The main cause of overvoltage in power systems is due to several factors: lightning impulses and switching impulses of the system, insulation failure, arcing ground, and resonance. Overvoltages caused by lightning is very high. Overvoltage can be caused by poor regulation of a power source from a utility company, oversized transformers, uneven or varying circuit loading, wiring errors, and electrical insulation or isolation failures.
Overvoltages can cause premature failure of electrical and electronic components due to overheating. As the voltage level goes up, the current is reduced and lower current usually equates to less heat generation within the motor windings. The overvoltage can cause excessive current to flow as well as creating excessive voltage stresses.
Overvoltages can be the result of long-term problems that create swells. An overvoltage can be thought of as an extended swell. Overvoltages are also common in areas where supply transformer tap settings are set incorrectly and loads have been reduced. This is common in community regions where seasonal power usage is reduced during the off-season, but the output settings for the high-usage portion of the season is still being supplied, even though the power need is much smaller. It's much like putting your thumb over the end of a garden hose. The pressure increases because the hole where the water comes out has been made smaller, even though the amount of water coming out of the hose remains the same.
Overvoltage conditions can create a high current draw and cause the unnecessary tripping of downstream circuit breakers as well as overheating and putting stress on equipment.
Since an overvoltage is really just a constant swell, the same UPS or conditioning equipment that works for swells will work for overvoltages. However, if the incoming power is constantly in an overvoltage condition, then the utility power to your facility may need correction as well. The same symptoms for swells also apply to overvoltages. Since overvoltages can be more constant, excess heat may be an outward indication of an overvoltage. Equipment (under normal environmental conditions and usage), which normally produces a certain amount of heat, may suddenly increase in heat output because of the stress caused by an overvoltage.