability: Adhering to open standards, like IEC 61850 and vPAC, allows modules from different vendors to coexist on a single platform, ensuring long-term compatibility.
• Reduced Vendor Lock-in: Since PAC functions are no longer tied to specific hardware, utilities gain greater technical autonomy and flexibility during system upgrades.

Ultimately, vPAC gives you the ability to incrementally modernize your substations without operational downtime while significantly reducing O&M costs.

From Substation Automation to vPAC: Platform Reliability Takes Center Stage

vPAC marks a significant leap forward in substation resilience and operational methodology. By leveraging virtualization to host PAC functions, systems achieve unprecedented consistency in failover mechanisms, update procedures, and centralized management. This shift provides the agility necessary for substations to navigate the complexities of the global energy transition. However, even the most flexible virtualization layer must be anchored by a rock-solid hardware foundation; without inherent platform stability, the most comprehensive vPAC architecture remains a purely theoretical framework.

IEC 61850-3 standards require substation-grade equipment to possess high environmental endurance and electromagnetic compatibility (EMC). As unmanned and remotely operated substations become the norm, the demand for visibility, manageability, and remote updates are increasing. Consequently, the reliability of the hardware platform has become a prerequisite for the successful deployment of SDS.

Research from international organizations, such as CIGRE, EPRI, and European TSOs (like RTE), confirms that the viability of  vPAC depends on whether hardware can maintain these critical characteristics in real-world grid environments. As pilot projects accumulate empirical data, the long-term reliability of hardware in substation settings has become a focal point for the international technical community. This scrutiny has led to a re-evaluation of the role of IEC 61850-3 certified servers in the SDS ecosystem. The vPAC Alliance has proposed specific hardware profiles for different substation levels—such as L2 profiles featuring fanless, IEC 61850-3 certified servers designed for unmanned sites, providing a standardized benchmark for evaluating the suitability of virtualization platforms.

In this new landscape, grid operators worldwide are exploring diverse implementation paths for SDS and vPAC tailored specific to their infrastructure and digital maturity. These approaches, ranging in virtualization depth, hardware configurations, and integration strategies, continue to evolve. The progression of the transformations reveals an undeniable trend—vPAC is fundamentally redefining the technical DNA of next-gen substations. As the SDS architecture takes form, defining the technical pillars and essential traits required for its long-term viability remains a vital dialogue—a journey of exploration that will ultimately shape the next chapter of grid evolution.

[1]LF Energy Project introduction:  https://lfenergy.org/projects/seapath/