Dips and interrupts can occur on the AC power mains as a result of a fault in the distribution system such as an open circuit breaker or a sudden large load being turned on in the immediate vicinity. A power distribution system fault can cause a switch in the distribution grid to open and close a number of times, resulting in multiple interrupts to electrical and electronic equipment. Dips occur at any level ranging from only a slight reduction in nominal to a total loss of voltage. A total loss of voltage is referred to as an interrupt. These events are expressed in terms of a percentage deviation from nominal voltage and with a duration period expressed either in time or periods. Dips / interrupts are completely random in nature and generally only occur as single events.

All electronic products should be tested for immunity to dips and interrupts to insure their continued reliable operation if subjected to dips and/or interrupts on the AC power mains. The European Union’s EMC Directive mandates dips and interrupts testing for virtually all electrical and electronic products as a condition for obtaining the CE Mark before shipping products to member states of the European Union.