The Real Causes and Troubleshooting Techniques for Low-Voltage Pole-Mounted Circuit Breakers Tripping During Severe Thunderstorms

With the frequent arrival of summer thunderstorms, many outdoor power distribution facilities face severe challenges. Equipment at the end of overhead lines, in particular, often suddenly stops working after thunderstorms. Often, when people find that their homes have no power, it's actually because the Lv Pole Mounted Circuit Breakers device on the utility pole has malfunctioned or been physically damaged due to an induced lightning strike.

How does lightning break down a low-voltage pole-mounted circuit breaker?

Lightning doesn't necessarily have to strike a utility pole directly to cause problems. When a thundercloud discharges to the ground, nearby conductors generate a huge induced overvoltage. This instantaneous high voltage directly impacts the internal contacts and electronic trip unit of the low-voltage pole-mounted circuit breaker along the line. If protective measures are inadequate, the powerful current can instantly burn out the arc chamber, or even cause the casing to explode. This type of fault is very common in power networks in mountainous or open areas.

On-site Inspection and Fault Diagnosis Procedure

Upon arrival at the site, the first step for maintenance personnel is usually to observe the exterior.

• Exterior Damage: Observe whether the operating handle of the low-voltage pole-mounted circuit breaker is in the free-trip position and whether there are carbonized black spots on the casing.

• Insulation Resistance Measurement: Use a megohmmeter to test the phase-to-phase insulation. Equipment struck by lightning often suffers from internal short circuits.

• Scorch marks: Open the terminal cover and check for metal melting caused by high-voltage creepage.

Why does excessive grounding resistance worsen the fault?

If the grounding down conductor is rusted or the grounding electrode resistance is substandard, the lightning current cannot quickly dissipate into the ground. In this case, the low-voltage pole-mounted circuit breaker becomes the unfortunate victim of current discharge. The pressure that should be borne by the surge arrester falls entirely on the circuit breaker's insulation layer. Maintaining an unobstructed grounding path is crucial to reducing this type of hardware damage.