Understanding power quality

Power quality problems can lead to equipment failure, high energy costs, business downtime and slow production. It is, therefore, important for businesses to understand and improve power quality to improve overall efficiency.

Put simply, power quality refers to how effectively your facility uses and distributes the power delivered to it. Power quality problems can usually be characterised in terms of the effect on the supply voltage. Typical symptoms include: flickering lights; transformer issues, such as noise, extra heat or premature failure; and unexpected equipment shutdown.

Why power quality matters

Power quality is an area of growing concern due to its associated financial impacts, downtime and damage to equipment. Not to mention, it’s becoming more common due to the digitisation and increasing use of electronic devices in industry facilities, ie, computers and digital machines.

In the industry sector, the cost of poor power quality can reach 4% of annual turnover and is often equivalent to the total balance payable on a facility’s energy bill. The more worrying statistic, however, is the EPRI finding that 80% of power quality disturbances are generated within a facility. That means a business’s approach to power will often hurt its bottom line. For example, if power is being inefficiently handled within a plant, it’s likely you’ll be paying more for the electricity that you’re using.

Power quality issues also put greater strain on your equipment, which not only means downtime and repair costs, but can be an issue for staff safety as staff are operating equipment that is not performing adequately. The life span of equipment is also impacted by poor power quality, meaning, again, more costs associated with maintenance and the replacement of depreciating assets.

Given the pressure that rising electricity prices are putting on businesses, plus initiatives surrounding the rollout of more cost-reflective tariffs, it’s not surprising more businesses want to tackle poor power quality. The challenge lies in understanding how to identify the problems.

Measuring to manage

It’s a classic business adage that you can’t manage what you can’t measure, and that principle certainly holds true for power quality.

The reason many businesses don’t measure is because they don’t know what they should be tracking, nor how they should go about the process. While every location is different — and has its unique profile of installed loads and grid-supplied power issues — research studies from Europe and the US help highlight what should be monitored.

In the US, for instance, research studies show that voltage sags and swells and harmonics are, by far, the most common issues facing facilities. Over in Europe, businesses are hit hard by transients and surges, voltage dips and short interruptions. In Australia, we have found that the following power quality issues are of growing concern: harmonics; poor power factor; voltage sags; transients.

How to measure

When planning an approach to measurement there are two options: a short-term, ‘quick fix’ like approach; or a long-term approach which is more aligned with the overall facility or company goals. The short-term approach might, for example, involve measuring known problem areas within a facility over a two-week period. Although doing this is better than doing no measurement at all, this method won’t support ongoing continuous-improvement goals of the facility. That’s because the analysis will likely only provide a small glimpse into what’s happening — rather than the complete picture.

While a short-term approach will be effective, based on our experience conducting hundreds of power-quality audits, it is recommended companies install a permanent power quality monitoring system to detect and record all disturbances on an ongoing basis. With continuous monitoring comes the possibility of making continuous improvements to your system’s power quality and sustainability.

Where to manage

To perform power quality measurements, a system should be equipped with power quality metering devices. These devices should be able to capture and record short-term power quality events; and provide current and voltage information, continuous disturbance measurements and power quality compliance evaluations.

Power quality meters usually have a higher cost than power meters with basic functionality, thus it is important to place them in the right places within your electrical installation, or on sensitive loads.  For example, placing a power quality meter on the main incomers allows monitoring of the power supply quality, detection of any background distortion coming from the energy provider and compliance with utility standards. Also, a key for continuous improvement of power quality and power system health is to collect and connect the information of all available sources into a single system, and provide tools that evaluate, analyse, report and alarm on power quality issues.

Analysis includes the interpretation of recorded data and the evaluation of power quality’s impact on the electrical installation and equipment. The analysis can be performed on a regular basis (for example, once per month) or ad hoc (when there is a problem caused by a potential power quality disturbance).

Analysis is usually performed by skilled and experienced professionals, with specific competencies in power quality, electric installation and equipment, who are capable of correlating power quality disturbances with equipment damage, malfunction or electrical installation downtime.

Because electrical and maintenance personnel in a facility may not be power quality experts, the current trend is to embed increasing analysis and expertise capabilities into power quality monitoring systems. Such systems can provide meaningful dashboards and appropriate widgets to analyse power quality problems. For example, a trend graph should be used to analyse steady state power quality disturbances (harmonics, unbalance, power factor etc) where exceeding recommended limits on a regular basis can lead to issues such as equipment overheating or failure and network overload.

Equipment to solve power quality problems

Once you have a clear understanding of power quality challenges, it’s time to take action. Manufacturers have developed a range of equipment to help consulting engineers and facility personnel. In some cases, the options are clear, while other situations may require a bit more thought.

• Transients. Transient voltage surge suppressors are the best option for protecting against transients in a power system.
• Voltage sags and interruptions. The best choice here depends on extent of any interruption. Uninterruptible power supplies and other energy-storage options could do well with shorter-term interruptions, but back-up generators or self-generation equipment is needed when longer outages are encountered. Other solutions could include static transfer switches and dynamic voltage restorers with energy storage.
• Harmonics. Active filters are the recommended solution for harmonic mitigation, thanks to their flexibility and dynamic mitigation performance. Alternative approaches could involve passive filters, multipulse arrangement transformers or harmonic correction at the equipment level (for example, by integrating harmonic filtering into variable speed drives).
• Power factor. Reducing power factor requires producing reactive energy as close as possible to connected loads. Installing capacitors on the network is the easiest and most common way to achieve this goal.

Taking power quality to the next level

By implementing a more proactive process of continuous power-quality improvement, facility managers can minimise the risk of future problems and interruptions and maximise both operational efficiency and equipment lifespan. The following short- and long-term steps can help facility managers improve their uptime, energy efficiency and asset management:

Within the next few weeks: Plan a project roadmap. As a starting point consider monitoring the power quality at plant level or at critical areas with sensitive loads.

Within the next 6 months: Analyse the results of your monitoring and its impact on your equipment and installation. Assess the power quality correction technologies. Identify an initial project with reasonable investment that can result in positive results over a relatively short period of time (for example, an immediate opportunity to deploy power quality equipment for a particular device or process).

Within the next 12 months: Plan methods for expanding power quality solutions more broadly throughout your organisation. Collaborate with internal stakeholders and/or seek out expert service organisations that have the technical expertise and global presence to support a long-term infrastructure integration project.

Tackling power quality

Poor power quality is a huge cost to businesses of all sizes — directly in terms of the energy prices businesses pay and indirectly in terms of the cost of replacing and repairing inefficient machinery or in terms of loss of production. Although the symptoms of poor power quality can be relatively easy to spot, understanding what exactly is causing the power quality issue is more complex. That’s why continuous monitoring is so important.  If you’re not monitoring what’s happening within your facility then your business could be leaking cash without you knowing.

Although a variety of solutions to manage power quality challenges exist, a lack of knowledge in how to address critical aspects of power quality performance is holding businesses back. As electricity prices continue to rise, it is critical facility managers take action now to protect the bottom line for the long term. The right kind of corrective action can create an almost immediate financial benefit in the form of electricity bill savings.

Case study

SULO Australia identifies 15% in energy usage savings and tackles power quality

SULO Australia, an Australian manufacturer and supplier of plastic and metal bin products, operates a highly automated, large-tonnage injection moulding plant in the country.

The company made the decision to undertake an energy audit. The audit was subsidised by the New South Wales Office of Environment and Heritage and was conducted by Schneider Electric to identify where and how energy was being used across the MGB manufacturing plant.

After a 15-week in-depth audit, a number of key findings were reported back to the SULO team, highlighting where energy was being used across the plant. Interestingly, across the facility just four machines were consuming 80% of the site’s power. On completion of the audit, there were 16 energy-saving opportunities presented back to SULO.

These 16 opportunities had the potential of reducing annual electricity costs by 15% across the entire plant, equating to over $200,000 per annum.

Improving power quality has now become more important than ever and therefore SULO installed and commissioned two Schneider Electric power factor correction units. These units have improved the power factor from 0.80 to 0.96 and will result in ongoing energy cost savings.