Ideal Power Quality Meters

Poor power quality can be extremely expensive since it increases energy costs. That may include excess power usage as well as being penalized for increasing poor power factor or higher peak demand utility charges that might not be necessary. Poor power quality takes its toll on equipment. This will increase the cost of maintenance and repairs. Replacement of premature failures of equipment as well as the cost of the diagnosis and replacement of this equipment can be extremely costly.
 
Although every user has a primary purpose in mind when checking and evaluating Power and Power Quality, the most common purpose is the measurement of how reliably and efficiently your systems operates under load. We usually begin by evaluating our system's response and use of electricity, but in utilizing power instrumentation, we may need to evaluate many parameters, including, but not limited to:          

• Transients
• Voltage, Current and Frequency Disturbances
• System Dips, Sags, Swells
• Harmonic Distortion
• Unbalances
• Flicker

System problems are evaluated based on measuring the source and direction of the impending problem as well always measuring magnitude and direction. The timing of the problem is always important, whether one microsecond or one hour in length
 
Normal system analysis usually involves the measurement of voltage and frequency deviations. Most instrumentation will detail the range of measured values and the safety category capability of the instrumentation. Please use the link below to see the most recent advance in NFPA 70E.
Who sets the rules for electrical testing and safety?

Considerations when selecting a Power Quality Analyzer

• Sampling rate and data storage rate
• Accuracy
• Bandwidth
• # of channels
• Are transducers included or purchased separately?
• Triggering algorithms and analysis techniques
• Memory
• Communications
• Ease of use
• Battery life

Harmonics Definitions and Measurements
 
Most concerns for any Power quality system evaluation will include the measurement of Harmonics. Harmonic Analysis involves the real time existence of waveform distortions. As a definition, harmonic frequencies are odd end even multiples of the 60Hz (hertz) first fundamental frequency. The second harmonic is at 120Hz, (twice the fundamental); the third harmonic is at 180Hz and so-on. When all the frequencies are summed, the result is the measured waveform. Any deviation from a pure sinusoidal (sine) waveform indicates the existence of harmonic components. Harmonics may exist in any short or long time sequence, but harmonics only cause damage when they exist for a significant amount of time. This is because harmonics generate excessive heat.

Although Current and Voltage Harmonics exist and both may be detrimental to the system, current harmonics tend to be less severe as they extend from their point of origin; however, Voltage harmonics have a tendency spread and can damaging at a greater distance from their origins.
 
Harmonic Distortion
 
Once the source of the harmonic distortion is found, the process of determining how to prevent it and control it may begin. Following is a listing of common sources of harmonics typically listed as Non-Linear Loads i.e.,          

• Personal computers and other microprocessor-based devices
• Uninterruptible Power Supplies (UPS)
• Fluorescent lighting (especially newer electronic ballast types)
• Battery chargers
• Static power converters
• AC heating controls
• AC and DC motor controllers
• Rectifiers
• Power supplies used in electronic and office equipment
• Power electronics such as Variable Speed Drives
• SCR-controllers
• AC/DC static converters
• Arc furnaces
• Welders
• Saturated Transformers
• Intermittent electrical noise from loose connections

What are Triplen Harmonics?

One of the most troublesome harmonics usually is the third harmonic and its odd multiples of the third. This is referred to as the Triplen Harmonics (3^rd, 9^th, 15^th, 21^st, etc.). These harmonics seems to be the most dominant and always have the highest magnitude and cause the most damage since the currents are additive on the neutral. The fifth (5^th) and eleventh (11^th) harmonics are also cause for concern since they will attempt to drive a 3-phase motor in the opposite direction and will possibly cause nuisance tripping and overheating.
 
It is important to establish the system evaluation; the harmonics that may be prevalent, any transients, sags or swells and then attempt to find a mitigation approach to reduce problem areas.
 
Sometimes it is not evident until testing is done and measurements are made that small equipment added in a system over time may be the very culprit in producing damaging harmonics.
     

Power Quality vs. Power Demand from TEquipment.net

Power Quality Measurement World Standards