Maintenance of Switchgear and Backup Power Systems

By James Piper, P.E.  
OTHER PARTS OF THIS ARTICLEPt. 1: Backup Generators, UPS Systems Provide Power in an OutagePt. 2: This Page

The electrical switchgear that connects the backup generator or the UPS system to the facility's loads forms the backbone of the power system. With the UPS system, the loads are connected to distribution panels that are wired to the output of the system. Loads in generator-based systems are connected to distribution panels that are wired to an automatic transfer switch. Utility power is normally connected to the loads through the transfer switch. When utility power is interrupted and the generator is producing power, the switch automatically transfers the load to the output of the generator. When utility power is restored, the switch automatically transfers the load back to the utility.

Electrical switchgear typically is a long-life, low-maintenance item. Because it is reliable and does not require much maintenance, it is the most overlooked component in the system. A malfunction in the switchgear, however, can prevent an otherwise perfectly operating system from coming online. Additionally, malfunctions within the switchgear can result in damage to the switchgear itself.

Most damage to electrical switchgear is caused by a combination of water, dust, high humidity levels and vibration. Moisture and dust combine to form an insulating layer on surfaces, reducing heat transfer from the components and increasing component operating temperatures. Similarly, moisture and dust coat components, restricting their movement and causing excessive wear. Vibrations can cause terminations to come loose.

At least once each year, all switches, disconnects, and circuit breakers should be exercised to verify that they are not binding. At the same time, all contacts and connections within the system should be inspected for pitting, discoloration and tightness.

Avoiding Common Pitfalls

Backup power systems are very reliable, and good maintenance practices can keep them that way for a long time. And while the systems may be fully automatic, they do require some careful planning during installation and once the systems become operational.

For example, during a prolonged power outage, it will be necessary to arrange for fuel deliveries for propane gas and diesel generators. Contracts with suppliers should be set up ahead of time with guaranteed delivery schedules. If a facility manager waits until the generator is already running to figure out how fuel is going to be supplied to the unit, maintenance personnel may be forced to shuttle fuel in five gallon cans, a practice that is unsafe and unreliable.

Care must be taken when planning the location of a backup power system. Generators are noisy units that create vibrations and give off exhaust fumes. Units must be located in such a way that they do not interfere with operations, yet are fairly close to the facility's power distribution panels so that they can be tied in relatively easily.

UPS systems also must be carefully sited. These systems and their batteries generate large quantities of heat under normal operation. Without adequate ventilation, a buildup of heat will shorten the lives of the batteries and other components. Good ventilation is also required to prevent a buildup of hydrogen gas, which is a normal byproduct of the battery charging process.

In addition, it's important to make certain that all required loads are properly connected to the system. Over time, power requirements within the facility change. New loads are added while old ones are removed or relocated. At least once each year, the facility should be reviewed for backup power requirements. Failing to do so may result in a perfectly operating backup power system that is not connected to the required loads.

Power outages can occur at any time. As a result, personnel who are most familiar with how to operate and monitor the backup power system may not be on-site at the time of the outage. Therefore it is essential to have well written procedures detailing what should be done in the event of an outage. These procedures must cover everything from what to do if the system does not start to how to monitor the health of the system while it is operating.

James Piper, PhD, PE, is a writer and consultant who has more than 35 years of experience in facilities management. He is a contributing editor for Building Operating Management.

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  posted on 6/29/2010   Article Use Policy

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