Power disturbance and power quality-light flicker voltage requirements

Operation of loads that produce power disturbances can interfere with successful operation of other loads connected to the electric power distribution network. Understanding the nature of power system disturbances is important in the proper diagnosis and remediation of problems. Light flicker resulting from frequently recurring, low amplitude voltage fluctuations is one of several well-known power quality problems. Voltage requirements to avoid objectionable light flicker is currently in need of a thorough technical review. Other related power quality problems are distinguished by a peculiar type of voltage fluctuation or power disturbance sometimes referred to as phase jitter or phase jump both of which are forms of phase modulation. Almost nothing has been published in the open literature about phase modulation or its effect on power systems. Although rare, symptoms of excessive phase modulation are not recognised when they do occur. Phase jitter problems are frequently identified as power disturbances of unknown origin. Instrumentation to measure phase modulation is not commercially available. Manifestations of excessive phase modulation include degraded electronic drive performance and interference with electronic UPS systems