By Matt Valenti, Application Engineer

In Part 1, we looked at how to find the source of harmonics without sending a crew. In Part 2, we identified how distributed energy resources (DER) and other surprise loads can drive harmonic distortions on your grid. In this last blog of our harmonics series, we look at a common misunderstanding. If your utility meets IEEE 519 standards, you’re in the clear, right? Not exactly.

Harmonics are often intermittent and tied to specific locations. IEEE 519 offers average-based limits, but utilities now need continuous asset-level visibility to catch harmful trends early. Many transformers degrade slowly due to harmonics that never technically break the rules.

What IEEE 519 Doesn’t Catch

• Uses 10-minute or 24-hour averages, not instant spikes
• Designed for system-wide not transformer-level views
• Misses brief but damaging harmonic events

Here’s the problem:

• A transformer could hit 100 percent iTHD for 5 minutes every hour and still pass
• These spikes heat and wear insulation
• Over time they lead to early failures

How Edge Zero Fills the Gap

EdgeSensor provides:

• Real-time iTHD and vTHD by phase
• Alerts for even short-lived spike events
• Event logs that track intermittent issues

This helps utilities:

• Catch early signs of transformer stress
• Improve analysis when failures happen
• Justify preventive maintenance or upgrades

Steps to Go Beyond Compliance

• Set your own internal thresholds tighter than IEEE 519 
• Monitor transformers not just substations
• Use long-term trends to find patterns

Key Points

Compliance is a good start, but not the finish line. For a stronger grid, you need:

• Real-time transformer-level data
• Alerts that catch short events
• Data that supports smarter maintenance

If you missed earlier parts of this series, go back and read Part 1 and Part 2 for a complete picture of the harmonic risks facing your grid.