When Equipment Fails Without Warning

Troubleshooting electrical systems often demands more than technical skill—it requires the mindset of an investigator. Issues don’t always announce themselves clearly. Instead, they hide behind symptoms that point in several directions at once: equipment that fails without cause, circuits that seem fine during inspection, or downtime that reappears despite repairs.

When these situations arise, an electrician must combine experience, systematic testing, and the right diagnostic tools to uncover the truth. In this article, we’ll follow one such investigation into a well-maintained manufacturing plant and draw out the lessons every electrical contractor can apply when facing elusive electrical problems.

The persistent failure

A contractor has been called in to investigate a large 3-phase motor that has failed multiple times over a three-year span. Each failure had cost the facility significant downtime. Standard steps had already been taken: the motor was replaced, the wiring was inspected, and protective devices verified. Each time, the system looked correct on paper. Yet, the failures kept returning.

For the contractor, the situation was a classic riddle. If the equipment and installation were sound, what else could be lurking beneath the surface?

The investigation process

The contractor begins where most failures start — closest to the equipment. Connections are examined, torque verified, insulation resistance tested. No defects are found. Next, attention turns upstream. Breakers, bus connections, and feeders are all checked. Voltage readings appear normal under load. Power factor and harmonics are evaluated, but nothing out of the ordinary emerges.

At this point, the process turns from routine troubleshooting to detective work. If nothing in the visible system explains the repeated failures, perhaps the problem lies in what can’t be seen with standard meters.

The unseen enemy: electrical transients

That’s when the contractor considers electrical transients. These short-duration surges of voltage or current last only microseconds to milliseconds. They can originate from inside the facility (such as motor switching, faulty breaker contacts, or variable-speed drives) or from outside (utility grid switching, capacitor bank operations, or lightning strikes).

Though invisible to the eye and too fast for most instruments to capture, their impact is real. Sensitive equipment such as PLCs, sensors, and industrial drives can degrade with repeated exposure. Over time, this leads to:

• Premature component failure
• Corrupted data and communication errors
• Costly unplanned downtime
• Higher maintenance expenses

The contractor realizes that specialized monitoring is needed to confirm or rule out transients.

Tools that reveal the invisible

Unlike standard digital multimeters or clamp meters, identifying transients requires high-speed power quality analyzers capable of logging and capturing events at very fine resolutions. These tools allow electricians to:

• Capture transient waveforms with sub-millisecond accuracy
• Measure magnitude, duration, and frequency of each event
• Correlate disturbances to equipment operation (e.g., motor startup, switching)
• Distinguish internal vs. external sources by testing at different points in the system

The contractor sets up the analyzer first at the motor connection, then progressively upstream toward the service entrance. This step-by-step approach systematically narrows in on the root cause of the transient activity, ultimately allowing for the next step to occur: solutioning toward prevention.

Building the case for mitigation

After several days of monitoring, the contractor has enough data to start piecing together the story. Each captured transient has its own fingerprint — magnitude, duration, timing, and waveform shape. Interpreting these clues points to different sources and, ultimately, different corrective measures.

When the source is internal switching equipment

The contractor notices sharp spikes each time a large motor starts. These impulsive events are traced back to load switching inside the facility.

Solution: Install transient voltage surge suppressors (TVSSs) at the affected panels and sensitive equipment. These devices act as the first line of defense, clamping the voltage before it can damage controls or drives.

When the pattern shows oscillatory disturbances

At another point in the system, the data reveals fast, back-and-forth waveforms each time capacitor banks engage. The oscillatory nature of the disturbance suggests resonance within the system.

Solution: Apply line filters or isolation transformers to smooth out the fluctuations and keep them from propagating downstream.

When grounding is the weak link

In reviewing the facility’s bonding system, the contractor finds inconsistent connections that create high-impedance paths. The captured transient events appear amplified compared to their likely source, confirming poor grounding as a contributing factor.

Solution: Improve grounding and bonding practices, ensuring a low impedance return path that reduces both the frequency and severity of transient events.

When the trail leads outside the plant

Finally, some events show up across multiple points simultaneously, with no clear internal trigger. Their timing matches with known utility switching operations in the area.

Solution: Coordinate with the utility provider for a broader power quality review. External sources require collaboration beyond the facility walls to implement utility-side solutions.

By walking through each scenario and applying the right mitigation strategy, the contractor not only resolves the motor failures but also helps the facility strengthen its entire power quality program.

Lessons learned

Electrical transients are among the most elusive of power quality problems. They don’t appear in normal testing, yet their consequences can be devastating. For contractors, the key lessons from this case are:

• Don’t stop at the obvious. If equipment continues to fail despite replacements, broaden the investigation.
• Use the right tools. Only high-speed analyzers can capture transient events.
• Think systematically. Start at the point of failure and work upstream to localize the source.
• Apply targeted solutions. Mitigation depends on the transient type and origin.

The takeaway

Electrical troubleshooting is as much about persistence and process as it is about technical skill. By approaching unexplained failures with an investigative mindset — and by leveraging advanced diagnostic tools — contractors can uncover hidden threats like transients before they cause long-term damage.

Reliability begins with visibility and sometimes, seeing what happens in less than a millisecond makes all the difference.