Here are some examples of problems that may be associated with harmonics.The total harmonic distortion value is often applied in terms of power quality validity to the voltage.Total harmonic distortion is the sum of all harmonic effects; (.Possible sources of flickering lights include machines with rapid fluctuations in load current or voltage, machines with rotary transformers such as mill motors and mine coils, and machines that use fixed frequency converters such as AC motors and electric  Overheated transformers and tripped circuit breakers, Dips  swells - voltage lower or higher than expected
frequency effects caused either by the power supply or by equipment operating within the system
Unbalance - the effect of voltage or current variations on each of the electrical phases
may be signs of harmonic problems, with harmonic currents flowing back to other parts of the power system.-The state of harmonics in a system can be expressed in several ways.Flickering lights are a common symptom of a power quality problem.