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CDCP: Data Centre Power Infrastructure

CDCP · Work through your exam, one topic at a time.

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Data Centre Power Infrastructure

This domain tests the electrical path from utility to rack: redundancy topologies, UPS and generator sizing, battery behaviour, switching, grounding, and failure modes. Questions often hinge on unit conversions, load growth, or whether a redundancy label actually removes a single point of failure.

Electrical chain and redundancy

  • Typical path: utility → MV switchgear → transformer → LV switchgear → ATS → generator/UPS → PDU → busway → rack PDU.
  • N means no redundancy; N+1 adds one spare capacity component; 2N provides two independent systems; 2(N+1) combines both. Only 2N and 2(N+1) remove many single points of failure, and only if the paths are truly independent.
  • UPS types include double-conversion (VFI), line-interactive, and rotary. Double-conversion isolates the load from utility disturbances but is less efficient than eco-mode operation.
  • Batteries may be VRLA, flooded lead-acid, or lithium-ion. Autonomy depends on load, end-of-life capacity, temperature, and discharge rate.
  • Generators need fuel, cooling, starting reliability, and load acceptance. An ATS transfers load, but generator startup and transfer time must match the UPS ride-through.
  • Bonding and grounding must be designed as a system; isolated grounds and loose bonding create safety and noise problems.

Sizing rules

  • Work in kW for heat/load and kVA for equipment rating; convert with power factor.
  • Apply growth, diversity, derating, and efficiency. Do not size a UPS to run continuously at 100%.

Worked example - UPS and generator sizing. IT load is 200 kW at 0.9 PF with 20% growth. Design load = 200 × 1.2 = 240 kW; required output = 240 / 0.9 = 267 kVA. Select 300 kVA UPS modules. For N+1, two 300 kVA modules allow one module to carry the load while the other is maintained. For 2N, use two independent 300 kVA UPS systems with separate distribution. The generator must carry the 240 kW load plus UPS charging, cooling, and starting margin, not just the UPS nameplate.

Traps that cost marks

  • Mixing kW and kVA or ignoring power factor.
  • Assuming N+1 protects against a shared downstream PDU or single feed.
  • Sizing batteries at beginning-of-life capacity with no end-of-life margin.
  • Forgetting generator step-load, fuel, and cooling requirements.
  • Treating an ATS as instantaneous; transfer time matters.