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Power Quality Problems
Power Quality is Important
The symptoms of a power quality problem could be as subtle as a light that dims every time a large motor starts or as catastrophic as equipment failure. Whatever the case, power quality problems may disrupt your business operations. Today, there is widespread use of digital or microprocessor controlled devices in all areas of our customer's businesses.
Many of these new devices are more sensitive and may not operate properly when small variations or disruptions in the electrical supply occurs. Some examples of problems that occur due to power quality problems are: Automatic Resets, Data Errors, Equipment Failure, Circuit Board Failure, Memory Loss, Power Supply Problems, UPS Alarms, Software Corruption, and Overheating of electrical distribution systems.
Common Power Quality Problems
To function properly, electronic devices require voltage to flow within a consistent range. Power surges, sags, transients, and momentary interruptions can cause voltage to fluctuate outside this range. Power quality problems can be caused by external events, such as lightning strikes can impact power quality but causes can also include starting and stopping of heavy equipment, circuit overloads, or improper wiring. Some loads that cycle on or off can cause surges that can gradually degrade internal circuitry of sensitive electronic equipment.
The electric power that is generated in the United States is in the form of a 60-hertz (Hz) alternating current (AC) sine wave. A pictorial representation in time of a sine wave is shown below.
A power quality problem is manifested by the interruption or distortion of the ideal 60-hertz sine wave. These power quality problems can be grouped into the following categories:
- Temporary Interruption
- Long-Term Outage
- Momentary Interruption
- Sag or Undervoltage
- Swell or Overvoltage
- Transient, Impulse, or Spike
- Harmonic Distortion
Power Quality Investigation
The main objective of the investigation is to properly identify the power quality problem so that the proper solution can be applied. This investigation should be done prior to any major electrical changes or purchase of power conditioning equipment.
A typical power quality investigation is conducted in the following sequence:
- Review of Electrical Disturbance Logs
- Review of the Facility's Single Line Electrical Diagram
- Site Survey by Hawaii Electric Light
- Review of Equipment documentation (example: specifications, equipment manuals, operating procedures)
- Installation of Power Quality Monitoring Instruments
- Analysis of Power Quality Data