Battery Systems for Mission Critical Infrastructure - Design, Maintenance and Testing (1)

 

Proper design, maintenance, and testing of battery system in mission critical facilities are crucial for business continuity and safety.

In these articles, we are going to

(1) Understand the need for reliable batteries in mission critical facilities;
(2) Explore the most common battery abnormalities that can be spotted through inspection; and
(3) Review simple steps that can be taken to find out battery problems.

When we say the systems are mission critical, it means "Power remains uninterrupted!". But this mission critical label does not apply to every single part of the facility. Some processes are more important to the business than others, and that is where the focus of the design lies. Certainly, designing for a mission critical facility can be challenging. There are many considerations in play. The system has to be very robust with no single point of failure.

Designing electrical systems, maintenance is an important factor, especially in deciding what battery to implement. Maintenance includes but not limits to the cost of replacement of a battery cell. It also involves the accessibility of the battery system, the ease of disassembly and reinstallation, the frequency of service, and the conditions needed in the actual environment (temperature, humidity, etc.).

The goal of maintenance is to prolong the life of batteries and to make sure the batteries perform as designed. Inspection is done to catch any abnormalities that could impact battery performance as well as long-term life expectancy. It is important to place the batteries in an environment that agrees with the manufacturer’s recommendations.


Battery Types


There are several types of batteries used for providing power to electrical systems. The most popular types of batteries being used nowadays are lead-acid and nickel-cadmium (NiCd). NFPA 110: Standard for Emergency and Standby Power Systems defines two types of lead-acid batteries:

Valve-regulated lead-acid (VRLA): A lead-acid battery consisting of sealed cells furnished with a valve that opens to vent the battery whenever the internal pressure of the battery exceeds the ambient pressure by a set amount.

A typical valve-regulated lead-acid (VRLA) battery used in an uninterruptible power supply (UPS) application

Vented (or flooded): A lead-acid battery consisting of cells that have electrodes immersed in liquid electrolyte. Flooded lead-acid batteries may have a provision for the user to add water to the cell and are equipped with a flame-arresting vent, which permits the escape of hydrogen and oxygen gas from the cell in a diffused manner such that a spark, or another ignition source, outside the cell will not ignite the gases inside the cell.

Although NFPA 110-2010 recognizes the usage of NiCd batteries for emergency systems, no definition is provided for such batteries. A definition can be found in IEEE 1106-2015: Recommended Practice for Installation, Maintenance, Testing, and Replacement of Vented Nickel-Cadmium Batteries for Stationary Applications (https://standards.ieee.org/findstds/standard/1106-2015.html).


Battery Uses


Mission critical facilities are not only the buildings that are critical to human life, such as hospitals, but also are facilities for business continuity, like data center. Many methods are employed to mitigate the risk of power outages. But, almost always, the risk mitigation relies upon batteries. Uses include:

Uninterruptible Power Supply (UPS) Systems: Batteries are used to back up power where UPSs are involved. While the power is processed and converted through the UPS to the load, the batteries are kept charged to provide the much-needed power to the critical system when normal power is out. Even though standby generators are most likely used as backup power, the batteries provide the critical power needed until the generators are able to receive load.

Standby Generators: Batteries are used to provide the initial crank to the generators as well as power the generator controls.

Controls: Batteries also are used to back up controls, especially when medium-voltage distribution is found throughout the facility. Nowadays, the operation of critical systems is more reliant on controls to avoid nuisance tripping and to enable fast-acting protection.

Emergency Systems: Batteries are widely used to back up life safety systems, such as exit lights. Exit lights normally are backed up by a 90-minute battery to allow people to recognize the way out of the building in case of a life-endangering situation. All of the above-mentioned uses (UPS, generators, and controls) could be part of an emergency system as well.



Next Article:
Battery Systems for Mission Critical Infrastructure - Design, Maintenance and Testing (2)



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SMA connects IT, Facilities and Design. For the other design considerations, please visit 

(1) Site Selection,
(2) Space Planning,
(3) Cooling,
(4) Redundancy,
(5) Fire Suppression,
(6) Meet Me Rooms,
(7) UPS Selection,
(8) Raised Floor,
(9) Code & Standards,
(10) Transformers and Harmonic Distortion,
(11) Multi-mode UPS Systems,
(12) Electrical Rooms,
(13) Generator Systems,
(14) Generator Fuel Systems, 
(15) Battery Systems, etc.

All topics focus on key components and provide technical advice and recommendations for designing a data center and critical facilities.

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