26-04-2012, 03:30 PM
Power Quality full report
250\'s report.docx (Size: 751.88 KB / Downloads: 65)
INTRODUCTION
Power quality
Power quality is one of the most important topics that electrical engineers have been noticed in recent years. Electric power quality means different things to different people. To most electric power engineers, the term refers to a certain sufficiently high grade of electric service but beyond that there is no universal agreement. The measure of power quality depends upon the need of the equipment that is being supplied. What is good power quality for an electric motor may not be good enough for a personal computer. Usually the term power quality refers to maintaining a sinusoidal waveform of bus voltages at rated voltage and frequency. In its broadest sense, power quality is a set of boundaries that allows electrical systems to function in their intended manner without significant loss of performance or life.
Cost of poor Power Quality
Poor Power Quality can be described as any event related to the electrical network that ultimately results in a financial loss. Possible consequences of poor Power Quality include
Unexpected power supply failures (breakers tripping, fuses blowing)
Equipment failure or malfunctioning
Equipment overheating (transformers, motors) leading to their lifetime reduction.
Damage to sensitive equipment (PC‟s, production line control systems)
Electronic communication interferences
Increase of system losses
Need to oversize installations to cope with additional electrical stress with consequential increase of installation and running costs and associated higher carbon footprint.
Sag
A "dip" (in British English) or a "sag" (in American English - the two terms are equivalent) is the opposite situation where the RMS voltage is below the nominal voltage by 10 to 90% for 0.5 cycle to 1 minute. The main causes for sag are faults on the transmission and distribution network mostly on parallel feeders, faults in consumer’s installation, connection of heavy loads and startup of motors. This leads to malfunction of microprocessor-based control systems (PCs, PLCs, ASDs, etc.) that may lead to process stoppage, tripping of contactors and electromechanical relays, disconnection and loss of efficiency in electric rotating machines.
Swell
It occurs when the RMS voltage exceeds the nominal voltage by 10 to 80% for 0.5 cycle to 1 minute. This voltage swell may be caused by switching of heavy loads, badly dimensioned power sources, badly regulated transformers mainly during off-peak hours. The various consequences of voltage swell are data loss, flickering of lighting and screens and stoppage or damage of sensitive equipment.
Surge
It is a rapid short-term increase in voltage. Surges often are caused when high power demand devices such as air conditioners turn off and the extra voltage is dissipated trough the power line. Surges are also caused by over-voltages resulting from lightning,switching on the utility power system and other causes without forewarning. Surges normally can be filtered out of the power system at the customer level.
Spike
An extremely high and nearly instantaneous increase in voltage with a very short duration measured in microseconds. Spikes are often caused by lightning or by events such as power coming back on after an outage. A spike can damage or destroy sensitive electronic equipment and of insulating materials, data processing errors or data loss and electromagnetic interference. Turn the equipment off during a power outage. Wait a few minutes after power is restored before turning it on, then turn on one device at a time.
Noise
Noise is a disturbance in the smooth flow of electricity. Often technically referred to as electro-magnetic interference (EMI) or radio frequency interference (RFI). “Harmonics” are a special category of power line noise that causes distortions in electrical voltage. Noise can be caused by motors and electronic devices in the immediate vicinity or far away. Noise can affect performance of some equipment and introduce glitches and errors into software programs and data files.
Outage
Total loss of power for some period of time. Outages are caused by excessive demands on the power system, lightning strikes and accidental damage to power lines. In addition to shutting down all types of electrical equipment, outages cause unexpected data loss.
250\'s report.docx (Size: 751.88 KB / Downloads: 65)
INTRODUCTION
Power quality
Power quality is one of the most important topics that electrical engineers have been noticed in recent years. Electric power quality means different things to different people. To most electric power engineers, the term refers to a certain sufficiently high grade of electric service but beyond that there is no universal agreement. The measure of power quality depends upon the need of the equipment that is being supplied. What is good power quality for an electric motor may not be good enough for a personal computer. Usually the term power quality refers to maintaining a sinusoidal waveform of bus voltages at rated voltage and frequency. In its broadest sense, power quality is a set of boundaries that allows electrical systems to function in their intended manner without significant loss of performance or life.
Cost of poor Power Quality
Poor Power Quality can be described as any event related to the electrical network that ultimately results in a financial loss. Possible consequences of poor Power Quality include
Unexpected power supply failures (breakers tripping, fuses blowing)
Equipment failure or malfunctioning
Equipment overheating (transformers, motors) leading to their lifetime reduction.
Damage to sensitive equipment (PC‟s, production line control systems)
Electronic communication interferences
Increase of system losses
Need to oversize installations to cope with additional electrical stress with consequential increase of installation and running costs and associated higher carbon footprint.
Sag
A "dip" (in British English) or a "sag" (in American English - the two terms are equivalent) is the opposite situation where the RMS voltage is below the nominal voltage by 10 to 90% for 0.5 cycle to 1 minute. The main causes for sag are faults on the transmission and distribution network mostly on parallel feeders, faults in consumer’s installation, connection of heavy loads and startup of motors. This leads to malfunction of microprocessor-based control systems (PCs, PLCs, ASDs, etc.) that may lead to process stoppage, tripping of contactors and electromechanical relays, disconnection and loss of efficiency in electric rotating machines.
Swell
It occurs when the RMS voltage exceeds the nominal voltage by 10 to 80% for 0.5 cycle to 1 minute. This voltage swell may be caused by switching of heavy loads, badly dimensioned power sources, badly regulated transformers mainly during off-peak hours. The various consequences of voltage swell are data loss, flickering of lighting and screens and stoppage or damage of sensitive equipment.
Surge
It is a rapid short-term increase in voltage. Surges often are caused when high power demand devices such as air conditioners turn off and the extra voltage is dissipated trough the power line. Surges are also caused by over-voltages resulting from lightning,switching on the utility power system and other causes without forewarning. Surges normally can be filtered out of the power system at the customer level.
Spike
An extremely high and nearly instantaneous increase in voltage with a very short duration measured in microseconds. Spikes are often caused by lightning or by events such as power coming back on after an outage. A spike can damage or destroy sensitive electronic equipment and of insulating materials, data processing errors or data loss and electromagnetic interference. Turn the equipment off during a power outage. Wait a few minutes after power is restored before turning it on, then turn on one device at a time.
Noise
Noise is a disturbance in the smooth flow of electricity. Often technically referred to as electro-magnetic interference (EMI) or radio frequency interference (RFI). “Harmonics” are a special category of power line noise that causes distortions in electrical voltage. Noise can be caused by motors and electronic devices in the immediate vicinity or far away. Noise can affect performance of some equipment and introduce glitches and errors into software programs and data files.
Outage
Total loss of power for some period of time. Outages are caused by excessive demands on the power system, lightning strikes and accidental damage to power lines. In addition to shutting down all types of electrical equipment, outages cause unexpected data loss.