Integrating PD Detection in High Voltage Gear After Fire Exposure

Dealing with a fire scene is tricky business. A methodical approach is necessary to ensure all evidence points to a cause or underlying risk. That way, a business or industrial setting can continue to operate without the danger of similar future fire incidents. High-voltage systems are particularly at risk due to the presence of heat, soot, chemicals, corrosion, and moisture.

Over time, many industrial settings begin to degrade. Materials get run down, wear and tear play a role, and insulation starts to crack. These create the perfect setting for partial discharge (PD), which can lead to a fire. Inspecting these situations post-fire requires specialized equipment and extensive experience in forensic engineering. Here are some of the insights we’ve gained from our work at Dreiym Engineering.

What Is Partial Discharge and Why Does It Matter?

Partial discharge occurs when insulation around high-voltage electrical equipment begins to degrade or break down. Instead of a complete arc or short circuit, PD tends to be a bit sneakier. It works in the background, silently impacting the insulation materials used on standard gear like cables, transformers, and bushings.

You find PD in voids, cracks, delaminated surfaces, or interfaces with contaminated materials. Once electrical loads are applied to such weak points, micro-arcs are created, along with acoustic energy, light, ozone, localized heating, or electromagnetic radiation. Those emissions are precisely what we look for using professional and carefully calibrated equipment.

It’s suggested that 85% of high voltage insulation failures are caused by PD activity. That is why IEEE Std. 930 exists. It is a crucial predictor that you are in danger of electrical failures and potential fire damage.

Fire’s Role in Accelerating PD Risk

If PD degrades insulating materials over time, fire takes that period and accelerates the heck out of it. Even a brief moment of material exposure to flame or high heat can weaken its reliability and underlying structure (especially if organic or polymer-based). In a post-fire situation, you are looking for PD due to:

• Thermal degradation breaks down the insulation materials, reducing their dielectric strength.
• Moisture absorption due to fire extinguishers and suppressors using water or foam.
• Smoke or soot deposits can act as semi-conductive barriers, increasing the risk of a spark.
• Mechanical stress occurs when materials are rapidly cooled or heated, and develop cracks and delamination.

When the degraded insulation cannot maintain the original voltage load safety, PD begins. This often occurs after a post-fire system is re-energized. Something like the insulation paper in a transformer, rated for continuous operation at 105 degrees Celsius, will lose half its protection in over 15 minutes to higher temperatures.

Methods of PD Detection After Fire Exposure

The question then becomes, how does a team like ours at Dreiym Engineering detect and indicate where PD activity is occurring after a fire? Our role is to rely on scientific instruments, years of experience, and data-driven insights. That may include:

• Ultrasound Detection: Utilize AE sensors to detect surface tracking discharges that emit high-frequency sound waves (acoustic emission sensors).
• Ultra-High Frequency (UHF) Sensing: Detecting the electromagnetic pulses created by internal PD activity, especially if you’re using enclosed or GIS components.
• Infrared Thermography: IR scanning isn’t a direct PD detection method, but it helps identify localized heat buildup from energy loss, which is likely to cause greater degradation of insulation materials.
• Oscillographic Time-Domain Reflectometry (OTDR): We use OTDR to locate insulation breakdowns in power cables. This is done by sending pulses and then analyzing the corresponding reflected waveforms received.

We can use these tools in both an online and offline setting (energized or powered down). That way, we have investigative techniques available that fit the safety risk to our team and people “on the ground” after the fire occurred.

Real-World Scenario: Data Center

It helps to examine partial discharge detection through the lens of a real-world scenario. Let’s say you’re running a massive data center somewhere in the Midwest. A fire occurred a couple of weeks ago in a nearby printer room due to an employee sneaking a cigarette near the trash bin. While the flames were dealt with quickly enough to restrict the fire to that room, the smoke damage got into your server space.

During a standard visual inspection by your risk management team, only superficial damage was detected. A few walls with scorched paint and some melted labels or floors that need professional cleaning were all that was required. However, you have an IT director who hired a forensic engineering team like ours, just to be sure.

Using a blend of our tools and experience, that team conducted offline PD testing and discovered active discharge within the switchgear’s busbar insulation. Those tiny little voids formed from high-heat smoke damage is all it takes for partial arcs that are likely to lead to even more damage in the next couple of weeks.

Now, your data center has more information to act on. You can replace any compromised sections of equipment, writing off the fractional cost of PD detection instead of incurring significant financial expenses due to a secondary fire that occurs so close to the primary incident.

Preventing Future PD Risks in High Voltage Systems

Partial discharge detection is necessary before a situation gets out of hand. It is the post-fire seal of approval you need for peace of mind. There are some other steps a business or industrial site can take to further reduce PD risk outside of a forensic team coming to visit, though that shouldn’t be replaced:

• Take baseline PD measurements around high-voltage assets during regular operation. That will establish a before image of baseline operations.
• Schedule electrical audits around your outdated, aging, or moisture-exposed insulation so you have a better idea of what to prepare for in the future.
• Install surge protection, especially if you’re considering commercial electrical design, to ensure your insulation systems have backup protection.
• Having your risk managers purchase thermal and ultrasonic equipment to monitor anomalies in real time.

That last suggestion is good, but may be better applied by a team of experts, such as our electrical engineers and forensic specialists at Dreiym Engineering. We spend decades working with private residences, commercial properties, and industrial settings all over Texas, Oklahoma, Louisiana, New Mexico, and Colorado. We possess the necessary licensing, legal expertise, and equipment to detect PD before it escalates.

Our extensive reporting will provide you with the necessary insight so you can adjust infrastructure upgrades or post-fire repairs accordingly. Working with high-voltage systems is risky enough. Save yourself the hassle of a silent PD issue creeping up when you’re trying to recover from an earlier incident.

Don’t Let Hidden Discharge Spark the Next Fire

Even after the flames are out and you’ve taken steps to clean and repair the affected area, risk hasn’t completely run out. Partial discharge can be inside the components of your high-voltage equipment, making an invisible threat that degrades your system further.

Calling on a forensic engineering team like ours at Dreiym Engineering provides peace of mind. It ensures your insurance provider is happy and gives your risk management team a solid heads up of what to repair, plans for improving systems in the future, and what to monitor right now. Schedule a consultation today, and let’s ensure your systems are safe and operating efficiently.