A data center is located in an area where the demand for power is higher than the utility power company is able to deliver. This results in frequent power outages and, therefore, power shedding (scheduled/controlled power shutdown for areas) is frequently applied. The mains power is more than 650 hours/year not available. What type of generators should be installed?

The mains power is unavailable for over 650 hours per year, a duration that far exceeds the typical operational limits for Emergency Standby Power (ESP) generators (often limited to 200-500 hours/year). This scenario requires a generator system that can act as the primary power source for unlimited hours. Continuous Power (COP) rated generators are designed for this exact purpose, supplying a consistent load 24/7. For a mission-critical facility like a data center, high availability is paramount. An N+1 configuration provides the necessary redundancy to ensure continuous operation during maintenance or in the event of a single generator failure, thus eliminating a single point of failure.

A. Standby generators are not designed for the high number of annual operating hours required and would be misapplied, leading to premature failure.
C. This option proposes an overly complex, non-standard, and cost-prohibitive design. A 500% capacity is excessive and unnecessary for achieving reliability.
D. Omitting an N+1 configuration is unacceptable for a data center, as it creates a single point of failure in the primary power system.

1. ISO 8528-1:2018, "Reciprocating internal combustion engine driven alternating current generating sets — Part 1: Application, ratings and performance." This international standard defines the power ratings for generator sets.

Section 5.1.3.4, Emergency standby power (ESP): States that ESP is for supplying power during a utility power interruption for a limited duration. Annex A, Table A.1, notes a typical usage of up to 200 operating hours per year. The 650 hours in the scenario far exceeds this.

Section 5.1.3.1, Continuous power (COP): Defines COP as the power a generating set can deliver continuously for an unlimited number of hours per year under agreed operating conditions. This directly matches the requirement of the scenario.

2. Telecommunications Industry Association (TIA), ANSI/TIA-942-B, "Telecommunications Infrastructure Standard for Data Centers." This standard is a cornerstone for data center design and is referenced in CDCS principles.

Section 5.3, "Redundancy": This section details the requirements for different Rated (Tier) levels. For Rated-2 and higher, which any enterprise data center would be, it requires redundant (N+1) capacity components for the electrical system to avoid single points of failure. A data center with such an unreliable utility would require at least a Rated-3 design, which mandates concurrently maintainable (N+1) power infrastructure.

3. Uptime Institute, "Data Center Site Infrastructure Tier Standard: Topology." The Uptime Institute's Tier Standard is a globally recognized benchmark for data center reliability.

Tier III: Concurrently Maintainable: This tier requires N+1 redundancy for the power path, including engine generators. This allows any component to be taken out of service for planned maintenance without impacting the IT load. The scenario's high reliance on generators makes concurrent maintainability a critical design requirement.