4  FM quick reads on backup power

1. Reliable Power Must Be Maintained In Critical Systems


The failure of a backup power system in an institutional or commercial facility could cause the loss of productivity, revenue and even human life. As a result of these high stakes, maintenance and engineering managers must ensure they provide a reliable flow of power to support critical systems and equipment, especially in emergencies.

In many facilities, a standby generator system supports crucial life-safety systems, such as egress lighting and fire alarm, that enable occupants to safely evacuate a building. In health care facilities, these systems also support essential life-support and other equipment.

In facilities with critical computer and technology loads, uninterruptible power supplies (UPS) are part of the standby power-distribution system. These systems include auxiliary equipment, such as transfer switches and fuel tanks.

But even modern facilities that are designed according to codes to provide backup power systems with appropriate levels of redundancy will have a high probability of failure if technicians do not properly test and maintain these essential systems.

It is important that technicians address all system components both individually and as a system. Standby power systems typically contain cooling, fuel, battery/charging, engine, and distribution subsystems, which all have their own unique testing and maintenance requirements.

Among the most common causes of failure in generator and UPS distribution systems are these:

  • Incomplete system commissioning that fails to identify installation or control-logic errors
  • Equipment not returned to proper operational state after testing, maintenance or alarms
  • Generator failure to start, due to old, discharged or poorly maintained batteries
  • Battery charger breaker turned off
  • Low fluid levels or fluid leaks
  • Exhaust system failure due to wet stacking, or running generators under low load that causes the accumulation of carbon particles, unburned fuel, oil and condensed water in the exhaust system
  • Insufficient reserve of fuel or deteriorating fuel quality
  • Operational failure of ventilation louvers.


2.  The Importance of UPS Maintenance

Even modern facilities that are designed according to codes to provide backup power systems with appropriate levels of redundancy will have a high probability of failure if technicians do not properly test and maintain these essential systems.

The failure of a backup power system in an institutional or commercial facility could cause the loss of productivity, revenue and even human life. As a result of these high stakes, maintenance and engineering managers must ensure they provide a reliable flow of power to support critical systems and equipment, especially in emergencies.

In many facilities, a standby generator system supports crucial life-safety systems, such as egress lighting and fire alarm, that enable occupants to safely evacuate a building. In health care facilities, these systems also support essential life-support and other equipment.

In facilities with critical computer and technology loads, uninterruptible power supplies (UPS) are part of the standby power-distribution system. These systems include auxiliary equipment, such as transfer switches and fuel tanks.

Prior to the testing and maintenance of backup power systems, technicians need to investigate potential locations and environmental causes of failure. Is key equipment located below flood level? Is it located below seismically unsafe objects or in an area with insufficient air flow? Assuming the system's designers and installers resolved any location and environmental issues prior to installation, managers can focus on testing and maintenance.

Just as a chain is only as strong as its weakest link, a standby power-distribution system is only as strong as its weakest link. A 5 megawatt (mW) generator distribution system can fail because of an incorrect fuse, a loose wire connection, or a lack of fuel.

It is important that technicians address all system components both individually and as a system. Standby power systems typically contain cooling, fuel, battery/charging, engine, and distribution subsystems, which all have their own unique testing and maintenance requirements.

3.  UPS Offers Protection Against Common Power System Faults

Generators can offer facilities and their operations long-term protection in the event of an interruption of service, but they cannot offer protection against many common faults in power systems. Facilities can achieve that level of protection only with an uninterruptible power supply (UPS). While there are several different configurations for UPS, online systems are the most common. An online UPS has three components: a charger/rectifier, storage batteries, and a power inverter. Incoming alternating current from the utility enters the charger/rectifier, which converts it to direct current. This direct current charges the batteries and supplies power to the inverter, which converts the direct current back to alternating current. In systems that provide power for loads in the event of extended outages, a generator typically is connected to the batteries.

The UPS offers the advantage of supplying power to the loads continuously, no matter what happens to the utility power. But the benefits of a UPS go beyond the ability to continuously supply power. The process of taking alternating current from the utility and converting it to direct current and back to alternating current also eliminates most power disturbances, including noise, transients, and voltage fluctuations.

Managers specifying a UPS to protect facilities and systems need to be certain it is sized properly for the load it is designated to protect. They at least must be sure to size the UPS so it can provide 150-200 percent of the connected load. This spare capacity protects the UPS from additional power loads while the equipment is starting, and it allows room for growth.

Managers also need to properly size the batteries in the UPS to provide the desired runtime in the event of a power loss. For some applications, the UPS only needs to provide power long enough to allow an orderly shutdown of connected equipment.

4.  Guidelines for Choosing a UPS

This is Chris Matt, Managing Editor of Print & E-Media, with Maintenance Solutions magazine. Today's tip is determining the right UPS solution.

A facility's uninterruptible power supply, or UPS, should be able to protect critical and high-tech equipment in an outage and facilitate planned power outages so technicians can conduct routine maintenance. Here are some considerations that can help system designers and managers determine the right UPS solution:

• Facility-distribution type. The two configurations of UPS distribution systems are centralized and distributed.

In a centralized configuration, the units are in a common location for more efficient maintenance, security, cooling and, in many cases, fire rating of the room. A distributed configuration puts the units closer to the loads they protect, minimizing potential failure points but increasing construction costs because many of the items listed above are repeated throughout the facility.

• Duration. An organization's business model determines the length of time a UPS must provide power. Does the application call for a quick-ride-through UPS, or does it require 15 minutes of backup capacity to systematically shut down sensitive electronics in the event of a longer power outage?

• Reliability. Determining an organization's reliability needs is essential for providing value to occupants. Some organizations can tolerate short periods of downtime, while others definitely cannot. A preventive maintenance program also plays a critical role in reliability over the system's life.

• Flexibility. If the UPS system does not have the flexibility to bypass equipment for maintenance purposes, the facility still will need to provide downtime to maintain or repair the system, even if designers and managers implement a highly reliable system.


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