Voltage fluctuations are changes or swings in the steady-state voltage above or below the designated input range for a piece of equipment. Fluctuations include both sags and swells.
Voltage fluctuation

Causes: Large equipment start-up or shutdown; sudden change in load; improper wiring; or grounding; utility protection devices

Vulnerable equipment: Computers; fax machines; variable frequency drives; CNC machines; extruders; motors

Effects: Data errors; memory loss; equipment shutdown; flickering lights; motors stalling/stopping; reduced motor life

Solutions: Verify proper electrical connections and wiring; relocate equipment; reduce voltage motor starters; uninterruptible power supply; voltage ride-through equipment.

Jack Johnson has given the answer in short. One thing I can suggest for you to protect your equipments especially refrigerators, where the compressors are likely to pack up very fast due to constant fluctuations and where replacement is going to cost you a fortune is - GO IN FOR A STABILISER WITH DELAY TIMER. This will protect your refrigerator and it has worked well for me in the last two years, as once I had to change the compressor due to constant fluctuations. The cost of stabiliser isn't very different from a normal one - around 1200 - 1500 depending on brand. I use a "whirlpool" one. And ask for a stabilser with a 5 MINUTE DELAY TIMER