Do MCB trigger overload because of lightning strike?

MCB & Lightning Strike

Do MCB trigger overload because of lightning strike?  

Miniature Circuit Breakers (MCBs) are designed to protect electrical circuits from overloads and short circuits.

However, they are not specifically designed to protect against the effects of lightning strikes. Here's how MCBs and lightning strikes interact:

1. Overload Protection:

MCBs trip when the current flowing through them exceeds their rated capacity for a certain period. A lightning strike typically causes a very brief but extremely high surge of current, which is not the same as a sustained overload.

Therefore, an MCB might not trip due to a lightning strike because the duration of the surge is too short to trigger the overload mechanism.

2. Short Circuit Protection:

MCBs also trip in the event of a short circuit, which occurs when there is a sudden drop in resistance, causing a massive current flow. If a lightning strike causes a short circuit (e.g., by damaging insulation or creating an arc), the MCB will likely trip to protect the circuit.

3. Surge Protection:

Lightning strikes can induce high voltage surges in electrical wiring. While MCBs can handle some level of surge, they are not designed to protect against the extremely high voltages associated with direct or nearby lightning strikes. For this purpose, surge protection devices (SPDs) are recommended.

SPDs are specifically designed to divert excess voltage to the ground, protecting connected equipment and circuits.

In summary, while an MCB might trip if a lightning strike causes a short circuit, it is not designed to handle the high-energy surges typically associated with lightning.

For comprehensive protection against lightning strikes, additional surge protection devices should be installed in the electrical system.