Two substation-hardened servers, both certified to IEC 61850-3 and IEEE 1613, both built to run virtualized protection, automation and control. They are not competing products. They answer different requirements, and the vPAC Alliance hardware specification explains why better than any datasheet can.
Start with the Profile Levels
The question we get most often is which server is "better." According to the vPAC Alliance hardware specification, that is the wrong question. The specification does not define a single server platform. Instead, it defines four profile levels because substations differ significantly in size, workload, cooling options, and operational requirements.
The result is a framework that allows utilities to select the right platform size without changing architecture, software stack, or cybersecurity model. All profile levels support the same vPAC ecosystem, differ mainly in performance and deployment scale, and remain interoperable.
| Profile Level | Characteristics |
| Level 1 | Smallest, fanless, highly ruggedized platform for limited workloads |
| Level 2 | Fanless platform with greater thermal capacity for medium-sized substations |
| Level 3 | Actively cooled platform with increased compute and memory resources |
| Level 4 | Largest profile intended for centralized protection, control, and AI/ML workloads |
Table 1 — The four vPAC Alliance hardware profile levels.
The RSAPC Mk2 targets Profile Level 2, while the RSAVP is designed for Profile Level 4 environments.
Designed for Substations from Day One
Both platforms were designed specifically for digital substations rather than adapted from conventional IT equipment. Their certifications, mechanical layout, power architecture, and environmental capabilities were incorporated from the beginning of the design process.
Both systems comply with IEC 61850-3 and IEEE 1613 requirements, support operation from station DC supplies, and are optimized for industrial environments where reliability, service life, and maintainability matter more than peak benchmark numbers.
Welotec contributes directly to the vPAC Alliance hardware working groups, which means the profile specifications and the hardware platforms evolved together rather than independently.
RSAPC Mk2: The Fanless Workhorse
The RSAPC Mk2 is a 19-inch, 2U fanless server with fully passive cooling and an operating temperature range of −40 °C to +70 °C. No moving parts are required for cooling, eliminating an entire category of maintenance activities.
Processor Options
| CPU | Cores / Threads | Base / Turbo | L3 Cache |
| Intel Xeon W-11555MLE | 6 / 12 | 1.9 / 4.4 GHz | 12 MB |
| Intel Xeon W-11865MLE | 8 / 16 | 1.5 / 4.5 GHz | 24 MB |
Table 2 — RSAPC Mk2 processor options.
The platform supports up to 128 GB DDR4 memory, four hot-swap SATA drives, multiple PCIe expansion slots, TPM 2.0, eight integrated 2.5 GbE copper ports, and Intel AMT for out-of-band management. Supported operating systems include SEAPATH, Red Hat Enterprise Linux Real Time, VMware ESXi, Ubuntu, Debian, and Windows Server.
Where the RSAPC Mk2 Excels
- No moving parts and therefore minimal maintenance requirements
- Wide operating temperature range from −40 °C to +70 °C
- Eight integrated 2.5 GbE copper ports
- Flexible AC and DC power supply options, including mixed-source redundancy
- Validated real-time performance with SEAPATH clusters
- Processor availability through 2035
The primary limitations are maximum memory capacity, lower CPU core counts, and limited support for hardware accelerators such as GPUs.
RSAVP: Built for Consolidation and Scale
The RSAVP represents Profile Level 4 and targets large-scale vPAC deployments. It is a 19-inch, 3U platform with hot-swap industrial fans, redundant power supplies, hot-swap NVMe storage, and dedicated server management through IPMI and Redfish.
Processor Options
| CPU | Cores / Threads | Base / Turbo | Cache | Architecture |
| Intel Xeon 6515P | 16 / 32 | 2.3 / 3.8 GHz | 72 MB | Granite Rapids P-Core |
| Intel Xeon 6736P | 36 / 72 | 2.0 / 4.1 GHz | 144 MB | Granite Rapids P-Core |
| Intel Xeon 6710E | 64 / 64 | 2.4 / 3.2 GHz | 96 MB | Sierra Forest E-Core |
Table 3 — RSAVP processor options.
The platform supports up to 512 GB DDR5 ECC memory, four U.2 NVMe drives with capacities up to 16 TB, PCIe Gen5 expansion, accelerator cards, and fiber-based networking with 1 GbE and 10 GbE SFP interfaces.
Choosing the Right CPU
- Xeon 6515P: Best for maximum real-time performance and latency-sensitive protection applications.
- Xeon 6736P: Balanced option combining high core counts with a large cache for mixed workloads.
- Xeon 6710E: Optimized for virtualization density, consolidation, and AI/ML processing.
Short version: 6515P for latency margin, 6736P for balance, and 6710E for density.
RSAPC Mk2 vs. RSAVP
| Characteristic | RSAPC Mk2 | RSAVP |
| vPAC Profile Level | Level 2 | Level 4 |
| Cooling | Fanless, passive | Active, hot-swap fans |
| Form Factor | 19", 2U | 19", 3U |
| Operating Temperature | −40 °C to +70 °C | −40 °C to +55 °C |
| Memory | Up to 128 GB DDR4 | Up to 512 GB DDR5 ECC |
| Storage | Up to 4 TB SATA | Up to 16 TB NVMe |
| Accelerator Support | Limited | Fully supported |
| Management | Intel AMT | IPMI and Redfish |
Table 4 — Side-by-side comparison of the RSAPC Mk2 and RSAVP platforms.
Which Platform Should You Choose?
Choose the RSAPC Mk2 when fanless operation, high ambient temperatures, limited cabinet space, or station-level workloads are the primary requirements. It is particularly well suited for brownfield modernization projects and small to medium-sized substations.
Choose the RSAVP when consolidating large substations, running centralized protection and control architectures, supporting AI/ML applications, or managing large fleets of systems through automated infrastructure management.
The Answer Is Often Both
The vPAC Alliance architecture explicitly allows heterogeneous server ensembles. Servers of different profile levels, sizes, manufacturers, generations, and performance classes can coexist within the same virtualized architecture.
This enables designs such as using RSAVP systems as primary compute nodes while RSAPC Mk2 platforms provide quorum services and lighter workloads. Utilities can also standardize on one software stack while deploying different hardware sizes for transmission and distribution substations.
Facts at a Glance
- RSAPC Mk2 targets vPAC Alliance Profile Level 2
- RSAVP targets Profile Level 4
- Both platforms comply with IEC 61850-3 and IEEE 1613
- Both support the same virtualization architecture and software ecosystem
- RSAPC Mk2 is optimized for fanless operation and harsh environments
- RSAVP is optimized for consolidation, AI/ML workloads, and large-scale deployments
- The vPAC architecture supports heterogeneous server clusters
- The selection is primarily a sizing decision rather than an architectural one
In short: The RSAPC Mk2 is the rugged, fanless platform for station-level virtualization and smaller substations, while the RSAVP provides the performance, scalability, and manageability required for large-scale vPAC deployments. Both are designed for the same architecture, allowing utilities to combine them as requirements evolve.
