The Seven Types of Power Problems
White Paper 18 Summary Revision 1 By Joseph Seymour
Many of the mysteries of equipment failure, down-time, software and data corruption, are the result of a problematic supply of power. There is also a common problem with describing power problems in a standard way. This white paper describes the most common types of power disturbances, what can cause them, what they can do to your critical equipment, and how to safeguard your equipment, using the IEEE standards for describing power quality problems.
Our technological world has become deeply dependent upon the continuous availability of electrical power. In most countries, commercial power is made available via nationwide grids, interconnecting numerous generating stations to the loads. The grid must supply basic national needs of residential, lighting, heating, refrigeration, air conditioning, and transportation as well as critical supply to governmental, industrial, financial, commercial, medical and communications communities. Commercial power literally enables today’s modern world to function at its busy pace. Sophisticated technology has reached deeply into our homes and careers, and with the advent of e-commerce is continually changing the way we interact with the rest of the world.
Many power problems originate in the commercial power grid, which, with its thousands of miles of transmission lines, is subject to weather conditions such as hurricanes, lightning storms, snow, ice, and flooding along with equipment failure, traffic accidents and major switching operations. Also, power problems affecting today’s technological equipment are often generated locally within a facility from any number of situations, such as local construction, heavy startup loads, faulty distribution components, and even typical background electrical noise.
Widespread use of electronics in everything from home electronics to the control of massive and costly industrial processes has raised the awareness of power quality. Power quality, or more specifically, a power quality disturbance, is generally defined as any change in power (voltage, current, or frequency) that interferes with the normal operation of electrical equipment.
The study of power quality, and ways to control it, is a concern for electric utilities, large industrial companies, businesses, and even home users. The study has intensified as equipment has become increasingly sensitive to even minute changes in the power supply voltage, current, and frequency. Unfortunately, different terminology has been used to describe many of the existing power disturbances, which creates confusion and makes it more difficult to effectively discuss, study, and make changes to today’s power quality problems. The Institute of Electrical and Electronics Engineers (IEEE) has attempted to address this problem by developing a standard that includes definitions of power disturbances. The standard (IEEE Standard 1159-1995, "IEEE Recommended Practice for Monitoring Electrical Power Quality") describes many power quality problems, of which this paper will discuss the most common.
Seven Types of Power Problems Summarized
|Impulsive||Loss of data, possible damage, system halts||Lightning, ESD, switching impulses, utility fault clearing||TVSS, maintain humidity between 35 – 50%|
|Oscillatory||Loss of data, possible damage||Switching of inductive/capacitive loads||TVSS, UPS, reactors/ chokes, zero crossing switch|
|Interruption||Loss of data possible, damage shutdown||Switching, utility faults, circuit breaker tripping, component failures||UPS|
|3. Sag / undervoltage|
|Sag||System halts, loss of data, shutdown||Startup loads, faults||Power conditioner, UPS|
|Undervoltage||System halts, loss of data, shutdown||Utility faults, load changes||Power conditioner, UPS|
|4. Swell / overvoltage|
|Swell||Nuisance tripping, equipment damage/reduced life||Load changes, utility faults||Power conditioner, UPS, ferroresonant “control” transformers|
|Overvoltage||Equipment damage/reduced life||Load changes, utility faults||Power conditioner, UPS, ferroresonant “control” transformers|
|5. Waveform distortion|
|DC offset||Transformers heated, ground fault current, nuisance tripping||Faulty rectifiers, power supplies||Troubleshoot and replace defective equipment|
|Harmonics||Transformers heated, system halts||Electronic loads (non-linear loads)||Reconfigure distribution, install k-factor transformers, use PFC power supplies|
|Interharmonics||Light flicker, heating, communication interference||Control signals, faulty equipment, cycloconverters, frequency converters, induction motors, arcing devices||Power conditioner, filters, UPS|
|Notching||System halts, data loss||Variable speed drives, arc welders, light dimmers||Reconfigure distribution, relocate sensitive loads, install filters, UPS|
|Noise||System halts, data loss||Transmitters (radio), faulty equipment, ineffective grounding, proximity to EMI/RFI source||Remove transmitters, reconfigure grounding, moving away from EMI/RFI source, increase shielding filters, isolation transformer|
|Voltage fluctuations||System halts, data loss||Transmitters (radio), faulty equipment, ineffective grounding, proximity to EMI/RFI source||Reconfigure distribution, relocate sensitive loads, power conditioner, UPS|
|Power frequency variations||System halts, light flicker||Intermittent operation of load equipment||Reconfigure distribution, relocate sensitive loads, power conditioner, UPS|
For more information on this topic, please download White Paper 18, The Seven Types of Power Problems.