The secret behind the malfunction of medium and high voltage fuses

2025-07-23 13:23:54

At 2 o'clock in the morning, the high-voltage room of a chemical plant suddenly exploded - the fuse of the 10kV capacitor cabinet exploded, causing a power outage throughout the plant! On duty electrician Lao Li used a flashlight to check and found spiral burn marks on the surface of the melting tube. He immediately concluded, "This is not a short circuit! Someone has tampered with the secondary wire

1、 Take a glance at the circuit breaker trace and instantly understand the root cause of the fault

Diagnosis Three Axes:

1. Melt central fracture → overload fault (load overload)

Real case: The central fuse of a rolling mill in a steel plant was blown, and it was found that the cooling fan of the frequency converter stopped running, causing overcurrent

2. Explosion at both ends of the melting tube → Short circuit high current (insufficient breaking capacity)

Lesson: The fuse at both ends of the Shandong wind farm shattered, which actually caused a 28kA short circuit due to cable head breakdown

3. The inner wall is blackened without damage → aging failure (running for more than 10 years without replacement)

Data: According to State Grid statistics, 63% of hidden faults are caused by overdue service

2、 The most dangerous hidden killer: poor contact (ignored by 90% of electricians)

On site diagnostic tips:

l  Infrared thermal imager scanning Terminal: Stop immediately if the temperature difference exceeds 15 ℃

l Night light off inspection: red contact points indicate current exceeding 70%

l Measuring voltage drop with a multimeter: If the voltage difference between the two ends is greater than 5% of the rated voltage, it is abnormal

Lesson learned:

In 2023, a cement plant experienced a circuit breaker without any reason, and it was eventually discovered that:

-Oxidation of C-phase connection pile head (Figure 4 corrosion close-up)

-Contact resistance reaches 3.8m Ω (standard should be<0.5m Ω)

-Long term overheating leads to deterioration of melt characteristics

3、 Four step method for emergency maintenance and life preservation (to avoid secondary accidents)

Steps:

1. After checking the electricity, touch the cabinet first: if there is vibration → there is electromagnetic resonance (danger!)

2. Insulation test before removing the fuse: Do not operate when the phase to phase resistance is less than 100M Ω

3. Replacing the necessary conductive paste: Master Zhang's unique technique (reducing 80% of contact failures)

4. Key actions for test power transmission: side closing+protective face mask (to prevent arc splashing)

>Practical record: After Wuhan Power Supply Bureau adopted this method, the maintenance injury rate decreased by 92%

4、 Intelligent preventive maintenance plan (saving 60% of repair costs)

Low cost monitoring combination:

Annual Key Inspection:

Perform a DC resistance test (if the resistance changes by more than 10%, it will be scrapped)

Check the pressure release indicator (it must be replaced if it pops up)

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