There was a time when achieving an uninterrupted flow of power was good enough. However, with the proliferation of contemporary electronic technologies has come the need for more precise control of electrical power as well.
Parameters such as frequency, voltage quality (interruptions, variations, unbalances, flicker, sags, and swells) and harmonics are key factors determining power quality. In a three-phase power system, any disturbance on one parameter (magnitude, frequency, waveform, or symmetry) is classified as a power quality problem.
Power Quality Defined
In a nutshell, good power quality is said to be comprised of a stable supply of voltage staying within a prescribed range, accompanied by a steady alternating current frequency as close as possible to the rated value. This will register as a smooth voltage curve waveform, resembling that of a sine wave when it’s viewed on a scope.
Less than optimal power quality can trigger performance degradation and reduced life expectancy of equipment. Generally speaking, any condition related to voltage, current, or frequency deviations — that result in failure, increased energy loss or malfunctioning of equipment — could be attributed to poor power quality. However, a lack of electromagnetic compatibility and the presence of noise can degrade power quality too. Fortunately, there are a wide variety of power quality devices to help you ensure your facility gets the absolute best it can.
Power Quality Factors
The parameters affecting power quality typically fall into one of two categories: steady state and disturbances. Steady state elements include harmonics, frequency deviation, voltage unbalance, voltage fluctuations and flicker.
Meanwhile, characteristics classified as disturbances include outages, momentary interruptions, surges, voltage dips and voltage swell. The disturbances are pretty self-explanatory; so, let’s delve a bit more deeply into voltage issues.
The power standard in the U.S. is 120V and 60HZ AC. Faults in the transmission system, load disconnections or generation sources going offline can affect frequency. This parameter is critical to the long-term functioning of equipment and can cause grid blackouts in extreme cases.
The goal in this area is to minimize interruptions, fluctuations, unbalance, sag, swell, transients and harmonics. In other words, you want the flow of voltage to be as smooth and uninterrupted as possible. Voltage-related issues can cause erratic operation of systems, as well as degradation of insulation. Contacting surfaces of switches, isolators and circuit breakers can be impacted negatively as well. High-voltage transients can trip circuit breakers and saturate transformers.
Also sometimes referred to as waveform, harmonics tend to be introduced during the transmission of power from the generating station to the end user. Harmonic usually creeps in as power flows through utility lines because of the current characteristics of non-linear loads reflecting on network impedance’s. Harmonics can cause vibrations, buzzing, equipment distortions, losses and overheating in transformers.
This one can actually be visible to the naked eye when voltage fluctuations affect the output of a lamp. In more technical terms, it happens when there is a change in voltage over nominal, which can be expressed as a percent. Fast switching operations of various industrial processes or electrical appliances connected to the supply system can induce this issue. These rapid voltage fluctuations can contribute to fatigue among workers in industrial settings. It can also have an adverse effect on the ability of people to focus their attention.
Consequences of Poor-Quality Power
Deficiencies in the factors determining power quality will increase your utility and operating costs. Even minor disruptive voltage fluctuations can cause major issues from equipment malfunctions to flickering lights to complete power shutdowns. Power quality problems can also cause outages and equipment failures.