Nowadays, electronic devices are very sensitive to disturbances and are intolerant of power quality issues such as voltage sags, surges and harmonics. The International Electrotechnical Commission's term for voltage sag is voltage sag. Voltage sag is also defined as the unexpected reduction in voltage at a point in the electrical system, which is recovered after a short period of time ranging from half a cycle to a few seconds (as defined by IEC). Voltage sag is the decrease in the effective voltage level to 10% to 90% of the actual value, at power frequency for a period of half a cycle to one minute (according to IEEE 1159). Voltage rise is the increase in the effective voltage level to 110% - 180% of the actual value, at power frequency for a duration of half a cycle to one minute (according to IEEE 1159). This is a short-time voltage change phenomenon, which is one of the common power quality problems. The term "momentary surge" is another name for the term