Aside from being one of the common power problems, transients are also the most damaging. Transients are basically sudden changes in voltage or current. The main causes of transients are lightning strikes, inadequate grounding and switching of devices, among others. These events can cause computers to lose data and equipment to fail. Transients are divided into two subcategories, impulsive transients and oscillatory transients.
Impulsive transients are sudden and excessive increases in power that can cause voltage or current to go up or down. These kinds of transients are also called power spikes, bumps and glitches. While the main cause of an impulsive transient is a lightning strike, it is not necessary for lightning to strike the equipment since the electro-magnetic field surrounding lightning is enough to affect structures that can conduct electricity. One way to protect against an impulsive transient is to use a device that can control voltage or surge protection devices. Another way to protect against impulsive transients is to control the temperature and moisture of the room where the data center is located.
On the other hand, oscillatory transients happen when the polarity of voltage or current goes up and down at a rapid rate. In other words, it goes from negative to positive and back at a fast pace. An oscillatory transient happens when machines, like a motor, is suddenly turned off. This situation is similar to rapidly shutting off a faucet where a hammering noise can be heard coming from the pipes. The hammering noise comes as the water flowing through the pipes resist this sudden change.
Uninterruptible power supply devices include surge protection and so can be used to reduce the effect of impulsive and oscillatory transients. But, these devices may not be able to prevent them from happening, especially when they happen in a shop using heavy machinery.