Power Quality Problem Identification and Mitigation
The impact of poor power quality is significant. According to Frost and Sullivan, power related problems cost U.S. companies more than $26 billion per year. There are a number of different factors that can cause electrical disturbances and one of the main factors can be the user. This includes wiring and grounding errors, load interactions, heavy load start-up, and poorly specified power conversion products. That being said, utility power isn’t perfect. Accidents can happen to power lines and power distribution equipment and bad weather can occur at any time.
Facility issues are a big factor, as well. Every facility/location is different. Disturbances can occur at varying magnitudes and rates. Noise, impulse, voltage and interruption are all varying issues. Resources such as a Power Quality Audit and Statistical Reports can be used to identify disturbances. Always be sure to match the protection to the needs to the load.
Another factor to keep in mind is load sensitivity. All loads are different; some may be sensitive to impulses, some may be sensitive to voltage sags, swells or brownout, and some may be sensitive to power interruption. Make sure to protect the loads that are most at risk.
Voltage sag is a temporary drop in RMS voltage and it may last for several cycles. It can be caused by large loads start-up, such as motors or air conditioning, and by utility switching. Some of the effects of voltage sag can be hardware crashes, occasional equipment failure and reduced efficiency and life span of electrical equipment. Solutions include a Power Conditioner, UPS and DC Power Supplies that meet SEMI F47.
A brownout is a temporary drop in RMS voltage that may last for several hours. A brownout can be caused by high demand on the utility grid or by service located at the end of the grid. The effects of a brownout are also hardware crashes, occasional equipment failure and reduced efficiency and life span of electrical equipment. A solution would be to use a Voltage Regulator.
A power interruption is sudden loss of AC power. Common causes of a power interruption are fuses or circuit breakers opening, bad weather, and construction accidents. The effects may include equipment shutting down, data loss, production delays, long process start up cycles and safety issues. A solution to a power interruption is a UPS.
Harmonic distortion is when distortion occurs to the sinewave. It can be caused by switch mode power supplies and by non-linear loads. The effects of harmonic distortion include high neutral current, overhead neutral, overheated transformers, voltage distortion, breaker tripping, and loss of system capacity. Solutions to this problem include Ferroresonant Transformers, Active/Passive filters, On-Line UPS, Drive Isolation Transformers, and K-Factor Transformers.
Voltage Transient is when a narrow, high voltage, or current impulse is superimposed on the AC waveform. It can be caused by utility grid switching, a contractor opening or closing, heavy industrial equipment starting and by lightning. The effects are equipment damage and/or failure, system lock-up, data corruption and/or loss and component stress that can lead to a breakdown. It can be taken care of with SPDs, an Isolation Transformer or with a Power Conditioner.
Last, but certainly not least, of all potential problems is electrical noise. Electrical noise is defined as low amplitude, low current, high frequency disturbances. It can be caused by switch mode power supplies, other loads and improper grounding and the effects of electrical noise could be perceived software errors and system lockup. Solutions include an Isolation Transformer, an Active Tracking Filter, a Power Conditioner and UPS.
Fluke offers many resources to help you identify and quantify energy disturbances and waste – both electrical and mechanical. These include power and energy loggers, thermal imagers and vibration testers. Visit Fluke’s website to learn more.
Now that we’ve discussed the potential problems, let’s review some of the solutions. Solutions include Surge Protective Devices, Signal/Data Line Protection (STC), Active Tracking Filters, Constant Voltage Transformers (Ferrorresonant), Drive Isolation and K-Factor Transformers and UPSs (Uninterruptible Power Supplies).
A Surge Protective Device is a device that clamps voltage to a safe level during an impulse. These devices solve problems with impulses and lightening. If the RMS voltage goes above the clamping level of the device, it will blow input fuses or destroy the device. A Signal/Data Line Protection (STC) is a device which clamps voltage to a safe level for data and communication lines and it also solves issues with impulses and lightening. It offers no protection from RMS voltage fluctuations.
An Active Tracking Filter is a device which filters high frequency noise (STF) and clamps voltage (STFE). This device solves issues with noise, impulse, and lightening and offers no protection from RMS voltage fluctuations. A Constant Voltage Transformer is a transformer with inherent voltage regulation due to design and it solves problems with impulses, noise, surges, sags, brownouts, and harmonics. A Constant Voltage Transformer will only ride through a -3ms power interruption.
Drive Isolation and K-Factor Transformers are transformers that are designed to handle high heat. They are also specifically designed for SCR controlled variable speed motor drives. They are able to handle mechanical stresses, voltage demands, and overheating caused by harmonics and they are typically K-4 rated. An Uninterruptible Power Supply (UPS) is a device which provides battery backup during a power interruption and also solves problems with impulses, harmonics, noise, surges, sags, and brownouts.
If you would like specifics on the solutions to solve power disturbances listed above, you can visit SolaHD’s website. SolaHD offers all of these power quality solutions.
There are a couple of different questions to ask when looking at the cost of power quality; such as how much the machinery or equipment is worth, how much the process is worth (a one second data loss, a 30 minute delay, a one hour shutdown, or a half-day work stoppage), and what the visibility of a production shutdown is to management. Lost performance, productivity, and data all leads to lost money.
The information was shared at our recent Product and Technology Expo in St. Louis. For a link to the PowerPoint presentation, click here.
Are you interested in learning more about these solutions to help mitigate your power quality issues? Contact your French Gerleman Account Manager or contact us.