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Cisco Wide Area Virtualization Engine 594 and 694 Hardware Installation Guide
OL-24619-02
Appendix B Maintaining the WAVE-594 and WAVE-694
Using Power Protection Devices
Surge Protectors
Surge protectors are available in a variety of types and usually provide a level of protection
commensurate with the cost of the device. Surge protectors prevent voltage spikes, such as those caused
during an electrical storm, from entering a system through the electrical outlet. Surge protectors,
however, do not offer protection against brownouts, which occur when the voltage drops more than
20 percent below the normal AC line voltage level.
Line Conditioners
Line conditioners go beyond the overvoltage protection of surge protectors. Line conditioners keep a
system’s AC power source voltage at a fairly constant level and therefore can handle brownouts. Because
of this added protection, line conditioners cost more than surge protectors—up to several hundred
dollars. However, these devices cannot protect against a complete loss of power.
Uninterruptible Power Supplies
Uninterruptible power supply (UPS) systems offer the most complete protection against variations in
power because they use battery power to keep the system running when AC power is lost. The battery is
charged by the AC power while it is available, so once AC power is lost, the battery can provide power
to the system for a limited amount of time—from 15 minutes to an hour or so—depending on the UPS
system.
UPS systems range in price from a few hundred dollars to several thousand dollars, with the more
expensive units allowing you to run larger systems for a longer period of time when AC power is lost.
UPS systems that provide only 5 minutes of battery power let you conduct an orderly shutdown of the
system but are not intended to provide continued operation. Surge protectors should be used with all UPS
systems, and the UPS system should be Underwriters Laboratories (UL) safety-approved.