When electrical equipment fails, it rarely happens out of the blue. Most failures begin quietly, hidden inside insulation systems as microscopic sparks known as Partial Discharge (PD). Left unchecked, PD slowly eats away at insulation until the day it flashes over, causing costly downtime and potential safety risks.
Studies show that up to 75% of disruptive failures in MV and HV assets are linked to PD activity. That makes early detection not just useful, but essential.
What Is Partial Discharge (PD)?
Put simply, PD is the inability of a small section of insulation to withstand the electric field around it. Imagine tiny sparks forming in voids, cracks, or along contaminated surfaces inside switchgear, transformers, or cables. They don’t short out the system immediately—but they weaken it, cycle after cycle, until it’s too late.
The key is that PD gives itself away. It produces electromagnetic pulses and ultrasonic sound waves—signals that can be captured with the right tools.
Partial discharges due to voids/cracks generating sparks inside a cable.
Why TEV & Ultrasound Testing Are Game Changers
Traditional PD testing required outages and invasive setups. Today, AMKA leverages TEV (Transient Earth Voltage) and Ultrasound testing, two complementary methods that detect PD while equipment stays online and in service.
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TEV Testing picks up high-frequency electromagnetic pulses caused by internal discharges hidden deep inside switchgear. These are often hard to detect as they occur inside the insulation.
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Ultrasound Testing detects high-frequency sounds from surface discharges, corona, and tracking, often heard as sizzling, crackling, or popping noises that reveal insulation problems on the surface.
TEV probe measuring internal discharges on switchgear; ultrasonic testing with headset and probe capturing sound waves from surface defect
Internal discharges are often difficult to detect directly, as they occur inside the insulation where early signs are not visible on the surface. By combining both, we can pinpoint insulation issues that would otherwise remain invisible—without disrupting your operations.
Real-World Proof
In one survey, engineers identified low-level void discharges inside a cable box using TEV detection. Left untreated, the defect could have escalated to a major fault. Because it was caught early, the client avoided an unplanned outage and replaced the affected termination at a fraction of the cost of failure.
In another case, ultrasonic testing revealed surface tracking on a cable termination. Visual inspection confirmed insulation deterioration that would have eventually led to failure. Thanks to early detection, the termination was replaced during scheduled maintenance rather than an emergency shutdown.
Cable termination with visible insulation damage, an early signs of PD activity.
These examples highlight a common truth—the majority of switchgear and cable failures originate from defects that PD testing can detect years in advance. By catching the “silent sparks” early, AMKA helps customers protect both uptime and safety.
Why Choose AMKA?
At AMKA, we don’t just measure. We analyze, trend, and advise. By integrating TEV and Ultrasound testing with other predictive tools like thermography, we provide a complete view of your asset health. Our approach is:
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Non-intrusive – equipment stays energized, minimizing downtime.
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Proactive – early warnings allow for planned interventions.
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Comprehensive – multiple diagnostic methods mean nothing slips through the cracks.
Our clients see us as more than testers—we’re their early-warning system against costly surprises.
The Bottom Line
Partial discharge is silent, but it doesn’t have to stay invisible. With TEV and Ultrasound testing, AMKA gives you the power to spot problems long before they turn into failures.
The best failures are the ones you never have. Talk to us today about how TEV & Ultrasound testing can safeguard your switchgear and keep your operations running smoothly.