Power Reliability
Part 1: Backup Generators, UPS Systems Provide Power in an Outage
Part 2: Maintenance of Switchgear and Backup Power Systems
Maintenance of Switchgear and Backup Power Systems
By James Piper, P.E. - July 2010
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.
Comments
DonCastagnola wrote re: Maintenance of Switchgear and Backup Power Systems
on 8/1/2010 11:01:10 AM
We have a double electrical distribution system feeding redundant A/B UPS systems. It was expensive, but it has proved invaluable to our operations.
We are under the juristiction of the South Coast Air Quality Management District here in LA. We have been using red dye low sulfur diesel for years. We have a vendor that checks the fuel for contamination once a year. We ususally polish 2/3 of our fuel annually, depending of severity of contamination.
JustAJanitor wrote re: Maintenance of Switchgear and Backup Power Systems
on 8/1/2010 9:55:02 AM
We test our critical load backup systems weekly and have the diesel fuel tested at least twice per year. We use only premium blend off-road fuel. Each system is serviced twice per year.
What's going to be interesting is that if the emission requirements for diesel generators change to the requirements recently implemented for diesel trucks. This could have a substantial financial impact on health care institutions or public entities where generators are decades old. Maybe they will be exempted because they are almost always used for standby duty only. Stay tuned..
On the subject of double electrical distribution systems, it would be nice to have such a network, but I can't imagine trying to justify, or paying for the extra expense to install and maintain such a system.
pktsam2000 wrote re: Maintenance of Switchgear and Backup Power Systems
on 8/1/2010 5:44:07 AM
When we speak about 'power reliability', it is not only the multiple power sources but also multiple power distribution systems that can guarantee reliability. It is of no use if one has multiple power sources (city power, generator power, UPS) but has only one power distribution circuit & single set of switch gear. For critical applications, the load should receive two independent power supply lines, each laid in a different route to increase reliability. Single distribution circuit also means 'shut-down' for maintenance & trouble-shooting. For example, in a hospital, one cannot afford to shut-down power for the purpose of maintenance of switch gear & distribution cables or bus bars. 'Dual path' power distribution is the solution with redundance distribution components (such as double bus bars)
Fuelman wrote re: Maintenance of Switchgear and Backup Power Systems
on 6/30/2010 2:41:55 PM
I work for a fuel lab and I can tell you first hand that it cost far less to get your fuel tested then it does to deal with the problem after failure.
WendyFOPCO wrote re: Maintenance of Switchgear and Backup Power Systems
on 6/29/2010 4:08:07 PM
In addition to having a procedure for refueling the generators, many times the fuel that is existing in the tank as well as the new fuel being added, is contaminated. If the fuel tanks are not properly maintained, the back up system may fail. The build up of contaminates in fuel and fuel storage tanks can quickly clog filters and fuel injectors resulting in the engine shut down. In an emergency situation this is the worst that can happen. Contaminated fuel can cause thousands of dollars in damage to the generator. It is suggested that you have each tank tested for contaminates. If water, microbial growth, particulate matter, fungus, algea or other fuel breakdown products (sludge) are found, it is important to have your fuel supply polished and treated with enzymes added to kill the bacteria. If the fuel is extremely contaminated (unusable), new tanks, filters, fuel injectors may need to be replaced. A fuel injector cost alone is in the range of $7,500. On top of that, to have the contaminated fuel disposed of properly and a new fuel supply added is an exorbitant cost. It is extremely cost effective and good maintenance protocol to have your fuel tested quarterly for hospitals and every six months for other entities. If the fuel test comes back positive for contaminants, have the fuel polished and treated. Maintaining the fuel properly will also lower the emmissions to meet the clean air standards. In the case with a hospital, the loss of power can be catastrophic. This situation actually happened recently at an Orange County Calfornia hospital. The generator failed and the doctors were manually pumping air into patients on venilators. The generators failed due to heavy contaminates in the fuel. Not a good outcome for this hospital. So as you can see, fuel and fuel tank maintenance is extremely important and should be taken very seriously.
