Bulgarian Data Center Power Distribution Box Configuration

Data center power distribution in Bulgaria follows international best practices for redundancy and safety, aligned with the Bulgarian Grid Code for auxiliary networks and control systems.

Regulatory Context in Bulgaria

In Bulgaria, the Bulgarian Grid Code governs the planning, operation, and development of transmission and auxiliary networks, including data center power infrastructure. It sets requirements for reliability, quality of power supply, and coordination between transmission system users and operators, ensuring that auxiliary networks and control systems meet safety and operational standards (ESO Grid Code, Art. 6, 7) . Data centers must comply with these regulations when connecting to the national grid and designing internal distribution systems.

Power Distribution Architectures

Data centers typically implement redundant power distribution topologies to ensure continuous operation:

• System + System (2N): Two independent systems feed critical loads, often used for dual-corded IT equipment. This provides maximum reliability but limits utilization to 50% of installed capacity .
• System + Utility: Combines an N+1 UPS system with a utility feed without UPS, suitable for small to mid-size data centers .
• Shared Redundant (3N/2, 4N/3): Multiple systems feed fewer loads to improve utilization (66–75%) while maintaining redundancy .
• Block Redundant (Catcher Topology): Uses a static transfer switch (STS) to switch loads between active and reserve UPS, allowing up to 80% utilization .

Key Equipment and Configuration

Medium-Voltage (MV) Switchgear

• MV switchgear receives utility power and includes meters, breakers, contactors, fuses, surge arresters, voltage/current transformers, and control relays .
• Typically arranged in cubicles: incoming unit, outgoing unit, voltage metering unit, and bus section.
• Each cubicle has a single MV circuit breaker to manage high-voltage flows safely .

Low-Voltage (LV) Switchgear and Automatic Transfer Switches (ATS)

• LV switchgear distributes power from MV/LV transformers or backup generators to critical IT loads.
• Components include incoming feeders, power control centers (PCC), motor control centers (MCC), busbars, circuit breakers, meters, surge arresters, and relays .
• ATS ensures seamless transfer between primary and backup power sources.

Power Distribution Units (PDUs) and Remote Power Panels (RPPs)

• PDUs distribute power from UPS units to IT racks, controlling, monitoring, and protecting the load.
• Typical PDUs include main input breakers, branch circuit panels, transformers, surge arresters, and monitoring modules.
• Rated for 50 kW to 500 kW depending on the data center size .

Design Considerations

• Redundancy: Critical IT loads should be dual-corded and connected to independent UPS paths.
• Protection: All components must be protected against over-current and short-circuit conditions, with rated short-circuit withstand currents defined for switchgear and panelboards .
• Monitoring: Integration of meters and communication modules for real-time monitoring and fault detection.
• Compliance: Designs should align with Bulgarian Grid Code requirements for auxiliary networks and international standards for Tier III/IV data centers .

Summary

Bulgarian data center power distribution boxes are configured using redundant architectures (2N, 3N/2, block redundant), with MV and LV switchgear, ATS, PDUs, and RPPs. Designs must ensure reliability, safety, and compliance with the Bulgarian Grid Code while following international best practices for redundancy, protection, and monitoring. Proper configuration supports uninterrupted IT operations and efficient energy management.