Technical Article

Understanding Power Quality, Monitoring, and Correction  

January 31, 2023 by Damond Goodwin

Power quality is an increasing concern for manufacturers all over the world as electrical equipment becomes more advanced and therefore sensitive to discrepancies in the supplied power.

When we think about the quality of incoming electrical power, it can be easy to think that all incoming power is the same and fits within a certain standard. This is true to a degree, but not all power is created equal, and there can be discrepancies in the quality, and usability of the power. 


incoming power quality can impact components and may cause electrical failure and downtime

Figure 1. The quality of incoming power can impact components and potentially lead to electrical failure and downtime. Image used courtesy of industrieblick


What is Power Quality?

Some equipment and systems are more robust, and the quality of incoming power has a less noticeable effect on operation. In other cases however, more sensitive equipment can be seriously affected by the quality of the power supplying it. If the quality of power is low enough, or sporadic, some equipment can even become unusable.  

Since it is known that incoming power exists with differing quality, it is useful to understand the types of power it affects as well as the different methods for measuring and understanding power quality. 

Power quality matters for most components in an automated system, including those supplied by internal power supplies. Power supplies within the factory are used to supply the necessary DC voltage where needed—transformers can also be used to change the higher voltage AC power into lower voltage AC power. 

This article will focus on the quality of power being delivered from the electrical power grid, as well as how to monitor and correct it. 


Effects of Bad Power Quality

As manufacturing and automation electronics continue to increase in complexity, so does the need for higher quality supplied power. Poor incoming power can lead to an inefficient use of electricity which translates to higher manufacturing costs. In some cases, that can also mean increased downtime from premature electrical component failure. 

The type of damage caused by power failures is often dependent on the specific way the power is distorted. Whenever harmonics add to each other, they can create a waveform that is damaging to equipment. In the case of increased voltage, some equipment may begin to operate in the saturation region leading to problems such as overheating and shortened lifespan.  

Low power quality can lead to equipment running inefficiently and an increase in the power supply cost associated with extra equipment needed to regulate the unreliable supply of power. In some cases, it can be necessary to oversize the power equipment in order to handle the extra stress imposed by inconsistent power leading to a higher equipment installation and maintenance cost. In cases where power is often interrupted, valuable data and unsaved information can be lost, creating larger problems downstream in the manufacturing process.  


Power Quality Monitoring and Correction   

Since power quality can have such a large impact on the cost, efficiency, and functionality of manufacturing equipment, it makes sense that manufacturers and integrators understand the quality of the incoming power. Understanding the ramifications in the beginning can help eliminate some factors in the event of equipment malfunctions. With the continuous improvement in electrical equipment and its growing dependance on higher quality power, the need for power monitoring, conditioning, and protection will continue to grow in importance. 

Eaton advanced power quality meter identifies incoming power quality issue

Figure 2. Power quality meters are used to identify if there is a quality issue with the incoming power supply. Image used courtesy of Eaton


Power Quality Monitoring

The first step to understanding whether or not power quality is an issue is to monitor the incoming power supply. There are several ways to monitor the incoming power supply, but they can be broken down into two categories: basic power quality meter or advanced power quality meter. 


Basic Power Quality Meter

A basic power quality meter simply monitors the incoming power into the plant. It is used to measure the amount of power consumed and is useful to manage costs associated with power consumption. It can also be assumed that sudden jumps in power consumption can be related to problems somewhere within the plant infrastructure—it will not, however, help with the process of finding the problem. 


Advanced Power Quality Meter

Advanced power meters are can do much more than monitor the incoming power, they are also capable of measuring different parameters of electrical power including:

  • Current

  • Voltage

  • Power Factors

  • Harmonics

  • Voltage Transients

Many different advanced power monitors are capable of alarming the plant when voltage spikes and other discrepancies occur. In addition to alarm systems, they are often capable of recording and saving waveforms and other information for an in-depth analysis after the incident occurs. 


Power Conditioning 

Once it is known that incoming power is causing problems within a plant, there are different methods available to manufacturers for solving power quality issues. A preemptive power study can be done by qualified engineers to understand the specific issues with the power supply and possible shortcomings in the current set up. This includes conducting arc flash tests, harmonic analysis, load flow tests, and stability studies, among others. These tests help manufacturers better prepare for weaknesses in their system should specific types of electrical irregularities occur.  


equipment, like uninterruptible power supplies (UPS) can regulate and mitigate low power quality issues

Figure 3. Different types of equipment can be used to regulate and mitigate issues with low power quality, such as an uninterruptible power supply. Image used courtesy of Traco Power


After a study is completed, there are specific pieces of equipment that can be put in place to help regulate and mitigate potential issues. The four main components used to condition equipment are:

  • Filters

  • Voltage regulators

  • Surge protectors

  • Uninterrupted power supplies   


Power Quality Filter

Filters are used to reduce harmonics created by non linear electrical loading. Filters are capable of blocking harmonics from entering the system or can bypass harmonics currents. They are often placed near the equipment creating non linear loads. 


Voltage Regulator

Voltage regulators are devices capable of creating a constant voltage for an output, regardless of the load on the system or the level of the voltage being provided to the system.


Surge Protector

Surge protectors are used to protect equipment from spikes in voltage by allowing only a certain voltage to accumulate before diverting excess current into the ground. 


Uninterruptible Power Supply (UPS)

Finally, a UPS is designed to provide constant power in the case of a power outage or interruption. These can be thought of as a backup for equipment to reduce the possible problems that arise as a result of unplanned plant downtime.  


Ensuring Quality Power

Incoming power can have a big impact on equipment running the automation industry. Low quality power can lead to a number of problems including increased downtime, shortened equipment lifespan, inefficient use of power, and lost data. These problems can become expensive if not properly addressed. 

In order to deal with low quality power, manufacturers will need to understand the specifics of the problem, usually through a power quality study. Once the problem has been identified, the right type of equipment can then be implemented to help mitigate the problem.