Data center backup power is a critical infrastructure to ensure business continuity, especially in the event of a main power outage, backup power sources (such as diesel generators) need to respond quickly and provide stable power. Some shallow research and discussion have been conducted on this, starting from the requirements of standard specifications, exploring its performance requirements, and providing some suggestions for the selection of diesel generator sets.
1, Standard specifications
In terms of regulatory requirements, international and domestic standards are taken into account. For example, GB50174, Uptime Institute Tier standards, NFPA 110, GB 50052 and other standards have different requirements for backup power sources at different levels. If it is necessary to provide detailed explanations for each standard, a lot of time would be spent researching and interpreting them. Simply identify some key points, such as power supply time, switching time, etc. In addition, the redundancy configuration of backup power supply is also crucial, such as N+1 or 2N structure, which need to be determined according to the data center level required by the user.
According to GB50174-2017 Design Specification for Data Centers, Class A data centers should be powered by dual power sources and equipped with backup power sources. The backup power source can be a diesel generator set that is independent of the normal power source, or a dedicated feeder line in the power supply network that is independent of the normal power source. When the normal power supply fails, the backup power supply should be able to bear the power load required for the normal operation of the data center. In addition, the performance level of the diesel generator set of the backup power source should not be lower than G3 level, and the generator set of the A-level data center should operate continuously and without time limit, and the output power should meet the needs of the maximum average load of the data center.
According to the American Communications Industry Association standard ANSI/TIA-942, the availability of data center infrastructure is divided into four levels: Tier I,Tier II,Tier III,Tier IV. These levels are mainly divided based on the availability, stability, and security of the data center. Tier IV data centers have the highest availability requirements, with fault-tolerant infrastructure systems that can ensure normal operation even in the event of multiple device or system failures.
In addition, NFPA 110 (National Fire Protection Association) stipulates that backup power systems must be activated within 10 seconds and support full load operation for at least 24 hours. GB 50052 Code for Design of Power Supply and Distribution Systems: It is required that the switching time of backup power supply should be ≤ 15 seconds, and important loads should meet the requirement of 0 second switching (through UPS transition).
2, Performance requirements
Performance requirements include reliability, start-up time, load capacity, fuel storage, noise and emissions, maintainability, and monitoring systems. For example, the backup power supply must be started within a few seconds after the main power supply is interrupted, and specific values may be required, such as reaching full load within 15 seconds. In terms of fuel storage, it should support at least 24 hours of full load operation, which may vary depending on the location of the data center, such as requiring longer fuel reserves in remote areas. Specifically, as follows:
1. Reliability
The success rate of startup ≥ 99%, and the average annual failure time should be less than 0.5%.
O Support frequent start stop (tested at least 12 times a year).
2. Response time
Cold start time ≤ 10 seconds, hot start time ≤ 5 seconds.
The total time from interruption of the main power supply to full load power supply ≤ 15 seconds.
3. Load capacity
Capable of withstanding sudden loads (such as 100% load step) with voltage/frequency fluctuations of ≤± 5%.
The long-term operating power needs to cover 110% -120% of the total load of the data center (considering future expansion).
4. Fuel and endurance
The fuel tank capacity supports full load operation for more than 24 hours and reserves an external fuel supply interface.
The fuel type needs to be adapted (commonly used diesel, which must comply with the National VI/Euro VI standards).
5. Noise and emissions
Noise level: ≤ 85 dB (A) at a distance of 1 meter from the unit.
Emissions must meet EPA Tier 4 or EU Stage V standards.
6. Intelligent management
O Support remote monitoring (oil pressure, water temperature, battery status, etc.).
O Equipped with self-diagnosis and fault alarm functions.
3, Selection of Diesel Generator Sets
Choosing a suitable diesel generator set requires consideration of load capacity calculation, analysis of the total load of IT equipment, air conditioning, lighting, etc. in the data center, and consideration of future expansion. In terms of unit type, whether to choose the constant load or standby type, the importance of synchronous motors, and whether modular design is adopted. Brand and quality are also important, as users may prefer well-known brands but need to balance their budget. The installation environment should consider space, ventilation, smoke exhaust, shock absorption, and the possibility of parallel operation, as well as after-sales service and maintenance support.
Deep level needs that users may not have explicitly mentioned include cost-benefit analysis, how to control budgets while meeting regulations, or environmental requirements such as whether emission standards comply with local regulations. In addition, users may also be concerned about how to test the reliability of the generator set, such as regular load testing, and how to integrate with the existing power system, such as the setting of automatic transfer switches. Specifically, as follows:
1. Load capacity calculation
Total load=IT equipment load+ air conditioning (CRAC)+lighting+other auxiliary equipment.
Redundancy factor: Select the unit capacity based on 1.25-1.5 times the maximum load (to avoid carbon deposition caused by low load operation).
2. Selection of Unit Type
Standby type: suitable for short-term emergency power supply, with a lower price.
Prime: Supports long-term operation and is suitable for high reliability scenarios.
• Synchronous motor: Permanent magnet synchronous generators are preferred for higher efficiency.
Modular design: supports parallel operation of multiple units for easy expansion.
3. Brand and Quality
International brands such as Caterpillar, Cummins, Perkins, MTU, etc. (high reliability but high cost).
Domestic alternatives: such as Weichai, Yuchai, and Shangchai (with high cost-effectiveness, long-term stability needs to be verified).
4. Installation environment adaptation
• Space: Reserve 1.5 times the size of the unit for easy maintenance.
• Heat dissipation: Independent air intake and exhaust channels are required, with an ambient temperature of ≤ 40 ℃.
Noise reduction: Optional silent unit or customized soundproof room.
5. Parallel operation capability
When multiple units are connected in parallel, load balancing function is required.
The control system needs to support automatic synchronization and load distribution.
6. After sales service
Choose a supplier with a well-established localized service network.
Sign a maintenance agreement (including regular replacement of filter cartridges, engine oil, load testing, etc.).
Finally, based on personal design and operation experience, it may be necessary to remind users to consider future scalability and avoid investing in upgrades again in the short term. At the same time, suggestions for maintaining and monitoring the system are also important to ensure long-term stable operation. In addition, there are some precautions for work summary:
1. Fuel management
Diesel fuel needs to be regularly tested to avoid clogging the fuel supply system due to sediment.
Configure dual fuel tanks or automatic switching fuel supply system.
2. Testing and maintenance
Monthly no-load testing and quarterly load testing (≥ 30% load). An annual practical exercise simulating the interruption of the main power supply.
3. Collaborate with UPS
Ensure that the ATS switching time is less than the UPS battery life (usually 5-15 minutes).
Prevent generator harmonics from interfering with UPS input.