Getting Started with Power Quality Surveys

Power issues are not abstract. They can cost money, degrade equipment performance, reduce reliability, lower productivity, and even pose safety hazards to personnel if left uncorrected.

A power quality (PQ) survey helps you see what’s on the wires to evaluate the compatibility of the power source with the loads. PQ surveys give you an organized approach to isolating the cause of power problems and verifying solutions. They can range from monitoring the electric utility service to facility-wide surveys or isolating loads or trouble areas. Reactive surveys are for troubleshooting and resolving problems. Proactive surveys are for benchmarking and understanding the present quality of supply versus the sensitivity of the loads.

PQ surveys can let you know if a problem is looming. Just because things appear to be working fine doesn't mean that you aren’t operating near or above tolerance limits for voltage, harmonics, etc.

When to conduct baseline surveys

It is a good practice to run a baseline PQ survey for a proactive health check of your power system or to document site power quality at the start of a project. Where to connect the meter(s) will be project dependent. For facility-wide projects, the best location may be at the electric utility service entrance, at or near the electric utility meter, or point of common coupling (PCC). Baseline surveys are also commonly done before designing in or commissioning sensitive loads or making major system changes.

If installing mitigation equipment such as UPS systems or harmonic filters, you should repeat the survey after installation to confirm performance and ensure the system is operating as expected.

Tools you’ll use

Basic PQ survey tools are a power quality monitor, circuit tester, multi-meter, and infrared scanner. Helpful add-ons include clamp meters, an insulation tester, and a ground resistance meter. Taking photos, videos, or quick audio notes can also aid in survey documentation.

The power quality monitor is your most important survey tool and is available as a portable or fixed unit. Portable PQ monitors are typically installed for the survey duration and removed upon completion. They are usually used reactively to solve problems. Permanent (or fixed) PQ instruments are typically installed proactively for the lifetime of the facility. Often, multiple permanent PQ monitors are installed at key points within a facility (e.g., at the PCC, UPS units, generators, and critical loads), creating a monitoring system.

You will want to ensure that whichever portable or fixed instrument you choose can capture the full spectrum of power quality problems — or at least the types of problems suspected. Otherwise, the survey results could be misleading or misreported, wasting time and money.

Applicable compliance standards

Modern PQ instruments should be Class A compliant with IEC 61000-4-30, Edition 3. This is an international standard for power quality measurement and specifies the instrument's measurement techniques to measure the quality of supply. IEC 61000-4-30 encapsulates other IEC standards, such as IEC 61000-4-7 for harmonics and 61000-4-15 for flicker.

In the United States, the IEEE has harmonized with some of the IEC standards. Voltage flicker measurement techniques in IEC 61000-4-15 are included in IEEE 1453. For harmonics, IEEE 519 (versions 2014 & 2022) adopted the harmonic measurement techniques of IEC 61000-4-7 and added new harmonic parameters and compliance limits for voltage and current harmonics.

When your instrument is IEC 61000-4-30 Edition 3 Class A compliant, it fully complies with the standard. In Europe and other parts of the world, using a Class A instrument is a “need to have” in many applications. In the U.S. and other areas, it’s also strongly recommended, but not a regulatory requirement. Regardless, an Edition 3 Class A instrument means it is from a reputable manufacturer, modern, and provides accurate and repeatable measurements.

PQ survey process overview

Whether your investigation involves a single piece of equipment or the facility’s entire electrical system, you’ll want to develop an understanding of the what, where, when, how, and why of the power-related problems before you start monitoring. The survey process typically includes these steps:

Describing the power problem. Review data logs and talk to equipment operators to learn the symptoms, when and where they appear, and what else may be occurring at the time, such as equipment startups. Document your findings.

Planning and preparing the survey. Based on your understanding of the power problem(s), decide initial monitoring points and duration, and the test equipment required. Set a safety plan and determine access needs.

Conducting a site inspection. Walk the site with facility operators to gain a better understanding of the electric utility service area and any equipment that might be causing problems. Sometimes a visual inspection may be all that’s needed to solve the problem.

Monitoring the power. Set up monitoring at the PCC if the concern is facility health or at the load for localized issues. Record both voltage and current based on your survey plan.

Collecting survey data. Use the power monitor’s scope mode to see real-time voltage and current magnitudes and wave shapes. Use its time interval setting to record parameter trends to see variations over time. Set instrument trigger limits to detect disturbances or other events affecting equipment.

Analyzing the data. Group events, align them with equipment logs, and determine likely causes such as sags, transients, distortion, grounding, or neutral issues. Compare system downtime or troubles with the PQ data recorded. If the PQ health is good — but the system is still experiencing problems — you may have to look elsewhere. For instance, is the equipment hardware or software the source of the problem, and not the power?

Applying corrective actions. Fix the basics first, such as wiring errors or damaged cords. Repair grounding and bonding. Then, mitigate as necessary by adding new wiring, UPS systems, transformers, or filters to resolve problems found in the survey. Document any changes made for future reference.

Verifying solutions. Re-measure with the same setup. Cover the same points, same thresholds, and same intervals so comparisons are apples to apples. Compare before and after to ensure your solution is working. Also, verify the solution hasn’t created other problems and the system is still operating as expected.

Key takeaways

• Power problems have real consequences. They can trip protection, upset controls, degrade product quality, and create safety risks.
  
  
• A PQ survey gives you a structured way to find the cause, prove the fix, and rule in or out power problems.
  
  
• Start with a baseline at the PCC, and repeat baselines after major changes or mitigation so future comparisons are valid.
  
  
• Use a small core kit and add tools as needed. Confirm that your monitor can capture the phenomena you suspect.
  
  
• Follow a simple process. Define the problem, plan and prepare, inspect the site, monitor at the right points, collect usable data, analyze with time correlation, apply fixes, and verify with the same setup.

Next in the series

In the next article, we’ll go deep on planning and preparing a power quality survey as well as include a short checklist you can use before you roll a cart on site.